Efferent synapses return to inner hair cells in the aging cochlea.

Published

Journal Article

Efferent innervation of the cochlea undergoes extensive modification early in development, but it is unclear if efferent synapses are modified by age, hearing loss, or both. Structural alterations in the cochlea affecting information transfer from the auditory periphery to the brain may contribute to age-related hearing deficits. We investigated changes to efferent innervation in the vicinity of inner hair cells (IHCs) in young and old C57BL/6 mice using transmission electron microscopy to reveal increased efferent innervation of IHCs in older animals. Efferent contacts on IHCs contained focal presynaptic accumulations of small vesicles. Synaptic vesicle size and shape were heterogeneous. Postsynaptic cisterns were occasionally observed. Increased IHC efferent innervation was associated with a smaller number of afferent synapses per IHC, increased outer hair cell loss, and elevated auditory brainstem response thresholds. Efferent axons also formed synapses on afferent dendrites but with a reduced prevalence in older animals. Age-related reduction of afferent activity may engage signaling pathways that support the return to an immature state of efferent innervation of the cochlea.

Full Text

Duke Authors

Cited Authors

  • Lauer, AM; Fuchs, PA; Ryugo, DK; Francis, HW

Published Date

  • December 2012

Published In

Volume / Issue

  • 33 / 12

Start / End Page

  • 2892 - 2902

PubMed ID

  • 22405044

Pubmed Central ID

  • 22405044

Electronic International Standard Serial Number (EISSN)

  • 1558-1497

Digital Object Identifier (DOI)

  • 10.1016/j.neurobiolaging.2012.02.007

Language

  • eng

Conference Location

  • United States