Some effects of cocaine and two cocaine analogs on schedule-controlled behavior of squirrel monkeys.

The behavioral effects of two phenyltropane derivatives of coaine were compared with those of cocaine. Squirrel monkeys responded under multiple fixed-interval, fixed-ratio schedules of either stimulus-shock termination or food presentation or under a fixed-ratio schedule of food presentation. The effects of the three drugs were independent of the type of event that maintained responding. Under the fixed-interval schedules, some doses of each drug increased responding, whereas larger doses generally decreased responding. Maximal increases in responding were similar with each drug. Appropriate doses of each drug increased low response rates, which occurred during the initial segments of the fixed intervals, but had little effect on or decreased higher response rates, which occurred during the later segments of the fixed intervals. Under the fixed-ratio schedules, each drug decreased responding in a dose-related manner. Decreases in fixed-ratio responding resulted both from increased periods of no responding at the beginning of the fixed ratios and from decreased rates of responding once responding began. Each cocaine analog had a slower onset of effect and longer responding began. Each cocaine analog had a slower onset of effect and a longer duration of effect than cocaine. The behavioral effects of the two cocaine analogs were qualitatively similar to those of cocaine, but each was 3 to 10 times more potent than cocaine.