Absence of glutathione peroxidase-1 exacerbates cerebral ischemia-reperfusion injury by reducing post-ischemic microvascular perfusion

Mice deficient in the anti-oxidant enzyme glutathione peroxidase-1 (Gpx1) have a greater susceptibility to cerebral injury following a localized ischemic event. Much of the response to ischemia-reperfusion is caused by aberrant responses within the microvasculature, including inflammation, diminished endothelial barrier function (increased vascular permeability), endothelial activation, and reduced microvascular perfusion. However, the role of Gpx1 in regulating these responses has not been investigated. Wild-type and Gpx1-/- mice underwent focal cerebral ischemia via mid-cerebral artery occlusion followed by measurement of cerebral perfusion via laser Doppler and intravital microscopy. Post-ischemic brains in wild-type mice displayed significant deficit in microvascular perfusion. However, in Gpx1-/- mice, the deficit in cerebral blood flow was significantly greater than that in wild-type mice, and this was associated with significant increase in infarct size and increased vascular permeability. Ischemia-reperfusion also resulted in expression of matrix metalloproteinase-9 (MMP-9) in endothelial cells. The absence of Gpx1 was associated with marked increase in pro-MMP-9 expression as well as potentiated MMP-9 activity. Pre-treatment of Gpx1-/- mice with the anti-oxidant ebselen restored microvascular perfusion, limited the induction and activation of MMP-9, and attenuated the increases in infarct size and vascular permeability. These findings demonstrate that the anti-oxidant function of Gpx1 plays a critical role in protecting the cerebral microvasculature against ischemia-reperfusion injury by preserving microvascular perfusion and inhibiting MMP-9 expression.     

The Akt/GSK-3β pathway mediates flurbiprofen-induced neuroprotection against focal cerebral ischemia/reperfusion injury in rats

Apoptosis is one of the major mechanisms of cell death during cerebral ischemia and reperfusion injury. Flurbiprofen has been shown to reduce cerebral ischemia/reperfusion injury in both focal and global cerebral ischemia models, but the mechanism remains unclear. This study aimed to investigate the potential association between the neuroprotective effect of flurbiprofen and the apoptosis inhibiting signaling pathways, in particularly the Akt/GSK-3β pathway. A focal cerebral ischemia rat model was subjected to middle cerebral artery occlusion (MCAO) for 120 min and then treated with flurbiprofen at the onset of reperfusion. The infarct volume and the neurological deficit scores were evaluated at 24 h after reperfusion. Cell apoptosis, apoptosis-related proteins and the levels of p-Akt and p-GSK-3β in ischemic penumbra were measured using TUNEL and western blot. The results showed that administration of flurbiprofen at the doses of 5 and 10 mg/kg significantly attenuated brain ischemia/reperfusion injury, as shown by a reduction in the infarct volume, neurological deficit scores and cell apoptosis. Moreover, flurbiprofen not only inhibited the expression of Bax protein and p-GSK-3β, but also increased the expression of Bcl-2 protein, the ratio of Bcl-2/Bax as well as the P-Akt level. Taken together, these results suggest that flurbiprofen protects the brain from ischemia/reperfusion injury by reducing apoptosis and this neuroprotective effect may be partly due to the activation of Akt/GSK-3β signaling pathway.     

大鼠脑缺血区细胞间粘附分子ICAM-1表达和LFA-1阳性细胞浸润的研究

研究粘附分子和白细胞与脑缺血／再灌流损伤的病理联系,运用原位杂交和免疫组化技术对36只SD大鼠脑缺血区细胞间粘附分子（ICAM－1）表达和淋巴细胞机能相关抗原（LFA－1）阳性细胞浸润进行了观察。结果显示,脑缺血区的毛细胞血管内皮细胞表达ICAM－1 mRNA发生于脑缺血1h,在脑缺血1h／再灌流8h达到高峰。而脑缺血区毛细血管ICAM－1蛋白质的表达则发生于脑缺血1h／再灌流2h,高峰出现于脑缺血1h／再灌流16h,LFA－1阳性细胞在脑缺血区的聚集发生在脑缺血1h,并随再灌流时间延长,其聚集数量逐渐增加。结果提示,脑缺血／再灌流能诱导缺血区的血管内皮细胞表达ICAM－1 mRNA和蛋白质,进而导致白细胞在脑缺血区的浸润,此可能是脑缺血／再灌流损伤的病理机制之一。     

