Selective labeling of 5-HT1A and 5-HT1B binding sites in bovine brain

Drug interactions with serotonin(1A) 5-HT1A and serotonin(1B) (5-HT1B) binding sites were analyzed in bovine brain membranes. 5-HT1A binding sites were directly labeled with [3H]8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT) in bovine hippocampal membranes. 5-HT1B 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-HT1A than 5-HT1B binding site. 5-HT, bufotenine, N,N-dimethyltryptamine (DMT) and quipazine were only slightly more potent at the 5-HT1A 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-HT1A, and 5-HT1B binding sites have distinct pharmacological profiles and can be directly labeled with appropriate [3H]ligands in specific brain regions.