NPY AND GALANIN IN A HIBERNATOR - HYPOTHALAMIC GENE-EXPRESSION AND EFFECTS ON FEEDING

Neuropeptides such as neuropeptide Y (NPY) and galanin may play a role in regulating the pronounced seasonal changes in food intake shown by golden-mantled ground squirrels (Spermophilus saturatus). We used in situ hybridization histochemistry to localize the expression of NPY an d galanin mRNA in the hypothalamus of normally feeding animals. NPY mR NA was abundantly expressed in the arcuate nucleus, while galanin mRNA was concentrated in both the arcuate nucleus and the dorsomedial nucl ei. When NPY (0.1, 0.5, 2, and 8 mug) or galanin (0.1, 0.5, 2, and 8 m ug) were injected into the third cerebral ventricle, food intake was s ignificantly and dose-dependently increased over the subsequent 30 min . NPY stimulated significant increases in food intake for up to 2 h wh ereas galanin's effect did not extend beyond 30 min. Our results sugge st that hibernating and nonhibernating rodents share common neural sub strates for the regulation of food intake. Seasonal modulation of thes e neural pathways may contribute to annual cycles of food intake in hi bernating mammals.