H1- and H2-receptors in the smooth muscle of the ruminant stomach.
1 The effects of histamine on the longitudinal and circular smooth muscle from the rumen and reticulum of the bovine stomach have been analyzed by the use of H1- and H2-receptor antagonists. 2 Histamine caused three different types of response of the smooth muscle preparations: a contraction, contraction followed by relaxation, and a relaxation. These responses were resistant to the effect of tetrodotoxin, atropine, combined treatment with alpha- and beta- adrenoceptor blocking agents, hexamethonium and also to guanethidine. 3 Mepyramine antagonized the contractile responses and metiamide antagonized the relaxation responses in a highly selective and competitive manner. 4 It is concluded that histamine-induced excitatory and inhibitory responses of the smooth muscles from the bovine forestomach are mediated by histamine H1- and H2-receptors, respectively.
D000818:Animals; D002417:Cattle; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D008785:Metiamide / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D011738:Pyrilamine / Q000494:pharmacology; D011968:Receptors, Histamine / Q000187:drug effects*; D011969:Receptors, Histamine H1 / Q000187:drug effects*; D011970:Receptors, Histamine H2 / Q000187:drug effects*; D013279:Stomach, Ruminant / Q000187:drug effects*
D011968:Receptors, Histamine; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D008785:Metiamide; D006632:Histamine; D011738:Pyrilamine