Effect of oxytocin on contraction of rabbit proximal colon in vitro.
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.
Xie
Dong-Ping
DP
Department of Physiology, School of Medicine, Shandong University, Jinan 250012, Shandong Province, China.
Chen
Lian-Bi
LB
Liu
Chuan-Yong
CY
Liu
Jing-Zhang
JZ
Liu
Ke-Jing
KJ
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
D004791:Enzyme Inhibitors; D004967:Estrogens; D018733:Nicotinic Antagonists; D018738:Hexamethonium; D011374:Progesterone; D010121:Oxytocin; D019331:NG-Nitroarginine Methyl Ester