Postjunctional I _Na contribution is enhanced for moderate gap junction coupling. (A–C) The fraction of Na⁺ charge Q_Na carried by (A) postjunctional, (B) lateral, and (C) prejunctional I_Na is shown as a function of gap junction conductance g_gap for cleft widths of 10 (left), 20 (middle), and 30 (right) nm and different values of f_Na for the mix/homogeneous-polarized distribution.