Noise-induced Outer Hair Cells' Dysfunction and Cochlear Damage in Rabbits
نویسندگان
1 Dept. of Occupational Health, Health promotion research center, Zahedan University of Medical Sciences (ZUMS), Zahedan, Iran
2 Dept. of Anatomical Sciences, School of Medical Sciences, Tarbiat Modares University (TMU), Tehran, Iran
3 Cancer Research Center, Iran Cancer Institute, Tehran University of Medical Sciences (TUMS), Tehran, Iran
4 Dept. of Audiology, School of Rehabilitation, Iran University of Medical Sciences (IUMS), Tehran, Iran
5 Dept. of Occupational Health, School of Medical Sciences, Tarbiat Modares University (TMU), Tehran, Iran
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doi
چکیده
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 lightmicroscopy.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 dBrespectively. 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.
