The present invention relates to a method for identifying modulators of B1 G-protein coupled receptors. The present invention also relates to a method for identifying an antagonist or agonist of the corticotropin-releasing factor receptor 2 (CRFR2). The present invention also relates to a method for improving antagonists or agonists of CRFR2. The present invention also relates to the three-dimensional structure of CRFR2 as representative of the B1 GPCR subfamily and its use as a basis for rational drug design of antagonist or agonists of B1 GPCRs.