Osterrieder W
J Cardiovasc Pharmacol. 1986 Nov-Dec;8(6):1101-6.
The inhibitory effect of the phenylalkylamine-type Ca2+-entry blocker, tiapamil, on the fast Na+ inward current was investigated in guinea-pig papillary muscles by measuring the maximum upstroke velocity (dV/dt)max of transmembrane action potentials. Tiapamil inhibited (dV/dt)max at concentrations above 10(-6) M, with an IC50 value of 7 X 10(-5) M (1 Hz stimulation frequency, 5.9 mM extracellular K+). Verapamil was less potent in depressing upstroke velocity. Inhibition of the dV/dtmax strongly depended on the frequency at which the muscles were stimulated ("use-dependent" effect). There was no evidence that tiapamil acts in a potential-dependent manner like local anesthetics. The results indicate that the Ca2+-entry blocker tiapamil has additional pharmacological properties, which may contribute to its usefulness in the treatment of ventricular arrhythmias.
通过测量豚鼠乳头肌跨膜动作电位的最大上升速度（dV/dt）max，研究了苯烷基胺类Ca2+内流阻滞剂替帕米对快速Na+内向电流的抑制作用。替帕米在浓度高于10（-6）M时抑制（dV/dt）max，IC50值为7×10（-5）M（刺激频率1Hz，细胞外K+浓度5.9mM）。维拉帕米降低上升速度的作用较弱。dV/dtmax的抑制强烈依赖于肌肉的刺激频率（“频率依赖性”效应）。没有证据表明替帕米像局部麻醉药那样以电位依赖性方式起作用。结果表明，Ca2+内流阻滞剂替帕米具有其他药理特性，这可能有助于其在治疗室性心律失常方面的应用。
