EFFECTS OF ELECTRIC-SHOCK ON RESPONDING MAINTAINED BY COCAINE INJECTIONS IN A CHOICE PROCEDURE IN RHESUS-MONKEY

A choice procedure was used to determine the ability of electric shock to suppress cocaine-maintained responding in a situation where cocaine was available on a 2nd lever without shock. In each session rhesus monkeys were allowed to self-inject cocaine 5 times in the presence of a stimulus. Thirty min after the 5th injection a 2nd cocaine dose could be self-injected 5 times in the presence of a different stimulus. At the onset of the injection of this dose a 5 or 10 mA electric shock was delivered. Choice trials began 30 min later in which both stimuli were present and monkeys could choose 1 of the 2 cocaine doses. Electric shock was delivered at the onset of the injection of 1 of these alternatives. Initially, both doses of cocaine were 0.1 mg/kg. The cocaine dose associated with electric shock was systematically increased until it was preferred to the dose not associated with electric shock. Although responding maintained by cocaine can be suppressed by punishment, this effect can be attenuated by increasing magnitude of reinforcement.