DISSOCIATED FEEDING AND HYPOTHERMIC EFFECTS OF NEUROPEPTIDE-Y IN THE PARAVENTRICULAR AND PERIFORNICAL HYPOTHALAMUS

The present study investigated the effects of neuropeptide Y (NPY) on food intake and body temperature (T-bo) in free-feeding unrestrained rats following injection into the medial hypothalamic paraventricular nucleus (PVN) or the lateral perifornical hypothalamus (PFH). NPY (78-235 pmol) or saline was infused unilaterally into the PVN or PFH in a volume of 0.4 mu l and simultaneous measures of food intake and Tbo were taken every 30 min for 3 h. Results indicated that NPY evoked changes in eating behavior and T-bo that were dependent upon the site of hypothalamic injection. Although PVN and PFH administration of NPY both increased food intake dose dependently within 30 min of treatment, PFH NPY-injected rats (n = 9) showed a stronger behavioral response compared to rats (n = 9) receiving NPY injections into the PVN. In PVN-treated rats, however, the increased eating was associated with a significant decline in T-bo evident within the first 30-min test interval. A mean maximal decline of 0.92 +/- 0.26 degrees C occurred within 90 min of PVN treatment of the highest dose, which produced a reduction in T-bo that was maintained for 2.5 h. In contrast, NPY infusion into the PFH failed to reliably alter T-bo at any of the doses tested. These findings are consistent with evidence that NPY in the PVN and PFH may have distinct functions and suggest that although PFH NPY acts to stimulate a robust and relatively specific ingestive response, PVN NPY may participate in the complex integrative mechanisms responsible for the simultaneous regulation of feeding, thermoregulatory, and metabolic processes.