Nitric oxide synthase inhibition and extracellular glutamate concentration after cerebral ischemia/reperfusion.
Nitric oxide synthase inhibition and extracellular glutamate concentration after cerebral ischemia/reperfusion.
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DOI：
10.1161/01.str.26.2.298
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发表时间：
1995-02
期刊：
影响因子：
8.3
通讯作者：
J. Zhang;H. Benveniste;B. Klitzman;C. Piantadosi
中科院分区：
文献类型：
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作者：
J. Zhang;H. Benveniste;B. Klitzman;C. Piantadosi
背景和目的大鼠短暂性脑缺血会导致神经元活力的选择性丧失，例如海马CA 1神经元。负责这种选择性缺血/再灌注（IR）的神经化学变量似乎涉及兴奋性氨基酸。在脑IR中，兴奋性氨基酸毒性可能受内源性一氧化氮（NO）调节。气体为了研究NO在全脑IR中的作用，我们测定了抑制NOS对大鼠间质兴奋性氨基酸的影响。同时观察脑缺血后脑血流量和血脑屏障功能的变化。方法采用系统性降压和阻断双侧颈总动脉15 min的方法造成前脑缺血模型。通过松开颈动脉并再灌注血液恢复血流60分钟。使用立体定位装置将微透析探针放置到皮质和海马中。在IR期间用高效液相色谱法测量间质谷氨酸浓度。在缺血前30分钟腹腔内给予竞争性NOS抑制剂N ω-硝基-L-精氨酸甲酯（L-NAME），剂量为1、4和20 mg/kg。采用激光多普勒血流仪和荧光素钠微透析法测定IR时脑血流量和血脑屏障的变化。结果：缺血再灌注期间透析液中的谷氨酸短暂增加10倍，再灌注30分钟时恢复到基线水平。在缺血前30分钟用L-NAME处理的动物在缺血期间也显示谷氨酸浓度增加，但在再灌注期间谷氨酸仍然升高。L-精氨酸可阻止L-NAME引起的再灌注期间谷氨酸浓度的增加。L-精氨酸和L-NAME联合给药可降低缺血时细胞外谷氨酸浓度。脑血流量在缺血期间下降到基线值的约5%，但在再灌注时相对于对照值增加约四倍。缺血后的充血反应在用或不用L-NAME的IR组之间没有差异。脑缺血增加了血脑屏障对荧光素的渗透性;然而，这种变化被20 mg/kg的L-NAME给药减弱。结论：NOS抑制不能减少缺血时细胞外谷氨酸的积累，并增加其在再灌注时的浓度。L-NAME治疗大鼠IR后谷氨酸浓度升高似乎不是由于缺血后脑血流反应减少或局部血脑屏障通透性增加所致。在大多数情况下，血脑屏障幸免于立即postisemic期间L-NAME治疗。这些数据表明，NO.生产可能会反对突触兴奋性氨基酸积累和推测兴奋性毒性在IR。
BACKGROUND AND PURPOSE Transient cerebral ischemia in rats results in selective loss of neuronal viability, eg, hippocampal CA1 neurons. The neurochemical variables responsible for this selective vulnerability to ischemia/reperfusion (IR) appear to involve excitatory amino acids. In brain IR, excitatory amino acid toxicity may be modulated by endogenous nitric oxide (NO.) gas. To investigate NO. in global brain IR, we measured the effects of NO. synthase (NOS) inhibition on interstitial excitatory amino acids in rats. Changes in postischemic cerebral blood flow and blood-brain barrier function also were evaluated. METHODS Forebrain ischemia was produced by systemic hypotension and occlusion of both carotid arteries for 15 minutes. Blood flow was restored for 60 minutes by unclamping the carotids and reinfusing with blood. A microdialysis probe was placed into the cortex and hippocampus using a stereotaxic device. Interstitial glutamate concentration was measured during IR with high-performance liquid chromatography. A competitive NOS inhibitor, N omega-nitro-L-arginine methyl ester (L-NAME), was given intraperitoneally 30 minutes before ischemia in doses of 1, 4, and 20 mg/kg. Changes in cerebral blood flow and blood-brain barrier during IR were determined using laser-Doppler flowmetry and microdialysis with sodium fluorescein. RESULTS Glutamate in the dialysate during IR increased transiently 10-fold and returned to baseline levels by 30 minutes of reperfusion. Animals treated with L-NAME 30 minutes before ischemia also showed increases in glutamate concentration during ischemia, but glutamate remained elevated during reperfusion. The increase in glutamate concentration during reperfusion caused by L-NAME was prevented by L-arginine. The administration of L-arginine and L-NAME together decreased extracellular glutamate concentration during ischemia. Cerebral blood flow decreased to about 5% of baseline values during ischemia but increased approximately fourfold relative to control values on reperfusion. The hyperemic responses after ischemia were not different between IR groups treated with or without L-NAME. Brain ischemia increased the permeability of the blood-brain barrier to fluorescein; however, this change was attenuated by L-NAME administration at 20 mg/kg. CONCLUSIONS NOS inhibition did not attenuate extracellular glutamate accumulation during ischemia and increased its concentration on reperfusion. The elevated glutamate concentration after IR in L-NAME-treated rats did not appear to be due to either a decrease in cerebral blood flow response after ischemia or increases in local blood-brain barrier permeability. For the most part, the blood-brain barrier was spared in the immediate postischemic period by L-NAME treatment. These data suggest that NO. production may oppose synaptic excitatory amino acid accumulation and presumably excitotoxicity during IR.