The effect of chronic MDMA treatment on pre-trained DMTS performance and acquisition of a DNMTS rule in rats

Abstract

Evidence from rats, non-human primates and humans shows that the drug of abuse, 3,4-methylenedioxymethamphetamine (MDMA or "ecstasy") has a profound neurotoxic effect on serotonin (5-HT) neurons in the brain. Human users often report impairment of memory and mnemonic function after long-term MDMA use, yet there is relatively little evidence of such impairments in experimental animal studies. In this study rats that had previously learned the delayed matching-to-sample (DMTS) task were treated with a large dose of MDMA (n=17) (four injections of 10mg/kg over 6 hours) or vehicle (n=13) on a single day. Two-weeks later animals resumed DMTS test sessions. A small overall deficit in accuracy was found for MDMA-treated animals for the five sessions post-treatment. At the conclusion of DMTS testing, rats were changed to the delayed non matching-to-sample task (DNMTS) and acquisition of this novel task was measured for the subsequent twenty test sessions. MDMA-treated animals showed no significant impairments in acquisition of the novel DNMTS at any delay tested. Therefore, chronic exposure to a high dose of MDMA impaired accuracy on the pretrained DMTS task, but did not have any effect on acquisition of the new DNMTS rule.