The rising slopes and threshold potentials in two AISS phases are different, in which phase two is dependent upon phase one. A) shows an expanded waveform of AISS that has a step-like upstroke with Vts one and two. B) shows a phase-plot for this expanded AISS waveform that is divided into two phases with slope one and two. C) illustrates a plot of slope two versus slope one from twenty-nine GABAergic neurons. The slope for phase one is larger than that for phase two, and CV of slope two is larger than CV of slope one (inset). There is a linear correlation between slope two and slope one (r2 = 0.58). D) illustrates phase-plot for the expanded waveforms of AISS that is divided into two phases from a neuron. E) shows a plot of slope two versus slope one from this neuron. F) illustrates a linear correlation between slope two versus inter-phase intervals (IPI) this neurons, i.e., the onset of phase two is influenced by the refractory period of phase one.