title: Effect of oxytocin on contraction of rabbit proximal colon in vitro.
abstract: OBJECTIVE
  To investigate the effects of oxytocin (OT) on isolated rabbit proximal colon and its mechanism.
  
  
  METHODS
  Both longitudinal muscle (LM) and circular muscle (CM) were suspended in a tissue chamber containing 5 mL Krebs solution (37 degrees ), bubbled continuously with 950 mL x L(-1) O(2) and 50 mL x L(-1) CO(2). Isometric spontaneous contractile responses to oxytocin or other drugs were recorded in circular and longitudinal muscle strips.
  
  
  RESULTS
  OT (0.1 U x L(-1)) failed to elicit significant effects on the contractile activity of proximal colonic smooth muscle strips (P>0.05). OT (1 to 10 U x L(-1)) decreased the mean contractile amplitude and the contractile frequency of CM and LM. Hexamethonium (10 micromol x L(-1)) partly blocked the inhibition of oxytocin (1 U x L(-1)) on the contractile frenquency of CM. N(omega))-nitro-L-arginine-methylester (L-NAME, 1 micromol x L (-1)), progesterone (32 micromol x L(-1)) and estrogen (2.6 micromol x L(-1)) had no effects on OT-induced responses.
  
  
  CONCLUSIONS
  OT inhibits the motility of proximal colon in rabbits. The action is partly relevant with N receptor, but irrelevant with that of NO, progesterone or estrogen.
authors.affiliation: Department of Physiology, School of Medicine, Shandong University, Jinan 250012, Shandong Province, China.
authors.forename: Dong-Ping
authors.initials: DP
authors.lastname: Xie
authors.forename: Lian-Bi
authors.initials: LB
authors.lastname: Chen
authors.forename: Chuan-Yong
authors.initials: CY
authors.lastname: Liu
authors.forename: Jing-Zhang
authors.initials: JZ
authors.lastname: Liu
authors.forename: Ke-Jing
authors.initials: KJ
authors.lastname: Liu
mesh_terms: D000818:Animals; D003106:Colon / Q000187:drug effects* / Q000502:physiology; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D004967:Estrogens / Q000378:metabolism / Q000494:pharmacology; D005260:Female; D005769:Gastrointestinal Motility / Q000187:drug effects* / Q000502:physiology; D018738:Hexamethonium / Q000378:metabolism / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D019331:NG-Nitroarginine Methyl Ester / Q000378:metabolism / Q000494:pharmacology; D018733:Nicotinic Antagonists / Q000378:metabolism / Q000494:pharmacology; D010121:Oxytocin / Q000378:metabolism / Q000494:pharmacology*; D011374:Progesterone / Q000378:metabolism / Q000494:pharmacology; D011817:Rabbits
chemical_list: D004791:Enzyme Inhibitors; D004967:Estrogens; D018733:Nicotinic Antagonists; D018738:Hexamethonium; D011374:Progesterone; D010121:Oxytocin; D019331:NG-Nitroarginine Methyl Ester