Figure 3.

(A) Laser-pulse photolysis experiment in the absence of SCN⁻ ([glutamate] = 60 ± 10 μM, V = 0 mV, SCN⁻ was replaced by an equimolar concentration of CI⁻) (SCN⁻-free trace). The time constants were τ_rise = 0.2 ± 0.1 ms, and τ_decay = 5.6 ± 0.4 ms. The SCN⁻ internal trace shows, for comparison, a similar experiment in the presence of intracellular SCN⁻ (τ_decay = 6.3 ± 0.1 ms), which was rescaled (factor 0.22) to match the maximum amplitude of the two currents. (B) Laser-pulse photolysis experiment in the presence of extracellular SCN⁻ (V = 0 mV, [glutamate] = 40 ± 10 μM, NaSCN-based extracellular solution, KCl-based intracellular solution). The time constant for the rise of the inward current were τ = 0.3 ± 0.1 ms, and for the rise of the outward current τ = 2.7 ± 0.6 ms (fit as in Fig. 2B). (C) Inhibition of the glutamate transporter by TBOA in the absence and presence of 25 μM glutamate. Bottom trace, control experiment in the absence of TBOA. The upper two traces show the same experiment after 2 s pre-incubation with 5 μM and 100 μM TBOA, respectively (V = 0 mV, KSCN-based intracellular solution, NaCl-based extracellular solution).