776
Research report
Effects of psychostimulants on social interaction in adult male rats Romana Šlamberováa, Anna Mikuleckáb, Eva Macúchováa, Ivana Hrebíčkováa, Mária Ševčíkováa, Kateryna Nohejlováa and Marie Pometlováa Psychostimulants are known to have a huge impact on different forms of social behaviour. The aim of the present study was to compare the effects of three different psychostimulants [amphetamine, cocaine and 3,4 methylenedimethoxyamphetamine (MDMA)] on social interaction (SI) in adult male rats. The SI test was performed in a familiar arena and under low-stress environmental conditions. Experimental animals received amphetamine (0.5, 1.0, 1.5 mg/kg), cocaine (0.5, 1.0, 1.5, 2.5, 5.0, 10.0 mg/kg) or MDMA (2.5, 5.0, 10 mg/kg) and control animals received saline (1 ml/kg) 45 min before the SI test. Time spent in SI (individual patterns of social behaviour) and nonsocial activities (locomotion and rearing) were video recorded and then analysed offline, with the following results: (a) all doses of amphetamine decreased SI. Specifically, all doses of amphetamine decreased mutual sniffing, and the higher doses also decreased allo-grooming and following behaviours. (b) The higher doses of cocaine decreased SI, especially mutual sniffing, allo-grooming and climbing over. Cocaine at the dose of 5.0 mg/kg increased genital investigation compared with lower doses. (c) All doses of MDMA decreased mutual sniffing and climbing over; the two
Introduction Psychostimulants have been shown to have considerable effects on a great variety of behaviours in both humans (Sommers et al., 2006) and laboratory animals. Chronic exposure to psychostimulant drugs in extreme cases may result in aggressive psychosis and paranoia (McGregor et al., 2008). Individuals with substance use disorders often show severely impaired social interaction (SI), preferring drugs of abuse instead of social contact (Zernig et al., 2013). Long-lasting alterations in emotional state, such as fear, anxiety, social receptivity and depressive symptoms, as well as memory deficits have been observed in the laboratory rats administered psychostimulants (Williams et al., 2003; McGregor et al., 2003b; Navarro et al., 2004; Hayase et al., 2005; Páleníček et al., 2005; Thompson et al., 2008; Schutová et al., 2009), which match the long-term changes reported in human studies (Clemens et al., 2007). Some animal studies examining the effects of acute psychostimulant administration have reported an anxiolytic-like action of these drugs in various animal models, even though there is also substantial evidence supporting an anxiogenic-like effect (Paine et al., 2002; Navarro et al., 2004). 0955-8810 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
higher doses decreased allo-grooming behaviour, and only the highest dose decreased following. The two higher doses of amphetamine and all the doses of MDMA increased locomotion and rearing; cocaine did not affect locomotion, but increased rearing at higher doses. In conclusion, the results confirm the well-known finding that psychostimulants suppress SI, but also show novel differences in the effects of psychostimulants on specific patterns of SI. Behavioural Pharmacology 26:776–785 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. Behavioural Pharmacology 2015, 26:776–785 Keywords: amphetamine, cocaine, male rats, 3,4 methylenedimethoxyamphetamine, psychostimulants, social behavior a Department of Normal, Pathological and Clinical Physiology, Third Faculty of Medicine, Charles University in Prague and bDepartment of Developmental Epileptology, Academy of Sciences of the Czech Republic, Institute of Physiology, Prague, Czech Republic
Correspondence to Romana Šlamberová, MD, PhD, Department of Normal, Pathological and Clinical Physiology, Third Faculty of Medicine, Charles University in Prague, Ke Karlovu 4, 120 00 Prague 2, Czech Republic E-mail: [email protected] Received 14 November 2014 Accepted as revised 30 April 2015
Psychostimulants, especially 3,4 methylenedimethoxyamphetamine (MDMA), are usually considered socializing drugs because they are often used to increase activity in dancing clubs and parties. Animal models of this drug abuse, however, show that the opposite seems to be true. Many studies (Miczek and Tidey, 1989; Ando et al., 2006; Trezza et al., 2014), including our own (Šlamberová et al., 2010, 2011), repeatedly show that psychostimulants decrease social behaviour in rats. For example acute treatment with MDMA inhibits social play behaviour (Homberg et al., 2007) and decreases social investigation at high doses (Navarro and Maldonado, 1999; Maldonado and Navarro, 2001; Daza-Losada et al., 2009). Nevertheless, there are also studies supporting the assumption of a prosocial effect of MDMA (Morley and McGregor, 2000; Thompson et al., 2007). It seems that the prosocial or antisocial effect of psychostimulants depends on the dose as well as on the animal model used (McGregor et al., 2008). Supporting the relevance of animal studies, a relationship has been reported between the effect of psychostimulants on social behaviour and the oxytocin levels in the rat hypothalamus (McGregor et al., 2008); oxytocin levels are also increased in humans who abuse MDMA at dancing parties (Wolff et al., 2006). DOI: 10.1097/FBP.0000000000000148
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
Social interaction and psychostimulants Šlamberová et al. 777
Social behaviour represents an integral part of the behavioural repertoire of rats that is essential for emotional wellbeing, healthy development, establishment and maintenance of adequate social structures and reproductive success (Trezza et al., 2011). There are different forms of SI that occur in different phases of an animal’s lifespan: affiliative behaviour, social play and sexual interaction have a high reward value (Trezza et al., 2011). A number of studies have reported that social behaviour is particularly sensitive to pharmacological influences (File and Seth, 2003; Varlinskaya and Spear, 2008; Mikulecká et al., 2014). In rodent and primate studies, psychostimulant drugs, such as amphetamine, cocaine and MDMA, have been shown to interfere with various social behaviours (Miczek and Tidey, 1989; Ando et al., 2006; Trezza et al., 2014). For example, amphetamines, more than any other psychostimulant drugs, elicit aggressive behaviour (Ellinwood et al., 1972; Miczek and Tidey, 1989). Methamphetamine (MA) and MDMA have been shown to decrease social behaviour, an effect that is associated with an anxiogenic effect and dopamine depletion (McGregor et al., 2003b; Clemens et al., 2004). In addition, another psychostimulant drug, cocaine, induces systemic effects that are similar to those of amphetamines (such as an increase of blood pressure, heart rate, feelings of ‘pleasantness’ and ‘stimulation’, and decreased feeling of hunger), but the duration of their action is much shorter (Resnick and Resnick, 1984). Acute cocaine administration suppresses affiliative behaviour and enhances defensive behaviour (Rademacher et al., 2002). In adolescent animals, social play had been shown to be suppressed by psychostimulants, such as amphetamine and cocaine (Holly et al., 2012; Achterberg et al., 2014; Baarendse et al., 2014). Our previous studies have shown that acute MA administration reduces SI in a dose-specific, stress-specific and hormone-specific manner (Šlamberová et al., 2010, 2011). Specifically, all doses of MA (0.5, 1.0 and 1.5 mg/kg) dosedependently decreased SI (Šlamberová et al., 2010). Further, the environmental conditions, such as familiarity with the experimental arena and intensity of light, influence both social and nonsocial activities (Šlamberová et al., 2010). While SI is decreased, locomotion and exploratory rearing are increased in an unfamiliar arena, suggesting a higher interest in the exploration of the unknown environment with lesser interest in the conspecific (Šlamberová et al., 2010). Thus, psychostimulant drugs, such as amphetamines and cocaine, markedly suppress social behaviour. However, the neural mechanisms underlying these effects remain to be elucidated (Achterberg et al., 2014). All the psychostimulants are known to activate monoamine systems in the brain – with differing preferences for noradrenalin, dopamine or serotonin (5-HT) (Iversen et al., 2014). Amphetamine affects mostly the noradrenergic, less the dopaminergic and minimally the serotoninergic systems. Cocaine mostly affects the dopaminergic and serotoninergic systems,
whereas MDMA predominantly affects the serotoninergic system (Rothman and Baumann, 2006; Iversen et al., 2014). A recent study showed that the suppressive effect of amphetamines on social behaviour might be mediated through α-2-noradrenergic receptors, whereas that of cocaine is because of simultaneous increases in dopamine, noradrenalin and serotonin neurotransmission (Achterberg et al., 2014). Repeated exposure of young rats to MDMA caused serotonin depletion and induced anxiety-like behaviour in the social interaction test (SIT) accompanied by a long-lasting reduction in specific 5-HT(2A)receptor-mediated behaviour (Bull et al., 2004). Another study indicated that MDMA could have a prosocial effect involving 5-HT 1A and 5-HT 2B/2C receptors, and in contrast, also an anxiogenic effect measured in the emergence test involving 5-HT 1A, 1B, 2A, 2B and 2C receptors (Morley et al., 2005). Although many studies have been published from the early 1970s (Tikal and Benešová, 1972; Syme and Syme, 1974; Kršiak, 1975) to date (Miczek et al., 2013; Achterberg et al., 2014; Trezza et al., 2014) showing the effects of various types of psychostimulants on different forms of social behaviour in rodents, the results of the studies are inconsistent. They involved different methodological procedures, different strains and animals of different ages. The objective of the present study was to compare the effects of three psychostimulant drugs (amphetamine, MDMA and cocaine) on social behaviour under identical conditions to integrate knowledge of the effects of psychostimulants on SI. As in our previous studies (Šlamberová et al., 2010, 2011), we used the method of File and Hyde (1978), which was validated for pharmacological studies. In addition to evaluating social behaviour in general, we also focused on specific patterns of the SI repertoire as well as the nonsocial behaviours locomotion and exploratory rearing.
Methods Subjects
In total, 246 adult male albino Wistar rats (8–10 pairs per group) were delivered by Anlab (Prague, the Czech Republic) from Charles River Laboratories International Inc. Animals were housed four per cage and left undisturbed for a week in a temperature-controlled (22–24°C) colony room with free access to food and water on a 12 h (light): 12 h (dark) cycle, with lights on at 06:00 h. Social interaction test
Animals were first habituated individually in an open field (45 × 45 × 30 cm) on 2 consecutive days in a dimly lit room for 10 min (File and Hyde, 1978). On the third day, a pair of unfamiliar animals of the same weight and treatment (each from a different cage) was tested for SI. The experiment was conducted under the same conditions as the habituation test. Drug (see below) or saline was injected subcutaneously 45 min before the SIT.
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
778 Behavioural Pharmacology 2015, Vol 26 No 8
The behaviour of each pair of animals was video recorded for 5 min. Subsequently, recordings were evaluated offline using ODLog software (Macropod Software). The frequency (number of occurrences) and the duration (time spent) in SI and nonsocial behaviours were evaluated. The measures analysed were as follows: (a) SI, which included the following patterns: sniffing (mutual), genital investigation (sniffing the anogenital area), following (the pursuit of one animal by another), climbing over and crawling under the partner, and allo-grooming; (b) nonsocial behaviours: locomotion (several steps in a forward direction) interrupted by other behavioural patterns, and rearing, expressed as vertical activity, irrespective of whether it occurred on or off the walls. Behaviour was recorded by typing pre-set keys on a computer keyboard. The ODLog software registered the number of presses and the time in seconds between presses. First, the number and the time spent in various social behaviours shown by each pair of rats were calculated. Then, the nonsocial behaviours were scored separately for each rat in a pair and summed to calculate the locomotion and exploration (rearing) for each pair. The experimenter trained himself until he could repeatedly score with at least 85% consistency between two analyses on the same pair of rats.
Particular patterns of social interaction
Drug treatment
Fig. 1
The effects of each drug (amphetamine, cocaine, MDMA) were analysed separately. Total SI was analysed first, followed by the particular patterns of social and nonsocial behaviours. One-way analysis of variance (drug treatment) with the Bonferroni post-hoc test was used to test the duration and number of each type of social and nonsocial behaviours. Differences were considered significant if P value was less than 0.05.
Results Amphetamine Total social interaction
As shown in Fig. 1, amphetamine decreased SI in a dosedependent manner [F(3, 28) = 27.86; P < 0.001]. All doses decreased SI relative to saline-treated rats, and the 1.0 and 1.5 mg/kg doses decreased SI relative to the 0.5 mg/ kg dose.
Allo-grooming: The duration [F(3, 28) = 9.61; P < 0.001] and the frequency [F(3, 28) = 15.34; P < 0.001] of allogrooming were decreased after the two higher doses of amphetamine (1.0 and 1.5 mg/kg) relative to salinetreated controls and to the lowest dose of amphetamine (0.05 mg/kg). Following: The duration [F(3, 28) = 8.61; P < 0.001] and the frequency [F(3, 28) = 7.58; P < 0.001] of following were decreased after the two higher doses of amphetamine (1.0 and 1.5 mg/kg) relative to saline-treated controls.
Duration (s)
120
Total Sl
Control AMP 0.5 AMP 1.0 AMP 1.5
∗
80 40
++ ∗∗∗
++ ∗∗∗
∗∗
∗∗
+ ∗∗∗
+ ∗∗∗
0 200 Duration (s)
Statistical analysis
Genital investigation: Because of a very low occurrence of genital investigation, this activity could not be analysed statistically.
Locomotion
160 120 80 40 0 160
Duration (s)
Amphetamine (0.5; 1.0; 1.5 mg/kg), cocaine (0.5; 1.0; 1.5; 2.5; 5.0; 10 mg/kg) or MDMA (2.5; 5.0; 10 mg/kg) was dissolved in distilled water and administered in a volume of 1 ml/kg. These doses were chosen on the basis of our preliminary data showing that these doses do not induce stereotyped behaviour. Saline (the same timing and injection volume) was administered to the control groups. The interval of 45 min was chosen on the basis of our published (Rambousek et al., 2014) and some unpublished pharmacokinetic data showing that brain concentrations of psychostimulants reach a peak between the 45th and the 60th minute after administration.
Mutual sniffing: The time spent in mutual sniffing was decreased after all doses of amphetamine [F(3, 28) = 18.49; P < 0.001]. The frequency of mutual sniffing [F(3, 28) = 11.68; P < 0.001] was decreased after the two higher doses of amphetamine (1.0 and 1.5 mg/kg) relative to both salinetreated controls and to rats treated with the lowest dose of amphetamine (0.05 mg/kg) (Table 1).
