Improved Correlation of Strain Indices with Cognitive Dysfunction with Inclusion of Adventitial Layer with Carotid Plaque.

Plaque instability may lead to chronic embolization, which in turn may contribute to progressive cognitive decline. Accumulated strain tensor indices over a cardiac cycle within a pulsating carotid plaque may be viable biomarkers for the diagnosis of plaque instability. Using plaque-only carotid artery segmentations, we recently demonstrated that impaired cognitive function correlated significantly with maximum axial and lateral strain indices within a localized region of interest in plaque. Inclusion of the adventitial layer focuses our strain or instability measures on the vessel wall-plaque interface hypothesized to be a region with increased shearing forces and measureable instability. A hierarchical block-matching motion tracking algorithm developed in our laboratory was used to estimate accumulated axial, lateral, and shear strain distribution in plaques identified with the plaque-with-adventitia segmentation. Correlations of strain indices to the Repeatable Battery for the Assessment of Neuropsychological Status Total score were performed and compared with previous results. Overall, correlation coefficients (r) and significance (p) values improved for axial, lateral, and shear strain indices. Shear strain indices, however, demonstrated the largest improvement. The Pearson correlation coefficients for maximum shear strain and cognition improved from the previous plaque-only analyses of -0.432 and -0.345 to -0.795 and -0.717 with the plaque-with-adventitia segmentation for the symptomatic group and for all patients combined, respectively. Our results demonstrate the advantage of including adventitia for ultrasound carotid strain imaging providing improved association to parameters assessing cognitive impairment in patients. This supports theories of the importance of the vessel wall plaque interface in the pathophysiology of embolic disease.

In vivo carotid strain imaging using principal strains in longitudinal view.

Carotid plaque rupture can result in stroke or transient ischemic attack that can be devastating for patients. Ultrasound strain imaging provides a noninvasive method to identify unstable plaque likely to rupture. Axial, lateral and shear strains in carotid plaque have been shown to be linked to carotid plaque instability. Recently, there has been interest in using principal strains, which do not depend on angle of insonification of the carotid artery for quantifying instability in plaque along the longitudinal view. In this work relationships between angle dependent axial, lateral and shear strain along with axis independent principal strains are compared. Three strain indices were defined, 1) Average Mean Strain (AMS), 2) Maximum Mean Strain (MMS) and 3) Mean Standard Deviation (MSD) to identify relationships between these five strain image types in a group of 76 in vivo patients. The maximum principal strain demonstrated the highest strain values when compared to axial strain for all patients with a linear regression slope of 1.6 and a y intercept of 2.4 percent strain for AMS. The maximum shear strain when compared to shear strain had a slope of 1.15 and a y intercept of 0.21 percent for AMS. Next, the effect of insonification angle, which is the angle subtended by the artery at the location of plaque was studied. Patients were divided into three sub groups, i.e. less than 5 degrees (n = 31), between 5 and 10 degrees (n = 24) and above 10 degrees (n = 21). The angle of insonification did not make a significant difference between the three angle groups when comparing the relationship between the angle dependent and independent strain values.

A Cross-Sectional Investigation of Cognition and Ultrasound-Based Vascular Strain Indices.

OBJECTIVE: We examine the relationship between variability in the plaque strain distribution estimated using ultrasound with multiple cognitive domains including executive, language, visuospatial reasoning, and memory function. METHOD: Asymptomatic (n = 42) and symptomatic (n = 34) patients with significant (>60%) carotid artery stenosis were studied for plaque instability using ultrasound strain imaging and multiple cognitive domains including executive, language, visuospatial reasoning, and memory function. Correlation and ROC analyses were performed between ultrasound strain indices and cognitive function. Strain indices and cognition scores were also compared between symptomatic and asymptomatic patients to determine whether there are significant group differences. RESULTS: Association of high-strain distributions with dysexecutive function was observed in both asymptomatic and symptomatic patients. For memory, visuospatial, and language functions, the correlations between strain and cognition were weaker for the asymptomatic compared to symptomatic group. CONCLUSIONS: Both asymptomatic and symptomatic patients demonstrate a relationship between vessel strain indices and executive function indicating that silent strokes and micro-emboli could initially contribute to a decline in executive function, whereas strokes and transient ischemic attacks may cause the further decline in other cognitive functions.

