Serotonin (5-HT) release is the primary pharmacological mechanism of 3,4-methylenedioxymethamphetamine (MDMA, ‘ecstasy’) action in the primate brain. Dopamine release and direct stimulation of dopamine D2 and serotonin 5-HT 2A receptors also contributes to the overall action of MDMA. The role of 5-HT 1A receptors in the human psychopharmacology of MDMA, however, has not yet been elucidated. In...