Rearing
120 80 40 0
Effect of amphetamine on the total time spent in social interaction. Values are mean ± SEM (n = 8 pairs). *P < 0.01, **P < 0.001, ***P < 0.0001 versus saline-treated control rats. +P < 0.05, + +P < 0.01 versus rats receiving the lowest dose of 0.5 mg/kg of amphetamine. AMP, amphetamine; SI, social interaction.
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
Social interaction and psychostimulants Šlamberová et al. 779
Effect of amphetamine on particular patterns of social interaction in adult male rats
Table 1
Social interaction pattern
Saline
Mutual sniffing Duration (s) 69.98 ± 6.7 Number 14.38 ± 1.6 Genital investigation Duration (s) LO Number LO Allo-grooming Duration (s) 9.99 ± 1.5 Number 2.38 ± 0.3 Following Duration (s) 23.31 ± 3.1 Number 6.25 ± 0.8 Climbing over Duration (s) 7.39 ± 2.3 Number 2.13 ± 0.8 Crawling under Duration (s) 0 Number 0
Amphetamine 0.5 mg/kg
Amphetamine 1.0 mg/kg
Amphetamine 1.5 mg/kg
34.56 ± 7.2** 10.86 ± 1.7
9.40 ± 6.6*** 3.63 ± 1.5***, +
8.80 ± 6.6*** 3.63 ± 1.5***, +
LO LO
LO LO
LO LO
4.37 ± 1.6 1.57 ± 0.3
0*** 0***, + +
0*** 0***, + +
14.58 ± 3.3 4.14 ± 0.9
6.44 ± 3.2* 2.25 ± 0.8*
2.58 ± 2.1** 0.88 ± 0.7**
8.59 ± 2.5 2.57 ± 0.8
3.42 ± 2.3 1.63 ± 0.7
0.52 ± 1.2 0.25 ± 0.7
0.36 ± 0.2 0.14 ± 0.1
Particular patterns of social interaction Mutual sniffing
The duration [F(6, 50) = 7.87; P < 0.001] and the frequency [F(6, 50) = 7.37; P < 0.001] of mutual sniffing were lowered by high doses of cocaine (2.5, 5.0, 10 mg/kg) relative to saline-treated controls (Table 2). Genital investigation
Low doses of cocaine (0.5, 1.0, 1.5 mg/kg) did not elicit genital investigation, which was significantly less than the duration [F(6, 50) = 2.92; P < 0.05] or the frequency [F(6, 50) = 2.94; P < 0.05] of genital investigation induced by 5.0 mg/kg of cocaine. Allo-grooming
0 0
0 0
Values are mean ± SEM (n = 8 pairs). LO, ‘low occurrence’ – this activity could not be statistically analysed because of a very low occurrence. *P < 0.01. **P < 0.001. ***P < 0.0001 versus saline-treated rats. + P < 0.05. ++ P < 0.01 versus rats treated with amphetamine 0.05 mg/kg.
The duration and frequency of allo-grooming were increased after the 1.5 mg/kg dose of cocaine, but frequency was decreased after higher doses (2.5; 5.0; 10 mg/kg) relative to saline-treated controls. In addition, the duration [F(6, 50) = 3.86; P < 0.01] and the frequency [F(6, 50) = 7.41; P < 0.001] of allo-grooming were lower after high doses of Fig. 2
Climbing over: There were no significant effects on the duration [F(3, 28) = 2.39; NS] or the frequency [F(3, 28) = 1.62; NS] of climbing over the other animal. Duration (s)
140 120 100 80 60 40 20 0
Duration (s)
Crawling under: There were no significant effects of amphetamine on the duration [F(3, 28) = 1.16; NS] or the frequency [F(3, 28) = 1.16; NS] of crawling under the other animal.
Total Sl
140 120 100 80 60 40 20 0
Particular patterns of nonsocial behaviour
Rearing: Animals administered 1.0 and 1.5 mg/kg spent more time in rearing [F(3, 28) = 16.17; P < 0.001] relative to saline-treated rats as well as rats receiving 0.5 mg/kg (Fig. 1), whereas only the highest dose of amphetamine (1.5 mg/kg) increased the frequency of rearing relative to saline-treated controls [F(3, 28) = 3.22; P < 0.05] (data not shown). Cocaine Total social interaction
As shown in Fig. 2, cocaine at higher doses (2.5, 5.0, 10 mg/kg) decreased total SI relative to saline [F(6, 50) = 8.19; P < 0.001] and relative to lower doses of cocaine (0.5, 1.0, 1.5 mg/kg).
150 Duration (s)
Locomotion: Animals administered 1.0 and 1.5 mg/kg amphetamine spent more time walking relative to salinetreated rats [F(3, 28) = 10.71; P < 0.001] (Fig. 1), whereas the frequency of acts of walking did not differ significantly between groups [F(3, 28) = 1.81; NS] (data not shown).
Control COC 0.5 COC 1.0 COC 1.5
COC 2.5 COC 5.0 COC 10
+ ∗
+ ∗
+ ∗
+ ∗∗
∗
∗∗
Locomotion
Rearing
100 50 0
Effect of cocaine on the total time spent in social interaction. Values are mean ± SEM (n = 8–9 pairs).*P < 0.01,**P < 0.001 versus saline-treated control rats. +P < 0.05 versus rats receiving the 1.5 mg/kg of cocaine. COC, cocaine; SI, social interaction.
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
780 Behavioural Pharmacology 2015, Vol 26 No 8
Table 2
Effect of cocaine on particular patterns of social interaction in adult male rats
Social interaction pattern Mutual sniffing Duration (s) Number Genital investigation Duration (s) Number Allo-grooming Duration (s) Number Following Duration (s) Number Climbing over Duration (s) Number Crawling under Duration (s) Number
Saline 69.98 ± 8.9 14.38 ± 1.5
Cocaine 0.5 mg/kg Cocaine 1.0 mg/kg Cocaine 1.5 mg/kg Cocaine 2.5 mg/kg Cocaine 5.0 mg/kg Cocaine 10 mg/kg 50.59 ± 8.8 9.5 ± 1.4
44.15 ± 7.8 8.50 ± 1.5
36.95 ± 7.6 8.38 ± 1.2
5.91 ± 3.48 0.89 ± 0.82
0 0
0 0
0 0
8.88 ± 4.1 2.11 ± 0.7
13.58 ± 5.5 2.88 ± 0.6
18.88 ± 5.3 2.74 ± 0.7
23.02 ± 5.6* 3.63 ± 0.8*
22.65 ± 7.0 6.22 ± 1.1
35.55 ± 6.8 7.88 ± 1.2
31.64 ± 6.9 7.00 ± 0.9
41.01 ± 6.8 9.13 ± 1.0
14.76 ± 7.5** 4.75 ± 1.4***
18.37 ± 6.8** 5.75 ± 1.5***
10.27 ± 3.6 2.25 ± 0.7
16.57 ± 3.5+ 3.75 ± 0.8+
0.22 ± 4.0+ 0.13 ± 0.5*, + 28.47 ± 6.5 7.13 ± 1.3
0.72 ± 4.2+ 0.13 ± 0.5*, + 26.64 ± 6.3 7.5 ± 1.2
15.61 ± 7.6** 4.00 ± 1.2*** 7.24 ± 3.3 2.38 ± 0.8 0.29 ± 4.3+ 0.13 ± 0.5*, + 23.64 ± 6.4 6.63 ± 1.1
7.51 ± 0.9 2.14 ± 0.4
2.85 ± 1.0* 0.88 ± 0.4*
2.32 ± 1.2* 0.5 ± 0.3*
1.39 ± 1.1* 0.38 ± 0.2*
0.22 ± 0.9** 0.13 ± 0.3**
0.21 ± 1.1** 0.13 ± 0.3**
0.18 ± 1.2** 0.13 ± 0.3**
LO LO
LO LO
LO LO
LO LO
LO LO
LO LO
LO LO
Values are mean ± SEM (n = 8–9 pairs). LO, ‘low occurrence’ – this activity could not be statistically analysed because of a very low occurrence. *P < 0.05. **P < 0.001. ***P < 0.001 versus saline-treated control rats. + P < 0.001 versus lower doses of cocaine (0.5; 1.0; 1.5 mg/kg).
cocaine (2.5, 5.0, 10 mg/kg) relative to lower doses of cocaine (0.5, 1.0, 1.5 mg/kg). Following
There were no significant differences in the duration [F(6, 50) = 1.08; NS] or the frequency [F(6, 50) = 0,55; NS] of following after cocaine treatment. Climbing over
The duration [F(6, 50) = 3.91; P < 0.01] and frequency [F(6, 50) = 3.56; P < 0.01] of climbing over were dosedependently lowered relative to saline-treated controls.
(Fig. 2). After high doses of cocaine (2.5, 5.0, 10 mg/kg), the frequency of rearing was increased [F(6, 50) = 16.67; P < 0.001] relative to saline-treated controls or to low doses of cocaine (0.5, 1.0, 1.5 mg/kg) (data not shown).
MDMA Total social interaction
As shown in Fig. 3, MDMA did not significantly alter total SI [F(3, 30) = 0.76; NS].
Particular patterns of social interaction Crawling under
Because of a very low occurrence of crawling under the other animal, this activity could not be analysed statistically. Particular patterns of nonsocial behaviour Locomotion
There were no significant differences in the duration of locomotion after cocaine treatment [F(6, 50) = 1.58; NS] (Fig. 2). The frequency of walking [F(6, 50) = 9.71; P < 0.001] was lower after the low doses of cocaine (0.5, 1.0, 1.5 mg/kg) relative to high doses (2.5, 5.0, 10 mg/kg), but no dose differed from saline-treated controls (data not shown). Rearing
As shown in Fig. 2, cocaine at higher doses (2.5, 5.0, 10 mg/kg) increased the time spent in rearing relative to saline-treated controls [F(6, 50) = 6.17; P < 0.001]. In addition, the duration of rearing was higher after the 2.5 mg/kg dose of cocaine in animals than after the 1.5 mg/kg dose
Mutual sniffing: All doses of MDMA decreased the duration [F(3, 30) = 12.60; P < 0.001] and the frequency [F(3, 30) = 31.59; P < 0.001] of mutual sniffing relative to saline-treated controls. In addition, the highest dose of MDMA (10 mg/kg) decreased the frequency of mutual sniffing compared with the lowest dose of MDMA (2.5 mg/kg) (Table 3). Genital investigation: Because of a very low occurrence of genital investigation, this activity could not be analysed statistically. Allo-grooming: The duration [F(3, 30) = 3.72; P < 0.05] and the frequency [F(3, 30) = 7.44; P < 0.001] of allogrooming were decreased after the two higher doses of MDMA (5.0 and 10 mg/kg) relative to the saline-treated control rats. Following: No doses of MDMA affected the duration of following [F(3, 30) = 2.45; NS], whereas the highest dose of MDMA (10 mg/kg) decreased the frequency of following [F(3, 30) = 4.24; P < 0.05] relative to saline control rats.
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
Social interaction and psychostimulants Šlamberová et al. 781
Fig. 3
Control MDMA 2.5 MDMA 5.0 MDMA 10
Total Sl
Duration (s)
160 120
Discussion
80 40
Duration (s)
0 420 360 300 240 180 120 60 0
++ ∗∗∗
Locomotion
+++ ∗∗∗
∗∗∗
Rearing
Duration (s)
200 160 120
[F(3, 30) = 3.97; P < 0.05]. The frequency of rearing (data not shown) was decreased after the two higher doses of MDMA (5.0 and 10 mg/kg) relative to the saline-treated controls or to the lowest dose of MDMA (2.5 mg/kg) [F(3, 30) = 15.52; P < 0.001].
+
80 40 0
Effect of MDMA on the total time spent in social interaction. Values are mean ± SEM (n = 8–10 pairs). ***P < 0.0001 versus saline-treated control rats. +P < 0.05, + +P < 0.001, + + +P < 0.0001 versus rats receiving the lowest dose of 2.5 mg/kg of MDMA. MDMA, 3,4 methylenedimethoxyamphetamine; SI, social interaction.
