Electron microscopical studies on the effect of lapsed time on the nerve endings of the outer hair cells in acoustically exposed rabbits.

Rabbits were exposed to pure tone (2 kHz, 100 dB for 2 h) and the changes in the nerve endings of the outer hair cells over a period of 1 month were studied using the electron microscope. In the afferent nerve endings mitochondria dilated and small vesicles decreased in number immediately after acoustic exposure. However, the afferent nerve endings recovered during the period of 1 month. In the efferent nerve endings mitochondria dilated and were distributed throughout the nerve endings, and small vesicles decreased in number immediately after acoustic exposure. The efferent nerve endings recovered more slowly than afferent nerve endings. In addition, the changes in the agglomerations of synaptic vesicles along the synaptic membrane and the gap-structures in the synaptic cleft in the efferent nerve endings after acoustic exposure are briefly discussed.