Glycine reverses 7-chlorokynurenic acid-induced inhibition of [³H]MK-801 binding

7-Chlorokynurenic acid (7-Cl KYNA) has been reported to attenuate N-methyl-d-aspartate (NMDA) receptor functioning by a potent and selective inhibitory action mediated at the strychnine-insensitive glycine recognition site of the NMDA complex. Here we report that 7-Cl KYNA dose-dependently inhibits [³H]MK-801 binding to the PCP receptor, and that this effect is reversed by addittion of glycine. Since [³H]MK-801 binding is a measure of channel activation, our results are consistents with the hypothesis that 7-Cl KYNA exerts its NMDA receptor antagonism by acting at the glycine site, and that activation of the glycine site is required for NMDA channel activity to occur.