Reinforcing effects of MDMA ('ecstasy') in drug-naive and cocaine-trained rats

3,4-Methylenedioxymethamphetamine (MDMA; 'ecstasy') is one of the most prev alent illegal drugs of abuse among European adolescents, a population not g enerally experienced with respect to 'hard' drugs such as cocaine. We, ther efore, determined the reinforcing effect of intravenously self-administered MDMA in a fixed ratio 1 time-out 150 s schedule of reinforcement in rats t hat were truly drug naive and compared it to cocaine-trained rats. The rein forcing effect of MDMA [0.032-10 mg/(kg.injection)] did not differ between drug-naive rats and cocaine-trained ones. MDMA sensitized the animals to it s own rate-increasing effect but not to that of cocaine. When MDMA was test ed after cocaine, there was no carryover of cocaine's reinforcing effect to that of MDMA, suggesting that MDMA and cocaine produce distinct interocept ive stimuli in rats. Copyright (C) 2001 S. Karger AG, Basel.