Kole Maarten H P, Letzkus Johannes J, Stuart Greg J
Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, ACT 0200, Australia.
Neuron. 2007 Aug 16;55(4):633-47. doi: 10.1016/j.neuron.2007.07.031.
Action potentials are binary signals that transmit information via their rate and temporal pattern. In this context, the axon is thought of as a transmission line, devoid of a role in neuronal computation. Here, we show a highly localized role of axonal Kv1 potassium channels in shaping the action potential waveform in the axon initial segment (AIS) of layer 5 pyramidal neurons independent of the soma. Cell-attached recordings revealed a 10-fold increase in Kv1 channel density over the first 50 microm of the AIS. Inactivation of AIS and proximal axonal Kv1 channels, as occurs during slow subthreshold somatodendritic depolarizations, led to a distance-dependent broadening of axonal action potentials, as well as an increase in synaptic strength at proximal axonal terminals. Thus, Kv1 channels are strategically positioned to integrate slow subthreshold signals, providing control of the presynaptic action potential waveform and synaptic coupling in local cortical circuits.
动作电位是通过其发放频率和时间模式来传递信息的二元信号。在这种情况下，轴突被视为一条传输线，在神经元计算中不发挥作用。在此，我们展示了轴突Kv1钾通道在塑造第5层锥体神经元轴突起始段（AIS）动作电位波形方面具有高度局部化的作用，且与胞体无关。细胞贴附式记录显示，在AIS的前50微米内，Kv1通道密度增加了10倍。在缓慢的阈下树突 - 胞体去极化过程中发生的AIS和近端轴突Kv1通道失活，导致轴突动作电位出现距离依赖性增宽，以及近端轴突终末处突触强度增加。因此，Kv1通道处于战略性位置以整合缓慢的阈下信号，从而控制局部皮质回路中的突触前动作电位波形和突触耦合。
