兴奋性氨基酸、氧自由基与缺血再灌注脑损伤关系的实验观察

目的：观察脑缺血再灌注过程中兴奋性氨基酸（Ｅｘｃｉｔａｔｏｒｙ ａｍｉｎｏ ａｃｉｄ,ＥＡＡ）、氧自由基的变化,研究探索脑缺血再灌注损伤的机制。方法：测定假手术组、缺血３０ｍｉｎ再灌注６０ｍｉｎ生理盐水（ＮＳ）处理组和单唾液酸四已糖神经节苷脂（ＧＭ１,１０ｍｇ／ｋｇ,ＩＰ）处理组,鼠脑海马组织ＥＡＡ、丙二醛（Ｍａｌｏｎｄｉａｄｅｈｙｄｅ,ＭＤＡ）的含量。实验应用全脑缺血（４ＶＯ）模型,ＥＡＡ采用Ｈ     

Effects of hypothermia and lamotrigine on trace-conditioned learning after global cerebral ischemia in rabbits.

Acquisition of the trace-conditioned eye blink response (CR) is mediated by a variety of brain structures, including the cerebellum, the hippocampus, and brain stem nuclei. We examined the effects of a neuronal sodium channel antagonist (lamotrigine) on the ability of rabbits to acquire an eye blink CR after 6.5 min of cerebral ischemia. New Zealand white rabbits (n = 31) were randomly assigned to sham (S), normothermic ischemia (N), hypothermic (30 degrees C) ischemia-(H), or lamotrigine (50 mg/kg) treated (L) groups. In the N, H, and L groups, 6.5 min of global cerebral ischemia was produced using an inflatable neck tourniquet. Trace conditioning was started on the 7th postischemic day. The conditioned stimulus consisted of a tone (85 dB, 6 kHz) presented for 100 ms. The unconditioned stimulus was an air puff (150 ms duration) directed at the cornea. The interval between the end of the conditioned stimulus and the start of the unconditioned stimulus (the trace interval, TI) was 300 ms in duration. A trace-conditioned response was defined as an eye blink that was initiated during the TI. Eighty trials were delivered daily for 15 days. Neurologic deficits were greatest in the N group, and these animals had fewer CRs (149 +/- 157) than animals in the S (509 +/- 214) or H (461 +/- 149) groups (P < 0.05 by analysis of variance). Animals in the L group had a total number of CRs (380 +/- 253) that was intermediate between the S and N groups. Histologic evidence of neural injury was greatest in the N group. This study demonstrates that a brief episode of cerebral ischemia results in the impairment of this test of neurobehavioral function. Both hypothermia and lamotrigine were able to attenuate the impairment of eye blink trace-conditioned responses produced by cerebral ischemia.     

全脑缺血再灌注兴奋性氨基酸、线粒体钙、钙调素含量的变化

目的：采用大鼠全脑缺血再灌注模型,观察海马组织兴奋性氨基酸、线粒体钙、钙调素含量的变化,研究分析脑缺血再灌注损伤中兴奋性氨基酸与钙平衡紊乱的变化和作用。方法：测定假手术组,缺血３０ｍｉｎ再灌注６０ｍｉｎ和缺血３０ｍｉｎ再灌注１２ｈ组,脑海马组织兴奋性氨基酸、线粒体钙、钙调素的含量。结果：缺血３０ｍｉｎ再灌注６０ｍｉｎ海马组织兴奋性氨基酸明显低于假手术组（Ｐ＜０．０１）,线粒体钙、钙调素含量显著性高于假手术组（Ｐ＜０．０１）,缺血３０ｍｉｎ再灌注１２ｈ组同假手术组比较没有显著性差异（Ｐ＞０．０５）。结论：我们从鼠脑缺血再灌注时线粒体钙、钙调素含量升高证实钙平衡紊乱参于兴奋性氨基酸的缺血再灌注脑损伤过程     

