The syntheses and rat CRF receptor binding affinities of 'retro-pyrazolotriazine'corticotropin- releasing factor (CRF) ligands 4 are reported. Some have high affinity for rat CRF receptors (Ki≤ 10 nM). The data provide additional support for the hypothesis that it is possible to interchange isosteric cores with similar electronic properties in the design of high-affinity CRF receptor ligands, provided the peripheral pharmacophore elements are maintained ...