Distribution of (3)H-dopamine and (3)H-DAGO binding sites in the central part of rat sinoatrial node

Distribution of (3)H-dopamine and (3)H-DAGO binding sites was studied by autoradiography on semithin sections of total preparations of rat sinoatrial node. The relative density of (3)H-dopamine and (3)H-DAGO binding sites in the functional nucleus of the sinoatrial node was minimum and increased in the cranial and caudal directions. The level of (3)H-dopamine binding in the perinodal atrial myocardium was appreciably lower (22+/-6%), while binding of (3)H-DAGO was similar (76+/-16%) to that in the periarterial zone of the sinoatrial node.