@Article{sv.2020.09880,
AUTHOR = {Parvane Mahdi, Akram Pourbakht, Vahid Pirhajati Mahabadi, Alireza Karimi Yazdi, Mahtab Rabbani Anari, Mohammad Kamali},
TITLE = {Cochlear Synaptopathy Following Noise Exposure in Guinea Pigs: Its Electrophysiological and Histological Assessments},
JOURNAL = {Sound \& Vibration},
VOLUME = {54},
YEAR = {2020},
NUMBER = {3},
PAGES = {163--177},
URL = {http://www.techscience.com/sv/v54n3/40078},
ISSN = {2693-1443},
ABSTRACT = {Exposure to high level of noise, may cause the permanent cochlear
synaptic degeneration. In present study, a model of noise induced cochlear synaptopathy was established and the electrophysiological and histological metrics for
its assessment was designed. 6 guinea pigs were subjected to a synaptopathic
noise (octave band of 4 kHz at 104 dB SPL, for 2-h). The amplitude growth curve
of Auditory Brainstem Response (ABR) wave-I and wave-III latency shift in presence of noise were calculated. These indexes were considered in pre-exposure,
1 day post exposure (1DPE), 1 week post exposure (1WPE) and 1 month post
exposure (1MPE) to noise. Finally, the samples were histologically analyzed.
ABR wave-I amplitude was different between pre and 1DPE (<i>p</i>-value ≤ 0.05).
However, at 1WPE, it was recovered at low intensities but at 70 dB SPL and
above, the differences persisted even till 1MPE. In masked ABR, the latency shift
of wave-III was different between pre and 3 post exposure assessments (p-value ≤
0.05). Electro-microscopic analysis confirmed the synaptic degeneration, as the
ribbons were larger than normal, hollow inside, and spherical and irregular in
shape, also, the post synaptic density was abnormally thick and missed its flat
orientation. These data revealed that noise at level below that can produce permanent hearing loss, can incur synaptic injury. So, noise is considered to be more
damaging than previously thought. Accordingly, designing tools for clinical
assessment of synaptopathy is beneficial in comprehensive auditory evaluation
of those with history of noise exposure and also in hearing protection planning.},
DOI = {10.32604/sv.2020.09880}
}