Climbing over: The duration [F(3, 30) = 4.11; P < 0.05] as well as the frequency [F(3, 30) = 5.00; P < 0.01] of climbing over the other animal were decreased after all the doses of MDMA. Crawling under: Because of a very low occurrence of crawling under the other animal, this activity could not be analysed statistically. Particular patterns of nonsocial behaviour
Locomotion: As shown in Fig. 3, all doses of MDMA increased the duration of locomotion [F(3, 30) = 47.19; P < 0.001] relative to saline-treated controls, and the highest doses of 5.0 and 10 mg/kg even increased the time spent in locomotion relative to the 2.5 mg/kg dose. The frequency of acts of walking (data not shown) was decreased in a dose-dependent manner [F(3, 30) = 16.07; P < 0.001]. Rearing: As shown in Fig. 3, the highest dose of MDMA (10 mg/kg) decreased the duration of rearing relative to the lowest dose (2.5 mg/kg), but not relative to salinetreated controls or rats treated with the 5.0 mg/kg dose
Numerous previous studies of the effects of psychostimulants on social behaviour have been carried out under nonidentical conditions (Ellinwood et al., 1972; Resnick and Resnick, 1984; Miczek and Tidey, 1989; Rademacher et al., 2002; McGregor et al., 2003b; Clemens et al., 2004; Trezza et al., 2014). Standardization of experimental conditions enables a detailed evaluation of the changes induced by different drugs. Moreover, the majority of the studies do not focus on the individual patterns of social behaviour that may be diversely affected by drug manipulation and the test environment. Therefore, the present study is distinctive in two ways. First, it compared the effect of three different psychostimulant drugs (amphetamine, cocaine and MDMA) on social behaviour under standard conditions. Second, in addition to providing an evaluation of social behaviour in general, the present study focused on specific elements of the SI repertoire as well as nonsocial behaviours. Table 4 summarizes our results, showing the differences in effects of the three psychostimulant drugs examined on the specific patterns of SI. All psychostimulant drugs resulted in decreased sociability, as a propensity to spent time with a conspecific, compared with time spent alone in the testing arena (Berton et al., 1997). The decrease in the total SI after the administration of amphetamine and cocaine is in agreement with our previous study showing a decrease in the total SI after MA exposure (Šlamberová et al., 2010) and other studies (McGregor et al., 2003a; Bull et al., 2004; Navarro et al., 2004; Clemens et al., 2007) showing a decrease in SI after MDMA. All the above-mentioned studies tested total SI only, without distinguishing between different social activities. In the present set of experiments, SI was divided into specific patterns of social behaviour, which were affected differently by the drugs under investigation (Table 4). Specifically, the present study has shown that mutual sniffing was decreased by all doses of amphetamine and MDMA and by the higher doses of cocaine and allogrooming was almost suppressed by higher doses of all three drugs. The following of one animal by another was decreased by higher doses of amphetamine and partially by the highest dose of MDMA, but was not affected by any dose of cocaine. Climbing over, in contrast, was decreased by all doses of cocaine and MDMA, with only a nonsignificant tendency toward suppression after amphetamine. In addition, genital investigation was measurable only in saline-treated animals and after higher doses of cocaine, with an increase in genital investigation after the dose of 5.0 mg/kg of cocaine was administered. Genital investigation may describe offensive aggression
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
782 Behavioural Pharmacology 2015, Vol 26 No 8
Table 3
Effect of MDMA on particular patterns of social interaction in adult male rats
Social interaction pattern Mutual sniffing Duration (s) Number Genital investigation Duration (s) Number Allo-grooming Duration (s) Number Following Duration (s) Number Climbing over Duration (s) Number Crawling under Duration (s) Number
Saline
MDMA 2.5 mg/kg
MDMA 5.0 mg/kg
MDMA 10 mg/kg
68.88 ± 6.5 13.70 ± 1.0
32.79 ± 7.3* 5.00 ± 1.1***
27.23 ± 7.2* 2.75 ± 1.0***
12.04 ± 6.8*** 0.50 ± 0.8***, +
LO LO
LO LO
LO LO
LO LO
0.65 ± 3.2** 0.13 ± 0.3**
0** 0**
15.34 ± 3.8 3.1 ± 0.5
12.27 ± 4.3 1.63 ± 0.6
24.02 ± 11.4 6.20 ± 0.7
54.86 ± 12.8 6.00 ± 0.8
51.36 ± 12.7 3.88 ± 0.6
5.86 ± 1.3 1.70 ± 0.4
0.65 ± 1.5* 0.13 ± 0.3*
0* 0*
0* 0*
LO LO
LO LO
LO LO
LO LO
68.56 ± 12.8 2.88 ± 0.7*
Values are mean ± SEM (n = 8–10 pairs). LO, ‘low occurrence’ – this activity could not be statistically analysed because of a very low occurrence; MDMA, 3,4 methylenedimethoxyamphetamine. *P < 0.05. **P < 0.01. ***P < 0.0001 versus saline-treated control rats. + P < 0.05 versus rats treated with 2.5 mg/kg of MDMA.
Table 4
General summary of the effects of psychostimulants on particular patterns of social interaction in adult male rats
Social interaction pattern Amphetamine Cocaine MDMA
Mutual sniffing
Genital investigation
Allo-grooming
Following
Climbing over
Crawling under
↓ ↓ ↓
LO – LO
↓ – ↓
↓ ↓ –
– – ↓
– LO LO
Table shows the general effect (independent of doses) of the psychostimulant drugs examined on the particular patterns of social interaction. ‘↓’, decrease in the activity induced by the psychostimulant drug; ‘–’, no effect of the psychostimulant drug on the activity; LO, ‘low occurrence’ – this activity could not be statistically analysed because of a very low occurrence; MDMA, 3,4 methylenedimethoxyamphetamine.
(Pellis, 1988); thus, this result is consistent with a proaggressive effect of cocaine at higher doses (Blanchard and Blanchard, 1999). However, in our experimental setting, we did not observe any other forms of aggressive behaviours such as boxing, aggressive fighting or biting attack. These forms of aggressive behaviour occur mostly in a resident-intruder test when resident rats express their territorial advantage in their environment. In the present study, the rats were familiarized with the testing arena for only a short period before testing; thus, there was no time to create a territorial dominance in the arena. In general, age-matched and weight-matched rats, as were used in the present study, do not usually express aggression and none of the drugs induced aggression per se. One of the main goals of the present study was to differentiate the effects of the psychostimulants examined on specific patterns of social behaviour. These differences may be explained by different effects on the neurotransmitters noradrenaline, dopamine and serotonin. In particular, amphetamine affects mostly the noradrenergic, less the dopaminergic and least the serotoninergic systems, whereas cocaine affects mostly the dopaminergic and serotoninergic systems (Fleckenstein et al., 2000; Rothman et al., 2001; Shoblock et al., 2003),
whereas MDMA affects predominantly the serotoninergic system, but also dopaminergic and noradrenergic systems (Yamamoto and Spanos, 1988; Bengel et al., 1998; Bankson and Cunningham, 2001; Cole and Sumnall, 2003). Thus, it seems that drugs that have greater effects on the serotonergic system (cocaine and MDMA) exerted greater effects on climbing, in comparison with amphetamine, which has a lesser effect on the serotonergic system. However, following was decreased by amphetamine and MDMA, but not cocaine, which corresponds with the effect of these drugs on the noradrenergic system. The neural network for social behaviours includes the amygdala and other limbic structures, the ventral hypothalamus, the prefrontal cortex, the preoptic area and the midbrain, and some of these structures interact with the drug reward circuit (Bachevalier and Loveland, 2006; Everitt et al., 2008; Siviy and Panksepp, 2011; Albers, 2012). One of the brain structures that seems to be involved in both the social behaviour neural network and the drug reward circuit is the striatum (Baez-Mendoza and Schultz, 2013). It has been hypothesized that activity in the striatum integrates actions, including social actions, with rewards (Baez-Mendoza and Schultz, 2013). Moreover,
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
Social interaction and psychostimulants Šlamberová et al. 783
social behaviour had been shown to involve several neurotransmitter systems, such as endogenous opioid and cannabinoid systems, as well as the dopaminergic noradrenergic and serotoninergic systems that are directly involved in the mechanisms of action of psychostimulant drugs (Panksepp et al., 1980; Niesink and Van Ree, 1989; Vanderschuren et al., 1997; Trezza et al., 2014). A question is whether the decreased SI could be interpreted as anxiety-like behaviour, as suggested by File and Hyde (1978), who proposed that the decrease in active SI under different environmental stress conditions could be considered anxiogenic behaviour, whereas an increase in active SI reflected an anxiolytic effect. The same conclusion was reached in our previous study (Šlamberová et al., 2010) showing that the administration of MA impairs SI in a dose-specific and stress conditionspecific manner suggestive of an anxiogenic effect. However, because another study indicated that acute administration of MA in adulthood exerts an anxiolyticlike effect in the elevated plus-maze (Schutová et al., 2010), we suggest being more careful about this conclusion. Moreover, various studies have reported contradictory findings, ranging from anxiolytic action, through no effect, to anxiogenic action (Miczek et al., 1989; Paine et al., 2002; Navarro et al., 2004; Hayase et al., 2005b). Such results suggest that SIT and nonsocial tests of anxiety probably measure different states of fear (File, 1991; Chaouloff et al., 1994). In addition, behavioural variability observed in rats in social and nonsocial environments is influenced by genetic factors as shown by the comparison of six inbred rat strains (Berton et al., 1997). As for nonsocial activities, the present data showed that amphetamine at higher doses (1.0 and 1.5 mg/kg) and all doses of MDMA increased locomotion, whereas exploratory rearing was increased after higher doses of amphetamine (1.0 and 1.5 mg/kg) and cocaine (2.5, 5.0 and 10 mg/kg). This type of response is considered to reflect not only exploratory activity but also emotionality (Lever et al., 2006). In contrast to these findings, the highest dose of MDMA (10 mg/kg) decreased rearing relative to the lowest dose of MDMA (2.5 mg/kg). Our finding that MDMA increased locomotion is in agreement with our earlier observation that 5.0 mg/kg MDMA increased locomotion when animals were tested in their home cages and behaviour was evaluated by an automated system (Šlamberová et al., 2013). That study also reported that cocaine at 5.0 mg/kg increased the exploratory rearing, whereas the dose of 5.0 mg/kg of MDMA did not affect rearing, again in agreement with the present results. Similarly, results have been reported in other studies: for example, Bull et al. (2004) reported that MDMA (5.0 mg/kg) increased the locomotion, but did not alter the rearing activity, and amphetamine has frequently been shown to increase locomotor activity (e.g. Melnick and Dow-Edwards, 2001; Bisagno et al., 2003). Thus, it seems that the effect of psychostimulants
on locomotor and exploratory (rearing) behaviour is drug and dose specific. Because it is known that psychostimulants at high doses increase locomotion and stereotypies (Tzschentke and Schmidt, 1998; Broderick et al., 2003), in the present study, we used lower doses that do not induce any stereotypical behaviours that might affect performance in the SIT. Taken together, our results show that psychostimulant-treated animals preferred nonsocial activities to SI, suggesting that these drugs alter decrease in motivation to interact socially. The drugs did not induce stereotyped behaviour, the repetition of seemingly purposeless acts such as gnawing or sniffing in a restricted location (Evenden and Ryan, 1988); thus, we assume that the reduced expression of social investigation is not secondary to stereotyped behaviour. It should be noted that the increase in locomotor and exploratory (rearing) behaviour may secondarily alter the SI. It is therefore possible that some decreases in SI may be because of increases in locomotion especially after the higher doses of amphetamine or cocaine. However, even though low doses of psychostimulants caused no increase in the locomotion or exploration, they decreased some specific patterns of SI; thus, the mutual influence seems to be only partial. Nevertheless, it is difficult to determine whether these are two independent effects or whether the decrease in SI was the result of response competition. For example, in the study of File and Hyde (1978), amphetamine decreased the time spent in SI but also increased locomotion, whereas Sams-Dodd (1998) observed increased locomotion with slightly decreased or no effect on social behaviour. In addition, factor analysis has shown that locomotion is a component of social behaviour in this test, and the measures can covary to an extent, such that walking is not entirely independent of anxiety (Lapiz-Bluhm et al., 2008). The methodology may also have an important influence on the data analysis. We gave preference to manual analysis by an experienced observer over an automated analysis because an experienced observer can better distinguish between the specific patterns of the SI repertoire, whereas an automated system cannot, and the evaluation of specific patterns of SI was one of the main goals of the present study. Locomotion and exploratory rearing were analysed as in the duration and frequency of the activity rather than the distance travelled (as in an automated system) or the number of squares crossed. Manual and automated methods each have their pros and cons. The limitation of the method used in the present study is that it does not show the distance travelled, which might provide a better measure of hyperactivity induced by the psychostimulant drugs. Nevertheless, we assume that the evaluation of locomotion by a videotracking system and the ethological approach that was used in the present study would yield highly similar results. Future studies are needed to address this issue.
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
784 Behavioural Pharmacology 2015, Vol 26 No 8
In conclusion, these findings extend the knowledge of psychostimulant effects on social behaviour. SI was decreased even by drugs, such as MDMA, known as socializing party drugs. We also show that not only overall social activity per se is affected but also specific patterns of SI compared with the effects of different drugs under standard conditions. Moreover, we show that after higher doses of amphetamine and cocaine, the animals prefer nonsocial exploratory activities rather than engagement in the investigation of a conspecific, suggesting deficit in the levels of emotionality and hyperactivity/hyperarousal. A variety of neuropsychiatric disorders are characterized by inappropriate or altered social behaviour and social cognition, including depression, autism spectrum disorders, bipolar disorders, obsessive-compulsive disorders and schizophrenia (Blumstein et al., 2010). The present study also adds a new dimension to this field of psychiatric research.
Acknowledgements This study was supported by grant 14-03708S from the Grant Agency of the Czech Republic, project #PRVOUK P34 and project #260168/SVV/2015 from Charles University in Prague and project #NT/14484 from the Internal Grant Agency of Ministry of Health of the Czech Republic. The procedures for animal experimentation utilized in this report was reviewed and approved by the Institutional Animal Care and Use Committee and are in agreement with the Czech Government Requirements under the Policy of Humans Care of Laboratory Animals (No. 246/1992) and with the regulations of the Ministry of Agriculture of the Czech Republic (No. 311/1997). Conflicts of interest
There are no conflicts of interest.
References Achterberg EJ, Trezza V, Siviy SM, Schrama L, Schoffelmeer AN, Vanderschuren LJ (2014). Amphetamine and cocaine suppress social play behavior in rats through distinct mechanisms. Psychopharmacology (Berl) 231:1503–1515. Albers HE (2012). The regulation of social recognition, social communication and aggression: vasopressin in the social behavior neural network. Horm Behav 61:283–292. Ando RD, Benko A, Ferrington L, Kirilly E, Kelly PA, Bagdy G (2006). Partial lesion of the serotonergic system by a single dose of MDMA results in behavioural disinhibition and enhances acute MDMA-induced social behaviour on the social interaction test. Neuropharmacology 50:884–896. Baarendse PJ, Limpens JH, Vanderschuren LJ (2014). Disrupted social development enhances the motivation for cocaine in rats. Psychopharmacology (Berl) 231:1695–1704. Bachevalier J, Loveland KA (2006). The orbitofrontal-amygdala circuit and selfregulation of social-emotional behavior in autism. Neurosci Biobehav Rev 30:97–117. Baez-Mendoza R, Schultz W (2013). The role of the striatum in social behavior. Front Neurosci 7:233. Bankson MG, Cunningham KA (2001). 3,4-Methylenedioxymethamphetamine (MDMA) as a unique model of serotonin receptor function and serotonindopamine interactions. J Pharmacol Exp Ther 297:846–852. Bengel D, Murphy DL, Andrews AM, Wichems CH, Feltner D, Heils A, et al. (1998). Altered brain serotonin homeostasis and locomotor insensitivity to 3, 4-methylenedioxymethamphetamine (‘Ecstasy’) in serotonin transporterdeficient mice. Mol Pharmacol 53:649–655.
