Fig. 7: Dorsal column activation of Split^Cre-ReaChR⁺ Aβ-LTMRs alleviated mechanical hyperalgesia in the chronic inflammatory pain model.

A Illustration showing our experimental paradigm. Blue laser stimulates ascending dorsal horn axons of Split^Cre- ReaChR⁺ Aβ-LTMRs (green color). VFH tests were performed at the baseline and different time points of the CFA model. B PWT of spinal cord stimulation using 0.5 and 10 mW blue laser. n = 7 mice. Black arrow indicates the time of blue light stimulation. C Quantification of c-Fos+ neurons in the superficial and deep dorsal horn laminae of the thoracic and lumbar spinal cord of no-light and light- stimulated Split^Cre-Aβ ReaChR mice (without treatment). Light blue and black bars represent light (0.5 mW) and no light conditions respectively. D RNAscope of c-Fos, Slc17a6, and Slc32a1 with lower thoracic spinal cord section. Scale bar = 50 μm. E Quantification of excitatory (Slc17a6⁺, brown bar) and inhibitory (Slc32a1⁺, black bar) interneurons co- labelled with c-Fos in the superficial and deep dorsal horn laminae of the thoracic and lumbar spinal cord after light stimulation. n = 3 mice, 4 sections per mouse. F Global activation of Split^Cre-ReaChR⁺ Aβ-LTMRs alleviated mechanical hyperalgesia in mice with CFA-induced chronic inflammatory pain. i. Spinal stimulation at 2 hour post-CFA significantly reversed the PWT at 5 min and 30 min post-light stimulation. ii. At D7 post-CFA, a significant reversal of PWT was observed at 5 min. and 30 min.post-light stimulation. iii. At D14 post-CFA, a significant reversal of PWT was observed at 5 min and 30 min. post-light stimulation. iv. At D21 post-CFA, no significant difference was observed in PWT post-light stimulation. Black arrow indicates the time of blue light stimulation. n = 6 mice except panel C (3 mice, 5-7 sections per mouse for statistical comparison) and E (3 mice, 3–4 sections per mouse). Error bars represent Mean ± S.E.M. Two-way ANOVA followed by Bonferroni test. *p < 0.05, **p < 0.01, ****p < 0.0001, ns = non-significant. See source data file for detailed p values and statistical tests. Source data are provided as a Source Data file.