Postnatal development of the vestibular sensory epithelium in the mouse.

The vestibular epithelium of the CBA/CBA mouse was analyzed from birth until the adult stage. Hair cells type I and type II develop in parallel. Initially, the innervation progresses rapidly post partum. A few mature type I hair cells with fully developed nerve calyces occur 4 days post partum. An early temporary innervation of both type I and type II hair cells occurs and is later rebuilt forming mature nerve endings and nerve calyces. Synaptic bodies develop within the cytoplasm of hair cells without the contact of nerve endings. Efferent nerve endings develop late on both type I and type II hair cells and moreover are few in the adult animal. The vestibular epithelium is not completely mature until 3-4 weeks post partum.