Fig. 1. Innervation of vestibular (A,B) and cochlear (C) sensory epithelia in TrkB- and Bdnf-mutant mice. Cochlear sections through the labyrinth of newborn (P0) and adult animals were labelled with anti-NF200 antibody to visualise afferent innervations. Arrows point to fibres; filled arrowheads mark hair cells (A,B). (A) TrkB^shc/shc mice maintain innervation of the sacculus at birth but show a severe reduction of NF200-positive fibres opposite the sensory epithelia in adults compared with TrkB^shc/+ controls. In TrkB^shc-/- mutants innervation is already lost at birth. (B) In the utriculus, both TrkB^shc/shc and TrkB^shc/- mutants lack afferent innervation at adulthood. (C) In the first postnatal week (P0-P8) neurofilament-positive projections are detected in the cochlea opposite all three rows of outer hair cells (OHC) in TrkB^shc/+ controls, but not in TrkB^shc/-, Bdnf^-/- or TrkB^-/- mutants. Scale bars: 20 µm.