Inhibition of T-Type and L-Type Ca2+ Currents by Aranidipine, a Novel Dihydropyridine Ca2+ Antagonist

Abstract
The effects of aranidipine, a novel dihydropyridine Ca2+ channel antagonist, on membrane currents in guinea pig ventricular myocytes and on action potentials in rabbit sinoatrial node tissue were examined. In myocytes, aranidipine (10 nmol/l to 1 μmol/l) concentration-dependently decreased T-type and L-type Ca2+ currents. Aranidipine (1 μmol/l) had little effect on K+ currents. In the sinoatrial node, 0.1 μmol/l aranidipine increased cycle length, and decreased +v̇max and the slope of the phase 4 depolarization. Thus, inhibition of both T-type and L-type Ca2+ currents by aranidipine may partly explain its potent negative chronotropic activity.

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