Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia.
Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia.
Brain Res. 2021 May 1;1758:147331. doi: 10.1016/j.brainres.2021.147331. Epub 2021 Feb 2.
During spaceflight and immediately after it, adaptive neuroplastic changes occur in the sensorimotor structures of the central nervous system, which are associated with changes of mainly vestibular and visual signals. It is known that the movement of the eyeball in the vertical direction is carried out by muscles that are innervated by the trochlear nerve (CN IV) and the oculomotor nerve (CN III). To elucidate the cellular processes underlying the atypical vertical nystagmus that occurs under microgravity conditions, it seems necessary to study the state of these nuclei in animals in more detail after prolonged space flights. We carried out a qualitative and quantitative light-optical and ultrastructural analysis of the nuclei of the trochlear nerve in mice after a 30-day flight on the Bion-M1 biosatellite. As a result, it was shown that the dendrites of motoneurons in the nucleus of the trochlear nerve significantly reorganized their geometry and orientation under microgravity conditions. The number of dendritic branches was increased, possibly in order to amplify the reduced signal flow. To ensure such plastic changes, the number and size of mitochondria in the soma of motoneurons and in axons coming from the vestibular structures increased. Thus, the main role in the adaptation of the trochlear nucleus to microgravity conditions, apparently, belongs to the dendrites of motoneurons, which rearrange their structure and function to enhance the flow of sensory information. These results complement our knowledge of the causes of atypical nystagmus in microgravity.
在航天飞行期间及其后，中枢神经系统的感觉运动结构会发生适应性神经可塑性变化，这与主要是前庭和视觉信号的变化有关。众所周知，眼球在垂直方向上的运动是由动眼神经（CN III）和滑车神经（CN IV）支配的肌肉完成的。为了阐明微重力条件下发生的非典型垂直眼球震颤的细胞过程，似乎有必要在长时间的太空飞行后更详细地研究这些核在动物中的状态。我们在 Bion-M1 生物卫星上进行了为期 30 天的飞行后，对小鼠的滑车神经核进行了定性和定量的光镜和超微结构分析。结果表明，在微重力条件下，滑车神经核中的运动神经元的树突明显改变了它们的几何形状和方向。树突分支的数量增加了，可能是为了放大减少的信号流。为了确保这种可塑性变化，运动神经元的体和来自前庭结构的轴突中的线粒体的数量和大小增加了。因此，运动神经元的树突在适应微重力条件方面起着主要作用，它们改变其结构和功能以增强感觉信息的流动。这些结果补充了我们对微重力条件下非典型眼球震颤原因的认识。
