The speed of I_to inactivation fitted by a double exponential function. (A and B) Summary of the fast time constant (τ_fast, A) and the slow time constant (τ_slow, B) according to the clamp voltage. (C and D) The I_Ca,L inactivation was also fitted by a double exponential function; neither the fast inactivating time constant (τ_fast, C) nor the slow inactivating time component (τ_slow, D) was different.