CHRONIC D-FENFLURAMINE DECREASES SEROTONIN TRANSPORTER MESSENGER-RNA EXPRESSION IN DORSAL RAPHE NUCLEUS

In situ hybridization was used to measure the effects of chronic fenfl uramine adminstration on serotonin transporter messenger RNA expressio n in cells of the dorsal raphe nucleus complex. Fenfluramine produced a significant, but transient, down-regulation of serotonin transporter mRNA in cells which lie in the ventral portion of the dorsal raphe nu cleus, but not in the dorsal part of the dorsal raphe nucleus. Our fin dings suggest that cells which lie in the ventral part of the dorsal r aphe nucleus are more sensitive to the effects of chronic fenfluramine administration, but that fenfluramine does not cause long-term change s in gene expression in serotonin cell bodies.