title: The role of nitric oxide in the acetylcholine-induced relaxation of the feline internal anal sphincter, in vitro.
abstract: BACKGROUND
  The relaxatory effect of acetylcholine was investigated on the feline internal anal sphincter (IAS), in vitro.
  
  
  RESULTS
  Acetylcholine (10, 30, 100, and 1000 microM) caused a concentration-dependent relaxation of the same magnitude in strips from the proximal and distal IAS. The antagonist of nitric oxide synthase, N omega-nitro-L-arginine (L-NNA; 1, 10, and 100 microM), in a concentration-dependent and stereospecific manner, blocked the acetylcholine-induced relaxation, leaving a residual response of 10-30%. The blocking effect of L-NNA (100 microM) could not be shown in tissues that had been incubated with the substrate for nitric oxide synthase, L-arginine (1 mM).
  
  
  CONCLUSIONS
  The present results suggest that the acetylcholine-induced relaxation of the IAS to a major extent is due to an activation of nitrergic, inhibitory motor neurons to the IAS.
authors.affiliation: Dept. of Surgery, University of Göteborg, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Buntzen
authors.forename: S
authors.initials: S
authors.lastname: Nordgren
authors.forename: L
authors.initials: L
authors.lastname: Hultén
authors.forename: D
authors.initials: D
authors.lastname: Delbro
mesh_terms: D000109:Acetylcholine / Q000008:administration & dosage / Q000494:pharmacology*; D001003:Anal Canal / Q000187:drug effects / Q000294:innervation; D000818:Animals; D002415:Cats; D046508:Culture Techniques; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005260:Female; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects* / Q000502:physiology; D009569:Nitric Oxide / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D009569:Nitric Oxide; D000109:Acetylcholine