Effect of once weekly treatment with 3,4-methylenedioxymethamphetamine on schedule-controlled behavior in rats.Eur J Pharmacol. 1998 Sep 25; 358(1):1-8.EJ
The present study examined the effects of 3,4-methylenedioxymethamphetamine (MDMA), before and after once a week dosing, on the behavior of rats responding under a fixed ratio 20 schedule of reinforcement. Acutely, cumulative doses of MDMA dose-dependently decreased responding when compared to a series of water injections. Rats were then separated into two groups, one of which received only weekly MDMA ('paired') while the other received an additional injection of water each week ('unpaired'). Weekly dosing with MDMA resulted in significantly increased responding at low doses in the paired group but not in the unpaired group. When water injections were readministered there was a significant increase in responding in both groups. During the weekly regimen, locomotor activity also increased significantly over time after both water and MDMA injections. In conclusion, it appears that even weekly dosing with a small amount of MDMA can have long-lasting effects that are manifested in both operant and spontaneous behavior and that may be mediated by a conditioning mechanism.