title: Reversed response to histamine following local anaphylaxis in blood-perfused calf trachea in situ.
abstract: Tracheas of calves were perfused via the tracheal artery in situ. An endotracheal tube recorded tracheal muscle contractions. Carbachol, histamine or antigen caused tracheal vascular depressor responses. Carbachol caused contraction; histamine, 2-methylhistamine and antigen relaxed the tracheal muscle. Following antigen challenge, vascular responses remained unchanged; however endotracheal relaxations to histamine were reversed (i.e. contractions). Allergenic 'challenge' impairs H2-receptors (airway relaxation), thus diminishing a compensatory mechanism which may relate to hyperresponsiveness characteristic of asthma.
mesh_terms: D000707:Anaphylaxis / Q000503:physiopathology*; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002417:Cattle; D006632:Histamine / Q000494:pharmacology*; D006633:Histamine Antagonists / Q000494:pharmacology; D006736:Horses / Q000276:immunology; D066298:In Vitro Techniques; D014132:Trachea / Q000503:physiopathology*
chemical_list: D006633:Histamine Antagonists; D006632:Histamine; D002217:Carbachol