Discriminative stimulus effects of 3,4-methylenedioxymethamphetamine (MDMA) in humans trained to discriminate among d-amphetamine, meta-chlorophenylpiperazine and placebo.

In animals, two-choice drug discrimination studies have demonstrated that the behavioral effects of 3,4-methylenedioxymethamphetamine (MDMA) are mediated by dopaminergic and serotonergic systems. In order to delineate the relative role of these systems, three-choice paradigms have been used in animals, with findings indicating a more prominent role for serotonin. Human studies assessing the subjective and physiological effects of MDMA have also indicated a mixed action.