蝸牛反応を指標とした慢性的内耳疲労の実験的研究

概要

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To study the mechanism of noise-induced hearing loss, normal adult rabbits with parmanent implanted electrodes placed on the round window of the cochlea were exposed to pure tone stimuli at 2 KHz for 2 hours daily, and the changes of CM amplitude were observed. These animals were anesthetized with pentobarbitalsodium (Nembutal®) to suppress the acoustic reflex. The results were as follows: 1) Auditory fatigue was classified into three patterns according to the intensity of the stimuli. At an intensity of less than 80 dB, no irreversible change was recognized. At 85-105 dB, CM amplitude decreased slowly and irreversibly. In the course of the experiment, the transient recovery of CM amplitude was observed despite daily sound exposure and a recruitment-like phenomenon was seen in the input-output curve of CM. These changes appeared to be similar to clinical noise induced-hearing loss. At more than 110 dB, CM amplitude decreased quickly. These changes appeared to correspond to clinical acoustic trauma. 2) According to the above experiment, the critical intensity level was calculated to be 80-85 dB. 3) A biphasic fatigued curve was observed when irreversible cochlear damage occured. 4) There were large indivisual differences in susceptibility to sound exposure.
耳鼻と臨床会の論文