Psycho

Psychopharmacology48, 1- 6 (1976)

pharmacology 9 by Springer-Verlag 1976

Original Investigations On the Supersensitivity of Dopamine Receptors, Induced by Neuroleptics A. V. CHRISTENSEN*, B. FJALLAND, and I. MOLLER NIELSEN Department of Pharmacologyand Toxicology,H. Lundbeck& Co. A/S, Ottiliavej 7- 9, DK-2500Copenhagen-Valby,Denmark

Abstract. Different neuroleptics caused dopamine receptor blockade (antagonism against methylphenidate-induced compulsive gnawing) for varying lengths of time. When the receptor blockade had expired, supersensitivity to dopamine agonists (occurrence of apomorphine-induced compulsive gnawing and enhancement of methylphenidate-induced gnawing) developed and persisted for varying periods of time. The degree and duration of supersensitivity was related to the degree and duration of the preceding receptor blockade. Inhibition of catecholamine or 5-HT synthesis had no influence on development of supersensitivity. Stimulation with a dopamine agonist, apomorphine, during the period of the development of supersensitivity did not modify the enhanced receptor supersensitivity. A cholinergic-dopaminergic balance was shown to be involved in the manifestation of compulsive behavior during the supersensitivity phase. Tolerance to the dopamine antagonistic effect of a neuroleptic also developed after a single neuroleptic treatment, most likely due to increased sensitivity of the receptors for the dopamine agonist. It is concluded, that the dopamine receptor blockade induced by a single dose of a neuroleptic agent is a dynamic phenomenon which in the course of time is replaced by an increased sensitivity of the receptors to dopamine agonists. Noradrenergic or 5-HT neuron systems do not seem to be involved in the neuroleptic-induced supersensitivity, whereas a dopaminergic-cholinergic balance is operative in the supersensitivity situation. Key words: Neuroleptics - Supersensitivity - Dopamine receptors - Compulsive behavior - Mice Apomorphine - Methylphenidate - Synthesis inhibition - Cholinergic - Anticholinergic. * To whom offprint requests should be sent.

INTRODUCTION In recognition of the fact that neuroleptic therapy in most cases entails long-term administration and that the antipsychotic effect usually manifests itself only after prolonged treatment, many investigators have in recent years been concerned with the study of the pharmacologic effects of neuroleptics after prolonged treatment. Several workers have found tolerance development to various effects of neuroleptics (Irwin, 1961; Julou et al., 1967; Schelkunov, 1967; Theobald et al., 1968; Gy6rgy et al., 1969; Iwamoto and Matsuki, 1969; MNler Nielsen et al.,

1974, etc.). In other experiments it was found that prolonged neuroleptic treatment led to increased sensitivity to dopamine agonists (Klawans and Rubovitz, 1972; Fjalland and MNler Nielsen, 1974a, b; Tarsy and Baldessarini, 1974; Moore and Thornburg, 1975; yon Voigtlander et al., 1975; Sayers et al., 1975). In all these experiments, neuroleptics were administered by repeated dosage for an extended time. However, in a prolonged study after a single dose, increased sensitivity of the dopamine receptors to dopamine agonists was found for some days after the receptor blockade had expired (MNler Nielsen and Christensen, 1975). In order to investigate the correlation between induction of receptor blockade and of supersensitivity and to investigate the mechanism behind the supersensitivity development the present study was undertaken. As a model of receptor blockade, antagonism of methylphenidate-induced stereotypies was used (Pedersen and Christensen, 1972; Scheel-Krfiger, 1971). Receptor supersensitivity was determined by quantitative assessment of apomorphine- or methylphenidate-induced gnawing (Pedersen, 1967; Fjalland and M~bller Nielsen, 1974a).

2

Psychopharmacology 48 (1976)

MATERIALS AND METHODS

Outline of Experiments

Animals

Experiment L The receptor blockade (methylphenidate antagonism)

Male mice (NMRI/BOM, SPF), initial weight 18-25g, were used.

