Fig 2: Immunohistochemical characterization of ChR2-expressing DRG neurons. A, Immunolabeling of ChR2+ neurons (Venus; green) with either NF200, TrkC, CGRP, TrkA, TRPV1, or IB4 (red) in the L4 DRG contralateral and ipsilateral to PNI on day 14. B, Percentage of colocalization of each marker in ChR2+ DRG neurons [n = 4 rats (two to three slices per rat)]. Size-frequency histogram (inset) illustrating the distribution of the cross-sectional areas of ChR2+ NF200+ DRG neurons in the L4 DRG ipsilateral (371 cells) and contralateral (316 cells) to PNI on day 14. Values represent mean ± SEM. Scale bar: 100 µm.

Fig 3: Effect of CBL on TrkA gp140 expression in the neocortex of young and old rats. TrkA gp140 content was measured using WB. Vehicle (n = 7–8 per group), CBL (n = 7–8). Data are presented as M±S.E.M. **,*** -p < 0.01, p < 0.001 versus respective young groups; # - p < 0.05 versus respective age control, Mann-Whitney U-test.

Fig 4: DRG nociceptor populations are unchanged after Prdm12 knockout and/or SNI(A) Exon-V-specific RNAscope verified loss of mRNA transcript in Prdm12AvilERT2CKO (adult CKO) mice. Scale bar, 100 µm. Inset arrows indicate mRNA puncta detected by the probe; inset scale bar, 25 µm.(B) qRT-PCR in Prdm12AvilERT2 mice after tamoxifen injection revealed reductions in expression of exon 5 of Prdm12, as well as Trpm8 and Ntrk1; other genes were unaffected. The dotted line represents p = 0.05; points above it differ significantly between control and mutant mice. Each point represents the analysis of significance and fold change from average values of n = 6 biological replicates.(C) Relative expression of select genes after SNI or sham surgery specifically from L4–5 DRG. Prdm12 is reduced after SNI in control animals (p = 0.0356) and in sham mutants (p = 0.0482). Additionally, Atf3 expression is increased in both control (p = 0.0001) and mutant (p = 0.0010) mice, but Kcnma1 is reduced only in control animals (p = 0.0239).(D) Representative images of lumbar DRGs from control and Prdm12AvilERT2CKO DRGs contralateral to and ipsilateral to SNI with immunohistochemistry for IB4 and CGRP. Scale bar, 100 µm.(E–I) Quantification of these images revealed no changes in the number of IB4+ (E), CGRP+ (F), TRKA+ (G), TRPV1+ (H), or NF200+ (I) neurons after SNI in either control or Prdm12AvilERT2CKO mice or between those two groups. Each data point in (E)–(I) represents the average counts/section across three DRGs taken from the L2–L5 region of n = 3 mice. DRGs were collected after behavior assessment at 18 weeks.Graphs show means ± SEM; statistical analysis two-tailed Student’s t test (B) or 2-way ANOVA with post hoc Tukey tests when a significant difference was detected (C–I).

Fig 5: Upregulation of NPTX2 expression in peptidergic DRG neurons under chronic itch-like conditions.a, b Nptx2 mRNA in the cervical DRG and spinal cord (SC) in vehicle- and DCP-treated mice (a: n = 6/group, Mann–Whitney test) and in the cervical DRG in SPF- and CV-NC/Nga mice (b: n = 5/group, unpaired t test). c NPTX2 immunofluorescence in the cervical DRG of vehicle- and DCP-treated mice. Scale bar, 100 µm. d Percentage of NPTX2+ neurons in the cervical DRG and immunofluorescence (IF) intensity of NPTX2 per cervical DRG neurons in vehicle- and DCP-treated mice (n = 4/group, unpaired t test). e Double-immunolabeling of NPTX2 and DRG neuronal markers (CGRP, TRKA, VGLUT2, TRPV1, NF200, and IB4) in the cervical DRG in DCP-treated mice. Scale bar: 100 µm. f Quantitative analysis of the percentage of NPTX2+ neurons colocalized with DRG neuronal markers in DCP-treated mice (CGRP; n = 4, VGLUT2; n = 3, TRPV1; n = 4, NF200; n = 4, and IB4; n = 4). g NPTX2 immunofluorescence in the cervical SDH of vehicle- and DCP-treated mice. In DCP-treated mice, NPTX2 (green) was colocalized with CGRP (red) in the SDH. Scale bar, 200 µm. h Electron microscopy analysis of NPTX2 expression at presynaptic terminal connected to a postsynaptic GRPR+ (mCherry+) neuron in the SDH. NPTX2 and mCherry were visualized by small (white arrowheads) and large (red arrowheads) immunogold particles conjugating antibody for NPTX2 and mCherry, respectively. Yellow arrowhead indicates the postsynaptic density site. Scale bar, 100 nm. Values represent mean ± S.E.M. Source data are provided as a Source Data file.