272 Neuroscience Letters, 85 (1988) 272 276 Elsevier Scientific Publishers Ireland Lid NSL 05144 Subtypes of adrenergic and dopaminergic receptors in bovine cerebral blood vessels Jacques De Keyser l, Guy Ebinger 1, Jean.Paul De Backer 2, Andre Convents 2, Patrick Vanderheyden 2 and Georges Vauquelin2 ~Department of Neurology, Akademisch Ziekenhuis, l/rije Universiteit Brussel, Brussels (Belgium) and 2Department of Protein Chemistry, Vr(je Universiteit Brussel, St. Genesius-Rode (Belgium) (Received 6 October 1987; Revised version received 2 November 1987; Accepted 2 November 1987) Key words: Adrenergic receptor; Dopaminergic receptor; Cerebral blood vessel; Bovine; Cerebral circu- lation Binding of the radiolabelled antagonists [3H]rauwolscine, [sH]SCH 23390 and (-)-[3H]dihydroalpreno- 1ol revealed the presence of ¢t2-adrenergic > DAI dopaminergic > p-adrenergic receptors in membrane prep- arations of calf basal cerebral arteries (basilar artery and circle of Willis) and pial vessels of the cerebral convexity. Computer-assisted analysis of ICI 118 551/(- )-[SH]dihydroalprenolol competition binding curves indicated the existence offl~- and fl2-adrenergic receptor subtypes ([32/fll ratio 7:3). No specific bind- ing of [3H]prazosin (to cq-adrenergic receptors) and [SH]spiroperidol (to DA2 dopaminergic receptors) was detected. Whereas DA~, fl~-and fl2-receptor densities were very similar in both blood vessel types, the ct2- receptor density was 3-fold higher in the pial vessels of the convexity. This suggests a functionally more important vasoconstrictor adrenergic control of the cerebral circulation in pial vessels of the convexity than in the arteries at the base of the brain. Cerebral blood vessels are richly innervated by sympathetic nerve fibers, which mainly originate from the superior cervical ganglia, and sympathetic stimulation in- duces a decrease in cerebral blood flow (CBF) [6, 11, 16, 17]. Norepinephrine pro- duces contraction of isolated cerebral blood vessels by acting on ct-adrenergic recep- tors, whereas isoprenaline provokes relaxation through ]/-receptor stimulation [5]. Although a direct innervation of cerebral blood vessels by dopaminergic nerve fibers has not been demonstrated, there is evidence that dopamine may also interact with specific receptors in the vessel wall. In the presence of both an ~- and fl-receptor blocker, dopamine and dopaminergic agonists cause relaxation of the isolated human basilar artery, and this effect can be prevented by a variety of dopamine receptor antagonists [7]. In this study we used radioligand binding techniques to identify and quantitate the subtypes of the adrenergic and dopaminergic receptors present in bo- vine basal cerebral arteries (BCA) and pial vessels from the cerebral convexity (PVC). Correspondence." J. De Keyser, Department of Neurology, A.Z. Vrije Universiteit Brussel, Laarbeeklaan 101, B-1090 Brussels, Belgium. 0304-3940/88/$ 03.50 © 1988 Elsevier Scientific Publishers Ireland Ltd.