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A comparison of the reinforcing efficacy of 3,4-methylenedioxymethamphetamine (MDMA, “ecstasy”) with cocaine in rhesus monkeys

2004; Elsevier BV; Volume: 78; Issue: 2 Linguagem: Inglês

10.1016/j.drugalcdep.2004.10.006

1879-0046

Joshua A. Lile, Jason T. Ross, Michael A. Nader,

Psychedelics and Drug Studies

The purpose of the present study was to compare the reinforcing efficacy of 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') to cocaine. Rhesus monkeys (n = 4) responded under a within-session, exponentially increasing, progressive-ratio (PR) schedule of cocaine reinforcement. Breaking point (BP) for the PR schedule was defined as the final response requirement completed before 2 h had elapsed without an injection delivered. Saline and doses of cocaine (0.003–0.3 mg/kg/injection) and MDMA (0.01–0.56 mg/kg/injection) were substituted for the training dose of cocaine for at least five consecutive sessions. Both cocaine and MDMA functioned as reinforcers, but self-administration of MDMA occurred at fewer doses and a significantly lower peak BP was obtained for MDMA. These data demonstrate that MDMA functions as a reinforcer, although its reinforcing efficacy appears to be less than that of cocaine.