Fig. 1.  Spinal MIF was increased in CCI-treated mice. Mice having undergone CCI sciatic nerve injury displayed changes in mechanically and thermally stimulated pain behaviors of the ipsilateral hind paws on days 1, 3, 7, 14, and 21 (A  and B ; n = 6 in the sham group and n = 8 in the CCI group; *P < 0.05 vs.  CCI Contra and Sham Ipsi). The level of MIF measured using ELISA in CSF from CCI mice was increased significantly on days 3, 7, and 14, but no similar change was observed in plasma (C ; n = 6; *P < 0.01 vs.  CSF Baseline). (D ) Immunofluorescence assay showed that the expression of MIF protein in the ipsilateral spinal cord dorsal horn after CCI was significantly upregulated (A ′ to D ′; n = 6; scale bar, 120 μm; detected with FITC-conjugated antibody). (E ) Electrical stimuli-evoked EPSCs on the substantia gelatinosa neurons in the lumbar spinal cord sections were measured with a voltage clamp, and it was found that CCI-induced higher amplitude of the firing could be inhibited by the MIF-specific antagonist of ISO-1, but the firing frequency in Hz did not show any change in CCI and ISO-1-treated CCI (n = 8; *P < 0.01 Sham vs.  CCI; ^#P < 0.05 CCI vs.  CCI+ISO-1; **P < 0.05 Sham vs.  CCI+ISO-1). Data are shown as means ± standard deviations. MIF = macrophage migration inhibitory factor; CSF = cerebrospinal fluid; CCI = chronic constriction sciatic nerve injury; FITC = fluorescein isothiocyanate; EPSC = excitatory postsynaptic current; ISO-1 = MIF tautomerase inhibitor (S ,R )-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid, methyl ester; Ipsi = ipsilateral; Contra = contralateral.