MDMA and performance under a progressive-ratio schedule of water delivery

This study investigated the possible motivational effects of ()3,4-methylenedioxymetham-phetamine (MDMA, ecstasy) in water-deprived rats responding under a progressive-ratio 2 schedule of water delivery. Lower doses (1.0 and 1.8 mg/kg ip) had inconsistent effects on breakpoints and response rates, whereas higher doses (3.2 and 5.6 mg/kg ip) significantly decreased both response measures relative to vehicle control levels. Increasing the level of water restriction significantly increased both response measures, and decreasing restriction significantly decreased both response measures. This study found no evidence that MDMA increased the reinforcing efficacy of water, although prior findings have suggested that the drug might have such an effect. MDMA-induced changes in motor activity may account for the present results.