(A) The effect of TNFα siRNA on the expression of TNFα induced by LPS in the in vitro study. Cultured HAPI cells were treated with TNFα siRNA or mismatch RNA 24 hours prior to the treatment with LPS. Cells were collected 6 hours after LPS and then homogenized with lysis buffer. TNFα was measured using a Western blot. The expression of TNFα in cells treated with TNFα siRNA was significantly lower than that in cells treated with mismatch RNA, ** p < 0.01 vs mmRNA, n=3, t test. The effect of TNFα siRNA on the expression of TNFα induced by ddC in the DRG (B) and spinal dorsal horn (C) was tested. At 12 days after ddC, rats received intrathecal injection of siRNA of TNFα or mismatch RNA once a day for 2 days. The DRG and the spinal cord of animals were harvested, and Western blots were carried out. The expression of TNFα in rats treated with TNFα siRNA was significantly lower than that in rats treated with mismatch RNA, *p < 0.05 vs mmRNA, n=4, t test. (D)The antinociceptive effect of siRNA of TNFα on the mechanical threshold in rats treated with ddC. At 12 days after ddC, rats received intrathecal injection of siRNA of TNFα or mismatch RNA. Administration of siRNA of TNFα, but not mismatch RNA, reversed the mechanical threshold, F(1,12)=11.733, p = 0.005 vs mismatch RNA, n=7, General Linear Model, repeated measure, SPSS.