Figure 5.

Paralleled observation of the behavioral changes (top panel, A–C) and spinal SP-ir release (bottom panel, D–F). Six series of experiments were performed in 13 groups. Behavioral indices were measured and then spinal perfusion was conducted at 1, 2, 3, 5, 7 and 9 weeks after CFA injection. One group of naïve rats served as control. 100 Hz TENS was administered once-a-week started at 24 h after the injection of CFA. The intensity of stimulation was increased from 1 mA to a maximal of 2 mA for 30 min. Behavioral measurements were performed only once for each group prior to spinal perfusion. The inflamed ankles of rats received TENS treatments had a lower level of ankle swelling (A) and lower sensitivity to flexion pain tests (B and C). There was a significant decrease in SP-ir level in spinal perfusate in rats receiving TENS treatments (E and F). *P < 0.05, **P < 0.01 compared with the baseline level; ^#P < 0.05, ^##P < 0.01 compared with the mock TENS control group at the same time point (two-way ANOVA followed by Duncan's test for ankle circumference in A, E and F; Kruskal–Wallis ANOVA followed by Dunn's test for the pain scores in B and C). ^αP < 0.05 compared between two groups from second week to ninth week (two-way ANOVA).