Conditioning following repeated exposure to MDMA in rats: Role in the maintenance of MDMA self-administration.

Rats pressed a lever to receive intravenous MDMA, and their responding increased when the required number of presses rose from 1 to 5, decreased when saline replaced MDMA, and increased again when MDMA was restored. During training, each MDMA infusion was accompanied by a light. After an average of 19 daily sessions, omitting either the light or the drug caused responding to decline gradually over 15 days. Omitting both the light and the drug produced a dramatic and lasting decrease in responding. These results suggest that cues paired with MDMA acquire conditioned properties that may contribute to drug-taking behavior.

Study at a glance

Abstract

There has been some controversy in the literature concerning the ability of +/-3,4 methylenedioxymethamphetamine (MDMA) to reinforce operant responding in rats. In the present study, operant responding maintained by intravenous MDMA infusions increased when the fixed ratio schedule was increased from 1 to 5, decreased when saline was substituted for MDMA, and increased again when MDMA was reintroduced. During self-administration training, each infusion of MDMA was paired with the illumination of a light stimulus. The role of the continued presentation of this drug-associated stimulus in operant responding was measured in groups of rats that had received comparable exposure (average 19 daily test sessions) to MDMA during training. When either the light stimulus or the drug infusion was omitted, operant responding decreased gradually over the 15-day test period following training. When both the light stimulus and the MDMA infusion were omitted, there was a dramatic decrease in operant responding that persisted for the entire 15-day test period. These findings suggest that cues associated with MDMA develop conditioned properties that might contribute to drug taking.