Published online Jan 15, 2003. doi: 10.3748/wjg.v9.i1.165
Revised: June 23, 2002
Accepted: July 3, 2002
Published online: January 15, 2003
AIM: 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 °C), bubbled continuously with 950 mL·L-1 O2 and 50 mL·L-1 CO2. Isometric spontaneous contractile responses to oxytocin or other drugs were recorded in circular and longitudinal muscle strips.
RESULTS: OT (0.1 U·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·L-1) decreased the mean contractile amplitude and the contractile frequency of CM and LM. Hexamethonium (10 μmol·L-1) partly blocked the inhibition of oxytocin (1 U·L-1) on the contractile frenquency of CM. Nω-nitro-L-arginine-methylester (L-NAME, 1 μmol·L-1), progesterone (32 μmol·L-1) and estrogen (2.6 μmol·L-1) had no effects on OT-induced responses.
CONCLUSION: 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.