Figure 3.

Gating of the anion channel is Na⁺ concentration dependent only in neuronal EAATs. (A) Averaged macroscopic currents amplitudes measured at +60 mV in response to perfusion of varying concentrations of Na⁺ in oocytes expressing either EAAT1 (red circles) or EAAT4 (blue squares; left panel) and in oocytes expressing EAAT2 (red circles) or EAAT3 (blue squares; right panel). Currents were normalized to the response to application of NaNO₃ solution at +60 mV and represent the mean and SEM from 5 to 12 oocytes for each condition and ≥3 frogs. Data were analyzed by a 2-way ANOVA comparing carriers vs. Na⁺ concentration with a Bonferroni post hoc analysis. (B) Accumulation of 3,4-³H-L-glutamate by oocytes expressing EAAT1 (red circles) or EAAT4 (green circles; left panel), and from oocytes expressing EAAT2 (black circles) or EAAT3 (orange circles; right panel), in solution that contained 200 nM 3,4-³H-L-glutamate + 10 μM glutamate and the indicated concentration of sodium was replaced with equal molar concentrations of choline and transport was normalized to the maximum transport activity at 140 mM Na⁺. Data were fitted with a non-linear curve to obtain an EC₅₀ and Vmax.