Development of new assessment for exercise intensity from the view point of brain activation; from brain lactate and hormone in rats with treadmill running.

运动可以促进神经发生、学习和认知功能，但什么样的运动适合于增强大脑健康还不清楚。为了解决这一问题，我们研究了如何在大鼠海马/下丘脑的神经元将在运动过程中被激活，以响应其强度，通过监测大脑乳酸和激素在跑台运行。当神经元激活时，脑乳酸从星形胶质细胞释放到细胞外室，其增加被认为是神经元激活的指标。首先，以乳酸阈（LT）为指标建立大鼠跑台运动模型。在我们的模型中，LT约为15 m/min。通过Takita等人（1992）建立的在线微透析测量了跑步机跑步期间海马/下丘脑中乳酸水平的变化。不同强度跑台运动时海马乳酸水平呈速度依赖性升高。在固定速度（10 m/min）跑时，海马乳酸水平也较跑前升高，并趋于稳定。钠通道阻断剂TTX（10 μM河豚毒素）或谷氨酸摄取抑制剂PDC（1 mM吡咯烷-2-4-二羧酸盐）预处理可完全阻断固定速度下海马乳酸的变化。运行.下丘脑乳酸水平的变化与海马相似。这些结果表明，海马神经元在低强度运动（低于LT）下也能以速度依赖的方式激活。这项研究表明，低强度运动可能会增强大脑健康。

Exercise enhances neurogenesis, learning and cognitive function, but it is unknown what kind of exercise would be suit for enhancing brain fitness. To address this, we investigated that how the neurons in rat hippocampus/hypothalamus would be activated during exercise in response to its intensity by monitoring the brain lactate and hormones during treadmill running. Brain lactate is released from astrocytes to extracellular compartment when neuronal activation is occurred, and its increase is considered as the indicator of neuronal activation. First, we established the treadmill running model of rats by estimating LT (Lactate Threshold) as a criterion. In our model, LT was about 15 m/min. The change in lactate level in the hippocampus/hypothalamus during treadmill running was measured by on-line microdialysis which had been established by Takita et al. (1992). The lactate level in hippocampus during a graded treadmill running increased with speed-dependent manner. During a fixed low speed running (10 m/min), the lactate level in hippocampus also increased from on set of running, and became plateou. Pretreatment of sodium channel blocker, TTX (tetrodotoxin, 10 μM), or glutamate uptake inhibitor, PDC (pirrolidine-2-4-dicarboxylate, 1mM) completely blocked the change in hippocampal lactate during a fixed speed. running. The changes of lactate level in hypothalamus were similar as these in the hippocampus. These results suggest that hippocampal neurons could activate with running with speed-dependent manner, though low intensity (below the LT) of exercise. This study suggests the possibility that low intensity exercise would enhance brain fitness.