单唾液酸四已糖神经节苷脂在脑缺血再灌注损伤中作用的实验研究

目的：观察单唾液酸四已糖神经节苷胸（GM1）对脑缺血再灌注损伤的保护作用。方法：采用四血管闭塞（4VO）全脑缺血再灌注动物模型，测定假手术组，缺血30min再灌注60minGM1；处理组（10mg／kg，缺血5min腹腔注射），缺血30min再灌注60min生理盐水（NS）处理组鼠脑海马组织兴奋性氨基酸（ExcitatoryAminoAcid，EAA），钙调素（Calmodulin，CaM），丙二醛（Malondiadehyde，MDA）的含量。结果：脑缺血再灌注组海马组织EAA含量显著性降低（P〈0．01），而CaM、MDA则显著性升高（P＜0．01），GM1处理组海马EAA、CaM、MDA含量同假术术组比较没有显著性差异（P＞0．05）。结论：GM1能阻抑脑缺血再灌注损伤中EAA的过度释放和／或重摄取障碍，细胞内外钙平衡紊乱，氧自由基产生过多等病理生理过程，发挥脑保护作用。     

Changes in the diffusion of water and intracellular metabolites after excitotoxic injury and global ischemia in neonatal rat brain.

The reduction of the apparent diffusion coefficient (ADC) of brain tissue water in acute cerebral ischemia, as measured by diffusion-weighted magnetic resonance imaging, is generally associated with the development of cytotoxic edema. However, the underlying mechanism is still unknown. Our aim was to elucidate diffusion changes in the intracellular environment in cytotoxic edematous tissue. The ADC of intracellular metabolites was measured by use of diffusion-weighted 1H-magnetic resonance spectroscopy after (1) unilateral N-methyl-D-aspartate (NMDA) injection and (2) cardiac arrest-induced global ischemia in neonatal rat brain. The distinct water ADC drop early after global ischemia was accompanied by a significant reduction of the ADC of all measured metabolites (P < 0.01, n = 8). In the first hours after excitotoxic injury, the ADC of water and the metabolites taurine and N-acetylaspartate dropped significantly (P < 0.05, n = 8). At 24 and 72 hours after NMDA injection brain metabolite levels were diminished and metabolite ADC approached contralateral values. Administration of the NMDA-antagonist MK-801 1.5 hours after NMDA injection completely normalized the water ADC but not the metabolite ADC after 1 to 2 hours (n = 8). No damage was detected 72 hours later and, water and metabolite ADC had normal values (n = 8). The contribution of brain temperature changes (calculated from the chemical shift between the water and N-acetylaspartate signals) and tissue deoxygenation to ischemia-induced intracellular ADC changes was minor. These data lend support to previous suggestions that the ischemia-induced brain water ADC drop may partly be caused by reduced diffusional displacement of intracellular water, possibly involving early alterations in intracellular tortuosity, cytoplasmic streaming, or intracellular molecular interactions.     

Lubeluzole inhibits accumulation of extracellular glutamate in the hippocampus during transient global cerebral ischemia

Increases in extracellular glutamate during cerebral ischemia may play an important role in neuronal injury. Lubeluzole is a novel neuroprotective drug, which in previous in vitro and focal ischemia studies has been shown to inhibit nitric oxide synthesis, to block voltage-gated Na+-ion channels, and to inhibit glutamate release. In this study, we investigated the ability of lubeluzole to inhibit glutamate accumulation during episodes of transient global cerebral ischemia. Twenty-five New Zealand white rabbits were randomized to one of four groups: a normothermic control group; a hypothermic group; a 1.25 mg/kg lubeluzole group; or a 2.5 mg/kg lubeluzole group. The animals were anesthetized, intubated, and ventilated before microdialysis probes were placed in the hippocampus. Lubeluzole was given intravenously 90 min before the onset of ischemia. Esophageal temperature was maintained at 38 degrees C in the control, and lubeluzole treated groups, while the animals in the hypothermia group were cooled to 30 degrees C. A 15-min period of global cerebral ischemia was produced by inflating a neck tourniquet. Glutamate concentrations in the microdialysate were determined using high-performance liquid chromatography (HPLC). During ischemia and early reperfusion, glutamate concentrations increased significantly in the control group and returned to baseline after 15 min of reperfusion. In the lubleuzole 2.5 mg/kg and hypothermia groups, glutamate levels were significantly lower (P<0.05) than in the control group and there was no significant change from baseline levels during the entire experiment. This study suggests that lubeluzole is effective in inhibiting extracellular glutamate accumulation during global cerebral ischemia, and has the potential to produce potent neuroprotection when instituted prior to an ischemic event.     

