Abstract
We studied the role of several serotonin (5-HT) and histamine receptors in the regulation of human umbilical artery (HUA) contractility. Among the 5-HT agonists used, only the 5-HT( 2A) and 5HT(1B/D) agonists contracts HUA. The 5-HT-induced contractions were fully inhibited by ketanserin (5-HT(2A) antagonist). The 5-HT( 7)-activation also relaxes and increases intracellular cyclic adenosine monophosphate (cAMP). Among the histamine receptor agonists, only betahistine (H(1) agonist) induced significant contractile effect. Histamine-induced contraction was partially relaxed by pyrilamine (H(1) antagonist). Betahistine-induced contraction was partially blocked by dimaprit (H( 2) agonist) and by the H(3) agonist when a low concentration of forskolin is present. Both, H(2) and H(3) agonists increased the cAMP intracellular levels in HUA smooth muscle. These findings show that in HUA, 5-HT(2A)- and 5-HT(1B/1D)-activation lead to vasoconstriction and 5-HT(7)-activation induces vasorelaxation. Concerning histamine receptors, H(1)-activation induces contraction and H(2)- and H(3)-activation lead to vasorelaxation.
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