Effects of quinpirole and SKF 38393 alone and in combination in squirrel monkeys trained to discriminate cocaine.

J L Katz, J M Witkin

Index: Psychopharmacology 107 , 217, (1992)

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Abstract

The present study was designed to assess the behavioral similarity of the effects of prototype dopamine receptor-subtype selective agonists and cocaine. Squirrel monkeys (N = 4) were trained with food reinforcement to press one of two levers after administration of IV cocaine (0.3 mg/kg) or the other lever after saline. After training, IV cocaine produced reliable responding on the cocaine lever (greater than 98%), whereas saline produced reliable responding on the alternate lever (greater than 98%). The D2 agonist, quinpirole (0.003-1.0 mg/kg, IM), produced dose-related increases in cocaine-appropriate responding, with maximal effects of 62%. When delivered IV, quinpirole (0.01-0.17 mg/kg) was approximately twice as potent, but no more effective. The D1 agonist, SKF 38393 (0.3-30.0 mg/kg, IM or 3.0-17.0 mg/kg, IV) failed to produce any significant cocaine-appropriate responding. Further, pretreatment with SKF 38393 (either 0.3 or 10.0 mg/kg, IM) did not significantly alter the the quinpirole (0.01-1.0 mg/kg, IM) dose-effect curve. The effects of these drugs differ from those previously reported in rats, suggesting a species difference that may be of importance in evaluating the behavioral pharmacology of cocaine.