Figure 4. Effects of Cs⁺ on other Ca²⁺-dependent parameters.

Each panel shows voltage traces recorded in the presence and absence of 3 mM Cs⁺ (all are superimposed except in B where only the spikes evoked by a single train are superimposed) to illustrate effects on: A, action potential (AP) duration measured at half-amplitude (e.g. horizontal arrow), relative to baseline (dashed line); B, AP broadening, measured as the percentage change in duration observed between the first and the last AP evoked by a train; C, HAP amplitude (e.g. vertical arrow); and D, AHP amplitude relative to baseline. All action potentials (A and C) were evoked from a constant initial membrane potential and a silent interval of at least 20 s occurred before each test. The spike trains in B and D (clipped amplitude) were evoked by a depolarizing current pulse applied every 20 s and the initial membrane potential was maintained constant by DC current injection. The right panels are bar histograms showing the effects of 3-6 mM Cs⁺ on mean (+ s.e.m.) AP duration (A; % of control; n = 8), AP broadening (B; % broadening; n = 8) HAP amplitude (C; % of control; n = 14) and AHP amplitude (D; % of control; n = 7). Note that none of the parameters were significantly affected (i.e. P > 0.05; see text for absolute values).