REPEATED COCAINE ADMINISTRATION DOES NOT AFFECT 5-HT RECEPTOR SUBTYPES (5-HT(1A), 5-HT2) IN SEVERAL RAT-BRAIN REGIONS

In order to examine whether cocaine-induced behavioral sensitization i s modulated by changes in serotonin receptor subtypes, we measured the binding of [H-3]8-hydroxy-2-(di-n-propylamino)tetralin ([H-3]8-OH-DPA T) to 5-HT1A receptors and of [H-3]ketanserin to 5-HT2 receptors in va rious brain regions of cocaine-treated and saline-treated (control) ra ts. As previously reported, repeated administration of cocaine resulte d in behavioral sensitization. Stereotypic scores with the cocaine cha llenge were significantly (P < 0.05) higher in cocaine-pretreated anim als than in the saline-pretreated group. Neither acute nor chronic coc aine administration significantly altered the number (B(max)) or the a ffinity (K(D)) of either [H-3]8-OH-DPAT or [H-3]ketanserin binding sit es in any of the brain regions examined. These results suggest that th e enhanced functional sensitivity of 5-HT1A or 5-HT2 receptor subtypes seen with cocaine may be associated with alterations in processes dis tal to receptors rather than changes in the number or the affinity of the receptors.