Quantitative changes in neuroglia in the white matter of the mouse brain following hypoxic stress

Two experimental and one control group of 70-80 day old mice were used in this study. The two experimental groups were subjected to hypoxia for 2 days in a decompression chamber at 390 mmHg. The animals in one experimental group were killed on removal from the chamber (hypoxic group) while those in the other (recovery group) were allowed to recover at sea-level atmospheric pressure for one week before being killed. Semithin, toluidine blue stained sections from the anterior limb of the anterior commissure were examined to find whether any quantitative changes occurred in the neuroglia with hypoxic stress. The following changes were observed: (1) The percentage of astrocytes in the hypoxic and recovery groups was significantly (P less than 0-005) lower than in the control group. (2) The percentage of oligodendrocytes in the hypoxic and recovery groups was significantly (P less than 0-001) higher than in the control group. (3) The percentage of microglia in the recovery groups was significantly (P less than 0-02) lower than in either of the other two groups. (4) The percentage of astrocytes in the recovery group was slightly (2-1%) higher than in the hypoxic group, and although not statistically significant, this result suggested that a slow return to normal might be occurring. (5) Little change was observed in cell density. The possible significance of these changes is discussed. I should like to express my indebtedness to Dr E.J. Clegg of the Department of Anatomy, Sheffield University, for the use of the decompression chamber, for his advice and help in the preparation of the control and experimental animals, and also for his hospitality throughout the duration of the experiments. Thanks are also due to Mrs Sheila Ramsay for her careful preparation of the perfusing fluids, and to Mrs Dawn Alexander for typing the manuscript.