Figure 4. E–C coupling gain increased with SR Ca²⁺ load at constant trigger strength.

A, Caffeine-induced [Ca²⁺]_i transients showing high and low SR loads. Below are responses at the two loads to two trigger strengths, set with either minimal (B; V_h=−55 mV) or substantial (C; V_h=−41 mV)I_Ca pre-inactivation. Rabbit cell, control only. This cell subsequently responded robustly to ISO (not shown).