Acute and carryover effects in mice of MDMA ("ecstasy") administration during periadolescence

In spite of the increasing evidence concerning its neurotoxicity, young human individuals are often involved in the recreational use of amphetamine-type stimulants such as 3,4-methylenedioxymethamphetamine (MDMA or "ecstasy"). A study aimed to investigate short- and long-term consequences of a repeated and intermittent MDMA administration (0, 5 or 10 mg/kg i.p., 3 days treatment history) was conducted in mice. Mice were injected at different phases in development, namely at early (28 days old), middle (38 days old) or late (52 days old) adolescence. When assessed for nociceptive response, a dose-dependent analgesia was found in middle and late adolescent mice. Carryover consequences of previous MDMA treatment were then investigated at adulthood (80 days old). In a social interaction test, levels of environment exploration and social behaviour resulted markedly increased in drug-free state as a function of drug exposure during development, whereas others behaviours were reduced. MDMA challenge (5-mg/kg dose) produced the expected hyperactivity, as well as a marked increment of hypothalamic serotonin (5-hydroxyhyptamine, 5-HT) levels. Mice treated chronically with MDMA during middle and late adolescence were associated with important reductions of the indoleamine. As a whole, these results indicate a differential long-term vulnerability to behavioural and neurotoxicant effects of MDMA as a function of the developmental stage of exposure.