7-Chlorokynurenic acid is a selective antagonist at the glycine modulatory site of the N-methyl-D-aspartate receptor complex.
- 1 September 1988
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences
- Vol. 85 (17), 6547-6550
- https://doi.org/10.1073/pnas.85.17.6547
Abstract
Glycine markedly potentiates N-methyl-D-aspartate (N-Me-D-Asp) responses in mammalian neurons by an action at a modulatory site on the N-Me-D-Asp receptor-ionophore complex. Here we present evidence that 7-chlorokynurenic acid (7-Cl KYNA) inhibits N-Me-D-Asp responses by a selective antagonism of glycine at this modulatory site. In rat cortical slices 7-Cl KYNA (10-100 .mu.M) noncompetitively inhibited N-Me-D-Asp responses, and this effect could be reversed by the addition of glycine (100 .mu.M) or D-serine (100 .mu.M). Radioligand binding experiments showed that 7-Cl KYNA had a much higher affinity for the strychnine-insensitive [3H]glycine binding site (IC50 = 0.56 .mu.M) than for the N-Me-D-Asp (IC50 169 .mu.M), quisqualate (IC50 = 153 .mu.M), or kainate (IC50 > 1000 .mu.M) recognition sites. In whole-cell patch-clamp recordings from rat cortical neurones in culture, the inhibitory effects of 7-Cl KYNA on N-Me-D-Asp-induced currents could not be overcome by increasing the N-Me-D-Asp concentration but could be reversed by increasing the glycine concentration. 7-Cl KYNA could completely abolish N-Me-D-Asp responses, including basal responses in the absence of added glycine, suggesting that it may possess negative modulatory effects at the glycine site. These findings indicate that the glycine modulatory site is functional in intact adult tissue and that 7-Cl KYNA should prove to be a selective tool for elucidating the involvement of this site in physiological and pathological events mediated by N-Me-D-Asp receptors.Keywords
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