PMID: 7087252Feb 1, 1982Paper

Potentiation of indirectly induced muscle twitches by organic calcium antagonists in phrenic nerve-diaphragm muscle preparations of mice

Japanese Journal of Pharmacology
F AsaiN Urakawa


Organic calcium antagonists (l- and d-verapamil, D600, and diltiazem) were examined for their effects on muscle twitches of isolated phrenic nerve-diaphragm muscle preparations of mice. The calcium antagonists (1 x 10(-6) to 7.5 x 10(-5) M) increased the amplitude of muscle twitches induced by nerve stimuli with short durations (0.04 to 0.4 msec) of rectangular pulses. However, these agents were poorly effective on twitches induced by nerve stimuli with longer durations over 0.6 msec or by direct shocks. The potentiative effect was reversible, reproducible and dependent on their concentrations. Diltiazem was the most effective among the four agents tested. The twitch increase produced by all of the agents was demonstrated at concentrations of external Ca++ above 0.6 mM. At Ca++ concentrations below 0.5 mM, the tension of the indirectly induced muscle twitch was partially inhibited in the presence of these agents. Caffeine, theophylline, isoproterenol or hypertonic potassium ions increased the tension of indirectly induced muscle twitches. The potentiative effect of the organic calcium antagonists, however, was discriminated from those induced by the other agents under some conditions. From these results, it is suggested that th...Continue Reading


Jun 1, 1984·European Journal of Pharmacology·H KarakiN Urakawa

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