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AIM:To investigate the effects of oxytocin(OT)on isolatedrabbit proximal colon and its mechanism.METHODS:Both longitudinal muscle(LM)and circularmuscle(CM)were suspended in a tissue chamber containing5 mL Krebs solution(37 ℃),bubbled continuously with950 mL.L~(-1)O_2 and 50 mL·L~(-1)CO_2.Isometric spontaneouscontractile responses to oxytocin or other drugs wererecorded in circular and longitudinal muscle strips.RESULTS:OT(0.1 U·L~(-1))failed to elicit significant effectson the contractile activity of proximal colonic smooth musclestrips(P>0.05).OT(1 to 10 U·L~(-1))decreased the meancontractile amplitude and the contractile frequency of CMand LM.Hexamethonium(10 μmol·L~(-1))partly blocked theinhibition of oxytocin(1 U·L~(-1))on the contractile frenquencyof CM.N~ω-nitro-L-arginine-methylester(L-NAME,1 μmol·L~(-1)),progesterone(32 μmol·L~(-1))and estrogen(2.6 μmol.L~(-1))hadno effects on OT-induced responses.CONCLUSION:OT inhibits the motility of proximal colon inrabbits.The action is partly relevant with N receptor,butirrelevant with that of NO,progesterone or estrogen.
AIM: To investigate the effects of oxytocin (OT) on isolatedrabbit proximal colon and its mechanism. METHODS: Both longitudinal muscle (LM) and circularmuscle (CM) were suspended in a tissue chamber containing 5 mL Krebs solution mL.L ~ (-1) O_2 and 50 mL·L -1 CO_2.Isometric spontaneous contractile responses to oxytocin or other drugs wererecorded in both circular and longitudinal muscle strips.RESULTS: OT (0.1 U · L -1) ) failed to elicit significant effects of the contractile activity of proximal colonic smooth musclestrips (P> 0.05) .OT (1 to 10 U · L -1) decreased the meancontractile amplitude and the contractile frequency of CMand LM. Hexamethonium (10 μmol · L -1) partly blocked the inhibition of oxytocin (1 U · L -1) on the contractile frenquency of CM.N ~ ω-nitro-L-arginine-methylester (L-NAME, 1 μmol·L (-1) and 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, butirrelevant with that of NO, progesterone or estrogen.