Fig. 2. Effect of the surgical incision on the expression of p-ERK in neurons of the ACC. (A–J ) Representative photomicrographs showing the p-ERK immunoreactivity in the ACC at different time points (15 min, 30 min, 1 h, 6 h, 24 h, and 72 h) after hind paw incision or sham operation (15 min and 24 h). Surgical incision biphasically increases the expression of p-ERK in the ACC. (I ) Image of higher magnification in the inset of H . (K  and L )Time course of the number of p-ERK-labeled cells in the ipsilateral side (K ) and contralateral side (L ) of ACC after hind paw incision (n = 4–5 for each time point). Bar, 200 μm. ACC = anterior cingulate cortex; p-ERK = phosphorylated extracellular signal-regulated kinase. **P < 0.01 versus  sham-operation. One-way ANOVA followed by Dunnett post hoc  test.