Figure 5. Low concentrations of 2-APB accelerate fast inactivation of I_CRAC.

A, peak I_CRAC (•) and the extent of inactivation (○) measured during steps to −100 mV. To monitor changes in the speed of inactivation, the extent of inactivation was measured as (I_peak–I_t)/I_peak, where I_peak is the peak current and I_t is the current measured 50 ms after each step to −100 mV. Addition of 5 μm 2-APB enhanced the peak current amplitude and increased the extent of inactivation. B, the time course of inactivation in the presence and absence of 2-APB. Traces on the left show the averages of five leak-corrected responses to hyperpolarizations given in A (bars in A) in 20 mm ${\text{Ca}}_0^{2+}$ with or without 5 μm 2-APB. The right plot shows the same traces normalized to their peak current. Note that the rate of current decay was enhanced in the presence of 2-APB. Holding potential =+30 mV.