Expression of a glutamate transporter subtype, EAAT4, in the developing human cerebellum

The effect of tumor necrosis factor binding protein (TNFbp) was studied in mice subjected to a permanent middle cerebral artery occlusion (MCAO). TNFbp is a dimeric form of the type I soluble TNF receptor linked to polyethylene glycol (TNFbp), and binds and inhibits TNF-alpha. TNFbp produced a significant reduction in the cortical infarct volume (22.6 +/- 3.5 mm3 immediately after MCAO; 25.2 +/- 2.4 mm3 1 h after MCAO) compared with vehicle-treated animals (30.3 +/- 3.7 mm3 immediately post MCAO; 31 +/- 3.7 mm3 1 h after MCAO (mean +/- S.D.) when administered intracranially up to 60 min post-occlusion. The neuroprotective effect of TNFbp was sustained in mice for 2 weeks after MCAO. DNA fragmentation at the margin of the cortical infarcts was dramatically reduced in mice treated with TNFbp whereas all control animals showed consistent and obvious DNA fragmentation 2 weeks after MCAO. TNFbp could have therapeutic value for the treatment of ischemic stroke if the problem of delivery to brain can be overcome.     

Post-treatment of transient focal cerebral ischemia in rats with the novel cerebrovascular-selective Ca2+ channel antagonist (+/-)-(E)-1-(3-fluoro-6,11-dihydrodibenz[b,e]-oxepine-11-yl)-4-(3-pheny l-2-propenyl)-piperazine dimaleate

The efficacy of post-ischemic treatment with AJ-3941 ((+/-)-(E)-1-(3-fluoro-6,11-dihydrodibenz[b,e]-oxepine-11-yl )-4-(3-phenyl-2- propenyl)-piperazine dimaleate, CAS 143110-70-7), a cerebrovascular selective Ca2+ channel antagonist, on brain infarction induced by focal ischemia-reperfusion in rats was evaluated. Focal ischemia was induced by transient occlusion of middle cerebral artery (MCA) with a 3-0 nylon monofilament for 90 min. One day after MCA occlusion (MCAo), brain infarct size was determined by measuring 2,3,5-triphenyltetrazonium chloride-negative stained area of the serial brain sections. The development of cerebral infarction was observed in both regions of cortex and subcortex, such as striatum, caudatum, putamen, hippocampus and corpus callosum. Post-ischemic treatment with AJ-3941 (1 or 3 mg/kg p.o., 10 min and 3 h after the occlusion) significantly reduced the infarct size and volume in the ipsilateral hemisphere in a dose-dependent manner, compared to the solvent control. The reducing effect was observed mainly in the cortical region, and a significant reduction of the subcortical infarct volume was found at the higher dose (3 mg/kg). Post-ischemic treatment with the thromboxane A2 synthetase inhibitor, sodium ozagrel (150 micrograms/kg/min i.v. infusion, between 1 h and 24 h after the MCAo) did not reduce the infarct volume in the hemisphere after ischemia-reperfusion. AJ-3941 had only minimum effect on the elevation of body temperature during ischemia-reperfusion. These results indicate that post-ischemic treatment with AJ-3941 may ameliorate the brain injury after the transient focal cerebral ischemia, and they suggest that AJ-3941 has beneficial effects for treatment of ischemic cerebral damage, such as stroke.     

Intraventricular brain-derived neurotrophic factor reduces infarct size after focal cerebral ischemia in rats

