Fig. 4

Intrathalamic application of Tm induces mechanical allodynia and neuroinflammation in healthy rats, and vice versa. LPS activates ER stress in healthy rats. a The experimental timeline of intrathalamic cannula implantation, agent delivery, pain behavioral tests, and Western blotting. b Healthy rats exhibit a significant decrease in PWMT in both ipsilateral and contralateral hind paws throughout the 180-min observation time after Tm administration at a dose of 0.1 μg or 1 μg. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001 compared with vehicle-treated rats, n = 10 per group, two-way ANOVA with Bonferroni tests. c Healthy rats exhibited increased secretion of the proinflammatory cytokines including TNFα, IL-1β, and IL-6 around thalamic VPL at 180 min after intrathalamic injection of 1 μg Tm or 1 μg LPS, compared with the vehicle. Data are expressed as mean ± SD and analyzed by one-way ANOVA with the Bonferroni test. **P < 0.01, ***P < 0.001, ****P < 0.0001 compared with the vehicle-treated rats, n = 5 per group. d, e Representative Western blot bands and quantification of ER stress markers and JNK/p38 in the perithalamic site of vehicle and Tm group were presented. Phosphorylation of JNK and p38, as well as ER stress markers, are significantly elevated around the thalamic VPL region at 180 min after Tm injection in the healthy rats compared with rats given vehicle treatment. Scatter plots with bar graphs display the relative density of the target proteins. Data are expressed as mean ± SD and analyzed by independent t-test. *P < 0.05, **P < 0.01, ***P < 0.001compared with the vehicle-treated rats, n = 5 per group. f, g Representative Western blot bands and quantification of ER stress markers and JNK/p38 in the perithalamic site of vehicle and LPS group were presented. ER stress markers, as well as hallmarks of the MAPK pathway, are markedly increased around the thalamic VPL region at 180 min after LPS injection in the healthy rats. Data are expressed as mean ± SD and analyzed by independent t-test. *P < 0.05, **P < 0.01, compared with the vehicle-treated rats, n = 5 per group. Tm, tunicamycin; LPS, lipopolysaccharide; ICI, intrathalamic cannula implantation; ns, no significance