Differential effects of verapamil and flunarizine on cardiac L-type and T-type Ca channels.

Whole cell experiments were used to study whether the L-type and the T-type Ca channel in guinea-pig ventricular myocytes are blocked similarly by verapamil and flunarizine. The L-type current is blocked by 5 mumol/l verapamil and 5 mumol/flunarizine in a use-dependent way, and block can be relieved by hyperpolarizing pulses in a potential-dependent way. The T-type current is not affected by 10 mumol/l verapamil while it is blocked by 10 mumol/l flunarizine in a use-dependent way. Verapamil selectively blocks the L-type channel in contrast to flunarizine.