神经节苷脂对大鼠脑缺血再灌注损伤的脑保护作用

目的探讨神经节苷脂对大鼠脑缺血再灌注损伤的脑保护作用。方法采用线栓法制作缺血再灌注大鼠模型,分别用神经节苷脂(治疗组)和生理盐水(对照组)腹腔注射。观察两组大鼠缺血90min、缺血90min再灌注24h的脑梗死面积、神经功能缺损程度、细胞凋亡数、细胞凋亡率。结果治疗组大鼠于相同时间点脑梗死面积较对照组明显减小,仅表现轻度的神经功能缺损,且神经细胞的凋亡数较对照组显著减少(均P<0.01)。结论神经节苷脂能明显减小大鼠实验性脑缺血的脑梗死面积,减轻脑缺血再灌注后神经功能缺损程度,显著减轻缺血区神经元损害,具有显著的脑保护作用。     

The effect of the NMDA receptor antagonist MK-801 on cerebral blood flow and infarct volume in experimental focal stroke

The non-competitive N-methyl-D-aspartate receptor/channel antagonist dizocilipine maleate (MK-801) has been reported to reduce infarct volume in a variety of focal stroke models. We examined the effect of MK-801 on infarct volume and cerebral blood flow in temporary and permanent focal ischemia in rats. In Wistar rats exposed to permanent right common carotid artery and 2 h of transient right middle cerebral and left common carotid artery occlusion followed by 22 h of reperfusion, MK-801 reduced infarct volume by 73% (P less than 0.05) and significantly increased cerebral blood flow to the ischemic core throughout the 2-h period of ischemia. In spontaneously hypertensive rats (SHRs) exposed to permanent right common carotid artery occlusion and 2 h of transient right middle cerebral artery occlusion followed by 22 h of reperfusion, MK-801 decreased infarct volume by 13% (P greater than 0.05) and increased cerebral blood flow to the penumbral region. In SHRs subjected to permanent right common carotid and middle cerebral artery occlusion MK-801 reduced infarct volume by 18% at 3 h (P greater than 0.05), by 25% at 6 h (P less than 0.01) and by 18% at 24 h (P less than 0.05). MK-801-treated SHRs had no difference in cerebral blood flow to the ischemic core, but increased cerebral blood flow to penumbral zones as compared with untreated SHRs. These results suggest that the protective effect of MK-801, at least in part, relates to improved cerebral blood flow.     

Mild hypothermia reduces infarct size resulting from temporary but not permanent focal ischemia in rats.

BACKGROUND AND PURPOSE: Mild hypothermia (32-35 degrees C) has been repeatedly shown in laboratory models to reduce damage resulting from global cerebral ischemic insults. Little information is available, however, regarding the protective potential of mild hypothermia against focal ischemia. We designed the present study to determine whether mild hypothermia influences outcome from either temporary or permanent middle cerebral artery occlusion in the rat. METHODS: In experiment 1 (permanent occlusion), mechanically ventilated, halothane-anesthetized spontaneously hypertensive rats underwent permanent ligation of the middle cerebral artery. Pericranial temperature was maintained at either 37 degrees C (n = 11) or 33 degrees C (n = 11) during the first 2 hours of occlusion. In experiment 2 (temporary occlusion), the vessel was occluded for 1 hour only. Pericranial temperature was controlled at either 37 degrees C (n = 12) or 33 degrees C (n = 14) during ischemia and for 1 hour after reperfusion. In both experiments, the rats were allowed to recover, with neurological function scored at 24 and 96 hours after onset of ischemia. Cerebral infarct volume (as determined by nitro blue tetrazolium staining) was planimetrically evaluated 96 hours after onset of ischemia. RESULTS: No difference in infarct volume was observed between groups undergoing permanent occlusion (177 +/- 53 mm3 for 37 degrees C rats, 167 +/- 71 mm3 for 33 degrees C rats [mean +/- SD]). Although neurologic function correlated with infarct volume at 96 hours (all animals in experiment 1 combined; p less than 0.01), we were unable to demonstrate an intergroup difference in function. In animals undergoing temporary occlusion, mean +/- SD infarct volume was 48% less in the hypothermic group (89 +/- 54 mm3 for 37 degrees C, 46 +/- 31 mm3 for 33 degrees C; p less than 0.03). Neurological function again correlated with infarct size (p less than 0.02), but improvement in function approached significance for the hypothermic group (p less than 0.06) at 24 hours after reperfusion only. CONCLUSIONS: Benefits from mild hypothermia may be obtained under conditions of temporary but not permanent middle cerebral artery occlusion in the rat.     

