Department of Physiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706, USA.
J Neurosci. 2010 Mar 10;30(10):3555-66. doi: 10.1523/JNEUROSCI.4551-09.2010.
The node of Ranvier is a tiny segment of a myelinated fiber with various types of specializations adapted for generation of high-speed nerve impulses. It is ionically specialized with respect to ion channel segregation and ionic fluxes, and metabolically specialized in ionic pump expression and mitochondrial density augmentation. This report examines the interplay of three important parameters (calcium fluxes, Na pumps, mitochondrial motility) at nodes of Ranvier in frog during normal nerve activity. First, we used calcium dyes to resolve a highly localized elevation in axonal calcium at a node of Ranvier during action potentials, and showed that this calcium elevation retards mitochondrial motility during nerve impulses. Second, we found, surprisingly, that physiologic activation of the Na pumps retards mitochondrial motility. Blocking Na pumps alone greatly prevents action potentials from retarding mitochondrial motility, which reveals that mitochondrial motility is coupled to Na/K-ATPase. In conclusion, we suggest that during normal nerve activity, Ca elevation and activation of Na/K-ATPase act, possibly in a synergistic manner, to recruit mitochondria to a node of Ranvier to match metabolic needs.
郎飞结是有髓纤维的微小片段，具有各种适应高速神经冲动产生的特殊结构。它在离子通道分隔和离子流方面具有离子特异性，在离子泵表达和线粒体密度增加方面具有代谢特异性。本报告研究了在正常神经活动期间青蛙郎飞结处三个重要参数（钙流、Na 泵、线粒体运动）的相互作用。首先，我们使用钙染料来解析动作电位期间郎飞结处轴突钙的高度局部升高，并表明这种钙升高会在神经冲动期间延迟线粒体运动。其次，我们令人惊讶地发现，Na 泵的生理性激活会延迟线粒体运动。单独阻断 Na 泵会极大地防止动作电位延迟线粒体运动，这表明线粒体运动与 Na/K-ATP 酶偶联。总之，我们认为在正常神经活动期间，Ca 升高和 Na/K-ATP 酶的激活可能以协同方式作用，将线粒体募集到郎飞结以满足代谢需求。
