Noise-induced Outer Hair Cells' Dysfunction and Cochlear Damage in Rabbits

AUTHORS

S A Moussavi-Najarkola 1 , A Khavanin 1 , * , R Mirzaei 2 , M Salehnia 3 , A Muhammadnejad 4 , M Akbari 5

1 Dept. of Occupational Health, School of Medical Sciences, Tarbiat Modares University (TMU), [email protected], Iran

2 Dept. of Occupational Health, Health promotion research center, Zahedan University of Medical Sciences (ZUMS), Iran

3 Dept. of Anatomical Sciences, School of Medical Sciences, Tarbiat Modares University (TMU), Iran

4 Cancer Research Center, Iran Cancer Institute, Tehran University of Medical Sciences (TUMS), Iran

5 Dept. of Audiology, School of Rehabilitation, Iran University of Medical Sciences (IUMS), Iran

How to Cite: Moussavi-Najarkola S A, Khavanin A, Mirzaei R, Salehnia M, Muhammadnejad A, et al. Noise-induced Outer Hair Cells' Dysfunction and Cochlear Damage in Rabbits, Iran Red Crescent Med J. Online ahead of Print ; 14(10):647-656.

ARTICLE INFORMATION

Iranian Red Crescent Medical Journal: 14 (10); 647-656
Published Online: October 30, 2012
Article Type: Research Article
Received: November 24, 2011
Accepted: June 8, 2012

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Abstract

Background: Outer hair cells' (OHCs') dysfunctions as the extent of temporary and permanent threshold shifts (TTS and PTS) and cochlear damage were assessed in rabbits exposed to continuous noise

Methods: Twelve New Zealand white rabbits were studied in noise (N) (n=6; exposed to continuous noise; 95 dB SPL, 500-8000 Hz for 8 h per day during 5 consecutive days) and control (C) (n=6; not exposed to noise). OHCs' functions were assessed by distortion product otoacoustic emission (DPOAE) level (Ldp) measurements in different periods and comparing TTS and PTS. Animals were anaesthetized by CO2; cochleae were extracted, fixed in 10% formaldehyde for 48 hours, decalcified by 10% nitric acid for 24 hours, and dehydrated, embedded, sectioned 5 m thickness and stained by Hematoxylin and Eosin for light microscopy.

Results: The most and least Ldp or TTS or PTS were related to 5888.50 Hz and 588.00 Hz respectively in noise subjected rabbits (P<0.05). TTS and PTS were decreased up to 17.79 dB and to 16.01 dB respectively. TTS were more than PTS over all test frequencies, especially at 5888.50 Hz (P<0.05). Ldp or TTS or PTS were found to be equal across ears (P>0.05). Severely vacuolated OHCs, pyknotic IHCs, swollen SC, and slightly thickened BM were found.

Conclusion: Continuous noise extensively led to OHCs' dysfunctions as decreased Ldp (both TTS and PTS) and highly damage to cochlea.

Keywords

Noise-induced Hearing Loss Outer hair cells' function Cochlear damage Distortion product Otoacoustic emissions

© 2012, Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited.

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