A natural coumarin derivative esculetin offers neuroprotection on cerebral ischemia/reperfusion injury in mice

Previous studies have demonstrated that a natural coumarin compound esculetin (Esc) possesses antioxidant, anti-tumor, and anti-inflammation activities and rescues cultured primary neurons from NMDA toxicity. In this study, we investigated the neuroprotective effects of Esc on cerebral ischemia/reperfusion (I/R) injury in a middle cerebral artery occlusion model in mice. Esc (20 μg) was administered intracerebroventricularly at 30 min before ischemia. We found that Esc significantly reduced infarct volume and decreased neurological deficit scores after 75 min of ischemia and 24 h of reperfusion. Post-treatment of Esc still provided neuroprotection even when Esc was administered after 4 h of reperfusion. Our data also indicated that intraperitoneal administration of Esc showed protective effects on cerebral I/R injury in a dose-dependent manner. We further explored the protective mechanisms of Esc on cerebral I/R injury and found that Esc decreased cleaved caspase 3 level, a marker of apoptosis. Finally, our data demonstrated that Esc exerted its anti-apoptotic activity by up-regulating the expression of Bcl-2 and down-regulating the expression of Bax, two apoptosis-related proteins. Because of its clinical use as an anticoagulant and its safety profile, Esc may have a therapeutic potential for the treatment of stroke in the future clinical trials.     

Remifentanil preconditioning alleviating brain damage of cerebral ischemia reperfusion rats by regulating the JNK signal pathway and TNF-α/TNFR1 signal pathway

Tumor necrosis factor (TNF) and the TNF receptor (TNFR) superfamily play very important roles for cell death as well as normal immune regulation. Previous studies have strongly suggested that c-Jun N-terminal kinase (JNK) signaling pathway plays a critical role in ischemic brain injury. The purpose of this investigation was to examine the protective effect of remifentanil preconditioning in cerebral ischemia/reperfusion injury (CIR) and its possible molecular mechanism. Results showed that Remifentanil pretreatment significantly decreased the CD4⁺ and increased the CD8⁺ in cerebral tissues. Additionally, CD4⁺/CD8⁺ in CIR + Remifentanil group was markedly lower than that in CIR group. TNF-α and TNFR1 in CIR + Remifentanil group rats was found to be significant lower than that in CIR group rats. The expression levels of Cyt-c, caspase-3, caspase-9 and pJNK proteins in brain of CIR + Remifentanil group rats were found to significantly decreased compared to CIR group rats. In addition, decreased ROS level indirectly inhibit JNK activation and cell death in CIR rat receiving Remifentanil preconditioning. From current experiment results, at least two signal pathways involve into the process of Remifentanil preconditioning inhibiting cerebral damage induced by ischemia reperfusion. The inhibitory effects of Remifentanil preconditioning on the brain damage are achieved probably through blocking the activation of TNF-α/TNFR1, JNK signal transduction pathways, which implies that Remifentanil preconditioning may be a potential and effective way for prevention of the ischemic/reperfusion injury through the suppression extrinsic apoptotic signal pathway induced by TNF-α/TNFR1, JNK signal pathways. Taken together, this study indicated that regulation of the TNF-α/TNFR1 and JNK signal pathways may provide a new therapy for cerebral damage induced by ischemia and reperfusion.     

毛蕊异黄酮通过抑制calpain-1的表达发挥抗脑缺血再灌注损伤的研究

目的:探讨毛蕊异黄酮抗脑缺血再灌注损伤的作用是否与抑制calpain-1的表达有关。方法:将SD大鼠随机分为假手术组、模型组以及药物组,采用线栓法建立大鼠大脑中动脉阻断(MCAO)模型,于缺血再灌注前30 min腹腔注射给予20 mg/kg毛蕊异黄酮或等体积的溶剂。再灌注24 h后,行神经功能学评分、脑梗死面积以及神经元凋亡检测;再灌注12 h、24 h时,采用免疫组化和蛋白印迹技术检测大鼠脑皮层calpain-1的表达。结果:与假手术组大鼠比较,MCAO模型组大鼠再灌注24 h后神经功能学评分、梗死面积、神经元凋亡率及calpain-1的表达均明显升高(P0.05),而毛蕊异黄酮能够降低模型组大鼠再灌注24 h后神经功能学评分、梗死面积、神经元凋亡率以及calpain-1的表达(P0.05)。结论:毛蕊异黄酮可能通过抑制calpain-1的表达发挥抗脑缺血再灌注损伤作用。     

