Selective labeling of 5-HT 1A and 5-HT 1B binding sites in bovine brain

Abstract

Drug interactions with serotonin(1A) 5-HT 1A and serotonin(1B) (5-HT 1B) binding sites were analyzed in bovine brain membranes. 5-HT 1A binding sites were directly labeled with [ 3H]8-hydroxy-2-(di- n-propylamino)-tetralin (8-OH-DPAT) in bovine hippocampal membranes. 5-HT 1B binding sites were labeled by [ 3H]5-HT in bovine striatal membranes where less than 15% of specific binding sites are sensitive to nanomolar concentrations of 8-OH-DPAT. Each of the 12 agents tested was more potent at the 5-HT 1A than 5-HT 1B binding site. 5-HT, bufotenine, N,N-dimethyltryptamine (DMT) and quipazine were only slightly more potent at the 5-HT 1A binding site. By contrast, 8-OH-DPAT, TVX Q 7821 and buspirone were significantly more potent at [ 3H]8-OH-DPAT binding sites in bovine hippocampus than at [ 3H]5-HT binding sites in bovine striatum. These findings suggest that 5-HT 1A and 5-HT 1B binding sites have distinct pharmacological profiles and can be directly labeled with appropriate [ 3H]ligands in specific brain regions.