Comparison of the reinforcing and anxiogenic effects of intravenous cocaine and cocaethylene.

Abstract

People report that ethanol improves the experience produced by cocaine. This effect may be attributable to cocaethylene (CE), a cocaine metabolite formed only in the presence of ethanol. To test this, rats were trained to run an alley for a single intravenous dose of either cocaine (0.5-2.0 mg/kg) or an equimolar dose of CE (0.75-2.88 mg/kg). The rats' start latency and running speed measured the reinforcing effects of the drugs and the number of times rats approached but failed to enter the goal box (i.e., approach-avoidance retreats) indexed anxiety. Rats reinforced with CE had shorter start latencies and faster running speeds and exhibited fewer "retreats" than cocaine-reinforced rats. These results suggest that CE is more reinforcing and less anxiogenic than cocaine and hence may account for the combined effects of cocaine and ethanol in humans.