The ability of a series of substituted kynurenic acids, thienopyridinonecarboxylic acids, and related compounds to inhibit the binding of nerve growth factor (NGF) to the p75 NGF receptor (KGFR) was evaluated in a radioligand binding assay that utilized a biotinylated derivative of the extracellular domain of p75 NGFR (p75, J fixed to streptavidin-coated plastic wells. Two compounds, 6-aminokynurenic acid (5hj and the 3-methyl ester of 4, 7- ...