Psychopharmacology (1992) 109:390-394
Psychopharmacology © Springer-Verlag 1992
Control of turning behavior under apomorphine by sensory input from the face Heinz Steiner 1 and Joseph P. Huston 2 1 Laboratory of Cell Biology, National Institute of Mental Health, Building 36, Room 2D 10, Bethesda, MD 20892, USA 2 Institute of Physiological Psychology I, University of Duesseldorf, Universitaetsstrasse 1, W-4000 Duesseldorf, Federal Republic of Germany Received October 30, 1991 / Final version July 17, 1992
Abstract. It has been shown that peripheral manipulation of sensory input by removal o f vibrissae on one side o f the rat's face induces turning behavior which is directed towards the contralateral vibrissae-intact side, under the influence of the dopamine receptor agonist a p o m o r phine, In the present experiment, we examined whether rats under a p o m o r p h i n e turn towards the side with m o r e sensory input, or simply away f r o m the manipulated side. Thus, an experimental manipulation was designed to increase sensory input. Sensory stimulation was applied by attaching a clip into the fur on one side of the face. Rats injected with apomorphine in doses of 0.5-5.0 mg/kg (but not with 0.05 mg/kg or vehicle) exhibited turning behavior towards the side of the clip. This sensory stimulation was also found to influence spontaneous behavioral asymmetries. These results show that an imbalance in sensory input is sufficient to produce turning under apomorphine.
side. Both manipulations are thought to create a sensory imbalance by reducing sensory input f r o m one side, and it is assumed that the rats turn towards the side with more sensory input. These results are consistent with the hypothesis that turning in apomorphine-treated rats is, in part, related to lateralized responsiveness to sensory stimuli (Huston et al. 1980). In the above mentioned studies, however, the possibility that turning was merely directed away f r o m the experimentally manipulated side (i.e., towards the intact side), rather than towards greater sensory input, was not ruled out. In the present study, we addressed this question by examining whether or not an experimental manipulation designed to increase sensory stimulation would lead to turning towards the stimulated side. Sensory stimulation was applied by attaching a plastic clip into the fur on one side of the rat's face. The results show that this is sufficient to induce turning behavior.
Key words: A p o m o r p h i n e - Turning b e h a v i o r - Sensory imbalance - Sensory responsiveness - D o p a m i n e
Materials and methods
Dopaminergic systems modulate the behavioral response of animals to sensory stimuli. It is well established that lateralized dopaminergic activity in the striatum results in sensorimotor asymmetries. F o r example, turning behavior is observed under the influence of the dopamine receptor agonist apomorphine, either when injected into one striatum in normal rats, or when given systemically after a unilateral 6 - O H D A lesion o f the nigrostriatal projection (Pycock t980, for review). However, turning behavior under the influence of a p o m o r p h i n e is also produced by peripheral manipulation of sensory input. It has been shown that bandaging one side of the rat's face (Szechtman 1983) or simply cutting the vibrissae on one side (Milani et al. 1990; Schwarting et al. 1990, 1991) both induce turning towards the sensory intact (opposite) Correspondence to: H. Steiner
Subjects. Forty male Wistar rats of 180-230 g were housed in groups of four to nine animals under standard laboratory conditions. They had free access to food and tap water and were maintained under a 12 h light-dark cycle (lights on at 7 a.m.). Prior to the experiment the rats were handled for several days. Behavioral testing. Rats were tested in an open field monitored by a video system, which was designed for automated measurement of turning behavior (Bonatz et aL 1987). In short, the testing apparatus consisted of a black wooden chamber (60 x 60 × 40 cm) with a video camera positioned above the center of the chamber. The video image was recorded on tape and, in parallel, fed into a video interface (digitizer) of a microcomputer, thus allowing image analysis of the rat's behavior. The following parameters were assessed: the number of quarter, half and full turns (i.e., two and four consecutive quarter turns, respectively) to the left and to the right, in diameter (d) categories of d < 20, < 30, 20-30, 30-55, > 55 cm. In addition, the distance the rat traversed was measured (in meters). The analysis of behavior started 10 s after the animal was placed near the center of the open field. Testing was carried out under dim red light. Immediately before the rat was transferred to the open field, it received an injection of
391 apomorphine (or vehicle). Five minutes after the drug application, the rat was removed from the field and reintroduced. Then, the rat's behavior was recorded for a 5-min period. This baseline session was followed by four 5-rain test sessions during which the rat carried a plastic clip in the fur on one side of the face. The rat was removed from the open field, and the clip was gently placed into the fur about 1 can under the ear on one side. The plastic clip had a weight of 1.2 g and a length of 2.9 cm. In the first test session, half of the rats had the clip attached on the right side, the other half on the left. In subsequent sessions, the side with the clip was always reversed.