Interrupting reperfusion as a stroke therapy: ischemic postconditioning reduces infarct size after focal ischemia in rats.

Cerebral ischemic preconditioning protects against stroke, but is clinically feasible only when the occurrence of stroke is predictable. Reperfusion plays a critical role in cerebral injury after stroke; we tested the hypothesis that interrupting reperfusion lessens ischemic injury. We found for the first time that such postconditioning with a series of mechanical interruptions of reperfusion significantly reduces ischemic damage. Focal ischemia was generated by permanent distal middle cerebral artery (MCA) occlusion plus transient bilateral common carotid artery (CCA) occlusion. After 30 secs of CCA reperfusion, ischemic postconditioning was performed by occluding CCAs for 10 secs, and then allowing for another two cycles of 30 secs of reperfusion and 10 secs of CCA occlusion. Infarct size was measured 2 days later. Cerebral blood flow (CBF) was measured in animals subjected to permanent MCA occlusion plus 15 mins of bilateral CCA occlusion, which demonstrates that postconditioning disturbed the early hyperemia immediately after reperfusion. Postconditioning dose dependently reduced infarct size in animals subjected to permanent MCA occlusion combined with 15, 30, and 60 mins of bilateral CCA occlusion, by reducing infarct size approximately 80%, 51%, and 17%, respectively. In addition, postconditioning blocked terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end labeling-positive staining, a marker of apoptosis, in the penumbra 2 days after stroke. Furthermore, in situ superoxide detection using hydroethidine suggested that postconditioning attenuated superoxide products during early reperfusion after stroke. In conclusion, postconditioning reduced infarct size, most plausibly by blocking apoptosis and free radical generation. With further study it may eventually be clinically applicable for stroke treatment.     

Characterizing the diffusion/perfusion mismatch in experimental focal cerebral ischemia

Diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) can rapidly detect lesions in acute ischemic stroke patients. The PWI volume is typically substantially larger than the DWI volume shortly after onset, that is, a diffusion/ perfusion mismatch. The aims of this study were to follow the evolution of the diffusion/ perfusion mismatch in permanent and 60- minute temporary focal experimental ischemia models in Sprague-Dawley rats using the intraluminal middle cerebral artery occlusion (MCAO) method. DWI and arterial spin-labeled PWI were performed at 30, 60, 90, 120, and 180 minutes after occlusion and lesion volumes (mm(3)) calculated At 24 hours after MCAO, and infarct volume was determined using triphenyltetrazolium chloride staining. In the permanent MCAO group, the lesion volume on the ADC maps was significantly smaller than that on the cerebral blood flow maps through the first 60 minutes after MCAO; but not after 90 minutes of occlusion. With 60 minutes of transient ischemia, the diffusion/perfusion mismatch was similar, but after reperfusion, the lesion volumes on ADC and cerebral blood flow maps became much smaller. There was a significant difference in 24- hour infarct volumes between the permanent and temporary occlusion groups.     

