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研究尼群地平（ｎｉｔｒｅｎｄｉｐｉｎｅ，Ｎｉｔ）、非洛地平（ｆｅｌｏｄｉｐｉｎｅ，Ｆｅｌ）对豚鼠乳头肌的电生理作用。用细胞内微电极技术测定药物的作用。结果：低浓度的Ｎｉｔ１和１０ｎｍｏｌ·Ｌ－１，延长快反应动作电位的二相坪台期（ＡＰＤ）中的ＡＰＤ２０、ＡＰＤ５０、ＡＰＤ９５和有效不应期（ＥＲＰ），其作用可被冲洗掉。高浓度的Ｎｉｔ０．３和１μｍｏｌ·Ｌ－１可浓度依赖性缩短异丙肾上腺素诱发的慢反应动作电位的时程ＡＰＤ５０和ＡＰＤ９０。其作用可被冲洗掉，但Ｎｉｔ的浓度增加到５和１０μｍｏｌ·Ｌ－１时，Ｎｉｔ对慢反应动作电位时程的作用，就不能冲洗掉。Ｆｅｌ也有相似作用。Ｎｉｔ和Ｆｅｌ对动作电位时程具有高浓度缩短，低浓度延长的的双相作用。硝苯啶（ｎｉｆｅｄｉｐｉｎｅ，Ｎｉｆ）１ｎｍｏｌ·Ｌ－１可明显延长动作电位时程，但维拉帕米（ｖｅｒａｐａｍｉｌ．Ｖｅｒ）０．１，１和５ｎｍｏｌ·Ｌ－１对动作电位无明显作用。结论：Ｎｉｔ，Ｆｅｌ在远低于阻断心肌钙通道的浓度时对心肌钙通道具有激动作用，但不是所有钙拮抗剂都具有类似作用。
To study the electrophysiological effects of nitrendipine (Nit) and felodipine (Fel) on papillary muscles in guinea pigs. Use of intracellular microelectrode techniques to determine the effect of drugs. Results: Low concentrations of Nit1 and 10 nmol·L-1 prolonged APD20, APD50, APD95 and effective refractory period (ERP) in the biphasic plateau phase (APD) of fast response action potentials, and their effects could be washed away. High concentrations of Nit0.3 and 1μmol·L-1 concentration-dependently shorten the isoproterenol-induced slow-response action potential duration APD50 and APD90. Its role can be washed away, but when the concentration of Nit is increased to 5 and 10μmol·L-1, the effect of Nit on the slow response action potential duration can not be washed away. Fel also has a similar effect. Nit and Fel have a biphasic effect of shortening the action potentials and prolonging the concentration of the action potentials. Nifedipine (Nif) 1nmol·L-1 could prolong the action potential duration significantly, but 0.1, 1 and 5nmol·L-1 of verapamil.Ver had no significant effect on action potential. CONCLUSIONS: Nit, Fel have an agonistic effect on myocardial calcium channels at well below the levels that block the calcium channels in the myocardium, but not all calcium antagonists have similar effects.