Neuroprotection of Ro25-6981 Against Ischemia/Reperfusion-Induced Brain Injury via Inhibition of Autophagy

In this study, we investigated the neuroprotective effect of Ro25-6981 against cerebral ischemia/reperfusion injury. Ro25-6981 alone or in combination with rapamycin was intracerebroventricularly administered to rats which suffered transient forebrain ischemia inducing by 4-vessel occlusion and reperfusion. Nissl staining was used to determine the survival of CA1 pyramidal cells of the hippocampus, while immunohistochemistry was performed to measure neuron-specific enolase (NSE) expression. The expression of autophagy-related proteins, such as microtubule-associated protein l light chain 3 (LC3), Beclin 1, and sequestosome 1 (p62), was assessed by immunoblotting. Nissl staining showed that neuronal damage was reduced in the hippocampal CA1 pyramidal layer in rats that received Ro25-6981. The protective effect of Ro25-6981 was dose-dependent, with a significant effect in the middle-dose range. The expression of NSE increased after Ro25-6981 treatment. Ro25-6981 significantly decreased LC3II (which is membrane bound) and Beclin 1, and increased p62. In addition, Ro25-6981 decreased rapamycin-induced neuronal damage and excessive activation of autophagy after I/R. Taken together, the results suggest that Ro25-6981 could suppress ischemic brain injury by regulating autophagy-related proteins during ischemia/reperfusion.     

Pathogenic natural antibodies propagate cerebral injury following ischemic stroke in mice

Self-reactive natural Abs initiate injury following ischemia and reperfusion of certain tissues, but their role in ischemic stroke is unknown. We investigated neoepitope expression in the postischemic brain and the role of natural Abs in recognizing these epitopes and mediating complement-dependent injury. A novel IgM mAb recognizing a subset of phospholipids (C2) and a previously characterized anti-annexin IV mAb (B4) were used to reconstitute and characterize injury in Ab-deficient Rag1(-/-) mice after 60 min of middle cerebral artery occlusion and reperfusion. Reconstitution with C2 or B4 mAb in otherwise protected Rag1(-/-) mice restored injury to that seen in wild-type (wt) mice, as demonstrated by infarct volume, demyelination, and neurologic scoring. IgM deposition was demonstrated in both wt mice and reconstituted Rag1(-/-) mice, and IgM colocalized with the complement activation fragment C3d following B4 mAb reconstitution. Further, recombinant annexin IV significantly reduced infarct volumes in wt mice and in Rag1(-/-) mice administered normal mouse serum, demonstrating that a single Ab reactivity is sufficient to develop cerebral ischemia reperfusion injury in the context of an entire natural Ab repertoire. Finally, C2 and B4 mAbs bound to hypoxic, but not normoxic, human endothelial cells in vitro. Thus, the binding of pathogenic natural IgM to postischemic neoepitopes initiates complement-dependent injury following murine cerebral ischemia and reperfusion, and, based also on previous data investigating IgM reactivity in human serum, there appears to be a similar recognition system in both mouse and man.     

阻断趋化因子CXCL10对脑缺血再灌注损伤及神经炎症的影响

目的:探讨趋化因子CXCL10在脑缺血再灌注损伤中对神经炎症的影响。方法:(1)线栓法建立脑缺血再灌注损伤大鼠模型,TTC染色检测梗死面积,Western blot检测CXCL10的表达;(2)建立小鼠神经瘤母细胞N2a氧糖剥夺/复氧(oxygen-glucose deprivation/reoxygenation,OGD/R)模型,通过CXCR3拮抗剂-NBI 74330阻断趋化因子CXCL10表达,Western blot检测CXCL10和CXCR3蛋白的表达;Real-time PCR检测CXCL10、CXCR3以及神经炎症因子TNF-α、IL-1β、IL-2 m RNA的表达。结果:(1)脑缺血再灌注(cerebral ischemia reperfusion injury,CIRI)模型大鼠脑梗死侧CXCR10的表达量显著高于其对侧和假手术组(P<0.05);(2)阻断CXCL10使得小鼠神经瘤母细胞N2a中CXCL10、CXCR3以及炎症因子TNF-α、IL-1β、IL-2的表达量均显著降低(P<0.05);(3)阻断CXCL10使得小鼠神经瘤母细胞细胞凋亡率降低(P<0.05)。结论:抑制CXCL10降低了氧糖剥夺模型细胞炎症因子的表达,表明阻断CXCL10可能通过减轻神经炎症在脑缺血再灌注损伤中发挥保护作用。     

