The Effect Of AP Ghrelin On The Gastric Motility In Cisplatin-treated Rats And The Regulation By The Lateral Hypothalamic Area

Ghrelin,a 28 amino acid peptide,is mainly produced by the stomach and expressed in the peripheral tissues as well as the central nervous system.Ghrelin has gradually attracted the attention of scholars because it has a range of biological activities such as promoting digestive motility and secretion,accelerating growth hormone(GH)release,and regulating metabolism and energy homeostasis.In recent years,we have done a lot of work in the central ghrelin neural pathway and its regulation on the gastrointestinal motility.However,there were few studies on the relationship between ghrelin and gastrointestinal dysfunction.The purpose of this study is to investigate the effect of AP ghrelin on the gastric motility in the cisplatin-treated rats and the regulation by the lateral hypothalamic area(LHA).The main contents and results are as follows:1.The expression of ghrelin and GHSR-1a in the gastric tissue of rats was detected by immunohistochemical method.The results showed that ghrelin and GHSR-1a positive cells were found in the rat stomach.The expression of ghrelin was decreased while the expression of GHSR-1a was increased in the cisplatin-treated rats.The ELISA,Western blot and PCR were used to measure the changes of ghrelin and its receptor GHSR-1a in the plasma and stomach.The results suggested that,compared with the saline-treated rats,the average concentration of ghrelin in plasma of cisplatin-treated rats decreased slightly without statistical significance(P>0.05);the average concentration of ghrelin in the gastric homogenate decreased significantly(P<0.05).Compared with the saline-treated rats,the expression of ghrelin in the stomach of cisplatin-treated rats was decreased at the levels of protein and mRNA without statistical significance(P>0.05);while the expression of GHSR-1a was increased(P<0.05).2.The composition of the ghrelin neural pathway between LHA-AP and the effect of cisplatin on the pathway were investigated by retrograde tracing combined with fluoro-immunohistochemical staining.The results suggested that there was a ghrelin neural pathway between LHA-AP,and cisplatin could reduced the ghrelin neuron projections in the nerve pathway.The Western blot and PCR were used to measure the changes of ghrelin and GHSR-1a expressions in the AP and LHA.The results suggested that,compared with the saline-treated rats,the expression of ghrelin in the AP and LHA of cisplatin-treated rats was significantly decreased at the protein and mRNA levels(P<0.05),while the expression of GHSR-1a was increased significantly at protein and mRNA levels(P<0.05-0.01).3.The effects of AP ghrelin and LHA stimulation on the gastric motility in cisplatin-treated rats were observed by nuclei microinjection,NMDA stimulating the LHA,gastric motility recording and extracellular discharge recording methods.The results showed that GD sensitive neurons could be recorded in the AP of rats.The discharge frequency of GD neurons increased significantly after ghrelin administrated into the AP(P<0.01),an effect completely blocked by treatment with the ghrelin receptor antagonist [D-Lys-3]-GHRP-6.NMDA in the LHA excited most of ghrelin-responsive gastric distension(GD)-sensitive neurons in the AP(P<0.01),and this effect was partially blocked by treatment with the ghrelin receptor antagonist [D-Lys-3]-GHRP-6.Cisplatin weakens the gastric motility of rats(P<0.01).Ghrelin administrated into the AP significantly promoted the gastric motility(P<0.05-0.01),an effect completely blocked by treatment with [D-Lys-3]-GHRP-6.NMDA in the LHA promoted gastric motility and this effect was partially blocked by treatment with [D-Lys-3]-GHRP-6(P<0.01).Electrical lesion of the AP diminished the excitatory effect on the gastric motility that was induced by the stimulation of the LHA.Furthermore,these excitatory effects in the cisplatin-treated rats were weaker than those in the saline-treated rats(P<0.05).In conclusion,these results of this study confirmed that AP ghrelin can promote gastric motility in rats.There was a ghrelin neural pathway between LHA-AP which participates in the regulation of gastric motility.This regulation on gastric motility was weaker in the cisplatin-treated rats than in the saline-treated rats,possibly duing to the reduced ghrelin expression in the LHA and ghrelin projection from the LHA to the AP.The above results can provide reference for the discovery of ghrelin as a new target for anti-vomiting drug.