Affiliation:
1. Rockefeller University, New York, New York 10021
Abstract
The effect of verapamil on normal sodium (Na)-dependent and slow calcium (Ca)-dependent action potentials recorded from canine cardiac Purkinje fibers was studied. The Ca-dependent slow response was obtained in fibers exposed to solutions in which all NaCl was replaced by tetraethylammonium chloride and in which Ca ranged from 4 m
M
to 16.2 m
M
. Verapamil (0.25-2 mg/liter) had little or no effect on the upstroke of the normal action potential, but such concentrations of verapamil suppressed rhythmic activity and depressed excitability in fibers that showed Ca-dependent slow responses. Spontaneous activity and rhythmic activity evoked by long depolarizing pulses were depressed. Verapamil decreased the amplitude and the upstroke velocity and shifted the threshold potential toward zero in fibers that showed Ca-dependent slow responses. The effectiveness of verapamil varied with the level of Ca; 0.25 mg/liter of verapamil was as effective in suppressing activity in fibers exposed to 4 m
M
Ca as was 2 mg/liter of verapamil in fibers exposed to 16.2 m
M
Ca. Although verapamil did not alter the upstroke of the normal Na-dependent action potential, it did depress the plateau and prolong the action potential of fibers exposed to normal Tyrode's solution.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Cardiology and Cardiovascular Medicine,Physiology
Cited by
246 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献