Effect of MDMA neurotoxicity upon its conditioned place preference and discrimination.

Experiments were conducted to investigate the functional consequences of a neurotoxic regimen of MDMA administration upon two behaviors, conditioned place preference and drug discrimination. Rats were trained to discriminate 1.5 mg/kg MDMA from its vehicle and their discriminative performance was shown to be dose-responsive. Subsequently, MDMA was observed to produce a conditioned place preference as three conditioning sessions with 1.5 mg/kg MDMA paired with the nonpreferred chamber increased the time the rats spent in the chamber paired with MDMA. Administration of a proportedly neurotoxic dose (20 mg/kg subcutaneous) of MDMA, twice-a-day for four days, did not affect this conditioned place preference when it was redetermined at a time of maximal neurochemical compromise. In contrast, sensitivity to 1.0 mg/kg MDMA in the drug discrimination task was shown to be significantly decreased after the neurotoxic regimen. Results are discussed in light of MDMA effects upon both central serotonergic and dopaminergic neurons.