Quantification of carotid artery plaque stability with multiple region of interest based ultrasound strain indices and relationship with cognition.

Vulnerability and instability in carotid artery plaque has been assessed based on strain variations using noninvasive ultrasound imaging. We previously demonstrated that carotid plaques with higher strain indices in a region of interest (ROI) correlated to patients with lower cognition, probably due to cerebrovascular emboli arising from these unstable plaques. This work attempts to characterize the strain distribution throughout the entire plaque region instead of being restricted to a single localized ROI. Multiple ROIs are selected within the entire plaque region, based on thresholds determined by the maximum and average strains in the entire plaque, enabling generation of additional relevant strain indices. Ultrasound strain imaging of carotid plaques, was performed on 60 human patients using an 18L6 transducer coupled to a Siemens Acuson S2000 system to acquire radiofrequency data over several cardiac cycles. Patients also underwent a battery of neuropsychological tests under a protocol based on National Institute of Neurological Disorders and Stroke and Canadian Stroke Network guidelines. Correlation of strain indices with composite cognitive index of executive function revealed a negative association relating high strain to poor cognition. Patients grouped into high and low cognition groups were then classified using these additional strain indices. One of our newer indices, namely the average L - 1 norm with plaque (AL1NWP) presented with significantly improved correlation with executive function when compared to our previously reported maximum accumulated strain indices. An optimal combination of three of the new indices generated classifiers of patient cognition with an area under the curve (AUC) of 0.880, 0.921 and 0.905 for all (n = 60), symptomatic (n = 33) and asymptomatic patients (n = 27) whereas classifiers using maximum accumulated strain indices alone provided AUC values of 0.817, 0.815 and 0.813 respectively.

Antisense knockdown of the glial glutamate transporter GLT-1, but not the neuronal glutamate transporter EAAC1, exacerbates transient focal cerebral ischemia-induced neuronal damage in rat brain.

Transient focal cerebral ischemia leads to extensive neuronal damage in cerebral cortex and striatum. Normal functioning of glutamate transporters clears the synaptically released glutamate to prevent excitotoxic neuronal death. This study evaluated the functional role of the glial (GLT-1) and neuronal (EAAC1) glutamate transporters in mediating ischemic neuronal damage after transient middle cerebral artery occlusion (MCAO). Transient MCAO in rats infused with GLT-1 antisense oligodeoxynucleotides (ODNs) led to increased infarct volume (45 +/- 8%; p < 0.05), worsened neurological status, and increased mortality rate, compared with GLT-1 sense/random ODN-infused controls. Transient MCAO in rats infused with EAAC1 antisense ODNs had no significant effect on any of these parameters. This study suggests that GLT-1, but not EAAC1, knockdown exacerbates the neuronal death and thus neurological deficit after stroke.

Carotid atherosclerotic plaques from symptomatic stroke patients share the molecular fingerprints to develop in a neoplastic fashion: a microarray analysis study.

