Short-term effects of 3,4-methylenedioximethamphetamine on noradrenergic activity in locus coeruleus and hippocampus of the rat

This study was undertaken to investigate the effects of the administration of 3,4-methylenedioxymethamphetamine (MDMA) on the locus coeruleus firing rate, on the sensitivity of the alpha(2)-adrenoceptors which regulate neuronal activity and on the in vivo tyrosine hydroxylase activity in hippocampus. The basal firing rate was not modified by either a single dose or repeated doses of MDMA, although the latter produced a shift to the right in the dose-response curve for clonidine-induced inhibition of the firing rate (ED50 increased by 59%) and a reduction in tyrosine hydroxylase activity (20%) in the hippocampus. However, 8 days after the final dose alpha(2)-adrenoceptor sensitivity and tyrosine hydroxylase activity had returned to control values. Our results show a desensitization Of alpha(2)-adrenoceptors in locus coeruleus and the existence of short-term changes in the noradrenergic system. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.