Cocaine and serotonin: a role for the 5-HT 1A receptor site in the mediation of cocaine stimulant effects

Abstract

Cocaine induced locomotor stimulant effects are generally attributed to cocaine effects on brain dopamine. In this report, we present evidence that the 5-hydroxytryptamine 1A (5-HT 1A) agonist, 8-hydroxy-2-(di- n-propylamino)tetralin (8-OHDPAT) and the 5-HT 1A antagonist, N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]- N-2-pyridinyl-cycylhexanecarboxaminde maleate (WAY 100635) can enhance or block, respectively, the locomotor stimulant effects induced by cocaine. In two separate experiments, rats administered cocaine (10 mg/kg) exhibited a locomotor stimulant effect and decreased grooming behavior compared to saline treated rats. Pretreatment with the 5-HT 1A agonist, 8-OHDPAT (0.2 mg/kg) enhanced and pretreatment with the 5-HT 1A antagonist, WAY 100635 (0.4 mg/kg) eliminated the locomotor stimulant effect of cocaine. Neither the 8-OHDPAT nor WAY 100635 effects were attributable to effects on the behavioral baseline. The 8-OHDPAT and WAY 100635 had opposite effects on grooming behavior. 8-OHDPAT decreased and WAY 100635 increased grooming. Neither treatment, however, affected the grooming suppression induced by cocaine. Ex vivo biochemical measurements indicated that neither 8-OHDPAT or WAY 100635 affected brain dopamine metabolism or cocaine availability in brain. Both treatments affected 5-HT metabolism and altered the effect of cocaine on 5-HT metabolism. 8-OHDPAT increased and WAY 100635 decreased cocaine effects on 5-HT metabolism. Cocaine and 8-OHDPAT but not WAY 100635 increased corticosterone. Altogether, these findings indicate that the 5-HT 1A receptor site may be an important target for the development of pharmacotherapies for the treatment of cocaine abuse.