Publicação: The possible involvement of hyperpolarizing mechanisms in histamine-induced relaxation of the rat portal vein
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2008-11-07
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The present study evaluated the effects of histamine 10 -2 M on longitudinal preparations of rat portal vein. It was observed that histamine 10 -2 M induced relaxation of rat portal vein preparations pre-contracted with phenylephrine 10 -4 M. On the other hand, no pharmacological effects were observed in preparations not pre-contracted. The observed histamine-induced relaxing effect was absent in preparations pre-contracted with KCl (120 mM) or in the presence of depolarizing nutritive solution. However, the histamine-induced relaxation was still present in the endothelium-removed preparations. The histamine-induced relaxation also was not prevented by astemizole (10 -6 M, 10 -5 M and 10 -4 M), cimetidine (10 -5 M, 10 -4 M and 10 -3 M) or thioperamide (10 -6 M, 10 -5 M and 10 -4 M), selective antagonists H 1, H 2 and H 3, respectively. The presence of L-NAME 10 -4 M or L-NAME 10 -4 M plus indomethacin 10 -5 M also did not prevent the histamine-induced relaxation observed in rat portal vein. Thus, the histamine-induced relaxation observed in rat portal vein appears to involve a non-endothelial hyperpolarizing mechanism independent of H 1, H 2 and H 3 receptors.
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Endothelium, Histamine, Hyperpolarizing mechanism, Portal vein, Relaxation, astemizole, enzyme inhibitor, histamine, histamine agonist, histamine H1 receptor, histamine H1 receptor antagonist, n(g) nitroarginine methyl ester, phenylephrine, potassium chloride, vasoconstrictor agent, animal, animal model, dose response, drug effect, male, physiology, portal vein, rat, vasodilatation, Wistar rat, Animals, Astemizole, Dose-Response Relationship, Drug, Enzyme Inhibitors, Histamine Agonists, Histamine H1 Antagonists, Non-Sedating, Male, Models, Animal, NG-Nitroarginine Methyl Ester, Phenylephrine, Portal Vein, Potassium Chloride, Rats, Rats, Wistar, Receptors, Histamine H1, Vasoconstrictor Agents, Vasodilation
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Inglês
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Journal of Smooth Muscle Research, v. 44, n. 3-4, p. 129-141, 2008.
