Effect of pulsatile stimulus amplitude.

<p><b>A.</b> Single APs elicited by the standard pulsatile stimulus (V_m(t) units are arbitrary, with the syn_clamp1_200Hz AP as reference) calculated for syn_clamp1_200Hz or syn_clamp5_200Hz, and V-gated currents (INa_T, where T signifies the transient component; persistent INa not shown), IK (delayed rectifier) plus the INa component of current through the AChR channels; gNa_max = 700 μS, stimuli at 200 Hz. <b>B.</b> For such APs elicited by pulsatile synaptic stimulation at increasing intensities (from syn_clamp0.5_200Hz to syn_clamp5.0_200Hz), Na⁺-entry via the stimulus (AChR) channels increases dramatically (red) but total Na⁺-entry (green) is almost unaffected. The V_peak is relatively insensitive to stimulus intensity beyond syn_clamp = 1 (an “all-or-none” AP feature). <b>C.</b> Further testing of pulsatile syn_clamp intensity, for APs at 200 Hz and 600 Hz with the gNa_max values indicated. The dashed black line in <b>C</b> is equivalent to the dashed black line in <b>B</b> (where values are normalized).