Nitrendipine blocks high potassium contractures but not twitches in rat skeletal muscle |
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Authors: | G B Frank L Konya T S Sudha |
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Institution: | Department of Pharmacology, University of Alberta, Edmonton, Canada. |
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Abstract: | 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. |
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