Twenty Years of Calcium Imaging: Cell Physiology to Dye For

Sensitivity of RyR2s and Ca²⁺triggering. A. Transient elevations of [Ca²⁺]_i are better able to activate RyR2s than steady-state changes. Here, the RyR2 open probability (P_o) increases more following a step increase in [Ca²⁺]_i than it does in the steady state for the same final [Ca²⁺]_i. B. PKA enhances the relative increase in P_o due to a step increase of [Ca²⁺]_i but decreases the steady-state P_o.