Fig. 1.

Flecainide inhibition of RyR2 open probability under various experimental conditions. Representative single-channel recordings of sheep RyR2 at +40 mV showing inhibition by flecainide in the cytoplasmic (A) and luminal (B) bath ([flecainide] at the end of each trace). The cytoplasmic bath contained 2 mM ATP; free Ca²⁺ = 0.1 mM and free Mg²⁺ = 1 mM. The luminal bath contained 0.1 mM Ca²⁺. Channel openings appear as upward current jumps from the baseline (top traces, the channel closed state indicated by dashed line). (C) [Flecainide] dependencies of RyR2 open probability (P_o) relative to that in the absence of flecainide (experimental conditions, legend, and n values given in Table 1). (D) The voltage dependence of IC₅₀ for cytoplasmic and luminal flecainide inhibition (symbols in Table 1).