Figure 3.

Axon terminal innervation of E18.5 footpad. (A, top) Normal innervation. (middle) In the absence of TrkA, innervation is diminished overall, and the CGRP-positive nociceptor endings are completely absent. Red arrowheads indicate the CGRP-positive axon terminals in the epidermis. (bottom) kaB-RAF expression partially rescues nociceptive innervation in the TrkA^−/− background. The dashed lines indicate the dermal–epidermal border. Bar, 100 µm. (B) Quantification of axon innervation in footpad (Luo et al., 2007; Hancock et al., 2011). Data are from three fetuses per genotype. Error bars indicate SEM. One-way ANOVA with post-hoc Tukey’s HSD test: **, P < 0.01.