Brain-derived neurotrophic factor (BDNF), acting through the high-affinity receptor tyrosine kinase (TrkB), is widely distributed throughout the central nervous system and displays in vitro trophic effects on a wide range of neuronal cells, including hippocampal, cerebellar, and cortical neurons. In vivo, BDNF rescues motorneurons, hippocampal, and substantia nigral dopaminergic cells from traumatic and toxic brain injury. After transient middle cerebral artery occlusion (MCAO), upregulation of BDNF-mRNA in cortical neurons suggests that BDNF potentially plays a neuroprotective role in focal cerebral ischemia. In the current study, BDNF (2.1 micrograms/d) in vehicle or vehicle alone (controls) was delivered intraventricularly for 8 days, beginning 24 hours before permanent middle cerebral artery occlusion by intraluminal suture in Wistar rats (n = 13 per group). There were no differences in physiological variables recorded during surgery for the two groups. Neurological deficit (0 to 4 scale), which was assessed on a daily basis, improved in BDNF-treated animals compared with controls (P < 0.05; analysis of variance and Scheffe's test). There were no significant differences in weight in BDNF-treated animals and controls during the experiment. After elective killing on day 7 after MCAO, brains underwent 2,3,5-triphenyltetrazolium chloride staining for calculation of the infarct volume and for histology (hematoxylin and eosin and glial fibrillary acid protein). The mean total infarct volume was 83.1 +/- 27.1 mm3 in BDNF-treated animals and 139.2 +/- 56.4 mm3 in controls (mean +/- SD; P < 0.01, unpaired, two-tailed t-test). The cortical infarct volume was 10.8 +/- 7.1 mm3 in BDNF-treated animals and 37.9 +/- 19.8 mm3 in controls (mean +/- SD; P < 0.05; unpaired, two-tailed t-test), whereas ischemic lesion volume in caudoputaminal infarction was not significantly different. These results show that pretreatment with intraventricular BDNF reduces infarct size after focal cerebral ischemia in rats and support the hypothesis of a neuroprotective role for BDNF in stoke.     

Rapid disappearance of zinc positive terminals in focal brain ischemia

The study was undertaken to determine if the levels of vesicular zinc in neuronal terminals would decrease in response to focal brain ischemia. The middle cerebral artery was occluded distal to the striatal branches in male spontaneously hypertensive rats. At 7, 15, 30, 45, 60, 90, 120 min; 3, 6, 12, 24, 48 h and 7 days later the animals were sacrificed and the brains were stained for zinc-sulfides, cell bodies and AChE-positive cholinergic fibers. The density of zinc positive terminals significantly decreased in the neocortical ischemic zone 7 min after middle cerebral artery occlusion (MCAO). In the neocortical layers II and III most zinc positive neuronal terminals disappeared at 7 min after MCAO whereas the zinc positive terminals in layers V and VI remained positive at least 2 h. Beginning at 1 h after MCAO and progressing to 24 h a significant decrease in the density of zinc positive terminals was observed in the dorsolateral striatum, and ventrobasal thalamic nucleus, both major projection areas of the sensorimotor cortex. The disappearance of zinc positive neuronal terminals in the ischemic neocortex and related areas, is most likely due to a neuronal release of vesicular zinc in response to hypoxia. The high extracellular concentration of zinc is thought to be both neuroprotective by blocking the NMDA receptor and neurotoxic by activating neuronal influx of Ca2+ through voltage gated calcium channels. It seems evident that the latter effect of zinc is contributing to the neuronal death in focal brain ischemia.     

Prolongation and enhancement of postischemic c-fos expression after fasting

BACKGROUND AND PURPOSE: A rapid but transient expression of c-fos after cerebral ischemia has been extensively documented. However, the mechanism of this induction and whether induction of c-fos is neuroprotective or detrimental to the brain after ischemia is presently not clear. Fasting before transient cerebral ischemia has been shown to reduce delayed neuronal necrosis and infarct volume. The purpose of the present study was to examine the effect of preischemic fasting for 24 hours on the expression of c-fos after transient focal cerebral ischemia. METHODS: Focal cerebral ischemia was induced by temporary occlusion of the right middle cerebral artery and both common carotid arteries for 60 minutes. Male Long-Evans rats weighting 250 to 300 g were randomly divided into two groups: fed (control group) and food deprived for 24 hours (fasted group) before ischemic surgery. Infarct volumes were measured on the basis of triphenyltetrazolium chloride-delineated infarct areas, and plasma glucose levels were determined by the glucose oxidase method. Temporal and spatial expression of c-fos was assessed by Northern blot analysis, in situ hybridization, and immunohistochemistry. RESULTS: Fasting for 24 hours before 60 minutes of ischemia resulted in a 26.6% decrease in preischemic plasma glucose levels and a 74.5% reduction in infarct volumes in the fasted group compared with the control group. A rapid but transient induction of c-fos mRNA was observed in the ischemic cortex in control animals after 60 minutes of ischemia. Fasting not only prolonged but also enhanced the intensity of c-fos expression in the ischemic cortex. Regional c-fos expression was also different between these two groups. CONCLUSIONS: The results support the contention that c-fos expression may be compatible with its purported neuroprotective role in selected experimental paradigms. The signaling mechanisms underlying the effect of fasting and subsequent lowering of plasma glucose levels on postischemic c-fos expression remain to be explored.     

