Time-response effects of pimozide on operant behavior and schedule-induced polydipsia

Previous research has indicated that the administration of specific doses of pimozide results in the suppression of the acquisition of schedule-induced polydipsia in rats while not affecting operant behavior. The purpose of this study was to determine if these results were due to a specific action of pimozide on schedule-induced polydipsia or if they were due to an insufficient presession time of drug administration. Pimozide at 1.0 mg/kg was administered to three groups of rats at either 30, 60 or 120 minutes presession with control subjects receiving administration of the drug vehicle also at these times. The results of the study were that both operant behavior and the acquisition of schedule-induced polydipsia were affected in a nondifferential and time-dependent manner by pimozide. It was also found that pimozide caused an alteration in the temporal pattern of both schedule-induced polydipsia and operant responding. This latter result appears to have been caused by a disruption in sensorimotor integration due to the dopamine blocking properties of pimozide.