Motheaten (me/me) mice deficient in SHP-1 are less susceptible to focal cerebral ischemia

We have demonstrated previously that the protein tyrosine phosphatase SHP-1 seems to play a role in glial development and is upregulated in non-dividing astrocytes after injury. The present study examines the effect of loss of SHP-1 on the CNS response to permanent focal ischemia. SHP-1 deficient (me/me) mice and wild-type littermates received a permanent middle cerebral artery occlusion (MCAO). At 1, 3, and 7 days after MCAO, infarct volume, neuronal survival and cell death, gliosis, and inflammatory cytokine levels were quantified. SHP-1 deficient me/me mice display smaller infarct volumes at 7 days post-MCAO, increased neuronal survival within the ischemic penumbra, and decreased numbers of cleaved caspase 3+ cells within the ischemic core compared with wild-type mice. In addition, me/me mice exhibit increases in GFAP+ reactive astrocytes, F4-80+ microglia, and a concomitant increase in the level of interleukin 12 (IL-12) over baseline compared with wild-type. Taken together, these results demonstrate that loss of SHP-1 results in greater healing of the infarct due to less apoptosis and more neuronal survival in the ischemic core and suggests that pharmacologic inactivation of SHP-1 may have potential therapeutic value in limiting CNS degeneration after ischemic stroke.     

Protective role for type 4 metabotropic glutamate receptors against ischemic brain damage

We examined the influence of type 4 metabotropic glutamate (mGlu4) receptors on ischemic brain damage using the permanent middle cerebral artery occlusion (MCAO) model in mice and the endothelin-1 (Et-1) model of transient focal ischemia in rats. Mice lacking mGlu4 receptors showed a 25% to 30% increase in infarct volume after MCAO as compared with wild-type littermates. In normal mice, systemic injection of the selective mGlu4 receptor enhancer, N-phenyl-7-(hydroxyimino)cyclopropa[b]chromen-1a-caboxamide (PHCCC; 10 mg/kg, subcutaneous, administered once 30 minutes before MCAO), reduced the extent of ischemic brain damage by 35% to 45%. The drug was inactive in mGlu4 receptor knockout mice. In the Et-1 model, PHCCC administered only once 20 minutes after ischemia reduced the infarct volume to a larger extent in the caudate/putamen than in the cerebral cortex. Ischemic rats treated with PHCCC showed a faster recovery of neuronal function, as shown by electrocorticographic recording and by a battery of specific tests, which assess sensorimotor deficits. These data indicate that activation of mGlu4 receptors limit the development of brain damage after permanent or transient focal ischemia. These findings are promising because selective mGlu4 receptor enhancers are under clinical development for the treatment of Parkinson''s disease and other central nervous system disorders.     

Monocyte chemoattractant protein-1 deficiency is protective in a murine stroke model.

Inflammatory processes have been implicated in the pathogenesis of brain damage after stroke. In rodent stroke models, focal ischemia induces several proinflammatory chemokines, including monocyte chemoattractant protein-1 (MCP-1). The individual contribution to ischemic tissue damage, however, is largely unknown. To address this question, the authors subjected MCP-1-deficient mice (MCP-1-/-) to permanent middle cerebral artery occlusion (MCAO). Measurement of basal blood pressure, cerebral blood flow, and blood volume revealed no differences between wild-type (wt) and MCP-1-/- mice. MCAO led to similar cerebral perfusion deficits in wt and MCP-1-/- mice, excluding differences in the MCA supply territory and collaterals. However, compared with wt mice, the mean infarct volume was 29% smaller in MCP-1-/- mice 24 hours after MCAO (P = 0.022). Immunostaining showed a reduction of phagocytic macrophage accumulation within infarcts and the infarct border in MCP-1-/- mice 2 weeks after MCAO. At the same time point, the authors found an attenuation of astrocytic hypertrophy in the infarct border and thalamus in MCP-1-/- mice. However, these effects on macrophages and astrocytes in MCP-1-/- mice occurred too late to suggest a protective role in acute infarct growth. Of note: at 6 hours after MCAO, MCP-1-/- mice produced significantly less interleukin-1beta in ischemic tissue; this might be related to tissue protection. The results of this study indicate that inhibition of MCP-1 signaling could be a new acute treatment approach to limit infarct size after stroke.     

