Figure 1.

Properties of Na_V1.7^WT and Na_V1.7^C1143F expressed in cultured cortical neurons. (a–f) Biophysical characterization of Na_V1.7^WT and Na_V1.7^C1143F in cultured cortical neurons. Because cortical neurons express endogenous Na_V1.7 channels, as well as many other types of sodium channels, we used a tetrodotoxin (TTX)-resistant form of Na_V1.7 (Supplementary Information, Na_V1.7^Y362S) and blocked endogenous channels with 500 nm TTX. (a) Representative set of sodium current traces from cortical neurons expressing Na_V1.7^WT and Na_V1.7^C1143F. (b) Mean current–voltage (I–V) relationships of peak currents. (c) Voltage dependence of activation (right curves, the V_1/2 of channel activation was 19.7±4.4 mV for Na_V1.7^WT and 19.3±9.3 mV for Na_V1.7^C1143F, P>0.05) or the voltage dependence for steady-state fast inactivation (left curves, V_1/2 for Na_V1.7^WT was −62.6±1.6 mV and for Na_V1.7^C1143F −69.7±3.62 mV, P>0.05). (d) Recovery from fast inactivation (τ=3.72±0.6 ms in Na_V1.7^WT and 7.63±1.35 ms in Na_V1.7^C1143F, P=0.017). (e and f) Mean normalized currents during 100 depolarizations to 0 mV at 20 Hz (e) and 50 Hz (f). Na_V1.7^WT, n=7, Na_V1.7^C1143F, n=5. Firing of cortical neurons expressing Na_V1.7^WT and Na_V1.7^C1143F. (g) Representative firing in response to 160 pA depolarizing current injection. (h) Membrane input resistance. (i) Rheobase, the minimal current needed to evoke action potentials (AP) (j) average number of AP in response to 1 s depolarizing current injection at the indicated intensity. The resting membrane potential was unaffected by the C1143F mutation (−65.8±2.7 mV in Na_V1.7^WT and −60.7±3.6 mV in Na_V1.7^C1143F, P>0.05). Similarly, the threshold for action potential (−32.7±1.7 mV for Na_V1.7^WT and −27.68±5.4 mV for Na_V1.7^C1143F, P>0.05) and cell capacitance (95.6±22 pF in Na_V1.7^WT and 85.3±37 pF in Na_V1.7^C1143F, P>0.05) were unchanged. *P<0.05. Na_V1.7^WT, n=7, Na_V1.7^C1143F, n=5.