Berton O, Ramos A, Chaouloff F, Mormde P (1997). Behavioral reactivity to social and nonsocial stimulations: a multivariate analysis of six inbred rat strains. Behav Genet 27:155–166. Bisagno V, Ferguson D, Luine VN (2003). Chronic D-amphetamine induces sexually dimorphic effects on locomotion, recognition memory, and brain monoamines. Pharmacol Biochem Behav 74:859–867. Blanchard DC, Blanchard RJ (1999). Cocaine potentiates defensive behaviors related to fear and anxiety. Neurosci Biobehav Rev 23:981–991. Blumstein DT, Ebensperger LA, Hayes LD, Vasquez RA, Ahern TH, Burger JR, et al. (2010). Toward an integrative understanding of social behavior: new models and new opportunities. Front Behav Neurosci 4:34. Broderick PA, Rahni DN, Zhou Y (2003). Acute and subacute effects of risperidone and cocaine on accumbens dopamine and serotonin release using in vivo microvoltammetry on line with open-field behavior. Prog Neuropsychopharmacol Biol Psychiatry 27:1037–1054. Bull EJ, Hutson PH, Fone KC (2004). Decreased social behaviour following 3,4-methylenedioxymethamphetamine (MDMA) is accompanied by changes in 5-HT2A receptor responsivity. Neuropharmacology 46:202–210. Chaouloff F, Castanon N, Mormede P (1994). Paradoxical differences in animal models of anxiety among the Roman rat lines. Neurosci Lett 182:217–221. Clemens KJ, Van Nieuwenhuyzen PS, Li KM, Cornish JL, Hunt GE, McGregor IS (2004). MDMA (‘ecstasy’), methamphetamine and their combination: longterm changes in social interaction and neurochemistry in the rat. Psychopharmacology (Berl) 173:318–325. Clemens KJ, Cornish JL, Hunt GE, McGregor IS (2007). Repeated weekly exposure to MDMA, methamphetamine or their combination: long-term behavioural and neurochemical effects in rats. Drug Alcohol Depend 86:183–190. Cole JC, Sumnall HR (2003). The pre-clinical behavioural pharmacology of 3,4-methylenedioxymethamphetamine (MDMA). Neurosci Biobehav Rev 27:199–217. Daza-Losada M, Rodriguez-Arias M, Maldonado C, Aguilar MA, Guerri C, Minarro J (2009). Acute behavioural and neurotoxic effects of MDMA plus cocaine in adolescent mice. Neurotoxicol Teratol 31:49–59. Ellinwood EH Jr, Sudilovsky A, Nelson L (1972). Behavioral analysis of chronic amphetamine intoxication. Biol Psychiatry 4:215–230. Evenden JL, Ryan CN (1988). Behavioral responses to psychomotor stimulant drugs: localization in the central nervous system. Pharmacol Ther 36:151–172. Everitt BJ, Belin D, Economidou D, Pelloux Y, Dalley JW, Robbins TW (2008). Review. Neural mechanisms underlying the vulnerability to develop compulsive drug-seeking habits and addiction. Philos Trans R Soc Lond B Biol Sci 363:3125–3135. File SE (1991). The biological basis of anxiety. In: Meltzer HY, Nerozzi D, editors. Current practices and future developments in the pharmacotherapy of mental disorders. Amsterdam: Elsevier. pp. 159–165. File SE, Hyde JR (1978). Can social interaction be used to measure anxiety? Br J Pharmacol 62:19–24. File SE, Seth P (2003). A review of 25 years of the social interaction test. Eur J Pharmacol 463:35–53. Fleckenstein AE, Gibb JW, Hanson GR (2000). Differential effects of stimulants on monoaminergic transporters: pharmacological consequences and implications for neurotoxicity. Eur J Pharmacol 406:1–13. Hayase T, Yamamoto Y, Yamamoto K (2005). Persistent anxiogenic effects of a single or repeated doses of cocaine and methamphetamine: interactions with endogenous cannabinoid receptor ligands. Behav Pharmacol 16:395–404. Holly EN, Shimamoto A, Debold JF, Miczek KA (2012). Sex differences in behavioral and neural cross-sensitization and escalated cocaine taking as a result of episodic social defeat stress in rats. Psychopharmacology (Berl) 224:179–188. Homberg JR, Schiepers OJ, Schoffelmeer AN, Cuppen E, Vanderschuren LJ (2007). Acute and constitutive increases in central serotonin levels reduce social play behaviour in peri-adolescent rats. Psychopharmacology (Berl) 195:175–182. Iversen L, White M, Treble R (2014). Designer psychostimulants: pharmacology and differences. Neuropharmacology 87:59–65. Krsiak M (1975). Timid singly-housed mice: their value in prediction of psychotropic activity of drugs. Br J Pharmacol 55:141–150. Lapiz-Bluhm MD, Bondi CO, Doyen J, Rodriguez GA, Bedard-Arana T, Morilak DA (2008). Behavioural assays to model cognitive and affective dimensions of depression and anxiety in rats. J Neuroendocrinol 20:1115–1137. Lever C, Burton S, O’Keefe J (2006). Rearing on hind legs, environmental novelty, and the hippocampal formation. Rev Neurosci 17:111–133. Maldonado E, Navarro JF (2001). MDMA (‘ecstasy’) exhibits an anxiogenic-like activity in social encounters between male mice. Pharmacol Res 44:27–31.
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
Social interaction and psychostimulants Šlamberová et al. 785
McGregor IS, Clemens KJ, Van der Plasse G, Li KM, Hunt GE, Chen F, Lawrence AJ (2003a). Increased anxiety 3 months after brief exposure to MDMA (‘Ecstasy’) in rats: association with altered 5-HT transporter and receptor density. Neuropsychopharmacology 28:1472–1484. McGregor IS, Gurtman CG, Morley KC, Clemens KJ, Blokland A, Li KM, et al. (2003b). Increased anxiety and ‘depressive’ symptoms months after MDMA (‘ecstasy’) in rats: drug-induced hyperthermia does not predict long-term outcomes. Psychopharmacology (Berl) 168:465–474. McGregor IS, Callaghan PD, Hunt GE (2008). From ultrasocial to antisocial: a role for oxytocin in the acute reinforcing effects and long-term adverse consequences of drug use? Br J Pharmacol 154:358–368. Melnick SM, Dow-Edwards DL (2001). Differential behavioral responses to chronic amphetamine in adult male and female rats exposed to postnatal cocaine treatment. Pharmacol Biochem Behav 69:219–224. Miczek KA, Tidey JW (1989). Amphetamines: aggressive and social behavior. NIDA Res Monogr 94:68–100. Miczek KA, Haney M, Tidey J, Vatne T, Weerts E, DeBold JF (1989). Temporal and sequential patterns of agonistic behavior: effects of alcohol, anxiolytics and psychomotor stimulants. Psychopharmacology (Berl) 97:149–151. Miczek KA, de Boer SF, Haller J (2013). Excessive aggression as model of violence: a critical evaluation of current preclinical methods. Psychopharmacology (Berl) 226:445–458. Mikulecká A, Šubrt M, Pařízková M, Mareš P, Kubová H (2014). Consequences of early postnatal benzodiazepines exposure in rats. II. Social behavior. Front Behav Neurosci 8:169. Morley KC, McGregor IS (2000). (+ / − )-3,4-methylenedioxymethamphetamine (MDMA,‘Ecstasy’) increases social interaction in rats. Eur J Pharmacol 408:41–49. Morley KC, Arnold JC, McGregor IS (2005). Serotonin (1A) receptor involvement in acute 3,4-methylenedioxymethamphetamine (MDMA) facilitation of social interaction in the rat. Prog Neuropsychopharmacol Biol Psychiatry 29:648–657. Navarro JF, Maldonado E (1999). Behavioral profile of 3,4-methylenedioxymethamphetamine (MDMA) in agonistic encounters between male mice. Prog Neuropsychopharmacol Biol Psychiatry 23:327–334. Navarro JF, Rivera A, Maldonado E, Cavas M, de la Calle A (2004). Anxiogenic-like activity of 3,4-methylenedioxy-methamphetamine (‘Ecstasy’) in the social interaction test is accompanied by an increase of c-fos expression in mice amygdala. Prog Neuropsychopharmacol Biol Psychiatry 28:249–254. Niesink RJ, Van Ree JM (1989). Involvement of opioid and dopaminergic systems in isolation-induced pinning and social grooming of young rats. Neuropharmacology 28:411–418. Paine TA, Jackman SL, Olmstead MC (2002). Cocaine-induced anxiety: alleviation by diazepam, but not buspirone, dimenhydrinate or diphenhydramine. Behav Pharmacol 13:511–523. Palenicek T, Votava M, Bubenikova V, Horacek J (2005). Increased sensitivity to the acute effects of MDMA (‘ecstasy’) in female rats. Physiol Behav 86:546–553. Panksepp J, Herman BH, Vilberg T, Bishop P, DeEskinazi FG (1980). Endogenous opioids and social behavior. Neurosci Biobehav Rev 4:473–487. Pellis SM (1988). Agonistic versus amicable targets of attack and defense: consequences for the origin, function, and descriptive classification of playfighting. Aggr Behav 14:85–104. Rademacher DJ, Schuyler AL, Kruschel CK, Steinpreis RE (2002). Effects of cocaine and putative atypical antipsychotics on rat social behavior: an ethopharmacological study. Pharmacol Biochem Behav 73:769–778. Rambousek L, Kacer P, Syslova K, Bumba J, Bubenikova-Valesova V, Slamberova R (2014). Sex differences in methamphetamine pharmacokinetics in adult rats and its transfer to pups through the placental membrane and breast milk. Drug Alcohol Depend 139:138–144. Resnick RB, Resnick EB (1984). Cocaine abuse and its treatment. Psychiatr Clin North Am 7:713–728. Rothman RB, Baumann MH (2006). Balance between dopamine and serotonin release modulates behavioral effects of amphetamine-type drugs. Ann N Y Acad Sci 1074:245–260.
Rothman RB, Baumann MH, Dersch CM, Romero DV, Rice KC, Carroll FI, Partilla JS (2001). Amphetamine-type central nervous system stimulants release norepinephrine more potently than they release dopamine and serotonin. Synapse 39:32–41. Sams-Dodd F (1998). Effects of continuous D-amphetamine and phencyclidine administration on social behaviour, stereotyped behaviour, and locomotor activity in rats. Neuropsychopharmacology 19:18–25. Schutová B, Hrubá L, Pometlová M, Deykun K, Šlamberová R (2009). Cognitive functions and drug sensitivity in adult male rats prenatally exposed to methamphetamine. Physiol Res 58:741–750. Schutová B, Hrubá L, Pometlová M, Rokyta R, Šlamberová R (2010). Responsiveness to methamphetamine in adulthood is altered by prenatal exposure in rats. Physiol Behav 99:381–387. Shoblock JR, Sullivan EB, Maisonneuve IM, Glick SD (2003). Neurochemical and behavioral differences between D-methamphetamine and D-amphetamine in rats. Psychopharmacology (Berl) 165:359–369. Siviy SM, Panksepp J (2011). In search of the neurobiological substrates for social playfulness in mammalian brains. Neurosci Biobehav Rev 35:1821–1830. Šlamberová R, Mikulecká A, Pometlová M, Schutová B, Hrubá L, Deykun K (2010). The effect of methamphetamine on social interaction of adult male rats. Behav Brain Res 214:423–427. Šlamberová R, Mikulecká A, Pometlová M, Schutová B, Hrubá L, Deykun K (2011). Sex differences in social interaction of methamphetamine-treated rats. Behav Pharmacol 22:617–623. Šlamberová R, Macúchová E, Nohejlová-Deykun K, Schutová B, Hrubá L, Rokyta R (2013). Gender differences in the effect of prenatal methamphetamine exposure and challenge dose of other drugs on behavior of adult rats. Physiol Res 62:S99–S108. Sommers I, Baskin D, Baskin-Sommers A (2006). Methamphetamine use among young adults: health and social consequences. Addict Behav 31:1469–1476. Syme LA, Syme GJ (1974). Group instability and the social response to methamphetamine. Pharmacol Biochem Behav 2:851–854. Thompson MR, Callaghan PD, Hunt GE, Cornish JL, McGregor IS (2007). A role for oxytocin and 5-HT(1A) receptors in the prosocial effects of 3,4 methylenedioxymethamphetamine (‘ecstasy’). Neuroscience 146:509–514. Thompson VB, Heiman J, Chambers JB, Benoit SC, Buesing WR, Norman MK, et al. (2009). Long-term behavioral consequences of prenatal MDMA exposure. Physiol Behav 96:593–601. Tikal K, Benešová O (1972). The effect of some psychotropic drugs on contact behavior in a group. Act Nerv Super (Praha) 14:168–169. Trezza V, Campolongo P, Vanderschuren LJ (2011). Evaluating the rewarding nature of social interactions in laboratory animals. Dev Cogn Neurosci 1:444–458. Trezza V, Baarendse PJ, Vanderschuren LJ (2014). On the interaction between drugs of abuse and adolescent social behavior. Psychopharmacology (Berl) 231:1715–1729. Tzschentke TM, Schmidt WJ (1998). The development of cocaine-induced behavioral sensitization is affected by discrete quinolinic acid lesions of the prelimbic medial prefrontal cortex. Brain Res 795:71–76. Vanderschuren LJ, Niesink RJ, Van Ree JM (1997). The neurobiology of social play behavior in rats. Neurosci Biobehav Rev 21:309–326. Varlinskaya EI, Spear LP (2008). Social interactions in adolescent and adult Sprague–Dawley rats: impact of social deprivation and test context familiarity. Behav Brain Res 188:398–405. Williams MT, Moran MS, Vorhees CV (2003). Refining the critical period for methamphetamine-induced spatial deficits in the Morris water maze. Psychopharmacology (Berl) 168:329–338. Wolff K, Tsapakis EM, Winstock AR, Hartley D, Holt D, Forsling ML, Aitchison KJ (2006). Vasopressin and oxytocin secretion in response to the consumption of ecstasy in a clubbing population. J Psychopharmacol 20:400–410. Yamamoto BK, Spanos LJ (1988). The acute effects of methylenedioxymethamphetamine on dopamine release in the awake-behaving rat. Eur J Pharmacol 148:195–203. Zernig G, Kummer KK, Prast JM (2013). Dyadic social interaction as an alternative reward to cocaine. Front Psychiatry 4:100.
