Real-time measurement of glutamate release from the ischemic penumbra of the rat cerebral cortex using a focal middle cerebral artery occlusion model

Following permanent middle cerebral artery occlusion, extracellular penumbral glutamate levels, measured by a realtime glutamate electrode, increased in two different patterns. In 7/11 rats, glutamate increased from baseline levels of 19 +/- 4 (mean +/- SEM) to 208 +/- 29 muM and then declined towards baseline levels. Blood flow in the penumbral area declined to 30% of pre-ischemic levels with recovery to 60 and 70% of baseline values by 3 and 6 h, respectively. Four of 11 rats in the study also exhibited late peaks of glutamate release (120 +/- 40 muM) 2 h after the onset of ischemia. There were no changes in the EEG recordings or cerebral blood flow during these late glutamate peaks. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.