FASTING-INDUCED INCREASES IN FOOD-INTAKE AND NEUROPEPTIDE-Y GENE-EXPRESSION ARE ATTENUATED IN AGING MALE BROWN-NORWAY RATS

Aging in man is associated with alterations in food intake (FI) and bo dy weight (BW). To establish a model of age-related alterations in Fl and BW regulation, Fl and BW were determined in young (3-month-old), m iddle-aged (12-month-old), and old (24-month-old) male Brown Norway ra ts during ad libitum Feeding and after 72 h of fasting. FI was reduced with aging both during ad libitum feeding and after fasting. With fas ting, young rats lost more BW than older rats, but regained BW more ra pidly during refeeding. To determine whether age-related impairments i n FI and BW regulation are mediated by neuropeptide Y (NPY), a potent stimulator of FI, we compared arcuate nucleus prepro-NPY (ppNPY) messe nger RNA (mRNA) by in situ hybridization in fasted and ad libitum-fed (fed) young, middle-aged, and old rats. ppNPY mRNA declined with aging in both fed and fasted rats. Although ppNPY mRNA increased with fasti ng in all age groups, this response was attenuated with aging. In conc lusion, impaired FI and BW recovery after fasting is associated with r educed NPY responsiveness to fasting in aging rats. Impaired activatio n of the hypothalamic NPY pathway may, therefore, contribute to age-re lated alterations in FI and BW regulation.