The effect of pimozide on variable-interval performance: A test of the ‘anhedonia’ hypothesis of the mode of action of neuroleptics

✍ Scribed by M. J. Morley; C. M. Bradshaw; E. Szabadi

• Publisher: Springer
• Year: 1984
• Tongue: English
• Weight: 633 KB
• Volume: 84
• Category: Article
• ISSN: 0033-3158
• DOI: 10.1007/bf00431461

✦ Synopsis

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.