Cortical spreading depression affects reactive oxygen species production

Cortical spreading depression (CSD) is a reversible electrophysiological phenomenon that is not associated with tissue damage under normal blood supply. The induction of CSD during ischemia causes an increase in tissue damage, while pre-conditioning with CSD decreases the damage induced by a subsequent episode of ischemia. The mechanisms underlying these effects are not clear. Because the production of reactive oxygen species (ROS) is involved in tissue damage during ischemia-reperfusion, the aim of the present study was to evaluate the effects of CSD on superoxide production (O(2)(-)), on hydrogen peroxide (H(2)O(2)) production and on superoxide dismutase (SOD) activity in the cerebral cortex. CSD was induced by KCl application on the cortical surface in rats. O(2)(-) production was evaluated using dihydroethidium (DHE) that is oxidized to the fluorescent dye ethidium (HEt) by O(2)(-). The extracellular level of H(2)O(2) was evaluated by microdialysis sampling and HPLC analysis. SOD activity was evaluated with a histochemical assay. The results showed an increase in H(2)O(2) production, an increase in SOD activity and a decrease in O(2)(-) concentration 1h after CSD induction.