MEASUREMENT OF STRIATAL H2O2 BY MICRODIALYSIS FOLLOWING GLOBAL FOREBRAIN ISCHEMIA AND REPERFUSION IN THE RAT - CORRELATION WITH THE CYTOTOXIC POTENTIAL OF H2O2 IN-VITRO

Toxic reactive oxygen species have been implicated as important mediat ors of tissue injury after reperfusion of ischemic organs. When rats a re subject to 30 min global forebrain ischemia, 24 h following this in sult, there is substantial loss of medium-sized neurones as revealed b y histological sectioning of the striatal region of the forebrain. The goal of this study was to utilize microdialysis to directly measure o ne of the more stable intermediates of reduced molecular oxygen, H2O2 in the rat striatum following 4-vessel occlusion and reperfusion, and to correlate these levels with H2O2 toxicity to neurones grown in cult ure. A significant rise in striatal H2O2 levels was observed for about 1 h during reperfusion, amounting to an increase of approximately 100 mu M 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 measurabl e increase in tissue H2O2 levels. H2O2 has been previously shown to be neurotoxic to PC12 cells as well as rat primary hippocampal neurones at comparable concentrations striatal neurones experience during reper fusion. We demonstrate that H2O2 is also neurotoxic to the human corti cal neuronal cell line, HCN-1A. These experiments establish an importa nt link between oxidant generation and neuronal loss in this tissue fo llowing global forebrain ischemia.