Cellular effects of nanosecond pulsed electric field exposures can be attenuated by an electric field reversal, a phenomenon called bipolar pulse cancellation. Our investigations of this phenomenon in neuroendocrine adrenal chromaffin cells show that a single 2 ns, 16 MV/m unipolar pulse elicited a rapid, transient rise in intracellular Ca2+ levels due to Ca2+ influx through voltage-gated calcium channels. The response was eliminated by a 2 ns bipolar pulse with positive and negative phases of equal duration and amplitude, and fully restored (unipolar-equivalent response) when the delay between each phase of the bipolar pulse was 30 ns. Longer interphase intervals evoked Ca2+ responses that were greater in magnitude than those evoked by a unipolar pulse (stimulation). Cancellation was also observed when the amplitude of the second (negative) phase of the bipolar pulse was half that of the first (positive) phase but progressively lost as the amplitude of the second phase was incrementally increased above that of the first phase. When the amplitude of the second phase was twice that of the first phase, there was stimulation. By comparing the experimental results for each manipulation of the bipolar pulse waveform with analytical calculations of capacitive membrane charging/discharging, also known as accelerated membrane discharge mechanism, we show that the transition from cancellation to unipolar-equivalent stimulation broadly agrees with this model. Taken as a whole, our results demonstrate that electrostimulation of adrenal chromaffin cells with ultrashort pulses can be modulated with interphase intervals of tens of nanoseconds, a prediction of the accelerated membrane discharge mechanism not previously observed in other bipolar pulse cancellation studies. Such modulation of Ca2+ responses in a neural-type cell is promising for the potential use of nanosecond bipolar pulse technologies for remote electrostimulation applications for neuromodulation.

中文翻译：

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2 ns 电刺激 Ca2+ 流入嗜铬细胞：通过场反转快速调制

纳秒脉冲电场暴露的细胞效应可以通过电场反转来减弱，这种现象称为双极脉冲消除。我们对神经内分泌肾上腺嗜铬细胞中这种现象的研究表明，由于 Ca2+ 通过电压门控钙通道流入，单个 2 ns、16 MV/m 的单极脉冲引起细胞内 Ca2+ 水平的快速、短暂上升。该响应被一个具有相等持续时间和幅度的正负相位的 2 ns 双极脉冲消除，并在双极脉冲的每个相位之间的延迟为 30 ns 时完全恢复（单极等效响应）。较长的相间间隔诱发的 Ca2+ 反应在幅度上大于单极脉冲（刺激）诱发的反应。当双极脉冲的第二（负）相位的幅度是第一（正）相位的一半但随着第二相位的幅度逐渐增加到高于第一相位的幅度时逐渐消失时，也观察到消除。当第二阶段的振幅是第一阶段的两倍时，有刺激。通过将双极脉冲波形的每次操作的实验结果与电容膜充电/放电（也称为加速膜放电机制）的分析计算进行比较，我们表明从取消到单极等效刺激的过渡与该模型大致一致。整体来看，我们的研究结果表明，用超短脉冲对肾上腺嗜铬细胞的电刺激可以以数十纳秒的相间间隔进行调节，这是对以前在其他双极脉冲消除研究中未观察到的加速膜放电机制的预测。这种在神经型细胞中对 Ca2+ 反应的调节有望将纳秒双极脉冲技术用于神经调节的远程电刺激应用。