大鼠全脑缺血模型的脑电图验证

目的 :用脑电图验证四血管关闭全脑缺血模型。方法 :选取 30只Wistar大鼠 ,按pulsinelli方法制成全脑缺血模型 ,以脑电图出现直线波作为全脑完全缺血指标 ,分别与正常鼠、椎动脉关闭鼠、颈动脉关闭鼠脑电图比较 ,并与正常鼠比较全脑缺血后脑组织病理学改变。结果 :单纯颈动脉或椎动脉关闭鼠脑电图均不出现直线波 ,全脑缺血 5～ 10s后 ,2 5只鼠中的 2 3只出现直线波 ,模型成功率 92 % ,全脑缺血鼠与正常鼠比较 ,脑组织病理学无差异。结论 :脑短暂缺血不会造成脑组织的明显损害 ,以脑电图出现直线波作为全脑完全缺血的指标来验证全脑缺血模型的方法简单、可靠、易行 ,有实际应用价值     

亚低温对大鼠全脑缺血再灌注损伤后海马CA1区c-Jun蛋白表达的影响

目的研究亚低温对大鼠全脑缺血再灌注损伤后海马CA1区神经元的保护作用,并探讨其可能的机制。方法采用四血管阻断法建立大鼠全脑缺血模型。SD大鼠,随机分为假手术组(SH组)、常温组(IR组)和亚低温组(HIR组)。各组在全脑缺血15min后分别再灌注6h、12h、1d、3d,采用苏木素-伊红(HE)染色观察各时间点海马CA1区细胞形态学变化和TUNEL法检测海马CA1区神经元凋亡,免疫印迹检测c-Jun蛋白表达。结果(1)HE染色结果 IR组和HIR组于全脑缺血再灌注后6h,HE染色未见明显改变,IR组缺血再灌注1d时CA1区出现严重改变,3d时损伤最严重,出现细胞数目减少,细胞胞体缩小、胞核固缩深染,损伤严重,排列紊乱,核膜不清,核仁消失。而HIR组海马存活的锥体细胞数较之IR组12h、1d、3d时间点均明显增加(P<0.05)。(2)TUNEL标记IR组于缺血再灌注后6h在海马CA1区阳性细胞开始增多,缺血再灌注1 d时阳性细胞数最多。而HIR组各时间点阳性细胞数均较IR组明显减少(P<0.01)。(3)免疫印迹结果全脑缺血再灌注后6h c-Jun蛋白在IR组海马CA1区表达开始增加,12h达高峰,持续到3d;HIR组在各时间点的表达均弱于IR组(P<0.01)。结论亚低温通过减少海马CA1区c-Jun的表达,抑制海马CA1区神经元的凋亡,可能是亚低温脑保护作用的机制之一。     

全脑缺血大鼠血液流变学变化特征的实验研究

目的：观察大鼠全脑缺血后血液流变学的动态变化。方法：采用4-VO大鼠急性全脑缺血模型,于4-VO后2d、4d、7d、14d和28d对大鼠血液流变学指标、脑组织含水量进行检测并在光镜下观察细胞形态学的变化。结果：大鼠全脑缺血再灌注后血液流变学指标、脑组织含水量2d时即增高,至7d时达到高峰,14d时逐渐恢复,28d时恢复至假手术组水平。再灌注后2d、4d、7d与假手术组比较有显著差异(P<0．05)。结论：大鼠全脑缺血再灌注后血液流变学指标、脑组织含水量随着再灌注时间的延长而增高,7d时达到高峰。     

一氧化氮在脑缺血再灌流神经损伤中作用的实验研究

采用改良的Ｇｒｉｅｓｓ法，测定了脑缺血再灌流大鼠血清和脑组织中一氧化氮（ＮＯ）代谢产物ＮＯｘ（ＮＯ２＋ＮＯ３）的含量。结果表明，在脑缺血再灌流过程中实验大鼠血清和脑组织中ＮＯｘ含量的变化表现出独特的双峰现象，其第二高峰的出现时间与迟发性神经元损伤的发生相吻合。这提示，ＮＯ在脑缺血再灌流神经损伤中可能具有重要作用。     

