Effect of Cilnidipine on L- and T-type Calcium Currents in Guinea Pig Ventricle and Action Potential in Rabbit Sinoatrial Node

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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.