Anesthetic protection against anoxic damage in the rat hippocampal slice

Evoked population spikes were recorded from the dentate granule cell layer of hippocampal slices obtained from adult rats. These slices were subjected to short periods of anoxia in the presence of different anesthetics. The recovery of the population spike after anoxia was compared across treatments. Little or no recovery was found after 10 min of anoxia when no anesthetic (4 +/- 4%), 1.5% isoflurane (5 +/- 5%), or 15% isoflurane (0 +/- 0%) was present during the anoxic periods. However, the population spike did recover to 81 +/- 7% of its preanoxic amplitude within 1 h after the anoxia if thiopental 160 mg/liter was present in the perfusate during the anoxia. Fifteen percent isoflurane and 160 mg/liter thiopental were equipotent in reducing the amplitude of the evoked population spike before anoxia but only thiopental protected against the damage after 10 min of anoxia. Our results suggest that the blocking of the evoked population spike by thiopental is not the sole mechanism of its protection against anoxic damage. Isoflurane (1.5%) was able to provide a small degree of protection against shorter periods (7 min) of anoxia.