Further characterisation of a thromboembolic model of stroke in the rat

We have used magnetic resonance imaging (MRI) techniques to characterise a rat model of thromboembolic stroke. The consequences of acute perfusion deficit associated with a middle cerebral artery occlusion (MCAo) by a newly formed thrombus was mapped by interrogation of the tissue oxygenation status using gradient echo methods and production of T2* maps. Final infarct size was subsequently assessed at 24-h post-ischaemia by histology with 2,3,5-triphenyltetrazolium chloride (TTC) staining. Animals displayed an infarct volume of 178.7+/-84.2 mm(3) (mean+/-S.D.) with a large coefficient of variation (47%) and range of values (85.6--265.5 mm(3)). This variability provided us with an opportunity to assess the relationships between early imaging observations and eventual infarct size. For a single cerebral slice, at the centre of the MCA territory, a relationship between the area of reduced T2* at 1 and 2 h post MCAo correlated highly with final lesion area (Spearman rank correlation, r=0.98, P<0.01, n=9). Lesion volumes in the thromboembolic MCAo model were compared with a 120-min occlusion, 22-h reperfusion protocol using an intraluminal thread MCAo approach. For the thromboembolic model, the total lesion volume was found to be smaller (178.7+/-84.2 vs. 243.3+/-50.1 mm(3), mean+/-S.D., Student's t-test P=0.046) and showed a greater variability (coefficient of variations: 47% vs. 21%). These data underline the relative variability of this embolic model and provide important preliminary information regarding the value of early changes in T2* in predicting eventual infarct size.     

MRI of combination treatment of embolic stroke in rat with rtPA and atorvastatin

To test the hypothesis that combination treatment of embolic stroke with rtPA and statins improves the efficacy of thrombolytic therapy in rats. Rats subjected to embolic MCA occlusion (MCAo) were randomized into control (n = 10) and treatment (n = 9) groups. Four hours after MCAo, a combination of rtPA and atorvastatin (treatment) or saline (control) was administered. MRI measurements were performed on all animals at 2 h, 24 h and 48 h after MCAo. The patency of cerebral microvessels was examined using fluorescent microscopy. MRI images showed complete blockage of the right MCA and a reduction of CBF in the territory supplied by the MCA 2 h after MCAo for all animals. By 48 h after stroke, MRI showed that the decreased lesion size, elevated CBF and increased incidence of recanalization were found in treated rats compared with the control rats. The combination treatment significantly increased microvascular patency (16.3 +/- 5.5% vs. 12.4 +/- 3.5%, of field-of-view) and reduced the infarct volume (23.1 +/- 9.6% vs. 38.8 +/- 13.3%, of hemisphere). These data demonstrate that the co-administration of rtPA and atorvastatin 4 h after ischemia is efficacious and is reflected by the MRI indices of recanalization of the MCA, reduction of secondary microvascular perfusion deficits and reduction of the ischemic lesion.     

Effect of early and delayed recanalization on infarct pattern in proximal middle cerebral artery occlusion

BACKGROUND: To investigate the effect of early (<6 h) versus delayed (>6 h) recanalization on infarct pattern in acute middle cerebral artery (MCA) occlusion. METHODS: 35 patients with acute MCA occlusion (M1 segment; symptom onset <6 h) were analyzed. Stroke MRI was performed immediately after admission (day 0), and on days 1 and 7. In addition, vessel status was assessed within 6 h, at 24 h and on day 7. Patients were grouped according to early (相似文献   

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.     

