Effect Of Ghrelin On Hypothalamic Glucose Responding Neurons In Rats

Background: Ghrelin, 28 amino acid acylated peptide, is an endogenous ligand for growth hormone secretagogue receptor (GHS-R). It regulates the release of growth hormone (GH) from pituitary. Recent physiological studies show that ghrelin plays an important role in the control of food intake and energy homeostasis, which does not depend on the release of GH. For example, intracerebroventricular injection of ghrelin strongly stimulated feeding in rats and increased body weight gain. Ghrelin is synthesized in stomach and arcuate nucleus (ARC) which project to many regions of brain involved in feeding regulation that contain GHS-R, such as ventromedial hypothalamic nucleus (VMH), paraventricular nucleus (PVN). VMH has been termed as "satiety center"; pPVN is included in the suppressing mechanism of feeding. The activity of glucose-sensitive neurons (GSNs) in the parvocellular part of paraventricular nucleus (pPVN) can be inhibited by glucose applied directly to their surface, and glucoreceptor neurons (GRNs) in VMH can be stimulated by glucose. Both GSNs and GRNs are responsible for controlling feeding behavior and weight. These neurons are susceptible to several hormones such as insulin, TRH, leptin, orexin, etc. The present study was undertaken to examine the effect of ghrelin on hypothalamic glucose responding neurons in rats. Object: To investigate the effect of ghrelin on glucose responding neurons in VMH and pPVN and the possible mechanism by which ghrelin controls feeding and energy homeostasis.Method: Electrophysiological method and micro-pressure injection. Results: Ghrelin inhibited 82% (27/33) GRNs and 69% (9/13) GSNs in VMH and pPVN, respectively. [D-Lys-3]-GHRP-6 antagonized the effect of ghrelin. Conclusion: The results of present experiments indicate that ghrelin may inhibit the...