Single-channel properties of Cx40 mutant gap junctions. (A) Sister single-channel currents (I₁ and I₂) recorded from a N2A Cx40A96S cell pair during maintained V_j of 50 mV. Solid line, zero current level. The all-points current histogram (right-hand side) revealed a conductance of 139 pS. (B) Bipolar pulse protocol (V₁ and V₂) and associated single-channel current recording from a N2A Cx40M163V cell pair. The all-points current histogram yielded conductances of 140 and 144 pS for negative and positive V_j, respectively. (C) Voltage-pulse protocol (V₁ and V₂) and associated single-channel current (I_j) recorded from a N2ACx40G38 mutant cell pair. The all-points current histogram revealed 235-pS main state conductance and 60-pS residual conductance levels, respectively. (D) Single-channel current (I_j) recorded at the maintained V_j of 50 mV from a WT hCx40 N2A cell pair. The dashed line corresponds to an ∼138-pS conductance level. (E) Average of unitary conductances measured from A96S (139 ± 2 pS; n = 32), M136V (131 ± 2 pS; n = 32), and G38D (220 ± 3 pS; n = 67) cell pairs. The dashed line denotes the unitary conductance of WT Cx40 (135 ± 1.4 pS; n = 72). Error bars represent means ± SEM.