BRAIN REGIONAL DIFFERENCES IN GLYCINE REVERSAL OF ETHANOL-INDUCED INHIBITION OF N-METHYL-D-ASPARTATE-STIMULATED NEUROTRANSMITTER RELEASE

The present study investigated the interaction between glycine and eth anol on N-methyl-D-aspartate (NMDA)-stimulated neurotransmitter releas e in hippocampal, cerebrocortical, and striatal slices from rat brain. Some, but not all, previous studies have shown that glycine may rever se the inhibitory effect of ethanol on NMDA receptors. Hippocampal or cortical slices were prepared and prelabelled with [H-3]norepinephrine , and striatal slices were labelled with [H-3]dopamine. Stimulation of the slices with 500 mu M NMDA for two minutes caused a significant re lease of [H-3]neurotransmitter in each brain region above basal. Ethan ol (60 mM) significantly inhibited the NMDA-stimulated release of neur otransmitter from all brain regions. Addition of glycine (0.3-3 mu M) to the buffer bathing the slices had no effect on the inhibitory effec t of ethanol in hippocampus or cortex. However, in striatal slices, 0. 3 and 1.0 mu M glycine added to the buffer reversed the inhibitory eff ect of ethanol on NMDA-stimulated [H-3]dopamine release without having any effect on either basal or NMDA-stimulated release by itself. Thes e results show that the interaction between ethanol and glycine varies in different brain regions. Therefore interpretation of the potential inhibitory effect of ethanol on NMDA receptor function in vivo should consider brain region and local concentrations of glycine.