Yang Lisha, Craviso Gale L, Vernier P Thomas, Chatterjee Indira, Leblanc Normand
Department of Pharmacology, University of Nevada, Reno School of Medicine, Reno, NV, United States of America.
Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA, United States of America.
PLoS One. 2017 Jul 10;12(7):e0181002. doi: 10.1371/journal.pone.0181002. eCollection 2017.
This study examined the effect of 5 ns electric pulses on macroscopic ionic currents in whole-cell voltage-clamped adrenal chromaffin cells. Current-voltage (I-V) relationships first established that the early peak inward current was primarily composed of a fast voltage-dependent Na+ current (INa), whereas the late outward current was composed of at least three ionic currents: a voltage-gated Ca2+ current (ICa), a Ca2+-activated K+ current (IK(Ca)), and a sustained voltage-dependent delayed rectifier K+ current (IKV). A constant-voltage step protocol was next used to monitor peak inward and late outward currents before and after cell exposure to a 5 ns pulse. A single pulse applied at an electric (E)-field amplitude of 5 MV/m resulted in an instantaneous decrease of ~4% in peak INa that then declined exponentially to a level that was ~85% of the initial level after 10 min. Increasing the E-field amplitude to 8 or 10 MV/m caused a twofold greater inhibitory effect on peak INa. The decrease in INa was not due to a change in either the steady-state inactivation or activation of the Na+ channel but instead was associated with a decrease in maximal Na+ conductance. Late outward current was not affected by a pulse applied at 5 MV/m. However, for a pulse applied at the higher E-field amplitudes of 8 and 10 MV/m, late outward current in some cells underwent a progressive ~22% decline over the course of the first 20 s following pulse exposure, with no further decline. The effect was most likely concentrated on ICa and IK(Ca) as IKV was not affected. The results of this study indicate that in whole-cell patch clamped adrenal chromaffin cells, a 5 ns pulse differentially inhibits specific voltage-gated ionic currents in a manner that can be manipulated by tuning E-field amplitude.
本研究检测了5纳秒电脉冲对全细胞电压钳制的肾上腺嗜铬细胞中宏观离子电流的影响。电流-电压（I-V）关系首先表明，早期内向电流峰值主要由快速电压依赖性Na⁺电流（INa）组成，而晚期外向电流至少由三种离子电流组成：电压门控Ca²⁺电流（ICa）、Ca²⁺激活的K⁺电流（IK(Ca)）和持续电压依赖性延迟整流K⁺电流（IKV）。接下来，采用恒压阶跃方案监测细胞暴露于5纳秒脉冲前后的内向电流峰值和晚期外向电流。在电场（E）幅度为5 MV/m时施加单个脉冲，导致INa峰值瞬间下降约4%，随后呈指数下降，10分钟后降至初始水平的约85%。将电场幅度增加到8或10 MV/m对INa峰值产生两倍大的抑制作用。INa的降低不是由于Na⁺通道稳态失活或激活的变化，而是与最大Na⁺电导的降低有关。5 MV/m的脉冲对晚期外向电流没有影响。然而，对于在8和10 MV/m的较高电场幅度下施加的脉冲，一些细胞中的晚期外向电流在脉冲暴露后的前20秒内逐渐下降约22%，之后不再下降。这种效应最可能集中在ICa和IK(Ca)上，因为IKV不受影响。本研究结果表明，在全细胞膜片钳制的肾上腺嗜铬细胞中，5纳秒脉冲以一种可通过调节电场幅度来控制的方式差异性地抑制特定的电压门控离子电流。
