Fig. 2. Fiber classes of targeted neurons in NFH;Na_V1.8;ReaChR mice.

a Left panels show example micrograph of sciatic nerve sections immunolabelled for mCitrine and CGRP. Single optical section, 63×/1.4 objective. Examples of mCitrine⁺ fibers without CGRP-IR are indicated by arrows, and mCitrine⁺ fibers colocalized with CGRP-IR are indicated by arrowheads. Scale bar, 5 µm. The right panel shows violin plots of fiber diameters (including MBP⁺ myelin sheath) of CGRP⁺ and CGRP⁻ mCitrine⁺ fibers in the sciatic nerve. n = 3 mice (1 sciatic nerve section per mouse). The number beneath each violin plot indicates the number of fibers analyzed. ****, p < 0.0001, Kolmogorov–Smirnov test. Statistics details are available in Supplementary Data 1. b Conduction velocity (CV) of optogenetically evoked compound action potentials (CAPs). The left panel shows a schematic of the DRG-dorsal root ex vivo preparation used. The measured distance was used for determining the CV. Middle panels, example traces of optogenetically (top) or electrically (bottom) evoked recordings. Blue line indicates time of optogenetic activation; arrow in top trace indicates optogenetic response. The dashed arrow indicates the stimulation to signal (total) latency, while the red arrow indicates the delay for ReaChR activation, which was subtracted from the total latency to yield the conduction latency. Right panel, a summary plot of the CVs of CAPs evoked by electrical (black) or optogenetic stimulation (green). The red dashed line indicates the border between Aδ and Aβ fiber CVs (Djouhri et al.³⁵). c In vivo Ca²⁺ imaging of NFH⁺/Na_V1.8⁺ DRG neurons. NFH;Na_V1.8;GCaMP7s mice were subjected to in vivo imaging of L4 DRGs to assess responses to natural stimuli applied to the skin of the plantar hind paw. The top panels show example micrographs of responses to different stimuli in an L4 DRG. Bottom panel, a heat map of the responses of GCaMP7s⁺ cells to cutaneous stimuli as indicated. Each row indicates the responses to the applied stimuli of an individual cell. n = 193 cells, collected from three L4 DRGs (one ganglion per mouse). Schematic created in BioRender. Larsson, M. (2026) https://BioRender.com/yim1dhh. Source data are provided as a Source Data file.