Comparison of the effects of bath Ca²⁺, A438079, and CBX on the rates of receptor deactivation. (A) Effects of A438079 application on the rate of deactivation of the wild-type P2X7R after washout of 100 µM BzATP with 2-mM Ca²⁺–containing (left) and Ca²⁺-deficient (right) medium. The gray trace (left) shows receptor deactivation in the absence of A438079. For clarity, the activation phase is not shown. (B) Changes in the rate of T15E-P2X7R deactivation by application of 100 µM A438079 in cells bathed in 2-mM Ca²⁺–containing (left) and Ca²⁺-deficient (right) medium. (C) Two examples of effects of 2 mM Ca²⁺ on the rate of T15E-P2X7R deactivation in the presence of A438079. Arrows indicate the time of Ca²⁺ application; black traces, 2 mM Ca²⁺; gray traces, Ca²⁺-deficient medium. In all experiments, bath medium contained 1 mM Mg²⁺, cells were stimulated with 100 µM BzATP, and the concentration of A438079 was 100 µM. (D) Effects of 10 mM Ca²⁺ on the amplitude of 100-µM BzATP–induced current in cells expressing the wild-type receptor and bathed in Ca²⁺-deficient medium with 32 µM CBX.