Phosphorylation of ERK in the RVM increases with mechanical sensitivity in a model of neuropathic pain. Effects of SNI or sham surgery in adult rats (N = 4-5 in each group) on: A/Mechanical withdrawal thresholds measured by Von Frey testing of the hind paw of the operated limb; and B/pERK expression in the RVM 3 and 8 days after surgery. Adult rats developed mechanical hypersensitivity and showed increase ERK activation in the RVM at 3 and 8 days post-SNI. Data show mean ± SEM. * P < 0.05, ** P < 0.01.