持续的内向电流对运动神经元的兴奋性和放电行为很重要,并且与兴奋性毒性有关。特别是,L型Ca2+通道,通常位于运动神经元树突上,在突触输入的放大中起主要作用。然而,最近关于L型Ca2+通道行为的实验发现挑战了一些用于解释实验和计算建模数据的基本假设。因此,这项研究的目的是将最新的实验数据纳入最新的,高保真计算模型,以解释明显的不一致性和更好地阐明空间分布,表达模式,以及L型Ca2+和SKL通道的功能作用。具体来说,更新后的模型结合了非对称通道激活/去激活动力学,去极化依赖性促进,通道门控的随机性,和SKL通道的共激活。我们的模拟结果表明,L型Ca2和SKL通道以点状表达主要集中在运动神经元的远端树突上。此外,点状表达,与同质表达相反,提供高突触电流放大,限制双稳态和点火速率,并强健地调节Ca2+持续的内向电流,从而降低兴奋毒性的风险。在电流-电压和频率-电流关系中实验观察到的滞后和双稳态是由L型Ca2通道的远端位置和固有预热引起的。因此,我们的结果表明,L型Ca2+和SKL通道的点状表达是调节兴奋性的有效机制,这将提供强大的神经保护作用。我们的结果可以为离子通道的预热和点状表达对细胞兴奋性调节的功能意义提供更广泛的见解。关于L型Ca2通道的最新实验发现挑战了用于解释实验和计算建模数据的基本假设。这里,我们将最近的实验数据整合到更新的数据中,高保真计算模型来解释明显的不一致性并更好地阐明分布,表达模式,以及L型Ca2+和SKL通道的功能作用。我们的结果表明,L型Ca2+和SKL通道的点状表达是调节运动神经元兴奋性的有效机制,提供强大的神经保护作用。
Persistent inward currents are important to motoneuron excitability and firing behaviors and also have been implicated in excitotoxicity. In particular, L-type Ca2+ channels, usually located on motoneuron dendrites, play a primary role in amplification of synaptic inputs. However, recent experimental findings on L-type Ca2+ channel behaviors challenge some fundamental assumptions that have been used in interpreting experimental and computational modeling data. Thus, the objectives of this study were to incorporate recent experimental data into an updated, high-fidelity computational model in order to explain apparent inconsistencies and to better elucidate the spatial distributions, expression patterns, and functional roles of L-type Ca2+ and SKL channels. Specifically, the updated model incorporated asymmetric channel activation/deactivation kinetics, depolarization-dependent facilitation, randomness in channel gating, and coactivation of SKL channels. Our simulation results suggest that L-type Ca2+ and SKL channels colocalize primarily on distal dendrites of motoneurons in a punctate expression. Also, punctate expression, as opposed to a homogeneous expression, provides high synaptic current amplification, limits bistability and firing rates, and robustly regulates the Ca2+ persistent inward current, thereby reducing risk of excitotoxicity. The hysteresis and bistability observed experimentally in current-voltage and frequency-current relationships result from the L-type Ca2+ channels\' distal location and intrinsic warm-up. Accordingly, our results indicate that punctate expression of L-type Ca2+ and SKL channels is a potent mechanism for regulating excitability, which would provide a strong neuroprotective effect. Our results could provide broader insights into the functional significance of warm-up and punctate expression of ion channels to regulation of cell excitability.NEW & NOTEWORTHY Recent experimental findings on L-type Ca2+ channels challenge fundamental assumptions used in interpreting experimental and computational modeling data. Here, we incorporated recent experimental data into an updated, high-fidelity computational model to explain apparent inconsistencies and better elucidate the distributions, expression patterns, and functional roles of L-type Ca2+ and SKL channels. Our results indicate that punctate expression of L-type Ca2+ and SKL channels is a potent mechanism for regulating motoneuron excitability, providing a strong neuroprotective effect.