一氧化氮供体及前体对大鼠脑缺血再灌注损伤保护机制的探讨

目的 观察介入给药一氧化氮（NO）供体硝酸甘油（Nitroglycerine，NG）及前体L-精氨酸（L-Arginine，ARG）对大鼠脑缺血再灌注后海马区星形胶质细胞表达的胶质纤维酸性蛋白（GFAP）的影响，探讨NG及ARG的脑保护机制。方法 采用大鼠大脑中动脉阻塞（MCAO）法建立局灶性脑缺血模型。将大鼠随机分为假手术组、MCAO组、NG组和ARG组。MCAO组、NG组和ARG组于缺血2 h再灌注同时分别局部介入给予生理盐水、NG和ARG，于再灌注3 h或24 h时，荧光法检测血清NO含量。并在3 h或24 h时处死大鼠，病理分析脑梗死体积以及免疫组织化学法检测海马区GFAP表达情况。结果 缺血再灌注后3 h血清NO升高（P <0.01），治疗组较MCAO组明显（P <0.01），GFAP表达阳性细胞数增加，但治疗组较MCAO组减少（P <0.01），各组大鼠脑组织未出现肉眼可见梗死灶；缺血再灌注后24 h，血清NO治疗组较3 h降低，而MCAO组较3 h升高（P <0.05），GFAP表达阳性细胞数较3 h增加（P <0.01），治疗组较MCAO组减少（P <0.01），TTC染色显示脑梗死体积治疗组较MCAO组减小（P <0.05）。结论 脑缺血再灌注后海马区脑组织GFAP表达增强，通过局部介入给予NG、ARG增加NO合成，抑制GFAP高表达，减小脑梗死体积。提示NG、ARG抗脑缺血性损伤的保护机制可能与抑制星形胶质细胞过度表达有关。     

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.     

PHLPP1 gene deletion protects the brain from ischemic injury

A recently discovered protein phosphatase PHLPP (PH domain Leucine-rich repeat Protein Phosphatase) has been shown to dephosphorylate Akt on its hydrophobic motif (Ser473) thereby decreasing Akt kinase activity. We generated PHLPP1 knockout (KO) mice and used them to explore the ability of enhanced in vivo Akt signaling to protect the brain against ischemic insult. Brains from KO mice subjected to middle cerebral artery occlusion (MCAO) for 2 hours showed significantly greater increases in Akt activity and less neurovascular damage after reperfusion than wild-type (WT) mice. Remarkably, infarct volume in the PHLPP1 KO was significantly reduced compared with WT (12.7±2.7% versus 22.9±3.1%) and this was prevented by Akt inhibition. Astrocytes from KO mice and neurons in which PHLPP1 was downregulated showed enhanced Akt activation and diminished cell death in response to oxygen-glucose deprivation. Thus, deletion of PHLPP1 can enhance Akt activation in neurons and astrocytes, and can significantly increase cell survival and diminish infarct size after MCAO. Inhibition of PHLPP could be a therapeutic approach to minimize damage after focal ischemia.     

Focal cerebral ischemia upregulates SHP-1 in reactive astrocytes in juvenile mice

