Tovar Kenneth R, Bridges Daniel C, Wu Bian, Randall Connor, Audouard Morgane, Jang Jiwon, Hansma Paul K, Kosik Kenneth S
Neuroscience Research Institute, University of California , Santa Barbara, California.
Department of Physics, University of California , Santa Barbara, California.
J Neurophysiol. 2018 Jul 1;120(1):306-320. doi: 10.1152/jn.00659.2017. Epub 2018 Apr 11.
We report the presence of co-occurring extracellular action potentials (eAPs) from cultured mouse hippocampal neurons among groups of planar electrodes on multielectrode arrays (MEAs). The invariant sequences of eAPs among coactive electrode groups, repeated co-occurrences, and short interelectrode latencies are consistent with action potential propagation in unmyelinated axons. Repeated eAP codetection by multiple electrodes was widespread in all our data records. Codetection of eAPs confirms they result from the same neuron and allows these eAPs to be isolated from all other spikes independently of spike sorting algorithms. We averaged co-occurring events and revealed additional electrodes with eAPs that would otherwise be below detection threshold. We used these eAP cohorts to explore the temperature sensitivity of action potential propagation and the relationship between voltage-gated sodium channel density and propagation velocity. The sequence of eAPs among coactive electrodes "fingerprints" neurons giving rise to these events and identifies them within neuronal ensembles. We used this property and the noninvasive nature of extracellular recording to monitor changes in excitability at multiple points in single axonal arbors simultaneously over several hours, demonstrating independence of axonal segments. Over several weeks, we recorded changes in interelectrode propagation latencies and ongoing changes in excitability in different regions of single axonal arbors. Our work illustrates how repeated eAP co-occurrences can be used to extract physiological data from single axons with low-density MEAs. However, repeated eAP co-occurrences lead to oversampling spikes from single neurons and thus can confound traditional spike-train analysis. NEW & NOTEWORTHY We studied action potential propagation in single axons using low-density multielectrode arrays. We unambiguously identified the neuronal sources of propagating action potentials and recorded extracellular action potentials from several positions within single axonal arbors. We found a surprisingly high density of axonal voltage-gated sodium channels responsible for a high propagation safety factor. Our experiments also demonstrate that excitability in different segments of single axons is regulated independently on timescales from hours to weeks.
我们报告了在多电极阵列（MEA）上的平面电极组中，培养的小鼠海马神经元存在同时出现的细胞外动作电位（eAPs）。共同激活电极组之间eAPs的不变序列、反复共同出现以及较短的电极间潜伏期与无髓鞘轴突中的动作电位传播一致。多个电极对eAPs的反复共同检测在我们所有的数据记录中都很普遍。eAPs的共同检测证实它们来自同一个神经元，并允许将这些eAPs与所有其他尖峰独立分离，而无需依赖尖峰分类算法。我们对同时出现的事件进行平均，发现了原本低于检测阈值但带有eAPs的额外电极。我们利用这些eAP队列来探索动作电位传播的温度敏感性以及电压门控钠通道密度与传播速度之间的关系。共同激活电极之间的eAPs序列为引发这些事件的神经元“指纹识别”，并在神经元集合中识别它们。我们利用这一特性以及细胞外记录的非侵入性，在数小时内同时监测单个轴突分支多个点的兴奋性变化，证明了轴突段的独立性。在数周时间里，我们记录了电极间传播潜伏期的变化以及单个轴突分支不同区域兴奋性的持续变化。我们的工作说明了如何利用eAPs的反复共同出现，从低密度MEA的单个轴突中提取生理数据。然而，eAPs的反复共同出现会导致对单个神经元尖峰的过采样，从而可能混淆传统的尖峰序列分析。新内容及值得注意之处 我们使用低密度多电极阵列研究了单个轴突中的动作电位传播。我们明确识别了传播动作电位的神经元来源，并从单个轴突分支内的多个位置记录了细胞外动作电位。我们发现负责高传播安全系数的轴突电压门控钠通道密度惊人地高。我们的实验还表明，单个轴突不同节段的兴奋性在数小时到数周的时间尺度上是独立调节的。
