Figure 7. Upregulation of IL-1β in the dorsal horn astrocytes and its involvement in pain behavior after intrathecal injection of SR57227. A, SR57227 (10 pmol, i.t., n = 4) or fractalkine (40 ng, i.t., n = 4) produced an increased expression of IL-1β (bottom panels) in the area from the inset in the spinal dorsal horn (top panels) compared to saline at 2 or 1 h after injection, respectively. Scale bar, 100 μm (top panels) and 25 μm (bottom panels). B, Western blot analysis showed increases in the levels of IL-1β in the spinal dorsal horn tissue of rats treated with SR57227 (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 (bottom panels) but not CD11b in glial cells (top panels) in the spinal dorsal horn in rats treated with SR57227 (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, SR57227 (10 pmol, i.t.)-induced mechanical hypersensitivity was attenuated 2 h after the injection by the antagonist of IL-1 receptor, IL1-ra (10 μg, i.t.) 1 d before and concurrently with SR57227 (***p < 0.001, saline + SR57227 vs saline +saline; #p < 0.05, IL1-ra + SR57227 vs saline + SR57227; n = 5 per group). E, SR57227 (10 ng, i.t.) significantly induced upregulation of IL-1β at 2 h after injection (**p < 0.01, 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). F, Intrathecal fractalkine (40 ng) also resulted in a significant increase of IL-1β expression in the dorsal horn at 1 h after injection (**p < 0.01, vs saline + saline), which was partially suppressed by IL-18R Ab pretreatment (20 μg, i.t., #p < 0.05, vs saline + SR57227; *p < 0.01, vs saline + saline) (n = 3 per group).