Cocaine self-administration in monkeys: effects on the acquisition and performance of response sequences

A three-component multiple schedule of intravenous cocaine self-administration (0.01-0.3 mg/kg), repeated acquisition and performance was used to examine the effects of self-administered cocaine on learning in rhesus monkeys. A 0.03 mg/kg infusion of cocaine maintained reliable self-administration without markedly decreasing overall response rate or increasing the percentage of errors in the acquisition and performance components in which food was presented. When saline was substituted for 0.03 mg/kg of cocaine, there was little or no effect on responding in the acquisition or performance components while the number of infusions and response rate in the self-administration component decreased. These effects occurred to a greater extent under a FR 90 schedule (Experiment 2) as compared to a FR 30 schedule (Experiment 1) of cocaine self administration. Substitution of higher infusion doses of cocaine also decreased response rate and the number of infusions in the self-administration components, and substantially decreased responding in the acquisition components; decreases in overall accuracy of responding were evident when responding in this schedule component occurred. Taken together, these data indicate that learning is generally more sensitive than performance to the disruptive effects of self-administered cocaine.