Fig. 2. The effects of TEA and ryanodine on periodic outward currents. (A) Depolarisation to -20 mV (v) from a membrane potential (V_M) of -69 mV activated periodic outward currents (ii) that increased in frequency and amplitude (mean amplitude 116±30 pA) even as [Ca²⁺]i (iv) declined. The current amplitude varied widely (i,iii). (B) TEA (20 mM, which blocks K⁺ channels) inhibited periodic outward currents (i) evoked by depolarisation to -30 mV (iii). (C) Ryanodine (50 µM), which places RyR in a subconductance state, inhibited periodic currents (i) evoked by depolarisation to 0 mV (iii) but failed to increase [Ca²⁺]i significantly. The small increase in [Ca²⁺]i (ii) represent a partial inhibition of conductance at the RyR. Together A, B and C indicate that the periodic outward currents are indeed STOCs.