Abstract

Rats Were trained to press a lever for food under a multiple sehedule of reinforcement Components of the multiple schedule were extinction, 4-min fixed interval and a fixed ratio of 25 responses. These sehedules were coordinated with distinctive visual stimuli and were repeated in a fixed order during daily 4-hr sessions. After stabilization of performance, each component of the multiple schedule generated a characteristie pattern of behavior. Effects of chlorpromazine (CPZ) On this complex performance were studied with single doses of 0.25, 0.50, 1.0 and 1.5 mg/kg i.m. CPZ decreased the rate of responding under fixed ratio as a monotonic function of dose from 0.50 to 1.5 mg/kg. Under fixed interval, average response rates were unaffected below 0.50 mg/kg and decreased at larger doses. The temporal paterning of fixed-interval behavior was affect at all doses. Low response rates extinetion were unaffected by CPZ. Maximal effects occurred in the 2nd hr after administration, with larger doses producing progressively longer durations of action. Repeated administration of 0.5 mg kg for 5 hays and of 1.0 mg/kg for 12 days had effects similar to single doses. Control performance was recoverd after withdrawal of chroic CPZ. Related experimental findings are discussed.