Interrelationship of brain edema, motor deficits, and memory impairment in rats exposed to focal ischemia

Neuroprotective Effect of 1,3-dipalmitoyl-2-oleoylglycerol Derived from Rice Bran Oil against Cerebral Ischemia-Reperfusion Injury in Rats

1,3-Dipalmitoyl-2-oleoylglycerol (POP) is a triacylglyceride found in oils from various natural sources, including palm kernels, sunflower seeds, and rice bran. In the current study, the neuroprotective effects and the specific mechanism of POP derived from rice bran oil were investigated for the first time using the middle cerebral artery occlusion/reperfusion (MCAO/R) model in rats. Orally administered POP at 1, 3, or 5 mg/kg (three times: 0.5 h before MCAO, after 1 h of MCAO, and after 1 h of reperfusion) markedly reduced the MCAO/R-induced infarct/edema volume and neurobehavioral deficits. Glutathione depletion and the oxidative degradation of lipids in the rat brain induced by MCAO/R were prevented by POP administration. The upregulation of phosphorylated p38 MAPKs, inflammatory factors (inducible nitric oxide synthase (i-NOS) and cyclooxygenase-2 (COX-2)), and pro-apoptotic proteins (B-cell lymphoma-2 (Bcl-2) associated X protein (Bax) and cleaved caspase-3) and the downregulation of the anti-apoptotic protein (Bcl-2) in the ischemic brain were significantly inhibited by POP administration. In addition, downregulation of phosphatidylinositol 3′-kinase (PI3K), phosphorylated protein kinase B (Akt), and phosphorylated cyclic (adenosine monophosphate) AMP responsive element-binding protein (CREB) expression in the ischemic brain was inhibited by POP administration. These results suggest that POP might exert neuroprotective effects by inhibition of p38 MAPK and activation of PI3K/Akt/CREB pathway, which is associated with anti-oxidant, anti-apoptotic, and anti-inflammatory action. From the above results, the present study provides evidence that POP might be effectively applied for the management of cerebral ischemia-related diseases.

Rodent models used in preclinical studies of deep brain stimulation to rescue memory deficits

Deep brain stimulation paradigms might be used to treat memory disorders in patients with stroke or traumatic brain injury. However, proof of concept studies in animal models are needed before clinical translation. We propose here a comprehensive review of rodent models for Traumatic Brain Injury and Stroke. We systematically review the histological, behavioral and electrophysiological features of each model and identify those that are the most relevant for translational research.

Intranasal Losartan Decreases Perivascular Beta Amyloid, Inflammation, and the Decline of Neurogenesis in Hypertensive Rats

The contribution of the local angiotensin receptor system to neuroinflammation, impaired neurogenesis, and amyloid beta (Aβ) accumulation in Alzheimer's disease (AD) and in hypertension is consistent with the remarkable neuroprotection provided by angiotensin receptor blockers (ARBs) independent of their blood pressure-lowering effect. Considering the causal relationship between hypertension and AD and that targeting cerebrovascular pathology with ARBs does not necessarily require their systemic effects, we tested intranasal losartan in the rat model of chronic hypertension (spontaneously hypertensive stroke-prone rats, SHRSP). Intranasal losartan at a subdepressor dose decreased mortality, neuroinflammation, and perivascular content of Aβ by enhancing key players in its metabolism and clearance, including insulin-degrading enzyme, neprilysin, and transthyretin. Furthermore, this treatment improved neurologic deficits and increased brain IL-10 concentration, hippocampal cell survival, neurogenesis, and choroid plexus cell proliferation in SHRSP. Losartan (1 μM) also reduced LDH release from cultured astroglial cells in response to toxic glutamate concentrations. This effect was completely blunted by IL-10 antibodies. These findings suggest that intranasal ARB treatment is a neuroprotective, neurogenesis-inducing, and Aβ-decreasing strategy for the treatment of hypertensive stroke and cerebral amyloid angiopathy acting at least partly through the IL-10 pathway.

Inhibition of VEGF Signaling Reduces Diabetes-Exacerbated Brain Swelling, but Not Infarct Size, in Large Cerebral Infarction in Mice

In light of repeated translational failures with preclinical neuroprotection-based strategies, this preclinical study reevaluates brain swelling as an important pathological event in diabetic stroke and investigates underlying mechanism of the comorbidity-enhanced brain edema formation. Type 2 (mild), type 1 (moderate), and mixed type 1/2 (severe) diabetic mice were subjected to transient focal ischemia. Infarct volume, brain swelling, and IgG extravasation were assessed at 3 days post-stroke. Expression of vascular endothelial growth factor (VEGF)-A, endothelial-specific molecule-1 (Esm1), and the VEGF receptor 2 (VEGFR2) was determined in the ischemic brain. Additionally, SU5416, a VEGFR2 inhibitor, was treated in the type 1/2 diabetic mice, and stroke outcomes were determined. All diabetic groups displayed bigger infarct volume and brain swelling compared to nondiabetic mice, and the increased swelling was disproportionately larger relative to infarct enlargement. Diabetic conditions significantly increased VEGF-A, Esm1, and VEGFR2 expressions in the ischemic brain compared to nondiabetic mice. Notably, in diabetic mice, VEGFR2 mRNA levels were positively correlated with brain swelling, but not with infarct volume. Treatment with SU5416 in diabetic mice significantly reduced brain swelling. The study shows that brain swelling is a predominant pathological event in diabetic stroke and that an underlying event for diabetes-enhanced brain swelling includes the activation of VEGF signaling. This study suggests consideration of stroke therapies aiming at primarily reducing brain swelling for subjects with diabetes.