亚低温对大鼠脑缺血再灌注损伤的保护研究

目的观察亚低温对大鼠全脑缺血再灌注后海马CAI区神经元凋亡的影响,探讨亚低温对缺血再灌注脑损伤的保护作用。方法SD大鼠30只随机分为对照组（n=10）,常温缺血组（n=10）,亚低温组（n=10）,采用改良的Pulsinelli-Brierley4血管法建立全脑缺血再灌注动物模型,缺血30min后再灌注72h,尼氏体染色观察海马区存活锥体细胞数,TUNEL法检测缺血后海马CAI区神经元凋亡情况,电镜下观察神经细胞形态学改变。结果与对照组比较,常温缺血组的海马CAI区存活的锥体细胞数目减少（P〈0.01）;与常温缺血组比较,亚低温组海马CAI存活的锥体细胞数目明显增多（P〈0.01）。对照组、亚低温组的海马CAI区神经元凋亡数目和凋亡指数明显低于常温缺血组。在电镜下观察亚低温能明显减轻缺血后脑组织病理形态学的损害程度。结论亚低温可以抑制脑缺血再灌注后的神经细胞凋亡,对神经细胞有保护作用。     

Regional distribution of selective neuronal loss and microglial activation across the MCA territory after transient focal ischemia: quantitative versus semiquantitative systematic immunohistochemical assessment

Histopathologic assessment in transient middle cerebral artery occlusion (MCAo) rodent models generally lacks comprehensiveness and exposes to interobserver bias. Here we compared a novel quantitative assessment of regional infarction, selective neuronal loss (SNL) and microglial activation (MA) across the MCA territory to a previously published semiquantitative visual protocol. NeuN and OX42 immunohistochemistry was applied after either 15 or 45 minutes distal MCAo to maximize SNL and infarction, respectively. Survival times varied from 28 to 60 days to cover potential biases such as delayed tissue shrinkage. Damage was assessed using a template of 44 cytoarchitectonic regions of interest (ROIs) mapped onto a subset of digitized coronal sections spanning the MCA territory. For each ROI were obtained a semiquantitative visually determined index of histopathologic changes (method 1), and lpsilateral/contralesional ratios of remaining neurons and activated microglia cell counts (method 2). There was excellent agreement between the two methods for 28-day survival for both MCAo durations, whereas method 2 more sensitively detected subtle SNL and MA at 45 days and 60 days after 15-minute MCAo. Thus the visual method is accurate for usual degrees of ischemic damage, but absolute cell quantification is superior to detect subtle changes and should therefore be preferred in brief MCAo models, although requires optimal staining quality.     

Selective neuronal vulnerability following transient cerebral ischemia in the gerbil: distribution and time course

An important feature of ischemic brain damage is the selective vulnerability of specific neuronal populations. We studied the distribution and time course of neuronal damage following transient cerebral ischemia in the gerbil, using light microscopy and 45Ca autoradiography. Following 5 min of ischemia, selective neuronal damage determined by abnormal 45Ca accumulation was recognized only in the hippocampal CA1 subfield and part of the inferior colliculus. Ischemia for 10 to 15 min caused extensive neuronal injury in the 3rd and 5th layers of neocortex, the striatum, the septum, the whole hippocampus, the thalamus, the medial geniculate body, the substantia nigra, and the inferior colliculus. Progression of the damage was rapid in the medial geniculate body and the inferior colliculus, moderate in the neocortex, striatum, septum, thalamus, and the substantia nigra, and was delayed in the hippocampal CA1 sector. However, the delayed damage of the hippocampus occurred earlier when the ischemia period was prolonged. Histological observation revealed neuronal loss in the identical sites of the 45Ca accumulation. This study revealed that the distribution and time course of selective neuronal damage by ischemia proceeded with different order of susceptibility and different speed of progression.     

The development of a new mouse model of global ischemia: focus on the relationships between ischemia duration, anesthesia, cerebral vasculature, and neuronal injury following global ischemia in mice

A new model for mouse global ischemia is presented, and the relationship of ischemia duration, cerebral vasculature, and ischemic neuronal injury has been determined. CD-1 mice anesthetized by chloral hydrate were subjected to global ischemia by bilateral common carotid artery occlusion under controlled ventilation for 3, 5, and 10 min. After evaluating the patency of the posterior communicating artery (PcomA) as hypoplastic or normoplastic, neuronal injury was independently determined in the striatum, cortex, and hippocampus in each hemisphere. Ischemic injury was strongly correlated with not only ischemia duration, but also with the patency of the PcomAs. Furthermore, neuronal injury developed in a delayed fashion after 3-min ischemia, while it was maximized at 24 h after 10-min ischemia. Physiological studies showed the induction of slight hypotension as compared with inhalation anesthesia, and improvement of blood gas data relative to spontaneous respiration. These data demonstrate the usefulness of this method to induce selective vulnerability and delayed neuronal cell death in mice, and to provide a useful model to study the detailed mechanism of global ischemia using transgenic or knockout mutant mice.     

