Figure 3

p75^−/−mice show reduced branching on embryonic day 18.5. DiI-labeled chorda tympani axons in wild-type (A,C,E) and p75^−/−(B,D,F) mice. As with the other ages, innervation was particularly sparse in the tongue mid-region of the p75^−/−tongue (D) compared to wild-type tongue (C). Sagittal sections near the tongue mid-line show that innervation reached the epithelial surface in both genotypes (G,H), although p75^−/−mice had less innervation caudal to the tongue tip. Scale bar = 500 μm for A, B, C, D, E, and F; scale bar = 200 μm for G and H.