Nakanishi H, Matsuoka I, Ono T, Yoshida H, Uchibori T, Kogi K
Department of Pharmacology, Fukushima Medical College, Japan.
Fukushima J Med Sci. 1996 Dec;42(1-2):1-10.
Effects of verapamil, prenylamine and a prenylamine analog, MG8926 on the intracellular spontaneous action potentials recorded from the isolated rabbit sinoatrial (SA) node were studied. Verapamil (1 microM), a selective inhibitor for slow Ca2+ channels, prolonged the cycle length, decreased the rate of diastolic depolarization, the rate of rise of action potential, the amplitude of action potential and the maximal diastolic potential, and usually arrested showing subthreshold fluctuation of the membrane potential within several ten min. Prenylamine (10 microM), a nonselective inhibitor for slow Ca2+ channels, tended to prolong the cycle length to decrease the diastolic depolarization, the rate of rise of action potential, the amplitude of action potential. However, these changes were statistically insignificant. Prenylamine at the concentration of 10 microM had no effect on the maximal diastolic potential. MG8926 (10 microM) prolonged the cycle length, decreased the rate of diastolic depolarization, the rate of rise of action potential and tended to decrease the amplitude of action potential. MG8926 at the concentration of 10 microM had almost no effect on the maximal diastolic potential. The present findings may indicate that replacement of phenyl residue of prenylamine by cyclohexyl residue increases the inhibitory action on the slow Ca2+ channels in rabbit SA node.
研究了维拉帕米、普尼拉明及其类似物MG8926对从离体兔窦房结记录的细胞内自发动作电位的影响。维拉帕米（1微摩尔），一种慢钙通道的选择性抑制剂，延长了心动周期长度，降低了舒张期去极化速率、动作电位上升速率、动作电位幅度和最大舒张电位，并且通常在几十分钟内使膜电位出现阈下波动并停止。普尼拉明（10微摩尔），一种慢钙通道的非选择性抑制剂，倾向于延长心动周期长度，降低舒张期去极化、动作电位上升速率和动作电位幅度。然而，这些变化在统计学上不显著。10微摩尔浓度的普尼拉明对最大舒张电位无影响。MG8926（10微摩尔）延长了心动周期长度，降低了舒张期去极化速率、动作电位上升速率，并倾向于降低动作电位幅度。10微摩尔浓度的MG8926对最大舒张电位几乎无影响。目前的研究结果可能表明，用环己基取代普尼拉明的苯基可增强对兔窦房结慢钙通道的抑制作用。
