Ghrelin In, And Obestatin On Spatial Learning And Memory Abilities

Background Ghrelin is the endogenous ligand of the growth hormone secretagogue receptor(GHS-R),which was found by Kojima.Many experiments found that ghrelin can stimulate growth hormone secretion,food intake and increase body weight.Because ghrelin was secreted by the stomach mucosa A cell in hungry,most of the experiments focus on its effect which initiated ingestion and regulated energy balance.Recently it is reported that cerebroventricular and periphery injection ghrelin can stimulate the rat'learning and memory ability.Obestatin,a novel peptide encoded by the same gene with ghrelin.Most of its reports were debated.ZHANG reported that cerebroventricular and periphery injection obestatin can all suppress ingestion。But there were also experiments found that ghrelin can pass the blood-brain barrier by special transport system,but obestatin can not and it can be cleared quickly.HOLST did not confirm that obestatin bind to GPR39.GOURCEROL found intraperitoneal injection obestatin did not affect the food intake.The effect of obestatin on study and memory was reported by CARLINI.Elevated plus maze and step down test found obestatin can improves memory performance and causes anxiolytic effects in rats.Objective To explore the effects of ghrelin and obestatin on the ability of learning and memory.Methods Rats were randomly divided into 6 groups:ghrelin high dose,low dose and saline; obestatin high dose,low dose and saline.Saline and different doses of ghrelin were given by micro-injection into the hippocampus CA3;saline and different dose of obestatin were given randomly by lateral cerebroventricular injection(icv).Ability of learning and memory was tested by Morris water maze.Results The latency of swimmimg time and distance in the high ghrelin group were decreased significantly compared with that in the control group.In the probe test,the rats of the high ghrelin group stayed longer time and the swimming distance in the ever quadrant were longer than that of the control group.The results tested obestatin showed no differece compared with control group in the hiding platform test and the probe test. Conclusion Micro-injection of ghrelin into the hippocampus has an effect of improving the ability of learning and memory in rats.icv injection of obestatin has no effect on the ability of learning and memory in rats.