Voltage dependence of sodium channel slow inactivation in lamina I/II neurons. A) Voltage waveform protocol whereby P2 test currents follow a 10 second conditioning pulse at variable potentials. Currents were recovered from fast inactivation at -120 mV for 100 ms before P2. Vhold = -100 mV. B) Representative sodium channel current traces during P2 tests pulses following 10 s conditioning pulses from -110 mV to + 10 mV. Scale bar x axis = 2 ms, y axis = 250 pA. C) Average fraction of P2 sodium channel current relative to P1 current amplitude during recordings as illustrated in A (n = 9). LJP = 4.2 mV, uncorrected.