Ghrelin Regulates Feeding By Orexin And NPY Signaling Pathway In Rats

Objective: Ghrelin neurons are mainly distributed in the arcuate nucleus(ARC)of the hypothalamus.It is the only peripheral hormone found in the feeding center.Both ARC and the lateral hypothalamic area(LHA)are involved in the regulation of feeding and energy balance.The neurons expressing orexin are mainly distributed in LHA.Studies have found that there is a nerve fiber connection between ARC-LHA and ghrelin receptor expression in LHA.The purpose of this study was to investigate the effect of LHA injection of ghrelin on feeding in rats,and to explore whether this effect is related to orexin,MCH or NPY signaling pathway,in order to elucidate the feeding mechanism of ghrelin on rats.Methods: 1.Fluorescence immunohistochemical staining was used to observe the distribution of orixin,MCH and ghrelin immunopositive neurons in LHA and ARC of hypothalamus;2.Intra-injection of ghrelin into LHA,fluorescence immunohistochemical staining for the expression of c-fos in orientin or MCH immunopositive neurons in LHA;3.Effect of NPY antibody on the expression of c-fos in ghrelin-induced orexin neurons and MCH neurons by fluorescent immunohistochemical staining;4.LHA was injected into the mixture of orexin-A antibody,MCH antibody or NPY antibody,respectively,to observe its effect on ghrelin-induced feeding effect.Results: 1.Immunohistochemical staining showed that there was expression of ghrelin immunopositive neurons in the hypothalamic ARC.At the same time,the expression of orexin immunopositive neurons was observed in LHA.LHA injection of ghrelin can induce c-fos expression in oroxin-positive neurons in LHA,but no c-fos expression in MCH-positive neurons.2.If LHA was pre-injected with NPY antibody,LHA was injected with ghrelin 5 min later,and there was still c-fos expression in orexin-positive neurons in LHA.3.LHA injection of orexin-A antibody,MCH antibody or NPY antibody,then the 10% sucrose intake(P<0.05)and 0.1% maltose intake(P<0.05)of rats were significantly decreased within 2h.4.LHA was injected into normal goat serum,and ghrelin was injected 5 minutes later.The intake of 10% sucrose solution(P<0.05)and 0.1% saccharin solution(P<0.05)was significantly increased.LHA injection of orexin-A antibody + normal saline,MCH antibody + normal saline,or NPY antibody + normal saline,rat 10% sucrose solution(P<0.05)and 0.1% saccharin solution intake decreased(P <0.05);pre-LHA injection of orexin-A antibody,MCH antibody,or NPY antibody,after 5 min injection of ghrelin,the ghrelin effect on the sucrose solution and saccharin solution was significantly reduced(P <0.05).5.Intra-injection of orexin-A antibody,MCH antibody or NPY antibody into LHA significantly decreased the food and water intake of rats(P<0.05).6.Pre-injection of orexin-A antibody or NPY antibody in LHA significantly inhibited the ghrelin-induced feeding effect(P<0.05).However,pre-injection of MCH antibody into LHA resulted in no significant ghrelin-induced feeding effect.Change(P>0.05).7.Compared with NPY antibody + ghrelin group or orexin-A antibody + ghrelin group,LHA injected NPY antibody + orexin-A antibody,5 min after injection of ghrelin,ghrelin induced The reduction in feeding effect was more significant(P < 0.05),and the food intake was reduced by about 80%.Conclusion: There are orexin and ghrelin immunopositive neurons in the hypothalamus Arc and LHA;ghrelin can activate orexin and MCH neurons in LHA;In LHA,ghrelin promotes 10% sucrose solution,0.1% saccharin solution,food and water intake in rats,which may be related to activation of orexin or NPY signaling pathways,but orexin and NPY signaling pathways are involved in rat ghrelin-induced feeding regulation independently and in parallel.