The role of postischemic recirculation in the development of ischemic neuronal injury following complete cerebral ischemia

Summary The neuronal response to complete cerebral ischemia (CCI) of 5–15 min duration was evaluated at the light and electron microscopic level subsequent to postischemic recirculation periods of up to 60 min. Following postischemic reperfusion, the homogeneous neuronal changes characteristic of permanent CCI were modified into a heterogeneous pattern of selectively vulnerable neuronal responses. Four basic types of neuronal injury were represented within this heterogeneous neuronal population. The Type I neuronal response was most numerous and consisted of chromatin clumping, nucleolar condensation and a breakdown of polysomes. This response may represent a reversal of some of the neuronal changes observed after permanent CCI. In addition to the above changes, Type II neurons contained swollen mitochondria and Golgi saccules which appeared as microvacuoles under the light microscope. Type III neurons displayed varying degrees of neuronal shrinkage and numerous swollen mitochondria. Type IV neurons were markedly shrunken and electron-dense with few identifiable subcellular structures. The distribution of Type I neurons was random but the other neuronal responses occurred in selectively vulnerable brain regions. The number of Type II, III, and IV neurons increased with extended insult durations but were unaffected by the length of recirculation. Ten minutes of CCI represented the threshold for a significant increase in the number of severely altered neurons. These findings suggest that considerable neuronal injury may be present after 10–15 min of CCI, and the lack of a recirculation period following CCI appears to afford the brain parenchyma an extensive degree of structural protection.Supported by PHS Grant NS-12587     

Complete cerebral ischemia

Summary Neuronal, astrocytic, and oligodendrocytic elements in several brain loci of the cat were examined at the light and electron microscopic level immediately after periods of complete cerebral ischemia (CCI) uncomplicated by post-ischemic recirculation. Such CCI episodes ranged from 1.5–25 min duration and were methodically produced in a cat model employing rigorous physiological controls. Subsequent to these CCI insults, morphological alterations occurred in a homogeneous manner within each cell type of all loci examined; however, variation in the temporal onset and magnitude of alterations among the various cell types was observed. With brief ischemic insults all cell nuclei demonstrated pronounced nuclear alterations, while their cytoplasmic organelles displayed minimal change. Chromatin clumping and nucleolar condensation were observed in both neurons and glia subsequent to 1.5–5 min of CCI, respectively. With increasing durations of CCI such changes were more dramatic and conspicuous alterations of the cytoplasmic organelles were observed. On the basis of extensive morphological analyses the present study illustrates that nuclear alterations are the first to occur subsequent to CCI. The homogeneity of neuronal involvement seen subsequent to CCI uncomplicated by post-ischemic recirculation is inconsistent with the selective vulnerability purported to occur by others. The significance of this inconsistency remains to be assessed; yet, the suggestion is advanced that post-ischemic recirculation may be a factor in the genesis of such vulnerability.Supported by PHS grant NS-12587     

基于微导管技术选择性动脉内低温对大鼠局灶性脑缺血基质金属蛋白酶-9表达影响

目的探讨基于微导管技术的选择性动脉内低温对大鼠急性脑缺血-再灌注损伤后基质金属蛋白酶-9(MMP-9)表达的影响。方法应用微导管堵塞SD大鼠大脑中动脉(MCAO)2h,建立急性可逆性脑缺血动物模型。动物随机分为4组(12只/组):1非干预对照组,MCAO后,再灌注48h;2低温生理盐水全身灌注组,MCAO后即刻通过股动脉灌注0℃0.9%生理盐水2.5ml;3低温生理盐水局部灌注组,MCAO后即刻通过微导管向脑缺血区灌注0℃0.9%生理盐水2.5ml;4常温生理盐水局部灌注组,MCAO后即刻通过微导管向脑缺血区灌注37℃0.9%生理盐水2.5ml。所有动物都进行运动、神经功能评分,计算脑梗死体积、脑水肿程度,应用免疫组化定位定量脑缺血区MMP-9的表达水平。结果和非干预对照组比较,通过微导管选择性灌注0℃生理盐水能对缺血脑组织区域快速诱导低温(皮质脑温由灌注前37.2±0.2℃降低至30.5±0.4℃,纹状体温度由37.8±0.1℃降至30.8±0.4℃,P0.01),显著改善实验动物的神经、运动功能(P0.01),明显缩小脑梗死体积(缩小约67%,P0.01)、减轻脑水肿程度(约70%,P0.01),同时改组动物缺血区MMP-9阳性表达的数目显著减少(P0.05)。而通过微导管灌注常温生理盐水及通过股动脉全身灌注低温生理盐水未显示出明显的脑保护作用,对MMP-9的表达也没有明显影响。结论通过微导管灌注低温生理盐水对急性缺血-再灌注损伤具有显著保护作用,其机制与抑制脑缺血区MMP-9表达有关。     

