FIGURE 1.

Block of wild-type BIB ionic current by extracellular calcium and barium. (A) Decrease in current amplitude after replacement of 4.5 mM Mg²⁺ saline with 4.5mM CaCl₂ or BaCl₂ saline, as monitored with repeated steps to +40 mV. (B) Representative current traces from +80 to −70 mV in 10-mV increments from a holding potential of −40 mV for wild-type BIB activated in Mg²⁺ saline and after perfusion with Ca²⁺ or Ba²⁺ salines. Scale bars indicate 5 μA and 100 ms. (C) Dose-dependent block of BIB conductance by external Ca²⁺ and Ba²⁺ (see text for details). Data points are mean ± SD, n = 3–12 per treatment. (D) Current-voltage relationships for data illustrated in B. (E) Summary histogram of the relative outward rectification values for wild-type BIB currents in salines containing 4.5 mM Mg²⁺, 4.5 mM Ca²⁺, or 4.5 mM Ba²⁺. Rectification values are absolute values of the ratio of current magnitudes at +50 and −70 mV (see text for details). Asterisks indicate significance (^*p < 0.01, ^**p < 0.001, ANOVA, Bonferroni post hoc test).