MDMA (3,4 Methylenedioxy-methamphetamine) binds and blocks the presynaptic serotonin reuptake transporters and postsynaptic serotonin 5-HT2A receptors, with highest affinity for the first. Whether 5-HT2A receptor density decreases due to MDMA's direct effect on postsynaptic serotonin receptors is at present not known. This study analyzes whether direct stimulation of the postsynaptic 5-HT2A receptor by MDMA in organotypic hippocampal cultures results in cell death and downregulation of this receptor. Fifty or 100 microM MDMA was added to 1 week old cultures, made of 11 day old rat pups. Fluorojade and immunostaining for MAP2 and 5-HT2A to determine neurodegeneration, and changes in receptor density, respectively, resulted in no significant differences. MDMA's neurotoxicity and regulation of post-synaptic 5-HT2A receptors thus seems to require the presence of intact serotonergic terminals.