title: Characterization of muscarinic receptors in canine bronchial smooth muscle.
abstract: Rings of canine bronchi were suspended for isometric tension recording. Contractions produced by exogenously added acetylcholine were inhibited by pirenzepine and pancuronium. The pKB values were 6.76 for pirenzepine (calculated at 10(-6) M) and 5.30 and 5.13 for pancuronium (calculated at 10(-5) and 3 X 10(-5) M, respectively). Contractile responses evoked by cholinergic nerve stimulation (0.2-16 Hz, 9 V) were depressed by pancuronium in a concentration-dependent manner, while concentrations of pirenzepine selective for M1-muscarinic receptors were without effect. The results indicate that exogenous and nerve-released acetylcholine activate a homogenous population of M2-muscarinic receptors in isolated preparations of canine bronchial smooth muscle.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001980:Bronchi / Q000187:drug effects; D004285:Dogs; D004558:Electric Stimulation; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D010197:Pancuronium / Q000494:pharmacology; D010275:Parasympathetic Nervous System / Q000502:physiology; D010890:Pirenzepine / Q000494:pharmacology; D011976:Receptors, Muscarinic / Q000187:drug effects*
chemical_list: D011976:Receptors, Muscarinic; D010890:Pirenzepine; D010197:Pancuronium; D000109:Acetylcholine