Mild hypothermia on anoxic depolarization and subsequent cortical injury following transient ischemia

Abstract

Anoxic depolarization (AD) is one of the major physiological characteristics in the ischemic core. The effect of mild hypothermia on the appearance of AD and subsequent brain injury following profound ischemia is studied to evaluate the protective mechanism of hypothermia against severe ischemia. Sprague-Dawley rats were subjected to transient ischemia by hypotension (50-20 mmHg) and bilateral carotid artery occlusion (BCA-O) for 20 min in normothermia and 30 min in hypothermia. The temperature of body and temporal muscles was maintained at 37.5°C and 36.5°C in normothermia and 33.0°C and 31.0°C in hypothermia, respectively. Recording of the DC potential shift and electrocorticogram and monitoring of the cortical blood flow (CoBF) with a laser Doppler flowmeter were done epidurally on the right parietal cortex. The right parietal cortex pathology was examined 24 h after ischemia in normothermia and after 30 days in hypothermia. AD appeared in all seven normothermic rats with a fall in the CoBF to 9%-10% of the control flow. However, in spite of CoBF reduction to 8%-9% of the control flow, it did not appear in five hypothermic rats. Intra-ischemic CoBF was not statistically different between these two groups. AD appeared with the CoBF decreasing to 4%-5% of the control flow in seven hypothermic rats. Intra-ischemic CoBF in hypothermic rats exhibiting AD was significantly lower than the other two groups. The interval between BCA-O and the appearance of AD in hypothermic rats was 5.1 ± 0.3 min (mean ± SE), which was significantly longer than the 2.2 ± 0.5 min observed in normothermia (p < 0.0005). Of seven normothermic rats exhibiting AD, two died within 24 h and four revealed massive neuronal injury. Of seven hypothermic rats with AD, four died between day 2 and day 13, and one revealed diffuse cerebral infarction. However, no severe ischemic injury or ischemic death was observed in all five hypothermic rats without AD. The incidence of severe neuronal injury or ischemic death was significantly lower in hypothermic rats without AD compared with normothermic rats with AD (p < 0.02) or hypothermic rats with AD (p < 0.05). Although mild hypothermia delays AD, it is suggested that raising the cerebral blood flow threshold for AD appearance has a key role in the hypothermic protection of a severely ischemic area such as the ischemic core. [Neurol Res 1999; 21: 670-676]     

Proteasome alteration and delayed neuronal death in hippocampal CA1 and dentate gyrus regions following transient cerebral ischemia

