PENTOBARBITAL, DIAZEPAM AND PHENCYCLIDINE DISRUPT DELAYED MATCHING PERFORMANCE - INTERACTIONS WITH PICROTOXIN IN PIGEONS AND SQUIRREL-MONKEYS

The ability of picrotoxin to antagonize selectively the effects of pen tobarbital was investigated in pigeons and squirrel monkeys responding under a titrating matching-to-sample schedule of reinforcement. Under the titrating matching-to-sample baseline, the length of the delay ch anged as a function of the animal's matching accuracy Picrotoxin (0.03 -1 mg/kg) failed to alter significantly the matching accuracy of pigeo ns; however, rate of responding was markedly suppressed at a dose of 1 mg/kg. In squirrel monkeys responding under a similar schedule, picro toxin (0.001-0.3 mg/kg) was without significant effect. Selected doses of picrotoxin in both pigeons (0.3 and 0.56 mg/kg) and squirrel monke ys (0.1 and 0.3 mg/kg) failed to shift the pentobarbital or diazepam d ose-response curve for mean delay length to the right. However, in bot h species, picrotoxin shifted the dose-response curve for pentobarbita l on rate of responding to the right. No such shift was observed for t he effect of diazepam on rate of responding. In both species, the comb ination of picrotoxin and phencyclidine shifted the dose-response curv es for phencyclidine on rate of responding, but not mean delay, downwa rd and to the left, in an apparent additive manner. Thus, picrotoxin f aded to produce a significant pharmacological antagonism of the effect s of pentobarbital, diazepam or phencyclidine on matching accuracy. Th is failure to observe an antagonism of the effects of pentobarbital on matching accuracy, at doses of picrotoxin that antagonized the effect s of pentobarbital on rate of responding, suggests that the effects of pentobarbital on matching accuracy and rate of responding are mediate d by different receptor sites.