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 penumbr al 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 towar ds 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 w ere no changes in the EEG recordings or cerebral blood flow during these la te glutamate peaks. (C) 2001 Elsevier Science Ireland Ltd. All rights reser ved.