Figure 6. Sodium currents.

Sodium current in LN in response to depolarizing voltage-step as shown. Sodium currents are not well space-clamped as the sodium channels are located on the processes, not the cell body we record from, and this is also responsible for the delay between the depolarizing step and the onset of channel opening. In this trace, the cell was held at -70 mV and a series of depolarizing traces applied to activate the channel. -30 mV was the first sweep to activate the currents, and is characterized as the activation threshold. The transient current amplitude is about 300 pA, and the persistent current amplitude is about 100 pA in this case. Mutant cells may have activation thresholds and/or current amplitudes greater or lower than wildtype cells. The channel deactivates after the stimulus step has ended, a phenotype that is sometimes impaired in mutant cells. Voltage sweeps can be applied after channel activation to investigate channel deactivation threshold as well.