EFFECTS OF MILD HYPOTHERMIA ON THE RELEASE OF REGIONAL GLUTAMATE AND GLYCINE DURING EXTENDED TRANSIENT FOCAL CEREBRAL-ISCHEMIA IN RATS

The present study is to determine the effect of mild hypothermia (MHT) on the release of glutamate and glycine in rats subjected to middle c erebral artery occlusion and reperfusion. The relationship between ami no acid efflux and brain infarct volume was compared in different peri ods during MHT. Reversible middle cerebral artery occlusion was perfor med in Sprague-Dawley rats using a suture model. The rats were divided into four groups including (1) MHT during ischemia (MHTi), (2) MHT du ring reperfusion (MHTr), (3) MHT during ischemia and reperfusion (MHTi + r), and (4) a normothermic group (NT). Extracellular concentrations of glutamate and glycine in the cortex and striatum were monitored us ing in vivo microdialysis and analyzed using high-performance liquid c hromatography. Morphometric measurements for infarct volume were perfo rmed using 2,3,5-triphenyltetrazolium chloride staining. The increase of glutamate and glycine in the ischemic cortex of the MHTi and MHTi r rats during ischemic and reperfusion periods was significantly less than that of the NT rats (p < 0.05). However, there was no statistica l difference among these groups in the peak of glutamate and glycine r elease in the striatum. Infarct volume paralleled the release of gluta mate and glycine. The protective effect of MHTi and MHTi + r in reduci ng ischemia and reperfusion brain injury may be due to the attenuation of both glutamate and glycine release during ischemia and reperfusion .