Diltiazem, an antagonist of calcium channels, reduces norepinephrine in the rat myocardium

The present study examined the effect of diltiazem, a calcium channel antagonist, on potassium (K+) depolarization-induced norepinephrine (NE) release in rat myocardium using a flexibly mounted microdialysis technique. When high concentration of KCl (70 mM) was directly infused in rat heart through a microdialysis probe, the level of NE gradually increased in a time dependent manner. However, when a high concentration of KCl (70 mM) was administered to diltiazem-pretreated animals, it failed to increase the KCl-induced dialysate NE. These results suggest that calcium (Ca2+) may play a key role in K+ depolarization-induced NE release in the myocardium.