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Cochlear neuropathy in the rat exposed for a long period to moderate‐intensity noises
Author(s) -
Gannouni Noura,
Lenoir Marc,
Ben Rhouma Khemais,
El May Michèle,
Tebourbi Olfa,
Puel Jean Luc,
Mhamdi Abada
Publication year - 2015
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.23567
Subject(s) - cochlea , spiral ganglion , presbycusis , audiology , noise (video) , intensity (physics) , hair cell , sensory system , biology , cochlear nerve , lipofuscin , medicine , neuroscience , hearing loss , physics , image (mathematics) , quantum mechanics , artificial intelligence , computer science
Damaging effects on the cochlea of high‐intensity acoustic overexposures have been extensively documented, but only few works have focused on the danger of moderate noise levels. Using scanning and transmission electron microscopy, we explored the noise‐induced neuroepithelial changes that occur in the cochlea of rats subjected to moderate intensities, 70 and 85 dB SPL, for an extended period of time (6 hr/day over 3 months). Although the full quota of outer and inner sensory hair cells remained present, we detected discrete abnormalities, likely resulting from metabolic impairment, in both types of hair cell within the basal region of the cochlea. In contrast, important noise‐dependent losses of spiral ganglion neurons had occurred. In addition, we found cytoplasmic accumulations of lipofuscin‐like aggregates in most of the surviving cochlear neurons. These results strongly suggest that noise levels comparable to those of certain working environments, with sufficient exposure duration, pose a severe risk to the cochlea. Moreover, our data support the notion that long‐duration exposure to moderate noise is a causative factor of presbycusis. © 2015 Wiley Periodicals, Inc.