Basolateral processes of type II hair cells receive synaptic inputs from vestibular
efferents. A. A horizontal confocal slice through the basolateral processes of type II
hair cells in a 6 week-old CBA/CaJ mouse utricle labeled for myosin VIIa (green) and
choline acetyl transferase (chat, magenta). Arrows point to three apparent sites of
contact between efferent endings and basolateral processes. B. An ultrathin transverse
section through a utricle from a 9 week-old CBA/CaJ mouse. The basolateral processes (P)
of a type II hair cell (HCII) of a type II hair cell are tinted green. The box
indicates the site of an efferent nerve element (eff) that synapses on the process; this
site is shown at higher magnification in the inset on the upper right. In the inset, the
white arrowhead points to polyribosomes in the hair cell process, the black arrowhead
points to the post-synaptic cistern in the hair cell, and the black arrow points to the
pre-synaptic vesicles in the efferent nerve element (eff). SC = supporting cell,
Cx = calyx of a type I hair cell. Scale bars: A = 4 μm; B
= 2 μm; inset B = 500 nm.