MDMA elicits behavioral and neurochemical sensitization in rats.

Rats were treated with repeated injections of saline or one of two doses of (+/-)3,4-methylenedioxymethamphetamine (MDMA; 5 or 20 mg/kg, s.c.). Rats pretreated with either of the two repeated MDMA treatment regimens demonstrated an augmented increase in motor activity to an injection of MDMA made 12 days after the last repeated injection compared with either the first MDMA injection or MDMA given to animals pretreated with repeated saline. Furthermore, animals pretreated with the highest dose of repeated MDMA revealed a greater behavioral response to cocaine (15 mg/kg, i.p.). Microdialysis was conducted in the nucleus accumbens and the capacity of MDMA (5 mg/kg, s.c.) to elevate extracellular dopamine content was augmented in rats pretreated with repeated MDMA compared with the animals pretreated with repeated saline. These data reveal repeated MDMA administration produces behavioral sensitization and enhanced dopamine transmission in the nucleus accumbens of rats.