Profiles of glutamate and GABA efflux in core versus peripheral zones of focal cerebral ischemia in mice

Efflux of glutamate during cerebral ischemia is known to contribute to brai n cell death via processes of excitotoxicity. However, gamma -aminobutyric acid (GABA) is also released during ischemia, and may be protective. In thi s study, we used in vivo microdialysis to map the efflux of glutamate and G ABA from central core and peripheral zones of focal ischemia in mouse brain . We show that the temporal profiles of glutamate and GABA efflux are signi ficantly different in core versus peripheral zones. Calculation of glutamat e/GABA ratios demonstrate that, in the core, there is a significant increas e above baseline ratios during the first 30 mm of ischemia, which then rapi dly renormalizes. In contrast, no significant changes in glutamate/GABA rat ios were seen in the ischemic periphery. These data suggest that imbalances in glutamate versus GABA eff lux may be an initial trigger of excitotoxic brain damage in the core but not the peripheral zones of focal cerebral isc hemia. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.