Minimal effect of brain temperature changes on glutamate release in rat following severe global brain ischemia: a dialysis electrode study

USING a dialysis electrode, we recently developed an oxygen-independent sys tem for real-time measurement of the glutamate concentration in the extrace llular space ([Glu]e) during ischemia. This system allows separate evaluati on of intra-ischemic biphase [Glu]e elevation, i.e. release from synaptic v esicles (1st phase), reversed uptake of glutamate from metabolic pools in n euronal cells (2nd phase), and post-ischemic glutamate re-uptake in ischemi a-reperfusion models. Using the system, we attempted to clarify the relatio nship between biphase glutamate release and brain temperature in a model of acute global ischemia produced by transecting both carotid arteries. Our r esults showed that, in contrast to mild hyperthermia, hypothermia did not i nhibit the Ist phase of [Glu]e release, and changes in intra-ischemic brain temperature had a minimal effect on the 2nd phase of [Glu]e elevation duri ng severe acute ischemia. These findings, together with our previous data, indicate that brain temperature change in the intra-ischemic period plays a n important role in disturbance of the glutamate re-uptake system during is chemia. NeuroReport 9: 3863-3868 (C) 1998 Lippincott Williams & Wilkins.