Performance effects with repeated-response measures during pimozide-produced dopamine receptor blockade.

Rats were trained to lever-press for either food reward or brain-stimulation reward on a continuous reinforcement schedule. Following training each animal was extinguished (i.e. tested with the reward omitted) under the influence of pimozide (0.25 mg/Kg or 0.5 mg/Kg). Pimozide produced a dose-dependent reduction in the mean number of responses to extinction made by rats in ecach group. In a second experiment, pimozide produced a similar dose-dependent decrease in the performance of a naturally occurring behavior (nose-poking) that had never been associated with reward. These data suggest that dopamine receptor blockade can produce a perofrmance deficit in situations which require repetitive responses, and that this deficit is unrelated to the presence or absence of reward.