(A). ChR2-YFP expression in unmyelinated and myelinated (lanceolate endings of hair shaft, panels on right) fibers of Prph-ChR2 mouse skin. Arrows indicate nerve fibers in dermis and epidermis (Epi); DAPI (blue) labeling demarcates keratinocytes. (B). ChR2 is expressed in DRG neurons of Prph-ChR2 but not KRT-ChR2 mice. CGRP labels peptidergic neurons. (C). Ex vivo preparation used for functional characterization of cutaneous afferents in response to mechanical, heat and laser stimulation. (D). Response of a Prph-ChR2 Aδ-HTMR to mechanical and blue laser stimulation. (E). Recordings from a CMHC nociceptor from a Prph-ChR2 mouse in response to mechanical, thermal and light stimulation. Calibration bars in (A) = 250 µm, (B) = 100 µm, (E) = 60 mV/1 s, top trace; 40 mV/1 s, bottom trace.