Western blot analyses of the phosphorylation of ERK, p38 and CaMKII in the DRG following a chronic morphine treatment. A 7-day treatment with morphine (M, 15 μg) increased the level of phosphorylated CaMKII, but not those of ERK or p38. Data are expressed as mean ± SEM of 4 animals. *p < 0.05 vs saline (NS) group. **p < 0.01 vs saline group.