NEUROPEPTIDE-Y TREATMENT AND FOOD-DEPRIVATION INCREASE CYCLIC-AMP RESPONSE ELEMENT-BINDING IN RAT HYPOTHALAMUS

Intrahypothalamic (IHT) administration of neuropeptide Y (NPY) induces a robust feeding response in rats. We have shown previously that NPY- induced feeding is mediated by a pertussis-toxin-sensitive G protein i n rats. NPY receptors are coupled to cAMP and Ca2+. Because these seco nd messengers are known to activate cAMP response element binding prot eins, (CREB), cAMP response element modulators, or activating transcri ption factor 1, we investigated the involvement of these transcription factors in NPY-induced feeding in rats. Compared with control injecti ons of cerebrospinal fluid (1 mu l), IHT administration of NPY increas ed cAMP response element (CRE) binding to rat hypothalamic nuclear ext racts in a time-dependent manner, as detected by an electrophoretic mo bility shift assay. In contrast, IHT administration of the anorectic n europeptide, pituitary adenylate cyclase activating polypeptide, stron gly inhibited the CRE binding. Food deprivation for 48 hr also increas ed CRE binding, whereas 8 hr of refeeding normalized CRE activity. Pre incubation of the hypothalamic nuclear extracts of NPY-treated and unf ed rats with antibody specific to CREB blocked CRE binding, whereas pr eincubation with phosphoCREB antibody retarded the migration of CRE-pr otein complex, indicating that phosphoCREB is involved in this process . Consistently, immunohistochemical studies with food-deprived rats sh owed an intense phosphoCREB signal in the paraventricular nuclei and v entromedial hypothalamus in comparison to rats fed ad libitum. Hypotha lamic calcium/calmodulin-dependent protein kinase II activity was also increased by IHT-NPY. These results suggest that calcium/calmodulin-d ependent protein kinase II induced phosphorylation of CREB may be invo lved in regulating feeding behavior induced by NPY.