Effect of preceding in vivo sublethal ischemia on the evoked potentials during secondary in vitro hypoxia evaluated with gerbil hippocampal slices.

We investigated the mechanism of 'ischemic tolerance phenomenon' by characterizing the physiological events, modified by preceding sublethal ischemia, during secondary hypoxia. Slices from brains after pretreatment of sublethal forebrain ischemia were subjected to a 70% reduction of PO2 (threshold hypoxia). Although evoked potentials disappeared completely in five of eight slices from sham-operated brain, they were sustained in 28/32 slices from pretreated brains. This study indicates that the maintenance of membrane function might be the mechanism of ischemic tolerance.