CD18-mediated neutrophil recruitment contributes to the pathogenesis of reperfused but not nonreperfused stroke

BACKGROUND AND PURPOSE: Neutrophil (PMN) recruitment mediated by increased expression of intercellular adhesion molecule-1 expression (ICAM-1, CD54) in the cerebral microvasculature contributes to the pathogenesis of tissue injury in stroke. However, studies using blocking antibodies against the common beta2-integrin subunit on the PMN, the counterligand for ICAM-1 (CD18), have demonstrated equivocal efficacy. The current study tested the hypothesis that mice deficient in CD18 would be protected in the setting of reperfused but not nonreperfused stroke. METHODS: Two groups of mice were studied, those whose PMNs could express CD18 (CD18 +/+) and those mice hypomorphic for the CD-18 gene (CD18 -/-). PMNs obtained from CD18 -/- or CD18 +/+ mice were fluorescently labeled and tested for binding to murine brain endothelial monolayers. Using a murine model of focal cerebral ischemia in which an occluding suture placed in the middle cerebral artery (MCA) is removed after 45 minutes (transient ischemia, reperfused stroke) or left in place (permanent ischemia, nonreperfused stroke), cerebral infarct volumes (% ipsilateral hemisphere by TTC staining), cerebral blood flow (CBF, % contralateral hemisphere by laser-Doppler flowmetry), and survival (%) were examined 24 hours after the initial ischemic event. Adoptive transfer studies used 111In-labeled PMNs (from either CD18 +/+ or CD18 -/- mice) to examine the relative accumulation of PMNs in the ischemic region. RESULTS: PMNs obtained from CD18 -/- mice exhibit reduced adhesivity (compared with CD18 +/+ PMNs) for both quiescent and cytokine-activated endothelial monolayers. CD18 -/- mice (n=14) subjected to transient focal cerebral ischemia demonstrated a 53% decrease in infarct volumes versus CD18 +/+ mice (n=26, P<0.05), improved penumbral CBF at 24 hours (1.8-fold, P=0.02), and a 3.7-fold decrease in mortality (P=0.02). However, when CD18 -/- mice (n=12) were subjected to permanent focal cerebral ischemia, no differences were noted in infarct volume, mortality, or CBF versus similarly treated CD18 +/+ mice (n=10). There was a greater accumulation of CD18 +/+ PMNs in the ischemic zone of CD18 +/+ animals than CD18 -/- animals subjected to reperfused stroke (82% increase, P=0.02), although there was no difference between groups when subjected to permanent MCA occlusion. CONCLUSIONS: Deficiency for the CD18 gene confers cerebral protection in a murine model of reperfused stroke, but this benefit does not extend to CD18-deficient animals subjected to permanent MCA occlusion. These data suggest that anti-PMN strategies should be targeted to reperfused stroke and may perhaps be used in conjunction with thrombolytic therapy that establishes reperfusion.     

Postischemic intracarotid treatment with TNK-tPA reduces infarct volume and improves neurological deficits in embolic stroke in the unanesthetized rat

BACKGROUND AND PURPOSE: To simulate human stroke, we developed a model of focal cerebral embolic ischemia in the unanesthetized rat. Using this model, we tested the hypothesis that intra-arterial administration of TNK-tPA, a fibrin specific second generation thrombolytic agent, is effective in reducing ischemic volume without increasing intra-cerebral hemorrhage. METHODS: Under anesthesia, a catheter was inserted to the origin of the MCA of male Wistar rats. Forty-five minutes after recovery from anesthesia, the MCA was occluded in the awake rat by a single fibrin rich clot placed via the catheter. TNK-tPA (1.5 mg/kg) was administered intraarterially via the catheter at either 2 h or 4 h after stroke. All rats were sacrificed at 48 h after ischemia. Neurological deficits, gross hemorrhage and ischemic lesion volume were measured. RESULTS: A clot was detected at the origin of the MCA 4 h after MCA occlusion in the awake rats (n=4). Rats (n=12) subjected to MCA occlusion showed immediate neurological deficits which persisted for 48 h of ischemia. Ischemic rats had a lesion volume of 38.2+/-3.8% and 25% of rats exhibited gross hemorrhage. Ischemic rats (n=10) treated with TNK-tPA at 2 h showed a significant (P<0.05) reduction of neurological deficits, body weight loss and infarct volume (22.8+/-2.1%) without an increase in gross hemorrhage (10%) compared with the non treated ischemic rats (25%). Although treatment with TNK-tPA of ischemic rats (n=12) at 4 h did not significantly (P=0.06) reduce infarct volume (28.6+/-3.0%), it also did not increase gross hemorrhage (25%) compared with the control group (25%). CONCLUSIONS: This study demonstrates that intraarterial administration of TNK-tPA at 2 h of ischemia in the unanesthesthetized rat is effective in reducing neurological deficits and ischemic lesion volume without increasing hemorrhagic transformation and that administration of TNK-tPA at 4 h of ischemia does not increase the incidence of hemorrhagic transformation.     

