Transforming growth factor-alpha acting at the epidermal growth factor receptor reduces infarct volume after permanent middle cerebral artery occlusion in rats.

Transforming growth factor-alpha (TGF-alpha) is a ligand for the epidermal growth factor (EGF) receptor (EGFR), and is more abundant than EGF in the brain. The authors studied whether administration of exogenous TGF-alpha into the brain can protect neurons against ischemia in a model of permanent middle cerebral artery (MCA) occlusion in the rat, and whether any effect of TGF-alpha was mediated by EGFR by administering 4,5-dianilinophthalimide (DAPH), a protein-tyrosine kinase inhibitor with high selectivity for EGFR. Rats received either TGF-alpha (10 or 25 ng), DAPH (100 ng), DAPH plus TGF-alpha (25 ng), or vehicle in the ipsilateral first ventricle. Drugs were administered twice: 30 minutes before and 30 minutes after MCA occlusion, and infarct volume was evaluated 24 hours later. Transforming growth factor-alpha at the dose of 25 ng caused a statistically significant reduction of infarct volume (60%) in relation to ischemic rats administered vehicle. This reduction was no longer seen when TGF-alpha was administered in combination with DAPH. The present results show that TGF-alpha can protect neurons from ischemic damage, and that this effect is mediated by EGFR. It is suggested that activation of EGFR-mediated intracellular signalling pathways contributes to the survival of neural cells susceptible to ischemic injury.     

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.     

Adenosine A(1) receptor antagonist and mitochondrial ATP-sensitive potassium channel blocker attenuate the tolerance to focal cerebral ischemia in rats.

Involvement of adenosine and adenosine triphosphate-sensitive potassium (KATP) channels in the development of ischemic tolerance has been suggested in global ischemia, but has not been studied extensively in focal cerebral ischemia. This study evaluated modulating effects of adenosine A1 receptor antagonist DPCPX (8-cyclopentyl-1,3-dipropylxanthine) and mitochondrial KATP channel blocker 5HD (5-hydroxydecanoate) on the development of tolerance to focal cerebral ischemia in rats. Preconditioning with 30-minute middle cerebral artery occlusion (MCAO) reduced cortical and subcortical infarct volume following 120-minute MCAO (test ischemia) given 72 hours later. The neuroprotective effect of preconditioning was attenuated by 0.1 mg/kg DPCPX given before conditioning ischemia (30-minute MCAO), but no influence was provoked when it was administered before test ischemia. DPCPX had no effect on infarct volume after conditioning or test ischemia when given alone. The preconditioning-induced neuroprotection disappeared when 30 mg/kg 5HD was administered before test ischemia. These results suggest a possible involvement of adenosine A1 receptors during conditioning ischemia and of mitochondrial KATP channels during subsequent severe ischemia in the development of tolerance to focal cerebral ischemia.     

The novel beta-blocker, carvedilol, provides neuroprotection in transient focal stroke.

Increasing evidence supports a role for oxidative stress, proinflammatory cytokines, and apoptosis in the pathophysiology of focal ischemic stroke. Previous studies have found that the multi-action drug, carvedilol, is a mixed adrenergic antagonist, and that it behaves as an antioxidant and inhibits apoptosis. In the current study, the authors investigated whether carvedilol provides protection in focal cerebral ischemia and whether this protection is associated with reduced apoptosis and the downregulation of the inflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha) and interleukin- 1beta (IL-1beta). Male Sprague-Dawley rats were subjected to transient middle cerebral artery occlusion (MCAO) by an intraluminal filament technique. Carvedilol (1, 3, and 10 mg/kg) was injected daily subcutaneously 2 or 4 days before the induction of ischemia. Neurologic scores, infarct volumes, TUNEL staining, and mRNA levels of TNF-alpha and IL-1beta were assessed at 24 hours reperfusion. The effect of carvedilol on microvascular cortical perfusion was studied with continuous laser-Doppler flowmetry. Twenty-four hours after MCAO, carvedilol at all three doses reduced infarct volumes by at least 40% and reduced neurologic deficits on average by 40% compared with vehicle-treated controls when given 2 or 4 days before the induction of ischemia. This protection was not mediated by changes in temperature or blood flow. Treatment with all three dose regimens resulted in fewer TUNEL positive cells compared with controls. At 24 hours reperfusion, carvedilol decreased TNF-alpha and IL-1beta expression by 40% to 50% in the ipsilateral ischemic cortex compared with the contralateral controls. The results of the current study indicate that carvedilol is neuroprotective in focal cerebral ischemia and may protect the ischemic brain by inhibiting apoptosis and attenuating the expression of TNF-alpha and IL-1beta.     

