Images: Increased mobilization of trkA to neuronal membrane enhances response to NGF challenge. A, Fluorescence photomicrographs depicting relative levels of activated/phosphorylated trkA (phospho-trkA) detected under permeabilizing conditions in representative adult DRG neurons exposed to acidic (pH 6.5) or control (pH 7.4) media (in the presence of anti-BDNF) for 30 min, followed by a 15 min challenge with pH-specific medium + anti-BDNF alone or with anti-BDNF + 50 ng/ml NGF. Scale bar, 10 μm. Scatter plots illustrate the relationship between phospho-trkA-like labeling intensity (y-axis; normalized to the mean signal intensity from the control pH group) and perikaryal diameter (x-axis) for all sensory neurons analyzed from three separate experiments exposed to control (pH 7.4, B) or acidic (pH 6.5, C) media as above and then challenged with 50 ng/ml NGF (open circles) or not (filled circles). D, Summary bar graph depicting relative levels of activated trkA (phospho-trkA; normalized to pH 7.4 control) in representative adult DRG neurons exposed to acidic (pH 6.5) or control (pH 7.4) media for 30 min and then challenged with 50 ng/ml NGF and as normalized to the mean signal intensity from the control pH group. E, Fluorescence photomicrographs of sensory neurons exposed to identical conditions as in A and processed to detect activated/phosphorylated p38MAPK Note: A significant increase is observed in the levels of phospho-trkA detected in sensory neurons in response to acidosis with a parallel response observed for phospho-p38MAPK (E) (one-way ANOVA with post hoc Tukey's; ***p < 0.001; n = 131-210 neurons analyzed per experimental condition). Scale bar, 20 μm. The Journal of Neuroscience, 8 May 2013, 33(19): 8202-8215; doi: 10.1523/​JNEUROSCI.4408-12.2013-phospho-TrkA Customer Publications.