Fig. 3. Reduction of TrkC, parvalbumin and Brn3b expression in the Brn3a^-/- spiral ganglion. (A-F) Compared with the wild-type ganglia (A,C), TrkC immunoreactivity is greatly reduced in the E15.5 (B) and E18.5 (D) mutant spiral ganglia. By contrast, a similar level of TrkB immunoreactivity is present in E18.5 spiral ganglion between wild-type (E) and Brn3a mutant (F). Arrows point to radial fibers. (G,H) Parvalbumin immunoreactivity shows substantial decrease in the mutant spiral and vestibular ganglia and their nerve fibers. (I-L) In contrast to the robust expression of Brn3b in wild-type ganglia, the intensity of Brn3b expression and the number of neurons positive for Brn3b is dramatically diminished in E18.5 mutant embryos. Cri, crista; Sac, saccule; SG, spiral ganglion; Utr, utricule; VG, vestibular ganglion. Scale bar: 25 µm in A-D,K,L; 50 µm in E,F; 100 µm in G-J.