Cilnidipine, a dihydropyridine Ca2+ channel antagonist, is known to have inhibitory effects on both L- and N-type Ca2+ currents. In the present study, we examined the effect of cilnidipine on myocardial L- and T-type Ca2+ currents and sinoatrial node action potential configuration. In voltage clamped guinea pig ventricular myocytes, cilnidipine concentration-dependently decreased L- and T-type Ca2+ currents. In rabbit sinoatrial node tissue, cilnidipine increased cycle length through reduction of phase 4 depolarization slope. In conclusion, cilnidipine has inhibitory effects on T-type Ca2+ current, which may contribute to its negative chronotropic potency.
The Japanese Pharmacological Society 2004