FIGURE 3.

Dependence of on ligand concentration can be explained by a change in the proportion of openings involving only three active subunits (A3-only openings) and those involving four active subunits (A4-related openings). (A) Stochastic simulation results demonstrating that the mean open times of A3-only and A4-related openings show only a slight dependence on [Ca²⁺] for [IP₃] = 10 μM. (B) The probabilities of A3-only and A4-related openings as functions of [Ca²⁺]. In both panels, [IP₃] = 10 μM.