THE ROLE OF GLYCINE IN ANOXIA AGLYCAEMIA-INDUCED POTENTIATION OF N-METHYL-D-ASPARTATE RECEPTOR-MEDIATED POSTSYNAPTIC POTENTIALS IN THE RAT HIPPOCAMPUS

During brain ischaemia there is a sustained increase in extracellular glycine levels, and the potential role of these changes in modulating N-methyl-D-aspartate (NMDA) receptor-mediated activity following an an oxic/aglycaemic insult was studied in the rat hippocampal slice. Addit ion of large saturating concentrations of glycine (100 mu M and 1 mM) to the superfusate resulted in increased extracellularly recorded NMDA receptor-mediated components of excitatory postsynaptic potentials (E PSPs) recorded in area CA1. The effects of added glycine were strychni ne-insensitive and blocked by a competitive NMDA antagonist. Anoxic/ag lycaemic insults to the tissue caused persistent increases in NMDA rec eptor-mediated EPSPs, but the magnitude of the observed upregulation w as unaffected by the presence of added saturating concentrations of gl ycine. The data suggests that alterations in glycine levels after oxyg en deprivation are not responsible for the long term modulation of NMD A receptor activity.