Comparison and contrast of noise-induced hyperactivity in the dorsal cochlear nucleus and inferior colliculus.
Comparison and contrast of noise-induced hyperactivity in the dorsal cochlear nucleus and inferior colliculus.
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DOI：
10.1016/j.heares.2012.04.003
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发表时间：
2013-01
期刊：
影响因子：
2.8
通讯作者：
Kaltenbach JA
中科院分区：
文献类型：
--
作者：
Manzoor NF;Gao Y;Licari F;Kaltenbach JA
中枢听觉系统的过度活跃是噪声性耳鸣动物模型的主要生理特征之一。虽然多动发生在听觉系统的各个层次，但尚不清楚起源于一个核团的多动在多大程度上有助于听觉系统更高层次的多动。在这项研究中，我们比较了耳蜗背核（DCN）和下丘（IC）的过度活动的时间进程和音调分布模式。通过DCN的被动中继在IC中获得多动的模型将预测两个核团显示出类似的多动的时间过程和音调分布图。通过补偿性可塑性机制获得IC中的活动过度的模型将预测IC和DCN将在这些特征中显示出差异，因为每个都调整相反极性的自发活动的变化。为了测试这两种机制的作用，将动物暴露于强烈的多动诱导音（10 kHz，115 dB SPL，4小时），然后在三个不同的暴露后恢复时间（暴露后1至6周）进行电生理学研究。对于每个时间帧，多单位自发活动被映射为DCN和IC中的音调梯度沿着位置的函数。从两个核的活动曲线的比较表明，随着时间的推移，朝着增加的活动，并最终在一个类似的tonotopic位置的过度活跃的中央峰的发展类似的进展。这些相似之处表明，活动轮廓的形状主要是由耳蜗核的被动中继决定的。然而，活动的绝对水平通常在IC中比在DCN中低得多，这表明过度活动的幅度被抑制大大减弱。
Induction of hyperactivity in the central auditory system is one of the major physiological hallmarks of animal models of noise-induced tinnitus. Although hyperactivity occurs at various levels of the auditory system, it is not clear to what extent hyperactivity originating in one nucleus contributes to hyperactivity at higher levels of the auditory system. In this study we compared the time courses and tonotopic distribution patterns of hyperactivity in the dorsal cochlear nucleus (DCN) and inferior colliculus (IC). A model of acquisition of hyperactivity in the IC by passive relay from the DCN would predict that the two nuclei show similar time courses and tonotopic profiles of hyperactivity. A model of acquisition of hyperactivity in the IC by compensatory plasticity mechanisms would predict that the IC and DCN would show differences in these features, since each adjusts to changes of spontaneous activity of opposite polarity. To test the role of these two mechanisms, animals were exposed to an intense hyperactivity-inducing tone (10 kHz, 115 dB SPL, 4 hours) then studied electrophysiologically at three different post-exposure recovery times (from 1 to 6 weeks after exposure). For each time frame, multiunit spontaneous activity was mapped as a function of location along the tonotopic gradient in the DCN and IC. Comparison of activity profiles from the two nuclei showed a similar progression toward increased activity over time and culminated in the development of a central peak of hyperactivity at a similar tonotopic location. These similarities suggest that the shape of the activity profile is determined primarily by passive relay from the cochlear nucleus. However, the absolute levels of activity were generally much lower in the IC than in the DCN, suggesting that the magnitude of hyperactivity is greatly attenuated by inhibition.
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