The effects of pimozide and of reward omission on fixed-interval behavior of rats maintained by food and electrical brain stimulation.

Pimozide (0.125 to 2.0 mg/kg) was administered to rats whose behavior was maintained by a fixed-interval schedule in which the reward was either food (Experiment 1) or electrical stimulation of the brain (Experiment 2). The effects of the drug were compared with the effects of withholding reward (i.e., extinction) in both experiments. Reward omission and administration of pimozide both resulted in decreases in overall rates of responding and increases in the time taken by the subjects to complete a specified number of fixed-intervals. The typical patterning of responding during the sessions of reward omission was also characteristic of the effects of pimozide with food reward but not with brain stimulation reward. The duration of trains of brain stimulation which was under the control of the subjects in Experiment 2, was not altered by administration of pimozide. The differences between the effects of pimozide on behavior maintained by intermittent food reward or by intermittent brain stimulation reward limits a global interpretation of the effects of neuroleptics.