Sound-Evoked Activity Influences Myelination of Brainstem Axons in the Trapezoid Body.
Sound-Evoked Activity Influences Myelination of Brainstem Axons in the Trapezoid Body.
复制标题
声音诱发的活动会影响梯形体内脑干轴突的髓鞘形成。
DOI：
10.1523/jneurosci.3728-16.2017
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发表时间：
2017-08-23
期刊：
影响因子：
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通讯作者：
Kopp-Scheinpflug C
中科院分区：
文献类型：
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作者：
Sinclair JL;Fischl MJ;Alexandrova O;Heβ M;Grothe B;Leibold C;Kopp-Scheinpflug C
髓鞘形成的可塑性代表了一种通过平衡功能需求与代谢和空间限制来调节信息流的机制。听觉系统有大量髓鞘，并在哺乳动物CNS中观察到的动作电位产生频率和速度的上限下工作。本研究旨在描述梯形体（一种中枢听觉纤维束）内髓鞘的发育特征，并确定感觉经验对两性小鼠这一过程的影响。我们发现，在体外传导速度加倍听力发作后，支持高频放电的能力同时增加。在此期间，梯形体轴突的直径和髓鞘的厚度增加一倍，在25至35日龄之间达到成熟样厚度。用耳塞诱发听阈升高≥ 50 dB。如果在听力发作时引入，梯形体纤维比年龄匹配的对照组发育更薄的轴突和髓鞘。如果在成年期堵塞，最厚的梯形体纤维也显示髓鞘减少。这些数据表明，在髓鞘的发育和维持中需要感觉活动，并在髓鞘可塑性的研究中具有重要意义，以及这如何与外周损伤后的感音神经性听力损失相关。听觉系统有许多机制来最大化其传入纤维的动态范围，这些传入纤维在动作电位产生、精度和速度的生理极限下工作。在这项研究中，我们第一次证明，外周活动的变化改变了感觉神经元髓鞘的厚度，不仅在发展中，而且在成熟的动物。目前的研究表明，中枢神经系统髓鞘形成的变化发生作为一个下游机制后，外周赤字。考虑到双耳听觉处理所需的亚毫秒级时间精度，髓鞘形成减少可能会增加感音神经性听力障碍。
Plasticity of myelination represents a mechanism to tune the flow of information by balancing functional requirements with metabolic and spatial constraints. The auditory system is heavily myelinated and operates at the upper limits of action potential generation frequency and speed observed in the mammalian CNS. This study aimed to characterize the development of myelin within the trapezoid body, a central auditory fiber tract, and determine the influence sensory experience has on this process in mice of both sexes. We find that in vitro conduction speed doubles following hearing onset and the ability to support high-frequency firing increases concurrently. Also in this time, the diameter of trapezoid body axons and the thickness of myelin double, reaching mature-like thickness between 25 and 35 d of age. Earplugs were used to induce ∼50 dB elevation in auditory thresholds. If introduced at hearing onset, trapezoid body fibers developed thinner axons and myelin than age-matched controls. If plugged during adulthood, the thickest trapezoid body fibers also showed a decrease in myelin. These data demonstrate the need for sensory activity in both development and maintenance of myelin and have important implications in the study of myelin plasticity and how this could relate to sensorineural hearing loss following peripheral impairment. SIGNIFICANCE STATEMENT The auditory system has many mechanisms to maximize the dynamic range of its afferent fibers, which operate at the physiological limit of action potential generation, precision, and speed. In this study we demonstrate for the first time that changes in peripheral activity modifies the thickness of myelin in sensory neurons, not only in development but also in mature animals. The current study suggests that changes in CNS myelination occur as a downstream mechanism following peripheral deficit. Given the required submillisecond temporal precision for binaural auditory processing, reduced myelination might augment sensorineural hearing impairment.