Figure 7.

VSFP2.3 sensing currents have little effect on fast action potential waveforms in simulations of Purkinje and layer 5 pyramidal neurons. (A) Overlaid action potential waveforms (aligned to the time of peak maximum) in the Purkinje neuron (left panel) and the soma (middle panel) and axon initial segment (right panel) of the layer 5 neuron including 1000 units /μm² (black traces) of VSFP2.3 (Model I) as compared to control waveforms (no VSFP; gray traces). The potentials were taken from the first spike in voltage transients evoked by a constant current step (same as in Fig.5) as shown in the inset with the stimulus onset marked by arrow. (B) Na⁺ currents flowing through voltage-gated sodium channels during membrane voltage traces in A. Inset traces are plotted at enlarged y-scale (given by separate scale bars; same units as main y-scale) to emphasize the subthreshold regime (peak currents truncated). (C) Gating currents associated with Na⁺ channel gating. (D) Summed total gating currents of voltage-gated ion channels. (E) VSFP2.3 sensing currents during membrane voltage traces in A. Timescales in B–E identical to A.