Background: Alcohol inhibits colonic motility but the mechanism is unknown. The goal of this study was to test the possibility that nuclear factor-kappa B (NF-jB) is involved in the upregulation of inducible nitric oxide synthase (iNOS) expression induced by ethanol in colon.Methods: The isometric contraction of longitudinal muscle strips of proximal colon (LP) was monitored by polygraph. Western blot analysis was used to measure the amount of iNOS and I-jB in the cytoplasm and P65 in the nucleus. Immunohistochemistry was applied to locate iNOS in colon.Results: Ethanol (87mM) inhibited the contraction of LP. Pretreatment of S-methylisothioure (SMT) (1 mM), a specific iNOS inhibitor, Pyrrolidine dithiocarbamate (PDTC) (10 mM) and BAY11-7082(10 mM), specific inhibitors of NF-jB significantly reversed the inhibitory effect of ethanol on LP contraction. Ethanol increased the amount of iNOS and content of NO in colon, and these effects were attenuated by pretreatment of PDTC. Following ethanol administration, the amount of I-jB in the cytoplasm decreased, but that of P65, the subunit of NF-jB in the nucleus, increased. The iNOS was located in the cell body of myenteric plexus in colon.Conclusion: Ethanol inhibited the contraction of LP in colon mainly through activation of NF-jB, the subsequent upregulation of iNOS expression and increase of NO release in myenteric plexus.
The aim of the present study was to investigate the effect of oxytocin (OT) on duodenum motility in rats and the possibility that cholecystokinin (CCK) was involved in this process. The isometric contraction of longitudinal muscle strips of duodenum was monitored by polygraph. ELISA was used to measure the concentration of CCK and OT in duodenum. CCK mRNA was assayed by RT-PCR. Oxytocin receptor (OTR) and CCK in duodenum were located by immunohistochemistry and immunofluorescence staining. OT (10⁻⁵ and 10⁻⁶ M) inhibited the spontaneous contraction of the muscle strips. On the contrary, atosiban (OT receptor antagonist), lorglumide (CCK₁ receptor antagonist), and tetrodotoxin (TTX, blocker of voltage-dependent Na(+) channel on nerve fiber) excited the contraction. The inhibitory effect of OT on duodenal motility was reversed by pretreatment of atosiban, lorglumide, or TTX. Exogenous OT did not influence the expression of OT mRNA in duodenum but increased the concentration of CCK in the culture medium of the cells isolated from longitudinal muscle myenteric plexus. The OTR and CCK were co-expressed in the neurons of the myenteric plexus in duodenum. We concluded that OT inhibited the contraction of the LD spontaneous contraction of rats in vitro. This effect was mediated by the CCK released from the neurons of the myenteric plexus in duodenum.
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