The effect of intravenous insulin on accumulation of excitotoxic and otheramino acids in the ischemic rat cerebral cortex

Insulin has been reported to be neuroprotective during cerebral ischemia/re perfusion. However, it may also increase the sensitivity of cultured cortic al neurons to glutamate toxicity. The experiments described here utilized a rat four-vessel occlusion model with cerebral cortical windows to determin e the effects of intravenous insulin, alone (I) or combined with glucose (I G) to maintain physiologic blood glucose levels, on the extracellular accum ulation of amino acids in superfusates of the cerebral cortex. Aspartate, p hosphoethanolamine, taurine and gamma-aminobutyric acid were increased in t he I and IG groups and glutamate was increased in the IG group compared to controls during ischemia/reperfusion. Insulin treatment attenuated the rebo und in cortical superfusate glucose levels in both groups of animals during reperfusion. The increases in amino acid release during reperfusion may be due to a lack of glycolytically derived energy available for amino acid up take systems and ionic pumps. (C) 2000 Elsevier Science Ireland Ltd. All ri ghts reserved.