The relationship between the apparent diffusion coefficient measured by magnetic resonance imaging, anoxic depolarization, and glutamate efflux during experimental cerebral ischemia.

A reduction in the apparent diffusion coefficient (ADC) of water measured by magnetic resonance imaging (MRI) has been shown to occur early after cerebrovascular occlusion. This change may be a useful indicator of brain tissue adversely affected by inadequate blood supply. The objective of this study was to test the hypothesis that loss of membrane ion homeostasis and depolarization can occur simultaneously with the drop in ADC. Also investigated was whether elevation of extracellular glutamate ([GLU]e) would occur before ADC changes. High-speed MRI of the trace of the diffusion tensor (15-second time resolution) was combined with simultaneous recording of the extracellular direct current (DC) potential and on-line [GLU]e from the striatum of the anesthetized rat. After a control period, data were acquired during remote middle cerebral artery occlusion for 60 minutes, followed by 30 minutes of reperfusion, and cardiac arrest-induced global ischemia. After either focal or global ischemia, the ADC was reduced by 10 to 25% before anoxic depolarization occurred. After either insult, the time for half the maximum change in ADC was significantly shorter than the corresponding DC potential parameter (P < 0.05). The [GLU]e remained at low levels during the entire period of varying ADC and DC potential and did not peak until much later after either ischemic insult. This study demonstrates that ADC changes can occur before membrane depolarization and that high [GLU]e has no involvement in the early rapid ADC decrease.     

Propentofylline administered by microdialysis attenuates ischemia-induced hippocampal damage but not excitatory amino acid release in gerbils

Systemic administration of propentofylline (PPF), and adenosine uptake inhibitor, has been demonstrated to protect CA1 pyramidal cells from death following transient cerebral ischemia in gerbils. In order to examine the direct effects of this inhibitor, we tested whether or not PPF administered into the hippocampus in situ through a microdialysis probe could attenuate ischemia-induced excitatory amino acid (EAA) release and prevent subsequent death of CA1 pyramidal cells in the gerbil. The EAA release and death of CA1 pyramidal cells observed in the hippocampus were compared with those in the contralateral hippocampus of the same animal into which vehicle alone was administered. The results indicated that pre- as well as post-treatments with PPF inhibited the death of CA1 pyramidal cells after 5-min ischemia in a dose-dependent manner, but did not significantly alter the EAA release during ischemia and reperfusion in the same animals. While the neuroprotective effect of PPF against ischemic damage has commonly been ascribed to attenuation of EAA release during ischemia, other actions of adenosine such as those influencing the synaptic responses, neuronal excitation, and local cerebral circulation, or as yet unidentified actions may be involved in the observed neuroprotective effects of PPF.     

Intracellular acidosis during and after cerebral ischemia: in vivo nuclear magnetic resonance study of hyperglycemia in cats

In vivo 31P nuclear magnetic resonance spectroscopy was used to monitor the time course of intracellular pH in cat cerebral cortex subjected to global cerebral ischemia under control and hyperglycemic pretreatment conditions. Transient (16 minutes) global cerebral ischemia was induced in 14 cats using an inflatable cervical cuff combined with systemic arterial hypotension. Six cats were pretreated with infusion of 1.5 g/kg glucose prior to ischemia. Relative concentrations of high-energy phosphate metabolites and intracellular pH were continuously monitored before, during, and for 2 hours after cerebral reperfusion. During ischemia, intracellular pH fell to the same level and followed a similar time course in both groups. However, during initial reperfusion in the hyperglycemic group, there was a severe further decline (p less than 0.003) in intracellular pH. We suggest that the increased neurologic deficit and mortality found in hyperglycemic animals subjected to cerebral ischemia may be attributed to this transient severe tissue acidosis.     