Oral administration of ampelopsin protects against acute brain injury in rats following focal cerebral ischemia

Ampelopsin (AMP) is isolated from the Chinese medicinal herb Ampelopsis grossedentata (Hand-Mazz) and has been associated with numerous biological and pharmacological activities. However, it is not clear whether AMP has a direct protective effect on cerebral ischemia reperfusion injury. Therefore, the present study investigated its role in acute brain injury following focal cerebral ischemia in rats. The current study induced transient focal cerebral ischemia by performing middle cerebral artery occlusion (MCAO) for 60 min, followed by 24 h of reperfusion. Rats were exposed to 40, 80 and 160 mg/kg AMP by oral administration 30 min prior to MCAO and the cysteinyl leukotriene receptor 1-antagonist, pranlukast (0.1 mg/kg, i.p.) was used as a positive control. Neurological deficit scores were observed and an inclined board test was used to assess behavioral dysfunction. The coronal slices were stained with 3,5-triphenyltetrazolium chloride to determine the infarct volume and brain edema. Neuronal morphology was assessed in brain sections stained with cresyl violet and degenerating neurons were identified using Fluoro-Jade B staining. Blood-brain barrier permeability was determined with immunoglobulin (Ig)G immunohistochemistry. Interleukin (IL)-1β, tumor necrosis factor-α (TNF-α) in serum and cerebrospinal fluid were measured using ELISA kits. AMP at 80 and 160 mg/kg attenuated neurological deficits, reduced infarct volume, brain edema, IgG exudation and neuron degeneration and loss. Similar to pranlukast, AMP also inhibited the MCAO-induced IL-1β and TNF-α release. Thus, AMP has a neuroprotective effect on acute brain injury following focal cerebral ischemia in rats at an effective oral dose of 80-160 mg/kg. The results of the current study indicate a therapeutic role for AMP in the treatment of ischemic stroke.

A novel indication of platonin, a therapeutic immunomodulating medicine, on neuroprotection against ischemic stroke in mice

Thrombosis and stroke are major causes of disability and death worldwide. However, the regular antithrombotic drugs may have unsatisfactory results and side effects. Platonin, a cyanine photosensitizing dye, has been used to treat trauma, ulcers and some acute inflammation. Here, we explored the neuroprotective effects of platonin against middle cerebral artery occlusion (MCAO)-induced ischemic stroke in mice. Platonin(200 μg/kg) substantially reduced cerebral infarct volume, brain edema, neuronal cell death and neurological deficit scores, and improved the MCAO-reduced locomotor activity and rotarod performance. Platonin(5–10 μM) potently inhibited platelet aggregation and c-Jun NH2-terminal kinase (JNK) phosphorylation in collagen-activated platelets. The antiaggregation effect did not affect bleeding time but increased occlusion time in platonin(100 and 200 μg/kg)-treated mice. Platonin(2–10 μM) was potent in diminishing collagen- and Fenton reaction-induced ^∙OH formation. Platonin(5–10 μM) also suppressed the expression of nitric oxide, inducible nitric oxide synthase, cyclooxygenase-2, interleukin-1β, and JNK phosphorylation in lipopolysaccharide-stimulated macrophages. MCAO-induced expression of 3-nitrotyrosine and Iba1 was apparently attenuated in platonin(200 μg/kg)-treated mice. In conclusion, platonin exhibited remarkable neuroprotective properties against MCAO-induced ischemia in a mouse model through its antiaggregation, antiinflammatory and antiradical properties. The observed therapeutic efficacy of platonin may consider being a novel medcine against ischemic stroke.

The role for infarct volume as a surrogate measure of functional outcome following ischemic stroke

The failed translation of proposed therapeutic agents for ischemic stroke from preclinical to clinical studies has led to increased scrutiny of preclinical studies, namely the model and outcome measures utilized. Preclinical studies routinely use infarct volume as an experimental endpoint or measure in studies employing young-adult, healthy male animals despite the fact that clinically, ischemic stroke is a disease of the elderly and improvements in functional outcome from pre- to post-intervention remains the most widely utilized assessment. The validity of infarct volume as a surrogate measure for functional outcome remains unclear in clinical studies as well as preclinical studies, particularly those utilizing a more clinically relevant aged thromboembolic model. In this work, we will address the relationship between acute and chronic functional outcome and infarct volume using a variety of functional assessments ranging from more simplistic, subjective measurements such as the modified Neurologic Severity Score (mNSS), to more complex, objective measurements such as grip strength and inclined plane.

Speed-accuracy strategy regulations in prefrontal tumor patients

The ability to flexibly switch between fast and accurate decisions is crucial in everyday life. Recent neuroimaging evidence suggested that left lateral prefrontal cortex plays a role in switching from a quick response strategy to an accurate one. However, the causal role of the left prefrontal cortex in this particular, non-verbal, strategy switch has never been demonstrated. To fill this gap, we administered a perceptual decision-making task to neuro-oncological prefrontal patients, in which the requirement to be quick or accurate changed randomly on a trial-by-trial basis. To directly assess hemispheric asymmetries in speed-accuracy regulation, patients were tested a few days before and a few days after surgical excision of a brain tumor involving either the left (N=13) or the right (N=12) lateral frontal brain region. A group of age- and education-matched healthy controls was also recruited. To gain more insight on the component processes implied in the task, performance data (accuracy and speed) were not only analyzed separately but also submitted to a diffusion model analysis. The main findings indicated that the left prefrontal patients were impaired in appropriately adopting stricter response criteria in speed-to-accuracy switching trials with respect to healthy controls and right prefrontal patients, who were not impaired in this condition. This study demonstrates that the prefrontal cortex in the left hemisphere is necessary for flexible behavioral regulations, in particular when setting stricter response criteria is required in order to successfully switch from a speedy strategy to an accurate one.

