THE MOLECULAR MECHANISM OF ECSTASY [3,4-METHYLENEDIOXY-METHAMPHETAMINE (MDMA)] - SEROTONIN TRANSPORTERS ARE TARGETS FOR MDMA-INDUCED SEROTONIN RELEASE

MDMA ("ecstasy") has been widely reported as a drug of abuse and as a neurotoxin. This report describes the mechanism of MDMA action at serotonin transporters from plasma membranes and secretory vesicles. MDMA stimulates serotonin efflux from both types of membrane vesicle. In plasma membrane vesicles isolated from human platelets, MDMA inhibits serotonin transport and [H-3]imipramine binding by direct interaction with the Na+-dependent serotonin transporter. MDMA stimulates radiolabel efflux from plasma membrane vesicles preloaded with [H-3]serotonin in a stereo-specific, Na+-dependent, and imipramine-sensitive manner characteristic of transporter-mediated exchange. In membrane vesicles isolated from bovine adrenal chromaffin granules, which contain the vesicular biogenic amine transporter, MDMA inhibits ATP-dependent [H-3]serotonin accumulation and stimulates efflux of previously accumulated [H-3]serotonin. Stimulation of vesicular [H-3]serotonin efflux is due to dissipation of the transmembrane pH difference generated by ATP hydrolysis and to direct interaction with the vesicular amine transporter.