Effects of calcium antagonists on smooth muscle membranes of the canine stomach.
In circular muscles of the canine stomach, diltiazem (greater than 3 X 10(-6)M) depolarized and nicardipine (greater than 10(-6)M) hyperpolarized the membrane. Diltiazem (greater than 5 X 10(-6)M) or nicardipine (greater than 3 X 10(-7M) inhibited the plateau potential of spontaneously generated or electrically evoked action potential. In Na-deficient solution (between 137 and 30 mM Na), diltiazem and nicardipine selectively inhibited the plateau potential. In Na- (15 mM Na) or Ca-deficient (0.25 mM Ca) solution, spontaneously generated action potential ceased, and only graded responses were evoked by electrical stimulation. These graded responses were inhibited by diltiazem (greater than 5 X 10(-6)M) or nicardipine (greater than 3 X 10(-7)M). The ionic contribution for generation of action potential in this muscle cell was discussed in relation to actions of Ca antagonists.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002794:Choline / Q000494:pharmacology; D004110:Diltiazem / Q000494:pharmacology; D004285:Dogs; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects*; D009529:Nicardipine; D009543:Nifedipine / Q000031:analogs & derivatives / Q000494:pharmacology; D013270:Stomach / Q000187:drug effects
D002121:Calcium Channel Blockers; D001285:Atropine; D009529:Nicardipine; D004110:Diltiazem; D009543:Nifedipine; D002794:Choline