线粒体钙、钙调素、兴奋性氨基酸、丙二醛在脑缺血再灌注中变化的实验观察

目的：观察脑缺血再灌注中线粒体钙（MitochondriaCaloium,MCa）、钙调素（Calmodulin,CaM）、兴奋性氨基酸（ExcitatoryAminoAcid,EAA）、丙二醛（Malondiadehyde,MDA）的动态变化,研究探索其变化时相,为阻抑其自稳平衡紊乱的发生提供科学的时间效应点。方法：采用大鼠全脑缺血再灌注模型（4VO）,测定假手术组、缺血30min再灌注1h、6h、12h组大脑皮层、海马组织MCa、CaM、EAA、MDA的含量。结果：缺血30min再灌注1h鼠大脑皮层、海马组织MCa、CaM、MDA含量显著升高,EAA含量显著降低,再灌注6h后,MCa、CaM继续升高,EAA、MDA回复到假手术组水平,当再灌注到12h时．MCa、CaM也相继回复到假手术组水平。结论：脑缺血再灌注早期（1h）,Ca++、EAA、氧自由基自稳平衡紊乱发生,Ca++自稳平衡紊乱回复较EAA、氧自由基晚。     

DWI动态评价大鼠脑缺血—再灌注损伤区的组织学特征

目的本研究运用磁共振弥散加权成像(DWI)技术动态评价大鼠脑缺血—再灌注损伤后不同时间脑损伤区DWI信号强度(SI)及表观扩散系数(ADC)的变化,结合组织学检测,分析损伤区组织学特征。方法健康成年SD雄性大鼠(n=80)随机分成8组,分别为脑缺血—再灌注1h、3h、6h、12h、1d、3d、7d组和假手术组,采用线栓法制作大鼠右侧大脑中动脉缺血—再灌注(MCAO/R)模型,Zea Longa评分评价神经功能损伤程度,Philips Achieva 3.0T MR扫描仪对假手术组和缺血—再灌注后不同时间点大鼠脑部行冠状位DWI扫描,在工作站上重建ADC图,测量基底核层面梗死灶DWI-SI和ADC值,计算相对ADC值(r ADC)和相对DWI-SI(r DWI-SI)值。2,3,5-氯化三苯基四氮唑(TTC)染色评价梗死体积的变化。苏木精—伊红染色观察组织形态学变化。结果假手术组动物麻醉苏醒后未见神经功能缺损,脑缺血—再灌注1h大鼠出现神经损伤,3h~1d时症状逐渐加重,3~7d时症状改善。假手术组DWI及ADC图均未见异常信号;MCAO/R后1h DWI上右侧纹状体及周围部分皮质区域出现高信号,相应部位ADC值降低,1h~1d DWI高信号范围随时间推移逐渐增大,信号强度逐渐增高,3~7d时开始降低;r ADC值随时间先降低后升高,6h达到最低,12h开始回升,1d时r ADC值较12h稍降低(P0.05),3d时r ADC升高,7d时与假手术组无明显差异(P0.05);1h~1d r DWI-SI持续升高,1d达最高峰,3~7d开始下降,7d时仍明显高于假手术组。苏木精—伊红染色显示假手术组右侧海马及皮质区结构未见明显异常;缺血—再灌注12h缺血侧海马区及皮质区出现可见部分浓染细胞和胞浆空泡形成,核固缩,但细胞排列尚好;1d时缺血侧神经元缺血损伤加重,细胞排列紊乱,细胞间隙增宽,出现大量胞浆空泡化,核固缩显著;3d时缺血侧海马区空泡化有所减轻。假手术组TTC染色未见梗死区域;脑缺血—再灌注1h可见右侧纹状体及周围少许皮质梗死;1h~1d梗死体积逐渐增大,1~3d时达到峰值,7d时梗死体积减小。1h~1d缺血侧脑水肿体积随时间持续增加,1d达到高峰,3d时开始下降,7d明显减轻。模型组各时间点神经功能评分与相应时间点基底核区梗死灶r DWI-SI呈显著性正相关(r=0.503,P=0.000);相应时间点脑梗死体积、水肿体积与r DWI-SI均呈显著性正相关(r=0.542,P=0.001;r=0.740,P=0.000)。结论磁共振弥散加权成像获得的DWI-SI及ADC值,对评价脑缺血再灌注损伤组织学特征具有高度的敏感性和特异性,对脑缺血—再灌注损伤后缺血区的动态改变具有直观的价值。     

The effect of 2-methoxyestradiol, a HIF-1 alpha inhibitor, in global cerebral ischemia in rats

