Inhibition of T-type and L-type Ca2+ currents by aranidipine, a novel dihydropyridine Ca2+ antagonist

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 mu mol/l) concentration-dependently decreased T-type and L-type Ca2+ currents. Aranidipine (1 mu mol/l) had little effect on K+ currents. In the sinoatrial node, 0.1 mu mol/l aranidipine increased cycle length, a nd decreased +(V) over dot (max) 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. Copyright (C) 2000 S. Karger AG, Basel.