EFFECTS OF CHRONIC COCAINE ADMINISTRATION ON THE SEROTONERGIC SYSTEM IN THE RAT-BRAIN

Male Sprague-Dawley rats received injections of cocaine (20 mg/kg/dose , IP) every 12 h for 14 days and were sacrificed on the 15th day. The chronic cocaine treatment caused an increase in the levels of serotoni n [5-hydroxytryptamine (5-HT)] and its metabolite 5-hydroxyindoleaceti c acid (5-HIAA) in the hippocampus. 5-HIAA levels in the frontal corte x were also increased, but 5-HT levels were unaltered by the chronic c ocaine treatment. Similarly. striatal levels of 5-HT and 5-HIAA were u nchanged by repeated administration of cocaine. Chronic cocaine admini stration did not alter the density of [H-3]8-OH(PAT), [H-3]mesulergine , or [H-3]ketanserin binding in the hippocampus, choroid plexus, and f rontal cortex, respectively. Furthermore, repeated injection of cocain e did not alter serotonergic-mediated inhibition of adenylate cyclase activity. Thus, repeated administration of cocaine causes region-speci fic alterations in 5-HT levels but does not change the properties of t he 5-HT1A, 5-HT1C, or 5-HT2 receptors.