侧脑室微量注射ghrelin对大鼠小肠转运的作用及其机制

Effect of intracerebroventricular injection of ghrelin on small intestinal transit in rats

目的探讨侧脑室微量注射ghrelin对大鼠小肠运动的作用及对中枢和胃肠道c-Fos表达的影响。方法 1给大鼠分别埋置十二指肠导管及侧脑室套管,禁食24h后经侧脑室微量注射生理盐水或ghrelin(0.4、1.6μg/kg或6.4μg/kg),经十二指肠导管注射伊文氏蓝溶液,观察不同剂量ghrelin对小肠转运的影响。另2组大鼠分别接受侧脑室注射ghrelin受体拮抗剂(D-Lys3)GHRP-6(3.7μg/kg)、(D-Lys3)GHRP-6(3.7μg/kg)+ghrelin(6.4μg/kg),探讨ghrelin对小肠转运的作用机制。2采用免疫组织化学和图像分析方法观察侧脑室注射ghrelin对大鼠中枢神经系统和肠神经系统c-Fos蛋白表达的影响,并观察(D-Lys3)GHRP-6对ghrelin作用的影响。结果 1侧脑室微量注射ghrelin 0.4μg/kg对大鼠小肠转运无显著影响,ghrelin 1.6μg/kg和6.4μg/kg可促进小肠转运,此作用被(D-Lys3)GHRP-6阻断。2侧脑室微量注射ghrelin可激活中枢多个部位的c-Fos蛋白表达,包括下丘脑弓状核、室旁核、下丘脑腹内侧核、杏仁内侧核、迷走神经背核等核团;胃、十二指肠、近端结肠的c-Fos表达增加,胃的c-Fos蛋白表达增加最显著。Ghrelin受体拮抗剂(D-Lys3)GHRP-6可抑制ghrelin激活的中枢神经系统和肠神经系统的c-Fos蛋白表达。结论侧脑室微量注射ghrelin促进大鼠小肠转运,其促动力作用可能通过受体GHSR介导。侧脑室微量注射ghrelin可通过中枢神经系统和肠神经系统调节小肠运动。

Objective To investigate the effects of ghrelin injected intracerebroventricularly on small intestinal mobility and on c-Fos expression in the enteric nervous system（ENS）and the central nervous system（CNS）.Methods 1 Rats received intraduodenal catheter and intracerebroventricular annular tube implantation.After fasting for 24 h,the rats received intracerebroventricular injection of ghrelin or normal saline（0.4,1.6,and6.4μg/kg,respectively）.Small intestinal transit was measured after injection of Evans blue through the intraduodenal catheter.The other two group of rats received ghrelin receptor antagonist（D-Lys3）GHRP-6（3.7μg/kg）or（D-Lys3）GHRP-6（3.7μg/kg）＋ghrelin（6.4μg/kg）.2 The c-Fos activation on the ENS and CNS through intracerebroventricular injection of ghrelin was studied by immunohistochemistry. Results 1 Ghrelin of 0.4 μg/kg injected intracerebroventricularly did not affect small intestinal transit obviously.However,ghrelin of 1.6 and 6.4μg/kg enhanced small intestinal transit and this effect was suppressed by its receptor antagonist（D-Lys3）GHRP-6.2 Intracerebroventricular injection of ghrelin could activate the expression of c-Fos in several CNS nuclei such as paraventricular nucleus,arcuate nucleus and ventromedial hypothalamic nucleus. Ghrelin also increased the expression of c-Fos in the stomach,duodenum and adjacent colon,especially the stomach.The receptor antagonist inhibited the effect of ghrelin.Conclusion Intracerebroventricular injection of ghrelin appears to have excitatory effects on small intestinal transit by regulating the intestinal motility through the CNS and ENS.Ghrelin receptor is involved in these activities.