Wang J, Powers N L, Hofstetter P, Trautwein P, Ding D, Salvi R
Hearing Research Laboratory, State University of New York at Buffalo, NY 14214, USA.
Hear Res. 1997 May;107(1-2):67-82. doi: 10.1016/s0378-5955(97)00020-8.
Current theories assume that the outer hair cells (OHC) are responsible for the sharp tuning and exquisite sensitivity of the ear whereas inner hair cells (IHC) are mainly responsible for transmitting acoustic information to the central nervous system. To further evaluate this model, we used a single (38 mg/kg) or double dose (38 mg/kg, 2 times) of carboplatin to produce a moderate (20-28%) or severe (60-95%) IHC loss while sparing a large proportion of the OHCs. The surviving OHCs were functionally intact as indicated by normal cochlear microphonic (CM) potentials and distortion product otoacoustic emissions (DPOAE). Single-unit responses were recorded from auditory nerve fibers to determine the effects of the moderate or severe IHC loss on the output of the surviving IHCs. Most neurons that responded to sound in the single-dose group had normal or near-normal thresholds and normal tuning. Relatively few neurons in the double-dose group responded to sound because of the severe IHC loss. The neurons that did respond to sound had narrow tuning curves. Some neurons in the double-dose group also had thresholds that were within the normal range, but most had thresholds that were elevated a mild-to-moderate degree. These results indicate that intact IHCs can retain relatively normal sensitivity and tuning despite massive IHC loss in surrounding regions of the cochlea. However, the spontaneous and driven discharge rates of neurons in the carboplatin-treated animals were significantly lower than normal. These changes could conceivably be due to sublethal damage to surviving IHCs or to postsynaptic dysfunction in the auditory nerve.
当前理论认为，外毛细胞（OHC）负责耳朵的尖锐调谐和极高灵敏度，而内毛细胞（IHC）主要负责将声学信息传递至中枢神经系统。为进一步评估该模型，我们使用单剂量（38毫克/千克）或双剂量（38毫克/千克，2次）的卡铂，造成中度（20 - 28%）或重度（60 - 95%）的内毛细胞损失，同时使大部分外毛细胞得以保留。如正常的耳蜗微音电位（CM）和畸变产物耳声发射（DPOAE）所示，存活的外毛细胞功能完好。从听神经纤维记录单单位反应，以确定中度或重度内毛细胞损失对存活内毛细胞输出的影响。单剂量组中大多数对声音有反应的神经元具有正常或接近正常的阈值和调谐。由于重度内毛细胞损失，双剂量组中相对较少的神经元对声音有反应。那些确实对声音有反应的神经元具有狭窄的调谐曲线。双剂量组中的一些神经元阈值也在正常范围内，但大多数神经元的阈值有轻度到中度的升高。这些结果表明，尽管耳蜗周围区域存在大量内毛细胞损失，但完整的内毛细胞仍可保持相对正常的灵敏度和调谐。然而，卡铂处理动物中神经元的自发放电率和驱动放电率明显低于正常水平。这些变化可能是由于存活的内毛细胞受到亚致死损伤或听神经中的突触后功能障碍所致。
