FOOD-DEPRIVATION PROTECTS THE RAT STRIATUM AGAINST HYPOXIA-ISCHEMIA DESPITE HIGH EXTRACELLULAR GLUTAMATE

In a model that combines hypoxia with ischemia, the relationship betwe en histological outcome, evoked rise in blood glucose, and striatal gl utamate release was investigated in the 24-h food-deprived and normall y fed rat. Food deprivation protected the dorsolateral striatum very e ffectively, as was shown with a silver stain. An online monitoring tec hnique based on microdialysis showed that, in the protected condition, more glutamate was released into the striatal extracellular space tha n in the compromised condition. The possibility that the microdialysis results were influenced by a difference in shrinking of the extracell ular space following food deprivation was excluded by the measurements of whole-tissue impedance. During the hypoxic-ischemic challenge, blo od glucose rose in normally fed rats, but was suppressed almost comple tely after food deprivation. These results led us to conclude that, in our model of hypoxia-ischemia, the amount of glutamate released is no t related directly to the extent of brain damage, but the increase in blood glucose may determine at least part of the brain damage.