Figure 4.

Inward conductance as a function of external [Na⁺]. (A) I-V relationships in the presence of different [Na⁺] with replacement by NMDG⁺. All solutions were nominally Ca²⁺ free. Currents were normalized to values obtained at V_m = −100 mV with 110 mM NaCl. In the case of [Na⁺] = 220 mM, the currents were normalized to those obtained at V_m = −100 mV with 110 mM NaCl + 110 mM NMDG·Cl. Data represent means ± SEM for 5–11 measurements. (B) Inward slope conductance as a function of [Na⁺]. Slope conductances were normalized to values at 110 mM NaCl (G₀) and were fit to the following equation: G/G_max = [Na⁺]/{[Na⁺] + K_Na}. Best-fit values were G_max = 1.23 ± 0.12, K_Na = 25 ± 8 mM.