UC Irvine

The stress neurohormone corticotropin releasing factor (CRF) activates at least two receptor types. Expression of corticotropin releasing factor receptor type II (CRF2) has been demonstrated in the hypothalamic ventromedial nucleus (VMH) of the adult and developing rat, but the physiological functions of VMH-CRF2 have not been elucidated. The VMH has been documented as an important participant in the regulation of food intake and its interactions with the hypothalamic-pituitary-adrenal axis and circadian rhythms. Regulation of VMH-CRF2 may thus play a role in the interplay of physiological alterations in metabolic state with the neuroendocrine and anorexic effects of CRF. This study determined the regulation of CRF2-mRNA expression in infant rats by the physiological consequences of maternal deprivation, i.e., fasting and stress. Using in situ hybridization, maternally deprived pups had an average 62% reduction of VMH-CRF2-mRNA levels compared with stress-free controls. Maternal deprivation also resulted in elevated plasma corticosterone levels (3.8 +/- 0.3 vs. 1.3 +/- 0.1 microg/dl) and an average 5.7% body weight loss. This study demonstrates that maternal deprivation, via fasting and HPA activation, leads to a dramatic decrease of CRF2-mRNA levels in the VMH. These results are consistent with a role for CRF2 activation in mediating some of the complex interactions of CRF (or urocortin) with regulation of food intake in the developing rat.