Fig. 5.

Comparison of the effect of Mg²⁺ on the kinetic and steady-state components of ΔF/F.(A) A_τ/ΔF_{+60 mV} -V curves were obtained in the absence (filled circles) or presence (open circles) of Mg²⁺. Data are shown as mean ± SEM, n = 4–9 (*, P < 0.05, one-way ANOVA). For comparison, double Boltzman fits to the ΔF/F–V data obtained in the absence (solid line) or presence (dashed line) of Mg²⁺ are also shown (see B). (B) Normalized steady-state ΔF/F–V curves were obtained in the absence (filled squares) or presence (open squares) of Mg²⁺. Each curve was fitted by the sum of two Boltzmann functions (solid lines). In the presence of Mg²⁺, V_1/2 values for the hyperpolarized and depolarized components were -108 ± 1.7 mV and -20 ± 0.1 mV, respectively. Both components had apparent valences of 0.7 ± 0.1. For fitted values of V_1/2 and z in the absence of Mg²⁺, see Fig. 1 legend. Data are shown as mean ± SEM, n = 4–9 (*, P < 0.05, one-way ANOVA). (C) The fitted hyperpolarized (Left) and depolarized (Right) steady-state components of ΔF/F in the absence (solid line) and presence (dashed line) of Mg²⁺ are shown.