Atypical (relaxant) response to histamine in cat bronchus.
Histamine, 2-methylhistamine (a specific H1-receptor agonist), 4-methylhistamine (a specific H2-receptor agonist), isoprenaline, bradykinin, prostaglandin E1, E2, and F 2alpha  induce relaxation of carbachol-contracted isolated cat bronchial strips and tracheal chains. Bovine SRS-A contracts bronchus but not trachea. Histamine-induced relaxation of cat bronchus is not blocked by mepyramine (a specific H1-receptor antagonist); metiamide or burimamide (specific H2-receptor antagonists); propranolol ( a beta-adrenoceptor blocker) and indomethacin (a PG-synthetase inhibitor) suggesting non-participation of H1,H2-histamine receptors, beta-adrenoceptors (catecholamine release) and prostaglandin release in histamine-induced broncho-relaxations in the cat. The existence of an atypical histamine response, resistant to both H1- and H2-receptor antagonists is thus established in cat bronchus.
D000403:Airway Resistance / Q000187:drug effects*; D000818:Animals; D001980:Bronchi / Q000187:drug effects; D002049:Burimamide / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D002415:Cats; D005260:Female; D006632:Histamine / Q000031:analogs & derivatives / Q000494:pharmacology*; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D006635:Histamine H2 Antagonists / Q000494:pharmacology; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D008785:Metiamide / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects; D011433:Propranolol / Q000494:pharmacology; D011738:Pyrilamine / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects
D006634:Histamine H1 Antagonists; D006635:Histamine H2 Antagonists; D008785:Metiamide; D006632:Histamine; D002217:Carbachol; D011433:Propranolol; D011738:Pyrilamine; D002049:Burimamide; D007213:Indomethacin