窄带噪声暴露后豚鼠听阈偏移及毛细胞的损伤

为了探讨听觉损伤与毛细胞损伤的关系,本实验比较了噪声暴露后豚鼠皮层听阈及其与基底膜单位长度上毛细胞损伤率的关系。暴露声源中心频率1000Hz,为1/3倍频程的窄带噪声。强度为136dB作用1小时。108dB每天暴露1小时,5天/周连续1个月。结果表明,毛细胞损伤呈灶性,损伤部位与周围界线十分分明。毛细胞损伤在豚鼠间及左右耳间均存在相当程度的个体差异。136dB暴露,毛细胞损伤最重的部位在基底膜1.5转到2.5转之间,符合1000Hz声音在基底膜的最大振动范围。108dB的损伤部位局限在1.5转,其范围及程度明显轻于136dB。136dB造成的听阈偏移高于108dB,尤其在4、8 KHz高频听阈偏移最明显,但耳蜗底转毛细胞多无明显损伤。

HEARING THRESHOLD SHIFT AND HAIR CELL LOSS IN GUINEA PIGS EXPOSED TO NARROW-BAND NOISE

To explore the relationship between hearing damage and hair cell loss, we studied the relationship of cortical hearing threshold with hair cell loss rate in an unit of length of the basilar membrane in guinea pigs. A1/3 octave narrow-band source of noise centered at 1000 Hz was used in the exper-iment. The animals were exposed to 136dB for an hour and to 108 dB cont-inously for a month (1h/day and 5d/week ) .The results of the experiment showed that the hair cell loss appeared to be focus-like with the damaged regions clearly demarcated from the periphery, and presented a considerable individual differences both between the animals and between the left and right ears. At 136dB the maximum loss was located in turn 1.5 to 2.5, which conformed with the maximum amplitude of vibration produced by & 1000 Hz sound on the basilar membrane. At 108 dB the loss was primarily located in turn 1.5 and was obviously smaller than that at 136 dB in severity and amplitude. The hearing threshold shift produced at 136 dB was larger than that at 108 dB, and the shifts at 4 and 8 kHz were most remarkable, however, no significant damage was done to hair cells in the base turn of cochlea.