A novel cell-permeable antioxidant peptide, SS31, attenuates ischemic brain injury by down-regulating CD36

Oxidative stress is implicated in the pathogenesis of ischemia/reperfusion injury. Recently, we demonstrated that activation of CD36, a class B scavenger receptor, mediates free radical production and tissue injury in cerebral ischemia (1). Oxidized low density lipoproteins (oxLDL) are among the ligands that bind to CD36 and are elevated in acute cerebral infarction. SS31 is a cell-permeable antioxidant peptide that reduces intracellular free radicals and inhibits LDL oxidation/lipid peroxidation (2). The current study was designed to investigate whether treatment with SS31 normalizes ischemia-induced redox changes and attenuates CD36-mediated tissue injury. C57BL/6 mice were subjected to transient middle cerebral artery occlusion (MCAO). Redox status and infarct volume were measured in animals treated with either saline or SS31. Oxidative stress induced by ischemia/reperfusion profoundly depleted glutathione (GSH) concentrations in the ipsilateral cortex and striatum. Treating mice with SS31 immediately after reperfusion significantly attenuated ischemia-induced GSH depletion in the cortex and reduced infarct size. By contrast, the protective effect of SS31 was absent in CD36 knock-out mice, indicating that SS31 is acting through inhibition of CD36. Treating C57BL/6 mice with SS31 reduced CD36 expression in postischemic brain and mouse peritoneal macrophages (MPM). Further in vitro studies revealed that SS31 attenuated oxLDL-induced CD36 expression and foam cell formation in MPM. These in vivo and in vitro studies indicate that the down-regulation of CD36 by novel class antioxidant peptides may be a useful strategy to treat ischemic stroke victims.     

小鼠短暂前脑缺血海马中半胱天冬酶-３酶原表达的变化

通过测定脑缺血再灌注时海马中半胱天冬酶-3酶原(procaspase-3)的表达变化, 从细胞凋亡的角度探讨脑缺血再灌注损伤的分子生物学机制及procaspase-3的活化机制.将C57BL/6N小鼠随机分为假手术组(正常对照组)、缺血再灌注组(I/R组), 后者夹闭双侧颈总动脉20 min后再通血流, 建立前脑缺血再灌注模型, 分别于再灌注6 h、12 h、24 h和48 h取海马.采用蛋白免疫印迹(Western blotting)方法检测海马中procaspase-3的表达变化.结果显示, 12 h I/R及24hI/R组海马中总procaspase-3水平与假手术组相比有明显升高, 且差异有统计学意义(P<0.05),24 h I/R组海马中去磷酸化水平与假手术组相比有明显升高, 且差异有统计学意义(P<0.05),而各组procaspase-3磷酸化水平与假手术组相比差异无统计学意义.结果提示, 脑缺血再灌注损伤诱发procaspase-3表达增加,其中procaspase-3去磷酸化水平高明显, 提示脑缺血再灌注损伤可能诱发procaspase-3去磷酸化, 继而促进procaspase-3转化为活性形式.     

Diminished Akt phosphorylation in neurons lacking glutathione peroxidase-1 (Gpx1) leads to increased susceptibility to oxidative stress-induced cell death