Global cerebral ischemia is an important clinical problem with few effective treatments. The hippocampus, which is important for memory, is especially vulnerable during global ischemia. Brain-specific knockout of hypoxia inducible factor-1 alpha (HIF-1 alpha) has been shown to be protective in focal ischemia in vivo. 2-methoxyestradiol (2ME2) is a natural metabolite of estrogen that is known to inhibit HIF-1 alpha. We tested 2ME2 in a rat model of global cerebral ischemia. Global ischemia was induced with the two-vessel occlusion model (2VO) which entailed hemorrhagic hypotension to a mean arterial pressure of 38-42 mmHg with simultaneous bilateral common carotid artery occlusion for 8 minutes. Sprague-Dawley rats (male, 280-350 g) were randomly assigned to three groups: global ischemia (GI, n=17), global ischemia with 2ME2 treatment (GI + 2ME2, n=17) and sham surgery (sham, n=12). 2ME2 treatment (15 mg/kg in 1% DMSO) was rendered 10 minutes after reperfusion. Rats in the GI and sham groups received similar doses of the DMSO solvent. Rats were killed 24 hours, 72 hours and 7 days after reperfusion. Quantitative CA1 hippocampal cell counts demonstrated significantly lower cell survival in the GI + 2ME2 group compared to either the GI or sham groups, in spite of a statistically significant reduction in HIF-1 alpha by Western blotting analysis of the GI + 2ME2 group. We conclude that 2ME2 worsens outcomes after global ischemia in rats.     

大鼠脑缺血-再灌注损伤早期DWI参数和AQP4蛋白表达相关性研究

目的脑水肿是脑缺血后主要的病理表现之一,研究表明水通道蛋白4(AQP4)在脑梗死后脑水肿的形成和发展中起着重要作用,目前尚缺乏磁共振弥散加权成像(DWS)与AQP4表达在急性脑缺血-再灌注早期相关性的研究。本文旨在评估大鼠脑缺血—再灌注早期脑损伤区水通道蛋白4表达、DWI信号强度(SI)及表观扩散系数(ADC)之间的相关性以及AQP4表达与缺血性脑水肿之间的关系。方法健康成年SD雄性大鼠(n=40),随机分成4组,分别为脑缺血—再灌注12h、1d、3d组和假手术组,采用线栓法制作大鼠右侧大脑中动脉缺血—再灌注(MCAO/R)模型,Zea Longa评分评价神经功能损伤程度,Philips Achieva 3.0T MRI扫描仪对假手术组和缺血—再灌注后不同时间点大鼠脑部行冠状位DWI扫描,在工作站上重建ADC图,测量基底核层面梗死灶DWI-SI和ADC值,计算相对ADC值(rADC)和相对DWI—SI(rDWI—SI)值。2,3,5-氯化三苯基四氮唑(TTC)染色评价梗死体积的变化。免疫组化染色测定AQP4蛋白表达,用平均吸光度(MOD)值评价染色程度。结果假手术组动物麻醉苏醒后未见神经功能缺损,脑缺血—再灌注后12h、1d和3d组大鼠出现不同程度神经功能损伤,1d组最重。假手术组TTC染色未见梗死体积,脑缺血—再灌注后12h、1d和3d梗死体积逐渐增加,3d时最大。水肿变化规律同梗死体积相仿。假手术组海马区及皮质区AQP4免疫组化染色较浅淡,MCAO/R后12h缺血侧海马区及皮质均可见AQP4阳性细胞,12h-3d AQP4的MOD值随时间延长逐渐增高,3d时达到高峰。12h、1d和3d组大鼠脑水肿体积与相应时间点缺血侧皮质区和海马区AQP4表达均呈正相关(r=0.642,r=0.605,均P0.05);三组大鼠基底核区梗死灶rADC值与缺血侧皮质区、海马区AQP4表达均呈正相关(r=0.542,P=0.037;r=0.655,P=0.008)。结论大鼠脑缺血—再灌注早期脑水肿体积、rADC值与AQP4的表达水平存在时间上的相关性。因此结合DWI检查对脑缺血后AQP4表达部位、作用及调节机制进行更深入系统的研究,可能为临床早期治疗缺血性脑水肿提供新的思路。     

Prediction of delayed ischemic injury with diffusion-weighted MRI following temporary middle cerebral artery occlusion in rats

