EFFECTS OF ELECTRICAL-STIMULATION OF EFFERENT OLIVOCOCHLEAR NEURONS ON CAT AUDITORY-NERVE FIBERS .2. SPONTANEOUS RATE
EFFECTS OF ELECTRICAL-STIMULATION OF EFFERENT OLIVOCOCHLEAR NEURONS ON CAT AUDITORY-NERVE FIBERS .2. SPONTANEOUS RATE
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DOI：
10.1016/0378-5955(88)90024-x
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发表时间：
1988-05-01
期刊：
影响因子：
2.8
通讯作者：
GIFFORD, ML
中科院分区：
文献类型：
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作者：
GUINAN, JJ;GIFFORD, ML
为了增加我们对耳蜗机制的理解，我们测量了猫在内耳耳蜗传出神经刺激下单个听觉神经纤维的自发放电率（SR）的变化。在传出刺激的第一秒，除了一只非常敏感的动物，SR的抑郁率高达80%外，SR的抑郁率高达35%。排除该异常猫的数据后，平均而言，随着听觉神经纤维灵敏度的增加，SR的下降幅度增加，随着原始SR的降低而增加（SR小于两个峰值/sc的数据未获得），并且在CFs约为10 kHz时具有广泛的最大值。在传出刺激被关闭后，在一些纤维中出现了“超调”，SR增加超过了原始速率。对于低SR的纤维和在传出诱导的SR抑制中表现出更大“适应性”的纤维，“超调”更大。传出刺激期间SR抑制的数据与两个假设一致：(1)在一些非常敏感的纤维中发现的比通常更强的“自发”速率的传出抑制，是因为“自发”放电在某种程度上是对声音的反应；(2)“真正的自发”放电被传出诱导的外毛细胞（ohc）的超极化通过耳蜗电位与内毛细胞（IHCs）电偶联而减少。结果表明：(1)在10 kHz附近的CF区，传出诱导的“真正自发”活动抑制最大，因为该CF区接受来自内侧传出神经的最大的OHC神经支配，并且传出诱导的OHC变化与ihc电偶联；然而(2)低中枢神经纤维对声音反应的传出抑制最大，因为OHCs上的传出末端减少基底膜的运动，这种变化从OHCs上活跃的传出突触向上传播。
In order to increase our understanding of cochlear mehanisms, we measured changes in the rate of spontaneous firing (SR) of single auditory-nerve fibers in response to the stimulation of medial olivocochlear efferents in cats. During the first second of efferent stimulation, SR was depressed by up to 35%, except in one very sensitive animal in which depressions up to 80% were found. With data from this aberrant cat excluded, the SR depression, on the average, increased as auditory-nerve fiber sensitivity increased, increased as the original SR decreased (data were not obtained for SRs less than two spikes/sc), and had a broad maximum at CFs of about 10 kHz. After the efferent stimulation was turned off, there was an "overshoot" in which the SR increased past the original rate in some fibers. The "overshoot" was larger for fibers with lower SRs and for fibers which showed larger "adaptation" in the efferent-induced depression of SR. The data on SR depression during efferent stimulation are consistent with two hypotheses: (1) that the stronger than usual efferent suppression of "spontaneous" rate found in some very sensitive fibers occurs because the "spontaneous" firing was, in part, a response to sound, and (2) that "true spontaneous" firing is reduced by the efferent-induced hyperpolarization of outer hair cells (OHCs) being electrically coupled through the endocochlear potential to inner hair cells (IHCs). It is suggested that (1) the efferent-induced suppression of "true spontaneous" activity is largest at CFs near 10 kHz because this CF region receives the greatest OHC innervation from medial efferents and the efferent-induced change in OHCs is electrically coupled to IHCs, whereas (2) the efferent suppression of responses to sound is largest at lower CFs because the efferent endings on OHCs act to decrease the motion of the basilar membrane and this change is propagated apically from the active efferent synapses on OHCs.