Figure 4

Potassium channel blockers reduce the increase in AP amplitude observed in the presence of TTX for hyperpolarized holding potentials. Responses from a single small DRG neuron (inset waveforms a-f on the right) demonstrate that the increase in AP amplitude observed in the presence of TTX with depolarization of membrane holding potential from -90 to -60 mV (inset waveforms a-c) is much smaller in the presence of TEA and 4-AP. In contrast, the decrease in AP amplitude with depolarization from holding potentials of -60 to -25 mV (inset waveforms c-f) is unchanged in the presence of TEA and 4-AP. The decrease can be fit with a single Boltzmann equation (dashed line in main figure, V_1/2 = -38.8 mV). The dotted lines in inset waveforms indicate 0 mV.