| Objective:Duplicate a model of hypoxic-ischemic brain damage(HIBD),to evaluate the effect of hyperbaric oxygenation(HBO) therapy on different stages of HIBD rats by observing histomorphologic changes at the CAl region of hippocampus and improvement of the learning and memory ability, further expose the influence of HBO therapy on microtubule-associated protein 2(MAP-2) expression in the hippocampal CAl subregion , thereby investigate the mechanism of HBO on neuronal regeneration and restoration after HIBD. Methods:Unsexed 7-day-old Wistar rats were used as research subjects,and randomly divided into 5 group: the HIBD group(n=12), the HBO early-treated group(n=12), the HBO late-treated group(n=8), the sham operation group(n=12) and the control group(n=6).The HIBD model pups were subjected to unilateral left carotid artery ligation followed by 2h of hypoxia(8%O2 at 37 degree C).HBO treatment was administered by placing pups in a chamber (0.2MPa for lh,once a day for 7 days) 4h after hypoxic-ischemia(HI) in HBO early-treated group,and 14 days after HI in HBO late-treated group.One group of HBO early-treated rats were decapitated 7 days after HBO treated post-HI (n=6), and for the learning and memory ability test an additional group of HBO early-treated and HBO late-treated rats were sacrificed after assessing the learning and memory ability 23 days post-HI by step through test. Sham operation and HIBD rats were also included in both experiments.Brain samples of all groups were collected to evaluate histomorphologic changes by hematoxylin and eosin(H&E) staining and immuhistochemical analysis of MAP-2 expression in the hippocampal CAl subregion.Results:The pathologic features in the HIBD group of 14-day-old were as follows: degeneration,necrosis,liquation,malacia of left brain and cavum formation; the pyramidal cell layer of celluar demarcation,coagulationnecrosis,cytoplasmic eosinophilia and nucleur pyknosis(condensed,spear- or triangle-shaped shrunken nucleus),there was significant difference between HIBD group and sham operation group.In HBO early-treated group,there was no significant difference in cytohistology of the coxtex and the hippocampal CA1 subregion, but the pyramidal cell layer was thinner than that in sham operation group.On post-HI d 23,obvious atrophy of left brain and proliferation of neuroglial cells could be seen in HIBD group,the pathologic changes in the hippocampal CA1 subregion was similar to that in HIBD group of 14-day-old. In HBO late-treated group there were similar changes in the left brain but more neurons were preserved in the CA1 compared to HIBD group.Immunohistochemical staining showed the reaction for MAP-2 in control group and sham operation group clearly visualized neuronal soma and dendrites.There was a significant decrease in MAP-2 expression in the HIBD group in different time points. The dendrites morphological changes could be seen such as curling,intermittence and decrease in quantity in HIBD group and HBO late-treated group,but the degree lightened in the latter group.No significant difference was observed between sham operation group and HBO early-treated group.The quantitative results of graylevel value of MAP-2 were as follows(The less the graylevel value,the higher level of MAP-2):At 14-day-old time point,HIBD group: 136.32 ±4.31,there was marked increase compared with sham operation group( 124.51 ±4.04) and HBO early-treated group(124.78±3.08)(P<0.01);At 30-day-old time point,fflBD group:136.61± 3.28,marked increased compared with sham operation group( 124.22± 1.61) and HBO early-treated group(126.87 ± 2.73)(P<0.01),and obviously increased compared with HBO late-treated group(133.17±4.17)(P<0.05).No significant difference between HBO early-treated group and sham operation group in different time point,whereas the greylevel value of HBO late-treated group was obviously increased compared with HBO early-treated group and sham operation group at the same time point.In the learning and memory ability test,the rate of memory-keeping was... |
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