Early reductions in the apparent diffusion coefficient of water (ADC) during focal cerebral ischemia are often reversible with reperfusion. With sustained ischemia, the magnitude of the ADC reduction generally increases with time, which could reflect increased severity of ischemic damage. Thus, a threshold in ADC reduction may exist beyond which damage can not be reversed with reperfusion. The goal of this study was to determine if such a threshold exists that is independent of the duration of ischemia in a rat model. Rats were subjected to either 30, 60, or 90 min of temporary middle cerebral artery occlusion. ADC maps acquired just before and 30 min after reperfusion were compared to histology performed after a 72 h survival period to determine the relationship between ADC reduction and final ischemic injury. Significant variability in tissue recovery was observed for the 30 min group. Regions with ADC reductions of up to 45% often recovered, while some regions not exhibiting any change in ADC during occlusion showed ischemic injury at 72 h. Similar observations were made in cortical regions of the 60 min group. In the caudate-putamen, reduced ADC was often associated with ischemic injury. For the 90 min group, results for the caudate-putamen were similar to those for the 60 min group, while reduced ADC was a much better predictor of final ischemic injury in cortical regions than it was in both the 30 and 60 min groups. Thus, no single threshold of ADC reduction that was independent of the duration of ischemia was associated with irreversible injury.     

大鼠全脑缺血再灌注脑微血管损伤与修复动态变化的实验研究

目的 通过检测FⅧ相关抗原(von Willebrand factor,vWF)和层粘蛋白(laminin)在大鼠全脑缺血再灌注后脑微血管的表达,以研究脑缺血再灌注过程中微血管的损伤与修复。方法 将大鼠随机分为假手术对照组和缺血再灌注(IR)组,两组又各分为再灌注1、3、6、12、24、48、72h组,动物模型采用全脑缺血模型中的三血管阻塞法建立,用免疫组化法检测脑缺血再灌注不同时间vWF和Laminin的表达规律。结果 假手术各组vWF和Laminin均成强阳性表达,脑缺血再灌注组各时间点表达均低于假手术组,缺血再灌注1h就出现表达降低,以后逐渐下降,24～48h表达达最低值,72h表达又开始上升。结论 大鼠全脑缺血再灌注病理过程中,再灌注1h就出现了脑微血管的损伤,48～72h出现了血管的修复。     

Glucose-associated alterations in ischemic brain metabolism of neonatal piglets.

BACKGROUND AND PURPOSE: During global brain ischemia or hypoxia-ischemia in adults, hyperglycemia is deleterious to the brain. In contrast, similar adverse effects have not been found in neonatal animals. This investigation examined neonatal piglets to determine if there were specific alterations of ischemic brain metabolism associated with different systemic glucose concentrations and to potentially clarify the effects of hyperglycemia during ischemia in neonates. METHODS: Two groups of animals (n = 12 in each group) were studied during partial ischemia to compare the effects of hyperglycemia (plasma glucose concentration, 258 +/- 97 mg% [mean +/- SD]) with modest hypoglycemia (plasma glucose concentration, 62 +/- 23 mg%). A broad spectrum of cerebral blood flow reduction was achieved by combining inflation of a cervical pressure cuff with varying degrees of hemorrhagic hypotension. High-energy phosphorylated metabolites, intracellular pH, and cerebral blood flow were simultaneously measured using a magnetic resonance spectroscopic technique. Brain metabolic variables (beta-ATP, inorganic phosphorus, phosphocreatine, intracellular pH) were plotted as a function of blood flow reduction during partial ischemia for each group. RESULTS: During ischemia values of cerebral blood flow were comparably distributed between groups and ranged from 15% to 110% of those of control. At a given reduction of cerebral blood flow, hyperglycemic piglets maintained a higher concentration of beta-ATP (p = 0.011) and had a smaller increase in inorganic phosphorus (p less than 0.001). At cerebral blood flow less than 50% of control, the intracellular pH of piglets with modest hypoglycemia during partial ischemia was never reduced to less than 6.46, whereas intracellular pH fell as low as 5.97 for hyperglycemic animals. CONCLUSIONS: ATP preservation may account for the differing effects of glucose during ischemia in neonates compared with adults, provided that the accentuated brain acidosis is not deleterious to neonatal brain tissue.     

