Glycine and kynurenate modulate the glutamate receptors in the myenteric plexus and in cortical membranes.

The responses evoked by stimulation of the N-methyl-D-aspartate receptors in the guinea-pig myenteric plexus were potentiated by micromolar concentrations of glycine and were non-competitively antagonized by kynurenate (IC50: 60 microM). The effects of kynurenate were competitively prevented by glycine. Furthermore, kynurenate displaced [3H]glycine from its binding sites on rat cortical membranes (IC50: 20 microM). Kynurenate and glycine, therefore, probably act at the same site, evoking opposite effects on the function of the ion channel complex of the N-methyl-D-aspartate receptor.