“…To begin to understand the molecular diversity of mature C‐neurons, we labeled various neuronal subtypes with antibodies in brachial spinal cord transverse sections of Robo3 Cre/+ ; ROSA26 LSL‐tdTomato/+ mice (Figure a–g). PKC‐γ is expressed in excitatory interneurons that receive inputs from low‐threshold mechanoreceptors (Neumann, Braz, Skinner, Llewellyn‐Smith, & Basbaum, ); NK‐1R identifies ascending projection neurons located in dorsal horn lamina I (Todd, ); CGRP labels ventral horn MNs and other neurons in the superficial dorsal horn, lamina X, and ventral spinal cord (Eftekhari & Edvinsson, ; Gibson et al, ; Kim, Sunagawa, Kobayashi, Shin, & Takayama, ); Tlx3 marks dI5 excitatory neurons in the dorsal horn (Xu et al, ); Pax2 identifies subsets of mature inhibitory neurons (Cheng et al, ; Larsson, ); staining for GABA identifies neurons that synthesize this inhibitory neurotransmitter; CB and CR are calcium‐binding proteins expressed in subsets of almost exclusively excitatory neurons (Albuquerque, Jackson, & MacDermott, ; Antal et al, ; Ren & Ruda, ). We found that PKC‐γ + neurons do not contribute to the commissural population (Figure a), 2.14 ± 0.31% of C‐neurons belong to the NK‐1R + population (Figure b), 3.61 ± 0.63% are positive for CGRP (Figure c), 12.67 ± 2.13% express Tlx3 (Figure d), 51.78 ± 9.27% are classified as Pax2 + (Figure e), 39.57 ± 4.32% belong to the GABA + population (Figure f), 5.66 ± 0.56% are positive for CB but not CR, 12.62 ± 3.78% do not express CB but are CR + , and 2.91 ± 0.89% are both CB + and CR + (Figure g).…”