BACKGROUND： Proteasome dysfunction has been reported to induce abnormal protein aggregation and cell death. OBJECTIVE： To investigate the effect of proteasome changes on delayed neuronal death in CA1 and dentate gyrus （DG） regions of the rat hippocampus following transient cerebral ischemia. DESIGN, TIME AND SETTING： A randomized, controlled animal experiment. The study was performed at the Department of Biochemistry and Molecular Biology, Norman Bethune Medical College of Jilin University, from September 2006 to May 2008. MATERIALS： Rabbit anti-19S S10B polyclonal antibody was purchased from Bioreagents, USA; propidium iodide and fluorescently-labeled goat anti-rabbit IgG were purchased from Jackson Immunoresearch, USA; hematoxylin and eosin staining solution was purchased from Sigma, USA; LSM 510 confocal microscope was purchased from Zeiss, Germany. METHODS： A total of 40 healthy Wistar rats, male, 4 months old, were randomly divided into sham surgery group （n = 8） and model group （n = 32）. Ischemic models were established in the model group by transient clamping of the bilateral carotid arteries and decreased blood pressure. After 20 minutes of global ischemia, the clamp was removed to allow blood flow for 30 minutes, 4, 24 and 72 hours, respectively, with 8 rats at each time point. The bilateral carotid arteries were not ligated in the sham surgery group. MAIN OUTCOME MEASURES： Neuronal death in the CA1 and DG regions was observed by hematoxylin-eosin staining. Proteasome expression in CA1 and DG region neurons was detected by immunohistochemistry. RESULTS： Hematoxylin-eosin staining showed neuronal death in the CA1 region alone at 72 hours of reperfusion following ischemia. In comparison to the sham surgery group, a significant decrease in proteasome expression was observed, by immunohistochemistry, in the CA1 and DG regions in the model group, following 30 minutes, 4, 24, and 72 hours of reperfusion （P 〈 0.01）. After 72 hours of reperfusion following ischemia, proteasome expression had almost completely disappeared in the CA1 region. In contrast, neurons of the DG region showed minimized proteasome expression at 24 hours, with a slight increase at 72 hours （P 〈 0.01）. CONCLUSION： The alteration of proteasome following ischemia/reperfusion in the neurons of hippocampal CA1 and DG regions reduces the ability of cells to degrade abnormal protein, which may be an important factor resulting in delayed neuronal death following transient cerebral ischemia.     

Axon guidance factor netrin-1 and its receptors regulate angiogenesis after cerebral ischemia

Neurogenesis and angiogenesis play important roles in functional recovery after ischemic stroke. When cerebral ischemia occurs, axon regeneration can compensate for the loss of apoptotic neurons in the ischemic area. The formation of new blood vessels ameliorates the local decrease in blood supply, enhancing the supply of oxygen and nutrients to newly-formed neurons. New blood vessels also act as a scaffold for the migration of neuroblasts to the infarct area after ischemic stroke. In light of this, researchers have been actively searching for methods to treat cerebral infarction. Netrins were first identified as a family of proteins that mediate axon guidance and direct axon migration during embryogenesis. Later studies have revealed other functions of this protein family. In this review, we focus on netrin-1, which has been shown to be involved in axon migration and angiogenesis, which are required for recovery after cerebral ischemia. Thus, therapies targeting netrin-1 may be useful for the treatment of ischemic stroke.     

Ultrastructural studies of cerebral vascular spasm after cardiac arrest-related global cerebral ischemia in rats

The present investigation was undertaken to study the ultrastructural morphology of brain blood vessels during vasospasm following total cerebral ischemia. Global cerebral ischemia was produced in rats by compression of the cardiac vessel bundle (i.e., cardiac arrest) using a metal hook that was introduced into the mediastinum. Ischemia lasted for 10 min with blood recirculation for 6, 12 and 24 h. Rat brains were perfusion-fixed and regions from the cerebral cortex and associated leptomeningeal vessels were evaluated by scanning and transmission electron microscopy. We noted three general vasoconstrictive responses in vessels of various sizes including veins and arteries. These alterations related to the smooth muscle cell arrangement associated with each constricted vessel including a circumferential, and longitudinal arrangement, or a combination of both types. Other features in the three types of vasoconstricted vessels included thickening of the vessel basement membranes with increased endothelial microfilaments and vesicular profiles. Our studies present evidence that ischemia of 10-min duration with blood reflow for 6, 12 and 24 h produces profound and variable vasospastic changes in some but not all vessels. These vascular alterations are thought to be caused in part by vasoactive substances released both by endothelial and blood cells and by perivascular cellular elements in response to the ischemic episode.     

小檗碱对小鼠全脑缺血后神经元凋亡的影响

目的观察小檗碱能否对小鼠全脑缺血后细胞凋亡产生抑制作用.方法利用改良的Pulsinelli-Brierley4血管闭塞法制成小鼠全脑缺血再灌注动物模型.TUNEL法原位检测特征性DNA片段.琼脂糖凝胶电泳技术检测DNA梯度带.结果小檗碱组与再灌流各时间段缺血组相比,海马CA1区TUNEL阳性细胞数明显减少(P<0.01).缺血组再灌注24h、48h可见典型的DNA梯度带,分别在180、360、540bp等处.小檗碱组未见特征性DNA梯度带.结论小檗碱可以减少小鼠全脑缺血后海马CA1区细胞凋亡的发生.     