The role of the tyrosine phosphatase SHP-1 in the hematopoietic system has been well studied; however, its role in the central nervous system (CNS) response to injury is not well understood. Previous studies in our laboratory have demonstrated increased immunoreactivity for SHP-1 in a subset of reactive astrocytes that do not appear to enter the cell cycle following deafferentation of the chicken auditory brainstem. In order to determine whether mammalian astrocytes also upregulate SHP-1 immunoreactivity following CNS injury, a mouse model of focal cerebral ischemia was utilized to study SHP-1 expression. The brains of 3-week-old mice were analyzed at four time points following permanent middle cerebral artery occlusion (MCAO): 1, 3, 7, and 14 days. Our results demonstrate consistent infarct volumes within surgical groups, and infarct volumes decrease as a function of time from 1 day (maximum infarct volume) to 14 days (minimum infarct volume) post-MCAO. In addition, SHP-1 protein levels are upregulated following cerebral ischemia and this increase peaks at 7 days post-MCAO. Analysis of confocal images further reveals that immunoreactivity for SHP-1 occurs predominantly in GFAP+ reactive astrocytes, although a small percentage of F4-80+ microglia are also double labeled for SHP-1 at early times post-MCAO. These SHP-1+ reactive astrocytes do not appear to enter the cell cycle (as defined by PCNA immunoreactivity), confirming our previous studies in the avian auditory brainstem. These results suggest that SHP-1 plays an important role in the regulation of glial activation and proliferation in the ischemic CNS.     

bcl-xl over-expression in transgenic mice reduces cerebral ischemia/reperfusion injury*☆

BACKGROUND： Basal cell lymphoma-extra large （bcl-xl） can inhibit neuronal apoptosis by stabilizing the mitochondrial membrane and suppressing cytochrome C release into the cytoplasm. OBJECTIVE： This study aimed to further investigate the cascade reaction pathway of cellular apoptosis. We established an ischemia/repcrfusion model by middle cerebral artery occlusion （MCAO） in transgenic and wild-type mice, and observed changes in the number and distribution of apoptotic neural cells, differences in cerebral infarct volume, in neurological function score, and in cytochrome C expression in the ischemic cerebral cortex, at different time points, DESIGN AND SETTING： The present gene engineering and cell biology experiment was performed at the Laboratory of Biology, Hubei Academy of Agricultural Sciences and at the Laboratory of Immunology, Tongji Medical College, Huazhong University of Science and Technology. MATERIALS： Male bcl-xl over-expression Kunming mice aged 8 weeks and age-matched male wild-type mice were used for this study. Terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling （TUNEL） kits were purchased from Boliman, France. Cytochrome C antibody and Bcl-x immunohistochemical kit were purchased from PharMingen, USA and Santa Cruz Biotechnology, USA, respectively. METHODS： Following MCAO and reperfusion, apoptosis in the ischemic cerebral cortex was detected by the TUNEL assay. Prior to MCAO and 3 hours after reperfusion, the Bcl-xl protein level in the ischemic cerebral cortex was measured by immunohistochemistry. At 3, 6, 12 and 24 hours after reperfusion, the level of cytochrome C in the ischemic cerebral cortex was examined by western blot analysis. Subsequent to MCAO, cerebral infarct volume measurement and neurological examination were performed. MAIN OUTCOME MEASURES： Neural cell apoptosis and cytochrome C expression in the ischemic cerebral cortex; cerebral infarct volume and neurological function score. RESULTS： Twenty-four hours after reperfusion, cerebral inf     

bcl-xl over-expression in transgenic mice reduces cerebral ischemia/reperfusion injury

BACKGROUND:Basal cell lymphoma-extra large (bcl-xl) can inhibit neuronal apoptosis by stabilizing the mitochondrial membrane and suppressing cytochrome C release into the cytoplasm. OBJECTIVE: This study aimed to further investigate the cascade reaction pathway of cellular apoptosis. We established an ischemia/reperfusion model by middle cerebral artery occlusion (MCAO) in transgenic and wild-type mice,and observed changes in the number and distribution of apoptotic neural cells,differences in cerebral infa...     

Administration of transforming growth factor-alpha reduces infarct volume after transient focal cerebral ischemia in the rat.

