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Endothelium‐dependent noradrenaline‐induced relaxation of rat isolated cerebral arteries: pharmacological characterization of receptor subtypes involved
Author(s) -
Hempelmann Ralf G.,
Ziegler Albrecht
Publication year - 1993
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1993.tb13963.x
Subject(s) - chemistry , atenolol , propranolol , endocrinology , medicine , methoxamine , cerebral arteries , prazosin , agonist , phentolamine , rauwolscine , schild regression , endothelium , isoprenaline , receptor , antagonist , stimulation , blood pressure
1 The endothelium‐dependence of catecholamine‐induced relaxation of rat cerebral arteries was investigated in vitro.2 In the basilar artery (BA), the maximal relaxant response was most pronounced with noradrenaline (NA), less with isoprenaline (Iso), and only very little with terbutaline. Methoxamine and the α 2 ‐adrenoceptor selective agonists BHT 933 and clonidine, had no relaxant effect. 3 In BA, the relaxation by NA or Iso was markedly attenuated by N ω ‐nitro‐ l ‐arginine ( l ‐NOARG) 10 −4 m . Short term perfusion of the vessels by Triton X 100 (1:1000) suppressed the NA‐induced relaxation. 4 The relaxation induced by NA or Iso was markedly reduced in presence of l ‐NOARG in the posterior, medial and anterior cerebral artery. 5 In BA, NA‐induced relaxation was non‐competitively inhibited by propranolol, atenolol, and the β 1 ‐ and β 2 ‐adrenoceptor selective antagonists, CGP 20712 A and ICI 118551. 6 The relaxant NA‐effect was not affected by prazosin but was non‐competitively blocked by phentolamine. 7 The Iso‐induced relaxation was competitively blocked by propranolol, whereas atenolol, CGP 20712 A and ICI 118551 caused a non‐competitive inhibition. 8 The experiments indicate that the catecholamine‐induced relaxation in rat isolated cerebral arteries depends upon the endothelium. They suggest that the NA‐induced relaxation of BA is mediated by different α‐ and β‐adrenoceptors and that the Iso‐induced relaxation is mediated by different β‐receptors. The findings would also be compatible with the idea of a receptor type which cannot be characterized by the pharmacological tools that we have used.