Hypothermia and brain-derived neurotrophic factor reduce glutamate synergistically in acute stroke

Moderate hypothermia and application of brain-derived neurotrophic factor (BDNF) have separately been identified as neuroprotective strategies in experimental cerebral ischemia. To assess their separate and combined effects on striatal glutamate release in the hyperacute phase of stroke, we inserted microdialysis probes into the striatum of rats 2 h before permanent middle cerebral artery occlusion (MCAO). The animals (N = 28) were randomly assigned to one of four treatment strategies commencing 30 min after MCAO: (1) hypothermia at 33 degrees C (n = 7); (2) intravenous BDNF infusion [300 microg/(kg/h) for 2 h, n = 7]; (3) combination of hypothermia and BDNF (n = 7); (4) control group (saline, n = 7). Infarct size at 5 h after MCAO was assessed with the silver-staining method. Total infarct volume was significantly reduced in the hypothermia (202.7 +/- 3.5 mm(3), P = 0.0002) and BDNF group (206.5 +/- 6.9 mm(3), P = 0.0006) as compared to control group (254.4 +/- 9.3 mm(3)). In the combination group, infarct size was further reduced with overall significance in post hoc tests (157.3 +/- 6.2 mm(3), P < 0.0001). Postischemic glutamate concentrations in the control group constantly remained significantly higher than in all other treatment groups. At 255 and 270 min after MCAO, striatal glutamate in the combination group decreased significantly more than in animals treated with hypothermia or BDNF alone.Combining hypothermia and BDNF therapy in the acute stage of ischemia has a synergistic effect in attenuating striatal glutamate release and reducing early infarct size.     

Propentofylline in adult-onset cognitive disorders: double-blind, placebo-controlled, clinical, psychometric and brain mapping studies

In a double-blind, placebo-controlled parallel group trial, the therapeutic efficacy and central effects of propentofylline (HWA 285) - a xanthine derivative with neuroprotective, metabolic, hemorheologic and antithrombotic action - were studied in 190 elderly outpatients with mild to moderate chronic cognitive disturbances (mild dementia, DSM-III-R). They received after a 2-week run-in period (placebo) for 12 weeks either 3 x 300 mg propentofylline or 3 x 1 tablet placebo (given at least 1 h before meals). The verum group (n = 96, age 68 +/- 9) was comparable to the placebo group (n = 94, age 69 +/- 8) in regard to age, height, smoking, consumption of stimulating alcoholic drinks, family and living status. Clinical evaluation by the Gottfries-Brane-Steen (GBS) scale demonstrated a significant superiority of propentofylline over placebo in the total score and the four GBS factors (motor, intellectual, emotional functions and other symptoms) as well as in the clinical global impression and Mini-Mental State. Psychometric measures showed slight and significant improvement in both groups but no intergroup differences. EEG brain mapping was carried out before and after 12 weeks' treatment in the Viennese subsample involving 24 propentofylline and 24 placebo patients. Propentofylline-treated patients exhibited, as compared with placebo-treated ones, a trend towards augmentation of total power, furthermore an increase in relative delta and beta and a decrease in alpha power, an acceleration of the dominant frequency as well as a slowing of the centroid of the combined delta/theta band. The total centroid tended towards acceleration, while the centroid deviation increased significantly. These alterations reflect vigilance changes of the dissociative type and differ from those of the classical nootropics. Clinical and psychometric evaluations demonstrated changes in the same direction as in the total sample, but interdrug differences were not significant. Thus, EEG brain mapping seems to be more sensitive in objectivating central drug effects.     

NXY-059, a novel free radical trapping compound, reduces cortical infarction after permanent focal cerebral ischemia in the rat

