Wang Hong-wei, Yang Zhi-fang, Zhang Yin, Yang Jian-min, Liu Yuan-mou, Li Ci-zhen
Department of Physiology, Shanghai Jiaotong University School of Medicine, Shanghai 200025, China.
Acta Pharmacol Sin. 2009 Aug;30(8):1115-22. doi: 10.1038/aps.2009.96. Epub 2009 Jul 20.
To study the influence of beta-receptor activation on sodium channel current and the physiological significance of increased sodium current with regard to the increased cardiac output caused by sympathetic excitation.
Multiple experimental approaches, including ECG, action potential recording with conventional microelectrodes, whole-cell current measurements, single-channel recordings, and pumping-force measurements, were applied to guinea pig hearts and isolated ventricular myocytes.
Isoprenaline was found to dose-dependently shorten QRS waves, increase the amplitude and the V(max) of action potentials, augment the fast sodium current, and increase the occurrence frequencies and open time constants of the long-open and burst modes of the sodium channel. Increased levels of membrane-permeable cAMP have similar effects. In the presence of a calcium channel blocker, TTX reversed the increased pumping force produced by isoprenaline.
Beta-adrenergic modulation increases the inward sodium current and accelerates the conduction velocity within the ventricles by changing the sodium channel modes, which might both be conducive to the synchronous contraction of the heart and enhance its pumping function.
研究β受体激活对钠通道电流的影响，以及钠电流增加在交感神经兴奋引起的心输出量增加方面的生理意义。
将包括心电图、用传统微电极记录动作电位、全细胞电流测量、单通道记录和泵力测量在内的多种实验方法应用于豚鼠心脏和分离的心室肌细胞。
发现异丙肾上腺素可剂量依赖性地缩短QRS波，增加动作电位的幅度和V(max)，增强快速钠电流，并增加钠通道长开放模式和爆发模式的发生频率及开放时间常数。膜通透性cAMP水平升高具有类似作用。在存在钙通道阻滞剂的情况下，TTX可逆转异丙肾上腺素产生的泵力增加。
β肾上腺素能调节通过改变钠通道模式增加内向钠电流并加速心室内的传导速度，这两者可能都有利于心脏的同步收缩并增强其泵血功能。
