title: Effect of substance P on the lower esophageal sphincter of the opossum.
abstract: Since the original observations by Von Euler and Gaddum, considerable interest has developed regarding the role of substance P in smooth muscle function. The purpose of the present investigation was to evaluate the effect of intravenously administered substance P on the vivo motor function of the lower esophageal sphincter (LES). Intraesophageal pressures were monitored by an assembly of polyvinyl catheters attached to pressure transducers and a recorder. The catheters were continuously perfused with bubble-free water. Administration of 5, 10, 25, 50, and 100 ng per kg of substance P stimulated the LES, respectively, 16, 32, 57, 147, and 169% above control values. Tetrodotoxin, phentolamine, hexamethonium, methysergide, and bilateral cervical vagotomy did not alter the response of the LES to substance P. Atropine in 40-, 250-, and 500-microgram per kg doses significantly but partially inhibited the response of the LES to substance P. It is concluded that subtance P is a potent stimulant of the LES. The stimulatory effect of substance P may involve both cholinergic muscarinic and noncholinergic mechanisms. It is conceivable that substance P may be a modulator of LES pressure, although the exact physiological significance is not clear at the present time.
mesh_terms: D000818:Animals; D001285:Atropine / Q000494:pharmacology; D004943:Esophagogastric Junction / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006584:Hexamethonium Compounds / Q000494:pharmacology; D008297:Male; D008365:Manometry; D008784:Methysergide / Q000494:pharmacology; D009893:Opossums; D010646:Phentolamine / Q000494:pharmacology; D013373:Substance P / Q000494:pharmacology*; D014628:Vagotomy; D014630:Vagus Nerve / Q000502:physiology
chemical_list: D006584:Hexamethonium Compounds; D013373:Substance P; D001285:Atropine; D008784:Methysergide; D010646:Phentolamine