Free radicals have gained wide acceptance as mediators of cerebral ischemic injury. It has previously been reported that a spin trap nitrone, alpha-phenyl-N-tert-butyl nitrone (PBN), can reduce infarct volumes in rats subjected to either permanent or transient focal cerebral ischemia. A recent study has demonstrated that NXY-059, a novel free radical trapping nitrone compound, has a neuroprotective effect against transient focal cerebral ischemia. This study was designed to determine the effect of NXY-059 in a rodent model of permanent focal cerebral ischemia. Male spontaneously hypertensive rats were subjected to permanent middle cerebral artery occlusion (MCAO) by placement of a microaneurysm clip on the middle cerebral artery (MCA). Animals were divided into three groups: (1) physiological saline given as a 1 ml/kg i.v. bolus administered 5 min post MCAO followed immediately by a continuous i.v. infusion of 0.5 ml/h of physiological saline for 24 h (n=10); (2) 30 mg/kg, 1 ml/kg, i.v. bolus of NXY-059 dissolved in physiological saline administered 5 min post MCAO followed immediately by a continuous i.v. infusion of 30 mg/kg/h, 0.5 ml/h, of NXY-059 for 24 h (n=9); (3) 60 mg/kg, 1 ml/kg, i.v. bolus of NXY-059 dissolved in physiological saline administered 5 min post MCAO followed immediately by a continuous i.v. infusion of 60 mg/kg/h, 0.5 ml/h, of NXY-059 for 24 h (n=12). Infarction was quantified after a survival period of 24 h. Differences in infarct volume were examined with one-way ANOVA following Dunnet's multiple comparison test. The percentage of cortical infarction in the saline control group was 22.6 +/- 6.8% (mean+/-S.D.) of contra-lateral hemisphere, and in the 30 mg/kg/h NXY-059-treated group was 17.4% +/- 6.8% (NS). Plasma concentration (microM/l) of NXY-059 in the 30 mg/kg/h group was 80.2 +/- 52.2 (n=9), while in the 60 mg/kg/h group plasma concentration (microM/l) of NXY-059 was 391.0 +/- 207.0 (n=10). Infarction in the 60 mg/kg/h NXY-059-treated group was significantly reduced (P=0.009) to 14.5 +/- 5%. Our preliminary data demonstrate that administration of NXY-059 (60 mg/kg/h for 24 h) ameliorates cortical infarction in rats subjected to permanent focal cerebral ischemia with 24 h survival.     

Neuroprotection by 2-h postischemia administration of two free radical scavengers, alpha-phenyl-n-tert-butyl-nitrone (PBN) and N-tert-butyl-(2-sulfophenyl)-nitrone (S-PBN), in rats subjected to focal embolic cerebral ischemia

Oxygen free radical generation may have important secondary damaging effects after the onset of cerebral ischemia. Free radical scavengers have been used successfully in attenuating neuronal damage in the reperfusion period in transient forebrain ischemia. There are limited data on effectiveness in models of focal ischemia. Two free radical scavengers, alpha-phenyl-n-tert-butyl-nitrone (PBN) and N-tert-butyl-(2-sulfophenyl)-nitrone (S-PBN), have been shown to reduce oxidative-stress-induced neuronal injury. Whereas PBN has been demonstrated to reduce infarct volume in focal ischemia, neuroprotection has not been evaluated with S-PBN. The present study was designed to evaluate the neuroprotective effect of PBN and S-PBN compared to vehicle in a focal embolic middle cerebral artery (MCA) cerebral ischemia model in rats. Wistar rats were randomly divided into three groups (n = 10 each group). Animals in the control group received vehicle and those in the treatment groups were treated with PBN or S-PBN (both 100 mg/kg/day x 3 days, intraperitoneally) starting 2 h after the introduction of an autologous thrombus into the right-side MCA. The neurological outcome was observed and compared before and after treatment and between groups. The percentage of cerebral infarct volume was estimated from 2,3, 5-triphenyltetrazolium chloride stained coronal slices 72 h after the ischemic insult. Two-hour postischemia administration of PBN or S-PBN significantly improved neurobehavioral scores at 24 h following MCA embolization (both P < 0.01). The percentage of infarct volume for animals receiving vehicle was 32.8 +/- 9.4%. Two-hour delayed administration of PBN and S-PBN achieved a 35.4% reduction in infarct volume in treatment groups when compared with animals receiving vehicle (PBN vs control, 21.2 +/- 10.9% vs 32.8 +/- 9.4%; P < 0.05; S-PBN vs control, 21.2 +/- 13.1%, (P < 0.05). These data indicate that free radical generation may be involved in brain damage in this model and 2-h delayed postischemia treatment with PBN and S-PBN may have neuroprotective effects in focal cerebral ischemia. As S-PBN does not normally cross the blood-brain barrier, the neuroprotection evident in this study may be explained by entry into the brain via damaged vessels.     