Growth factors promote cell growth and survival and protect the brain from developing injury after ischemia. In this article, the authors examined whether transforming growth factor-alpha (TGF-alpha) was protective in transient focal ischemia and whether alteration of cerebral circulation was involved. Rats received intraventricular TGF-alpha (50 ng, either split into 2 doses given 30 minutes before and 30 minutes after middle cerebral artery occlusion (MCAO), or 1 dose given 30 minutes after MCAO) or vehicle. Rats were subjected to 1-hour intraluminal MCAO and cerebral blood flow was recorded continuously by laser-Doppler flowmetry. Infarct volume was measured 1 and 4 days later. The effects of TGF-alpha on arterial tone were assessed in isolated rabbit basilar and common carotid arteries. Transforming growth factor-alpha before and after ischemia reduced infarct volume by 70% at 1 day and 50% at 4 days. Transforming growth factor-alpha given only after ischemia also did reduce infarct volume by 70% at 1 day and 80% at 4 days. The protective effect was more marked in cortex than in striatum. Transforming growth factor-alpha did not change cortical microvascular perfusion and did not modify arterial passive tone nor agonist-induced active tone. It can be concluded that TGF-alpha reduces infarct volume, even when the factor is exclusively administered at reperfusion, and that this effect is not mediated by changes in microvascular perfusion or cerebral arteries. It is therefore suggested that TGF-alpha has a protective effect against neuronal cell death after transient focal ischemia.     

预防及超早期应用尼莫同对小鼠局灶性脑梗死的影响

目的观察尼莫同超早期给药对小鼠局灶性脑梗死的影响.方法经右侧颈总动脉将尼龙单丝线栓至大脑中动脉造成永久性缺血模型.经尾静脉及腹腔注射尼莫同,TTC染色、图像分析仪测定脑梗死体积.结果单纯缺血组各时间点脑梗死体积最大,缺血前预防给药组各时间点脑梗死体积最小,缺血后即刻给药组各时间点脑梗死体积介于二者之间.结论小鼠大脑中动脉闭塞后其局灶性脑梗死体积于术后第3天达高峰.缺血前预防给药组、缺血后即刻给药,尼莫同均可使梗死体积减少.     

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。     

小鼠大脑中动脉缺血再灌注后缺血区及周边区星形胶质细胞的变化

目的 探讨小鼠大脑中动脉缺血再灌注后脑梗死体积、星形胶质细胞(AS)病理形态及其蛋白表达的变化.方法 选取69只成年健康雄性KM小鼠,将小鼠随机分为脑缺血2h再灌注1、4、10、24、48、72 h模型组(n=9)以及假手术组(n=6,仅结扎右侧颈总动脉)和正常组(n=9).采用线栓法制备小鼠大脑中动脉局灶性脑缺血再灌注模型.应用2,3,5-氯化三苯基四氮唑(TTC)染色法观察脑梗死的部位与体积;免疫组化法观察脑缺血中心区与周边区不同再灌注时间点胶质纤维酸性蛋白(GFAP)的表达.结果 缺血再灌注1h开始出现脑梗死灶,且再灌注24 h时梗死体积最大,之后逐渐缩小(F=745.534,P=0.000).小鼠脑缺血再灌注后缺血中心区AS肿胀、肥大进而较快发生凋亡,其GFAP表达水平低于周边区(P＜0.05);而缺血周边区GFAP阳性表达的AS出现反应性活化,进而发生形态学改变;缺血周边区及对侧相应脑组织区域GFAP的表达量均随再灌注时间的延长呈现增加趋势(P＜0.05).结论 AS反应性活化可能是一种缺血后的全脑保护性防御机制,尤其是在缺血周边区,其活化程度影响脑组织的存活与修复,提示在脑缺血再灌注过程中AS反应性活化可能在脑损伤后可塑性形态及功能改变中发挥重要作用.     

Protective role of reactive astrocytes in brain ischemia.

