The effects of a probably neurotoxic regimen of MDMA on dopamine (DA) transport was studied in synaptosomes from striatal tissue taken from rats given repeated doses of MDMA (4 doses of 10 mg/kg every 2 h) or saline. Before sacrifice, rats were maintained in group cages, and some were placed in a cool environment (6 C) while the rest were kept at room temperature (24 C). Rats were killed either 1 or 24 h after MDMA (saline-treated rats killed 1 h post-treatment). Results were also compared with data from another study on the effects of methamphetamine on DA transport that apparently used the same methods and similar but higher doses of methamphetamine (15 mg/kg). Surprisingly, rats in cold environment were not hypothermic, but remained normothermic; rats in room-temperature environment were hyperthermic. Plasmalemmal DA (measured in cell membrane) was measured alone, and after binding of tritiated WIN35428, a ligand for the dopamine transporter. MDMA reduced plasmalemmal DA uptake 1 h post-treatment, but DA transporter binding was unaffected by MDMA treatment. Reduced plasmalemmal DA after MDMA was no longer apparent 24 h after treatment. In contrast, dopamine transporter ligand binding was only slightly reduced 1 h post-treatment, but with slight reduction persisting 24 h post-treatment. Preventing hyperthermia by keeping rat in cold environment during drug treatment did not alter changes in DA uptake after MDMA. Rats pretreated with the catecholamine depleter a-methyl-p-tyrosine (AMPT) had reduced DA content, but this did not reduce MDMA-induced decrease in plasmalemmal DA. When synaptosomes were incubated with 10 mM MDMA for 30 min at 37 C, there was reduction in DA uptake in vitro. Two protein kinase C (PKC) inhibitors (NPC15437 and Ro31-7549) attenuated MDMA-induced decrease in DA uptake in synaptosomes, but WIN35428 did not prevent MDMA-induced reduction in DA uptake. When vesicles were taken from same striatal tissue, it was found that MDMA decreased DA uptake in vesicles (compared with saline-treated animals) and reduced DHTBZ binding. Preventing hyperthermia did not attenuate reduction in vesicular DA uptake or DHTBZ binding. Eticlopride pre-treatment (15 min before each MDMA attenuated MDMA-induced decrease in vesicular DA uptake. Using data from an investigation of the effects of methamphetamine on DA transport in cell membranes as a comparison, the authors note that methamphetamine-induced alterations last longer than MDMA-induced alterations, and that methamphetamine produced similar effects at a lower dose (1 dose of 15 mg/kg methamphetamine versus 4 does of 10 mg/kg MDMA). These findings suggest that the PKC signaling pathway might be involved MDMA-induced DA release in rats.