Ultrastructural Changes of Hippocampus after Exhaustive Treadmill Running in Rats
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Yanru Zhang, Rongmei Xu, Qinghua Song, Yan Shang and Jianjun Zhang
Hippocampal CA1 (cornuammonis 1) pyramidal neurons are extremely sensitive to ischemia and hypoxia. Transient global cerebral ischemia can induce cell death in a particular form known as delayed neuronal death (DND). In this paper, the rats’ brain hippocampal pyramidal cells and mitochondrial morphological changes were studied to further reveal the process of nerve degeneration, the impact of exercise on learning, memory and other functions. To observe the ultrastructural changes in hippocampal pyramidal cells and cerebral mitochondria of rats after endurance exercise training. Methods: The study was conducted during June 2015 to November 2017 in Zhengzhou University. Selected 40 eight-week old male SD rats, which were randomly divided into four groups: Group A (no training); Group B, the 24 h acute exhaustive exercise group (no training, acute exhaustive treadmill exercise the day before sacrificed); Group C, the endurance training group with immediate acute exhaustive exercise (endurance training implementation and acute exhaustive treadmill exercise and sacrificed immediately after exercise), and group D, endurance training and 24 hours later after acute exhaustive exercise groups (endurance training and acute exhaustive treadmill exercise, then sacrificed 24 hours later). Each group had 10 rats. For the training groups, exhaustion exercise started the next day at a rate of 10 m/min. Gradually the speed was increased up to a predetermined speed (medium and higher exhaustive exercise respectively at a speed of 20 m/min and 36 m/min), and maintained speed until exhaustion, then record the exhaustive exercise time. The training plan was rats in treadmill exercise trained once a day, 6 days per week, treadmill speed is gradually increased from the beginning of the fourth week of 10 m/min to 30 m/min, exercise time from 30 min/d to 40 min/d. Exhaustion standard for rats is driven out in the end to stay 2 s treadmill reluctant to run, and the loss of quick turn reflex. Main outcome measures: After being sacrificed, ultrastructural changes in the rats brain hippocampus pyramidal cells and their mitochondria were studied. Results: 40 SD rats completed the experimental trial and all results were analyzed. It showed that the number of apoptotic cells in the brain of rats increased significantly after endurance training and exhaustive exercise group. Exhaustive exercise increased the number of apoptotic cells, among which were mostly glial cells. The percentage of apoptotic cells in brain and the degeneration of pyramidal cell and mitochondria by transmission electron microscopy in rats’ hippocampus increased significantly. Conclusion: We observed that endurance training and exhaustion exercise might cause certain damage to brain cells, the hippocampus neurons and mitochondria degeneration. This may be due to exhaustive training that caused brain tissue acidosis; meanwhile lack of oxygen caused some degeneration of brain cells that affecting the memory.
Endurance training; Exhaustive treadmill exercise; cell apoptosis; delayed neuronal death; pyramidal cell; mitochondria