Neuroprotection of the leaf and stem of Vitis amurensis and their active compounds against ischemic brain damage in rats and excitotoxicity in cultured neurons

Vitis amurensis (Vitaceae) has been reported to have anti-oxidant and anti-inflammatory activities. The present study investigated a methanol extract from the leaf and stem of V. amurensis for neuroprotective effects on cerebral ischemic damage in rats and on excitotoxicity induced by glutamate in cultured rat cortical neurons. Transient focal cerebral ischemia was induced by 2h middle cerebral artery occlusion followed by 24h reperfusion (MCAO/reperfusion) in rats. Orally administered V. amurensis (25-100 mg/kg) reduced MCAO/reperfusion-induced infarct and edema formation, neurological deficits, and neuronal death. Depletion of glutathione (GSH) level and lipid peroxidation induced by MCAO/reperfusion was inhibited by administration of V. amurensis. The increase of phosphorylated mitogen-activated protein kinases (MAPKs), cyclooxygenase-2 (COX-2), and pro-apoptotic proteins and the decrease of anti-apoptotic protein in MCAO/reperfusion rats were significantly inhibited by treatment with V. amurensis. Exposure of cultured cortical neurons to 500 μM glutamate for 12h induced neuronal cell death. V. amurensis (1-50 μg/ml) and (+)-ampelopsin A, γ-2-viniferin, and trans-ε-viniferin isolated from the leaf and stem of V. amurensis inhibited glutamate-induced neuronal death, the elevation of intracellular calcium ([Ca(2+)](i)), the generation of reactive oxygen species (ROS), and changes of apoptosis-related proteins in cultured cortical neurons, suggesting that the neuroprotective effect of V. amurensis may be partially attributed to these compounds. These results suggest that the neuroprotective effect of V. amurensis against focal cerebral ischemic injury might be due to its anti-apoptotic effect, resulting from anti-excitotoxic, anti-oxidative, and anti-inflammatory effects and that the leaf and stem of V. amurensis have possible therapeutic roles for preventing neurodegeneration in stroke.

Protective effect of Ilex latifolia, a major component of "kudingcha", against transient focal ischemia-induced neuronal damage in rats

AIMS OF THE STUDY

Ilex latifolia (Aquifoliaceae), a primary component of "kudingcha", has been used in Chinese folk medicine to treat various kinds of diseases including headaches, inflammatory diseases, and cardiac ischemic injury. The present study investigated the protective effect of the ethanol extract of Ilex latifolia against transient, focal, ischemia-induced neuronal damage.

MATERIALS AND METHODS

Transient focal ischemia was induced by 2 h middle cerebral artery occlusion followed by 24 h reperfusion (MCAO/reperfusion) in rats. After MCAO/reperfusion, brain infarction and neuronal death were measured by triphenyltetrazolium chloride and hematoxylin and eosin staining, respectively. Glutathione concentration and lipid peroxidation rate were measured. The expression levels of phosphorylated mitogen activated proteins kinases (MAPKs), cyclooxygenase 2 (COX-2), and anti-apoptotic and pro-apoptotic proteins were detected by Western blot.

RESULTS

Ilex latifolia (50-200 mg/kg) significantly reduced MCAO/reperfusion-induced infarction and edema formation, neurological deficits, and brain cell death. Depletion of glutathione level and lipid peroxidation induced by MCAO/reperfusion were inhibited by administration of Ilex latifolia. The increase of phosphorylated MAPKs, COX-2, and proapoptotic proteins and the decrease of antiapoptotic protein in MCAO/reperfusion rats were significantly inhibited by treatment with Ilex latifolia.

CONCLUSION

Ilex latifolia ameliorated ischemic injury induced by MCAO/reperfusion in rats, and this neuroprotective effect might be associated with its anti-apoptotic effect, resulting from anti-oxidative and anti-inflammatory actions.

Anti-ischemic activities of aralia cordata and its active component, oleanolic acid

Aralia has been reported to exhibit various pharmacological properties, including anti-inflammatory, antidiabetic and antioxidant activities. We performed in vitro and in vivo analyses on the neuroprotective effects of an ethanolic extract of the aerial parts of Aralia cordata Thunb. (Araliaceae). In cultured cortical neurons from rats, A. cordata (5-20 microg/mL) inhibited 100 muM hydrogen peroxide (H(2)O(2))-induced apoptotic neuronal death, elevation of intracellular calcium concentration ([Ca(2+)](i)) and generation of reactive oxygen species (ROS). Since oleanolic acid isolated from A. cordata also inhibited H(2)O(2)-induced neuronal death, increase in [Ca(2+)](i) and ROS generation in cultured cortical neurons, some of the neuroprotective effects of A. cordata might be attributable to this compound. In rats, A. cordata prevented cerebral ischemic injury induced by 3 h of middle cerebral artery occlusion, followed by 24 h of reperfusion. Ischemic infarct and edema volumes were significantly reduced in rats that received A. cordata (50 mg/kg, orally). These animals exhibited a corresponding improvement in neurological function and a reduction of neuronal death, as determined histologically from the cortex and hippocampal regions. It is possible that the anti-oxidative properties of A. cordata may be responsible for its neuroprotective effects against focal cerebral ischemic injury. In future, A. cordata might play a therapeutic role in the prevention and treatment of neurodegeneration in stroke.

Neuroprotective effect of Sanguisorbae radix against oxidative stress-induced brain damage: in vitro and in vivo

Sanguisorbae radix (SR), the root of Sanguisorba officinalis L. (Rosaceae), has been traditionally used for its anti-inflammatory, anti-infectious and analgesic activities in Korea. Previous work has shown that SR prevents neuronal cell damage induced by Abeta (25--35) in cultured rat cortical neurons. The present study was carried out to further investigate the neuroprotective effect of SR on oxidative stress-induced toxicity in primary culture of rat cortical neurons, and on ischemia-induced brain damage in rats. SR, over a concentration range of 10--50 microg/ml, inhibited H2O2 (100 microM)-induced neuronal death, which was significantly inhibited by MK-801 (5 microM), an N-methyl-D-aspartate (NMDA) receptor antagonist, and verapamil (20 microM), an L-type Ca2+ channel blocker. Pretreatment of SR (10-50 microg/ml), MK-801 (5 microM), and verapamil (20 microM) inhibited H2O2-induced elevation of intracellular Ca2+ concentration ([Ca2+]i) measured by a fluorescent dye, Fluo-4 AM. SR (10-50 microg/ml) inhibited H2O2-induced glutamate release into medium measured by HPLC, and generation of reactive oxygen species (ROS) measured by 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA). In vivo, SR prevented cerebral ischemic injury induced by 2-h middle cerebral artery occlusion (MCAO) and 24-h reperfusion. The ischemic infarct and edema were significantly reduced in rats that received SR (10, 30 mg/kg, orally), with a corresponding improvement in neurological function. Catechin isolated from SR inhibited H2O2-induced neuronal death in cultures. Taken together, these results suggest that SR inhibits H2O2-induced neuronal death by interfering with the increase of [Ca2+]i, and inhibiting glutamate release and generation of ROS, and that the neuroprotective effect of SR against focal cerebral ischemic injury is due to its anti-oxidative effects. Thus SR might have therapeutic roles in neurodegenerative diseases such as stroke.

