English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

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 mM to 16.2 mM. 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 mM Ca as was 2 mg/liter of verapamil in fibers exposed to 16.2 mM 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.

Effect of Verapamil on the Normal Action Potential and on a Calcium Dependent Slow Response of Canine Cardiac Purkinje Fibers