Figure 7

Upregulation of IL-1β in the dorsal horn astrocytes and its involvement in pain behavior after intrathecal injection of SR57227. A. SR 57227 (10 pmol, i.t., n = 4) or fractalkine (40 ng, i.t., n = 4) produced an increased expression of IL-1β (lower panels) in the area from the inset in the spinal dorsal horn (upper panels) compared to saline at 2 h or 1 h after injection, respectively. Scale bar = 100 μm (upper panel) and 25 μm (lower panel). B. Western blot analysis showed increases in the levels of IL-1β in the spinal dorsal horn tissue of rats treated with SR 57227 (10 ng, i.t., *, p < 0.05 at 1 and 4 h, **, p < 0.01 at 2 h, vs. saline, n = 3 per group). C. Dense colocalization of IL-1β and GFAP (lower panels) but not CD11b in glial cells (upper panels) in the spinal dorsal horn in rats treated with SR 57227 (10 pmol, i.t., n = 3) at 2 h after injection, suggesting that IL-1β was predominantly expressed in spinal astrocytes. Scale bar = 25 μm. D. SR 57227 (10 pmol, i.t.)-induced mechanical hypersensitivity was attenuated at 2 h after the injection by the antagonist of IL-1 receptor, IL1-ra (10 μg, i.t.) 1d before and concurrently with SR 57227 (***, p < 0.001, saline + SR 57227 vs. saline + saline; ^# p < 0.05, IL1-ra + SR 57227 vs. saline + SR 57227) (n = 5 per group). E. SR 57227 (10 ng, i.t.) significantly induced up-regulation of IL-1β at 2 h after injection (*, p < 0.05, vs. saline + saline), which was attenuated by pretreatment with CX3CR1 Ab (20 μg, i.t.) (^#, p < 0.05, vs. saline + SR57227) (n = 3 per group).