Reduction of ischemic brain injury by topical application of glial cell line-derived neurotrophic factor after permanent middle cerebral artery occlusion in rats

BACKGROUND AND PURPOSE: Glial cell line-derived neurotrophic factor (GDNF) plays important roles in the survival and recovery of some mature neurons under pathological conditions. However, the effect of GDNF in ameliorating ischemic brain injury has not been well documented. Therefore, we investigated a possible effect of GDNF on the changes of infarct size, brain edema, DNA fragmentation, and immunoreactivities for caspases after permanent middle cerebral artery occlusion (MCAO) in rats. METHODS: For the estimation of ischemic brain injury, we calculated the infarct size of MCA region and also measured the brain water content as edema formation at 24 hours after the MCAO. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin in situ nick labeling (TUNEL) staining was performed for the detection of DNA fragmentation. Immunoreactivities for caspase-1 (ICE), caspase-2 (Nedd-2), and caspase-3 (CPP32) were stained. RESULTS: Both infarct size and brain edema after permanent MCAO were significantly reduced by topical application of GDNF (48% and 30% decreases, P=0.01). TUNEL staining and immunoreactivities for caspases were markedly induced at 12 hours after permanent MCAO in the vehicle-treated animals. However, the spatial distribution of those immunohistochemically positive cells was dissociative in each caspase. Induction of TUNEL staining and immunoreactivities for caspases-1 and -3 was greatly reduced with GDNF treatment, whereas the reduction of caspase-2 staining was only minimum. CONCLUSIONS: These data suggest that the reduction of infarct size and brain edema by GDNF was greatly associated with the reduction of DNA fragmentation and apoptotic signals predominantly through caspases-1 and -3 cascades.     

Immunologic tolerance to myelin basic protein decreases stroke size after transient focal cerebral ischemia

Immune mechanisms contribute to cerebral ischemic injury. Therapeutic immunosuppressive options are limited due to systemic side effects. We attempted to achieve immunosuppression in the brain through oral tolerance to myelin basic protein (MBP). Lewis rats were fed low-dose bovine MBP or ovalbumin (1 mg, five times) before 3 h of middle cerebral artery occlusion (MCAO). A third group of animals was sensitized to MBP but did not survive the post-stroke period. Infarct size at 24 and 96 h after ischemia was significantly less in tolerized animals. Tolerance to MBP was confirmed in vivo by a decrease in delayed-type hypersensitivity to MBP. Systemic immune responses, characterized in vitro by spleen cell proliferation to Con A, lipopolysaccharide, and MBP, again confirmed antigen-specific immunologic tolerance. Immunohistochemistry revealed transforming growth factor beta1 production by T cells in the brains of tolerized but not control animals. Systemic transforming growth factor beta1 levels were equivalent in both groups. Corticosterone levels 24 h after surgery were elevated in all sham-operated animals and ischemic control animals but not in ischemic tolerized animals. These results demonstrate that antigen-specific modulation of the immune response decreases infarct size after focal cerebral ischemia and that sensitization to the same antigen may actually worsen outcome.     

Induction of ischemic tolerance following brief focal ischemia in rat brain

The objective of this study was to determine whether brief focal ischemia induces ischemic tolerance in rat brain. Focal ischemia was produced in Wistar rats by occluding the middle cerebral artery (MCA) for 20 min at a distal site. Following recovery for 24 h, the animals were subjected to a 10-min episode of forebrain ischemia using a combination of bilateral carotid artery occlusion and systemic hypotension. Histologic injury, assessed after a survival period of 3-4 days, consisted of selective neuronal necrosis bilaterally in cerebral cortex, striatum, hippocampus, and thalamus superimposed upon a small cortical infarct adjacent to the site of MCA occlusion. However, the intensity of neuronal necrosis in the MCA territory of the neocortex ipsilateral to MCA occlusion was markedly less than that in the contralateral MCA cortex. In contrast, the extent of neuronal necrosis in subcortical structures was similar in both hemispheres. Unexpectedly, animals in which the MCA was manipulated, but not occluded, also exhibited a marked reduction of neuronal necrosis in the ipsilateral MCA neocortex following forebrain ischemia. However, in animals with craniotomy alone, forebrain ischemia caused a similar extent of neuronal necrosis in the MCA neocortex of both hemispheres. Transient occlusion of the MCA induced the focal expression of the 72-kDa heat-shock protein (hsp72) in the MCA territory of the neocortex. Limited expression of hsp72 was also detected following sham occlusion, but not after craniotomy alone. These results demonstrate focal induction of ischemic tolerance in rat neocortex that may be related to expression of heat-shock proteins.     

