Time-dependent effects of neuropeptide Y infusion in the paraventricular hypothalamus on ingestive and associated behaviors in rats.

In this study the role of neuropeptide Y (NPY) in the paraventricular nucleus of the hypothalamus (PVN) in the daily regulation of feeding, drinking, locomotor activity, and nestbox occupation was investigated. These behaviors were recorded during and after bilateral infusion of NPY into the PVN of rats during the early (E) or late (L) part of the light phase. Administration of NPY caused a significant increase in feeding behavior at E, but not at L. In contrast to the feeding at E, L feeding was associated with increased water intake following NPY infusion. While locomotor activity was similar in sCSF- and NPY-infused rats at all times of the daily cycle, administration of NPY at L, but not at E increased nestbox occupation during the first few hours of the dark phase. This increased nestbox occupation was not associated with altered food intake or drinking behavior, implying that NPY-treated rats made frequent excursions between nestbox and food hopper/water bottle. Thus, feeding-associated drinking and explorative behavior are time-dependently modulated by NPY in the PVN, independent of locomotor activity.