The role of corticotropin-releasing factor and urocortin in the modulationof ingestive behavior

Participation of the hypathalamo-pituitary-adrenocortical axis, and its pri mary brain trigger, corticotropin-releasing factor (CRF) in the control of ingestive behavior can be inferred from data suggesting that CRF and its ho mologue urocortin act in brain to limit appetite following administration i n rodents. Moreover, levels of endogenous CRF, CRF, and CRF, receptors and CRF-binding protein, which sequesters CRF and urocortin, are altered by cha nges in nutritional status brought about by food restriction/repletion. Med iation of the anorexic effects of CRF and urocortin appear not to privilege CRF, receptors, unlike the anxiogenic effects of CRF which are primarily a consequence of CRF, receptor activation. Such fear-like consequences of CR F system activation constitute a non-specific mechanism whereby the emergen ce of behaviors incompatible with food intake may appear to suppress appeti te without affecting hunger per se. However, enhanced appetite following ad ministration of CRF receptor antagonists and the involvement of CRF systems in sexual appetite and drug-seeking behavior all suggest a role for CRF in ingestive behavior. In particular, available evidence suggests that physio logically relevant suppression of appetite may accompany CRF system activat ion occurring as a consequence of stressor exposure induced by nutrient imb alance, for example, or under conditions of excessive intake or consumption of unfamiliar foodstuffs. (C) 1999 Harcourt Publishers Ltd.