Identification of genetic mechanisms that promote the onset of stroke and transient cerebral ischemic attack symptoms in carotid atherosclerotic patients would further our understanding of the pathophysiology of this disease and could lead to new pharmacological and molecular therapies. Using Affymetrix Human Genome 230 GeneChip set, the present study evaluated the gene expression differences in geometrically similar carotid artery plaque samples extricated from six symptomatic stroke patients and four asymptomatic patients. There was no significant difference in the degree of stenosis between the two groups. Of the 44,860 transcripts analyzed, 289 (approximately 0.6% of the total transcripts) were differentially expressed between the plaques from the symptomatic and asymptomatic groups (236 were expressed more abundantly and 53 were expressed less abundantly in the symptomatic group). Of the 236 transcripts expressed more abundantly in the symptomatic plaques, 71% (167 transcripts) indicate an active cell proliferation and neoplastic process. These include oncogenes, growth factors, tumor promoters, tumor markers, angiogenesis promoters, transcription factors, RNA splicing factors, RNA processing proteins, signal transduction mediators and those that control the metabolism. Real-time polymerase chain reaction confirmed the increased expression of 63 transcripts in the symptomatic plaques. The other groups of transcripts expressed more abundantly in the symptomatic plaques are those that control ionic homeostasis, those that participate in the progression of degenerative neurological diseases (Alzheimer's disease, amyotrophic lateral sclerosis and Huntington's disease) and epilepsy. This indicates that symptomatic plaques are molecularly and biochemically more active than the asymptomatic plaques, or active plaque growth precipitates stroke symptoms.

Pineal melatonin secretion drives the reproductive response to daylength in the ewe.

This study was conducted to determine whether the pineal indoleamine melatonin mediates the effects of photoperiod on the capacity of estradiol to inhibit LH secretion in the ewe. Patterns of serum melatonin were characterized in pineal-intact ovariectomized ewes treated with sc Silastic estradiol implants and exposed to 90-day alternations between long and short photoperiods. High fluctuating levels of serum melatonin were found during the night, with the duration of elevated serum levels corresponding to the length of the dark period. Transfer from long to short photoperiods caused a rapid change in the duration of nightly melatonin secretion and reduced the negative feedback potency of estradiol upon LH secretion during the natural anestrous season. In pinealectomized ewes, the night-time rise of melatonin was absent, and transfer from long to short days failed to reverse the capacity of estradiol to inhibit LH secretion during anestrus. Nightly infusions of melatonin restored patterns of this indoleamine similar to those observed in pineal-intact ewes exposed to the 90-day alternation between long and short days. The melatonin infusions also restored the reproductive response to the inductive photoperiod: in every ewe, the negative feedback effects of estradiol upon LH secretion were diminished after transfer from long to short days. The amplitude and latency of this escape matched those of pineal-intact animals. We conclude that the pineal mediates the reproductive response of the ewe to inductive photoperiods through its daily rhythm of melatonin secretion.

Effects of citicoline on phospholipid and glutathione levels in transient cerebral ischemia.

BACKGROUND AND PURPOSE: Cytidine-5'-diphosphocholine (citicoline or CDP-choline) is an essential intermediate in the biosynthesis of phosphatidylcholine, an important component of the neural cell membrane. Citicoline provided significant neuroprotection after transient forebrain ischemia in gerbils. This study was undertaken to examine changes and effects of citicoline on phospholipids and glutathione synthesis after transient cerebral ischemia and reperfusion. METHODS: Ten-minute transient forebrain ischemia was induced by bilateral carotid artery occlusion in male Mongolian gerbils with reperfusion up to 6 days. Citicoline (500 mg/kg IP in saline) was given to gerbils just after the end of ischemia, at 3-hour reperfusion, and daily thereafter until 1 day before euthanasia. Hippocampal lipids were extracted and analyzed by thin-layer and gas chromatography. Glutathione was measured by using an enzymatic recycling assay. Glutathione reductase activity was determined by measuring NADPH oxidation. RESULTS: Significant decreases in phospholipids occurred at 1-day reperfusion. Citicoline significantly restored the phosphatidylcholine, sphingomyelin, and cardiolipin levels but did not affect phosphatidylinositol and phosphatidylserine at 1 day. The phospholipids returned to sham levels over days 2 to 6 and were unaffected by citicoline. Ceramide levels significantly increased by 3 and 6 days of reperfusion and were unaltered by citicoline. Ischemia resulted in significant decreases in glutathione and glutathione reductase activity over 3 days of reperfusion. Citicoline significantly increased total glutathione and glutathione reductase activity and decreased the glutathione oxidation ratio, an indicator of glutathione redox status. CONCLUSIONS: Our data indicated that the effects of citicoline on phospholipids occurred primarily during the first day of reperfusion, with effects on glutathione being important over the 3-day reperfusion period.