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
Research report
Effects of psychostimulants on social interaction in adult male rats Romana Šlamberováa, Anna Mikuleckáb, Eva Macúchováa, Ivana Hrebíčkováa, Mária Ševčíkováa, Kateryna Nohejlováa and Marie Pometlováa Psychostimulants are known to have a huge impact on different forms of social behaviour. The aim of the present study was to compare the effects of three different psychostimulants [amphetamine, cocaine and 3,4 methylenedimethoxyamphetamine (MDMA)] on social interaction (SI) in adult male rats. The SI test was performed in a familiar arena and under low-stress environmental conditions. Experimental animals received amphetamine (0.5, 1.0, 1.5 mg/kg), cocaine (0.5, 1.0, 1.5, 2.5, 5.0, 10.0 mg/kg) or MDMA (2.5, 5.0, 10 mg/kg) and control animals received saline (1 ml/kg) 45 min before the SI test. Time spent in SI (individual patterns of social behaviour) and nonsocial activities (locomotion and rearing) were video recorded and then analysed offline, with the following results: (a) all doses of amphetamine decreased SI. Specifically, all doses of amphetamine decreased mutual sniffing, and the higher doses also decreased allo-grooming and following behaviours. (b) The higher doses of cocaine decreased SI, especially mutual sniffing, allo-grooming and climbing over. Cocaine at the dose of 5.0 mg/kg increased genital investigation compared with lower doses. (c) All doses of MDMA decreased mutual sniffing and climbing over; the two
Introduction Psychostimulants have been shown to have considerable effects on a great variety of behaviours in both humans (Sommers et al., 2006) and laboratory animals. Chronic exposure to psychostimulant drugs in extreme cases may result in aggressive psychosis and paranoia (McGregor et al., 2008). Individuals with substance use disorders often show severely impaired social interaction (SI), preferring drugs of abuse instead of social contact (Zernig et al., 2013). Long-lasting alterations in emotional state, such as fear, anxiety, social receptivity and depressive symptoms, as well as memory deficits have been observed in the laboratory rats administered psychostimulants (Williams et al., 2003; McGregor et al., 2003b; Navarro et al., 2004; Hayase et al., 2005; Páleníček et al., 2005; Thompson et al., 2008; Schutová et al., 2009), which match the long-term changes reported in human studies (Clemens et al., 2007). Some animal studies examining the effects of acute psychostimulant administration have reported an anxiolytic-like action of these drugs in various animal models, even though there is also substantial evidence supporting an anxiogenic-like effect (Paine et al., 2002; Navarro et al., 2004). 0955-8810 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
higher doses decreased allo-grooming behaviour, and only the highest dose decreased following. The two higher doses of amphetamine and all the doses of MDMA increased locomotion and rearing; cocaine did not affect locomotion, but increased rearing at higher doses. In conclusion, the results confirm the well-known finding that psychostimulants suppress SI, but also show novel differences in the effects of psychostimulants on specific patterns of SI. Behavioural Pharmacology 26:776–785 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. Behavioural Pharmacology 2015, 26:776–785 Keywords: amphetamine, cocaine, male rats, 3,4 methylenedimethoxyamphetamine, psychostimulants, social behavior a Department of Normal, Pathological and Clinical Physiology, Third Faculty of Medicine, Charles University in Prague and bDepartment of Developmental Epileptology, Academy of Sciences of the Czech Republic, Institute of Physiology, Prague, Czech Republic
Correspondence to Romana Šlamberová, MD, PhD, Department of Normal, Pathological and Clinical Physiology, Third Faculty of Medicine, Charles University in Prague, Ke Karlovu 4, 120 00 Prague 2, Czech Republic E-mail: [email protected] Received 14 November 2014 Accepted as revised 30 April 2015
Psychostimulants, especially 3,4 methylenedimethoxyamphetamine (MDMA), are usually considered socializing drugs because they are often used to increase activity in dancing clubs and parties. Animal models of this drug abuse, however, show that the opposite seems to be true. Many studies (Miczek and Tidey, 1989; Ando et al., 2006; Trezza et al., 2014), including our own (Šlamberová et al., 2010, 2011), repeatedly show that psychostimulants decrease social behaviour in rats. For example acute treatment with MDMA inhibits social play behaviour (Homberg et al., 2007) and decreases social investigation at high doses (Navarro and Maldonado, 1999; Maldonado and Navarro, 2001; Daza-Losada et al., 2009). Nevertheless, there are also studies supporting the assumption of a prosocial effect of MDMA (Morley and McGregor, 2000; Thompson et al., 2007). It seems that the prosocial or antisocial effect of psychostimulants depends on the dose as well as on the animal model used (McGregor et al., 2008). Supporting the relevance of animal studies, a relationship has been reported between the effect of psychostimulants on social behaviour and the oxytocin levels in the rat hypothalamus (McGregor et al., 2008); oxytocin levels are also increased in humans who abuse MDMA at dancing parties (Wolff et al., 2006). DOI: 10.1097/FBP.0000000000000148
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
Social interaction and psychostimulants Šlamberová et al. 777
Social behaviour represents an integral part of the behavioural repertoire of rats that is essential for emotional wellbeing, healthy development, establishment and maintenance of adequate social structures and reproductive success (Trezza et al., 2011). There are different forms of SI that occur in different phases of an animal’s lifespan: affiliative behaviour, social play and sexual interaction have a high reward value (Trezza et al., 2011). A number of studies have reported that social behaviour is particularly sensitive to pharmacological influences (File and Seth, 2003; Varlinskaya and Spear, 2008; Mikulecká et al., 2014). In rodent and primate studies, psychostimulant drugs, such as amphetamine, cocaine and MDMA, have been shown to interfere with various social behaviours (Miczek and Tidey, 1989; Ando et al., 2006; Trezza et al., 2014). For example, amphetamines, more than any other psychostimulant drugs, elicit aggressive behaviour (Ellinwood et al., 1972; Miczek and Tidey, 1989). Methamphetamine (MA) and MDMA have been shown to decrease social behaviour, an effect that is associated with an anxiogenic effect and dopamine depletion (McGregor et al., 2003b; Clemens et al., 2004). In addition, another psychostimulant drug, cocaine, induces systemic effects that are similar to those of amphetamines (such as an increase of blood pressure, heart rate, feelings of ‘pleasantness’ and ‘stimulation’, and decreased feeling of hunger), but the duration of their action is much shorter (Resnick and Resnick, 1984). Acute cocaine administration suppresses affiliative behaviour and enhances defensive behaviour (Rademacher et al., 2002). In adolescent animals, social play had been shown to be suppressed by psychostimulants, such as amphetamine and cocaine (Holly et al., 2012; Achterberg et al., 2014; Baarendse et al., 2014). Our previous studies have shown that acute MA administration reduces SI in a dose-specific, stress-specific and hormone-specific manner (Šlamberová et al., 2010, 2011). Specifically, all doses of MA (0.5, 1.0 and 1.5 mg/kg) dosedependently decreased SI (Šlamberová et al., 2010). Further, the environmental conditions, such as familiarity with the experimental arena and intensity of light, influence both social and nonsocial activities (Šlamberová et al., 2010). While SI is decreased, locomotion and exploratory rearing are increased in an unfamiliar arena, suggesting a higher interest in the exploration of the unknown environment with lesser interest in the conspecific (Šlamberová et al., 2010). Thus, psychostimulant drugs, such as amphetamines and cocaine, markedly suppress social behaviour. However, the neural mechanisms underlying these effects remain to be elucidated (Achterberg et al., 2014). All the psychostimulants are known to activate monoamine systems in the brain – with differing preferences for noradrenalin, dopamine or serotonin (5-HT) (Iversen et al., 2014). Amphetamine affects mostly the noradrenergic, less the dopaminergic and minimally the serotoninergic systems. Cocaine mostly affects the dopaminergic and serotoninergic systems,
whereas MDMA predominantly affects the serotoninergic system (Rothman and Baumann, 2006; Iversen et al., 2014). A recent study showed that the suppressive effect of amphetamines on social behaviour might be mediated through α-2-noradrenergic receptors, whereas that of cocaine is because of simultaneous increases in dopamine, noradrenalin and serotonin neurotransmission (Achterberg et al., 2014). Repeated exposure of young rats to MDMA caused serotonin depletion and induced anxiety-like behaviour in the social interaction test (SIT) accompanied by a long-lasting reduction in specific 5-HT(2A)receptor-mediated behaviour (Bull et al., 2004). Another study indicated that MDMA could have a prosocial effect involving 5-HT 1A and 5-HT 2B/2C receptors, and in contrast, also an anxiogenic effect measured in the emergence test involving 5-HT 1A, 1B, 2A, 2B and 2C receptors (Morley et al., 2005). Although many studies have been published from the early 1970s (Tikal and Benešová, 1972; Syme and Syme, 1974; Kršiak, 1975) to date (Miczek et al., 2013; Achterberg et al., 2014; Trezza et al., 2014) showing the effects of various types of psychostimulants on different forms of social behaviour in rodents, the results of the studies are inconsistent. They involved different methodological procedures, different strains and animals of different ages. The objective of the present study was to compare the effects of three psychostimulant drugs (amphetamine, MDMA and cocaine) on social behaviour under identical conditions to integrate knowledge of the effects of psychostimulants on SI. As in our previous studies (Šlamberová et al., 2010, 2011), we used the method of File and Hyde (1978), which was validated for pharmacological studies. In addition to evaluating social behaviour in general, we also focused on specific patterns of the SI repertoire as well as the nonsocial behaviours locomotion and exploratory rearing.
Methods Subjects
In total, 246 adult male albino Wistar rats (8–10 pairs per group) were delivered by Anlab (Prague, the Czech Republic) from Charles River Laboratories International Inc. Animals were housed four per cage and left undisturbed for a week in a temperature-controlled (22–24°C) colony room with free access to food and water on a 12 h (light): 12 h (dark) cycle, with lights on at 06:00 h. Social interaction test
Animals were first habituated individually in an open field (45 × 45 × 30 cm) on 2 consecutive days in a dimly lit room for 10 min (File and Hyde, 1978). On the third day, a pair of unfamiliar animals of the same weight and treatment (each from a different cage) was tested for SI. The experiment was conducted under the same conditions as the habituation test. Drug (see below) or saline was injected subcutaneously 45 min before the SIT.
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
778 Behavioural Pharmacology 2015, Vol 26 No 8
The behaviour of each pair of animals was video recorded for 5 min. Subsequently, recordings were evaluated offline using ODLog software (Macropod Software). The frequency (number of occurrences) and the duration (time spent) in SI and nonsocial behaviours were evaluated. The measures analysed were as follows: (a) SI, which included the following patterns: sniffing (mutual), genital investigation (sniffing the anogenital area), following (the pursuit of one animal by another), climbing over and crawling under the partner, and allo-grooming; (b) nonsocial behaviours: locomotion (several steps in a forward direction) interrupted by other behavioural patterns, and rearing, expressed as vertical activity, irrespective of whether it occurred on or off the walls. Behaviour was recorded by typing pre-set keys on a computer keyboard. The ODLog software registered the number of presses and the time in seconds between presses. First, the number and the time spent in various social behaviours shown by each pair of rats were calculated. Then, the nonsocial behaviours were scored separately for each rat in a pair and summed to calculate the locomotion and exploration (rearing) for each pair. The experimenter trained himself until he could repeatedly score with at least 85% consistency between two analyses on the same pair of rats.
Particular patterns of social interaction
Drug treatment
Fig. 1
The effects of each drug (amphetamine, cocaine, MDMA) were analysed separately. Total SI was analysed first, followed by the particular patterns of social and nonsocial behaviours. One-way analysis of variance (drug treatment) with the Bonferroni post-hoc test was used to test the duration and number of each type of social and nonsocial behaviours. Differences were considered significant if P value was less than 0.05.
Results Amphetamine Total social interaction
As shown in Fig. 1, amphetamine decreased SI in a dosedependent manner [F(3, 28) = 27.86; P < 0.001]. All doses decreased SI relative to saline-treated rats, and the 1.0 and 1.5 mg/kg doses decreased SI relative to the 0.5 mg/ kg dose.
Allo-grooming: The duration [F(3, 28) = 9.61; P < 0.001] and the frequency [F(3, 28) = 15.34; P < 0.001] of allogrooming were decreased after the two higher doses of amphetamine (1.0 and 1.5 mg/kg) relative to salinetreated controls and to the lowest dose of amphetamine (0.05 mg/kg). Following: The duration [F(3, 28) = 8.61; P < 0.001] and the frequency [F(3, 28) = 7.58; P < 0.001] of following were decreased after the two higher doses of amphetamine (1.0 and 1.5 mg/kg) relative to saline-treated controls.
Duration (s)
120
Total Sl
Control AMP 0.5 AMP 1.0 AMP 1.5
∗
80 40
++ ∗∗∗
++ ∗∗∗
∗∗
∗∗
+ ∗∗∗
+ ∗∗∗
0 200 Duration (s)
Statistical analysis
Genital investigation: Because of a very low occurrence of genital investigation, this activity could not be analysed statistically.
Locomotion
160 120 80 40 0 160
Duration (s)
Amphetamine (0.5; 1.0; 1.5 mg/kg), cocaine (0.5; 1.0; 1.5; 2.5; 5.0; 10 mg/kg) or MDMA (2.5; 5.0; 10 mg/kg) was dissolved in distilled water and administered in a volume of 1 ml/kg. These doses were chosen on the basis of our preliminary data showing that these doses do not induce stereotyped behaviour. Saline (the same timing and injection volume) was administered to the control groups. The interval of 45 min was chosen on the basis of our published (Rambousek et al., 2014) and some unpublished pharmacokinetic data showing that brain concentrations of psychostimulants reach a peak between the 45th and the 60th minute after administration.
Mutual sniffing: The time spent in mutual sniffing was decreased after all doses of amphetamine [F(3, 28) = 18.49; P < 0.001]. The frequency of mutual sniffing [F(3, 28) = 11.68; P < 0.001] was decreased after the two higher doses of amphetamine (1.0 and 1.5 mg/kg) relative to both salinetreated controls and to rats treated with the lowest dose of amphetamine (0.05 mg/kg) (Table 1).
