Effects of anticholinergic drugs on DRL performance of rhesus monkeys

Four adult rhesus monkeys were trained to stable performance baselines on a differential reinforcement of low rates (DRL) 28 sec schedule for food pellet presentation. The effects of graded doses of atropine SO4, benactyzine HCl, and scopolamine HBr on performance were studied. All three anticholinergic compounds produced dose-related decreases in the number of food pellets earned. The number of responses was decreased only by the highest scopolamine dose. The unimodal peak of interresponse times (IRTs) was flattened under drug conditions such that there were roughly equal frequencies of responding in all IRT intervals. Drug potencies for producing these effects were: scopolamine greater than atropine greater than benactyzine.