We have previously identified an increased susceptibility of glutathione peroxidase-1 (Gpx1)-/- mice to neuronal apoptosis following mid-cerebral artery (MCA) occlusion. This study was designed to elucidate the mechanisms involved in elevated neuronal cell death arising from an altered endogenous oxidant state. This was addressed in both an in vitro and in vivo model of oxidative stress in the form of exogenous H2O2 and cerebral ischaemia, respectively. Increased levels of cell death were detected in primary neurons lacking Gpx1 following the addition of exogenous H2O2. This increased apoptosis correlated with a down-regulation in the activation of the phospho-inositide 3-kinase [PI3K]-Akt survival pathway. The importance of this pathway in protecting against H2O2-induced cell death was highlighted by the increased susceptibility of wildtype neurons to apoptosis when treated with the PI3K inhibitor, LY294002. The Gpx1-/- mice also demonstrated elevated neuronal cell death following MCA occlusion. Although Akt phosphorylation was detected in the Gpx1-/- brains, activation was not seen in later reperfusion events, as demonstrated in wildtype brains. Previous studies have highlighted the importance of Akt phosphorylation in protecting against neuronal cell death following cerebral ischaemia-reperfusion. Our results suggest that the increased susceptibility of Gpx1-/- neurons to H2O2-induced apoptosis and neuronal cell death in vivo following cerebral ischaemia-reperfusion injury can be attributed in part to diminished activation of Akt. Perturbations in key anti-apoptotic mechanisms as a result of an altered redox state may have implications in the study of oxidative stress-mediated neuropathologies.     

不同亚型一氧化氮合酶在脑缺血/再灌注早期的表达变化

目的:观察脑缺血/再灌注(CI/R)早期缺血区脑组织的内皮型一氧化氮合酶(eNOS)与神经型一氧化氮合酶(nNOS)表达的变化。方法:健康wistar大鼠60只,体重200～280g,由中国医科大学动物中心提供,雌雄各半。随机分为6组(n=10):假手术组、缺血1h组、缺血2h组、再灌注0.5h组、再灌注1h组、再灌注2h组。采用线栓法制作大鼠CI/R模型,免疫组化方法检测缺血区脑组织的eNOS与nNOS蛋白表达情况。结果:与假手术组比较,CI/R模型大鼠脑组织血管内皮细胞内eNOS表达在缺血1h内升高,之后到再灌注2h内持续降低。而nNOS的表达在缺血到再灌注2h内持续上升。结论:CI/R模型中缺血区脑组织的eNOS与nNOS的变化趋势不同,表明一氧化氮在缺血性脑损伤病理过程的作用与一氧化氮合酶亚型的变化有关。     

Increased infarct size and exacerbated apoptosis in the glutathione peroxidase-1 (Gpx-1) knockout mouse brain in response to ischemia/reperfusion injury

Glutathione peroxidase is an antioxidant enzyme that is involved in the control of cellular oxidative state. Recently, unregulated oxidative state has been implicated as detrimental to neural cell viability and involved in both acute and chronic neurodegeneration. In this study we have addressed the importance of a functional glutathione peroxidase in a mouse ischemia/reperfusion model. Two hours of focal cerebral ischemia followed by 24 h of reperfusion was induced via the intraluminal suture method. Infarct volume was increased three-fold in the glutathione peroxidase-1 (Gpx-1) -/- mouse compared with the wild-type mouse; this was mirrored by an increase in the level of apoptosis found at 24 h in the Gpx-1 -/- mouse compared with the wild-type mouse. Neuronal deficit scores correlated to the histologic data. We also found that activated caspase-3 expression is present at an earlier time point in the Gpx-1 -/- mice when compared with the wild-type mice, which suggests an enhanced susceptibility to apoptosis in the Gpx-1 -/- mouse. This is the first known report of such a dramatic increase, both temporally and in level of apoptosis in a mouse stroke model. Our results suggest that Gpx-1 plays an important regulatory role in the protection of neural cells in response to the extreme oxidative stress that is released during ischemia/reperfusion injury.     

Effects of intracerebroventricular injection of delta-opioid receptor agonist TAN-67 or antagonist naltrindole on acute cerebral ischemia in rat

This work was performed to determine the role of delta-opioid receptor (DOR) in protection against acute ischemia/reperfusion injury. Transient (1 h) focal cerebral ischemia was induced by middle cerebral artery occlusion (MCAO). DOR agonist TAN-67 (30 nmol, 60 nmol, 200 nmol), DOR antagonist naltrindole (20 nmol, 50 nmol, 100 nmol) or artificial cerebral spinal fluid (aCSF) was injected respectively into the lateral cerebroventricle of the rat 30 min before the induction of brain ischemia. Neurological deficits were assessed by the five-grade system (Longa's methods). The brain infarct was measured by cresyl violet (CV) staining and infarct volume was analyzed by an image processing and analysis system. The expression of DOR was detected by Western blot. The results showed that 60 nmol TAN-67 significantly reduced the infarct volume (P<0.05), attenuated neurological deficits (P<0.05) and tended to increase the expression of about 60 kDa DOR protein (P>0.05), while 100 nmol naltrindole aggravated ischemic damage and decreased about 60 kDa DOR protein expression (P<0.05). These results suggest that DOR activation protects the brain against acute ischemia/reperfusion injury in rat.     

