Synaptic alterations at inner hair cells precede spiral ganglion cell loss in aging C57BL/6J mice.

Journal Article (Journal Article)

Hearing deficits have often been associated with loss of or damage to receptor hair cells and/or degeneration of spiral ganglion cells. There are, however, some physiological abnormalities that are not reliably attributed to loss of these cells. The afferent synapse between radial fibers of spiral ganglion neurons and inner hair cells (IHCs) emerges as another site that could be involved in transmission abnormalities. We tested the hypothesis that the structure of these afferent terminals would differ between young animals and older animals with significant hearing loss. Afferent endings and their synapses were examined by transmission electron microscopy at approximately 45% distance from the basal end of the cochlea in 2-3 month-old and 8-12 month-old C57BL/6J mice. The number of terminals in older animals was reduced by half compared to younger animals. In contrast, there was no difference in the density of SGCs between the age groups. Older animals featured enlarged terminals and mitochondria and enlarged postsynaptic densities and presynaptic bodies. These morphological changes may be a combination of pathologic, adaptive and compensatory responses to sensory dysfunction. Improved knowledge of these processes is necessary to understand the role of afferent connectivity in dysfunction of the aging cochlea.

Full Text

Duke Authors

Cited Authors

  • Stamataki, S; Francis, HW; Lehar, M; May, BJ; Ryugo, DK

Published Date

  • November 2006

Published In

Volume / Issue

  • 221 / 1-2

Start / End Page

  • 104 - 118

PubMed ID

  • 17005343

International Standard Serial Number (ISSN)

  • 0378-5955

Digital Object Identifier (DOI)

  • 10.1016/j.heares.2006.07.014


  • eng

Conference Location

  • Netherlands