Psychopharmacology

, Volume 84, Issue 4, pp 531–536 | Cite as

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

  • M. J. Morley
  • C. M. Bradshaw
  • E. Szabadi
Original Investigations

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 K H (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 K H 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 each schedule. The drug suppressed 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.

Key words

Operant behaviour Neuroleptics Pimozide “Anhedonia” hypothesis Herrnstein's equation 

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Copyright information

© Springer-Verlag 1984

Authors and Affiliations

  • M. J. Morley
    • 1
  • C. M. Bradshaw
    • 1
  • E. Szabadi
    • 1
  1. 1.Department of PsychiatryUniversity of ManchesterManchesterUK

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