Suppressive effects of recombinant human monokine induced by IFN-gamma (rHuMig) chemokine on the number of committed and primitive hemopoietic progenitors in liquid cultures of CD34+ human bone marrow cells

A novel group of antioxidant compounds, the pyrrolopyrimidines, has been discovered recently. Many of these possess significantly improved oral bioavailability (56-70% in rats), increased efficacy and potency in protecting cultured neurons against iron-induced lipid peroxidative injury and as much as a 5-fold increase in brain uptake compared with the 21-aminosteroid antioxidant compound, tirilazad mesylate (U-74006F), described earlier. They appear to quench lipid peroxidation reactions by electron-donating and/or radical-trapping mechanisms. Several compounds in the series, such as U-101033E and U-104067F, demonstrate greater ability than tirilazad to protect the hippocampal CA1 region in the gerbil transient (5-min) forebrain ischemia model. Delaying treatment until 4 hr after the ischemic insult still results in significant CA1 neuronal protection. U-101033E is still effective in salvaging a portion of the CA1 neuronal population when the ischemic duration is extended to 10 min. In addition, U-101033E has been found to be protective in the context of focal cerebral ischemia, reducing infarct size in the mouse permanent middle cerebral artery occlusion model, in contrast to tirilazad which is minimally effective. These results suggest that antioxidant compounds with improved brain parenchymal penetration are better able to limit certain types of ischemic brain damage than those which are localized in the cerebral microvasculature. However, the activity of U-101033E in improving early post-traumatic recovery in mice subjected to severe concussive head injury is similar to that of tirilazad. Last, the oral bioavailability of many pyrrolopyrimidines suggests that they may be useful for certain chronic neurodegenerative disorders in which lipid peroxidation plays a role.     

Regional CBF in apolipoprotein E-deficient and wild type mice during focal cerebral ischemia

Apolipoprotein E-(apoE) deficient mice exhibit hypercholesterolemia, accelerated atherosclerosis and increased infarct size after middle cerebral artery occlusion (MCAO). This study examined whether worsened ischemic outcome is attributable to effects of apoE deficiency on cerebral circulation. Wild type and apoE-deficient mice underwent MCAO and autoradigraphic measurement of cerebral blood flow. Circle of Willis anatomy was examined in non-ischemic animals. Both groups exhibited similar reduction in blood flow. Both groups had 100% incidence of filling of the anterior communicating artery. The posterior communicating artery (PcomA) filled in 70% of wild type and 80% of apoE-deficient mice. Both groups had considerable variability in relative sizes of the PcmA. This study indicates that worsened outcome from MCAO of apoE-deficient mice is not attributable to any detectable vascular effects and offers validity to use of apoE-deficient mice for study of apoE as a factor in cerebral ischemic pathophysiology.     

Secondary osteoporosis and the risk of vertebral deformities in women

Recent reports have indicated that large-dose opiate anesthesia can increase neuronal injury in rats subjected to forebrain ischemia. However, most episodes of cerebral ischemia in the operating room setting are focal in nature, and the influence of large-dose opioid administration on the tolerance of the brain to focal cerebral ischemia has not been studied. Accordingly, we undertook the present study to evaluate the effect of fentanyl administration on outcome after focal cerebral ischemia. Three groups of fasted Wistar-Kyoto rats (awake, fentanyl, and isoflurane groups; n = 20 per group) were anesthetized with isoflurane (2.5% end-tidal). Pericranial temperature was servocontrolled at 37.0 degrees C. After surgical preparation fentanyl 50 microg/kg was administered IV over 10 min in the fentanyl group. Thereafter, an infusion was established at a rate of 50 microg x kg(-1) x h(-1). The end-tidal concentration of isoflurane was then reduced to 1.1%, one minimum alveolar anesthetic concentration (1 MAC) in all groups. Occlusion of the middle cerebral artery was achieved by advancing a 0.25-mm filament into the anterior cerebral artery via the common carotid artery. In the fentanyl and awake groups, isoflurane administration was then discontinued. In the isoflurane group, isoflurane anesthesia was maintained at 1.0 MAC. After 90 min of focal ischemia, the filament was removed, and the animals were allowed to recover. Seven days later, the volume of cerebral infarction in the animals was determined by image analysis of hematoxylin and eosin-stained coronal brain sections. There was no difference in the infarct volume between the fentanyl and awake groups. The infarct volume was the least in the isoflurane group. The results confirm the ability of isoflurane to reduce brain injury caused by focal cerebral ischemia. Fentanyl neither increased nor decreased brain injury compared with the awake unanesthetized state. IMPLICATIONS: Fentanyl is commonly used in surgical procedures in which there is a substantial risk of focal cerebral ischemia. Fentanyl did not affect cerebral injury produced by focal ischemia in the rat. The data suggest that, in doses that produce respiratory depression and muscle rigidity, fentanyl does not reduce the tolerance of the brain to a focal ischemic insult.     

