Discriminative profile of MDMA.

Groups of rats were trained to discriminate the stimulus properties of dopaminergically and/or serotonergically active drugs, viz., apomorphine, fenfluramine, tetrahydro-beta-carboline (THBC) and l-cathinone. Once trained, these animals were given several doses of drugs used in training and dose-response relationships and ED50 values were generated. Subsequently, each group of trained rats was administered various doses of 3,4-methylenedioxymethamphetamine (MDMA) to test generalization of the interoceptive cue of the drug used for training to MDMA. Rats trained to fenfluramine, THBC, and l-cathinone were observed to discriminate MDMA in a manner similar to the drug state to which they had been trained. Analysis of dose-response curves suggested that MDMA may be acting both as an indirect dopaminergic agonist and as a serotonergic receptor agonist. This duality of effect of MDMA has been evidenced by other studies and may account for its present abuse potential.