Monofilament intraluminal middle cerebral artery occlusion in the mouse

Abstract

The rat middle cerebral artery (MeA) occlusion model with an intraluminal filament is well characterized with a two hour period ofocclusion in widespread use. The recent availability oftransgenic animals has led to an interest in adapting the MCA model in the mouse. To date the model has not been well characterized in the mouse. We performed the present study to compare different durations of MCA occlusion and to validate new functional assessments in this model. The MCA occlusion model (5-0 filament) was used. Swiss-Webster mice, 24-44 g, were randomly assigned to four groups: one hour of occlusion; two hours of occlusion; three hours of occlusion; or permanent occlusion. At 48 hours post-ischemia, the animals were rated on three neurologic function scales, and then the brains were removed for lesion size determination. Overall, there was a significant difference in lesion volume (p < 0.001) between the groups. In the permanent group of mice, the average lesion volume was 78.41 ± 17.47mm (n = 12); two and three hours of ischemia produced 51.29 ± 29.82 mm3 (n = 11) and 54.85mm3 (n = 13), respectively, significantly different than the one hour group 14.84 ± 31.34 mm3 (n = 11). All three functional scoring systems found significant overall differences between the four groups with our detailed General and Focal scores producing mpre robust between group treatment differences and showing correlation coefficients of r = 0.766 and r = 0.788, respectively to infarct volume. The MCA filament occlusion model can be successfully adapted in the mouse with either two or three hour occlusions producing reliable infarcts. New functional scoring systems unique to the mouse appear to add additional information. [Neural Res 1997; 19: 641-648]     

Talampanel a non-competitive AMPA-antagonist attenuates caspase-3 dependent apoptosis in mouse brain after transient focal cerebral ischemia

Talampanel (IVAX) is a non-competitive AMPA-antagonist has a remarkable neuroprotection in different rodent stroke models. The focal cerebral ischemia in mice was induced by transient (60 min.) MCA occlusion and 48 h reperfusion and treated with talampanel (6 x 2 mg/kg, i.p.). The apoptotic and necrotic cells were analyzed by double immune histochemical staining on confocal laser microscope. The infarct size is decreased significantly by talampanel treatment (from 57.1+/-7.2mm(2) to 18.9+/-2.6 mm(2), p< 0.001). The number of TUNEL-positive cells localized mostly in the border zone of ischemic lesions is significantly decreased after talampanel treatment (from 962+/-13.0 to 604+/-6.9, p < 0.01). A strong, significant reduction of caspase-3 active cells was visualized. Talampanel as a neuroprotective drug candidate has a significant effect in mice transient MCA occlusion model.     

The time course of ischemic damage and cerebral perfusion in a rat model of space-occupying cerebral infarction

We aimed to establish a rat model of space-occupying hemispheric infarction to evaluate potential treatment strategies. For adequate timing of therapy in future experiments, we studied the development of tissue damage, edema formation, and perfusion over time with different MRI techniques. Permanent middle cerebral artery (MCA) occlusion was performed in 32 Fisher-344 rats. Forty-six MRI experiments including diffusion weighted (DW), T2-weighted (T2W), flow-sensitive alternating inversion recovery (FAIR) perfusion-weighted, and T1-weighted (T1W) imaging before and after gadolinium were performed at 1, 3, 8, 16, 24, and 48 h of ischemia. MCA occlusion consistently led to infarction of the complete MCA territory. Mortality was 75%. Lesion volumes as derived from apparent diffusion coefficient (ADC) and T2 maps increased to maximum values of 400+/-48 mm3 at 24 h and 420+/-54 mm3 at 48 h of ischemia, respectively. Midline shift peaked at 24 h. The area with diffusion-perfusion deficit decreased to a minimum at 24 h after onset of ischemia and perfusion of the contralateral hemisphere dropped at the same time point. Leakage of gadolinium through the blood-brain barrier in the entire infarct occurred within 3 h of ischemia. Permanent intraluminal MCA occlusion in Fisher-344 rats is an adequate model for space-occupying cerebral infarction. Rats may benefit from intervention aimed at reducing tissue shift and intracranial pressure (ICP), and at improving cerebral blood flow, if initiated before 24 h after MCA occlusion. The value of treatment modalities depending on an intact blood-brain barrier should be questioned.     

