title: Pharmacological analysis of histamine receptors in musculature and vasculature of the dog trachea in situ.
abstract: 1 The role of histamine H1- and H2-receptors in the musculature and vasculature of the dog trachea was investigated in the blood-perfused trachea in situ. 2 Histamine and acetylcholine caused increases in blood flow (tracheal, vasodilatation) and in intraluminal pressure (tracheal constriction) in a dose-dependent manner. Histamine was almost equipotent to acetylcholine in causing tracheal vasodilatation but was about 30 times less potent in causing tracheal constriction. 3 The histamine H2-receptor agonist, dimaprit, caused a dose-dependent increase in tracheal blood flow but failed to cause tracheal constriction. 4 The tracheal constriction produced by histamine was inhibited strongly by diphenhydramine but not modifed by metiamide. The tracheal vasodilatation produced by histamine was antagonized by both diphenhydramine and metiamide; diphenhydramine was more effective than metiamide. 5 It is concluded that in the tracheal musculature, histamine receptors are exclusively of the H1-type and mediate constriction, whereas in the tracheal vasculature, both histamine H1- and H2-receptors mediate vasodilatation but histamine H1-receptors are predominant.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D004155:Diphenhydramine / Q000494:pharmacology; D004285:Dogs; D005260:Female; D006632:Histamine / Q000494:pharmacology; D008297:Male; D008785:Metiamide / Q000494:pharmacology; D009130:Muscle, Smooth / Q000187:drug effects*; D010646:Phentolamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D011968:Receptors, Histamine / Q000187:drug effects*; D011969:Receptors, Histamine H1 / Q000187:drug effects; D011970:Receptors, Histamine H2 / Q000187:drug effects; D012039:Regional Blood Flow / Q000187:drug effects; D014132:Trachea / Q000098:blood supply / Q000187:drug effects*
chemical_list: D011968:Receptors, Histamine; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D008785:Metiamide; D001285:Atropine; D006632:Histamine; D004155:Diphenhydramine; D011433:Propranolol; D000109:Acetylcholine; D010646:Phentolamine