Dual effect of clonidine on mesenteric artery adrenoceptors: Agonistic (alpha-2) and antagonistic (alpha-1)

Dual effect of clonidine on mesenteric artery adrenoceptors: Agonistic (alpha-2) and antagonistic (alpha-1)

Author Silva, Eneida de Gusmão Autor UNIFESP Google Scholar
Feres, Teresa Autor UNIFESP Google Scholar
Vianna, Lucia Marques Autor UNIFESP Google Scholar
Okuyama, Paulo Akinori Autor UNIFESP Google Scholar
Paiva, Therezinha Bandiera Autor UNIFESP Google Scholar
Institution Universidade Federal de São Paulo (UNIFESP)
Abstract The effect of clonidine on the mesenteric vascular bed and the isolated mesenteric artery was examined in preparations in which tonus was induced by norepinephrine or endothelin. In preparations precontracted by norepinephrine, clonidine caused a relaxation which was not inhibited by the alpha-2 antagonists yohimbine and idazoxan or by the K+ channel blockers apamine, tetraethylammonium and glibenclamide. In preparations precontracted with endothelin, clonidine increased the depolarization and induced a contraction. Both these effects were inhibited by prazosin. In isolated mesenteric arteries, norepinephrine caused a significant depolarization that was inhibited by clonidine or prazosin. On the other hand, clonidine caused a hyperpolarization which was inhibited by idazoxan or yohimbine, but not by prazosin. This hyperpolarization was also abolished by apamine, tetraethylammonium and glibenclamide. It is concluded that clonidine acts on alpha-1 adrenoceptors as a partial agonist, causing relaxation of the mesenteric artery precontracted with norepinephrine or contraction of preparations precontracted with endothelin. Moreover, clonidine can open K+ channels and hyperpolarize the plasma membrane of mesenteric artery by acting on alpha-2 adrenoceptors.
Language English
Date 1996-05-01
Published in Journal Of Pharmacology And Experimental Therapeutics. Baltimore: Williams & Wilkins, v. 277, n. 2, p. 872-876, 1996.
ISSN 0022-3565 (Sherpa/Romeo, impact factor)
Publisher Williams & Wilkins
Extent 872-876
Origin http://jpet.aspetjournals.org/content/277/2/872
Access rights Closed access
Type Article
Web of Science ID WOS:A1996UJ95300039
URI http://repositorio.unifesp.br/11600/44570

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