The dependency test of SERCA and RyR in the genesis of SDs. (a) Time-course of the membrane potential, [Ca2+]up, [Ca2+]rel, and Irel for modulated SERCA and RyR, removed modulation of [Ca2+]i on SERCA, removed modulation of [Ca2+]up on SERCA, and removed modulation of [Ca2+]d on RyR. (b) Time-course of the membrane potential, [Ca2+]up, [Ca2+]rel, and Irel for removed modulation of [Ca2+]i on RyR. The black triangle indicates the time when a stimulus was applied. SERCA, sarcoplasmic reticulum Ca2+-ATPase; SD, spontaneous depolarization; RyR, ryanodine receptors. (Online version in colour.)