L 2O
10
I-"
10
Drugs. Apomorphine [apomorphine hydrochloride (APO); Woelm Pharma, Eschwege, FRG] was dissolved in saline containing 0.1% ascorbic acid on the day of testing. The rats were randomly assigned to one of five groups, and these received one of the following doses: 0.00 (vehicle), 0.05 (APO-0.05), 0.5 (APO4).5), 1.0 (APO-1), 5.0 (APO-5) mg/kg (n = 8 each). The drug was injected subcutaneously (in the neck) in a volume of 1 ml/kg.
Statistical analysis. Turns towards the side of the clip and towards the opposite side were compared with the Wilcoxon matched-pairs test. Between-group comparisons for turning and locomotion data were done with the Kruskal-Walfis test, followed by post hoc comparisons of individual groups with the Dunn Procedure (Rosner 1986). All P values are given two-tailed.
20 R
abcd B
abed
abed
1
obcd
2
abed
3
4
TEST SESSIONS
Fig. 1. Illustration of turning behavior under the influence of the clip in an individual animal. The numbers of half turns to the left (L) and to the right (R) in diameter categories of < 20 (a), 20~30 (b), 30-55 (c) and > 55 cm (d) are given. The animal received an injection of 1.0 mg/kg of apomorphine. In the baseline session (B; from 5 min to 10 min after the injection), the rat's behavior without clip was assessed. During the following four 5-rain test sessions, the rat carried a clip in the fur under the ear, either on the right side (sessions 1 and 3; side with clip indicated by solid bars) or on the left side (sessions 2 and 4)
Results
General observations Overall, the clip was well tolerated by m o s t of the animals. A few times, rats of the vehicle and APO-0.05 groups removed the clip with the forepaw shortly after they were placed in the open field. In such cases, it was attached again, and the trial was restarted. Rats injected with vehicle mostly m o v e d around the field during the first part o f the session. After this initial l o c o m o t o r activity, they often showed grooming behavior, and some thereby removed the clip with washing movements. In most cases, there was little or no locomotion afterwards. G r o o m i n g was sometimes also observed in APO-0.05 animals (which generally showed little l o c o m o t o r activity). However, it was m o r e directed towards ventral aspects o f the body. Nevertheless, occasionally grooming caused loss o f the clip. In contrast, in animals injected with higher doses o f a p o m o r p h i n e (0.5-5 mg/kg), grooming was never observed, neither were washing movements directed towards the clip. These rats showed well k n o w n a p o m o r p h i n e stereotypies, such as continuous snout contact with surthces (Szechtman et al. 1982; Beck et al. 1986), sniffing, whisking and sometimes licking and gnawing. F o r w a r d progression varied substantially between animals (see below). A few times the clip was lost through the course o f the session, especially when rats m o v e d very fast. However, attempts to remove the clip were not seen in these animals. (This contrasts with findings in pilot studies, in which clips were also attached to vibrissae. In rats injected with higher a p o m o r p h i n e doses, as well as in vehicle rats, clips were removed f r o m vibrissae immediately and vigorously. Similarly, clips were removed instantly and vigorously when placed into the fur and, by accident, also pinched skin.)