Compounds The following compounds were given as aqueous solutions: Methylphenidate hydrochloride, c~-MT (d,/-c~-methyltyrosinemethylester hydrochloride, H 44/68), PCPA (p-chlorophenylalanine methylester hydrochloride), scopolamine hydrobromide, chlorpromazine hydrochloride, cis (Z)-flupenthixol dihydrochloride, fluphenazine dihydrochloride, teflutixol dihydrochtoride (6-fluoro9-(3-(4-(2-hydroxyethyl)piperazin- 1-yl)propyl)-2-trifluoromethylthioxanthene dihydrochloride), piflutixol hydrochloride (6-fluoro-9(3- (4- (2- hydroxyethyl)piperidino)propylidene)-2- trifluoromethylthioxanthene hydrochloride), physostigmine salicylate and apomorphine hydrochloride. The solutions of FLA 63 (bis-4(methyl1-homopiperazinylthiocarbonyl)disulphide) and clozapine were prepared by adding a few drops of hydrochloric acid, and haloperidol was dissolved in 0.1 M tartaric acid and diluted with water.

Methylphenidate Antagonism The antagonism against methylphenidate was estimated as described by Pedersen and Christensen (1972). At varying intervals after pretreatment (on day zero) with the drug under investigation the mice were given a subcutaneous injection of methylphenidate 60 mg/kg. Immediately after the injection of methylphenidate the mice were placed for exactly 1 h in observation cages, 2 mice in each cage. The cages consisted of 30 cm high perspex boxes (12 x 25 cm) without bottom or Iid. During the experiments the cages were placed on corrugated paper, the corrugations facing upwards. For each dose level and time at least 5 pairs of mice were used, and the number of pairs that did not bite the corrugated paper, was counted.

and supersensitivity (gnawing with apomorphine) induced by eight different neuroleptics was followed after a single intraperitoneal injection. On each day following the injection new groups of mice were tested for methylphenidate antagonism and apomorphineinduced gnaw compulsion (5 x 2 mice per group).

Experiment II. On day zero mice were given an injection of 5, 1.25, or 0.31 mg/kg of teflutixol, intraperitoneally. The apomorphineinduced gnaw compulsion was then determined each day in the :10-day experimental period, new groups of 10 x 2 mice being used every day.

Experiment IIL The antagonistic E.D.so (the dose causing 50~ reduction of methylphenidate-induced gnaw compulsion) of teflutixol was determined 4 days after intraperitoneal pretreatment with teflutixol 5 mg/kg or saline. For each dose level 5 x 2 mice were used.

Experiment IV. The dose response-curves for methylphenidateinduced gnaw compulsion were determined 4 days after pretreatment with teflutixol 5 mg/kg or saline, intraperitoneally. For each dose ] 0 x 2 mice were used.

Experiment V. The influence of different treatments on the development of the teftutixoMnduced "potentiation" of apomorphine was investigated. Mice were tested in the apomorphine gnaw compulsion test 4 days after teflutixol 5 mg/kg intraperitoneally and otherwise treated as stated in Table 2.

Experiment VL The influence of cholinergic and anticholinergic treatments dn the teflutixol induced "potentiation" of apomorphine was determined 4 days after teflutixol 5 mg/kg intraperitoneally. For each dose 10 x 2 mice were used.

Statistics The statistical evaluation presented in Figure 3 and Table 3 were performed according to the X-test of van der Waerden and Nievergelt (1956). The E.D.so values (Table 1) were determined by probit analysis (Finney, 1952).

RESULTS

Apomorphine Gnaw-Compulsion The test used was a modification of that described by Ther and Schramm (1962). At varying intervals after pretreatment with the test substance, apomorphine, 10 mg/kg, 1.25 mg/kg, or 0.63 mg/kg was injected subcutaneously. Immediately after the injection of apomorphine, the mice were placed in the cages described above, two mice in each cage, for exactly 1 h. For each dose level and time at least 5 pairs of mice were used, and the number of pairs that bit the corrugated paper was counted. Furthermore, in some experiments the intensity of gnawing was determined quantitatively (Ther and Schramm, 1962; Pedersen, 1967).

Methylphenidate Potentiation Dose-response curves for methylphenidate-induced stereotypies were determined 4 days after pretreatment with the test substance. Methylphenidate 25, 20, 15, or i0 mg/kg was injected intravenously and the animals placed in observation cages as described above. After the experiment the biting intensity of each pair was estimated quantitatively as indicated above.

