Figure 5

Fractalkine-induced hypersensitivity and up-regulation of IL-18 are mediated by spinal microglia. A. Fractalkine (40 ng, i.t.) induced behavioral hyperalgesia (p<0.001, one-way ANOVA, n = 4 for each group; *, p<0.05, **, p<0.01, vs. baseline), which was significantly attenuated by pretreatment with a neutralizing antibody against CX3CR1 (CX3CR1 Ab, 20 μg, i.t.) (^#, p<0.05, ^##, p<0.01 vs. saline + fractalkine). B. Fractalkine (40 ng) increased CD11b or Iba1 expression (lower panels); lower panels are from the insets of the spinal dorsal horn (upper panels, respectively) at 1 h after intrathecal injection when compared with vehicle treatment. Scale bar=100 μm (upper panels) and 25 μm (lower panels). C. The expression of Iba1 and IL18 in the spinal dorsal horn was increased at 2 h after injection of fractalkine (40 ng, i.t.) when compared with saline group (*, p<0.05, n=3 per group); such upregulation was significantly attenuated by pretreatment of CX3CR1 Ab (20 μg, i.t.) (^#, p<0.05, n=3). D. IL18 in the dorsal horn was upregulated 2 h after i.t. SR57227 (10 pmol) or fractalkine (40 ng) but not vehicle when compared with that in naïve rat (n=3-4 per group). Scale bar=100 μm. E. Increased expression of Iba1 but not GFAP in the dorsal horn glial cells was colocalized with IL-18-IR at 2 h after fractalkine treatment (40 ng, i.t. n=3-4). There was no coexpression of IL-18 and NeuN. The right upper panel is an enlarged area from the inset from the dorsal horn in the left upper panel. Scale bar=100 μm (the left upper panel) and 25μm (the right upper, middle and lower panels). F. IL-18 was increased in the dorsal horn at 2 h after i.t. SR57227 (10 pmol, n=3) (*, p<0.05) compared with that with saline (i.t., n=3). CX3CR1 Ab (20 μg, i.t., n=3) prevented the effects of SR57227 on IL-18 expression (^#, p<0.05).