Fig. 7. Reduction of NMDAR current in EAAT3⁺ oocytes under continuous flow conditions. (A) Glutamate (µmol l^-1) dose-response curves of EAAT3. Oocytes were injected with 40 ng of EAAT3 mRNA (filled circle) or 40 ng of NMDAR mRNA and 40 ng of EAAT3 mRNA (co-expression, open circle). In co-expressing oocytes, glutamate was in a glycine-free solution containing 5 mmol l^-1 Mg²⁺ to inhibit the NMDAR activation. Results are means ±S.D. (N=12 for EAAT3 single expressing oocytes and N=9 for co-expressing oocytes) of the percentage of the currents induced by various concentrations of glutamate in the maximal EAAT3 current induced by 300 µmol l^-1 of glutamate (I_max). (B) NMDA (µmol l^-1) dose-response curves of NMDAR. Oocytes were injected with 40 ng of NMDAR mRNA (filled circle) or 40 ng of NMDAR mRNA and 40 ng of EAAT3 mRNA (open circle). In co-expressing oocytes, no EAAT inhibitors were included in the superfusates. Results are means ±S.D. (N=6 for both NMDAR single expressing oocytes and co-expressing oocytes) of the percentage of the currents induced by various concentrations of glutamate in the maximal NMDAR current induced by 1 mmol of NMDA (I_max). (C) Dose-response curves of glutamate-induced current. Oocytes were injected with 40 ng of NMDAR mRNA (filled circle) or 40 ng of NMDAR mRNA and 40 ng of EAAT3 mRNA (open circle and open triangle) or 10 ng of NMDAR mRNA and 40 ng of EAAT3 mRNA (filled triangle). EAAT3 activity was inhibited by replacing Na⁺ with Li⁺ in the solution and the data are presented as open triangle in the graph. Results are means ±S.D. (N=16 for filled circle, N=15 for open circle, N=10 for filled triangle and N=6 for the open triangle) of the percentage of the currents induced by various concentrations of glutamate in the maximal current induced by 300 µmol l^-1 of glutamate (I_max). (D) Relationship between the EC₅₀ shift of the dose-response curves of glutamate-induced current and the percentage of EAAT3 current in the total glutamate-induced current in the co-expressing oocytes. EAAT3 current was isolated from NMDAR current by using a glycine-free solution containing 5 mmol l^-1 Mg²⁺ to inhibit the NMDAR activation/current. Each data point represents data from one oocyte. A linear regression yielded an r=0.607 (P<0.05).