The neurobiology of urocortin

Urocortin (UCN) is a recently isolated 40 amino acid-containing neuropeptid e that is the second endogenous mammalian ligand for the corticotropin-rele asing factor (CRF) receptors. While UCN and CRF both display a similar high affinity for the CRF1 receptor, the affinity of UCN for the CRF2 receptor is more than 10-fold higher than that of rat/human CRF. UCN mRNA expression is highest in the Edinger-Westphal nucleus and lateral superior olive, wit h the most prominent terminal fields found in the lateral septum. Because o f the higher relative affinity of UCN for the CRF2 receptor and the corresp onding neuroanatomical distribution of the highest density of UCN expressio n and innervation to brain regions preferentially expressing the CRF2 recep tor subtype, it has been hypothesized that UCN is the preferred endogenous ligand for the CRF2 receptor. Following central administration, UCN has bee n demonstrated to produce behavioral and physiological effects that are qua litatively similar to CRF. Quantitatively, however, UCN appears to be a mor e potent suppressor of ingestive behavior (food and water intake) and a les s potent inducer of anxiogenic behavior than CRF. (C) 2000 Elsevier Science B.V. All rights reserved.