Fig. 1.

Effect of changing external calcium on membrane currents recorded from a Cx50^−/− fiber cell using the whole cell patch-clamp technique. A: families of current traces were recorded from the fiber cell shown in B in the presence of 0 Ca²⁺ and 2 mM Mg²⁺ (left), after exposure to 1 mM Ca²⁺ and 1 mM Mg²⁺ (middle), and finally after exposure to 1 mM Ca²⁺, 1 mM Mg²⁺, and 1 mM La³⁺ (right). A series of depolarizing steps was applied in 10 mV increments between −60 and 80 mV from a holding potential of −60 mV. The intracellular pipette solution in these whole cell patch-clamp experiments contained 140 mM CsCl to block potassium currents. Dashed line represents zero current. Scale bar = 100 μm. C: current-voltage (I–V) relations obtained from the data shown in A. The current was measured at the end of the 8-s pulse and plotted as a function of voltage after correction for liquid junction potential. D: bar graph summarizing the La³⁺-sensitive current data at the holding potential in the presence of the indicated concentrations of Mg²⁺ and Ca²⁺. Data are means ± SE. Number of cells indicated by the values in parentheses. *P < 0.002, compared with the hypothesized population mean of 0.0 using the one-sample t-test.