CXCR4 and diabetes mellitus: Both the spinal cord TNF-α and CXCR4 protein expressions were significantly increased at 5 weeks (Figures 3(c) and 3(d), P < 0.05) but not at 2 weeks of diabetes (Figures 3(a) and 3(c), P > 0.05, diabetes vs. control) despite significant reductions in the thresholds of PWT and PWL as early as 1 week of diabetes (Figure 2) as compared to control.