Lack of neuroprotection of inhibitory peptides targeting Jun/JNK after transient focal cerebral ischemia in spontaneously hypertensive rats

In this study, we have assessed the ability of two TAT-fused peptides PYC36D-TAT and JNKI-1D-TAT (JNKI-1 or XG-102), which respectively inhibit jun proto-oncogene (c-Jun) and c-Jun N-terminal kinase (JNK) activation, to reduce infarct volume and improve functional outcome (adhesive tape removal) after transient focal cerebral ischemia in Spontaneously Hypertensive (SH) rats. PYC36D-TAT and JNKI-1D-TAT peptide batches used for experiments were tested in vitro and protected cortical neurons against glutamate excitotoxicity. Rats were treated intravenously with three different doses of PYC36D-TAT (7.7, 76, or 255 nmol/kg), JNKI-1D-TAT (255 nmol/kg), D-TAT peptide (255 nmol/kg), or saline (vehicle control), 10 minutes after reperfusion after 90 minutes of middle cerebral artery occlusion (MCAO). Contrary to other stroke models, no treatment significantly reduced infarct volume or improved functional score measurements compared with vehicle-treated animals when assessed 48 hours after MCAO. Additionally, assessment of the JNKI-1D-TAT peptide, when administered 1 or 2 hours after reperfusion after 90 minutes of MCAO, also did not improve histological or functional outcomes at 48 hours after occlusion. This study is the first to evaluate the efficacy of PYC36D-TAT and JNKI-1D-TAT using the SH rat, which has recently been shown to be more sensitive to AMPA receptor activation rather than to NMDA receptor activation after cerebral ischemia, and which may have contributed to the negative findings.     

经鼻给予VEGF治疗脑缺血/再灌注大鼠的量效关系

目的探讨经鼻给予血管内皮生长因子(VEGF)治疗脑缺血/再灌注损伤大鼠的量效关系。方法48只SD大鼠随机分为四组:低剂量组(100μg/mL)、中剂量组(200μg/mL)、高剂量组(500μg/mL)及盐水对照组(n=12)。通过阻塞大脑中动脉制作大鼠局灶性脑缺血90 m in再灌注损伤模型。缺血后1d、7d和14 d行神经功能评价,14 d动物被麻醉,行组织学检查,应用图像分析系统计算梗死体积、评价血管形成。结果与对照组相比,经鼻给予中剂量VEGF,可明显降低梗死体积,改善神经功能(P<0.01);而低和高剂量组对比于对照组,不能降低脑缺血后大鼠脑梗死体积和改善神经功能(P>0.05)。与对照组相比,经鼻给予中和高剂量VEGF,可增加缺血后脑表面血管形成(P<0.01);而低剂量组对比于对照组,不能促进脑缺血后血管生成(P>0.05)。结论经鼻给予中剂量VEGF可有效降低脑缺血/再灌注损伤大鼠梗死体积,改善神经功能,增加血管密度。因此经鼻给予中等剂量(200μg/mL)VEGF是治疗脑缺血/再灌注损伤的最佳剂量,其可用于进一步评价VEGF作用的有效实验剂量。     

Neuroprotective effect of hyperbaric oxygen therapy monitored by MR-imaging after embolic stroke in rats

