Blocking Glutamate uptake elevates extracellular D-serine by acting through AMPA receptors. (A) Raw trace showing glutamate (Glu) increase following a 50 minute incubation in 10 μM TFB-TBOA. (B) TFB-TBOA significantly elevated Glu in all conditions tested. There was no difference in Glu between experiments where TFB-TBOA was added. (C) TFB-TBOA elevated D-serine in the presence of cyclothiazide which was blocked by the application of 50 μM GYKI. A, B, C DAO- retinas (*, statistically different from control, p<0.05, n=6-7).