The Experimental Study And Clinical Application On The Pathological Change Of Cochlear Hair Cell And Affect To Audiologic Function After Exposure To Intensive Noise

Objective: To investigate the effect of the intensive noise to the audiologic functionand the outer hair cells of guinea pigs, animal model of noise-induced hearing loss wasestablished.Methods: Auditory brainstem response (ABR) is adopted to investigate the hearingloss of guinea pigs caused by noise. To observe the cochlear outer hair cell damagecaused by excessive noise at microscopic and ultramicro level, cochlear basilarmembrane stretched preparation technique,light microscopy and electron microscopywere instrated.20guinea pigs were randomly divided into2groups. In the experimental group,guinea pigs were exposed to white noise at120dB SPL for8h. The control groupreceive no noise exposure. After noise exposure, animals were killed, and auditorybrainstem response(ABR) of the guinea pigs were tested to essess hearing thresholdshift.Cochlear pathology was assessed by surface preparation technique.Before and afternoise exposure, different groups of guinea pigs were studied under inverted microscopeby silver nitrate staining techniques.Transmission electron microscopy were used to investigate changes of ultrastructurein the organ of Corti and spiral ganglion cells, and to assess the effect of apoptosis in noise-induced hearing loss.Result: The threshold of wave Ⅲ was used to assess ABR threshold. After noiseexposure for8hours,the average ABR threshold was74.00±2.21dB SPL, while that ofcontrol group was28.00±2.00dB SPL.There was statistically significant difference(*P<0.01) in the average ABR threshold between the experimental group and thecontrol one.Under inverted microscope, damage due to strong noise exposure, mainly involvedthe outer hair cells in the first row inside, followed by the second row and the thirdrow. The damage of inner hair cells was less.Under transmission electron microscope, we saw the outer hair cells and spiralganglion cells pyknotic nuclei chromosomes after noise exposure.While noabnormalities were found in the control group.Conclusion: The intensive noise used in our study can cause permanent hearingthreshold shift in the guinea pig. We successfully established an animal model ofnoise-induced hearing loss. Intensive noise can cause extensive apoptosis in cochlearcells.