Carbachol-induced inositol phosphate formation in rat striatum is mediated by both M1 and M3 muscarinic receptors

We used in situ hybridization to localize the long-term changes in ornithine decarboxylase (ODC) expression after a 90 min occlusion of the middle cerebral artery (MCAO) in the rat. The ODC mRNA was induced in the ipsilateral dentate gyrus (DG) and throughout the ischemic cortex at 12 h and still at 3 days after reperfusion. The induction was blocked by an N-methyl-D-aspartate (NMDA) receptor antagonist suggesting that ODC induction is NMDA receptor-mediated. The long-lasting up-regulation detected in regions where no cellular damage usually occurs, favors the hypothesis that ODC expression does not contribute to neuronal death after stroke.     

Transient middle cerebral artery occlusion by intraluminal suture: II. Neurological deficits, and pixel-based correlation of histopathology with local blood flow and glucose utilization

We conducted a pixel-based analysis of the acute hemodynamic and metabolic determinants of infarctive histopathology in a reproducible model of temporary (2-hour) middle cerebral artery occlusion (MCAO) produced in rats by an intraluminal suture. Three-dimensional averaged image data sets of local cerebral blood flow (LCBF) and glucose utilization (LCMRglc) acquired in the companion study (Belayev et al., 1997) either at the end of a 2-hour period of MCAO or after 1 hour of recirculation were comapped (using digitized atlas-templates) with data sets depicting the frequency of histological infarction in a matched animal group (n = 8) in which 2 hours of MCAO was followed by 3-day survival, sequential neuro behavioral examinations, and perfusion-fixation and paraffin-embedding of brains for light-microscopic analysis. All rats developed marked postural-reflex and forelimb-placing deficits at 60 minutes of MCAO, signifying high-grade ischemia. Tactile placing deficits persisted during the 72-hour observation period while visual placing and postural-reflex abnormalities variably improved. Comapping of LCBF and histopathology showed that in those pixels destined to undergo infarction, LCBF measured at 2 hours of MCAO showed a sharp distributional peak centered at 0.14 mL/g/min. In 70% of pixels destined to infarct, LCBF at 2 hours of MCAO was 0.24 mL/g/min or below, and in 89% LCBF was below 0.47 mL/g/min (the upper limits of the ischemic core and penumbra, respectively, as defined in the companion study [Belayev et al., 1997]). Local cerebral glucose utilization measured at approximately 1 hour after 2 hours of MCAO was distributed bimodally in the previously ischemic hemisphere. The major peak, at 22 mumol/100g/min, coincided exactly with the distribution peak of pixels destined to undergo infarction, while in pixels with a zero probability of infarction, LCMRglc was higher by 12 to 13 mumol/100g/min. These results indicate that local blood flow at 2 hours of MCAO is a robust predictor of eventual infarction. Pixels with ischemic-core levels of LCBF (0% to 20% of control) have a 96% probability of infarction, while the fate of the penumbra is more heterogeneous: below LCBF of 0.35 mL/g/min, the probability of infarction is 92%, while approximately 20% pixels in the upper-penumbral LCBF range (30% to 40% of control) escape infarction. Our data strongly support the view that the likelihood of infarction within the ischemic penumbra is highly influenced by very subtle differences in early perfusion.     