Blockade of ornithine decarboxylase enzyme protects against ischemic brain damage.

Polyamines are derived from ornithine by the actions of ornithine decarboxylase (ODC), which is the rate-limiting step in this pathway. Polyamines play a role in cell growth, neoplasia, differentiation, and response to injury. We have shown that transient cerebral ischemia gives rise to increased ODC mRNA and enzyme activity in the gerbil brain. ODC and polyamines are thought to be important in the generation of edema and the neuronal cell loss associated with cerebral ischemia. To test this theory, we examined the ODC activity, putrescine levels, and neuronal density in the CA1 region of the hippocampus following ischemia and reperfusion injury in the absence and presence of an inhibitor of ODC activity, alpha-difluoromethylornithine (DFMO). Pretreatment of animals with DFMO resulted in attenuation of the ODC activity following 5 min of ischemia and 4 h of reperfusion. In addition, DFMO prevented the increase in polyamine levels, as determined by measurement of putrescine in the ischemic brain. These alterations were not due to changes in ODC mRNA level. Further analysis revealed that DFMO treatment blocked the delayed neuronal cell death in the CA1 region of the hippocampus that accompanies ischemia and reperfusion injury. Administration of DFMO resulted in a dose-dependent beneficial effect upon neuronal cell survival. These results suggest that ODC enzyme activity and the production of polyamines play a significant role in the response of the brain to ischemic injury.

Na+-K+-Cl- cotransporter in rat focal cerebral ischemia.

In cultured neurons, the authors previously demonstrated that the Na+-K+-Cl- cotransporter is significantly stimulated by elevated extracellular potassium and glutamate, which are important factors in cerebral ischemic damage. These findings led the authors to hypothesize that stimulation of the cotransporter after ischemia might result in Na+, K+, and Cl- influx, and might contribute to neuron damage. In the current study, the authors investigated such a role of the Na+-K+-Cl- cotransporter in focal cerebral ischemia. Cerebral ischemia was induced by 2-hour occlusion of the left middle cerebral artery (MCA) and 24-hour reperfusion in male spontaneously hypertensive rats (SHRs). Immunocytochemical staining and immunoblotting revealed an up-regulation of expression of the cotransporter protein in neurons in cortex at 24 hours of reperfusion. Artificial cerebral spinal fluid (aCSF) or 100 micromol/L bumetanide (a cotransporter inhibitor) in aCSF were continuously microdialyzed through a microdialysis probe into left cortices throughout 2-hour MCA occlusion and 24-hour reperfusion. Compared with the aCSF-treated group, infarction volume was significantly reduced in the bumetanide-treated group (25%, P < 0.05). In addition, brain water content in the bumetanide-treated brains was decreased by 70% (P < 0.05). These results strongly suggest that the Na+-K+-Cl- cotransporter may play an important role in cerebral ischemic neuronal damage.

Ornithine decarboxylase activity and immunohistochemical location in postischemic brain.