Rearing
120 80 40 0
Effect of amphetamine on the total time spent in social interaction. Values are mean ± SEM (n = 8 pairs). *P < 0.01, **P < 0.001, ***P < 0.0001 versus saline-treated control rats. +P < 0.05, + +P < 0.01 versus rats receiving the lowest dose of 0.5 mg/kg of amphetamine. AMP, amphetamine; SI, social interaction.
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
Social interaction and psychostimulants Šlamberová et al. 779
Effect of amphetamine on particular patterns of social interaction in adult male rats
Table 1
Social interaction pattern
Saline
Mutual sniffing Duration (s) 69.98 ± 6.7 Number 14.38 ± 1.6 Genital investigation Duration (s) LO Number LO Allo-grooming Duration (s) 9.99 ± 1.5 Number 2.38 ± 0.3 Following Duration (s) 23.31 ± 3.1 Number 6.25 ± 0.8 Climbing over Duration (s) 7.39 ± 2.3 Number 2.13 ± 0.8 Crawling under Duration (s) 0 Number 0
Amphetamine 0.5 mg/kg
Amphetamine 1.0 mg/kg
Amphetamine 1.5 mg/kg
34.56 ± 7.2** 10.86 ± 1.7
9.40 ± 6.6*** 3.63 ± 1.5***, +
8.80 ± 6.6*** 3.63 ± 1.5***, +
LO LO
LO LO
LO LO
4.37 ± 1.6 1.57 ± 0.3
0*** 0***, + +
0*** 0***, + +
14.58 ± 3.3 4.14 ± 0.9
6.44 ± 3.2* 2.25 ± 0.8*
2.58 ± 2.1** 0.88 ± 0.7**
8.59 ± 2.5 2.57 ± 0.8
3.42 ± 2.3 1.63 ± 0.7
0.52 ± 1.2 0.25 ± 0.7
0.36 ± 0.2 0.14 ± 0.1
Particular patterns of social interaction Mutual sniffing
The duration [F(6, 50) = 7.87; P < 0.001] and the frequency [F(6, 50) = 7.37; P < 0.001] of mutual sniffing were lowered by high doses of cocaine (2.5, 5.0, 10 mg/kg) relative to saline-treated controls (Table 2). Genital investigation
Low doses of cocaine (0.5, 1.0, 1.5 mg/kg) did not elicit genital investigation, which was significantly less than the duration [F(6, 50) = 2.92; P < 0.05] or the frequency [F(6, 50) = 2.94; P < 0.05] of genital investigation induced by 5.0 mg/kg of cocaine. Allo-grooming
0 0
0 0
Values are mean ± SEM (n = 8 pairs). LO, ‘low occurrence’ – this activity could not be statistically analysed because of a very low occurrence. *P < 0.01. **P < 0.001. ***P < 0.0001 versus saline-treated rats. + P < 0.05. ++ P < 0.01 versus rats treated with amphetamine 0.05 mg/kg.
The duration and frequency of allo-grooming were increased after the 1.5 mg/kg dose of cocaine, but frequency was decreased after higher doses (2.5; 5.0; 10 mg/kg) relative to saline-treated controls. In addition, the duration [F(6, 50) = 3.86; P < 0.01] and the frequency [F(6, 50) = 7.41; P < 0.001] of allo-grooming were lower after high doses of Fig. 2
Climbing over: There were no significant effects on the duration [F(3, 28) = 2.39; NS] or the frequency [F(3, 28) = 1.62; NS] of climbing over the other animal. Duration (s)
140 120 100 80 60 40 20 0
Duration (s)
Crawling under: There were no significant effects of amphetamine on the duration [F(3, 28) = 1.16; NS] or the frequency [F(3, 28) = 1.16; NS] of crawling under the other animal.
Total Sl
140 120 100 80 60 40 20 0
Particular patterns of nonsocial behaviour
Rearing: Animals administered 1.0 and 1.5 mg/kg spent more time in rearing [F(3, 28) = 16.17; P < 0.001] relative to saline-treated rats as well as rats receiving 0.5 mg/kg (Fig. 1), whereas only the highest dose of amphetamine (1.5 mg/kg) increased the frequency of rearing relative to saline-treated controls [F(3, 28) = 3.22; P < 0.05] (data not shown). Cocaine Total social interaction
As shown in Fig. 2, cocaine at higher doses (2.5, 5.0, 10 mg/kg) decreased total SI relative to saline [F(6, 50) = 8.19; P < 0.001] and relative to lower doses of cocaine (0.5, 1.0, 1.5 mg/kg).
150 Duration (s)
Locomotion: Animals administered 1.0 and 1.5 mg/kg amphetamine spent more time walking relative to salinetreated rats [F(3, 28) = 10.71; P < 0.001] (Fig. 1), whereas the frequency of acts of walking did not differ significantly between groups [F(3, 28) = 1.81; NS] (data not shown).
Control COC 0.5 COC 1.0 COC 1.5
COC 2.5 COC 5.0 COC 10
+ ∗
+ ∗
+ ∗
+ ∗∗
∗
∗∗
Locomotion
Rearing
100 50 0
Effect of cocaine on the total time spent in social interaction. Values are mean ± SEM (n = 8–9 pairs).*P < 0.01,**P < 0.001 versus saline-treated control rats. +P < 0.05 versus rats receiving the 1.5 mg/kg of cocaine. COC, cocaine; SI, social interaction.
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
780 Behavioural Pharmacology 2015, Vol 26 No 8
Table 2
Effect of cocaine on particular patterns of social interaction in adult male rats
Social interaction pattern Mutual sniffing Duration (s) Number Genital investigation Duration (s) Number Allo-grooming Duration (s) Number Following Duration (s) Number Climbing over Duration (s) Number Crawling under Duration (s) Number
Saline 69.98 ± 8.9 14.38 ± 1.5
Cocaine 0.5 mg/kg Cocaine 1.0 mg/kg Cocaine 1.5 mg/kg Cocaine 2.5 mg/kg Cocaine 5.0 mg/kg Cocaine 10 mg/kg 50.59 ± 8.8 9.5 ± 1.4
44.15 ± 7.8 8.50 ± 1.5
36.95 ± 7.6 8.38 ± 1.2
5.91 ± 3.48 0.89 ± 0.82
0 0
0 0
0 0
8.88 ± 4.1 2.11 ± 0.7
13.58 ± 5.5 2.88 ± 0.6
18.88 ± 5.3 2.74 ± 0.7
23.02 ± 5.6* 3.63 ± 0.8*
22.65 ± 7.0 6.22 ± 1.1
35.55 ± 6.8 7.88 ± 1.2
31.64 ± 6.9 7.00 ± 0.9
41.01 ± 6.8 9.13 ± 1.0
14.76 ± 7.5** 4.75 ± 1.4***
18.37 ± 6.8** 5.75 ± 1.5***
10.27 ± 3.6 2.25 ± 0.7
16.57 ± 3.5+ 3.75 ± 0.8+
0.22 ± 4.0+ 0.13 ± 0.5*, + 28.47 ± 6.5 7.13 ± 1.3
0.72 ± 4.2+ 0.13 ± 0.5*, + 26.64 ± 6.3 7.5 ± 1.2
15.61 ± 7.6** 4.00 ± 1.2*** 7.24 ± 3.3 2.38 ± 0.8 0.29 ± 4.3+ 0.13 ± 0.5*, + 23.64 ± 6.4 6.63 ± 1.1
7.51 ± 0.9 2.14 ± 0.4
2.85 ± 1.0* 0.88 ± 0.4*
2.32 ± 1.2* 0.5 ± 0.3*
1.39 ± 1.1* 0.38 ± 0.2*
0.22 ± 0.9** 0.13 ± 0.3**
0.21 ± 1.1** 0.13 ± 0.3**
0.18 ± 1.2** 0.13 ± 0.3**
LO LO
LO LO
LO LO
LO LO
LO LO
LO LO
LO LO
Values are mean ± SEM (n = 8–9 pairs). LO, ‘low occurrence’ – this activity could not be statistically analysed because of a very low occurrence. *P < 0.05. **P < 0.001. ***P < 0.001 versus saline-treated control rats. + P < 0.001 versus lower doses of cocaine (0.5; 1.0; 1.5 mg/kg).
cocaine (2.5, 5.0, 10 mg/kg) relative to lower doses of cocaine (0.5, 1.0, 1.5 mg/kg). Following
There were no significant differences in the duration [F(6, 50) = 1.08; NS] or the frequency [F(6, 50) = 0,55; NS] of following after cocaine treatment. Climbing over
The duration [F(6, 50) = 3.91; P < 0.01] and frequency [F(6, 50) = 3.56; P < 0.01] of climbing over were dosedependently lowered relative to saline-treated controls.
(Fig. 2). After high doses of cocaine (2.5, 5.0, 10 mg/kg), the frequency of rearing was increased [F(6, 50) = 16.67; P < 0.001] relative to saline-treated controls or to low doses of cocaine (0.5, 1.0, 1.5 mg/kg) (data not shown).
MDMA Total social interaction
As shown in Fig. 3, MDMA did not significantly alter total SI [F(3, 30) = 0.76; NS].
Particular patterns of social interaction Crawling under
Because of a very low occurrence of crawling under the other animal, this activity could not be analysed statistically. Particular patterns of nonsocial behaviour Locomotion
There were no significant differences in the duration of locomotion after cocaine treatment [F(6, 50) = 1.58; NS] (Fig. 2). The frequency of walking [F(6, 50) = 9.71; P < 0.001] was lower after the low doses of cocaine (0.5, 1.0, 1.5 mg/kg) relative to high doses (2.5, 5.0, 10 mg/kg), but no dose differed from saline-treated controls (data not shown). Rearing
As shown in Fig. 2, cocaine at higher doses (2.5, 5.0, 10 mg/kg) increased the time spent in rearing relative to saline-treated controls [F(6, 50) = 6.17; P < 0.001]. In addition, the duration of rearing was higher after the 2.5 mg/kg dose of cocaine in animals than after the 1.5 mg/kg dose
Mutual sniffing: All doses of MDMA decreased the duration [F(3, 30) = 12.60; P < 0.001] and the frequency [F(3, 30) = 31.59; P < 0.001] of mutual sniffing relative to saline-treated controls. In addition, the highest dose of MDMA (10 mg/kg) decreased the frequency of mutual sniffing compared with the lowest dose of MDMA (2.5 mg/kg) (Table 3). Genital investigation: Because of a very low occurrence of genital investigation, this activity could not be analysed statistically. Allo-grooming: The duration [F(3, 30) = 3.72; P < 0.05] and the frequency [F(3, 30) = 7.44; P < 0.001] of allogrooming were decreased after the two higher doses of MDMA (5.0 and 10 mg/kg) relative to the saline-treated control rats. Following: No doses of MDMA affected the duration of following [F(3, 30) = 2.45; NS], whereas the highest dose of MDMA (10 mg/kg) decreased the frequency of following [F(3, 30) = 4.24; P < 0.05] relative to saline control rats.
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
Social interaction and psychostimulants Šlamberová et al. 781
Fig. 3
Control MDMA 2.5 MDMA 5.0 MDMA 10
Total Sl
Duration (s)
160 120
Discussion
80 40
Duration (s)
0 420 360 300 240 180 120 60 0
++ ∗∗∗
Locomotion
+++ ∗∗∗
∗∗∗
Rearing
Duration (s)
200 160 120
[F(3, 30) = 3.97; P < 0.05]. The frequency of rearing (data not shown) was decreased after the two higher doses of MDMA (5.0 and 10 mg/kg) relative to the saline-treated controls or to the lowest dose of MDMA (2.5 mg/kg) [F(3, 30) = 15.52; P < 0.001].
+
80 40 0
Effect of MDMA on the total time spent in social interaction. Values are mean ± SEM (n = 8–10 pairs). ***P < 0.0001 versus saline-treated control rats. +P < 0.05, + +P < 0.001, + + +P < 0.0001 versus rats receiving the lowest dose of 2.5 mg/kg of MDMA. MDMA, 3,4 methylenedimethoxyamphetamine; SI, social interaction.
