Fig. 1. Stimulus-evoked ERK phosphorylation in rat DRG neurons. A, L4 DRG section (30 μm) immunostained for pERK in the naive rat. B, pERK labeling in many small L4 DRG neurons 2 min after intraplantar injection of capsaicin (10 mm, 200 μl). The inset shows a Western blot of capsaicin-stimulated DRG tissue with pERK antibody.C, Time course of capsaicin-evoked pERK expression in L4/5 DRG neurons (n = 5 at each time point; *p < 0.01; **p < 0.001 compared with naive). D, L4 DRG section double-immunostained for NF200 (red) and pERK (green) after intraplantar capsaicin injection.E, Colocalization of pERK (green) and VR-1 (red) in L4 DRG neurons after capsaicin injection. Double staining appears yellow. F, G, Capsaicin-induced pERK was inhibited by the lidocaine block to the sciatic nerve. Cap, Capsaicin group;Lid, capsaicin plus lidocaine group (**p < 0.001 compared with capsaicin group).H, Example of 0.1 mA (a) and 0.3 mA (b, c) evoked action potentials at the sciatic nerve.a, Aβ response; b, c, Aβ and Aδ responses with no c response (c; 100 sweeps were averaged). I, L4 DRG section immunostained for pERK 2 min after 0.3 mA of stimulation to the sciatic nerve. J, L4 DRG section immunostained for NF200 (a marker of myelinated neurons,red) and pERK (green) after a 0.3 mA electrical stimulation. Double staining appearsyellow. Scale bars, 100 μm.