Combined X-ray angiography and diffusion-perfusion MRI for studying stroke evolution after rt-PA treatment in rats

Clinical studies on rt-PA (recombinant tissue-type plasminogen activator) treatment of stroke showed a favorable outcome. However, there are reports of harmful effects of t-PA via the potentiation of excitotoxic injury. We used combined X-ray angiography and MRI imaging to study the balance between the beneficial effect of reperfusion and secondary detrimental effects of rt-PA. Therefore, rats (n=15) were assigned to three groups according to recanalization or lack thereof of the middle cerebral artery (MCA) and rt-PA or saline treatment in an embolic stroke model. Diffusion and perfusion MRI showed that animals had significantly improved perfusion values and final infarct size when recanalization was successful. However, final infarct volumes at 6 h post stroke onset were greater in the rt-PA group compared to controls at comparable perfusion values when the MCA did not recanalize after treatment (67.4+/-5.4 versus 47.7+/-17.9% of ipsilateral hemisphere, P=0.042). Our results demonstrate that the combination of angiography and MR-imaging is useful to further evaluate rt-PA treatment of thromboembolic stroke.     

The effect of C 1 esterase inhibitor on ischemia: reperfusion injury in the rat brain]

BACKGROUND: Despite the current interest in thrombolytic therapy for acute stroke, ischemia-reperfusion injury remains a potentially hazardous complication. The complement system is thought to play a major role in initiating some of the inflammatory events occurring in the reperfusion injury. This study was conducted to explore the effect of C 1 esterase inhibitor (C 1 INH) on the reperfusion injury in rat middle cerebral artery (MCA) occlusion-reperfusion model. METHODS: Twenty-nine male Wistar rats were used. Intraluminal MCA occlusion was performed for 60 minutes. Just before the reperfusion, C 1 INH(50 IU/kg, C 1 INH group, n = 15) or saline (control group, n = 14) was administrated. Forty-eight hours after the reperfusion, infarct volume and myeloperoxidase(MPO) activity of the brain were evaluated. RESULT: Infarct volume and MPO activity were significantly smaller in the C 1 INH group(86.5 +/- 76.8 mm3, 0.38 +/- 0.30 U/g) than in control group(179 +/- 92.8 mm3, 1.37 +/- 0.46 U/g) (p < 0.01). CONCLUSION: The results of this study provided the first evidence that C 1 INH reduced polymorphonuclear leukocytes(PMN) accumulation and reperfusion damage in the brain.     

Neuroprotection and glutamate attenuation by acetylsalicylic acid in temporary but not in permanent cerebral ischemia

To assess the effects of acetylsalicylic acid (ASA) on glutamate and interleukin-6 (IL-6) release in the striatum of rats suffering from cerebral ischemia, we used the microdialysis technique with probes implanted 2 h prior to stroke onset. A total of 36 rats were randomly assigned to either temporary (90 min, n=18) or permanent (n=18) middle cerebral artery occlusion (MCAO). Animals received either a bolus of 40 mg/kg ASA or saline as control 30 min after stroke onset. Permanent MCAO led to large infarct volumes with no differences between treatment with ASA (239.8+/-4.1 mm3) and saline (230.1+/-3.9 mm3, p=0.15). In contrast, ASA therapy in temporary ischemia (87.2+/-6.2 mm3) reduced infarct size significantly compared to placebo (155.6+/-4.8 mm3, p<0.0001). Only in temporary ischemia, ASA application reduced glutamate significantly at the time points 90, 120, and 150 min after MCAO. Pooled post-ischemic microdialysate concentrations of IL-6 in temporary MCAO were significantly higher after ASA treatment (215+/-81 pg/mL, p=0.0297) than in saline-treated rats (80+/-13 pg/mL). In the permanent MCAO group, no difference in IL-6 between the ASA (125+/-21 pg/mL) and saline group (68+/-34 pg/mL) was noted. No differences were seen for c-fos positive neurons in the penumbra and hippocampus between all groups. These results suggest that the neuroprotective effect of ASA is reflected by glutamate attenuation and IL-6 induction even if given after stroke onset, but only if reperfusion is achieved.     