吡拉西坦抗短暂性局灶性脑缺血作用观察

目的 观察吡拉西坦的抗局灶性脑缺血作用。方法采用动脉腔内插线大鼠局灶性脑缺血模型及激光多普勒血流计测定半暗带脑血流、湿重-干重法测定缺血半球水含量、3％伊文氏蓝染色结合图像分析测定血脑屏障(BBB)的破坏、HE染色结合图像分析测定缺血后21h的梗死体积。结果100mg／kg体重吡拉西坦对半暗带脑血流无明显影响，200mg／kg体重吡拉西坦可明显升高再灌注期间半暗带脑血流；100mg／kg和200mg/kg体重的吡拉西坦均可明显降低局灶性脑缺血后缺血半球的水含量及BBB的损伤，缩小梗死体积。结论吡拉西坦具有明确的抗局灶性脑缺血作用，它可改善半暗带脑血流、减轻脑组织水肿和BBB的损伤、缩小梗死体积。     

一种C-Jun N-末端激酶肽抑制剂在沙土鼠全脑缺血中的保护作用

目的 为了进一步研究海马C1区域神经细胞活动中JNK的作用，我们评价了一种JNK抑制剂即D-JNKI1在沙土鼠一过性大脑缺血模型中对迟发性神经细胞死亡（DND）的作用。方法 55只沙土鼠随机分为11个组。5组沙土鼠先接受5min前脑缺血处理，再灌注3h后，通过立体定向方法。向每组沙土鼠右侧侧脑室内分别注入不同浓度的D-JNKI1（2μL PBS内加入0．00012，0．0012，0．012，0．12，1．2μmol／L D-JNKI1，每组n=5）。对照组（n=5）：沙土鼠先接受5min前脑缺血处理，再灌注3h后，通过立体定向方法方法向右侧侧脑室内仅注入PBS2μL。腹腔内注射组（n=5）沙土鼠；先接受5min前脑缺血处理，再灌注3h后，1．2μmol／L D-JNKI1溶于0．5mL PBS腹腔内注射。假手术组（n=5）；沙土鼠仅暴露双侧颈总动脉，未夹闭。预处理组（共3组，n=15）：先将0．0012μmol／L D-JNKI1，0．00012μmol／L D-JNKI1溶于2μL PBS，分别注入两组沙土鼠的右侧侧脑室内，另外一组沙土鼠的右侧侧脑室内仅仅注入PBS2μL，30min后三组均夹闭双侧颈总动脉2min，48h后再次接受双侧颈总动脉夹闭5min。所有沙土鼠从接受夹闭5min双侧颈总动脉后4d处死，作冰冻切片和Niss1染色。结果 缺血再灌注3h后用D-JNKI-1治疗，有神经保护作用，最好的神经保护效应浓度为0．0012μmol／L。D-JNKI-1预处理加强了2min预处理所诱导的缺血耐受效应。结论D-JNKI1在沙土鼠全脑缺血模型中对海马CA1区域的迟发性神经细胞死亡有潜在的神经保护作用。     

Non-additive effects of delayed connexin hemichannel blockade and hypothermia after cerebral ischemia in near-term fetal sheep

Hypothermia is partially neuroprotective after neonatal hypoxic-ischemic encephalopathy. Blockade of connexin hemichannels can improve recovery of brain activity and cell survival after ischemia in near-term fetal sheep. In this study, we investigated whether combining delayed hypothermia with connexin hemichannel blockade with intracerebroventricular infusion of a mimetic peptide can further improve outcomes after cerebral ischemia. Fetal sheep (0.85 gestation) received 30 minutes of cerebral ischemia followed by a 3-hour recovery period before treatment was started. Fetuses were randomized to one of the following treatment groups: normothermia (n=8), hypothermia for 3 days (n=8), connexin hemichannel blockade (50 μmol/L intracerebroventricular over 1 hour followed by 50 μmol/L over 24 hours, n=8) or hypothermia plus hemichannel blockade (n=7). After 7 days recovery, hypothermia was associated with reduced seizure burden, improved electroencephalographic (EEG) power, and a significant increase in neuronal and oligodendrocyte survival and reduced induction of Iba1-positive microglia. In contrast, although hemichannel blockade reduced seizure burden, there was no effect on EEG power or histology (P<0.05). There was no further improvement in outcomes with combined hypothermia plus hemichannel blockade. In conclusion, these data show that there is no additive neuroprotection with combined hypothermia and hemichannel blockade after cerebral ischemia in near-term fetal sheep.     

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.