Abstract: Objective: To investigate the effects of glucocorticoid on neuropeptide Y(NPY) gene expression of the hypothalamus in obese and nonobese rats.Methods: Obese rat model was established by high-fat diet.Both the obese and nonobese rats were randomly assigned to normal saline(NS) group,low dose and high dose of glucocorticoid groups,and were administered intraperitoneal injection with normal saline 0.2 ml/100 g,hydrocortisone sodium succinate 5 mg/kg and 15 mg/kg,respectively,for 20 days.Their food intake was measured.Real-time quantitative PCR was used to measure the expression of NPY mRNA in the hypothalamus of the rats.Results: After high dose of glucocorticoid injection,the food intake of the obese and nonobese rats was lower than that of the NS group(P<0.05);the mRNA expressions of NPY in the hypothalamus of the obese and nonobese rats was lower than that of the NS group(P<0.01);the expression of NPY mRNA of the nonobese rats in the low dose group was significantly lower than that of the NS group(P<0.01).Conclusions: High dose of glucocorticoid may inhibit the appetite and the NPY mRNA expression in the hypothalamus of the obese and nonobese rats;low dose of glucocorticoid can inhibit the NPY mRNA expression in the hypothalamus of nonobese rats.NPY plays an important role in regulation of the appetite of rats.