Glutamate release in the gerbil hippocampus after middle cerebral artery occlusion.

In a modified version of the unilateral middle cerebral artery occlusion (MCAO) model in gerbils, both sides of hippocampus are spared from direct ischaemic insult. Using this newly employed left MCAO model in gerbils, we investigated the concentrations of extracellular amino acids in the left hippocampus by microdialysis and histological changes in both sides of hippocampus one month after ischaemia. The concentrations of glutamate and aspartate were significantly increased by more than 3.5 times basal levels after MCAO. Glutamate maintained this peak level for 40 to 120 min after the onset of ischaemia. However, hippocampal neurones were well preserved one month after MCAO. While the exact mechanism of the survival of hippocampal neurones remains to be elucidated, we suggest it may be crucial that the hippocampus be protected from ischaemic insult.