title: Auditory nerve perinodal dysmyelination in noise-induced hearing loss.
abstract: Exposure to loud sound (acoustic overexposure; AOE) induces hearing loss and damages cellular structures at multiple locations in the auditory pathway. Whether AOE can also induce changes in myelin sheaths of the auditory nerve (AN) is an important issue particularly because these changes can be responsible for impaired action potential propagation along the AN. Here we investigate the effects of AOE on morphological and electrophysiological features of the centrally directed part of the rat AN projecting from the cochlear spiral ganglion to brainstem cochlear nuclei. Using electron microscopy and immunocytochemistry, we show that AOE elongates the AN nodes of Ranvier and triggers notable perinodal morphological changes. Compound action potential recordings of the AN coupled to biophysical modeling demonstrated that these nodal and perinodal structural changes were associated with decreased conduction velocity and conduction block. Furthermore, AOE decreased the number of release sites in the cochlear nuclei associated with the reduced amplitudes of EPSCs evoked by AN stimulation. In conclusion, AN dysmyelination may be of fundamental importance in auditory impairment following exposure to loud sound.
authors: Department of Cell Physiology and Pharmacology, and Electron Microscopy Facility, University of Leicester, Leicester LE1 9HN, United Kingdom.
authors: Thomas
authors: T
authors: Tagoe
authors: Matt
authors: M
authors: Barker
authors: Andrew
authors: A
authors: Jones
authors: Natalie
authors: N
authors: Allcock
authors: Martine
authors: M
authors: Hamann
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D003056:Cochlear Nerve / Q000473:pathology* / Q000503:physiopathology; D004195:Disease Models, Animal; D005072:Evoked Potentials, Auditory / Q000502:physiology; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D005260:Female; D006317:Hearing Loss, Noise-Induced / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D009186:Myelin Sheath / Q000473:pathology*; D018408:Patch-Clamp Techniques; D011901:Ranvier's Nodes / Q000473:pathology*; D051381:Rats; D017208:Rats, Wistar
keywords: central auditory pathway; deafness; dorsal cochlear nucleus; dysmyelination; hearing loss; myelin