Climbing over: The duration [F(3, 30) = 4.11; P < 0.05] as well as the frequency [F(3, 30) = 5.00; P < 0.01] of climbing over the other animal were decreased after all the doses of MDMA. Crawling under: Because of a very low occurrence of crawling under the other animal, this activity could not be analysed statistically. Particular patterns of nonsocial behaviour
Locomotion: As shown in Fig. 3, all doses of MDMA increased the duration of locomotion [F(3, 30) = 47.19; P < 0.001] relative to saline-treated controls, and the highest doses of 5.0 and 10 mg/kg even increased the time spent in locomotion relative to the 2.5 mg/kg dose. The frequency of acts of walking (data not shown) was decreased in a dose-dependent manner [F(3, 30) = 16.07; P < 0.001]. Rearing: As shown in Fig. 3, the highest dose of MDMA (10 mg/kg) decreased the duration of rearing relative to the lowest dose (2.5 mg/kg), but not relative to salinetreated controls or rats treated with the 5.0 mg/kg dose
Numerous previous studies of the effects of psychostimulants on social behaviour have been carried out under nonidentical conditions (Ellinwood et al., 1972; Resnick and Resnick, 1984; Miczek and Tidey, 1989; Rademacher et al., 2002; McGregor et al., 2003b; Clemens et al., 2004; Trezza et al., 2014). Standardization of experimental conditions enables a detailed evaluation of the changes induced by different drugs. Moreover, the majority of the studies do not focus on the individual patterns of social behaviour that may be diversely affected by drug manipulation and the test environment. Therefore, the present study is distinctive in two ways. First, it compared the effect of three different psychostimulant drugs (amphetamine, cocaine and MDMA) on social behaviour under standard conditions. Second, in addition to providing an evaluation of social behaviour in general, the present study focused on specific elements of the SI repertoire as well as nonsocial behaviours. Table 4 summarizes our results, showing the differences in effects of the three psychostimulant drugs examined on the specific patterns of SI. All psychostimulant drugs resulted in decreased sociability, as a propensity to spent time with a conspecific, compared with time spent alone in the testing arena (Berton et al., 1997). The decrease in the total SI after the administration of amphetamine and cocaine is in agreement with our previous study showing a decrease in the total SI after MA exposure (Šlamberová et al., 2010) and other studies (McGregor et al., 2003a; Bull et al., 2004; Navarro et al., 2004; Clemens et al., 2007) showing a decrease in SI after MDMA. All the above-mentioned studies tested total SI only, without distinguishing between different social activities. In the present set of experiments, SI was divided into specific patterns of social behaviour, which were affected differently by the drugs under investigation (Table 4). Specifically, the present study has shown that mutual sniffing was decreased by all doses of amphetamine and MDMA and by the higher doses of cocaine and allogrooming was almost suppressed by higher doses of all three drugs. The following of one animal by another was decreased by higher doses of amphetamine and partially by the highest dose of MDMA, but was not affected by any dose of cocaine. Climbing over, in contrast, was decreased by all doses of cocaine and MDMA, with only a nonsignificant tendency toward suppression after amphetamine. In addition, genital investigation was measurable only in saline-treated animals and after higher doses of cocaine, with an increase in genital investigation after the dose of 5.0 mg/kg of cocaine was administered. Genital investigation may describe offensive aggression
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
782 Behavioural Pharmacology 2015, Vol 26 No 8
Table 3
Effect of MDMA on particular patterns of social interaction in adult male rats
Social interaction pattern Mutual sniffing Duration (s) Number Genital investigation Duration (s) Number Allo-grooming Duration (s) Number Following Duration (s) Number Climbing over Duration (s) Number Crawling under Duration (s) Number
Saline
MDMA 2.5 mg/kg
MDMA 5.0 mg/kg
MDMA 10 mg/kg
68.88 ± 6.5 13.70 ± 1.0
32.79 ± 7.3* 5.00 ± 1.1***
27.23 ± 7.2* 2.75 ± 1.0***
12.04 ± 6.8*** 0.50 ± 0.8***, +
LO LO
LO LO
LO LO
LO LO
0.65 ± 3.2** 0.13 ± 0.3**
0** 0**
15.34 ± 3.8 3.1 ± 0.5
12.27 ± 4.3 1.63 ± 0.6
24.02 ± 11.4 6.20 ± 0.7
54.86 ± 12.8 6.00 ± 0.8
51.36 ± 12.7 3.88 ± 0.6
5.86 ± 1.3 1.70 ± 0.4
0.65 ± 1.5* 0.13 ± 0.3*
0* 0*
0* 0*
LO LO
LO LO
LO LO
LO LO
68.56 ± 12.8 2.88 ± 0.7*
Values are mean ± SEM (n = 8–10 pairs). LO, ‘low occurrence’ – this activity could not be statistically analysed because of a very low occurrence; MDMA, 3,4 methylenedimethoxyamphetamine. *P < 0.05. **P < 0.01. ***P < 0.0001 versus saline-treated control rats. + P < 0.05 versus rats treated with 2.5 mg/kg of MDMA.
Table 4
General summary of the effects of psychostimulants on particular patterns of social interaction in adult male rats
Social interaction pattern Amphetamine Cocaine MDMA
Mutual sniffing
Genital investigation
Allo-grooming
Following
Climbing over
Crawling under
↓ ↓ ↓
LO – LO
↓ – ↓
↓ ↓ –
– – ↓
– LO LO
Table shows the general effect (independent of doses) of the psychostimulant drugs examined on the particular patterns of social interaction. ‘↓’, decrease in the activity induced by the psychostimulant drug; ‘–’, no effect of the psychostimulant drug on the activity; LO, ‘low occurrence’ – this activity could not be statistically analysed because of a very low occurrence; MDMA, 3,4 methylenedimethoxyamphetamine.
(Pellis, 1988); thus, this result is consistent with a proaggressive effect of cocaine at higher doses (Blanchard and Blanchard, 1999). However, in our experimental setting, we did not observe any other forms of aggressive behaviours such as boxing, aggressive fighting or biting attack. These forms of aggressive behaviour occur mostly in a resident-intruder test when resident rats express their territorial advantage in their environment. In the present study, the rats were familiarized with the testing arena for only a short period before testing; thus, there was no time to create a territorial dominance in the arena. In general, age-matched and weight-matched rats, as were used in the present study, do not usually express aggression and none of the drugs induced aggression per se. One of the main goals of the present study was to differentiate the effects of the psychostimulants examined on specific patterns of social behaviour. These differences may be explained by different effects on the neurotransmitters noradrenaline, dopamine and serotonin. In particular, amphetamine affects mostly the noradrenergic, less the dopaminergic and least the serotoninergic systems, whereas cocaine affects mostly the dopaminergic and serotoninergic systems (Fleckenstein et al., 2000; Rothman et al., 2001; Shoblock et al., 2003),
whereas MDMA affects predominantly the serotoninergic system, but also dopaminergic and noradrenergic systems (Yamamoto and Spanos, 1988; Bengel et al., 1998; Bankson and Cunningham, 2001; Cole and Sumnall, 2003). Thus, it seems that drugs that have greater effects on the serotonergic system (cocaine and MDMA) exerted greater effects on climbing, in comparison with amphetamine, which has a lesser effect on the serotonergic system. However, following was decreased by amphetamine and MDMA, but not cocaine, which corresponds with the effect of these drugs on the noradrenergic system. The neural network for social behaviours includes the amygdala and other limbic structures, the ventral hypothalamus, the prefrontal cortex, the preoptic area and the midbrain, and some of these structures interact with the drug reward circuit (Bachevalier and Loveland, 2006; Everitt et al., 2008; Siviy and Panksepp, 2011; Albers, 2012). One of the brain structures that seems to be involved in both the social behaviour neural network and the drug reward circuit is the striatum (Baez-Mendoza and Schultz, 2013). It has been hypothesized that activity in the striatum integrates actions, including social actions, with rewards (Baez-Mendoza and Schultz, 2013). Moreover,
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
Social interaction and psychostimulants Šlamberová et al. 783
social behaviour had been shown to involve several neurotransmitter systems, such as endogenous opioid and cannabinoid systems, as well as the dopaminergic noradrenergic and serotoninergic systems that are directly involved in the mechanisms of action of psychostimulant drugs (Panksepp et al., 1980; Niesink and Van Ree, 1989; Vanderschuren et al., 1997; Trezza et al., 2014). A question is whether the decreased SI could be interpreted as anxiety-like behaviour, as suggested by File and Hyde (1978), who proposed that the decrease in active SI under different environmental stress conditions could be considered anxiogenic behaviour, whereas an increase in active SI reflected an anxiolytic effect. The same conclusion was reached in our previous study (Šlamberová et al., 2010) showing that the administration of MA impairs SI in a dose-specific and stress conditionspecific manner suggestive of an anxiogenic effect. However, because another study indicated that acute administration of MA in adulthood exerts an anxiolyticlike effect in the elevated plus-maze (Schutová et al., 2010), we suggest being more careful about this conclusion. Moreover, various studies have reported contradictory findings, ranging from anxiolytic action, through no effect, to anxiogenic action (Miczek et al., 1989; Paine et al., 2002; Navarro et al., 2004; Hayase et al., 2005b). Such results suggest that SIT and nonsocial tests of anxiety probably measure different states of fear (File, 1991; Chaouloff et al., 1994). In addition, behavioural variability observed in rats in social and nonsocial environments is influenced by genetic factors as shown by the comparison of six inbred rat strains (Berton et al., 1997). As for nonsocial activities, the present data showed that amphetamine at higher doses (1.0 and 1.5 mg/kg) and all doses of MDMA increased locomotion, whereas exploratory rearing was increased after higher doses of amphetamine (1.0 and 1.5 mg/kg) and cocaine (2.5, 5.0 and 10 mg/kg). This type of response is considered to reflect not only exploratory activity but also emotionality (Lever et al., 2006). In contrast to these findings, the highest dose of MDMA (10 mg/kg) decreased rearing relative to the lowest dose of MDMA (2.5 mg/kg). Our finding that MDMA increased locomotion is in agreement with our earlier observation that 5.0 mg/kg MDMA increased locomotion when animals were tested in their home cages and behaviour was evaluated by an automated system (Šlamberová et al., 2013). That study also reported that cocaine at 5.0 mg/kg increased the exploratory rearing, whereas the dose of 5.0 mg/kg of MDMA did not affect rearing, again in agreement with the present results. Similarly, results have been reported in other studies: for example, Bull et al. (2004) reported that MDMA (5.0 mg/kg) increased the locomotion, but did not alter the rearing activity, and amphetamine has frequently been shown to increase locomotor activity (e.g. Melnick and Dow-Edwards, 2001; Bisagno et al., 2003). Thus, it seems that the effect of psychostimulants
on locomotor and exploratory (rearing) behaviour is drug and dose specific. Because it is known that psychostimulants at high doses increase locomotion and stereotypies (Tzschentke and Schmidt, 1998; Broderick et al., 2003), in the present study, we used lower doses that do not induce any stereotypical behaviours that might affect performance in the SIT. Taken together, our results show that psychostimulant-treated animals preferred nonsocial activities to SI, suggesting that these drugs alter decrease in motivation to interact socially. The drugs did not induce stereotyped behaviour, the repetition of seemingly purposeless acts such as gnawing or sniffing in a restricted location (Evenden and Ryan, 1988); thus, we assume that the reduced expression of social investigation is not secondary to stereotyped behaviour. It should be noted that the increase in locomotor and exploratory (rearing) behaviour may secondarily alter the SI. It is therefore possible that some decreases in SI may be because of increases in locomotion especially after the higher doses of amphetamine or cocaine. However, even though low doses of psychostimulants caused no increase in the locomotion or exploration, they decreased some specific patterns of SI; thus, the mutual influence seems to be only partial. Nevertheless, it is difficult to determine whether these are two independent effects or whether the decrease in SI was the result of response competition. For example, in the study of File and Hyde (1978), amphetamine decreased the time spent in SI but also increased locomotion, whereas Sams-Dodd (1998) observed increased locomotion with slightly decreased or no effect on social behaviour. In addition, factor analysis has shown that locomotion is a component of social behaviour in this test, and the measures can covary to an extent, such that walking is not entirely independent of anxiety (Lapiz-Bluhm et al., 2008). The methodology may also have an important influence on the data analysis. We gave preference to manual analysis by an experienced observer over an automated analysis because an experienced observer can better distinguish between the specific patterns of the SI repertoire, whereas an automated system cannot, and the evaluation of specific patterns of SI was one of the main goals of the present study. Locomotion and exploratory rearing were analysed as in the duration and frequency of the activity rather than the distance travelled (as in an automated system) or the number of squares crossed. Manual and automated methods each have their pros and cons. The limitation of the method used in the present study is that it does not show the distance travelled, which might provide a better measure of hyperactivity induced by the psychostimulant drugs. Nevertheless, we assume that the evaluation of locomotion by a videotracking system and the ethological approach that was used in the present study would yield highly similar results. Future studies are needed to address this issue.
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
784 Behavioural Pharmacology 2015, Vol 26 No 8
In conclusion, these findings extend the knowledge of psychostimulant effects on social behaviour. SI was decreased even by drugs, such as MDMA, known as socializing party drugs. We also show that not only overall social activity per se is affected but also specific patterns of SI compared with the effects of different drugs under standard conditions. Moreover, we show that after higher doses of amphetamine and cocaine, the animals prefer nonsocial exploratory activities rather than engagement in the investigation of a conspecific, suggesting deficit in the levels of emotionality and hyperactivity/hyperarousal. A variety of neuropsychiatric disorders are characterized by inappropriate or altered social behaviour and social cognition, including depression, autism spectrum disorders, bipolar disorders, obsessive-compulsive disorders and schizophrenia (Blumstein et al., 2010). The present study also adds a new dimension to this field of psychiatric research.
Acknowledgements This study was supported by grant 14-03708S from the Grant Agency of the Czech Republic, project #PRVOUK P34 and project #260168/SVV/2015 from Charles University in Prague and project #NT/14484 from the Internal Grant Agency of Ministry of Health of the Czech Republic. The procedures for animal experimentation utilized in this report was reviewed and approved by the Institutional Animal Care and Use Committee and are in agreement with the Czech Government Requirements under the Policy of Humans Care of Laboratory Animals (No. 246/1992) and with the regulations of the Ministry of Agriculture of the Czech Republic (No. 311/1997). Conflicts of interest
There are no conflicts of interest.
References Achterberg EJ, Trezza V, Siviy SM, Schrama L, Schoffelmeer AN, Vanderschuren LJ (2014). Amphetamine and cocaine suppress social play behavior in rats through distinct mechanisms. Psychopharmacology (Berl) 231:1503–1515. Albers HE (2012). The regulation of social recognition, social communication and aggression: vasopressin in the social behavior neural network. Horm Behav 61:283–292. Ando RD, Benko A, Ferrington L, Kirilly E, Kelly PA, Bagdy G (2006). Partial lesion of the serotonergic system by a single dose of MDMA results in behavioural disinhibition and enhances acute MDMA-induced social behaviour on the social interaction test. Neuropharmacology 50:884–896. Baarendse PJ, Limpens JH, Vanderschuren LJ (2014). Disrupted social development enhances the motivation for cocaine in rats. Psychopharmacology (Berl) 231:1695–1704. Bachevalier J, Loveland KA (2006). The orbitofrontal-amygdala circuit and selfregulation of social-emotional behavior in autism. Neurosci Biobehav Rev 30:97–117. Baez-Mendoza R, Schultz W (2013). The role of the striatum in social behavior. Front Neurosci 7:233. Bankson MG, Cunningham KA (2001). 3,4-Methylenedioxymethamphetamine (MDMA) as a unique model of serotonin receptor function and serotonindopamine interactions. J Pharmacol Exp Ther 297:846–852. Bengel D, Murphy DL, Andrews AM, Wichems CH, Feltner D, Heils A, et al. (1998). Altered brain serotonin homeostasis and locomotor insensitivity to 3, 4-methylenedioxymethamphetamine (‘Ecstasy’) in serotonin transporterdeficient mice. Mol Pharmacol 53:649–655.
