Neuropeptide Y and corticotropin-releasing hormone concentrations within specific hypothalamic regions of lean but not ob/ob mice respond to food-deprivation and refeeding

Leptin is proposed to control food intake at least in part by regulating hypothalamic neuropeptide Y (NPY), a stimulator of food intake, and corticotropin-releasing hormone (CRH), an inhibitor of food intake. Ob/ob mice are leptin-deficient and would thus be expected to exhibit alterations in hypothalamic NPY and CRH, We therefore measured concentrations of NPY and CRH in discrete regions of the hypothalamus (i.e,, ARC, arcuate nucleus; PVN, paraventricular nucleus; VMH, ventromedial nucleus; DMH, dorsomedial nucleus; and SCN, suprachiasmatic nucleus) of 6.5-7-wk-old ob/ob and lean mice with free access to stock diet, 24 h after food deprivation, and 1 h after refeeding. Fed ob/ob mice had 55-75% higher concentrations of NPY in the ARC, VMH and SCN than lean mice. Food deprivation increased NPY concentrations similar to 70% in the ARC, PVN and VMH of lean mice, and refeeding lowered NPY concentrations similar to 70% in the PVN of these mice. NPY in these hypothalamic regions of ob/ob mice was unresponsive to food deprivation or refeeding. The most pronounced change in CRH concentrations within the regions examined (i.e., ARC, PVN and VMH) occurred in the ARC of lean mice where refeeding lowered CRH concentrations by 75% without influencing ARC CRH concentrations in ob/ob mice, The hypothalamic concentrations of two neuropeptides involved in body weight regulation (i.e., NPY and CRH) in leptin-deficient ob/ob mice respond abnormally to abrupt changes in nutritional status.