Inflammation in areas of remote changes following focal brain lesion

Focal brain lesions can lead to metabolic and structural changes in areas distant from but connected to the lesion site. After focal ischemic or excitotoxic lesions of the cortex and/or striatum, secondary changes have been observed in the thalamus, substantia nigra pars reticulata, hippocampus and spinal cord. In all these regions, inflammatory changes characterized by activation of microglia and astrocytes appear. In the thalamus, substantia nigra pars reticulata and hippocampus, an expression of proinflammatory cytokine like tumor necrosis factor-alpha and interleukin-1beta is induced. However, time course of expression and cellular localisation differ between these regions. Neuronal damage has consistently been observed in the thalamus, substantia nigra and spinal cord. It can be present in the hippocampus depending on the procedure of induction of focal cerebral ischemia. This secondary neuronal damage has been linked to antero- and retrograde degeneration. Anterograde degeneration is associated with somewhat later expression of cytokines, which is localised in neurons. In case of retrograde degeneration, the expression of cytokines is earlier and is localised in astrocytes. Pharmacological intervention aiming at reducing expression of tumor necrosis factor-alpha leads to reduction of secondary neuronal damage. These first results suggest that the inflammatory changes in remote areas might be involved in the pathogenesis of secondary neuronal damage.

Neuropsychological outcome after fractionated stereotactic radiotherapy (FSRT) for base of skull meningiomas: a prospective 1-year follow-up

PURPOSE

The purpose of this study was to evaluate the cognitive outcome after fractionated stereotactic radiotherapy (FSRT) in patients with base of skull meningiomas.

METHODS AND MATERIAL

A total of 40 patients with base of skull meningiomas were neuropsychologically evaluated before, after the first fraction (1.8 Gy), at the end of FSRT (n=37), 6 weeks (n=24), 6 (n=18) and 12 months (n=14) after FSRT. A comprehensive test battery including assessment of general intelligence, attention and memory functions was used. Alternate forms were used and current mood state was controlled.

RESULTS

After the first fraction a transient decline in memory function and simultaneous improvements in attention functions were observed. No cognitive deteriorations were seen during further follow-up, but increases in attention and memory functions were observed. Mood state improved after the first fraction, at the end of radiotherapy and 6 weeks after radiotherapy.

CONCLUSION

The present data support the conclusion that the probability for the development of permanent cognitive dysfunctions appears to be very low after FSRT. The transient memory impairments on day 1 are interpreted as most likely related to an increase of a preexisting peritumoral edema, whereas the significant acute improvements in attention functions are interpreted as practice effects. An analysis of localization specific effects of radiation failed to show clear hemisphere specific cognitive changes.

Impaired motor activity and motor learning function in rat with middle cerebral artery occlusion

The poor quality of life after a stroke is largely attributed to deficits in cognitive-motor functioning. The goals of this study were to detect if damaged motor learning function were attributed to motor deficits in rats following a transient middle cerebral artery (MCA) occlusion. Stroke was induced by a 2-h occlusion of the MCA using an intraluminal filament. Motor functions were evaluated from 5 up to 28 days after reperfusion in ischemic and control rats. Motor function was detected by a series of motor tests (runway traversing and beam balancing, as well as foot fault placing, parallel bar crossing, rope and ladder climbing), and motor learning behavior was determined by analyzing the rate of improvement of impaired function during performance of the motor tasks. Significant (P<0.001) motor deficits were detected in the stroke group (n=10) while performing motor tasks that involve extensive coordination, in comparison to the controls (n=12). Although motor behavior was improved with repeated behavior testing, unparalleled rate of improvement of motor performance on rope and ladder climbing tests was found between the two groups, suggesting an impaired motor learning function. Brain tissue damage was detected in the ischemic animals 28 days after surgery, demonstrated by 40% infarct volume of contralateral hemisphere. Both motor learning and motor function were impaired in ischemic rats. The motor tests used in this study are sensitive, semi-quantitative, and reproducible measurements of functional impairment in rats following an ischemic stroke.

Cognitive and behavioral assessment in experimental stroke research: will it prove useful?

Stroke in humans is associated with deficits in sensorimotor and cognitive function. Consequently, many stroke researchers recently have expanded their techniques to assess cognitive and behavioral correlates of histologically-determined stroke damage in animal models. Although the incorporation of functional outcome assessment represents an important step forward in stroke research, reports of middle cerebral artery occlusion (MCAO) induced behavioral deficits often conflict, and a significant correlation between post-stroke histology and behavior has been reported in few stroke studies. Discrepancies in behavioral outcomes among studies may be due to several factors, such as method of MCAO, duration of occlusion, strain, the timing and method of the behavioral testing and the laboratory environment. Furthermore, proper experimental and control groups, necessary to rule out potential confounding factors during cognitive testing, often are not incorporated. The goal of this review is: (1) to provide a description of the techniques most commonly employed to assess functional outcome after (MCAO) in rodents and (2) to identify potential confounding factors that may interfere with a clear interpretation of the behavioral data.

S-allylcysteine inhibits free radical production, lipid peroxidation and neuronal damage in rat brain ischemia

The efficacy of S-allylcysteine (SAC) as a free radical scavenger was studied using rat brain ischemia models. In a middle cerebral artery occlusion model, preischemic administration of SAC had the following effects: it improved motor performance and memory impairment and reduced water content and the infarct size. In a transient global ischemia model, the time course of free radical (alkoxyl radical) formation as studied by electron paramagnetic resonance (EPR) spectroscopy and alpha-phenyl-N-tert-butylnitrone (PBN) was biphasic; the first peak occurred at 5 min and the second at 20 min after reperfusion. Although SAC did not attenuate the first peak, it did affect the second peak, which is related to lipid peroxidation. The lipid peroxidation as estimated by thiobarbituric acid reactive substances (TBARS) increased significantly at 20 min after reperfusion. SAC decreased TBARS to the levels found without ischemia. These results suggest that SAC could have beneficial effects in brain ischemia and that the major protective mechanism may be the inhibition of free radical-mediated lipid peroxidation.

