Figure 15.

${\mathrm{K}}_{\mathrm{HVA}}^{+}$ and resurgent sodium current promote burst firing in NMc neurons. (A and B) Representative membrane responses recorded from an NMc neuron to 5 Hz sinusoidal current injections in control and during dual-drug application of Guangxitoxin (GxTx, 100 nM) and TEA to block ${\mathrm{K}}_{\mathrm{HVA}}^{+}$ channels (I_KHVA blockade). Gray area of the second sinusoidal cycle in (A) was expanded and shown in (B). (C) Simulated membrane responses from model NMc neuron to 5 Hz sinusoidal current injections under three conditions: control (left), with removal of resurgent sodium current (no resurgent I_Na, middle) and with removal of both resurgent sodium current and $K_{HVA}^{+}$ conductances (no resurgent I_Na and I_KHVA, right). (D) The expansion of simulated membrane responses to the first cycle of sinusoidal current injections under three conditions. The inter-spike interval (ISI) represents the time difference between the first and second APs. (E) The expansion of simulated Na_V currents underlying the burst firing shown in (D). Inset showing the enlargement of first AP. Arrow and green arrowhead point to the generation of resurgent sodium current between APs. Red arrowhead points to zero resurgent sodium current. Blue arrowheads point to the generation of persistent sodium current. AP indicates action potential.