Fast-slow analysis of AP bursting generated from modeled neuron. The phase plot of burst firing elicited by continuous current injection shows the projection of the burst trajectory onto n-o plane. n and o denote the activation gates of CaV3.1 and KCa channels, respectively. Arrows indicate the direction of trajectory movement. The solid and dashed lines are the voltage nullcline (i.e., dV/dt = 0) of the fast subsystem with n and o as parameters. Below the nullcline is the silent region. Notably, as the value of gM was increased from 0.02 to 0.04 mS/cm2, the nullcline was shifted in an upward direction with minimal change in the burst trajectory. When the values of gM and gKCa were simultaneously elevated by two-fold to mimic the effect of NGEG (10 μM), the burst trajectory was clearly compressed in combination with a further upward shift in the voltage nullcline.