Fig. 10.

HCY does not rescue effects of partially blocking the GLY site with dichlorokynurenic acid (DCKA). DCKA (1 μM, 10-s preincubation) inhibited peak NMDAR current amplitude by ∼80% in the presence (B2 vs. B1) and absence (A2 vs. A1) of bathing 1 mM HCY. DCKA largely prevented the ability of HCY to reduce GLY-dependent desensitization. It is as if HCY was not even present when DCKA was preincubated, because HCY + NMDA + DCKA currents desensitize similarly to NMDA + DCKA (see normalized superimposed traces A3 and B3), indicating that DCKA blocks the effects of both HCY and GLY on desensitization (N = 5 for DCKA alone, N = 4 for DCKA + HCY).