title: The effect of pimozide on variable-interval performance: a test of the 'anhedonia' hypothesis of the mode of action of neuroleptics.
abstract: A quantitative behavioural test system based on Herrnstein's (1970) equation was used to test a prediction derived from the "anhedonia" hypothesis of neuroleptic action, that pimozide should increase the value of the behavioural parameter KH (the reinforcement frequency needed to maintain the half-maximal response rate in variable-interval schedules). On the basis of theoretical considerations, it was shown that the equation implies that a drug which exerts such an effect on KH must have a more profound suppressant effect on performance maintained by low reinforcement frequencies than on performance maintained by high reinforcement frequencies. Fifteen rats were trained under variable-interval 10-s and variable-interval 100-s schedules, and the effect of pimozide (0.125, 0.25, 0.33, and 0.5 mg/kg) was tested on performance maintained under both schedules in a dose-dependent manner, and there was no tendency for the drug to exert a greater effect on performance maintained under the lower reinforcement frequency. These results do not provide any evidence that the effect of pimozide on variable-interval performance is due to an "anti-hedonic effect"; rather, they are compatible with the hypothesis that pimozide impairs the capacity to respond.
mesh_terms: D000818:Animals; D014150:Antipsychotic Agents / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D008959:Models, Neurological; D010868:Pimozide / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012055:Reinforcement Schedule
chemical_list: D014150:Antipsychotic Agents; D010868:Pimozide