大鼠脑缺血再灌注半暗带β淀粉样前蛋白mRNA表达与梗死体积的关系

为了探讨大鼠局灶性脑缺血再灌注缺血半暗带β淀粉样前蛋白(APP)转录水平与缺血时间及梗死体积的相互关系，用插线法建立大鼠局灶性脑缺血再灌注模型，剥取缺血半暗带皮质组织，采用半定量逆转录－聚合酶链式反应（RT－PCR），测定永久性缺血48h和不同缺血时间再灌注48h后，APPmRNA水平的变化。结果显示，梗死体积随再灌注前缺血时间的延长而增大，皮质半暗带缺血30min再灌注48h APPmRNA表达升高；缺血60min和缺血120min再灌注48h APPmRNA升高明显；缺血180min再灌注48h和永久性缺血48h APPmRNA达到高峰。提示缺血半暗带APPmRNA的表达随再灌注前缺血时间延长而增加并与梗死体积有一定的相关性，早期再灌注可减少其表达。（（GFDA1））。     

Neuroprotective effect of a heat shock protein inducer, geranylgeranylacetone in permanent focal cerebral ischemia

Previous studies have strongly suggested that heat shock protein 70 (HSP70) has protective effects in ischemia/reperfusion in tissues such as brain, heart, and liver. This study was performed to assess the efficacy of the HSP70 inducer geranylgeranylacetone (GGA) in experiments involving permanent middle cerebral artery (MCA) occlusion. Male Balb/c mice were subjected to permanent MCA occlusion by direct occlusion through small craniectomy. Vehicle or GGA (200 or 1000 mg/kg) was injected intraperitoneally 1 h prior to the onset of ischemia. Infarct volumes were evaluated at 24 h of ischemia by using 2,3,5-triphenyltetrazolium chloride (TTC) staining. The effect of GGA on the induction of HSP70 was studied at 3 h after ischemia with fluorescence immunocytochemistry. The percentage of infarct volume in the control mice (n=10) was 23.0+/-4.0% (mean+/-SD) of the contralateral hemisphere, while those in the treated groups were 22.6+/-7.3% (200 mg/kg group; n=5, P>0.05) and 15.7+/-3.8% (1000 mg/kg group; n=5, P<0.05). Pretreatments with 1000 mg/kg of GGA enhanced the ischemia-related induction of HSP in the neurons and astrocytes in the boundary zone of infarct. The results demonstrate that GGA significantly reduces infarct volume due to permanent MCA occlusion when given 1 h prior to the induction of ischemia.     

Reperfusion increases neutrophils and leukotriene B4 receptor binding in rat focal ischemia.

