预运动训练对大鼠脑梗死后脑内谷氨酸水平动态变化的影响

Effects of preconditioning treadmill exercise on the dynamic changes of brain glutamate level after cerebral infarction in rats

目的研究预先电动跑台运动训练对大鼠脑梗死后大脑中枢兴奋性氨基酸水平变化的影响，探讨预运动对缺血脑损伤保护作用的机制。方法将Sprague-Dawley大鼠随机分为5组（每组实验用时均为4周）：运动1周组（运动训练1周，在第4周实施）、运动2周组（运动训练2周，在后2周实施）、运动4周组（运动训练4周）、假手术组和缺血组。各组大鼠在实验4周后，于脑内纹状体留置微透析管，进行大脑中动脉缺血术，采用微透析技术收集大鼠缺血前、缺血期间（40，80和120min）和再灌注后（40，80，120，160，200和240rain）的脑细胞外液。测定大脑兴奋性氨基酸含量的变化，选取谷氨酸（Glu）含量作为兴奋性氨基酸的主要参考值。同时测量缺血再灌注24h时的脑梗死体积。结果缺血再灌注24h时不同组间脑梗死体积变化差异有统计学意义（P〈0．05）。2周和4周的预先电动跑台运动训练可显著下调因缺血而过度升高的Glu浓度（P〈0．01）。结论至少2周的预运动训练对随后发生的脑损伤缺血期及再灌注期间，大脑内重要的兴奋性氨基酸递质——Glu的过度释放有一定程度的抑制作用，这可能是运动对早期脑缺血损伤的保护机制之一。

Objective To study the effects of preconditioning treadmill exercise on excitatory amino acid changes in rats after the cerebral infarction and the protective effects against cerebral ischemia brain injury. Methods Thirty Sprague-Dawley rats were used in this study. Twenty-five rats were subject to an operation to establish the animal model of middle cerebral artery occlusion and divided into aischemia group, an 1-week exercise group （trained in the 4th week）, a 2-week exercise group （trained in the 3rd and 4th weeks） and a 4- week exercise group （trained for 4 weeks） , while the remaining 5 rats were subject to sham operation, and served as the controls. After 4 weeks of experiment, all the the rats were fixed on stereotactic apparatus for the brain microdialysis of the striatum. Then the focal middle cerebral artery ischemia and reperfusion were made with thread oeelussion in rats and microdialysis technique was used to collect extraeellular fluid in each period of pre-ischemia, ischemia （40, 80 and 120 min） , and reperfusion （40, 80, 120, 160, 200 and 240 rain） to detect the changes of the excitatory amino acid. At the same time the infarction volume was also measured at 24 hours after isehemia-reperfusion of the brain. Results The difference between any two groups was significant with regard to the volume of cerebral infarction （P 〈0.05）. Two weeks and four weeks of the preconditioning treadmill exercise couled significantly reduce concentration of Glu excessively released due to the ischemia （ P 〈 0.01 ）. Conclusion At least two weeks of preconditioning treadmill exercise can inhibit the excessive release of the important excitatory amino acid neurotransmitter glutamate, to some extent, in the process of the subsequent ischemic brain injury and during reperfusion, which might be one of the protective mechanisms of movement against the early ischemie brain injury.