| Objective:To investigate the central and peripheral effects of endogenous Orexin-A on gastric motility in rats.Methods:Selecting 286 adult Wistar rats for the study, the synthesis of endogenous Orexin-A was induced by fasting. Plasma Orexin-A concentration was measured by radioimmunoassay. Rats were pretreated with Orexin-A receptor antagonist SB-334867 prior to measurement to observe the effect of Orexin-A.Vagotomy was used to observe vagus nerve-mediated effects. Gastric emptying was measured by spectrophotometric methods. One strain gauge transducers were attached on the antrum to record interdigestive gastric motility. Preproorexin(PPO) expression in stomach and hypothalamus were tested by Western blot. Orexin-A immunoreactivity in antrum was determined with immunohistochemistry.Results:Fasting could induce the synthesis of endogenous Orexin-A.Compared with feeding group, the level of plasma Orexin-A of 18 h fasting group significantly increased(P <0.05), the highest level appeared in 36 h fasting group(P <0.01). Endogenous Orexin-A promoted gastric emptying(P <0.05), inhibited gastric interdigestive motility(P <0.05). Compared with feeding group, PPO protein expression of stomach and hypothalamus tissues in 36 h fasting group was significantly increased(P <0.05). As these effects were abolished with injection of SB-334867, but no effect on PPO expression. Vagotomy surgery did not block endogenous Orexin-A-mediated effects(P> 0.05). Immunohistochemistry showed that, compared with feeding group, after 36 h fasting Orexin-A immunoreactive nerve cells in stomach was significantly increased.Conclusions:Fasting can induce the synthesis of endogenous Orexin-A. Endogenous Orexin-A can accelerate gastric emptying, but it suppressed interdigestive gastric motility. |
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