N-methyl-D-aspartate-evoked release of acetylcholine from the medial septum/diagonal band of rat brain.

N-Methyl-D-aspartate (NMDA)-evoked release of [3H]acetylcholine (ACh) from slices of rat brain medial septum/vertical limb of the diagonal band (ms/vdB) was examined. NMDA increased the release of tritium in a concentration-dependent manner and the specific non-competitive NMDA antagonist, MK-801, and the competitive NMDA antagonist kynurenic acid inhibited this release. Tetrodotoxin inhibited the NMDA-evoked release suggesting the [3H]ACh released arises from collaterals of the cholinergic septohippocampal neurons. Basal release of tritium was significantly increased by glycine alone and strychnine inhibited this response while having no effect on NMDA-evoked release. However, glycine, although not affecting the NMDA-evoked release, did enhance release of tritium in the presence of NMDA and blocking concentrations of Kynurenic acid. Together, these findings suggest that under the conditions of these experiments sufficient concentrations of glycine permit the full expression of NMDA-evoked modulation of [3H]ACh release, and that the predominant actions of glycine were mediated by a specific, strychnine-sensitive receptor.