Effects of lactation, lactation-cessation and lactation-cessation-lactation paradigms on hypothalamic orexin-A immunoreactive neurons in rats / 生理学报

Orexin-A is a novel neuropeptide produced by neurons mainly located in lateral hypothalamic area that potently facilitates appetite and food intake. The purpose of this study was to investigate the possible change in orexin-A immunoreactivity in suckling-induced hyperphagia. By using immunohistochemistry and image analysis techniques we examined orexin-A-like immunoreactivity in a series of rat brain sections corresponding to the hypothalamus in groups of non-lactating, lactating, lactating with overnight cessation of suckling, lactating and cessation followed by resumed short-term sucklings. Long-term lactation significantly increased daily food intake on day 3 (81%) and day 11 (180%) postpartum compared to that in non-lactating postpartum rats, whereas daily food intake was significantly decreased by overnight cessation of suckling on day 11 postpartum in long-term lactating rats (45%). Moreover, long-term lactating rats on day 12 postpartum exhibited significantly greater number and higher mean staining intensity of orexin-A immunoreactive neurons than those of non-suckling postpartum rats (P<0.001 and P<0.05, respectively). Overnight cessation of lactation in rats on day 12 postpartum significantly decreased both the number and mean staining intensity of orexin-A immunoreactive neurons compared to those in long-term lactating group of rats (P<0.001 and P<0.05, respectively), similar to the levels in the non-lactating postpartum rats. Resumed lactation for 2 and 5 h after overnight cessation of lactation significantly increased the number (P<0.001 and P<0.05, respectively) and mean staining intensity (P<0.05) of orexin-A immunoreactive neurons compared to those in the rats without resumed lactation. Both long-term lactation and short-term resumed suckling enhanced orexin-A immunoreactivity in the hypothalamus in rats, and overnight cessation of lactation down-regulated the increased orexin-A immunoreactivity induced by long-term lactation. Suckling may regulate orexin-A expression in the hypothalamus and the increased orexin-A may be involved in hyperphagia in lactating rats, suggesting the possibility of the existence of some neural-humoral links between suckling and hypothalamic orexin-A-immunoreactive neurons.

The effect of blood glucose variation on gastric emptying and ghrelin expression in diabetic rats / 中华消化杂志

Objective To study the effect of blood glucose variation on gastric emptying and ghrelin expression in diabetic rats,and to explore the relationship between the delayed gastric emptying and the ghrelin expression in different diabetic stages.Methods Sixty Wistar rats were randomly divided into three groups:a normal control group(NC group),a diabetes mellitus group (DM group) induced by intra- peritoneal injection of streptozotocin (STZ),and an insulin-treated group (INS group).After one and four weeks the gastric emptying was measured by intragastric administration of phenol red and the expression of gastric ghrelin was determined by immunohistochemistry and semi-quantitative RT PCR.Results After one week of STZ injection,the gastric emptying,the ghrelin integral optical density and the ghrelin mRNA expression decreased significantly in DM group compared to those in NC group and INS group(P0.05).Conclusion Short term hyperglycemia delay gastric emptying through the reduction of gastric ghrelin expression,while long-term hyperglycemia may enhance the expression and release of gastric ghrelin to stimulate food intake and maintain energy balance.