Interaction of haloperidol and SCH 23390 with cocaine and dopamine receptor subtype-selective agonists on schedule-controlled behavior of squirrel monkeys.

Involvement of D1 and D2 dopamine receptors in the effects of cocaine on schedule-controlled behavior was evaluated in squirrel monkeys responding under a multiple fixed-interval 5-min, fixed-ratio 10 schedule (mult FI FR) of food delivery. Cocaine and the D2 agonist quinpirole increased responding under the F1 at certain doses and disrupted the temporal patterning of behavior. Higher doses of these drugs decreased responding. In contrast, the D1 agonist SKF 38393 was devoid of behavioral activity up to 10 mg/kg where response suppression was obtained without significant modification of the temporal distribution of responding. The D2 antagonist haloperidol (0.001-0.03 mg/kg) did not alter the behavioral effects of cocaine up to doses that had pronounced behavioral effects on their own. However, haloperidol attenuated the behavioral effects of quinpirole. In contrast, the D1 antagonist SCH 23390 partially attenuated the response rate-suppressant effects of cocaine without blocking cocaine-induced disruptions of temporal response patterning. SCH 23390 did not antagonize the behavioral effects of SKF 38393. These results suggest that independent stimulation of either D1 or D2 receptors alone does not play a major role in the effects of cocaine on schedule-controlled behavior of squirrel monkeys.