The Mechanism Of Y-aminobutyric Acid Regulated Appetite By Vagus Nerve

Gamma-aminobutyric acid(GABA)is the main inhibitory neurotransmitter in the central nervous system.GABA in the brain mainly promotes appetite by acting on neuropeptide Y(NPY)and agouti gene-related protein(AgRP)neurons and pro-opiomelanocortin(POMC)neurons.Exogenous GABA can not pass the blood-brain barrier,mainly by regulating related appetite hormones to regulate appetite.Previous studies found that the vagus nerve on the intestines is also involved in appetite regulation,exogenous substances can regulate the appetite through the vagus nerve on the intestines,activate the nucleus tractus solitarius and arcuate nucleus of the hypothalamus.But it is not clear that exogenous GABA regulates appetite through the peripheral vagus nerve and the related mechanism of action.Therefore,in this study,immunohistochemistry and fluorescence quantitative PCR were used to investigate whether exogenous GABA can regulate appetite and its related mechanism through peripheral vagus nerve.This experiment intends to study the effect of the combination of GABA and GABARA on appetite,and choose Bicuculline as an inhibitor of GABARA.Immunohistochemistry and fluorescence quantitative PCR were used to find the expression levels of GABARA,GAT2,GLP-1,synapsin-1,NPY,POMC and c-fos positive cells of the dorsal nucleus of the vagus nerve.Detection of co-localized expression of GABARA and GLP-1 by immunofluorescence dual-label method.Through the vagal nerve stem cutting experiment,the effect of vagus nerve on GABA on the expression levels of NPY,POMC and c-fos positive cells was studied.The research results are as follows.1.In order to select the appropriate GABA dosage,the control group,10mg/kg GABA group,30mg/kg GABA group and 50mg/kg GABA group were set up and the rats were gavaged for 5 weeks.The study found that GABA mice fed 30mg/kg were significantly higher in food intake and body weight than the Control group,10mg/kg GABA and 50mg/kg GABA(p<0.05).There was no difference between 10mg/kg GABA and Control group(p>0.05).Compared with the control group,50 mg/kg GABA significantly increased the intake and weight of mice in the early period of gavage(p<0.05),but in the late period of gavage,it was found that there was no difference in the intake and weight of mice compared with the control group(p>0.05).Therefore,30mg/kg GABA was selected as the intragastric dose in subsequent experiments.2.In order to study the effect of GABA on the appetite and body weight of mice,the control group,GABA group,GABA+Bicuculline group were established in this experiment,and gavage was given for 6 weeks.Bicuculline is an inhibitor of GABARA.In the GABA+Bicuculline group,intraperitoneal injection of 4mg/kg Bicucullin was given intraperitoneally with GABA at the fourth week.The study found that the food intake and body weight of the GABA group increased significantly compared with the Control group(p<0.05).3 weeks before gavage,the food intake of the GABA+Bicuculline group increased significantly compared with the Control group(p<0.05),and there was no difference compared with the GABA group(p>0.05),but after the injection of the inhibitor,The food intake of mice in the Bicuculline+GABA group was significantly lower than that in the GABA group(p<0.05).3.Through immunohistochemistry and fluorescence quantitative PCR studies,it was found that the expression of GABARA,GAT2,and synapsin-1 positive cells in the jejunal tissue of the GABA group increased significantly compared with the Control group(p<0.05),while GLP-1 was positive Cell expression decreased significantly(p<0.05).After the injection of Bicuculline,it was found that the expression of GABARA,GAT2,and synapsin-1 positive cells in the jejunal tissue of the 4mg/kg Bicuculline+GABA group was significantly lower than that of the GABA group(p<0.05),while GLP-1 positive cells expressed The amount increased significantly(p<0.05).Immunofluorescence double labeling found that GABARA and GLP-1 had co-localized expression,and GLP-1 was also expressed on intestinal endocrine cells expressing GABARA.4.Immunohistochemistry and fluorescence quantitative PCR study found that the expression levels of NPY and nucleus fascicularis nucleus and c-fos positive cells in the hypothalamic arcuate nucleus of GABA group were significantly higher than those in Control group(p<0.05),while the expression of POMC-positive cells in the arcuate nucleus of the hypothalamus decreased significantly(p<0.05).However,after the injection of Bicuculline,it was found that the expression levels of positive cells in the hypothalamic arcuate nucleus NPY,nucleus fascicularis nucleus,and c-fos of the dorsal nucleus in the 4mg/kg Bicuculline+GABA group were significantly lower than those in the GABA group(p<0.05),While the expression level of POMC-positive cells in the arcuate nucleus of the hypothalamus increased significantly(p<0.05).5.In order to study the effect of vagus nerve on GABA regulating appetite and body weight in mice.The Control group,the sham operation group,the sham operation+GABA group,the vagus nerve cut+GABA group were established,and the rats were gavaged for 6 weeks.After cutting the vagus nerve trunk with GABA,it was found that compared with the sham operation group,the food intake and body weight of the mice in the sham operation+GABA group increased significantly(p<0.05),while the food intake of the vagus nerve cuts+GABA group mice Compared with the weight and sham operation+GABA group,both decreased significantly(p<0.05).6.After cutting the vagus nerve trunk and gavage,it was found that the expression levels of positive cells in the hypothalamic arcuate nucleus NPY,nucleus fascicularis,and c-fos of the dorsal nucleus of the vagus nerve were significantly lower than those in the sham operation+GABA group(p<0.05),While the expression of POMC-positive cells in the arcuate nucleus of the hypothalamus increased significantly(p<0.05).Compared with the sham operation group and the sham operation group,the expression levels of positive cells in the hypothalamic arcuate nucleus NPY,solitary tract nucleus,c-fos of the dorsal nucleus of the vagus nerve were significantly increased(p<0.05),and the hypothalamic arcuate nucleus The expression level of POMC positive cells decreased significantly(p<0.05).In summary,in the intestine,exogenous GABA may be transported by GAT2 to endocrine cells of the intestinal wall,and after combining with GABARA,it inhibits the secretion of GLP-1 by intestinal endocrine cells and promotes the expression of synapsin-1 in the intestine,thereby further passing the vagus nerve activates the solitary tract nucleus and dorsal nucleus of the brainstem.The nucleus tract and dorsal nucleus of the vagus nerve promote the NPY of the arcuate nucleus of the hypothalamus by projecting fibers and inhibit the expression of POMC,thereby increasing appetite.This provides a new mechanism for exogenous GABA to regulate appetite,and also has important significance for further understanding and understanding the role of the brain-gut axis in appetite regulation.