Figure 9. Brn3b expression in the afferent and efferent projecting cells of the developing cochlear nerve.

A, Spiral ganglion neuron cell bodies (black arrowhead), axons forming the cochlear nerve (star) and dendritic processes innervating the cochlea (arrow) in a R26^rtTA-CreERt; Brn3b^CKOAP E15.5 embryo. B, Efferent axon innervations of the cochlea, in a Phox2b:Cre; Brn3b^CKOAP E15.5 embryo and adult (C1,C2). C3 Efferent innervation of the three rows of outer hair cells. D1–G2 coronal sections through the adult pons and brainstem. D1, D2 Dense and sparse labeling of Eve (nucleus of origin of efferents of the vestibular nerve) (arrow head) and OCB (Olivocochlear Bundle) (arrow) in adult Phox2b:Cre; Brn3b^CKOAP (D1) and cRet^CreERt; Brn3b^CKOAP (D2) animals. E1, F1 Brn3b/Phox2b and E2, F2 Brn3b/cRet double positive neurons of the ventral nucleus of the trapezoid body (VNTB), at the level of the superior olivary complex (SOC) (red circle). G1, G2 Phox2b⁺ Brn3b⁺ positive (G1) and cRet⁺ Brn3b⁺ positive (G2) VNTB projections to the cochlear nucleus (black arrow head). Scale bars: A,B,C1,C2 = 100μm, C3=25μm, D1,D2,F1,F2,G1,G2,=200μm, E1,E2=500μm