Reactive astrocytes are thought to protect the penumbra during brain ischemia, but direct evidence has been lacking due to the absence of suitable experimental models. Previously, we generated mice deficient in two intermediate filament (IF) proteins, glial fibrillary acidic protein (GFAP) and vimentin, whose upregulation is the hallmark of reactive astrocytes. GFAP(-/-)Vim(-/-) mice exhibit attenuated posttraumatic reactive gliosis, improved integration of neural grafts, and posttraumatic regeneration. Seven days after middle cerebral artery (MCA) transection, infarct volume was 210 to 350% higher in GFAP(-/-)Vim(-/-) than in wild-type (WT) mice; GFAP(-/-), Vim(-/-) and WT mice had the same infarct volume. Endothelin B receptor (ET(B)R) immunoreactivity was strong on cultured astrocytes and reactive astrocytes around infarct in WT mice but undetectable in GFAP(-/-)Vim(-/-) astrocytes. In WT astrocytes, ET(B)R colocalized extensively with bundles of IFs. GFAP(-/-)Vim(-/-) astrocytes showed attenuated endothelin-3-induced blockage of gap junctions. Total and glutamate transporter-1 (GLT-1)-mediated glutamate transport was lower in GFAP(-/-)Vim(-/-) than in WT mice. DNA array analysis and quantitative real-time PCR showed downregulation of plasminogen activator inhibitor-1 (PAI-1), an inhibitor of tissue plasminogen activator. Thus, reactive astrocytes have a protective role in brain ischemia, and the absence of astrocyte IFs is linked to changes in glutamate transport, ET(B)R-mediated control of gap junctions, and PAI-1 expression.     

Knockout of silent information regulator 2 (SIRT2) preserves neurological function after experimental stroke in mice

Sirtuin-2 (Sirt2) is a member of the NAD⁺-dependent protein deacetylase family. Various members of the sirtuin class have been found to be involved in processes related to longevity, regulation of inflammation, and neuroprotection. Induction of Sirt2 mRNA was found in the whole hemisphere after experimental stroke in a recent screening approach. Moreover, Sirt2 protein is highly expressed in myelin-rich brain regions after stroke. To examine the effects of Sirt2 on ischemic stroke, we induced transient focal cerebral ischemia in adult male Sirt2-knockout and wild-type mice. Two stroke models with different occlusion times were applied: a severe ischemia (45 minutes of middle cerebral artery occlusion (MCAO)) and a mild one (15 minutes of MCAO), which was used to focus on subcortical infarcts. Neurological deficit was determined at 48 hours after 45 minutes of MCAO, and up to 7 days after induction of 15 minutes of cerebral ischemia. In contrast to recent data on Sirt1, Sirt2^−/− mice showed less neurological deficits in both models of experimental stroke, with the strongest manifestation after 48 hours of reperfusion. However, we did not observe a significant difference of stroke volumes or inflammatory cell count between Sirt2-deficient and wild-type mice. Thus we postulate that Sirt2 mediates myelin-dependent neuronal dysfunction during the early phase after ischemic stroke.     

Deficiency of PAR4 attenuates cerebral ischemia/reperfusion injury in mice

Stroke is the third leading cause of death in the USA. Antithrombotic therapy targeting platelet activation is one of the treatments for ischemic stroke. Here we investigate the role of one of the thrombin receptors, protease-activated receptor 4 (PAR4), in a mouse transient middle cerebral artery occlusion (MCAO) model. After a 60 min MCAO and 23 h reperfusion, leukocyte and platelet rolling and adhesion on cerebral venules, blood–brain barrier (BBB) permeability, and cerebral edema were compared in PAR4-deficient mice and wild-type mice. Cerebral infarction volume and neuronal death were also measured. PAR4−/− mice had more than an 80% reduction of infarct volume and significantly improved neurologic and motor function compared with wild-type mice after MCAO. Furthermore, deficiency of PAR4 significantly inhibits the rolling and adhesion of both platelets and leukocytes after MCAO. BBB disruption and cerebral edema were also attenuated in PAR4−/− mice compared with wild-type animals. The results of this investigation indicate that deficiency of PAR4 protects mice from cerebral ischemia/reperfusion (I/R) injury, partially through inhibition of platelet activation and attenuation of microvascular inflammation.     

