Brunner János, Arszovszki Antónia, Tarcsay Gergely, Szabadics János
HUN-REN Institute of Experimental Medicine, Budapest, Hungary.
PLoS Biol. 2024 Dec 2;22(12):e3002929. doi: 10.1371/journal.pbio.3002929. eCollection 2024 Dec.
Active conductances tune the kinetics of axonal action potentials (APs) to support specialized functions of neuron types. However, the temporal characteristics of voltage signals strongly depend on the size of neuronal structures, as capacitive and resistive effects slow down voltage discharges in the membranes of small elements. Axonal action potentials are particularly sensitive to these inherent biophysical effects because of the large diameter variabilities within individual axons, potentially implying bouton size-dependent synaptic effects. However, using direct patch-clamp recordings and voltage imaging in small hippocampal axons in acute slices from rat brains, we demonstrate that AP shapes remain uniform within the same axons, even across an order of magnitude difference in caliber. Our results show that smaller axonal structures have more Kv1 potassium channels that locally re-accelerate AP repolarization and contribute to size-independent APs, while they do not preclude the plasticity of AP shapes. Thus, size-independent axonal APs ensure consistent digital signals for each synapse within axons of same types.
主动电导调节轴突动作电位（APs）的动力学，以支持不同类型神经元的特定功能。然而，电压信号的时间特性很大程度上取决于神经元结构的大小，因为电容和电阻效应会减缓小元件膜中电压放电的速度。轴突动作电位对这些固有的生物物理效应特别敏感，因为单个轴突内存在较大的直径差异，这可能意味着突触效应依赖于终扣大小。然而，通过在大鼠大脑急性切片中的小海马轴突上进行直接膜片钳记录和电压成像，我们证明，即使在直径相差一个数量级的情况下，同一轴突内的AP形状仍保持一致。我们的结果表明，较小的轴突结构具有更多的Kv1钾通道，这些通道可在局部重新加速AP复极化，并有助于形成与大小无关的AP，同时它们并不排除AP形状的可塑性。因此，与大小无关的轴突AP可确保同一类型轴突内每个突触的数字信号保持一致。
