Characterization of vascular histamine receptors in the rat.
1 In the rat the decrease in blood pressure caused by histamine involves activation of both H1- and H2-receptors. Since arterial pressure measurements alone do not permit the separation of responses into cardiac and vascular components, the following experiments were undertaken to study vascular histamine receptors. 2 Vascular responses were studied in the autoperfused hindquarters of anaesthetized rats. Intra-arterial histamine caused vasodilatation which was only partially attenuated by treatment with mepyramine, an H1-receptor antagonist. Treatment with metiamide, the H2-receptor antagonist, did not affect vasodilatation caused by histamine but did attenuate vasodilatation which persisted after mepyramine. 3 Intra-arterial 4-methylhistamine, an H2-receptor agonist, caused vasodilatation which was reduced by metiamide. The H1-receptor agonist, 2-(2-pyridyl)ethylamine also caused vasodilatation which was blocked by mepyramine. 4 It is concluded that in the rat, histamine causes vasodilatation mediated by both H1- and H2-receptors.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D006635:Histamine H2 Antagonists / Q000494:pharmacology; D008297:Male; D051381:Rats / Q000502:physiology*; D011968:Receptors, Histamine / Q000032:analysis*; D011969:Receptors, Histamine H1 / Q000032:analysis* / Q000502:physiology; D011970:Receptors, Histamine H2 / Q000032:analysis* / Q000502:physiology; D014664:Vasodilation
D006634:Histamine H1 Antagonists; D006635:Histamine H2 Antagonists; D011968:Receptors, Histamine; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2