Figure 5. Effect of nitrous oxide, when present only during 6 min of hypoxia, on recovery of the evoked population spike recorded in the CA1 region of rat hippocampal slices. Slices were subjected to 95% nitrous oxide only during hypoxia (solid line); after hypoxia, the slices were aerated with 95% oxygen. This is described as experimental series 4 in Materials and Methods. Control slices, made hypoxic without nitrous oxide (dashed line), had significantly better recovery of the population spike. The oxygen concentration was the same in both groups throughout the experiment and 5% carbon dioxide was present in all gas mixtures. The x axis shows the time after slice preparation and the percentage of oxgyen in the gas mixture. Values shown are means +/- SEM; n = 15 animals per group. *P < 0.05.