Ornithine decarboxylase, rate-limiting in polyamine formation, has been found to be necessary for the development of vasogenic edema after cryogenic cerebral injury and is postulated to be of importance in late ischemic brain edema formation. Ornithine decarboxylase activity and accompanying edema was studied after transient cerebral ischemia in Mongolian gerbils. Bilateral carotid artery occlusion was utilized to produce dense forebrain ischemia. After 4 h of reperfusion a significant elevation in ornithine decarboxylase activity was present (72.5 +/- 24.7 vs 8.5 +/- 2 pmoles/mg protein/h, p less than 0.05). Immunohistochemical localization of ornithine decarboxylase indicated its presence in cortical neurons of ischemic gerbils. This was typically located in the perinuclear cytoplasm and extended into proximal dendrites. Nonischemic animals did not contain ornithine decarboxylase immunoreactivity. These studies show the presence and location of ornithine decarboxylase in cerebral tissue subjected to transient ischemia. The increase in this marker of polyamine activity paralleled previous studies in this model of cerebral edema formation and reperfusion deficit in blood flow and evoked potential, suggesting that ornithine decarboxylase is a marker for and may be associated with those late metabolic events leading to progressive functional deterioration after incomplete cerebral ischemia.

Hyperglycemia suppresses c-fos mRNA expression following transient cerebral ischemia in gerbils.

The c-fos proto-oncogene is activated by transient cerebral ischemia. This activation may signify a specific genetic response to ischemia affecting tolerance to ischemia and ultimate cell survival. Hyperglycemia, which enhances brain injury from transient ischemia, was studied for its effects on this gene system in gerbils by measuring c-fos mRNA 2 h after 20 min of bilateral carotid artery occlusion. Brain c-fos mRNA was increased by ischemia (11.7 +/- 5.0, p less than or equal to 0.05, fold increase) compared to nonischemic controls (1.0 +/- 1.3). Pretreatment with 1 g/kg of glucose partially reduced postischemic c-fos mRNA (6.3 +/- 1.6, p less than or equal to 0.05) while 4 g/kg of glucose completely suppressed postischemic c-fos expression (0.7 +/- 0.3, p less than or equal to 0.05). These data indicate that hyperglycemia suppresses normal postischemic gene expression and suggest the possibility that such suppression is a predictor or even a contributor to hyperglycemia-enhanced ischemic brain damage.

Modulation of ornithine decarboxylase mRNA following transient ischemia in the gerbil brain.

Ornithine decarboxylase (ODC) is the rate-limiting enzyme that catalyzes the synthesis of polyamines from ornithine and is thought to be involved in the cellular response to growth, differentiation, and stress. Previous studies have demonstrated that transient cerebral ischemia results in an increase in ODC activity and polyamine synthesis. We have used the Mongolian gerbil as a model system to test the hypothesis that the cellular response to ischemia induces a distinct pattern of ODC gene expression. Our results indicate that transient ischemia, induced by bilateral carotid occlusion, elevates ODC mRNA within 1-4 h after reperfusion, which correlates with increased ODC activity and polyamine synthesis. Increased ODC mRNA can be detected in the forebrain, striatum, hippocampus, and midbrain but not the cerebellum, which is not subject to ischemic injury. In contrast, c-fos mRNA increased by 15 min after reperfusion and actin mRNA did not demonstrate alterations in level after ischemia. Pentobarbital prevented the increase in ODC mRNA, whereas the glutamate antagonist MK-801 had no effect on the elevation of ODC gene expression after ischemia. We conclude that the ischemia-induced increase in ODC enzyme activity may be attributed in part to transcriptional activation of the ODC gene.

Ornithine decarboxylase knockdown exacerbates transient focal cerebral ischemia-induced neuronal damage in rat brain.

Transient cerebral ischemia leads to increased expression of ornithine decarboxylase (ODC). Contradicting studies attributed neuroprotective and neurotoxic roles to ODC after ischemia. Using antisense oligonucleotides (ODNs), the current study evaluated the functional role of ODC in the process of neuronal damage after transient focal cerebral ischemia induced by middle cerebral artery occlusion (MCAO) in spontaneously hypertensive rats. Transient MCAO significantly increased the ODC immunoreactive protein levels and catalytic activity in the ipsilateral cortex, which were completely prevented by the infusion of antisense ODN specific for ODC. Transient MCAO in rats infused with ODC antisense ODN increased the infarct volume, motor deficits, and mortality compared with the sense or random ODN-infused controls. Results of the current study support a neuroprotective or recovery role, or both, for ODC after transient focal ischemia.

