Alpha-2 adrenoceptors are present in rat aorta smooth muscle cells, and their action is mediated by ATP-sensitive K+ channels

Alpha-2 adrenoceptors are present in rat aorta smooth muscle cells, and their action is mediated by ATP-sensitive K+ channels

Author Fauaz, Grasiele Google Scholar
Feres, Teresa Google Scholar
Borges, Antonio CR Autor UNIFESP Google Scholar
Paiva, Therezinha B. Autor UNIFESP Google Scholar
Institution Universidade Federal de São Paulo (UNIFESP)
Abstract 1 the role of alpha (2)-adrenoceptors in the response of aorta smooth muscle rings to the alpha (2)- adrenoceptors agonists UK 14,304 and clonidine was studied.2 Stimulation by 1-10 nM UK 14,304 caused dose-dependent relaxant responses in BaCl2-contracted endothelium-denuded aorta rings, and hyperpolarization in rings with or without endothelium. which were inhibited by yohimbine and glibenclamide, but not affected by prazosin, propranolol, apamin or iberiotoxin. At higher concentrations (10 nM- 10 muM) UK 14,304 also induced a depolarizing effect which was potentiated by yohimbine and inhibited by prazosin. These results indicate that UK 14,304 acts on alpha (2)-adrenoceptors at lower concentrations and on both alpha (1)- and alpha (2)-adrenoceptors above 10 nM.3 in rings, with or without endothelium, noradrenaline had a depolarizing effect which was inhibited by prazosin. Adrenaline did not affect the membrane potential but in the presence of prazosin caused hyperpolarization, which was inhibited by yohimbine and glibenclamide. These results indicate that noradrenaline is more selective for alpha (1)-, whereas adrenaline has similar affinities for alpha (1)- acid alpha (2)-adrenoceptors.4 in aortae with endothelium, L-NNA caused a small depolarization but did not affect the hyperpolarization induced by UK 14,304, indicating that NO is not involved in that response.5 Glibenclamide induced a small depolarization in aortae, with or without endothelium, indicating that ATP-sensitive K+ channels may play a role in maintaining the smooth muscle's membrane potential.6 Our results indicate that, in rat aorta, alpha (2)-adrenoceptors are also present in the smooth muscle, and that these receptors act through small-conductance ATP-sensitive K+ channels.
Keywords rat aorta
membrane potential
alpha-2 adrenoceptor
ATP-sensitive K+ channel
UK 14,304
Language English
Date 2000-10-01
Published in British Journal of Pharmacology. Basingstoke: Nature Publishing Group, v. 131, n. 4, p. 788-794, 2000.
ISSN 0007-1188 (Sherpa/Romeo, impact factor)
Publisher Nature Publishing Group
Extent 788-794
Origin http://dx.doi.org/10.1038/sj.bjp.0703630
Access rights Open access Open Access
Type Article
Web of Science ID WOS:000090037100020
URI http://repositorio.unifesp.br/handle/11600/26388

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