Effects of Axonal Topology on the Somatic Modulation of Synaptic Outputs
Effects of Axonal Topology on the Somatic Modulation of Synaptic Outputs
复制标题
DOI：
10.1523/jneurosci.5365-11.2012
复制
发表时间：
2012-02
期刊：
影响因子：
--
通讯作者：
T. Sasaki;N. Matsuki;Y. Ikegaya
中科院分区：
文献类型：
--
作者：
T. Sasaki;N. Matsuki;Y. Ikegaya
神经元胞体的去极化通过长距离轴突电缆特性增加突触后神经元的突触输出。在这里，我们报告了这种躯体影响的范围不仅受到轴突路径长度的空间限制，而且还受到依赖于分支的轴突直径的减少的限制。对大鼠海马CA3区锥体细胞多个轴突分支动作电位(AP)的细胞附着式记录显示，胞体去极化20 mV后，AP变宽，并在沿轴突向下传播的过程中恢复到正常宽度。AP的缩小取决于AP行进的距离和AP通过的轴突分支点的数量。这些发现被突触前突触周围AP诱导的钙升高的光学成像所证实，表明体膜电位改变了胞体附近的突触输出，但不改变长投射输出。与这一预测一致的是，来自突触连接神经元的全细胞记录显示，突触前CA3锥体细胞的去极化促进了突触传递到附近的CA3锥体细胞，但不利于突触传递到CA3或CA1中的远处锥体细胞。因此，轴突几何结构使突触输出能够根据靶位置的不同而进行差异调制。
Depolarization of the neuronal soma augments synaptic output onto postsynaptic neurons via long-range, axonal cable properties. Here, we report that the range of this somatic influence is spatially restricted by not only axonal path length but also a branching-dependent decrease in axon diameter. Cell-attached recordings of action potentials (APs) from multiple axon branches of a rat hippocampal CA3 pyramidal cell revealed that an AP was broadened following a 20 mV depolarization of the soma and reverted to a normal width during propagation down the axon. The narrowing of the AP depended on the distance traveled by the AP and on the number of axon branch points through which the AP passed. These findings were confirmed by optical imaging of AP-induced calcium elevations in presynaptic boutons, suggesting that the somatic membrane potential modifies synaptic outputs near the soma but not long-projection outputs. Consistent with this prediction, whole-cell recordings from synaptically connected neurons revealed that depolarization of presynaptic CA3 pyramidal cells facilitated synaptic transmission to nearby CA3 pyramidal cells, but not to distant pyramidal cells in CA3 or CA1. Therefore, axonal geometry enables the differential modulation of synaptic output depending on target location.