3,4-Methylenedioxymethamphetamine-induced release of serotonin and inhibition of dorsal raphe cell firing: potentiation by L-tryptophan
Sprouse JS, Bradberry CW, Roth RH, Aghajanian GK.
Department of Psychiatry,
Yale University School of Medicine,
New Haven, CT 06508.
Eur J Pharmacol 1990 Mar 27;178(3):313-20
ABSTRACTThe effects of the serotonin (5-HT) precursor L-tryptophan on MDMA (3,4-methylenedioxymethamphetamine)-induced inhibition of dorsal raphe neuronal firing were characterized using extracellular single-unit recording and microdialysis techniques in the in vitro midbrain slice preparation. Pretreatment with L-tryptophan (100 microM) lowered the doses of MDMA required to inhibit unit activity. Based upon IC50 values, L-tryptophan increased the potency of MDMA by approximately 3-fold. In a parallel series of experiments, microdialysis probes resting on the brain slice surface provided a means to estimate 5-HT release from the dorsal raphe nucleus. Pretreatment with L-tryptophan increased MDMA-induced 5-HT release in a manner consistent with the suppression of dorsal raphe cell firing: compared to untreated preparations, peak 5-HT release, total release and the duration of release were all increased. Taken together, these data suggest that the enhancement by L-tryptophan of MDMA-induced 5-HT release and inhibition of dorsal raphe neuronal firing is due to an increase in the amount of 5-HT available for release. The question is raised as to what effect L-tryptophan may have on the psychotropic and neurotoxic actions of MDMA.History
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