Fig. 6

Downregulation of 5-HT synthesis reversed hyperalgesia after delayed REOI but did not alter PEOI-induced hyperalgesia. A Schematic diagram of the experimental time course of HWT measurements (n = 7–9 in each group). B Injection of viruses into the RVM region. C, D Changes in HWTs in all the groups. Results represent mean ± SD; two-way repeated measures ANOVA, followed by Tukey’s multiple-comparison test. & P < 0.05, &&& P < 0.001, Tph2-shRNA-expressing REOI group vs. scramble-shRNA-expressing REOI group. ## P < 0.01, ### P < 0.001, #### P < 0.0001, day 14 or day 21 vs. baseline. E Representative images revealed co-expression of Tph2-labeled neurons with EGFP in the RVM in the scramble-shRNA-expressing rats while little co-expression was observed in the Tph2-shRNA-expressing rats. Scale bar, 200 μm. F Immunofluorescence staining illustrated the number of Tph2-positive neurons in the Tph2-shRNA-expressing and the scramble-expressing REOI groups, as well as in the Tph2-shRNA-expressing and the scramble-shRNA-expressing PEOI groups. Scale bar, 200 μm. G Semi-quantitative analysis of the number of Tph2-positive cells in all the groups. Fewer Tph2-positive cells were found in Tph2-shRNA-expressing REOI group (vs. scramble-shRNA-expressing REOI group) and Tph2-shRNA-expressing PEOI group (vs. scramble-shRNA-expressing PEOI group). Results represent mean ± SD; two-way ANOVA, followed by Tukey’s multiple-comparison test. Tph2, tryptophan hydroxylase 2