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O,5
1.0
5.0
0,5-5.0
I00
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V "1~ 60 CO Z rv1-20
0.00
0.05
APOMORPHINE (mg/kg)
Fig. 2. The number (mean + SEM) of quarter turns with a diameter of less than 30 cm towards the side with clip (soh:d bars) and towards the side without clip (open bars) during 20 min of testing (4 test sessions pooled). Rats were injected with the following doses of apomorphine: 0.00 (vehicle), 0.05, 0.5, 1.0 and 5.0 mg/kg (n= 8 each). The data of rats with apomorphine doses of 0.5--5.0 mg/kg are also given pooled. *P< 0.05, **P< 0.001; Wilcoxon matchedpairs test, two-tailed
Clip-induced turning behavior Attaching the clip to the fur on one side of the face directed turning behavior in rats injected with a p o m o r phinc in doses o f 0.5-5 mg/kg; 23 out of 24 o f these animals showed more turns towards the side o f the clip than towards the opposite side. An example of an individual turning profile is depicted in Fig. 1. Turning asymmetries under the influence of the clip were most clearly observable in small-diameter turning categories. Figure 2 shows the total n u m b e r of quarter turns with a diameter of less than 30 cm throughout the four test sessions (20 min). Eight out of eight rats injected with
392
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10
B
1
2
3
4 0.5-5.0 0.05
* 20
20
-z-
10
I0
2
g
1
2
3
4
.
g
1
2
3
4
TEST SESSIONS
Fig. 3. The number (mean+ SEM) of quarter turns with a diameter of less than 30 cm towards the side with clip (solid bars) and towards the side without clip (open bars), during the baseline session (B) (withoutclip) and during 4 test sessions. These data are given for rats injected with vehicle (0.00, upper left), 0.05 mg/kg apomorphine (lower left) or 0.5-5.0 mg/kg apomorphine (lower right). *P0.05; but APO-0.5-5 pooled: P < 0.05). However, all three groups with higher apomorphine doses expressed more quarter turns towards both sides than the APO-0.05 group (P
Psychopharmacology © Springer-Verlag 1992
Control of turning behavior under apomorphine by sensory input from the face Heinz Steiner 1 and Joseph P. Huston 2 1 Laboratory of Cell Biology, National Institute of Mental Health, Building 36, Room 2D 10, Bethesda, MD 20892, USA 2 Institute of Physiological Psychology I, University of Duesseldorf, Universitaetsstrasse 1, W-4000 Duesseldorf, Federal Republic of Germany Received October 30, 1991 / Final version July 17, 1992
Abstract. It has been shown that peripheral manipulation of sensory input by removal o f vibrissae on one side o f the rat's face induces turning behavior which is directed towards the contralateral vibrissae-intact side, under the influence of the dopamine receptor agonist a p o m o r phine, In the present experiment, we examined whether rats under a p o m o r p h i n e turn towards the side with m o r e sensory input, or simply away f r o m the manipulated side. Thus, an experimental manipulation was designed to increase sensory input. Sensory stimulation was applied by attaching a clip into the fur on one side of the face. Rats injected with apomorphine in doses of 0.5-5.0 mg/kg (but not with 0.05 mg/kg or vehicle) exhibited turning behavior towards the side of the clip. This sensory stimulation was also found to influence spontaneous behavioral asymmetries. These results show that an imbalance in sensory input is sufficient to produce turning under apomorphine.
side. Both manipulations are thought to create a sensory imbalance by reducing sensory input f r o m one side, and it is assumed that the rats turn towards the side with more sensory input. These results are consistent with the hypothesis that turning in apomorphine-treated rats is, in part, related to lateralized responsiveness to sensory stimuli (Huston et al. 1980). In the above mentioned studies, however, the possibility that turning was merely directed away f r o m the experimentally manipulated side (i.e., towards the intact side), rather than towards greater sensory input, was not ruled out. In the present study, we addressed this question by examining whether or not an experimental manipulation designed to increase sensory stimulation would lead to turning towards the stimulated side. Sensory stimulation was applied by attaching a plastic clip into the fur on one side of the rat's face. The results show that this is sufficient to induce turning behavior.
