Effect of cortical spreading depression on the levels of mRNA coding for putative neuroprotective proteins in rat brain

Previous studies have demonstrated that cortical spreading depression (CSD) induces neuronal tolerance to a subsequent episode of ischemia. The object ive of the present investigation was to determine whether CSD alters levels of mRNA coding for putative neuroprotective proteins. Unilateral CSD was e voked in male Wistar rats by applying 2 mol/L KCl over the frontal cortex f or 2 hours. After recovery for 0, 2, or 24 hours, levels of several mRNA co ding for neuroprotective proteins were measured bilaterally in parietal cor tex using Northern blot analysis. Levels of c-fos mRNA and brain-derived ne urotrophic factor (BDNF) mRNA were markedly elevated at 0 and 2 hours, but not 24 hours after CSD. Tissue plasminogen activator (tPA) mRNA levels were also significantly increased at 0 and 2 hours, but not 24 hours after CSD. Levels of the 72-kDa heat-shock protein (hsp72) mRNA were not significantl y increased by CSD, except for a small elevation (20%) at 2 hours recovery. Levels of the 73-kDa heat-shock cognate (hsc73) mRNA were slightly, but si gnificantly, increased at 2 and 24 hours of recovery. Finally, levels of mR NA for protease nexin-l and glutamine synthetase were not significantly alt ered by CSD at any time studied. The current results support the hypothesis that neuronal tolerance to ischemia after CSD may be mediated by increased expression of FOS, BDNF, or tPA, but not by increased expression of hsp72, hsc73, nexin-1, or glutamine synthetase.