A temporal MRI assessment of neuropathology after transient middle cerebral artery occlusion in the rat: correlations with behavior

The purpose of this study was to evaluate the temporal and spatial pathological alterations within ischemic tissue using serial magnetic resonance imaging (MRI) and to determine the extent and duration of functional impairment using objective behavioral tests after transient middle cerebral artery occlusion (tMCAO) in the rat. MRI signatures derived from specific anatomical regions of interest (ROI) were then appropriately correlated to the behavioral measures over the time course of the study (up to 28 days post-tMCAO). Sprague-Dawley rats (n = 12) were initially trained on the following behavioral tasks before surgery: bilateral sticky label test (for contralateral neglect); beam walking (for hindlimb coordination); staircase test (for skilled forelimb paw-reaching). Rats were then randomly assigned to receive either tMCAO (90 minutes, n = 6), by means of the intraluminal thread technique, or sham-control surgery (n = 6). Proton density, T2- and T2-diffusion-weighted MR images were acquired at 1, 7, 14, and 28 days post-tMCAO that were then smoothed into respective proton density, T2 relaxation, and apparent diffusion coefficient (ADC) maps. Apparent percent total lesion volume was assessed using T2W imaging. MR signatures were evaluated using the tissue maps by defining ROI for MCAO and sham-control groups, which corresponded to the caudate-putamen, forelimb, hindlimb, and lower parietal cortices both ipsilateral and contralateral to the occlusion site. Behavioral tests were undertaken daily from 1 to 28 days post-tMCAO. Results demonstrate that apparent percent lesion volume reduced from 1 to 7 days (P < 0.05) but then remained constant up to 28 days for the MCAO group. Pathological changes in the temporal profile of T2 and ADC tissue signatures were significantly altered in specific ROI across the time course of the study (P < 0.05 to <0.001), reflecting the progression of edema to necrosis and cavitation. Both T2 and ADC measures of ischemic pathology correlated with parameters defined by each of the functional tests (r > or =0.5, P < 0.05) across the time course. The staircase test revealed bilateral impairments for the MCAO group (P <0.001), which were best predicted by damage to the ipsilateral lower parietal cortex by means of hierarchical multiple regression analyses (R2 changes > or =0.21, P < or =0.03). Behavioral recovery was apparent on the beam walking test at 14 to 28 days post-MCAO, which was mirrored by MRI signatures within the hindlimb cortex returning to sham-control levels. This long-term study is the first of its kind in tracing the dynamic pathologic and functional consequences of tMCAO in the rat. Both serial MRI and objective behavioral assessment provide highly suitable outcome measures that can be effectively used to evaluate promising new antiischemic agents targeted for the clinic.

Evaluation of a motor deficit after chronic focal cerebral ischemia in rats

It is well known that hemiplegia is frequently observed in cerebral ischemia. It is important for the pathophysiologic study and development of drug therapies to establish a precise method investigating impairment of motor function with animal models. To develop a quantitative and objective method for evaluating impairment of motor function, we examined an inclined plane test after chronic focal cerebral ischemia in the rat. Standard scoring of neurologic deficits has limitations, including problems with quantification and objectivity. The purpose of this study was to establish a novel method for evaluating impairment of motor function in middle cerebral artery (MCA) occluded rats. The left MCA was permanently occluded at a proximal site, and sensorimotor performance was evaluated at the fifth day and every week for 11 weeks thereafter. The ability to maintain body position on an inclined plane was measured when rats were placed on a stainless steel slope in left-headed, right-headed, and up-headed positions. Neurologic examination based on hemiparesis and abnormal posture was also performed. After all behavioral examinations were completed, the degree of shrinkage of the left hemisphere to the contralateral was measured. The ability of MCA-occluded rats to maintain position on an inclined plane in the left-headed position was significantly restricted when compared with that of sham-operated rats throughout the test period (maximum angle of 37 degrees versus 45 degrees, respectively). Minimal natural recovery was observed for all position measurements. MCA-occluded rats showed a significantly higher neurologic score with natural recovery. The ability to maintain position on an inclined plane after MCA occlusion (MCAO) was significantly correlated with the degree of the shrinkage of the ischemic hemisphere and neurologic score. The angle for the left-headed position was most strongly correlated with ipsilateral shrinkage. In the present study, long-lasting impairment of motor function was detected in rats with MCAO, which correlated with the shrinkage of the ischemic hemisphere. Furthermore, a difference in performance depending on body position (left-headed versus right-headed) was also detected. The left-headed position was found to be most sensitive for evaluating this model. The inclined plane test is a quantitative, objective, and sensitive method for evaluating motor deficits after chronic focal cerebral ischemia in rats, and this method may be useful to investigate changes in motor function in hemiplegia.

To what extent have functional studies of ischaemia in animals been useful in the assessment of potential neuroprotective agents?

A general consensus is being reached on the use of a combination of mortality and functional end-points in clinical trials of neuroprotective agents. However, to date, few preclinical studies have examined the effects of putative neuroprotective agents on functional outcome after ischaemia. The data described in this review show the importance of combining both histopathological and neurobehavioural studies when evaluating the neuroprotective efficacy of anti-ischaemic agents in animal models of cerebral ischaemia. Here, Jackie Hunter, Ken Mackay and Derek Rogers argue that measures of functional improvement in models of ischaemia should be incorporated to characterize further the neuroprotection afforded by a compound that could aid the selection of doses and end-point measures in early clinical trials.

