Measurement of striatal H 2O 2 by microdialysis following global forebrain ischemia and reperfusion in the rat: correlation with the cytotoxic potential of H 2O 2 in vitro

Abstract

Toxic reactive oxygen species have been implicated as important mediators of tissue injury after reperfusion of ischemic organs. When rats are subject to 30 min global forebrain ischemia, 24 h following this insult, there is substantial loss of medium-sized neurones as revealed by histological sectioning of the striatal region of the forebrain. The goal of this study was to utilize microdialysis to directly measure one of the more stable intermediates of reduced molecular oxygen. H 2O 2 in the rat striatum following 4-vessel occlusion and reperfusion, and to correlate these levels with H 2O 2 toxicity to neurones grown in culture. A significant rise in striatal H 2O 2 levels was observed for about 1 h during reperfusion, amounting to an increase of approximately 100 μM at the peak. In control experiments where the dialysis probe was embedded in cortical regions surrounding the striatum (where there is no neuronal loss due to the ischemic episode), there was no measurable increase in tissue H 2O 2 levels. H 2O 2 has been previously shown to be neurotoxic to PC12 cells as well as rat primary hippocampal neurones at comparable concentrations striatal neurones experience during reperfusion. We demonstrate that H 2O 2 is also neurotoxic to the human cortical neuronal cell line, HCN-1A. These experiments establish an important link between oxidant generation and neuronal loss in this tissue following global forebrain ischemia.