Attenuation of p53 expression protects against focal ischemic damage in transgenic mice

Apoptosis or programmed cell death may be involved in neuronal death in the cerebral cortex after a permanent focal ischemic insult. Studies indicate that protein p53 is a major determinant of the cellular mechanism that leads to programmed cell death. Wild-type C57 mice and two groups of transgenic C57 mice, one homozygous and the other heterozygous for a p53 null gene, were subjected to middle cerebral artery occlusion. As expected, the wild-type mice had a large, consistent infarct volume (22.11 +/- 4.59 mm3; n = 10). Both transgenic groups had significantly less ischemic damage than the wild-type control group. However, unexpectedly, the heterozygous group had the least amount of ischemic damage (16.12 +/- 1.71 mm3, n = 11; 27% reduction in infarct size). The ischemic damage in the homozygous group (18.72 +/- 3.48 mm3, n = 9) was significantly less than in the wild-type control (15% reduction in infarct size) but significantly more than in the heterozygous group. Thus, although the absence of p53 expression was protective, greater protection was afforded by reduced expression of p53. These data suggest that attenuated p53 expression may be protective after an ischemic event.     

Cathepsin B and middle cerebral artery occlusion in the rat

Lysosomal proteases, although tightly regulated under physiological conditions, are known to contribute to cell injury after various forms of tissue ischemia have occurred. Because cathepsin B is a prominent lysosomal protease found in brain parenchyma, the authors hypothesized that it may contribute to neuronal cell death after focal cerebral ischemia. The authors measured the expression and spatial distribution of cathepsin B within the ischemic brain in 43 animals by means of immunohistochemical analysis in a rat model of transient middle cerebral artery (MCA) occlusion. Cathepsin B activity was also measured within specific ischemic brain regions by using an in vitro assay (22 animals). In addition, the authors tested the therapeutic effect of preischemic intraventricular administration of stefin A, a cysteine protease inhibitor, on the volume of cerebral infarction after transient MCA occlusion (15 animals). Increased cathepsin B immunoreactivity was detected exclusively within the ischemic neurons after 2 hours of reperfusion following a 2-hour MCA occlusion. Cathepsin B immunolocalization in the ischemic region decreased by 24 hours of reperfusion, but then increased by 48 hours of reperfusion because the infarct was infiltrated by inflammatory cells. Increased immunolocalization of cathepsin B in the inflammatory cells located in the necrotic infarct core continued through 7 days of reperfusion. Cathepsin B enzymatic activity was significantly increased in the ischemic tissue at 2, 8, and 48 hours, but not at 24 hours of reperfusion after 2 hours of MCA occlusion. Continuous intraventricular infusion of stefin A, before 2 hours of MCA occlusion (15 animals), significantly reduced infarct volume compared with control animals (12 animals): the percentage of hemispheric infarct volume was 20+/-3.9 compared with 33+/-3.5 (standard error of the mean; p = 0.025). These data indicate that neuronal cathepsin B undergoes increased expression and activation within 2 hours of reperfusion after a 2-hour MCA occlusion and may be a mechanism contributing to neuronal cell death. Intraventricular infusion of stefin A, an inhibitor of cathepsin B, significantly reduces cerebral infarct volume in rats.     

Blockade of adenosine A2A receptors by SCH 58261 results in neuroprotective effects in cerebral ischaemia in rats

Blockade of adenosine receptors can reduce cerebral infarct size in the model of global ischaemia. Using the potent and selective A2A adenosine receptor antagonist, SCH 58261, we assessed whether A2A receptors are involved in the neuronal damage following focal cerebral ischaemia as induced by occluding the left middle cerebral artery. SCH 58261 (0.01 mg/kg either i.p. or i.v.) administered to normotensive rats 10 min after ischaemia markedly reduced cortical infarct volume as measured 24 h later (30% vs controls, p < 0.05). Similar effects were observed when SCH 58261 (0.01 mg/kg, i.p.) was administered to hypertensive rats (28% infarct volume reduction vs controls, p < 0.05). Neuroprotective properties of SCH 58261 administered after ischaemia indicate that blockade of A2A adenosine receptors is a potentially useful biological target for the reduction of brain injury.     

Basic performance of a miniature intraventricular axial pump

Lubeluzole is a neuroprotective compound in the final stages of clinical evaluation. We evaluated the effects of intravenous followed by intraperitoneal doses of lubeluzole on histological outcome after reversible tandem middle cerebral/common carotid artery occlusion in Long-Evans rats, with particular emphasis on the time window of efficacy. Lubeluzole, started 15 min after the onset of ischemia, had no adverse physiological or behavioral effects and reduce maximal infarct volume produced by 120 min or more of arterial occlusion by approximately 50%, from 143.2 +/- 11.8 mm3 (p < 0.05). Lubeluzole did not prolong the duration of middle cerebral artery occlusion which could be tolerated before histological damage occurred. Lubeluzole was still effective if started 30 min after the onset of ischemia (34% reduction of maximal infarct volume; p < 0.05), but not after delays of 60 or 120 min. we conclude that lubeluzole has promise as a neuroprotective drug, particularly for more severe strokes, but must be started very rapidly after the onset of ischemia to be effective.     

