Reversed response to histamine following local anaphylaxis in blood-perfused calf trachea in situ.
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.
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*
D006633:Histamine Antagonists; D006632:Histamine; D002217:Carbachol