The potential neuroprotective effects of hyperbaric oxygen (HBO) were tested in an embolic model of focal cerebral ischemia with partially spontaneous reperfusion. Rats (n = 10) were subjected to embolic middle cerebral artery occlusion (MCAO) and diffusion weighted MRI (DWI) was performed at baseline, 1, 3, and 6 h after MCAO to determine the ADC viability threshold yielding the lesion volumes that best approximated the 2,3,5-triphenyltetrazolium chloride (TTC) infarct volumes at 24 h (experiment 1). For assessment of neuroprotective effects, rats were treated with 100% oxygen at 2.5 atmospheres absolute (ATA, n = 15) or normobaric room air (n = 15) for 60 min beginning 180 min after MCAO (experiment 2). DWI-, perfusion (PWI)- and T2-weighted MRI (T2WI) started within 0.5 h after MCAO and was continued 5 h, 24 h (PWI and T2WI only), and 168 h (T2WI only). Infarct volume was calculated based on TTC-staining at 24 h (experiment 1) or 168 h (experiment 2) post-MCAO. ADC-lesion evolution was maximal between 3 and 6 h. In experiment 2, the relative regional cerebral blood volume (rCBV) of both groups showed similar incomplete spontaneous reperfusion in the ischemic core. HBO reduced infarct volume to 145.3 +/- 39.6 mm3 vs. 202.5 +/- 58.3 mm3 (control, P = 0.029). As shown by MRI and TTC, HBO treatment demonstrated significant neuroprotection at 5 h after embolic focal cerebral ischemia that lasted for 168 h.     

人脐血间充质干细胞静脉移植治疗大鼠局灶性脑缺血的实验研究

目的 探讨来源于人脐血的间充质干细胞经静脉移植治疗大鼠局灶性脑缺血的可行性及其机制.方法 将人脐血间充质干细胞在体外纯化、扩增并经BrdU标记后,经尾静脉移植到局灶性脑缺血大鼠体内,通过神经缺损评分观察移植后大鼠神经行为学改善情况,通过组织学方法观察移植到脑内的人脐血间充质干细胞表达脑源性神经营养因子和缺血灶周围微血管密度变化的情况.结果 人脐血间充质干细胞移植组大鼠的神经缺损评分显著低于对照组(P＜0.05);移植到脑内的人脐血间充质干细胞主要选择性分布于缺血灶周围区域并表达脑源性神经营养因子,移植组大鼠梗死灶周围的微血管密度显著高于对照组(P＜0.01).结论 经静脉注射移植人脐血间充质干细胞能明显促进局灶性脑缺血大鼠的神经行为功能恢复,促进缺血灶周边区微血管增生可能是人脐血间充质干细胞移植治疗局灶性脑缺血的机制之一.     

Broad-spectrum cation channel inhibition by LOE 908 MS reduces infarct volume in vivo and postmortem in focal cerebral ischemia in the rat

Cation channels conduct calcium, sodium and potassium, cations that are likely deleterious in the evolution of focal ischemic injury. We studied the effects of a novel, broad-spectrum inhibitor of several cation channels, LOE 908 MS, on acute ischemic lesion development with diffusion-weighted magnetic resonance imaging (DWI) and on cerebral perfusion with perfusion imaging (PI) in vivo and on cerebral infarct size using 2,3,5-triphenyltetrazolium chloride (TTC) staining postmortem. A total of 18 male Sprague-Dawley rats underwent 90 min of middle cerebral artery occlusion (MCAO) and were randomly and blindly assigned to either LOE 908 MS or vehicle starting 30 min after inducing focal ischemia and continuing for 4 h. Whole-brain DWI and multislice PI were done before initiation of treatment and repeated frequently for the next 3.5 h. DWI-derived lesion volume at 4 h showed a significant difference in favor of the drug treated group (P=0.03), whereas PI-derived perfusion deficit volumes did not significantly differ between the groups. The postmortem infarct volume at 24 h was significantly attenuated in the treated group in comparison to controls (P=0.0001) and neurological score was significantly better in the treated group (P<0.02). Blocking several distinct cation channels with LOE 908 MS significantly reduced infarct size and improved neurological outcome without observable adverse effects in this focal ischemia model.     

Rapid tolerance to focal cerebral ischemia in rats is attenuated by adenosine A1 receptor antagonist.