BACKGROUND AND PURPOSE: Neutrophils are critically involved with ischemia and reperfusion injury in many tissues but have not been studied under conditions of reperfusion after focal cerebral ischemia. The present studies were conducted to confirm our previous observations quantifying neutrophils in rat permanent focal stroke using a myeloperoxidase activity assay and to extend them to transient ischemia with reperfusion. In addition, leukotriene B4 receptor binding in ischemic tissue was evaluated as a potential marker for inflammatory cell infiltration. METHODS: Histological, enzymatic, and receptor binding techniques were used to evaluate neutrophil infiltration and receptor binding in infarcted cortical tissue 24 hours after permanent middle cerebral artery occlusion (n = 25) or temporary occlusion for 80 (n = 12) or 160 (n = 22) minutes followed by reperfusion for 24 hours in spontaneously hypertensive rats. RESULTS: Sham surgery (n = 26) produced no changes in any parameter measured. After permanent middle cerebral artery occlusion, neutrophil accumulation was observed histologically, but the infiltration was moderate and typically within and adjacent to blood vessels bordering the infarcted cortex. After temporary middle cerebral artery occlusion with reperfusion, marked neutrophil infiltration was observed throughout the infarcted cortex. Myeloperoxidase activity was increased (p less than 0.05) after permanent occlusion and to a greater extent after temporary occlusion with reperfusion. Myeloperoxidase activity (units per gram wet weight) in ischemic cortex was increased over that in nonischemic (control) cortex 32.2-fold, 54.6-fold, and 92.1-fold for permanent occlusion and 80 and 160 minutes of temporary occlusion with reperfusion, respectively (p less than 0.05). Sham surgery produced no changes in myeloperoxidase activity. Leukotriene B4 receptor binding also was increased (p less than 0.05) after focal ischemia and paralleled the increases in myeloperoxidase activity. Ischemic cortex-specific receptor binding (femtomoles per milligram protein) was 3.87 +/- 0.63 in sham-operated rats and 4.57 +/- 0.98, 8.98 +/- 1.11, and 11.12 +/- 1.63 for rats subjected to permanent occlusion and 80 and 160 minutes of temporary occlusion with reperfusion, respectively (all p less than 0.05 different from sham-operated). Cortical myeloperoxidase activity was significantly correlated with the degree of cortical leukotriene B4 receptor binding (r = 0.66 and r = 0.79 in two different studies, p less than 0.01). CONCLUSION: These data indicate that neutrophils are involved in focal ischemia and that there is a dramatic accumulation of neutrophils in infarcted tissue during reperfusion that can be quantified using the myeloperoxidase activity assay. Leukotriene B4 receptor binding increases in infarcted tissue in a parallel manner, which suggests that the increased leukotriene B4 binding is to receptors located on the accumulating neutrophils.     

Therapeutic time window for YAG laser-induced reperfusion of thrombotic stroke in hypertensive rats

We examined the novel YAG laser-induced reperfusion method in the photothrombotic middle cerebral artery (MCA) occlusion model in spontaneously hypertensive rats. In the 1 h ischemia group, infarct volume was significantly reduced to 41.1 +/- 15.6 mm3 compared with 81.6 +/- 18.3 mm3 in the no-reperfusion group. There were no significant differences in infarct volume among 2 h or 3 h ischemia and no-reperfusion groups. Three of six rats in the 3 h ischemia group showed hemorrhagic infarction. Our present results showed that recirculation must be instituted within 2 h of MCA occlusion to get beneficial effects in our model, supporting the concept of a narrow therapeutic time window for intervention in ischemic stroke.     

Interplay between the gamma isoform of PKC and calcineurin in regulation of vulnerability to focal cerebral ischemia.

