Effects of multiple intraperitoneal (i.p.) injection of gabapentin (Gab, 100 mg/kg) on MA-induced spinal glial activation and thermal hyperalgesia. A and B, Effects of repeated Gab treatment on MA-induced increase in Iba-1-1R (A) and GFAP (B) in the ipsilateral spinal dorsal horn. C and D, Quantification of Iba-1-IR (C) and GFAP-IR (D) expression on both sides of the spinal dorsal horn ** p < 0.01 vs. sham control; + p < 0.05, ++ p < 0.01 vs. MA. E, Repeated Gab treatment inhibited MA-induced thermal hyperalgesia. Repeated i.p. Gab or NS were given directly after the behavioral test on days 0–3, with the first injection 60 min before intra-articular injection of CFA. ** p < 0.01 vs. NS control.