Figure 1.

FPL increases open probability, prolongs open duration, and prevents Ca²⁺ release-induced inactivation of Ca²⁺ channel. (A) Representative traces of unitary Ca²⁺ current recorded from a single channel patch at 0 mV, using 10 mM Ca²⁺ as the charge carrier in the presence of 10 μM FPL. (A Bottom) the ensemble averaged current of 925 sweeps. Notice the prolonged openings and reopenings during the pulse. (B) Open-time histogram of 1,907 opening events, bin width = 0.4 ms. The smooth line represents the best-fitted probability distribution function and τs denote the time constants. (C) Latency distribution of the first openings and reopenings of Ca²⁺ channel, bin width = 1 ms. Number of first openings is 637 and reopenings is 1,270. (D) Currents of the first opening (I_1st) and reopenings (I_R) of Ca²⁺ channels, reconstructed from idealized events. (A to D) Generated from the same patch. (E) Whole-cell I_Ca and Ca²⁺ transients in the presence of 3 μM FPL, before and during superfusion of 10 mM caffeine. (F) Inactivation of whole-cell I_Ca, quantified as I_{25 ms}/I_peak, before and during superfusion of 10 mM caffeine, in control and FPL-treated (n = 13) myocytes. ∗, Significant difference from control (P < 0.05).