NEUROPEPTIDE-Y STIMULATION OF INSULIN-SECRETION IS MEDIATED VIA THE NUCLEUS TRACTUS-SOLITARIUS

Neuropeptide-Y (NPY) is widely distributed in nervous tissue. In the c entral nervous system, NPY has been shown to be densely located in spe cific brain regions wherein it may mediate specific functions. Previou s data have indicated that NPY may act at a selective site in the brai n to modulate insulin secretion. In this study, we investigated the ef fect of NPY on NTS-mediated insulin secretion. A limited occipital cra niotomy was performed on anesthetized rats to expose the caudal medull a in the region of the obex. NPY was microinjected into the NTS and bl ood samples were subsequently collected from the femoral vein. NPY mic roinjection resulted in a significant increase in insulin secretion wi thin 5 minutes that returned to baseline at 30 minutes. However, micro injections of NPY did not significantly alter the plasma glucose in th is model system. We conclude that NPY can act directly on the NTS to i ncrease circulating insulin levels. Thus, the NTS may be a major brain stem site that directly mediates the central action of NPY on nutrient homeostasis.