Effect of MDMA (ecstasy) on activity and cocaine conditioned place preference in adult and adolescent rats

MDMA (ecstasy) is a drug commonly used in adolescence, and many users of MDMA also use other illicit drugs. It is not known whether MDMA during adolescence alters subsequent responses to cocaine differently than in adults. This study examined the effects of MDMA in adolescent and adult rats on cocaine conditioned reward. At the start of these experiments, adolescent rats were at postnatal day (PND) 33 and adult rats at PND 60. Each rat was treated for 7 days with MDMA (2 or 5 mg/kg/day or vehicle) and locomotor activity was measured. Five days later cocaine conditioned place preference (CPP) was begun. Rats were trained for 3 days, in the morning with saline and in the afternoon with 10 mg/kg cocaine in 30 min sessions, and tested on the fourth day. MDMA stimulated activity in both age groups, but with a greater effect in the adult rats. Sensitization to the locomotor-stimulant effects of the lower dose of MDMA occurred in adult rats and in both groups to the higher dose. Cocaine did not produce a CPP in vehicle-treated adolescent rats, but a significant CPP was observed subsequent to treatment with MDMA. In contrast, cocaine-induced CPP was diminished after MDMA in adult rats. These effects were still evident 2 weeks later upon retest. Thus, under the present conditions, MDMA increased cocaine conditioned reward in adolescent and decreased it in adult rats. These findings suggest that exposure to MDMA during this critical developmental period may carry a greater risk than during adulthood and that male adolescents may be particularly vulnerable to the risk of stimulant abuse after use of MDMA.