Neuroscience Department, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT 0200, Australia.
Neuron. 2011 Aug 25;71(4):671-82. doi: 10.1016/j.neuron.2011.06.024.
In central neurons the first node of Ranvier is located at the first axonal branchpoint, ∼ 100 μm from the axon initial segment where synaptic inputs are integrated and converted into action potentials (APs). Whether the first node contributes to this signal transformation is not well understood. Here it was found that in neocortical layer 5 axons, the first branchpoint is required for intrinsic high-frequency (≥ 100 Hz) AP bursts. Furthermore, block of nodal Na(+) channels or axotomy of the first node in intrinsically bursting neurons depolarized the somatic AP voltage threshold (∼ 5 mV) and eliminated APs selectively within a high-frequency cluster in response to steady currents or simulated synaptic inputs. These results indicate that nodal persistent Na(+) current exerts an anterograde influence on AP initiation in the axon initial segment, revealing a computational role of the first node of Ranvier beyond conduction of the propagating AP.
在中枢神经元中，郎飞氏结的第一个结位于距轴突起始段约 100μm 的第一个轴突分支点，此处整合突触输入并将其转换为动作电位（AP）。第一个结是否有助于这种信号转换尚不清楚。本研究发现，在新皮层 5 层的轴突中，第一个分支点对于内在高频（≥100Hz）AP 爆发是必需的。此外，内在爆发神经元的结区 Na+通道阻断或第一个结区的轴突切断，会使体 AP 电压阈值去极化（约 5mV），并在对稳定电流或模拟突触输入的反应中，选择性地消除高频簇内的 AP。这些结果表明，结区持续的 Na+电流对轴突起始段中的 AP 起始具有顺行影响，揭示了郎飞氏结第一个结的计算作用超出了传播性 AP 的传导。
