title: Histamine H1- and H2-receptors in pulmonary and systemic vasculature of the dog.
abstract: This study was conducted to identify and clarify the actions of pulmonary and systemic H1- and H2-receptors by utilizing specific histamine receptor antagonists. Histamine was infused in anesthetized dogs during control conditions, after H2-receptor blockade with metiamide, after H1-receptor blockade with chlorpheniramine, and after combined H1- and H2-receptor blockade. Histamine infusion, alone, induced marked systemic vasodilatation, pulmonary vasoconstriction, and transient increases in cardiac output and heart rate. H2-receptor blockade prevented the systemic vasocilatation and potentiated the pulmonary vasoconstriction induced by histamine. H1-receptor blockade augmented the systemic vasodilatation, prevented the pulmonary vasoconstriction, and increased the cardiac output and heart rate responses induced by histamine. Thus, H2-receptors appear to mediate the vasocilatation, tachycardia, and increased cardiac output induced by histamine, whereas H1-receptors appear to mediate the vasoconstrictor and the minimal cardiac depressent actions of histamine. Histamine stimulates only H1- and H2-receptors, since combined H1- and H2-receptor antagonism prevented almost all of the cardiovascular actions of histamine.
mesh_terms: D000818:Animals; D001775:Blood Circulation / Q000187:drug effects*; D002302:Cardiac Output / Q000187:drug effects; D002744:Chlorpheniramine / Q000494:pharmacology; D004285:Dogs; D006168:Guinea Pigs; D006339:Heart Rate / Q000187:drug effects; D006632:Histamine / Q000494:pharmacology / Q000502:physiology*; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008168:Lung / Q000098:blood supply; D008785:Metiamide / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D011652:Pulmonary Circulation / Q000187:drug effects*; D011955:Receptors, Drug / Q000187:drug effects; D014655:Vascular Resistance / Q000187:drug effects*; D014666:Vasomotor System / Q000187:drug effects*
chemical_list: D006634:Histamine H1 Antagonists; D011955:Receptors, Drug; D008785:Metiamide; D002744:Chlorpheniramine; D006632:Histamine; D011433:Propranolol; D007545:Isoproterenol