Central Y4 Receptor Distribution

A large variety of different neuropeptides function as central transmitters in neuronal circuits regulating diverse aspects of energy homeostasis such as feeding behavior, energy expenditure, and thermoregulation. Neuropeptide Y (NPY) represents one such peptide mediating behavioral and homeostatic alterations favoring positive energy balance (1 ). Thus, direct application of NPY into the hypothalamic paraventricular nucleus (PVN) or adjacent perifornical area (PeF) elicits a powerful orexigenic response leading most species to eat even in the satiated state (2 ,3 ). Application of NPY to these central sites also switches the tone of the autonomic nervous system in favor of a parasympathetic tone, leading to lowered energy expenditure and insulin secretion (4 ,5 ). Central administration also lowers body core temperature, but the exact site(s) and mode of action underlying this effect are largely unknown. Given the involvement of medial preoptic and hypothalamic ventromedial neurons in body temperature regulation, the numerous NPY-containing terminals within these forebrain areas are possible mediators of temperature-regulating actions of NPY.