(A) selective inhibition of ligand-independent TrkA baseline activity, but not TrkC baseline activity, accelerates the death of NIH-TrkA in SFM, (B) dose-dependent inhibition of TrkA baseline activity. (C) NIH-TrkA cells were cultured in SFM ± the indicated ligands at 37°C in a cell incubator (NGF 2 nM; 1-ss 20 μM). After detergent solubilization the phosphotyrosine levels of the samples were studied by western blotting with anti-pTyr mAb 4G10. Total TrkA loading was verified on the same membranes with a highly specific anti-TrkA mAb 5C3. (D) Same as in (C) except that samples were studied by western blotting with anti-p-Akt mAb, standardized versus actin loading control, after treatment with the indicated ligands for 20 minutes.