Abstract
Objectives: This study was designed to determine the morphology changes of noise-induced hidden hearing loss (NIHHL). Method: Fifteen guinea pigs were divided into three groups: noise-induced hidden hearing loss (NIHHL) group, noise-induced hearing loss (NIHL) group, and normal control group. For the noise-induced hidden hearing loss group, the guinea pigs were exposed to 15 times of impulse noise at one time. For the noise-induced hearing loss group, the animals were exposed to a total of 200 times of impulse noise in two times, and the time interval is 24 hours. Auditory brain response (ABR) was tested before, immediately, 24h, 1week, and one month after noise exposure to evaluate cochlear physiology changes. One month after noise exposure, all guinea pigs in three groups were sacrificed, and basement membranes were carefully dissected immediately after ABR tests. The cochlea samples were observed by transmission electron microscopy (TEM) to found out the monograph changes. Result: The ABR results showed that 15 times of impulse noise exposure could cause NIHHL in guinea pigs and 200 times could cause completely hearing loss. Impulse noise exposure could cause a dramatic increase in chondriosome in the inner hair cell. The structures of ribbon synapses and heminodes were also obviously impaired compared to the normal group. The nerve fibers and myelin sheaths remained intact after impulse noise exposure. Conclusion: This research revealed for the first time that impulse noise could cause hidden hearing loss, and the changes in inner hair cells, ribbon synapse, and heminode all played a vital role in the pathogenesis of hidden hearing loss.
The Protective effect of the endoplasmic reticulum stress-related factors BiP/GRP78 and CHOP/Gadd153 on noise-induced hearing loss in guinea pigs
