Self-administration of cocaine and remifentanil by monkeys under concurrent-access conditions

Аннотация

Cocaine and opioids are often co-abused. Laboratory research has focused largely on the reinforcing effects of mixtures of drugs relative to the drugs alone. Less research has examined drug mixing by the subject under concurrent-access conditions. Objective Self-administration of various doses of cocaine and remifentanil was examined under concurrent-access conditions. It was hypothesized that if cocaine and opioid combinations were more effective reinforcers than the single drugs, subjects would mix the two drugs by adjusting their responding to cocaine and an opioid alternative to maintain an optimal ratio of cocaine/remifentanil intake.Method Three male rhesus monkeys were allowed to selfadminister cocaine (0.05–0.2 mg/kg/inj) or saline on one lever and remifentanil (0.05–0.4 μg/kg/inj) or saline on the other lever under concurrent fixed-ratio (FR) 10 schedules. Daily sessions lasted 2 h, and there was a 1-s timeout after every 10-s injection.