Semicircular canal size determines the developmental onset of angular vestibuloocular reflexes in larval Xenopus.
Semicircular canal size determines the developmental onset of angular vestibuloocular reflexes in larval Xenopus.
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半规管大小决定了爪蟾幼虫角前庭眼反射的发育起始。
DOI：
10.1523/jneurosci.1288-08.2008
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发表时间：
2008-08-06
期刊：
影响因子：
--
通讯作者：
Straka H
中科院分区：
文献类型：
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作者：
Lambert FM;Beck JC;Baker R;Straka H
半规管作为角加速度传感器已有4.5亿年的历史。这种脊椎动物的适应通过在三维环境中运动时实现姿势和视觉的稳定来提高存活率。我们在非洲爪哇幼虫中使用了一种综合的神经行为学方法来证明，半规管的大小，而不是其他因素的功能，决定了角加速检测的开始。在垂直平面和水平平面上的角度前庭眼功能之前，分别在阶段47和48，前庭眼系统的每个单独组成部分都被证明是可操作的：眼外肌可以被激活，中枢神经通路完整，管状毛细胞能够引起分级反应。对于非洲爪鲨，最小半规管半径为60μm，以允许内淋巴在400o/s2的峰值加速度下产生足够的内淋巴位移以满足传感器功能。动物内部的比较表明，这种大小在垂直管中比在水平管中更早发育，对应于垂直管激活的眼球运动行为开始得更早。由于大小构成了其他脊椎动物，如斑马鱼，管诱发行为的生物物理阈值，我们认为半规管管腔和管路半径限制了所有小型脊椎动物前庭功能的开始。鉴于非洲爪哇的重力惯性加速度检测先于角加速度检测最多10天，这些结果质疑了已知的成人椭圆形和神经管传入的精确空间模式是如何在发育过程中实现的。
Semicircular canals have been sensors of angular acceleration for 450 million years. This vertebrate adaptation enhances survival by implementing postural and visual stabilization during motion in a three-dimensional environment. We used an integrated neuroethological approach in larval Xenopus to demonstrate that semicircular canal dimensions, and not the function of other elements, determines the onset of angular acceleration detection. Prior to angular vestibuloocular function in either the vertical or horizontal planes, at stages 47 and 48, respectively, each individual component of the vestibuloocular system was shown to be operational: extraocular muscles could be activated, central neural pathways were complete, and canal hair cells were capable of evoking graded responses. For Xenopus, a minimum semicircular canal radius of 60 μm was necessary to permit endolymph displacement sufficient for sensor function at peak accelerations of 400°/s2. An intra-animal comparison demonstrated that this size is reached in the vertical canals earlier in development than in the horizontal canals, corresponding to the earlier onset of vertical canal-activated ocular motor behavior. Since size constitutes a biophysical threshold for canal-evoked behavior in other vertebrates, such as zebrafish, we suggest that semicircular canal lumen and canal circuit radius is limiting the onset of vestibular function in all small vertebrates. Given that the onset of gravito-inertial acceleration detection precedes angular acceleration detection by up to 10 days in Xenopus, these results question how the known precise spatial patterning of utricular and canal afferents in adults is achieved during development.