Protein phosphorylation and dephosphorylation mediated by protein kinases and protein phosphatases, respectively, represent essential steps in a variety of vital neuronal processes that could affect susceptibility to ischemic stroke. In this study, the role of the neuron-specific gamma isoform of protein kinase C (gammaPKC) in reversible focal ischemia was examined using mutant mice in which the gene for gammaPKC was knocked-out (gammaPKC-KO). A period of 150 minutes of unilateral middle cerebral artery and common carotid artery (MCA/CCA) occlusion followed by 21.5 hours of reperfusion resulted in significantly larger (P < 0.005) infarct volumes (n = 10; 31.1+/-4.2 mm3) in gammaPKC-KO than in wild-type (WT) animals (n = 12; 22.6+/-7.4 mm3). To control for possible differences related to genetic background, the authors analyzed Balb/cJ, C57BL/6J, and 129SVJ WT in the MCA/CCA model of focal ischemia. No significant differences in stroke volume were detected between these WT strains. Impaired substrate phosphorylation as a consequence of gammaPKC-KO might be corrected by inhibition of protein dephosphorylation. To test this possibility, gammaPKC-KO mice were treated with the protein phosphatase 2B (calcineurin) inhibitor, FK-506, before ischemia. FK-506 reduced (P < 0.008) the infarct volume in gammaPKC-KO mice (n = 7; 24.6+/-4.6 mm3), but at this dose in this model, had no effect on the infarct volume in WT mice (n = 7; 20.5+/-10.7 mm3). These results indicate that gammaPKC plays some neuroprotective role in reversible focal ischemia.     

A novel AMPA receptor antagonist, YM872, reduces infarct size after middle cerebral artery occlusion in rats

The neuroprotective effect of YM872 ([2.3-dioxo-7-(1H-imidazol-1-yl) 6-nitro-1,2,3,4-tetrahydro-1-quinoxalinyl]acetic acid monohydrate), a novel α-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor antagonist with improved water solubility, was examined in a rat focal cerebral ischemia model. Rats were subjected to permanent middle cerebral artery (MCA) occlusion using the intraluminal suture occlusion method for 24 h. YM872 was intravenously infused for 4 h (20 and 40 mg/kg/h) or 24 h (10 and 20 mg/kg/h), starting 5 min after the MCA occlusion, to investigate the effect of prolonged duration of the treatment on infarct volume. In the 4 h infusion study, YM872 reduced the cortical infarct volume by 48% at a dose of 40 mg/kg/h. YM872 did not significantly reduce the infarct at 20 mg/kg/h for 4 h. In the 24 h infusion study, however, YM872 markedly reduced the cortical infarct volume by 62%, even at 20 mg/kg/h. The present study indicates that the neuroprotective effect of YM872 is enhanced by extending the duration of treatment, and demonstrates the benefit of the prolonged treatment with AMPA antagonists following focal cerebral ischemia. YM872, a highly water soluble compound, is applicable to investigate the role of AMPA receptors in ischemic models without concern about nephrotoxicity and could be useful in the treatment of human stroke.     

Does poly-L-lysine coating of the middle cerebral artery occlusion suture improve infarct consistency in a murine model?

Background and Purpose: Rodent models of stroke that employ an intraluminal suture to cause focal cerebral ischemia are associated with some variability of resultant infarct volumes, thus requiring increased numbers of animals to determine significant differences between experimental groups. A recent modification of the occluding suture by coating with poly-L-lysine has been shown to create more uniform infarct volumes in rats. Methods: To evaluate the utility of this modification in murine models of both transient and permanent focal cerebral ischemia, male C57B16J mice were subjected to reversible middle cerebral artery occlusion (MCAo) for 45 minutes (n=42), or to permanent MCAo (n=25), with an intraluminal monofilament suture. Three types of sutures were used: untreated, partially coated, and completely coated with poly-L-lysine. Relative changes in regional cerebral blood flow, severity of neurological deficits, and infarct volumes were measured 24 hours after the ischemic injury. Results: Animals subjected to 45 minutes of temporary occlusion with completely coated poly-L-lysine sutures had infarct volumes of 13.8%+/-5% compared with infarct volumes of 7.2%+/-4% in those subjected to partially coated sutures and 22.4%+/-6% in the group occluded with untreated sutures (P=ns). Use of completely coated sutures resulted in significantly less reperfusion following suture removal. Control animals undergoing permanent occlusion with untreated sutures had infarct volumes of 17%+/-7% compared with 14.1%+/-5% using completely coated sutures and 6.5%+/-3% in animals with partially coated sutures (P=ns). There were no significant differences in cerebral blood flow between the experimental groups undergoing permanent MCAo. Conclusions: Poly-L-lysine coating of intraluminal sutures does not increase the consistency of infarct volumes in a murine model of temporary/permanent MCAo. These findings are in marked contrast to findings in rats.     

