Duan Ya-Qi, Tang Ming, Liang Hua-Min, Hescheler Jurgen
Department of Physiology, Tongji Medical College, Huazhong University of Science and Technology, Pulmonary Disease Laboratory of Ministry of Health of China, Wuhan 430030, China.
Sheng Li Xue Bao. 2006 Feb 25;58(1):65-70.
In our studies, we have applied a novel tool, microelectrode arrays (MEA), to investigate the electrophysiological properties of murine embryonic hearts in vitro. The electrical signals were recorded from the areas of the heart adhering to the 60 MEA electrodes, being called field potentials (FPs). As an extracelluar recording, the waveform of the FP appeared similar to a reversed action potential obtained from single cell by whole cell current clamp and the FP duration was comparable with the action potential duration. To study propagation of spontaneous electrical activity, we have compared the occurrence time of FPs recorded from different electrodes. It is shown that there was already an apparent A-V delay [(50.21+/-9.7) ms] at day 9.5 post coitum (E9.5) when heart was still tubular-like and atrium and ventricle were not separated anatomically, while occurence of FP at different electrodes of ventricular area were almost synchronous. Further, we looked into the modulation of spontaneous electrical activity during cardiac development: at E9.5 of embryonic development, 1 mumol/L of isoproterenol (Iso) increased beating frequency by (34.04+/-7.31)%, shortened the A-V delay by (20.00+/-6.44) % and prolonged FP duration. In contrast, 1 mumol/L of carbachol (CCh) slowed down beating frequency by (42.32+/-5.36) %, A-V conduction by (26.00+/-4.81) % and shortened FP duration; however at late stage (E16.5), the regulatory effect of Iso and CCh was strengthened. Therefore we conclude that cardiac conduction system is already established at E9.5 when the four-chambered heart is not formed yet and the regulation of spontaneous activity by sympathetic and para-sympathetic system is gradually matured during cardiac development.
在我们的研究中，我们应用了一种新型工具——微电极阵列（MEA），来体外研究小鼠胚胎心脏的电生理特性。电信号从附着在60个MEA电极上的心脏区域记录下来，称为场电位（FP）。作为一种细胞外记录，FP的波形看起来类似于通过全细胞电流钳从单细胞获得的反向动作电位，并且FP持续时间与动作电位持续时间相当。为了研究自发电活动的传播，我们比较了从不同电极记录的FP的发生时间。结果表明，在妊娠第9.5天（E9.5），当心脏仍呈管状且心房和心室在解剖学上未分离时，已经存在明显的房室延迟[（50.21±9.7）毫秒]，而心室区域不同电极处FP的发生几乎是同步的。此外，我们研究了心脏发育过程中自发电活动的调节：在胚胎发育的E9.5时，1μmol/L的异丙肾上腺素（Iso）使心跳频率增加了（34.04±7.31）%，使房室延迟缩短了（20.00±6.44）%，并延长了FP持续时间。相比之下，1μmol/L的卡巴胆碱（CCh）使心跳频率减慢了（42.32±5.36）%，房室传导减慢了（26.00±4.81）%，并缩短了FP持续时间；然而在后期（E16.5），Iso和CCh的调节作用增强。因此我们得出结论，在四腔心脏尚未形成的E9.5时心脏传导系统已经建立，并且交感和副交感系统对自发活动的调节在心脏发育过程中逐渐成熟。