The effects of citicoline and lamotrigine alone and in combination following permanent middle cerebral artery occlusion in rats

The neuroprotective efficacies of citicoline and lamotrigine, alone and in combination, were investigated in experimental permanent focal ischemia. Seven groups of adult male rats underwent focal cerebral ischemia and were given the following treatments: placebo (P), low and high doses of citicoline (C250 and C500, 250 and 500 mg/kg/day i.p., respectively), low and high doses of lamotrigine (L50 and L100, 50 and 100 mg/kg/day p.o., respectively), and combination regimes of both drugs in low (C250 + L50) and high doses (C500 + L100). Citicoline, but not lamotrigine, exerted neuroprotective efficacy during this acute ischemic stroke model. The citicoline and lamotrigine combination did not provide a significant additive neuroprotective effect.     

不同氨基酸受体拮抗剂对缺血纹体CCK—8释放的影响

目的：研究不同兴奋性氨基酸受体拮抗剂（ＭＫ８０１，Ｓｐｅｒｍｉｎｅ，ＤＮＱＸ）对大鼠脑缺血时纹体缩胆囊肽－８（ＣＣＫ－８）释放的影响。方法：用微透析和ＲＩＡ法测定半球缺血时纹体ＣＣＫ－８的释放。结果：脑缺血时纹体ＣＣＫ－８释放明显增高，缺血前分别给予三种拮抗剂，都明显地降低缺血时纹体ＣＣＫ－８的不正常释放。结论：表明脑缺血时的ＣＣＫ－８和兴奋性氨基酸（ＥＡＡ）之间有协同的相互作用，抑制ＣＣＫ－８释放增高，可能是兴奋性氨基酸受体拮抗剂保护缺血大脑的机制之一。     

Global cerebral ischemia and intracellular pH during hyperglycemia and hypoglycemia in cats

In 27 cats treated to vary arterial serum glucose concentrations, we measured cerebral high-energy phosphate metabolite concentration and intracellular pH using in vivo phosphorus-31 nuclear magnetic resonance spectroscopy during transient global cerebral ischemia and reperfusion. Hypoglycemia was induced with 4 units/kg i.v. insulin in six cats before ischemia; hyperglycemia was induced with 1.5 g/kg i.v. glucose in six cats before and in six cats during ischemia. Nine untreated cats subjected to ischemia without manipulation of blood glucose concentration served as controls. During ischemia, intracellular pH fell to similar levels in the control and both hyperglycemic groups. During reperfusion, the hyperglycemic before ischemia group initially exhibited a severe further decline in intracellular pH (p less than 0.003); this further decline was not observed in the control or the hyperglycemic during ischemia groups. Intracellular acidosis was attenuated both during ischemia and early after reperfusion in the hypoglycemic before ischemia group. In all groups, cerebral high-energy phosphate metabolite concentrations were depleted during ischemia and then recovered to the same degree during reperfusion. Our data suggest that brain glucose stores before ischemia determine the severity and time course of intracellular acidosis during ischemia and reperfusion.     

Neuroprotective effects of lamotrigine in global ischemia in gerbils. A histological, in vivo microdialysis and behavioral study

A sudden surge in the release of glutamate is currently believed to be an important initiating step in neuronal damage due to an ischemic insult. In this experiment, we tested the efficacy of neuroprotection with lamotrigine, a novel antiepileptic drug that blocks voltage gated sodium channels and inhibits the ischemia-induced release of glutamate in the gerbil forebrain model of cerebral ischemia. The medication was administered 30 min before and 30 min after the insult in two groups of animals. Histological assessment of neuronal damage was evaluated at 7 and 28 days after the ischemic insult. Animals evaluated at 28 days also underwent behavioral testing. Microdialysis was used in the same model to study the response of ischemia-induced glutamate in saline treated controls versus animals treated with lamotrigine 20 min before the insult. There was highly significant neuronal protection in animals who were treated with lamotrigine either before or after the insult. Protection was seen both at 7 and 28 days after the insult. Behavioral testing also showed significantly better recovery in both sets of animals in comparison to the saline-treated group. Microdialysis confirmed a significant attenuation of the ischemia-induced glutamate surge when compared to the saline-treated animals. Our morphological, behavioral and microdialysis experiments show that lamotrigine offers significant neuroprotection from the effects of transient forebrain ischemia in gerbils. Neuroprotection with post-ischemic therapy probably depends on preserving the capacity of the sodium/calcium exchanger to reduce intracellular calcium concentrations or persistent `toxicity' of glutamate in the reperfusion period on the already `primed' injured neurons. These concepts need further study.