Photothrombotic occlusion of rat middle cerebral artery: histopathological and hemodynamic sequelae of acute recanalization

The histopathological and hemodynamic consequences of photochemically induced middle cerebral artery (MCA) thrombosis and recanalization were studied in the rat. Recanalization of the thrombosed MCA segment was achieved by the topical application of nimodipine at 1 h following photochemically induced occlusion. Pathological consequences of permanent and temporary occlusion were compared by morphometric procedures 7 days following thrombus formation. Rats with permanent thrombosis exhibited consistent infarction of both striatum and cortex. MCA recanalization at 1 h was associated with a significant reduction in total infarct volume. In recanalized rats, small cortical infarcts, confined to the peripheral MCA territory, were observed in only three of six rats. In contrast, a mixed pattern of infarction and ischemic cell damage was documented throughout the striatum in all rats. Local CBF (1CBF), measured autoradiographically, was significantly reduced in the MCA territory following 1 h of MCA occlusion, especially within the striatum. At 1 h after recanalization, 1CBF recovered within the previously ischemic brain regions to greater than 50% of control. Perfusion deficits were detected by carbon black infusion within focal areas of the striatum following reperfusion. Thus, cortical neurons appear to tolerate 1 h of MCA occlusion in this model. In contrast, reperfusion following 1 h of photochemically induced MCA occlusion gives rise to selective injury to the striatum.     

大脑中动脉梗死模型制作方法的研究

目的:通过大鼠短暂性大脑中动脉阻塞后梗死体积的测量和神经功能评分,评价改良大鼠大脑中动脉阻塞模型的可靠性。方法:分别使用包被有多聚-L-赖氨酸(0·1%)尼龙线和普通尼龙线,线栓法制作大鼠大脑中动脉阻塞模型,缺血2h后再灌注,分别在再灌注后3、24、48和72h联合应用八分法和姿势反射评价运动神经功能,3d后处死大鼠,测定梗死体积并进行比较。结果:运动神经功能评分结果与梗死体积成线性关系,多聚-L-赖氨酸包被线组制作模型的成功率高于普通线组,且梗死体积比普通线组大。结论:神经功能评分能很好的反映脑梗死的严重程度;采用多聚-L-赖氨酸包被的尼龙线能使大鼠大脑中动脉阻塞模型更可靠,成功率高,梗死体积和部位变异性小。     

Neuroprotection against transient cerebral ischemia by exercise pre-conditioning in rats

There is increasing evidence that physical activity is associated with decreased stroke risk and incidence. The purpose of this study was to determine whether increased levels of physical activity could reduce brain damage in rats subjected to transient or permanent middle cerebral artery (MCA) occlusion. Adult male Sprague-Dawley rats (three months old, n=36) exercised on a treadmill, which required repetitive locomotor movement, for 30 min each day for three weeks. Then, using an intraluminal filament, stroke was induced by either 2-h MCA occlusion followed by two days of reperfusion or by MCA occlusion for two days without reperfusion. Brain damage was determined by evaluating neurologic deficits and brain infarction. In rat with transient MCA occlusion, pre-ischemic motor activity significantly (p<0.01) reduced neurologic deficits and infarct volume in the frontoparietal cortex and the dorsolateral striatum. In contrast, the same exercise procedure did not produce neuroprotection in the permanently MCA-occluded stroke. In addition to decreasing stroke risk and incidence, physical activity also reduces brain damage after stroke. Although we cannot completely rule out a neuroprotective effect on ischemic episode, our study suggests that a major neuroprotection is conferred during reperfusion for rats that have undergone exercise pre-conditioning. This exercise-induced endogenous neuroprotection may be an effective strategy to ameliorate ischemia/reperfusion brain injury from stroke.     

