FIGURE 11.

The slow modal transitions in scGIRK and K_ACh channel gating are associated with changes in the equilibrium among the four functional modes of these channels. (A) Open probability histograms generated from the initial (left panel) and late (right panel) phases of scGIRK activity shown in Fig. 9. The mean p_o values and the relative areas of different gamma components (shown in parentheses) are p_o1 = 0.00037 (65.5%), p_o2 = 0.0015 (28.7%), and p_o3 = 0.0032 (5.8%) for the initial phase; and p_o1 = 0.00072 (58.7%), p_o2 = 0.0026 (32.8%), and p_o3 = 0.0045 (8.5%) for the late phase of channel activation. The P values computed from these histograms are P^initial = 0.225, and P^late = 0.270. In this experiment, the changes in the kinetic behavior of the scGIRK were associated with both a slight shift in modal equilibrium and a significant increase in the open probability of different functional modes. (B) Open probability histograms generated from the initial (left panel) and late (right panel) phases of K_ACh channel activity shown in Fig. 9. The mean p_o values and the relative areas of different components are p_o1 = 0.0033 (50.0%), p_o2 = 0.012 (37.5%), and p_o3 = 0.031 (12.5%) for the initial phase; and p_o1 = 0.0033 (20.3%), p_o2 = 0.015 (37.4%), and p_o3 = 0.053 (42.3%) for the late phase of channel activation. The P values computed from these histograms are P^initial = 0.328 and P^late = 0.555 for the K_ACh channel. Thus, the changes in the gating behavior for this K_ACh channel were mostly associated with a shift in the modal equilibrium toward gating modes 3 and 4.