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.     

Modified permanent middle cerebral artery occlusion rat model aiming to reduce variability in infarct size

In animal cerebral infarct experiments, the most important aspect is to produce consistent infarct size and localization. In an attempt to improve the conventional middle cerebral artery (MCA) coagulation technique, we developed a new animal model using a microclip to reduce variability in infarct size. Male Sprague-Dawley rats were subjected to right MCA occlusion. The animals were divided into two groups; conventional MCA occlusion group (Group 1; n = 9) and modified clip occlusion group (Group 2; n = 9). In Group 2, the proximal portion of MCA was occluded by applying a small clip just proximal to the olfactory nerve, and the MCA from the clipped position to the position just proximal to the level of the inferior cerebral vein was electrocoagulated using a bipolar diathermy in the same manner as in Group 1. In other words, the only difference between these two groups was the manner of occlusion of the most proximal portion of the MCA. Rats were killed 24 hours after the stroke-inducing surgery, and infarct volume was determined by an image analysis program following staining with 2,3,5-triphenyltetrazolium chloride. The cortical infarct volumes were 51.0 +/- 13.8% in Group 1 and 46.3 +/- 6.2% in Group 2. The scattering of cortical infarct volume was significantly small in Group 2 (p=0.0176). The differences in scattering of striatal and total infarct volumes did not reach statistical significance. The present results demonstrated that the new MCA occlusion model using a clip significantly reduces the variability in cortical infarct volume, solving the problems of the model using coagulation alone. That permanent MCA occlusion model using a clip is an excellent method that produces more consistent and reproducible infarction.     

Stimulation of the fastigial nucleus enhances EEG recovery and reduces tissue damage after focal cerebral ischemia.

Stimulation of the cerebellar fastigial nucleus (FN) increases CBF but not metabolism and reduces the tissue damage resulting from focal cerebral ischemia. This effect may result from enhancing CBF in the ischemic tissue without increasing local metabolic demands. To test this hypothesis, we studied whether the reduction in tissue damage is restricted to the neocortex, a region in which the CBF increase is independent of metabolism, and whether stimulation of the dorsal medullary reticular formation (DMRF), a treatment that increases both cerebral metabolism and CBF, also protects the brain from ischemia. In halothane-anesthetized Sprague-Dawley rats, the middle cerebral artery (MCA) was occluded either proximally or distally to the lenticulostriate branches. The FN or DMRF were then stimulated for 1 h (50-100 microA; 50 Hz; 1 s on/l s off). Twenty-four hours later, the infarct volume was determined. FN stimulation substantially reduced the size of the infarct, an effect that was greater with distal (-69 +/- 8%; n = 6; p < 0.001; mean +/- SD) than with proximal (-38 +/- 8%; n = 8; p < 0.001) MCA occlusion. The reduction occurred only in neocortex (-43 +/- 9%; p < 0.001) and not in striatum (-16 +/- 21%; p > 0.05). Stimulation of the FN also enhanced recovery of EEG amplitude in the ischemic cortex (+48%; p < 0.003). DMRF stimulation (n = 7) did not affect the stroke size or EEG recovery (p > 0.05). Thus, stimulation of the FN, but not the DMRF, attenuates the damage resulting from focal ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

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.     

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.