Fig. 6
Representative original recordings of brain-tissue oxygen concentration (tissue O2) of the cortex and the hippocampus of a rat exposed to +3.0 Gz acceleration for 15 s without anti-G equipment. Brain-tissue oxygen concentration was measured by the oxygen monitor (multi-channel oxygen monitor, Eikou-Kagaku, Tokyo) with polarographic oxygen electrodes inserted directly to the cortex and the hippocampus. Abbreviations were same as Fig. 5. Acceleration of +3.0 Gz for 15 s without anti-G equipment decreased cortical O2 concentration from 61 ± 32 to 44 ± 28 mmHg, that is 71 ± 2 %, and hippocampal O2 concentration from 63 ± 34 to 33 ± 27 mmHg, that is 52 ± 6 %. The %-decrease in hippocampal O2 concentration was significantly larger than that in cortical O2 concentration. In addition to the decreases, the recovery time to the control level was significantly longer in the hippocampus than in the cortex. The effects of +3.0 Gz acceleration without anti-G equipment on O2 concentration were larger in the hippocampus than in the cortex [19, 21, 27]