| Objective:To explore the interaction of hypoxia and exercise training in simulated altitude training on the learning and memory ability of rats and its intervention. And explore the relationship between the learning and memory ability and synaptic plasticity, to provide strong experimental evidence for scientific implementation of altitude training.Method:The6-week-old male SD rats were randomly divided into4groups:control group (group C), hypoxia control group (group HC), exercise training group (group E), hypoxia with exercise training group (group HE). After8weeks of14.2%hypoxic exposure or/and no load swimming training? the learning and memory function of rats was observed by Morris water maze test. The ultrastructure of hippocampus in rats was observed、the GABA content and the expression of BDNF, NR1and NR2B mRNA in hippocampus were measured.Results:①According to two-way ANOVA analysis, it was obvious that the long hypoxic exposure could significantly increase the incubation period (p<0.05)and reduce the number of cross-platform (p<0.05)of rats; In contrast, moderate exercise training could shorten the incubation period (p<0.05) and increase the number of cross-platform (p<0.05) of rats notably. There was no remarkable interaction of hypoxia and exercise training (simulated altitude training) on shortening the incubation period and improving the number of cross-platform of rates (p>0.05)②By electron microscopy, in group C, the hippocampus synaptic cleft was clearly visible. Postsynaptic membrane dense material (PSD) was thick. Synaptic vesicles gathered in presynaptic terminal. There were plenty of mitochondria, and the structure was normal. In group HC, the number of hippocampus synaptic cleft was fewer. The synaptic cleft was blurred and synaptic interface was smaller. The structure of mitochondria were deformed and blurred. In Group E, a large amount of hippocampal synapses and clearly visible synaptic cleft were observed. Synaptic interface curvature was large and postsynaptic membrane dense material (PSD) was significantly thick. Rich synaptic vesicles gathered in presynaptic terminal. The number of mitochondria increased and structure was clear. Compared with that in group E, the number of synapses and synaptic vesicles was fewer in group HE. The thickness of postsynaptic membrane dense material (PSD) decreased. The number of mitochondria were fewer, and the structure was blurred.③According to two-way ANOVA analysis, long-term hypoxic exposure increased the content of GABA in hippocampus, but it was no statistical significance (P>0.05), exercise training could significantly reduce the content of GABA in hippocampus tissue of rats (P<0.05), and there is no significant interaction of exercise training and hypoxia on reducing the GABA content in hippocampus (P>0.05)④According to two-way ANOVA analysis, long-term hypoxic exposure could reduce the expression of NR1, NR2B and BDNF mRNA in the hippocampus significantly (P<0.05), exercise training could significantly increase the expression of NR1and NR2BmRNA in the hippocampus of rats (P<0.05), and it tended to increase the expression of BDNF mRNA in the hippocampus, but no statistical significance(P>0.05). There was no significant interaction of exercise training and hypoxia on the expression of NR1, NR2B and BDNF mRNA (P>0.05).Conclusion:(1) Long-term hypoxic exposure could inhibit the rats’ability of learning and memory by reducing the number of hippocampus synaptic cleft of rats, and increasing the content of GABA, and decreasing the expression of NR1, NR2B, BDNF mRNA in hippocampus.(2) Exercise training under normoxia could improve the ability of learning and memory in rats by increasing the number of synaptic cleft and the expression of NR2Band NR1mRNA, and decreasing the content of GABA in hippocampus.(3) Exercise training has some improvement on the ultrastructure of rats’hippocampus, the expression of NR1, NR2B, BDNF mRNA and the ability of learning and memory, but there were no significant interaction. |
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