Hydroxyl Radical Formation in Hyperglycemic Rats During Middle Cerebral Artery Occlusion/Reperfusion

Preexisting hyperglycemia is associated with enhanced reperfusion injury in the postischemic rat brain. The goal of this study was to evaluate whether the hyperglycemic exacerbation of brain injury is associated with enhanced generation of hydroxyl radicals in rats subjected to middle cerebral artery occlusion (2 h), followed by reperfusion (2 h). Magnetic resonance images revealed the exacerbation of focal brain injury in hyperglycemic rats. The salicylate trapping method was used in conjunction with microdialysis to continuously estimate hydroxyl radical production by measurement of the stable adducts 2,3- and 2,5-dihydroxybenzoic acid (DHBA) during ischemia/reperfusion. In normoglycemic rats, from a mean baseline level of 130 nmol/l, 2,3-DHBA levels surged to peak levels of 194 nmol/l 45 min into ischemia and to 197 nmol/l 15–30 min into the reperfusion period, returning to baseline by 2 h into reperfusion. A similar temporal profile was observed in hyperglycemic rats, except that absolute 2,3-DHBA levels were higher (165 nmol/l at baseline, 317 nmol/l peak during ischemia, 333 nmol/l peak during reperfusion), and levels remained significantly high (p < .05) throughout the reperfusion period. These results suggest that hydroxyl radical is an important contributor to the exacerbation of neuronal and cerebrovascular injury after focal ischemia/reperfusion in hyperglycemic rats.     

Hypothermia Protects the Brain from Transient Global Ischemia/Reperfusion by Attenuating Endoplasmic Reticulum Response-Induced Apoptosis through CHOP

Endoplasmic reticulum (ER) stress has been implicated in the pathology of cerebral ischemia. Apoptotic cell death occurs during prolonged period of stress or when the adaptive response fails. Hypothermia blocked the TNF or Fas-mediated extrinsic apoptosis pathway and the mitochondria pathway of apoptosis, however, whether hypothermia can block endoplasmic reticulum mediated apoptosis is never known. This study aimed to elucidate whether hypothermia attenuates brain cerebral ischemia/reperfusion (I/R) damage by suppressing ER stress-induced apoptosis. A 15 min global cerebral ischemia rat model was used in this study. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) positive cells in hippocampus CA1 were assessed after reperfusion of the brain. The expressions of C/EBP-homolo gous protein (CHOP) and glucose-regulated protein 78 (GRP78) in ischemic hippocampus CA1 were measured at 6, 12, 24 and 48 h after reperfusion. The results showed that hypothermia significantly attenuated brain I/R injury, as shown by reduction in cell apoptosis, CHOP expression, and increase in GRP78 expression. These results suggest that hypothermia could protect brain from I/R injury by suppressing ER stress-induced apoptosis.     

Effects of ischemia/reperfusion on brain tissue prostanoids and leukotrienes in newborn pigs.

We investigated the hypothesis that cerebral prostanoid and peptidoleukotriene (LTs) (LTC4/D4/E4/F4) synthesis are increased during postischemic reperfusion of newborn pig brains. Prostanoids and LTs extracted from brain tissue were determined by RIA in sham-control piglets and at 1h, 3h, or 12h after a 20-min period of total cerebral ischemia. During reperfusion following ischemia, all regional brain tissue (cerebrum, brain stem and cerebellum) prostanoids (6-keto-PGF1 alpha, TXB2, PGE2 and PGF2 alpha) were increased at 1h compared with those in sham-control piglets. Only cerebral and brain stem 6-keto-PGF1 alpha and cerebral TXB2 remained elevated at 3h postischemia and all prostanoids returned to control levels by 12h postischemia. Brain tissue LTs were lower than prostanoids and were not altered 1, 3, or 12h following ischemia. These data indicate that 1) newborn pig brain tissue prostanoids are increased initially, and then returned to control levels at later stages of reperfusion following ischemia; 2) LTs are present in newborn pig brain tissue, but are not increased by ischemia/reperfusion injury and therefore probably do not play a significant role in cerebral ischemia-reperfusion injury.