Fig. 5: Opto-activation of Grp⁺ sensory neuron skin fibers evokes itch behavior.

a Schematic of Grp^Cre-KI mating with Ai32 ChR2-eYFP line to produce Grp^ChR2 mice. b IHC Image of eYFP expression in Grp^ChR2 DRG. Scale bar, 50 μm. c IHC images of eYFP and βIII-Tubulin in Grp^ChR2 nape skin. Dashed lines indicate epidermal/dermal boundary. Scale bar, 100 μm. d Optical parameters of skin fiber stimulation Grp^ChR2 and Grp^WT mice. e Raster plot of scratching behavior induced by light stimulation of skin in Grp^ChR2 and Grp^WT mice. f Snapshots of Grp^ChR2 and Grp^WT mice with light off or on. Arrow indicates hind paw scratching the nape when light is on. g Total number of scratches during 5-min light stimulation experiment in Grp^WT, Grp^ChR2, Grp^ChR2 morphine-treated and Grp^ChR2 BB-sap-treated mice. Data are presented as mean ± s.e.m., n = 8 mice for Grp^WT, 9 mice for Grp^ChR2 BB-sap, and 10 mice for Grp^ChR2 and Grp^ChR2 morphine, one-way ANOVA with Tukey post hoc, ***p < 0.001, ns not significant. Source data are provided as a Source Data file.