Effects of nicardipine on frog skeletal muscle in normal and calcium-free media.
The effects of the new "Ca-antagonist," nicardipine, on frog skeletal muscle were studied. Nicardipine (3 X 10(-10)-3 X 10(-7) M) had no effect on the twitch tension yet a high concentration (3 X 10(-6) M) had a slight potentiating effect, with no effect on the action potential. Nicardipine suppressed the repetitive action potentials induced by perfusion of Ca-free solution and thereby suppressed augmentation of the tension responses, in a dose dependent manner. A high concentration of nicardipine (3 X 10(-6) M) abolished the twitch tension due to abolition of the action potential, in Ca-free solution. These abolitions of the action potential and twitches induced by nicardipine in Ca-free solution were antagonized in the case of NaCl hypertonic solution. Therefore, nicardipine probably inhibits Na permeability in frog skeletal muscle placed in Ca-free solution.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers; D009119:Muscle Contraction / Q000187:drug effects; D009132:Muscles / Q000502:physiology*; D009529:Nicardipine; D009543:Nifedipine / Q000031:analogs & derivatives* / Q000494:pharmacology; D011892:Rana catesbeiana; D011898:Ranidae; D012462:Saline Solution, Hypertonic; D013779:Tetrodotoxin / Q000494:pharmacology
D002121:Calcium Channel Blockers; D012462:Saline Solution, Hypertonic; D013779:Tetrodotoxin; D009529:Nicardipine; D009543:Nifedipine; D002118:Calcium