Figure 4. pH_i-dependent modulation of junctional conductance.

A, dynamics of I_j and g_j measured by applying repeated V_j ramps of ±20 mV (enlarged I_j responses to V_j ramps are shown in the inset) in response to applications of NH₄Cl (10 mm). B, g_j and pH_i measurements in one cell pair after application of 1, 3, 7 and 15 mm of NH₄Cl. C, summarized g_j–pH_i relationship in which the continuous line is a fitting curve to the Hill equation; pK_a= 7.41 ± 0.02 and the Hill coefficient of 5.9 ± 0.5 (n= 6). Filled circles are from the experiment shown in B.