Glycine modulation of NMDA-evoked release of [3H]acetylcholine and [3H]dopamine from rat striatal slices.

Superfused slices of rat striatum were used to investigate whether N-methyl-D-aspartate (NMDA) receptors mediating [3H]acetylcholine (ACh) and [3H]dopamine (DA) release are modulated by glycine. Kynurenic acid, a compound possessing antagonist activity at the receptor's glycine modulatory site, dose-dependently blocked NMDA release of both transmitters. The inhibition was reversed by glycine, D-serine, D-alanine, D-cysteine, L-serine and L-alanine. The relative potencies of these amino acids was in agreement with their previously reported abilities to inhibit strychnine-insensitive [3H]glycine binding and enhance [3H]MK-801 binding to the NMDA receptor complex. These data indicate that glycine modulatory sites are linked to NMDA receptors involved in striatal [3H]ACh and [3H]DA release.