title: Inhibitory effects of sildenafil citrate on the tonus of isolated dog internal anal sphincter.
abstract: OBJECTIVE
  Although the exact pathogenesis of anal fissure is not known, hypertonicity of the internal anal sphincter might be involved in its pathogenesis as main event. To gain information about possible usefulness of the novel, smooth-muscle-relaxing drug, sildenafil, in chronic anal fissure, we investigated the effect of sildenafil citrate on acetylcholine-induced contractility of internal anal sphincter isolated from dogs.
  
  
  METHODS
  Internal anal sphincter strips were taken from German shepherd dogs and suspended in a tissue bath filled with Krebs solution at 37 degrees C (pH 7.4) continuously bubbled with 95 percent oxygen and 5 percent carbon dioxide, and isometric contractions were recorded. Contractions were evoked by 10 muM acetylcholine, and the effects of different concentrations of sildenafil citrate (0.1, 0.3, and 1 mM) on the isometric tension of each internal anal sphincter strip were examined. The statistical significance was analyzed by one-way analysis of variance.
  
  
  RESULTS
  Pretreatment with sildenafil citrate (0.1 mM) attenuated contractile response to acetylcholine (n = 3), which were significantly weak compared with the maximum contractile response to the acetylcholine alone (610 +/- 110 mg vs. 2,825.17 +/- 416 mg; n = 12; P < 0.05). Sildenafil citrate also significantly inhibited the acetylcholine-induced contractions in a dose-dependent manner when applied after.
  
  
  CONCLUSIONS
  This experimental in vitro study showed that sildenafil citrate relaxes acetylcholine stimulated contractions of isolated dog internal anal sphincter. This may be of importance for raising the possibility that sildenafil cit-rate may have future potential in the treatment of chronic anal fissure. Further studies are needed for a conclusive decision on possible usefulness of sildenafil citrate in patients with chronic anal fissure.
authors.affiliation: Department of Surgery, Firat University School of Medicine, Elazig, Turkey.
authors.forename: Erhan
authors.initials: E
authors.lastname: Aygen
authors.forename: Cemalettin
authors.initials: C
authors.lastname: Camci
authors.forename: Ali Sait
authors.initials: AS
authors.lastname: Durmus
authors.forename: Osman
authors.initials: O
authors.lastname: Dogru
authors.forename: Omer
authors.initials: O
authors.lastname: Topuz
authors.forename: Refik
authors.initials: R
authors.lastname: Ayten
authors.forename: Ahmet
authors.initials: A
authors.lastname: Ayar
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000037:antagonists & inhibitors*; D000109:Acetylcholine / Q000008:administration & dosage / Q000494:pharmacology; D001003:Anal Canal / Q000187:drug effects*; D000818:Animals; D018678:Cholinergic Agents / Q000008:administration & dosage / Q000494:pharmacology; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D007537:Isometric Contraction / Q000187:drug effects; D009129:Muscle Tonus / Q000187:drug effects*; D010276:Parasympatholytics / Q000008:administration & dosage / Q000494:pharmacology*; D010726:Phosphodiesterase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D010879:Piperazines / Q000008:administration & dosage / Q000494:pharmacology*; D011687:Purines; D000068677:Sildenafil Citrate; D013450:Sulfones
chemical_list: D018678:Cholinergic Agents; D010276:Parasympatholytics; D010726:Phosphodiesterase Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D000068677:Sildenafil Citrate; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D000109:Acetylcholine