A novel endothelin antagonist, A-127722, attenuates ischemic lesion size in rats with temporary middle cerebral artery occlusion: a diffusion and perfusion MRI study

BACKGROUND AND PURPOSE: Endothelins (ETs) are potent vasoconstrictors. Plasma ET levels increase during acute brain ischemia and may worsen the ischemic damage. Diffusion-weighted MRI (DWI) and perfusion imaging (PI) are powerful tools for evaluation of acute cerebral ischemia. We studied the effects of A-127722, a novel ET(A)-selective ET antagonist, on cerebral ischemic lesion size using 2,3,5-triphenyltetrazolium chloride (TTC) staining postmortem, on acute ischemic lesion development with DWI, and on the cerebral circulation using PI. METHODS: Twenty male Sprague-Dawley rats received either 5 mg/kg of A-127722 or vehicle (n=10 per group) intravenously 30 minutes and subcutaneously 4 hours after middle cerebral artery occlusion (MCAO). Whole-brain DWI and single-slice PI were done before initiation of treatment and repeated frequently thereafter up to 4 hours after MCAO. The animals were reperfused in the MRI scanner 90 minutes after the onset of MCAO. At 24 hours the animals were killed, and the brains were cut into six 2-mm-thick slices and stained with 2% TTC. Percent hemispheric lesion volume (%HLV) was calculated for each animal. RESULTS: Physiological parameters, body weight, neurological scores, and premature mortality (2 versus 2) did not differ between the two groups. No hypotension, abnormal behavior, or other adverse effects were seen. TTC-derived %HLV was 25.3+/-5.6% for controls and 16.2+/-9.6% for treated animals (36% reduction, P<.02). Six animals in each group had successful reperfusion as shown by PI. Among these animals, %HLV was 23.2+/-3.1% for controls and 9.3+/-4.4% for treated animals (60% reduction, P=.0001). The beneficial effect of A-127722 was limited to animals in which successful reperfusion was demonstrated. No difference in PI-detected perfusion deficit size was observed between the groups. DWI did not demonstrate significant in vivo lesion size differences. CONCLUSIONS: A-127722 significantly reduced ischemic lesion size in rats without observable adverse effects. It is not clear whether the effect was due to vasodilatation of collateral arterioles not detectable by PI or whether A-127722 has neuroprotective properties that are independent of vascular effects.     

Permeability of a neuroprotective compound NS-7 into brain: comparison between normal and middle cerebral artery-occluded rats

The pharmacokinetics of 4-(4-fluorophenyl)-2-methyl-6-(5-piperidinopentyloxy) pyrimidine hydrochloride (NS-7), a novel neuroprotective compound, in brains of normal and ischemic rats were investigated. In normal rats, the concentrations of NS-7 in the cerebral cortex and striatum were more than 10-folds higher than those in plasma during 5 min and 12 h after intravenous injection. The time course changes in plasma concentration of NS-7 were fitted to the two-compartment open model, in which elimination half-life (t(1/2)beta) was 6.0 h and distribution volume (V1) was 4.4. The estimated striatal interstitial concentration of NS-7 measured by microdialysis was unexpectedly low and almost constant after intravenous injection. Subsequently, the level of NS-7 in brain was compared between sham-operated and middle cerebral artery (MCA)-occluded rats. In MCA-occluded rats, the concentrations of NS-7 in the ischemic cerebral cortex and striatum were 64-71% of those in sham-operated group at 1 h after injection, although the initial concentrations (at 2-5 min) were much lower (about 20%) in MCA-occluded rats. The t(max) was observed at 1 h after injection, which was later than that (5 min) determined in sham-operated rats. Moreover, its elimination half-life was longer in MCA-occluded rats than in sham-operated animals. From these results it is suggested that peripherally administered NS-7 readily penetrates into brain, in which it exists for the most part in parenchymal fraction. In addition, substantial amount of NS-7 may distribute to the ischemic brain regions when it was injected after MCA occlusion.