SOME ACUTE EFFECTS OF INTRACEREBROVENTRICULAR NEUROPEPTIDE-Y ON INSULIN-SECRETION AND GLUCOSE-METABOLISM IN THE RAT

Acute administration of neuropeptide Y(NPY) into the hypothalamus and cerebral ventricles can stimulate insulin secretion in the absence of available food. However, the relationship of this effect to blood gluc ose and other hormones which regulate glucose metabolism remains uncle ar. The purpose of this study was to compare the effects of NPY inject ed into the third ventricle (ICV) on serum insulin, glucose, glucagon, corticosterone and non-esterified fatty acids. Studies were performed on conscious, unrestrained female rats, not given access to food. ICV NPY, 2 and 5 mu g produced an increase in serum insulin and glucagon, while the 5 mu g dose only increased plasma glucose transiently and i ncreased non-esterified fatty acids for a longer period. Corticosteron e was not affected by ICV NPY. The insulinaemic response to i.v. gluco se, 0.5 g/kg was doubled by ICV NPY, 4 mu g. The maximal insulin level s were 113+/-18 for ICV NPY versus 67+/-8 mu U/ml for ICV saline-treat ed animals. The glycaemic response was not altered. The hypoglycaemic response to i.v. insulin, 0.15 U/kg was significantly attenuated by IC V NPY, 5 mu g. We concluded that ICV NPY promotes insulin secretion in the absence of available food and may potentiate the insulinaemic res ponse to hyperglycaemia. Furthermore, possibly through its effects on glucagon and non-esterified fatty acids, ICV NPY may decrease the abil ity of insulin to control glucose metabolism.