Two types of ischemic tolerance in the brain, rapid and delayed, have been reported in terms of the interval between the conditioning and test insults. Although many reports showed that delayed-phase neuroprotection evoked by preconditioning is evident after 1 week or longer, there have been a few investigations about rapidly induced tolerance, and the reported neuroprotective effects become ambiguous 7 days after the insults. The authors examined whether this rapid ischemic tolerance exists after 7 days of reperfusion in a rat focal ischemic model, and investigated modulating effects of the adenosine A 1 receptor antagonist DPCPX (8-cyclopentyl-1,3-dipropylxanthine). Preconditioning with 30 minutes of middle cerebral artery occlusion reduced infarct volume 7 days after 180 minutes of subsequent focal ischemia given after 1-hour reperfusion. The rapid preconditioning also improved neurologic outcome. These beneficial effects were attenuated by pretreatment of 0.1 mg/kg DPCPX, which did not influence the infarct volume after conditioning (30 minutes) or test (180 minutes) ischemia when given alone. The results show that preconditioning with a brief focal ischemia induces rapid tolerance to a subsequent severe ischemic insult, the effect of which is still present after 7 days of reperfusion, and that the rapid ischemic tolerance is possibly mediated through an adenosine A 1 receptor-related mechanism.     

Changes in tissue factor and the effects of tissue factor pathway inhibitor on transient focal cerebral ischemia in rats

INTRODUCTION: To determine the contribution of tissue factor (TF) to focal cerebral ischemia/reperfusion injury, we investigated the changes in TF in rat brains with transient focal cerebral ischemia and also assessed the effect of TF pathway inhibitor (TFPI). MATERIALS AND METHODS: Spontaneous hypertensive rats were subjected to 90-min of middle cerebral artery occlusion (MCAO) and then were reperfused for up to 24 h. Immediately after MCAO, recombinant human TFPI (rhTFPI) (50 or 20 microg/kg/min) was administered by means of a continuous intravenous injection for 4.5 h. RESULTS AND CONCLUSIONS: TF immunoreactivity decreased or scattered in the ischemic area after reperfusion, however, an increased TF expression was observed in the microvasculature with the surrounding brain parenchyma and it peaked at 3 to 6 h, which coincided with the start of fibrin formation. On the other hand, total TF protein in ischemic area continued to exist and did not remarkably change until 24 h after reperfusion. At 24 h after reperfusion, the total infarct volume in the group treated with 50 microg/kg/min rhTFPI was significantly smaller than that in the controls (saline). Western blotting and immunohistochemical studies showed that rhTFPI treatment resulted in a decrease of fibrin in the ischemic brains and microvasculature. TF-mediated microvascular thrombosis is thus considered to contribute to focal cerebral ischemia/reperfusion injury. The continuous infusion of rhTFPI until a peak of TF-mediated microvascular thrombosis therefore attenuates the infarct volume by reducing fibrin deposition in the cerebral microcirculation.     

Peripheral and central administration of neuropeptide Y in a rat middle cerebral artery occlusion stroke model reduces cerebral blood flow and increases infarct volume

Recent studies have shown increased immunoreactivity for neuropeptide Y (NPY) within the perilesional cortex following experimental middle cerebral artery occlusion (MCAO) or focal excitotoxic damage. Downregulation of the NPY Y1 receptor gene using an antisense oligodeoxynucleotide produced a doubling of the infarct volume, implying that NPY may mediate neuroprotection against focal ischemia. The effects of treatment with NPY on infarct volume and hemodynamic parameters were investigated in the present study. Adult male Sprague-Dawley rats were anesthetized with sodium pentobarbital to undergo right-sided endovascular MCAO for 2 h. A single dose of NPY was given via intracarotid injection (10 microg/kg) at the beginning of reperfusion, intracisternal injection (10 or 30 microg/kg) at 30 min of ischemia, or intracerebroventricular (i.c.v.) injection (10 or 70 microg/kg) at 30 min of ischemia. Control groups received the vehicle only via the same route. Body temperature was maintained constant, and hemodynamic parameters were monitored during anesthesia. Laser Doppler flowmetry was used to monitor the regional cerebral blood flow (rCBF) during ischemia and reperfusion in some rats. The rats were decapitated on day 3, and their brains were cut into 2-mm thick coronal slices before reaction with a 2% solution of 2,3,5-triphenyltetrazolium chloride to reveal the infarct. Compared to the respective control groups, NPY treatment via any method of administration increased the relative infarct volume. Suppression of rCBF was observed during reperfusion. These results indicate that peripheral or central administration of NPY impairs reperfusion following experimental MCAO and worsens the outcome of focal cerebral ischemia.     

