Is the loss of the tooth a risk factor of the Alzheimer's disease? Examination by microdialysis methods

目的：为探讨磨牙缺失对学习记忆的影响，用遥测谷氨酸生物传感器测量被动回避任务中海马区谷氨酸的释放。EXT组(n=8)在全身麻醉下拔除上颌磨牙，CON组(n=8)麻醉后不拔牙。在7周龄时，这些大鼠接受了由习得和保持试验组成的被动回避任务。同时测定海马谷氨酸释放量。首先，在习得试验期间，将大鼠放入一个明亮的隔间，并测量它们进入黑暗隔间之前的持续时间(反应潜伏期)。在老鼠进入黑暗的隔间后，立即通过栅格地板施加了电击。24小时后，进行保留试验，以相同的方法测量反应潜伏期。结果：在被动回避任务的反应潜伏期方面，在获得实验中，两组间无显著差异。在保留试验中，两组的反应潜伏期都增加了，但EXT组的反应潜伏期显著缩短。此外，EXT组在习得实验中海马区谷氨酸释放明显缩短，而在保留实验中，两组间谷氨酸释放无显著差异。结论：磨牙缺失可能阻碍学习记忆。

Purpose : To clarify the effects of molar tooth loss on learning and memory, hippocampal glutamate release during a passive-avoidance task was measured with a telemetric glutamate biosensor.Methods: Male Sprague-Dawley rats were used. Under general anesthesia, all the maxillary molars were extracted from the EXT group rats (n=8); those in the CON group (control, n=8) were anesthetized without tooth extraction. At age 7 weeks, the rats were subjected to a passive-avoidance task consisting of acquisition and retention trials. Simultaneously, hippocampal glutamate release was measured. First, during the acquisition trial, the rats were placed in a light compartment, and the duration before they entered a dark compartment was measured (reaction latency). Immediately after the rat entered the dark compartment, an electric shock was applied through a grid floor. After 24h, the retention trial was performed, and the reaction latency was measured in the same manner. Further, a biosensor was used to measure the release of hippocampal glutamate before and after the start of each trial.Results: Regarding the reaction latency during the passive-avoidance task, no significant differences were seen between the groups in the acquisition trial. Reaction latency increased in both groups in the retention trial, but was significantly shorter in the EXT group. Furthermore, hippocampal glutamate release in the acquisition trial was significantly shorter in the EXT group, but in the retention trial, no significant difference in glutamate release was seen between the groups.Conclusion: Molar tooth loss may impede learning and memory.