Ultrastructure of Nerve Endings of Inner Hair Cells (the Second Report)

Abstract

It is supposed that inner hair cells play an important role in hearing mechanisms, but the reports concerning the innervation patterns of inner hair cells are less numerous compared with that of outer hair cells. In this paper, the electron microscopic study on the synaptic relationships between nerve endings and inner hair cells of guinea pig was discussed.
The afferent endings were 1300-4000 nm in diameter and contained a few vesicles that were 100-150 nm in diameter. Coated vesicles contained within inner hair cells were 50-100 nm in diameter. Junctional specialization such as synapses, coated vesicles, desmosomes and tubular structure was observed. Tubular structure, parallel to the presynaptic membrane accompanied with the postsynaptic membrane thickning, was considered to be one of synaptic specialization.
The efferent endings were 500-1500 nm in diameter and contained a cluster of vesicles sized 35-50 nm in diameter. Axodendritic synapses between the efferent fibers and the afferent endings were also observed.