局灶预缺血诱导脑缺血耐受的动物模型

目的　建立一种简便可靠的 SD大鼠局灶性脑缺血预处理模型。方法　将大鼠随机分为 3组 ,分别给予 10 m in大脑中动脉缺血 ( MCAO)预处理 ( PC) ;10 min PC后 2 h MCAO( PC MCAO)及假手术 ( SS)后 2 hMCAO( SS MCAO) ,再灌注 2 2 h后处死 ,观察各组神经功能缺损、梗死体积及脑含水量变化。结果　 PC MCAO组神经功能评分、梗死体积及含水量均明显低于 SS MCAO组 ,PC组无神经功能缺损及梗死灶形成。结论　 2次线栓法建立的大鼠局灶脑缺血预处理模型 ,能有效减轻 MCAO所致的神经损伤 ,操作简便 ,稳定性好 ,是一种研究局灶脑缺血耐受的有用工具。     

骨髓基质细胞静脉移植治疗大鼠短暂性局灶性脑缺血

目的探讨骨髓基质细胞静脉移植治疗大鼠短暂性局灶性脑缺血的可行性及其机制。方法将大鼠骨髓基质细胞在体外纯化、扩增并经BrdU标记后,经尾静脉移植到局灶性脑缺血大鼠体内,通过神经缺损评分观察移植后大鼠神经行为学改善情况,通过组织学方法观察移植到脑内的骨髓基质细胞表达脑源性神经营养因子、缺血灶周围细胞凋亡及脑微血管密度的变化。结果骨髓基质细胞移植组大鼠的神经缺损评分显著低于对照组(P<0.05);移植到脑内的骨髓基质细胞主要选择性分布于缺血灶周围区域并表达BDNF;骨髓基质细胞移植组大鼠梗死灶周围的凋亡细胞明显少于对照组(P<0.01)、微血管密度显著高于对照组(P<0.001)。结论经静脉注射移植骨髓基质细胞能够明显促进局灶性脑缺血大鼠的神经行为功能恢复;抗凋亡及促微血管增生可能是骨髓基质细胞移植治疗局灶性脑缺血的机制之一。     

Postischemic intraventricular administration of FGF-2 expressing adenoviral vectors improves neurologic outcome and reduces infarct volume after transient focal cerebral ischemia in rats.

Fibroblast growth factor (FGF)-2 is a potent neurotrophic and angiogenic peptide. To examine possible protective effects of FGF-2 gene expression against transient focal cerebral ischemia in rats, a replication defective, recombinant adenovirus vector expressing FGF-2, was injected intraventricularly 2 hours after middle cerebral artery occlusion (MCAO). The treatment group showed significant recovery compared with the vehicle-treated groups in terms of serial neurologic severity scores over the 35 days after MCAO. Further, 2,3,5-triphenyltetrazolium chloride staining showed that FGF-2 gene transfer decreased infarct volume by 44% as compared with that in the vehicle-treated groups at 2 days after MCAO. The same tendency of gene transfer effects on infarct volume was confirmed at 35 days after MCAO with hematoxylin/eosin staining. Enzyme-linked immunosorbent assay revealed that FGF-2 concentration was increased significantly at 2 days after MCAO, not only in cerebrospinal fluid but also in cerebral substance in the lesioned and treated animals. These results suggested that FGF-2 gene transfer using these adenoviral vectors might be a useful modality for the treatment of occlusive cerebrovascular disease even after the onset of stroke.     

Treadmill training effects on neurological outcome after middle cerebral artery occlusion in rats

BACKGROUND: Treadmill training is used for promoting rhythmical vigorous walking and for task-related training in patients with stroke. The neurological impact of treadmill training has not been established. The present investigation is aimed at (1) examining neurological changes over a four-week period after middle cerebral artery occlusion (MCAO) in rats and (2) assessing the impact of one-week, two-week and four-week treadmill training in MCAO rats. METHODS: Male Sprague-Dawley rats were subjected to 60-minute right MCAO. All rats were randomly assigned to one of seven groups. Infarct volume and neurological score were measured. RESULTS: Rats sacrificed 24 hours post MCAO had the largest infarct volumes (171.4 +/- 14.4 mm3) and the highest neurological score (median: 2, range: 1-3). We noted that without treadmill training, infarct sizes and neurological score diminished with time. Treadmill training for at least one week further reduced infarct volume and significantly improved neurologic function in MCAO rats. CONCLUSION: Treadmill training after focal cerebral ischemia significantly improves neurological outcome in MCAO rats. Treadmill training may be beneficial for ischemic brain recovery.     

