Abstract
Despite having no effect on basal phosphoinositide hydrolysis, N-methyl-D-aspartate (NMDA) inhibited carbachol-stimulated accumulation of 3H-inositol phosphates and enhanced that due to noradrenaline in guinea-pig cerebral cortex slices. The glycine antagonist 7-chlorokynurenic acid inhibited the effects of NMDA and this inhibition was reversed by glycine. The action of 7-chlorokynurenic acid was not mimicked by strychnine or HA 966 (1-hydroxy-3-aminopyrrolid-2-one). L-Glutamate also inhibited carbachol-stimulated accumulation of 3H-inositol phosphates, but this inhibition was not blocked by 7-chlorokynurenic acid. The data are consistent with glycine maintaining tonic control over NMDA receptor activity in guinea-pig brain.