局灶性脑缺血耐受和星形胶质细胞反应

目的　研究短暂性局灶性脑缺血预处理对永久性局灶性脑缺血的保护作用 ,及最佳预处理时间剂量 ,并探讨星形胶质细胞在脑缺血耐受中的反应。方法　采用开颅方法阻断大鼠大脑中动脉 ,通过观察大鼠脑梗死后神经功能损伤状况、脑梗死体积分析及病理形态学变化 ,评价不同的缺血预处理时间剂量 (10分钟、2 0分钟、30分钟 )对永久性局灶性脑缺血的保护作用。采用胶质纤维酸性蛋白 (GFAP)免疫组化法观察星形胶质细胞在脑缺血耐受中的反应。结果　与对照组相比 ,缺血预处理 2 0分钟未引起明显的神经元损伤 ,但使永久性局灶性脑缺血后神经功能损伤减轻 ,梗死体积明显减小 (P <0 .0 1)。免疫组化显示 ,2 0分钟缺血预处理组及重复缺血组星形胶质细胞在损伤预处理侧广泛激活。结论　 2 0分钟局灶性脑缺血预处理能够有效诱导脑缺血耐受。星形胶质细胞的激活可能与脑缺血耐受中神经元的存活相关。     

Extended therapeutic time window after focal cerebral ischemia by non-competitive inhibition of AMPA receptors

In acute stroke, the therapeutic time window is a critical factor which may have contributed to the failure of several phase III clinical trials with so-called neuroprotective agents. Since cerebral glutamate levels are elevated for many hours in progressing stroke, we investigated the novel AMPA glutamate receptor antagonist ZK 187638 in rodent models of stroke using up to 12 h delays in the start of therapy after permanent occlusion of the middle cerebral artery (MCA). In rats, ZK 187638 reduced total infarct volume by 43% and 33% when therapy was started immediately or with a delay of 6 h, respectively, but no effect was observed after a 12 h delay. Dose-dependent decreases of total infarct volume (up to 42%) were measured in mice given the first injection of ZK 187638 6 h after permanent MCA occlusion. In conclusion, the AMPA receptor antagonist ZK 187638 has a therapeutic time window of at least 6 h after permanent focal cerebral ischemia in rodents.     

Immediate or delayed mild hypothermia prevents focal cerebral infarction

The protective effect of mild hypothermia was studied in rodent models of both permanent and transient focal cerebral ischemia. In Expt. 1, Wistar rats were exposed to 6 h permanent ischemia by bilateral occlusion of both common carotid arteries and right middle cerebral artery. In Expt. 2, animals were exposed to 3 h transient ischemia followed by 21 h reperfusion, and in Expt. 3, 3 h transient ischemia was followed by 69 h of reperfusion. Expt. 4 used 3 h transient ischemia followed by 3 h reperfusion. In Expt. 1, animals maintained at 37 degrees C rectal (normothermia) suffered a mean infarct volume (+/- S.D.) of 142 +/- 44 mm3 (n = 6), which was reduced for those exposed to permanent hypothermic (32 degrees C) ischemia to 56 +/- 64 mm3 (n = 10) (P less than 0.05). In Expt. 2, normothermic ischemia and reperfusion resulted in an infarction of 211 +/- 35 mm3 (n = 6). Intra-ischemic hypothermia (32 degrees C) followed by 21 h of normothermic reperfusion resulted in 17 +/- 12 mm3 of infarction (n = 9) (P less than 0.001). Hypothermia for either the first or second 1.5 h of the 3 h ischemic insult reduced the infarct volume to 116 +/- 76 mm3 (n = 6) (P less than 0.05) or 108 +/- 73 mm3 (n = 7) (P less than 0.01), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)