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.     

Effects of RSR13, a synthetic allosteric modifier of hemoglobin, alone and in combination with dizocilpine, on outcome from transient focal cerebral ischemia in the rat

This study examined the effect of a pharmacologically induced rightward shift in the partial pressure of oxygen at which 50% of hemoglobin is saturated (P50) on outcome from transient focal cerebral ischemia in the rat. Halothane anesthetized rats (n=20 per group) were given saline or a single 15-min infusion of 150 mg/kg RSR13 (2-[4-[[3,5-dimethylanilino) carbonyl]methyl]phenoxy]-2-methylproprionic acid) intravenously before or 30 min after onset of 75 min of middle cerebral artery filament occlusion (MCAO). Seven days later, severity of hemiparesis and cerebral infarct size were examined. RSR13 alone did not significantly improve outcome. Conscious normothermic rats (n=12 per group) were also given RSR13 (150 mg/kg) or 0.9% NaCl intravenously and subjected to 75 min of MCAO with 7 days of recovery. Again, RSR13 alone did not significantly reduce infarct size or improve neurologic score. A dose-response curve for dizocilpine (MK-801) was then constructed in conscious normothermic rats subjected to 75 min of MCAO. Dizocilpine (0.5 mg/kg i.v.) caused a 90% reduction in mean infarct size while 0.25 mg/kg reduced infarct size by 48%. Other rats were then subjected to 75 min of MCAO after being given dizocilpine (0.25 mg/kg i.v.; n=18) or RSR13 (150 mg/kg i.v. )+dizocilpine (0.25 mg/kg i.v.; n=15). RSR13+dizocilpine resulted in smaller cortical infarct volume (8+/-14 mm3 vs. 34+/-37 mm3, p<0.02) and total cerebral infarct volume (46+/-28 mm3 vs. 81+/-60 mm3, p<0. 05) compared to dizocilpine alone, respectively. We conclude that a pre-ischemic peak increase in P50 of approximately 25 mmHg alone is insufficient to reduce focal ischemic injury, but may be advantageous when used in conjunction with other neuroprotective agents.     

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.     

Neuroprotection in ischemic stroke--combination drug therapy and mild hypothermia in a rat model of permanent focal cerebral ischemia

We have recently demonstrated marked neuroprotective efficacy of a combination therapy with magnesium (calcium- and glutamate-antagonist), tirilazad (antioxidant) and mild hypothermia (MTH) in a rat model of transient focal cerebral ischemia. In the present study, we investigated MTH under conditions of permanent focal cerebral ischemia. In part I, 20 Sprague-Dawley rats were subjected to 6 h of permanent, laser-Doppler flowmetry (LDF) controlled middle cerebral artery occlusion (MCAO). Drugs were administered 30 min before and 1 h after MCAO. Hypothermia (33 degrees C) was maintained for 2 h. Infarct size was planimetrically determined after 6 h. In part II, 29 rats were assigned to the same treatment arms and subjected to 7 days of permanent MCAO. Neurological deficits and body weight were assessed daily. Infarct size was determined on day 7. In part I, MTH significantly reduced infarct formation by 52% after 6 h. In part II, high mortality within the first 3 days was observed in both groups. Treated animals showed a significantly better postoperative weight gain on day 7 and neurological recovery on days 6 and 7 compared to controls without significant differences in infarct volume. MTH seems to exert its neuroprotective properties even in a setting of permanent cerebral ischemia. High mortality and absence of infarct reduction after 7 days might be due to model limitations. Neurological recovery, the most important clinical outcome parameter, is significantly improved in 7-day survivors. Significant neuroprotection under conditions of permanent ischemia and former promising results in transient ischemia justify further investigations of MTH.