The effects of electric shock on responding maintained by cocaine injections in a choice procedure in the 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 also available on a second lever without shock. In each session rhesus monkeys were allowed to self-inject cocaine five times in the presence of a stimulus. Thirty minutes after the fifth injection a second dose of cocaine could be self-injected five 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. Thirty minutes later choice trials began in which both stimuli were present and monkeys could choose one of the two doses of cocaine. Electric shock was delivered at the onset of the injection of one of these alternatives. Initially, both doses of cocaine were 0.1 mg/kg. The dose of cocaine associated with electric shock was systematically increased until it was preferred to the dose not associated with electric shock. The results indicate that although responding maintained by cocaine can be suppressed by punishment, this effect can be attenuated by increasing magnitude of reinforcement.