Postischemic hypothermia. A critical appraisal with implications for clinical treatment

The use of hypothermia to mitigate cerebral ischemic injury is not new. From early studies, it has been clear that cooling is remarkably neuroprotective when applied during global or focal ischemia. In contrast, the value of postischemic cooling is typically viewed with skepticism because of early clinical difficulties and conflicting animal data. However, more recent rodent experiments have shown that a protracted reduction in temperature of only a few degrees Celsius can provide sustained behavioral and histological neuroprotection. Conversely, brief or very mild hypothermia may only delay neuronal damage. Accordingly, protracted hypothermia of 32-34 degrees C may be beneficial following acute clinical stroke. A thorough mechanistic understanding of postischemic hypothermia would lead to a more selective and effective therapy. Unfortunately, few studies have investigated the mechanisms by which postischemic cooling conveys its beneficial effect. The purpose of this article is to evaluate critically the effects of postischemic temperature changes with a comparison to some current drug therapies. This article will stimulate new research into the mechanisms of lengthy postischemic hypothermia and its potential as a therapy for stroke patients.

Sensorimotor impairments in rats with cerebral infarction, induced by unilateral occlusion of the left middle cerebral artery: strain differences and effects of the occlusion site

Enormous differences exist between rat strains with respect to the infarct volume induced by unilateral middle cerebral artery (MCA) occlusion. We performed three experiments to address the following questions. Firstly, whether the pattern of MCA-occlusion (MCA-O) induced sensorimotor impairments in rats are strain dependent; secondly, whether proximal (i.e., close to its origin) and distal occlusions (above the lenticulostriate branch) of the MCA affect infarct volume and the behavioral impairments to a different extent; and thirdly, whether there is a relationship between the infarct volume and behavioral deficits. We found that the pattern of sensorimotor malfunctions induced by proximal unilateral MCA-O were highly strain dependent. Of the eight strains tested, Winkelmann-Wistar rats, Spontaneously Hypertensive Stroke-Prone rats, and Wistar-Kyoto rats were most severely affected. By contrast, Brown-Norway rats showed only mild behavioral deficits after the MCA-O. The second experiment confirmed that proximal occlusions induced slightly more behavioral malfunctions than distal occlusions did. Histological evaluation of the brain damage caused by proximal and distal MCA-O, confirmed that distal MCA-O damaged nearly exclusively cortical areas, and spared the caudate/putamen. An exploratory analysis of the relationship between infarct volume and behavioral deficits did not indicate that the severity of sensorimotor malfunctions can be predicted from the size of the infarct.

Motor dysfunction in a photothrombotic focal ischaemia model

The study of behavioural deficits resulting from cerebral infarction in animal models of stroke has in the past taken second place to histological assessment. This is particularly true of the photothrombotic lesion model. Most tests currently used to measure motor deficits use a scoring system to quantify parameters such as beam walking. The present study set out to characterise a simple and objective assessment for motor impairment in the photothrombotic cortical lesion model. Rats were assessed on a number of motor function tests, i.e. gross locomotor activity, rotarod, and grip strength. After the establishment of stable baselines, cortical photothrombotic lesions were induced, after which the animals were re-tested for a further 18 days. The presence of cortical photothrombotic lesions significantly imparied the rats' performance on the rotarod and grip-strength tests. The deficit observed with the grip-strength task appeared 24 h postsurgery, but was much reduced by day 18 postsurgery. The rotarod test revealed an effect that took longer to establish, but which was more persistent. Gross locomotor activity was not affected. These data suggest that bilateral photothrombotic lesions of the prefrontal cortex produce deficits that can be detected by rotarod and grip-strength tasks.

Behavioral studies on rats with transient cerebral ischemia induced by occlusion of the middle cerebral artery

The behavioral effects of transient cerebral ischemia in adult Wistar rats were studied. In Experiment 1, rats were subjected to 90-min occlusion of the unilateral, left or right, middle cerebral artery (MCA) followed by recirculation. The locomotor activity had not changed 3 and 30 days after the occlusion, except that the number of rearing was significantly decreased by left MCA occlusion. Rats were examined in a radial maze system for learning and memory ability during 4 weeks from the 3rd day after ischemia (the 3rd day was counted as day 1 of the experiment). Maze performance was slightly disturbed due to focal brain damage by MCA occlusion, but the disturbance was statistically significant only on days 6, 11, and 15 in the right occlusion. In Experiment 2, rats were trained to master a radial maze task completely for 4 weeks, and then subjected to transient unilateral (right) ischemia as described above. These rats showed an increase in incorrect entry in the radial maze task from day 4 to day 14. However, on day 21, the number of incorrect entry decreased to the control level of the sham-operated group. The numbers of correct choice were inversely related with those of incorrect entry, though slightly blunted. Coincidentally, the time required to solve the maze task was also prolonged from day 4 to day 14, but returned to the control time on day 21. These results suggest that unilateral ischemia transiently suppresses both acquiring radial maze performance and maintenance of learned performance and that it is a good model for studying human focal cerebral ischemia.

Use of mild intraischemic hypothermia versus mannitol to reduce infarct size after temporary middle cerebral artery occlusion in rats

To determine which of two treatments for reducing ischemic injury after temporal focal ischemia is more effective, the effects of mild (33 degrees C) intraischemic hypothermia were compared with those of mannitol, the most commonly used neuroprotective agent. Four groups of Sprague-Dawley rats underwent 1 hour of endovascular middle cerebral artery occlusion followed by 23 hours of normothermic reperfusion. The four experimental groups were as follows: Group A, saline control; Group B, mannitol (25%, 1 g/kg); Group C, hypothermia; and Group D, hypothermia plus man-nitol. Laser-Doppler estimates of cortical blood flow showed that hypothermia did not affect blood flow during ischemia or reperfusion. Mannitol increased cortical blood flow during ischemia and reperfusion under both normothermic and hypothermic conditions (p < 0.05). Neurological deficit was significantly less severe in treated rats (Group B, p < 0.05; Group C or D, p < 0.01) than in controls (Group A). Infarct volume, measured on semiserial Nissl-stained sections, was significantly smaller in treated rats (p < 0.01) than in controls. Infarct volume was also significantly smaller in rats treated with hypothermia than in those treated with mannitol (Group C vs. Group B, p < 0.05); there was no difference between rats treated with mannitol and those treated with mannitol and hypothermia. All three treatments reduced infarct area in the ischemic penumbra; hypothermia with or without mannitol also reduced infarct area in the ischemic core. These results demonstrate that both mild intraischemic hypothermia and mannitol reduce infarct size and neurological deficit: hypothermia reduces infarct size more effectively than mannitol, and mannitol adds no significant protection to hypothermia, whereas hypothermia adds significant protection beyond that afforded by mannitol after brief focal ischemia followed by reperfusion in rats. The results suggest that mild intraischemic hypothermia alone, or in combination with mannitol, may be useful in avoiding ischemic injury from temporary vessel occlusion during cerebrovascular surgery.

