Zheng P, Shi N C, Gong Q Y, Yang Z C
Department of Pharmacology, School of Basic Medical Sciences, Shanghai Medical University, China.
Zhongguo Yao Li Xue Bao. 1996 May;17(3):241-4.
To determine whether felodipine (Fel) has Ca2+ channel blocking effect in mammalian myocardium in comparison with those of nifedipine (Nif) and verapamil (Ver).
The action potentials (AP), the slow AP and the inward slow Ca2+ currents of guinea pig papillary muscles were studied using intracellular microelectrodes and voltage-clamp techniques.
Fel 1, 3, and 10 mumol.L-1 concentration-dependently shortened APD30, APD50, and APD90 of the AP, while Vmax and APA were not affected. The effect of Fel was not reversible on washout. At 0.1, 1, 3, and 10 mumol.L-1, Fel depressed Vmax, APA, APD30, APD50, and APD90 of the slow AP in a dose-dependent manner. The inward slow Ca2+ currents were reduced by Fel 3 mumol.L-1. APD30, APD50, and APD90 of the first AP after rest were still shortened by Fel. When the stimulation frequency was elevated, the effect of Fel on the AP and slow AP decreased. The effect of Fel 3 mumol.L-1 on the slow AP was abolished in preparation pretreated with trifluoperazine. The threshold concentrations of Nif and Ver for the inhibition of APD50 of the slow AP (P < 0.05) were 0.1 and 1 mumol.L-1, respectively. The effect of Ver 3 mumol.L-1 on the fast AP was not reversible on washout, but that of Nif 3 mumol.L-1 was. When the stimulation frequency was elevated from 0.5 to 2 Hz, the effect of Nif 3 mumol.L-1 on the fast AP was reduced, but that of Ver 3 mumol.L-1 was increased.
Fel inhibited mainly the resting state of the cardiac Ca2+ channel. The potency of Fel was about the same as that of Nif and about 10 times more potent than that of Ver.
比较非洛地平（Fel）与硝苯地平（Nif）和维拉帕米（Ver）相比，在哺乳动物心肌中是否具有钙通道阻滞作用。
采用细胞内微电极和电压钳技术研究豚鼠乳头肌的动作电位（AP）、慢动作电位和内向慢钙电流。
1、3和10μmol·L-1浓度的Fel呈浓度依赖性缩短动作电位的APD30、APD50和APD90，而Vmax和APA不受影响。Fel的作用在洗脱后不可逆。在0.1、1、3和10μmol·L-1时，Fel呈剂量依赖性降低慢动作电位的Vmax、APA、APD30、APD50和APD90。3μmol·L-1的Fel可降低内向慢钙电流。休息后的第一个动作电位的APD30、APD50和APD90仍被Fel缩短。当刺激频率升高时，Fel对动作电位和慢动作电位的作用减弱。用三氟拉嗪预处理的标本中，3μmol·L-1的Fel对慢动作电位的作用被消除。抑制慢动作电位APD50的Nif和Ver的阈值浓度（P<0.05）分别为0.1和1μmol·L-1。3μmol·L-1的Ver对快动作电位的作用在洗脱后不可逆，而3μmol·L-1的Nif的作用可逆。当刺激频率从0.5Hz升高到2Hz时，3μmol·L-1的Nif对快动作电位的作用减弱，而3μmol·L-1的Ver的作用增强。
Fel主要抑制心脏钙通道的静息状态。Fel的效力与Nif大致相同，比Ver强约10倍。