Effects of dexmedetomidine after transient and permanent occlusion of the middle cerebral artery in the rat

Summary. Increased sympathetic tone is a consequence of cerebral ischemia. Although the role of catecholamines in ischemic damage is still unclear, in some experimental ischemia models α₂-adrenergic agonism has proved to be neuroprotective. In the present work we have compared the effects of transient and permanent middle cerebral artery occlusion (MCAO) on the infarct volume, and, also, examined whether a selective α₂-adrenergic receptor agonist, dexmedetomidine (9 μg/kg or 15 μg/kg i.v.), is able to reduce ischemic damage after transient or permanent MCAO in rats. Permanent MCAO led to a significantly larger infarct volume than transient occlusion (p < 0.05). The rats receiving the higher dose of dexmedetomidine were detectected to have smaller (statistically non-significant) infarct volume in the cortex (30.9%) and in the striatum (20.3%) after transient occlusion. Additionally, dexmedetomidine caused significant variations in the physiological parameters. Received December 22, 1999; accepted September 20, 2000     

N‐myc downstream‐regulated gene 2 protects blood–brain barrier integrity following cerebral ischemia

Disruption of the blood‐brain barrier (BBB) following cerebral ischemia is closely related to the infiltration of peripheral cells into the brain, progression of lesion formation, and clinical exacerbation. However, the mechanism that regulates BBB integrity, especially after permanent ischemia, remains unclear. Here, we present evidence that astrocytic N‐myc downstream‐regulated gene 2 (NDRG2), a differentiation‐ and stress‐associated molecule, may function as a modulator of BBB permeability following ischemic stroke, using a mouse model of permanent cerebral ischemia. Immunohistological analysis showed that the expression of NDRG2 increases dominantly in astrocytes following permanent middle cerebral artery occlusion (MCAO). Genetic deletion of Ndrg2 exhibited enhanced levels of infarct volume and accumulation of immune cells into the ipsilateral brain hemisphere following ischemia. Extravasation of serum proteins including fibrinogen and immunoglobulin, after MCAO, was enhanced at the ischemic core and perivascular region of the peri‐infarct area in the ipsilateral cortex of Ndrg2‐deficient mice. Furthermore, the expression of matrix metalloproteinases (MMPs) after MCAO markedly increased in Ndrg2^?/? mice. In culture, expression and secretion of MMP‐3 was increased in Ndrg2^?/? astrocytes, and this increase was reversed by adenovirus‐mediated re‐expression of NDRG2. These findings suggest that NDRG2, expressed in astrocytes, may play a critical role in the regulation of BBB permeability and immune cell infiltration through the modulation of MMP expression following cerebral ischemia.     

Enlarged infarct volume and loss of BDNF mRNA induction following brain ischemia in mice lacking FGF-2

FGF-2, a potent multifunctional and neurotrophic growth factor, is widely expressed in the brain and upregulated in cerebral ischemia. Previous studies have shown that intraventricularly or systemically administered FGF-2 reduces the size of cerebral infarcts. Whether endogenous FGF-2 is beneficial for the outcome of cerebral ischemia has not been investigated. We have used mice with a null mutation of the fgf2 gene to explore the relevance of endogenous FGF-2 in brain ischemia. Focal cerebral ischemia was produced by occlusion of the middle cerebral artery (MCAO). We found a 75% increase in infarct volume in fgf2 knock-out mice versus wild type littermates (P < 0.05). This difference in the extent of ischemic damage was observed after 24 h, and correlated with decreased viability in fgf2 mutant mice following MCA occlusion. Increased infarct volume in fgf2 null mice was associated with a loss of induction in hippocampal BDNF and trkB mRNA expression. These findings indicate that signaling through trkB may contribute to ameliorating brain damage following ischemia and that bdnf and trkB may be target genes of FGF-2. Together, our data provide the first evidence that endogenous FGF-2 is important in coping with ischemic brain damage suggesting fgf2 as one crucial target gene for new therapeutic strategies in brain ischemia.