Key words: A p o m o r p h i n e - Turning b e h a v i o r - Sensory imbalance - Sensory responsiveness - D o p a m i n e
Materials and methods
Dopaminergic systems modulate the behavioral response of animals to sensory stimuli. It is well established that lateralized dopaminergic activity in the striatum results in sensorimotor asymmetries. F o r example, turning behavior is observed under the influence of the dopamine receptor agonist apomorphine, either when injected into one striatum in normal rats, or when given systemically after a unilateral 6 - O H D A lesion o f the nigrostriatal projection (Pycock t980, for review). However, turning behavior under the influence of a p o m o r p h i n e is also produced by peripheral manipulation of sensory input. It has been shown that bandaging one side of the rat's face (Szechtman 1983) or simply cutting the vibrissae on one side (Milani et al. 1990; Schwarting et al. 1990, 1991) both induce turning towards the sensory intact (opposite) Correspondence to: H. Steiner
Subjects. Forty male Wistar rats of 180-230 g were housed in groups of four to nine animals under standard laboratory conditions. They had free access to food and tap water and were maintained under a 12 h light-dark cycle (lights on at 7 a.m.). Prior to the experiment the rats were handled for several days. Behavioral testing. Rats were tested in an open field monitored by a video system, which was designed for automated measurement of turning behavior (Bonatz et aL 1987). In short, the testing apparatus consisted of a black wooden chamber (60 x 60 × 40 cm) with a video camera positioned above the center of the chamber. The video image was recorded on tape and, in parallel, fed into a video interface (digitizer) of a microcomputer, thus allowing image analysis of the rat's behavior. The following parameters were assessed: the number of quarter, half and full turns (i.e., two and four consecutive quarter turns, respectively) to the left and to the right, in diameter (d) categories of d < 20, < 30, 20-30, 30-55, > 55 cm. In addition, the distance the rat traversed was measured (in meters). The analysis of behavior started 10 s after the animal was placed near the center of the open field. Testing was carried out under dim red light. Immediately before the rat was transferred to the open field, it received an injection of
391 apomorphine (or vehicle). Five minutes after the drug application, the rat was removed from the field and reintroduced. Then, the rat's behavior was recorded for a 5-min period. This baseline session was followed by four 5-rain test sessions during which the rat carried a plastic clip in the fur on one side of the face. The rat was removed from the open field, and the clip was gently placed into the fur about 1 can under the ear on one side. The plastic clip had a weight of 1.2 g and a length of 2.9 cm. In the first test session, half of the rats had the clip attached on the right side, the other half on the left. In subsequent sessions, the side with the clip was always reversed.
L 2O
10
I-"
10
Drugs. Apomorphine [apomorphine hydrochloride (APO); Woelm Pharma, Eschwege, FRG] was dissolved in saline containing 0.1% ascorbic acid on the day of testing. The rats were randomly assigned to one of five groups, and these received one of the following doses: 0.00 (vehicle), 0.05 (APO-0.05), 0.5 (APO4).5), 1.0 (APO-1), 5.0 (APO-5) mg/kg (n = 8 each). The drug was injected subcutaneously (in the neck) in a volume of 1 ml/kg.
Statistical analysis. Turns towards the side of the clip and towards the opposite side were compared with the Wilcoxon matched-pairs test. Between-group comparisons for turning and locomotion data were done with the Kruskal-Walfis test, followed by post hoc comparisons of individual groups with the Dunn Procedure (Rosner 1986). All P values are given two-tailed.
