Frank G B, Konya L, Sudha T S
Department of Pharmacology, University of Alberta, Edmonton, Canada.
Can J Physiol Pharmacol. 1988 Sep;66(9):1210-3. doi: 10.1139/y88-199.
The effects of the organic calcium channel blocker nitrendipine was tested on electrically evoked twitches and on potassium depolarization-induced contractures of rat lumbricalis muscles. Nitrendipine (10(-7) to 5 X 10(-5) M) blocked only the potassium contractures. It was concluded that blocking calcium uptake through the slow voltage-sensitive calcium channels during potassium depolarization blocks the mechanical response of the muscle. Thus extracellular calcium ions are required for the excitation-contraction (E-C) coupling during depolarization contractures. On the other hand, electrically evoked twitches were not affected by nitrendipine; therefore, extracellular calcium ions entering via the slow voltage-sensitive channels are not required for E-C coupling during the twitch.
研究了有机钙通道阻滞剂尼群地平对大鼠蚓状肌电诱发抽搐和钾去极化诱导挛缩的影响。尼群地平（10^(-7)至5×10^(-5)M）仅阻断钾诱导的挛缩。得出的结论是，在钾去极化过程中，通过缓慢电压敏感性钙通道阻断钙摄取可阻断肌肉的机械反应。因此，去极化挛缩期间的兴奋-收缩（E-C）偶联需要细胞外钙离子。另一方面，电诱发的抽搐不受尼群地平影响；因此，抽搐期间的E-C偶联不需要通过缓慢电压敏感性通道进入的细胞外钙离子。
