Autoradiographic localization of vascular dopamine receptors

By using combined in vitro radioreceptor binding and autoradiographic techniques, the pharmacological profile and the anatomical localization of dopamine-1 (DA-1) and dopamine-2 (DA-2) receptors were assessed in rat cerebral, mesenteric and renal arteries. 3H-SCH 23390 (DA-1 ligand) was bound by the medial layer of cerebral, mesenteric and renal arteries without different density in large, medium and small sized arteries. Moreover, 3H-SCH 23390 binding sites were not sensitive to chemical sympathectomy, suggesting postjunctional localization of DA-1 receptors. 3H-Spiroperidol (DA-2 ligand) was bound primarily by the adventitial, the adventitial-medial border as well as by the intimal layer of cerebral, mesenteric and renal arteries. The accumulation of adventitial and adventitial-medial 3H-spiroperidol binding sites was higher in medium and small sized arteries than in large ones and was remarkably reduced after chemical sympathectomy. These results show prejunctional localization of DA-2 receptors and further suggest that some DA-2 binding sites are located in the arterial intima.