p-Chloroamphetamine (PCA), 3,4-methylenedioxymethamphetamine (MDMA) andd-fenfluramine pretreatment attenuatesd-fenfluramine-evoked release of 5-HT in vivo

Abstract

Previous work has suggested that repeated treatment with substituted amphetamines including PCA, MDMA andd-fenfluramine produces a persistent neurodegeneration which is relatively selective for the fine serotoninergic terminals arising from the dorsal raphe nucleus. The aim of the present study was to investigate whether the acute releasing effect ofd-fenfluramine might also be sensitive to lesions produced by PCA, MDMA andd-fenfluramine itself. Basal and 5-HT release evoked byd-fenfluramine or 100 mM KCl was measured by microdialysis in frontal or parietal cortex of rats 2 weeks after they had been treated with a neurodegenerative regime of PCA, MDMA,d-fenfluramine, or vehicle. In frontal cortex of vehicle controls,d-fenfluramine (10 mg/kg IP) and KCl (100 mM via microdialysis probe) evoked an increase in 5-HT of 1740% and 779% of basal, respectively. PCA pretreatment reducedd-fenfluramine-evoked 5-HT release by 90.9% while potassium-evoked release was reduced by only 66.8%. Similar results were obtained in parietal cortex. MDMA (20 mg/kg×8) andd-fenfluramine (12.5 mg/kg×8) pretreatment reducedd-fenfluramine-evoked release of 5-HT in frontal cortex by 45.2% and 72.0%, respectively. Overall, the present data are consistent with the hypothesis that the acute release of 5-HT evoked byd-fenfluramine occurs via those terminals destroyed by pretreatment with PCA, MDMA andd-fenfluramine, while KCl evokes release from both PCA-sensitive and PCA-insensitive terminals. The significance of these results for the interpretation of neuroendocrine data fromd-fenfluramine challenge tests is discussed.