title: A possible physiological role of histamine H2-receptors in rat mesenteric circulation.
abstract: Dose-response curves of histamine were studied on the mesenteric circulation of the anaesthetized rat. The vasodilation produced by small doses of histamine was prevailingly H2-receptor-dependent, as shown by its inhibition by cimetidine but not by mepyramine, and by its reproducibility by some H2-receptor agonists, but not by specific H1-receptor agonists. The vasodilation produced by high doses of histamine was mainly due to stimulation of H1-receptors, as shown by its 70% inhibition by mepyramine. Mepyramine and cimetidine given simultaneously nearly completely inhibited the vasodilating action of high doses of histamine. Certain H2-receptor agonists, administered at high doses, induced a paradoxical vasoconstriction. It is suggested that a small number of H2-receptors is present in rat mesenteric arterioles, and that these receptors may play a physiological role in the control of mesenteric circulation.
mesh_terms: D000818:Animals; D002927:Cimetidine / Q000494:pharmacology; D017259:Dimaprit; D051381:Rats; D011919:Rats, Inbred Strains; D011968:Receptors, Histamine / Q000502:physiology*; D011970:Receptors, Histamine H2 / Q000187:drug effects / Q000502:physiology*; D013152:Splanchnic Circulation / Q000187:drug effects; D013844:Thiazoles / Q000494:pharmacology; D013890:Thiourea / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects
chemical_list: D011968:Receptors, Histamine; D011970:Receptors, Histamine H2; D013844:Thiazoles; C029345:2-(2-aminoethyl)thiazole; D002927:Cimetidine; D013890:Thiourea; D017259:Dimaprit