Nimodipine prevents early loss of hippocampal CA1 parvalbumin immunoreactivity after focal cerebral ischemia in the rat

The effect of focal cerebral ischemia induced by middle cerebral artery occlusion on hippocampal interneurons containing the calcium-binding protein parvalbumin (PV) was studied in rats. Four hours after the onset of ischemia, a reduced number of PV-immunoreactive (-ir) neurons was observed in the lateral part of the CA1 region, while PV-ir was not altered in the CA2 and CA3 areas. Pretreatment with the L-type Ca2+ channel blocker nimodipine prevented the ischemia-induced loss of PV-ir in the CA1, suggesting a role for L-type voltage sensitive calcium channels in the mechanism of early neuronal alterations in the hippocampus CA1 region after focal cerebral ischemia.

Oedema reduction by levemopamil in focal cerebral ischaemia of spontaneously hypertensive rats studied by magnetic resonance imaging

The effect of treatment with the Ca2+ channel blocker and 5-HT2 receptor antagonist levemopamil (recommended INN for (S)-emopamil) on the extent of ischaemic brain oedema was studied by magnetic resonance imaging in vivo. Focal cerebral ischaemia was induced in spontaneously hypertensive rats by permanent middle cerebral artery occlusion. The treatment consisted of slow intravenous injections of an aqueous solution of levemopamil given immediately after middle cerebral artery occlusion and again 2 h and 4 h later. One group of animals (n = 17) received 3 x 2 mg/kg of levemopamil (total dose: 6 mg/kg) and another group (n = 13) received 3 x 4 mg/kg (total dose: 12 mg/kg). Saline was administered to the controls (n = 16) at corresponding times. High-resolution T2-weighted spin echo images were obtained 24 h after middle cerebral artery occlusion from two transversal brain planes (4.5 mm and 6.5 mm dorsal to the interaural line). Dose-dependent reductions of brain oedema were achieved in both brain planes. The lower dose of levemopamil reduced the extent of oedema significantly (P < 0.05) by 20 +/- 3.7% in the upper and by 21 +/- 3.8% in the lower brain plane as compared to the controls (means +/- S.E.M.). The higher dose diminished the extent of oedema in the same planes by 30 +/- 3.5% and 31 +/- 4.0%, respectively. Dose-dependent reductions of infarct size, as determined by vital tissue staining using 2,3,5-triphenyltetrazolium chloride (TTC), were observed in the levemopamil-treated groups. Body temperature was not affected by levemopamil, suggesting direct cerebroprotection by this drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Potentiation of nitric oxide formation following bilateral carotid occlusion and focal cerebral ischemia in the rat: in vivo detection of the nitric oxide radical by electron paramagnetic resonance spin trapping

We have directly demonstrated in vivo that nitric oxide (NO) is produced in the ischemic rat brain. Using diethyldithiocarbamate and Fe as spin-trapping agents, NO spin adducts were detected by cryogenic electron paramagnetic resonance. The cerebral cortex which was exposed to focal ischemia or bilateral carotid artery occlusion generated an increased amount of spin-adducts of NO radicals (g = 2.039, a hyperfine coupling constant aN = 13 gauss). This signal disappeared by the preischemic administration of NG-nitro-L-arginine methylester, a NO synthase inhibitor.

Endonuclease activation following focal ischemic injury in the rat brain

The structural changes which occur in chromatin DNA after ischemic brain injury are poorly understood. This study examined the appearance of double-strand DNA breaks and the temporal profile of DNA degradation following focal ischemic injury in rat brain. Focal cerebral ischemia was produced by tandem occlusion of the common carotid and proximal middle cerebral arteries. The effects of decapitation ischemia were also studied by DNA analysis. DNA was extracted by standard methods from the ischemic brain tissues and electrophoresed on a 1.5% agarose gel. With decapitation ischemia, random DNA cleavage was observed as a dense "smear" on the gel electrophoresis beginning 6 h after the ischemic insult, and increasing in amount thereafter. Focal ischemia provided DNA fragmentation, which is specific DNA cleavage at the internucleosomal linker regions, particularly in the caudoputamen. Coexisting random degradation and specific fragmentation of DNA was observed in the cortex following focal ischemia. To determine whether an endonuclease responsible for DNA fragmentation was present, nuclear proteins were extracted from normal brain nuclei and the endonuclease activity was determined using plasmid DNA and a nuclear incubation system. This demonstrated that brain nuclear proteins have Ca(2+)-dependent endonuclease activity which is related to DNA fragmentation. Ischemic injury causes both random and specific DNA cleavage in the brain, which is probably mediated by Ca(2+)-dependent endonuclease.

Effect of riluzole on focal cerebral ischemia in rats

The effects of riluzole, a putative inhibitor of glutamate release, on the histological and neurobehavioral consequences of middle cerebral artery occlusion were tested in Sprague-Dawley rats. Neurobehavioral studies (neurological examination, passive avoidance task) were carried out with sham-operated and occluded rats. Riluzole 4 and 8 mg/kg administered 30 min after occlusion reduced (P < 0.01) the cortical infarct (respectively 94 +/- 12 mm3 and 73 +/- 15 mm3 versus 139 +/- 8 mm3 for control rats). Striatum necrosis was not modified by the low dosage (46 +/- 3 mm3 versus 49 +/- 3 mm3 for control rats), whereas the high dosage increased it (61 +/- 3 mm3, P < 0.05). The ischemia-induced neurological and memory impairments were not improved by riluzole. Our results indicate that a drug depressing glutamatergic neurotransmission without blocking the glutamate receptors exerts anti-ischemic activity. Moreover, the results highlight the need for carrying out histological and neurobehavioral studies in parallel in this model.

