Figure 1. The expression of pC/EBPβ in the SCDH in the peripheral gp120 neuropathic pain model. A, Rats received peripheral gp120 application onto the left sciatic nerve, and the sham group received RSA as vehicle. Time course of mechanical withdrawal threshold was measured using von Frey filaments to ipsilateral hindpaws and contralateral hindpaws. Peripheral gp120 induced a persistent lowered mechanical withdrawal threshold of the ipsilateral hindpaw as measured by von Frey filaments compared with sham rats; F(12,96), interaction = 2.238, p < 0.05; F(4,96), main effect time = 2.611, p < 0.05; F(3,24), main effect treatment = 11.05, p < 0.0001, two-way repeated-measures ANOVA; n = 7. We also observed that there was a significant lowered mechanical threshold in ipsilateral (gp120-ipsi) compared with that contralateral hindpaws (gp120-contra) in gp120 rats at days 7, 10, and 14 (**p < 0.01, ***p < 0.001 vs gp120-contralateral paw; two-way ANOVA, Bonferroni post-tests, n = 7. Mechanical threshold in ipsilateral hindpaws in gp120 rats (gp120-ipsi) was significantly lower than that in ipsilateral hindpaws in sham rats (sham-ipsi) at days 7, 10, and 14 (##p < 0.01, ###p < 0.001 vs sham-ipsilateral paw; two-way ANOVA, Bonferroni post-tests; n = 7. There was no significant difference in mechanical threshold between ipsilateral hindpaw (sham-ipsi) and contralateral paws (sham-contra) in sham rats. B, Western blots showed no difference in the expression of pC/EBPβ in sham rats between ipsilateral (sham-I) and contralateral (sham-C) SCDH in the SCDH 2 weeks post-gp120. C, pC/EBPβ in the ipsilateral SCDH in gp120 rats (gp120-I) was significantly higher than that in the contralateral SCDH (gp120-C); **p < 0.01, t test, n = 6. D, No difference in the expression of C/EBPβ in sham rats between ipsilateral (sham-I) and contralateral SCDH (sham-C) at 2 weeks post vehicle. E, C/EBPβ in the ipsilateral SCDH in gp120 rats (gp120-I) was significantly higher than that in the contralateral SCDH (gp120-C); **p < 0.01, t test, n = 6. F, RT-PCR showed that gp120 increased the expression of mRNA of C/EBPβ; ***p < 0.001 versus sham, t test; n = 5. G, Western blots assay showed that gp120 evoked overexpression of pC/EBPβ in the ipsilateral SCDH compared with either naive or sham groups; #p < 0.05 versus sham **p < 0.01 versus naïve; one-way ANOVA, post hoc PLSD test; n = 4. H, HIV gp120 induced the overexpression of C/EBPβ in the ipsilateral SCDH; ***p < 0.001 versus naïve; ###p < 0.001 versus sham; one-way ANOVA, post hoc PLSD test; n = 4. I, Low-magnification image showed pC/EBPβ immunostaining in the L4/5 lamina I–V of the SCDH. Scale bar, 100 μm. J–L, Double-immunostaining showed that pC/EBP-beta-positive cells were colocalized with NeuN (a neuron marker; J), but few of pC/EBP-beta-positive cells overlaid with GFAP (astrocytes marker; K) or with OX42 (a microglia marker; L) in the SCDH in rats with gp120 application at 2 weeks. Scale bar, 50 μm. M, Twelve days after gp120 application, intrathecal administration of C/EBPβ siRNA or mmRNA was given once a day for 2 d. Intrathecal C/EBPβ siRNA significantly increased mechanical threshold (F(5,50), interaction = 8.59, p < 0.0001; F(5,50), main effect time = 9.52, p < 0.0001; F(1,10), main effect treatment = 7.96, p < 0.05; two-way repeated-measures ANOVA). Mechanical withdrawal threshold in the C/EBPβ siRNA group was higher than that in mmRNA at day 1 and 2; ***p < 0.001 versus mmRNA; two-way ANOVA, Bonferroni tests; n = 6. N, Western blots displayed that C/EBPβ siRNA reversed the upregulated pC/EBPβ in the SCDH. **p < 0.01 versus sham+mmRNA; ##p < 0.01 versus gp120+mmRNA; one-way ANOVA, post hoc PLSD test; n = 4–5.