Effects of Cortical Serotonin Depletion Induced by 3,4-Methylenedioxymethamphetamine (MDMA) on Behavior, Before and After Additional Cholinergic Blockade

Abstract

Repeated treatment with high doses of 3,4-methylenedioxymethamphetamine (MDMA; "ecstasy") produces a long-lasting depletion of brain serotonin, presumably because of the degeneration of serotonin axon terminals. However, very little is known about the long-term behavioral consequences of MDMA neurotoxicity. The experiments reported here were designed to evaluate the effects of MDMA neurotoxicity on a number of behavioral tests known to be sensitive to neocortical and hippocampal damage. Also, the effect of additional cholinergic blockade in MDMA-pretreated rats was evaluated because loss of both the serotonergic and cholinergic inputs to the cortex produces a functional decortication and a behavioral syndrome reminiscent of human global dementia. Partial depletion of neocortical serotonin (72.6%) did not produce deficits on a variety of behavioral tests, including a place navigation learning-set task, skilled forelimb use, or the ability to make complex judgements regarding the stimulus properties of food in a foraging situation, and neither did additional cholinergic blockade. MDMA-pretreated rats had a mild impairment in rapidly developing an efficient search strategy in the place navigation task, but once the goal was located, MDMA pretreated rats performed at control levels and showed no deficits in memory for spatial location. It is concluded that the extent of serotonergic denervation produced by MDMA is not sufficient to produce marked and lasting behavioral deficits, possibly because of neurocompensatory changes in the remaining serotonin terminals.