Myelination of Axons Corresponds with Faster Transmission Speed in the Prefrontal Cortex of Developing Male Rats.
Myelination of Axons Corresponds with Faster Transmission Speed in the Prefrontal Cortex of Developing Male Rats.
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DOI：
10.1523/eneuro.0203-18.2018
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发表时间：
2018-07-01
期刊：
影响因子：
3.4
通讯作者：
Richardson, Heather N
中科院分区：
文献类型：
--
作者：
McDougall, Sean;Vargas Riad, Wanette;Richardson, Heather N
在青春期前额叶回路的髓鞘化被认为会导致认知过程的增强和行为控制的改善。然而，虽然在人类和动物研究中常用的标准神经成像技术可以测量大的白色物质束和残余传导速度，但它们不能直接测量单个轴突的髓鞘形成或电信号沿沿着这些轴突传播的速度。在这里，我们专注于一个特定的人口的前额叶轴突，直接测量传导速度和髓鞘微结构在发育中的雄性大鼠。体外电生理方法使我们能够隔离的胼胝体（胼胝体钳小，CCFM）的前分支的前扣带内侧前额叶皮层（Cg1）的子区域的单突触的预测和测量的速度和方向的动作电位传播沿着这些轴突。我们发现，大量的轴突从CCFM投射到Cg1第V层的神经元，在青春期前[出生后第15天（PD）]和青春期中期（PD 43）之间被髓鞘包裹。这种轴突髓鞘形成的强劲增长伴随着传播速度的近一倍。由于这些轴突的直径没有年龄差异，髓磷脂可能是老年动物更快传输电信号的驱动力。轴突微观结构和生理学的这些发育变化也可能延伸到其他轴突群体，并可能成为儿童和青春期之间认知过程改善的基础。
Myelination of prefrontal circuits during adolescence is thought to lead to enhanced cognitive processing and improved behavioral control. However, while standard neuroimaging techniques commonly used in human and animal studies can measure large white matter bundles and residual conduction speed, they cannot directly measure myelination of individual axons or how fast electrical signals travel along these axons. Here we focused on a specific population of prefrontal axons to directly measure conduction velocity and myelin microstructure in developing male rats. An in vitro electrophysiological approach enabled us to isolate monosynaptic projections from the anterior branches of the corpus callosum (corpus callosum-forceps minor, CCFM) to the anterior cingulate subregion of the medial prefrontal cortex (Cg1) and to measure the speed and direction of action potentials propagating along these axons. We found that a large number of axons projecting from the CCFM to neurons in Layer V of Cg1 are ensheathed with myelin between pre-adolescence [postnatal day (PD)15] and mid-adolescence (PD43). This robust increase in axonal myelination is accompanied by a near doubling of transmission speed. As there was no age difference in the diameter of these axons, myelin is likely the driving force behind faster transmission of electrical signals in older animals. These developmental changes in axonal microstructure and physiology may extend to other axonal populations as well, and could underlie some of the improvements in cognitive processing between childhood and adolescence.