The time course of a n t a g o n i s m to m e t h y l p h e n i d a t e - i n d u c e d compulsive g n a w i n g a n d of the occurrence of a p o m o r p h i n e - i n d u c e d compulsive g n a w i n g following a single dose o f different neuroleptics are s h o w n in F i g u r e 1. A d m i n i s t r a t i o n of piflutixol (0.08 m g / k g intraperitoneally) resulted in methylp h e n i d a t e a n t a g o n i s m (receptor blockade) in a period o f 3 days after the injection. T w o h o u r s after pretreatm e n t (day 0) the i n h i b i t i o n was 60 % whereas complete p r o t e c t i o n against m e t h y l p h e n i d a t e was registered 24 a n d 48 h after the neuroleptic. O n the following days slight (day 3, 20 ~ ) or n o i n h i b i t i o n was observed. Teftutixol a n d fluphenazine (5 mg/kg) i n d u c e d complete p r o t e c t i o n against m e t h y l p h e n i d a t e d u r i n g 24 h after the a d m i n i s t r a t i o n a n d n o a n t a g o n i s m the following days. T h e protective effect of cis (Z)-flupenthixol (5 mg/kg), haloperidol (5 mg/kg), chlorprom a z i n e (40 mg/kg), a n d c h l o r p r o t h i x e n e (40 mg/kg)

A. V. Christensen et al. : Neuroleptic-Induced Supersensitivity rEFLUTIXOL

PIFLUTIXOL O/o 0 . 0 8 M G / K G

FLUPHENAZINE

CIS (Z)-FLUPENTH IXOL

5 MG/KG

5 MG/KG

CHLORPROTHIXENE 40 MG/KG

CLOZAPINE 8,0 M G / K G

ZL IL MG/KG

3

: : ; ; : : ; : ; :.~-

CHLORPROMAZINE 40 MG/KG

HALOPERI DOL %

MG/,KG

100

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DAYS

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INJECTION

Fig. 1. Influence of single doses of neuroleptlcs on methylphenidate- and apomorphine-induced stereotypies in mice. Ordinate indicates in case of methylphenidate percentage inhibition and in case of apomorphine percentage occurrence of gnawing. All treatments performed i.p. on day zero. OO: rnethylphenidate antagonism; 9 9 apomorphine gnawing. Each point represents mean of 5 pairs of mice

was only seen 2 h after the injections and had completely disappeared in the following days. Clozapine at a dose of 80 mg/kg had no methylphenidate antagonistic effect at all. In our experimental setup no gnawing was seen with apomorphine in nonpretreated mice nor in pretreated mice during the period of receptor blockade. However, all the compounds led apomorphine to cause compulsive gnawing: in various degrees after the period of receptor blockade. The effect of piflutixol and teflutixol appeared on days 2 - 3 and lasted for 6 days. Fluphenazine and cis (Z)-flupenthixol were quite similar in potentiating apomorphine. The effect of these substances only lasted 4 days. Haloperidol, chlorpromazine, chlorprothixene, and clozapine all showed some potentiation but this effect was considerably weaker and disappeared in 1 - 3 days. In contrast to the other compounds the effect ofclozapine was maximal on the day of pretreatment. The time course of apomorphine potentiation was studied after different doses of teflutixol (Fig. 2). The potentiation appeared 2 days after drug administration and the intensity and duration were dose dependent. Peak effect occurred about 3 days after injection of teflutixol. The methylphenidate antagonistic effect of teflutixol was investigated in normal mice and in mice treated 4 days previously with teflutixol 5 mg/kg intraperitoneally (Table 1). The dose of teflutixol required to antagonize methylphenidate by 50 ~o was about 10 times increased in the teflutixol-pretreated mice as compared to saline-pretreated mice.

lOO

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c~ 50

0

9

DAYS AFTER DRUG-ADMINISTRATION

Fig.2. Time course of teflutixol-induced potentiation of apomorphine. Teflutixol was given i.p. on day zero in doses of: O O 0.31 mg/kg; 9 ~ 1.25 mg/kg; and LX ZX 5 mg/kg. At various times after these treatments apomorphine l0 mg/kg s.c. was given and ~ animals gnawing estimated. Each point represents mean of 10 pairs of mice

Table 1. The methylphenidate antagonistic effect of teflutixol in mice treated 4 days previously with teflutixol 5 mg/kg or saline i.p. Methylphenidate antagonism of teflutixol E.D.so mg/kg i.p." Teflutixol-pretreated mice

Saline-pretreated mice

1.2 (0.6- 2.5)

0.13 (0.08 - 0.22)

a

In brackets 95 o% confidence limits.

4

Psychopharmacology 48 (1976) Table 2. Influence of treatments with c~-MT, FLA 63, PCPA, or apomorphine on the teflutixol-induced potentiation of apomorphine

50,

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Substance

40. ~3

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20

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Dose

Time (h) before apomorphine

N pairs of animals gnawing

mg/kg

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