Figure 5. Sodium currents in iPSC-derived neurons from ASD patients and controls show different voltage dependence of steady-state inactivation.

A, B, Inward sodium currents evoked by depolarizing test jumps to −20 mV from pre-test potentials of −90 mV to −25 mV (A) or −45 mV (B) in steps of 5 mV. C, Peak inward current amplitudes as a function of pre-test potential from the data in A and B. The results were normalized to Imax values obtained for each neuron from fits to the raw data (as in D and E). D, E, Steady-state inactivation data obtained from 10 control neurons (D) and seven patient neurons (E). Data for individual cells are shown with different symbols and colors (normalized data in C are shown here with the same symbols: control, open black square; patient, filled black circle). For some neurons, the results were better fitted as the sum of two components (arrowheads point to E_h1/2 values for each component). F, Bar graph depicting the percentage of control and patient neurons (n = 10 and 7) with E_h1/2 values that fell within the indicated ranges. When two components were present, the fractional amplitudes of each were used in the calculation of mean percentages for each group. Cells that gave E_h1/2 values ≤ −65 mV gave half-activation voltages that ranged from −39.1 to −55.8 mV, a phenotype most consistent with the Na_v1.1 brain sodium channel isoform (Catterall et al., 2005).