20 R
abcd B
abed
abed
1
obcd
2
abed
3
4
TEST SESSIONS
Fig. 1. Illustration of turning behavior under the influence of the clip in an individual animal. The numbers of half turns to the left (L) and to the right (R) in diameter categories of < 20 (a), 20~30 (b), 30-55 (c) and > 55 cm (d) are given. The animal received an injection of 1.0 mg/kg of apomorphine. In the baseline session (B; from 5 min to 10 min after the injection), the rat's behavior without clip was assessed. During the following four 5-rain test sessions, the rat carried a clip in the fur under the ear, either on the right side (sessions 1 and 3; side with clip indicated by solid bars) or on the left side (sessions 2 and 4)
Results
General observations Overall, the clip was well tolerated by m o s t of the animals. A few times, rats of the vehicle and APO-0.05 groups removed the clip with the forepaw shortly after they were placed in the open field. In such cases, it was attached again, and the trial was restarted. Rats injected with vehicle mostly m o v e d around the field during the first part o f the session. After this initial l o c o m o t o r activity, they often showed grooming behavior, and some thereby removed the clip with washing movements. In most cases, there was little or no locomotion afterwards. G r o o m i n g was sometimes also observed in APO-0.05 animals (which generally showed little l o c o m o t o r activity). However, it was m o r e directed towards ventral aspects o f the body. Nevertheless, occasionally grooming caused loss o f the clip. In contrast, in animals injected with higher doses o f a p o m o r p h i n e (0.5-5 mg/kg), grooming was never observed, neither were washing movements directed towards the clip. These rats showed well k n o w n a p o m o r p h i n e stereotypies, such as continuous snout contact with surthces (Szechtman et al. 1982; Beck et al. 1986), sniffing, whisking and sometimes licking and gnawing. F o r w a r d progression varied substantially between animals (see below). A few times the clip was lost through the course o f the session, especially when rats m o v e d very fast. However, attempts to remove the clip were not seen in these animals. (This contrasts with findings in pilot studies, in which clips were also attached to vibrissae. In rats injected with higher a p o m o r p h i n e doses, as well as in vehicle rats, clips were removed f r o m vibrissae immediately and vigorously. Similarly, clips were removed instantly and vigorously when placed into the fur and, by accident, also pinched skin.)
E
*
*
~
-x-~
O,5
1.0
5.0
0,5-5.0
I00
o 0
V "1~ 60 CO Z rv1-20
0.00
0.05
APOMORPHINE (mg/kg)
Fig. 2. The number (mean + SEM) of quarter turns with a diameter of less than 30 cm towards the side with clip (soh:d bars) and towards the side without clip (open bars) during 20 min of testing (4 test sessions pooled). Rats were injected with the following doses of apomorphine: 0.00 (vehicle), 0.05, 0.5, 1.0 and 5.0 mg/kg (n= 8 each). The data of rats with apomorphine doses of 0.5--5.0 mg/kg are also given pooled. *P< 0.05, **P< 0.001; Wilcoxon matchedpairs test, two-tailed
Clip-induced turning behavior Attaching the clip to the fur on one side of the face directed turning behavior in rats injected with a p o m o r phinc in doses o f 0.5-5 mg/kg; 23 out of 24 o f these animals showed more turns towards the side o f the clip than towards the opposite side. An example of an individual turning profile is depicted in Fig. 1. Turning asymmetries under the influence of the clip were most clearly observable in small-diameter turning categories. Figure 2 shows the total n u m b e r of quarter turns with a diameter of less than 30 cm throughout the four test sessions (20 min). Eight out of eight rats injected with
392
E
o 0 o3
V 19. O0 Z rr" ~D t'-
10
B
1
2
3
4 0.5-5.0 0.05
* 20
20
-z-
10
I0
2
g
1
2
3
4
.
g
1
2
3
4
TEST SESSIONS
Fig. 3. The number (mean+ SEM) of quarter turns with a diameter of less than 30 cm towards the side with clip (solid bars) and towards the side without clip (open bars), during the baseline session (B) (withoutclip) and during 4 test sessions. These data are given for rats injected with vehicle (0.00, upper left), 0.05 mg/kg apomorphine (lower left) or 0.5-5.0 mg/kg apomorphine (lower right). *P0.05; but APO-0.5-5 pooled: P < 0.05). However, all three groups with higher apomorphine doses expressed more quarter turns towards both sides than the APO-0.05 group (P
