Laboratorio Cajal de Circuitos Corticales, Centro de Tecnología Biomédica, Universidad Politécnica de Madrid, Pozuelo de Alarcón, Madrid, Spain.
Departamento de Neurobiología Funcional y de Sistemas, Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
Cereb Cortex. 2018 Oct 1;28(10):3673-3684. doi: 10.1093/cercor/bhy159.
Mitochondria play a key role in energy production and calcium buffering, among many other functions. They provide most of the energy required by neurons, and they are transported along axons and dendrites to the regions of higher energy demands. We have used focused ion beam milling and scanning electron microscopy (FIB/SEM) to obtain stacks of serial sections from the somatosensory cortex of the juvenile rat. We have estimated the volume fraction occupied by mitochondria and their distribution between dendritic, axonal, and nonsynaptic processes. The volume fraction of mitochondria increased from layer I (4.59%) to reach its maximum in layer IV (7.74%) and decreased to its minimum in layer VI (4.03%). On average, 44% of mitochondrial volume was located in dendrites, 15% in axons and 41% in nonsynaptic elements. Given that dendrites, axons, and nonsynaptic elements occupied 38%, 23%, and 39% of the neuropil, respectively, it can be concluded that dendrites are proportionally richer in mitochondria with respect to axons, supporting the notion that most energy consumption takes place at the postsynaptic side. We also found a positive correlation between the volume fraction of mitochondria located in neuronal processes and the density of synapses.
线粒体在能量产生和钙缓冲等许多功能中发挥着关键作用。它们为神经元提供所需的大部分能量，并沿着轴突和树突运输到能量需求较高的区域。我们使用聚焦离子束铣削和扫描电子显微镜（FIB/SEM）从幼年大鼠的体感皮层中获得了一系列连续切片的堆栈。我们估计了线粒体的体积分数及其在树突、轴突和非突触过程之间的分布。线粒体的体积分数从第 I 层（4.59%）增加到第 IV 层（7.74%）的最大值，然后减少到第 VI 层（4.03%）的最小值。平均而言，线粒体体积的 44%位于树突中，15%位于轴突中，41%位于非突触元件中。鉴于树突、轴突和非突触元件分别占据神经胶的 38%、23%和 39%，可以得出结论，与轴突相比，树突在比例上富含线粒体，这支持了大多数能量消耗发生在突触后侧的观点。我们还发现位于神经元过程中的线粒体的体积分数与突触密度之间存在正相关关系。