Berton O, Ramos A, Chaouloff F, Mormde P (1997). Behavioral reactivity to social and nonsocial stimulations: a multivariate analysis of six inbred rat strains. Behav Genet 27:155–166. Bisagno V, Ferguson D, Luine VN (2003). Chronic D-amphetamine induces sexually dimorphic effects on locomotion, recognition memory, and brain monoamines. Pharmacol Biochem Behav 74:859–867. Blanchard DC, Blanchard RJ (1999). Cocaine potentiates defensive behaviors related to fear and anxiety. Neurosci Biobehav Rev 23:981–991. Blumstein DT, Ebensperger LA, Hayes LD, Vasquez RA, Ahern TH, Burger JR, et al. (2010). Toward an integrative understanding of social behavior: new models and new opportunities. Front Behav Neurosci 4:34. Broderick PA, Rahni DN, Zhou Y (2003). Acute and subacute effects of risperidone and cocaine on accumbens dopamine and serotonin release using in vivo microvoltammetry on line with open-field behavior. Prog Neuropsychopharmacol Biol Psychiatry 27:1037–1054. Bull EJ, Hutson PH, Fone KC (2004). Decreased social behaviour following 3,4-methylenedioxymethamphetamine (MDMA) is accompanied by changes in 5-HT2A receptor responsivity. Neuropharmacology 46:202–210. Chaouloff F, Castanon N, Mormede P (1994). Paradoxical differences in animal models of anxiety among the Roman rat lines. Neurosci Lett 182:217–221. Clemens KJ, Van Nieuwenhuyzen PS, Li KM, Cornish JL, Hunt GE, McGregor IS (2004). MDMA (‘ecstasy’), methamphetamine and their combination: longterm changes in social interaction and neurochemistry in the rat. Psychopharmacology (Berl) 173:318–325. Clemens KJ, Cornish JL, Hunt GE, McGregor IS (2007). Repeated weekly exposure to MDMA, methamphetamine or their combination: long-term behavioural and neurochemical effects in rats. Drug Alcohol Depend 86:183–190. Cole JC, Sumnall HR (2003). The pre-clinical behavioural pharmacology of 3,4-methylenedioxymethamphetamine (MDMA). Neurosci Biobehav Rev 27:199–217. Daza-Losada M, Rodriguez-Arias M, Maldonado C, Aguilar MA, Guerri C, Minarro J (2009). Acute behavioural and neurotoxic effects of MDMA plus cocaine in adolescent mice. Neurotoxicol Teratol 31:49–59. Ellinwood EH Jr, Sudilovsky A, Nelson L (1972). Behavioral analysis of chronic amphetamine intoxication. Biol Psychiatry 4:215–230. Evenden JL, Ryan CN (1988). Behavioral responses to psychomotor stimulant drugs: localization in the central nervous system. Pharmacol Ther 36:151–172. Everitt BJ, Belin D, Economidou D, Pelloux Y, Dalley JW, Robbins TW (2008). Review. Neural mechanisms underlying the vulnerability to develop compulsive drug-seeking habits and addiction. Philos Trans R Soc Lond B Biol Sci 363:3125–3135. File SE (1991). The biological basis of anxiety. In: Meltzer HY, Nerozzi D, editors. Current practices and future developments in the pharmacotherapy of mental disorders. Amsterdam: Elsevier. pp. 159–165. File SE, Hyde JR (1978). Can social interaction be used to measure anxiety? Br J Pharmacol 62:19–24. File SE, Seth P (2003). A review of 25 years of the social interaction test. Eur J Pharmacol 463:35–53. Fleckenstein AE, Gibb JW, Hanson GR (2000). Differential effects of stimulants on monoaminergic transporters: pharmacological consequences and implications for neurotoxicity. Eur J Pharmacol 406:1–13. Hayase T, Yamamoto Y, Yamamoto K (2005). Persistent anxiogenic effects of a single or repeated doses of cocaine and methamphetamine: interactions with endogenous cannabinoid receptor ligands. Behav Pharmacol 16:395–404. Holly EN, Shimamoto A, Debold JF, Miczek KA (2012). Sex differences in behavioral and neural cross-sensitization and escalated cocaine taking as a result of episodic social defeat stress in rats. Psychopharmacology (Berl) 224:179–188. Homberg JR, Schiepers OJ, Schoffelmeer AN, Cuppen E, Vanderschuren LJ (2007). Acute and constitutive increases in central serotonin levels reduce social play behaviour in peri-adolescent rats. Psychopharmacology (Berl) 195:175–182. Iversen L, White M, Treble R (2014). Designer psychostimulants: pharmacology and differences. Neuropharmacology 87:59–65. Krsiak M (1975). Timid singly-housed mice: their value in prediction of psychotropic activity of drugs. Br J Pharmacol 55:141–150. Lapiz-Bluhm MD, Bondi CO, Doyen J, Rodriguez GA, Bedard-Arana T, Morilak DA (2008). Behavioural assays to model cognitive and affective dimensions of depression and anxiety in rats. J Neuroendocrinol 20:1115–1137. Lever C, Burton S, O’Keefe J (2006). Rearing on hind legs, environmental novelty, and the hippocampal formation. Rev Neurosci 17:111–133. Maldonado E, Navarro JF (2001). MDMA (‘ecstasy’) exhibits an anxiogenic-like activity in social encounters between male mice. Pharmacol Res 44:27–31.
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
Social interaction and psychostimulants Šlamberová et al. 785
McGregor IS, Clemens KJ, Van der Plasse G, Li KM, Hunt GE, Chen F, Lawrence AJ (2003a). Increased anxiety 3 months after brief exposure to MDMA (‘Ecstasy’) in rats: association with altered 5-HT transporter and receptor density. Neuropsychopharmacology 28:1472–1484. McGregor IS, Gurtman CG, Morley KC, Clemens KJ, Blokland A, Li KM, et al. (2003b). Increased anxiety and ‘depressive’ symptoms months after MDMA (‘ecstasy’) in rats: drug-induced hyperthermia does not predict long-term outcomes. Psychopharmacology (Berl) 168:465–474. McGregor IS, Callaghan PD, Hunt GE (2008). From ultrasocial to antisocial: a role for oxytocin in the acute reinforcing effects and long-term adverse consequences of drug use? Br J Pharmacol 154:358–368. Melnick SM, Dow-Edwards DL (2001). Differential behavioral responses to chronic amphetamine in adult male and female rats exposed to postnatal cocaine treatment. Pharmacol Biochem Behav 69:219–224. Miczek KA, Tidey JW (1989). Amphetamines: aggressive and social behavior. NIDA Res Monogr 94:68–100. Miczek KA, Haney M, Tidey J, Vatne T, Weerts E, DeBold JF (1989). Temporal and sequential patterns of agonistic behavior: effects of alcohol, anxiolytics and psychomotor stimulants. Psychopharmacology (Berl) 97:149–151. Miczek KA, de Boer SF, Haller J (2013). Excessive aggression as model of violence: a critical evaluation of current preclinical methods. Psychopharmacology (Berl) 226:445–458. Mikulecká A, Šubrt M, Pařízková M, Mareš P, Kubová H (2014). Consequences of early postnatal benzodiazepines exposure in rats. II. Social behavior. Front Behav Neurosci 8:169. Morley KC, McGregor IS (2000). (+ / − )-3,4-methylenedioxymethamphetamine (MDMA,‘Ecstasy’) increases social interaction in rats. Eur J Pharmacol 408:41–49. Morley KC, Arnold JC, McGregor IS (2005). Serotonin (1A) receptor involvement in acute 3,4-methylenedioxymethamphetamine (MDMA) facilitation of social interaction in the rat. Prog Neuropsychopharmacol Biol Psychiatry 29:648–657. Navarro JF, Maldonado E (1999). Behavioral profile of 3,4-methylenedioxymethamphetamine (MDMA) in agonistic encounters between male mice. Prog Neuropsychopharmacol Biol Psychiatry 23:327–334. Navarro JF, Rivera A, Maldonado E, Cavas M, de la Calle A (2004). Anxiogenic-like activity of 3,4-methylenedioxy-methamphetamine (‘Ecstasy’) in the social interaction test is accompanied by an increase of c-fos expression in mice amygdala. Prog Neuropsychopharmacol Biol Psychiatry 28:249–254. Niesink RJ, Van Ree JM (1989). Involvement of opioid and dopaminergic systems in isolation-induced pinning and social grooming of young rats. Neuropharmacology 28:411–418. Paine TA, Jackman SL, Olmstead MC (2002). Cocaine-induced anxiety: alleviation by diazepam, but not buspirone, dimenhydrinate or diphenhydramine. Behav Pharmacol 13:511–523. Palenicek T, Votava M, Bubenikova V, Horacek J (2005). Increased sensitivity to the acute effects of MDMA (‘ecstasy’) in female rats. Physiol Behav 86:546–553. Panksepp J, Herman BH, Vilberg T, Bishop P, DeEskinazi FG (1980). Endogenous opioids and social behavior. Neurosci Biobehav Rev 4:473–487. Pellis SM (1988). Agonistic versus amicable targets of attack and defense: consequences for the origin, function, and descriptive classification of playfighting. Aggr Behav 14:85–104. Rademacher DJ, Schuyler AL, Kruschel CK, Steinpreis RE (2002). Effects of cocaine and putative atypical antipsychotics on rat social behavior: an ethopharmacological study. Pharmacol Biochem Behav 73:769–778. Rambousek L, Kacer P, Syslova K, Bumba J, Bubenikova-Valesova V, Slamberova R (2014). Sex differences in methamphetamine pharmacokinetics in adult rats and its transfer to pups through the placental membrane and breast milk. Drug Alcohol Depend 139:138–144. Resnick RB, Resnick EB (1984). Cocaine abuse and its treatment. Psychiatr Clin North Am 7:713–728. Rothman RB, Baumann MH (2006). Balance between dopamine and serotonin release modulates behavioral effects of amphetamine-type drugs. Ann N Y Acad Sci 1074:245–260.
Rothman RB, Baumann MH, Dersch CM, Romero DV, Rice KC, Carroll FI, Partilla JS (2001). Amphetamine-type central nervous system stimulants release norepinephrine more potently than they release dopamine and serotonin. Synapse 39:32–41. Sams-Dodd F (1998). Effects of continuous D-amphetamine and phencyclidine administration on social behaviour, stereotyped behaviour, and locomotor activity in rats. Neuropsychopharmacology 19:18–25. Schutová B, Hrubá L, Pometlová M, Deykun K, Šlamberová R (2009). Cognitive functions and drug sensitivity in adult male rats prenatally exposed to methamphetamine. Physiol Res 58:741–750. Schutová B, Hrubá L, Pometlová M, Rokyta R, Šlamberová R (2010). Responsiveness to methamphetamine in adulthood is altered by prenatal exposure in rats. Physiol Behav 99:381–387. Shoblock JR, Sullivan EB, Maisonneuve IM, Glick SD (2003). Neurochemical and behavioral differences between D-methamphetamine and D-amphetamine in rats. Psychopharmacology (Berl) 165:359–369. Siviy SM, Panksepp J (2011). In search of the neurobiological substrates for social playfulness in mammalian brains. Neurosci Biobehav Rev 35:1821–1830. Šlamberová R, Mikulecká A, Pometlová M, Schutová B, Hrubá L, Deykun K (2010). The effect of methamphetamine on social interaction of adult male rats. Behav Brain Res 214:423–427. Šlamberová R, Mikulecká A, Pometlová M, Schutová B, Hrubá L, Deykun K (2011). Sex differences in social interaction of methamphetamine-treated rats. Behav Pharmacol 22:617–623. Šlamberová R, Macúchová E, Nohejlová-Deykun K, Schutová B, Hrubá L, Rokyta R (2013). Gender differences in the effect of prenatal methamphetamine exposure and challenge dose of other drugs on behavior of adult rats. Physiol Res 62:S99–S108. Sommers I, Baskin D, Baskin-Sommers A (2006). Methamphetamine use among young adults: health and social consequences. Addict Behav 31:1469–1476. Syme LA, Syme GJ (1974). Group instability and the social response to methamphetamine. Pharmacol Biochem Behav 2:851–854. Thompson MR, Callaghan PD, Hunt GE, Cornish JL, McGregor IS (2007). A role for oxytocin and 5-HT(1A) receptors in the prosocial effects of 3,4 methylenedioxymethamphetamine (‘ecstasy’). Neuroscience 146:509–514. Thompson VB, Heiman J, Chambers JB, Benoit SC, Buesing WR, Norman MK, et al. (2009). Long-term behavioral consequences of prenatal MDMA exposure. Physiol Behav 96:593–601. Tikal K, Benešová O (1972). The effect of some psychotropic drugs on contact behavior in a group. Act Nerv Super (Praha) 14:168–169. Trezza V, Campolongo P, Vanderschuren LJ (2011). Evaluating the rewarding nature of social interactions in laboratory animals. Dev Cogn Neurosci 1:444–458. Trezza V, Baarendse PJ, Vanderschuren LJ (2014). On the interaction between drugs of abuse and adolescent social behavior. Psychopharmacology (Berl) 231:1715–1729. Tzschentke TM, Schmidt WJ (1998). The development of cocaine-induced behavioral sensitization is affected by discrete quinolinic acid lesions of the prelimbic medial prefrontal cortex. Brain Res 795:71–76. Vanderschuren LJ, Niesink RJ, Van Ree JM (1997). The neurobiology of social play behavior in rats. Neurosci Biobehav Rev 21:309–326. Varlinskaya EI, Spear LP (2008). Social interactions in adolescent and adult Sprague–Dawley rats: impact of social deprivation and test context familiarity. Behav Brain Res 188:398–405. Williams MT, Moran MS, Vorhees CV (2003). Refining the critical period for methamphetamine-induced spatial deficits in the Morris water maze. Psychopharmacology (Berl) 168:329–338. Wolff K, Tsapakis EM, Winstock AR, Hartley D, Holt D, Forsling ML, Aitchison KJ (2006). Vasopressin and oxytocin secretion in response to the consumption of ecstasy in a clubbing population. J Psychopharmacol 20:400–410. Yamamoto BK, Spanos LJ (1988). The acute effects of methylenedioxymethamphetamine on dopamine release in the awake-behaving rat. Eur J Pharmacol 148:195–203. Zernig G, Kummer KK, Prast JM (2013). Dyadic social interaction as an alternative reward to cocaine. Front Psychiatry 4:100.
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
