Augmented accumbal serotonin levels decrease the preference for a morphineassociated environment during withdrawal

Recent studies have found that acute morphine administration increases sero tonin (5-HT) transmission within the nucleus accumbens and other forebrain regions. In contrast, 5-HT transmission is depressed during withdrawal from chronic morphine. We show that pharmacological agents that increase brain 5-HT levels (fluoxetine or 5-hydoxytryptophan, 5-HTP) abolish the preferenc e of chronically morphine-treated, withdrawn mts for a morphine-associated environment. Similar results were seen when fluoxetine was microinjected in to the nucleus accumbens. Conversely, rats given morphine acutely showed an enhanced preference for a morphine-associated environment when pretreated with these agents. Fluoxetine also decreased the heightened anxiety found i n morphine withdrawn rats. The results of our study indicate that drugs tha t augment 5-HT levels may reduce the desire for morphine during withdrawal. (C) 2000 American College of Neuropsychopharmacology. Published by Elsevie r Science Inc.