beta-Adrenoceptor blocking agents recognize a subpopulation of serotonin receptors in brain

The interaction of beta-adrenoceptor blocking agents with serotonin receptors in rat brain was analyzed by quantitative light microscopic autoradiography using (-) [125I]cyanopindolol (ICYP) as a ligand. In some brain areas such as the globus pallidus and dorsal subiculum, binding of ICYP was blocked with high affinity by some serotoninergic ligands, RU-24969 and serotonin, but not by lysergic acid diethylamide and 8-hydroxy-2-(N,N-di-n-propylamino)tetralin. Some beta-blockers also showed high affinity for these sites. These results supply direct evidence for the labeling of a subclass of serotonin receptors, the 5-HT-1B class, providing anatomical and pharmacological basis for some known serotonin-related effects of beta-adrenoceptor drugs.