Diffusion- and T2-weighted imaging: evaluation of oedema reduction in focal cerebral ischaemia by the calcium and serotonin antagonist levemopamil

Magnetic resonance imaging (MRI) was used to evaluate beneficial drug effects in a rat model of focal cerebral ischaemia. Extent of cerebral oedema was measured on T2-weighted images 24 hr after permanent middle cerebral artery occlusion (MCAO) in spontaneously hypertensive rats. Areas of increased signal intensity strongly correlate with histochemically determined areas of ischaemia in corresponding brain planes (r = 0.84; p < .001). In a separate cohort of animals, spatial progression of oedema formation was studied at 3, 24, 48, and 72 hr after MCAO showing a maximum extent at 48 hr. Early events in cerebral ischaemia were monitored using diffusion-weighted imaging. Effects of levemopamil [formerly (S)-emopamil], a calcium and serotonin antagonist, and the reference compound isradipine were quantified on high resolution T2-weighted spin-echo images 24 hr after MCAO. Combined pre- and posttreatment with isradipine showed a 21% inhibition of oedema progression. Application of a single dose (10 mg/kg) of levemopamil either 30 min before or 2 hr after MCAO revealed a diminution of oedematous areas by 19% and 25%, respectively. Levemopamil reduces the extent of ischaemic brain oedema in an established stroke model.

Genetic hypertension and increased susceptibility to cerebral ischemia

A review of the sensitivity of genetically hypertensive rats to cerebral ischemia was presented together with original data describing the systematic comparison of the effects of focal ischemia (permanent and temporary with reperfusion) performed in hypertensive and normotensive rats (i.e., blood pressures verified in conscious instrumented rats). Microsurgical techniques were used to isolate and occlude the middle cerebral artery (MCAO) of spontaneously hypertensive (SHR), Sprague-Dawley (SD) and Wistar Kyoto (WKY) rats at the level of the inferior cerebral vein. Following permanent (24 h) MCAO, persistent and similar decreases in local microvascular perfusion (i.e., to 15.6 +/- 1.7% of pre-MCAO levels) were verified in the primary ischemic zone of the cortex for all strains using Laser-Doppler flowmetry. A contralateral hemiplegia that occurred following MCAO, evidenced by forelimb flexion and muscle weakness, was greater in SHR (neurological grade = 2.0 +/- 0.1) than SD (1.0 +/- 0.4) or WKY (0.7 +/- 0.4) rats (N = 7-9, p less than 0.05). SHR also exhibited sensory motor deficits following MCAO compared to sham-operation, with decreased normal placement response of the hindlimb (% normal = 20 vs. 83, N = 23-30, p decreased rota-rod (41 +/- 7 vs. 126 +/- 19 on rod, N = 10-15, p less than 0.05) and balance beam (25 +/- 5 vs. 116 +/- 29 s on beam, N = 5-7, p less than 0.05) performance. However, an index of general motor activity was not affected by permanent MCAO. Triphenyltetrazolium-stained forebrain tissue analyzed by planimetry revealed a significantly larger and more consistent cortical infarction in SHR (hemispheric infarction = 27.9 +/- 1.5%) compared to SD (15.4 +/- 4.1%) and WKY (4.0 +/- 2.4%) rats (N = 7-9, p less than 0.05), occupying predominantly the frontal and parietal areas. Also, a significant degree of ipsilateral hemispheric swelling (4.6 +/- 0.9%, N = 7-9, p less than 0.05) and increased brain water content (78.4 +/- 0.3% to 80.4 +/- 0.2%, N = 8-9, p less than 0.05) was identified in SHR that was not observed in SD or WKY rats. A novel model of temporary MCAO also was evaluated in the hypertensive and normotensive rat strains. Initially, the effect of increasing MCAO-time followed by 24 h reperfusion in SHR was studied. During temporary MCAO (20 to 300 min), persistent and stable decreases in local microvascular perfusion (i.e., to 15-20% of pre-MCAO levels) were verified in the primary ischemic zones of the cortex.(ABSTRACT TRUNCATED AT 400 WORDS)

Atrial natriuretic peptide augments the blood-brain transfer of water but not leucine and glucose

Recent evidence predicts an effect of atrial natriuretic peptide (ANP) on the blood-brain transfer of water. To test this prediction, we measured the blood-brain transfer of water, L-leucine, and D-glucose in 9 brain regions of male rats after intravenous injection of 10 pmol ANP. The peptide elicited an increase of the permeability-surface area (PaS) product of labeled water by 28-108% while the PaS products of leucine and glucose remained unchanged. Cerebral blood flow increased 15-48% while cardiac output and plasma volume in brain did not alter, indicating no change of capillary surface area (CSA). Regionally, the CSA varied from 63 cm2/g (striatum) to 97 cm2/g (colliculi) and the fraction of capillaries contributing to the total vascular volume varied from 29% (olfactory bulb/lobe) to 62% (striatum). The blood-brain barrier (BBB) permeability to water (5.7 micron/s) was an order of magnitude higher than to glucose (0.4 micron/s) or to leucine (0.3 micron/s).

GM1 ganglioside reduces cognitive dysfunction after focal cortical ischemia

The functional consequences of cortical focal ischemia and the effect of monosialoganglioside (GM1) treatment on learning/performance of a spatial reversal task were investigated. Cortical focal ischemia was induced by a permanent occlusion of the left common carotid artery and the ipsilateral middle cerebral artery, with a 1-h clamping of the contralateral carotid artery. Twenty-six rats were randomly assigned to three groups: sham controls, a saline-treated ischemic group, and a GM1 ganglioside-treated ischemic group (10 mg/kg/day: IM). Fifteen days after surgery rats were trained on a spatial reversal task in a two-lever operant chamber where food reward was contingent on lever pressing. Training continued from day 15 to day 21 after surgery. Cortical focal ischemia resulted in learning/performance deficits that were reduced by GM1 ganglioside treatment. The cognitive deficits were characterized by a significantly higher number of nonperseverative errors and number of responses to criterion. There was a significant difference between left and right lever performance in the saline-treated ischemic group, which was absent in shams and GM1-treated ischemic rats. On all measures GM1-treated rats were not different from sham controls.