The CRF1 receptor is a Gs-coupled GPCR expressed in the brain and pituitary gland that binds to several neuropeptides, including corticotropin-releasing factor (CRF) and urocortin, and the amphibian peptide sauvagine (Chen et al., 1993; Dautzenberg and Hauger, 2002; Bale and Vale, 2004). CRF plays a predominant role in stress response mediated by the hypothalamic-pituitary-adrenal axis, and alterations in CRF and its receptors CRF1 and CRF2 appear to be linked to depression and anxiety (Holsboer, 1999; Bale and Vale, 2004). A number of small molecule antagonists of the CRF1 receptor have been characterized, including R121919, SC241, NBI27914, antalarmin, DMP-696, and CP 154,526. When delivered in animal models of psychiatric disorders, these antagonists display effectiveness in reducing stress-related behaviors (Kehne and De Lombaert, 2002). Chemicon's cloned human CRF1-expressing cell line is made in the Chem-1 host, which supports high levels of recombinant CXCR2 expression on the cell surface and contains high levels of the promiscuous G protein Galpha15 to couple the receptor to the calcium signaling pathway. Thus, the cell line is an ideal tool for screening for antagonists of interactions between CRF1 and its ligands.