Altered striatal dopaminergic metabolism 36 hours after unilateral trauma to the human mesencephalon.

Markers of dopaminergic synaptic activity and choline acetyltransferase (CAT) were measured in the putamen and caudate nucleus of a patient who lived 36 hours after a unilateral mechanical lesion of the mesencephalon. After cessation of impulse flow along the nigrostriatal tract, dopamine was elevated, dihydroxyphenylacetic acid was diminished, and CAT and tyrosine hydroxylase activity were enhanced in the putamen ipsilateral to the lesion. [3H]-spiperone binding indicated an increase in D2-dopamine receptor density in the caudate nucleus. These findings indicate that the changes predicted from experimental neurochemical models occur in human nigrostriatal systems.

Ischemic induction of protooncogene expression in gerbil brain.

Cerebral ischemia and reperfusion results in an active series of metabolic events, eventually leading to cell death. The expression of specific genes during cerebral ischemia and reperfusion may play an important, determinant role in the mechanisms controlling cellular processes. Ten minutes of bilateral carotid occlusion in the Mongolian gerbil was found to increase the messenger RNA for both the c-fos and c-jun protooncogenes. The changes in gene expression were detected in the regions of ischemia, specifically the cortex and striatum, and no increases were seen in either the brain stem or the cerebellum, which possess a separate circulation. Induction of protooncogene mRNA is correlated to the duration of ischemia, i.e., the longer the time of ischemia, the greater the increase in c-fos expression. Pretreatment of animals with pentobarbital reduced the effect of the ischemic insult and prevented the increase in c-fos mRNA. Analysis of the c-fos and c-jun proteins after ischemia demonstrated an increase in the formation of a functional transcriptional complex and association with the AP-1 binding region. These findings suggest that ischemic cell death and recovery in neurodegenerative disorders such as stroke may involve the regulated expression of these protooncogenes early in the pathway of ischemia.

Beneficial effects of S-adenosyl-L-methionine on blood-brain barrier breakdown and neuronal survival after transient cerebral ischemia in gerbils.

We have studied the beneficial effects of S-adenosyl-L-methionine (SAM) tosylate on blood-brain barrier (BBB) breakdown and neuronal survival after transient cerebral ischemia in gerbils. BBB breakdown experiments were performed in pentobarbital anesthetized gerbils subjected to 10 min of bilateral carotid artery occlusion and 6 h of reperfusion. For BBB breakdown measurements, SAM (120 mg/kg, i.p.) was administered to gerbils just after occlusion and thereafter every hour up to 5 h. Fluorometric measurements quantified the blood-brain permeability tracer, Evans blue (EB). SAM treatment significantly reduced the BBB breakdown as indicated by reduced levels of EB fluorescence. Neuronal count experiments were conducted in gerbils subjected to transient ischemia and 7 days of reperfusion. For neuronal count experiments SAM (15-120 mg/kg) was administered at 6 and 12 h after reperfusion, and twice each day thereafter for 7 days. SAM dose dependently protected the hippocampal CA1 neurons assessed by histopathological methods. SAM has a beneficial effect on the outcome of ischemic injury by reducing the BBB breakdown and neuronal death.

Regional levels of free fatty acids and Evans blue extravasation after experimental brain injury.

The recently developed controlled cortical-impact (CCI) model of brain injury in rats serves as an excellent tool to understand some of the neurochemical mechanisms mediating the pathophysiology of traumatic brain injury. In this study, rats were subjected to lateral CCI brain injury of low-grade severity. Their brains were frozen in situ at various times after injury to measure regional levels of free fatty acids. Tissue total free fatty acids at the injury site within the left cortex were increased at 30 min, 2.5 h, and 24 h postinjury. In injured animals, increases in stearic and arachidonic acids were slightly greater than those in palmitic and oleic acids. The levels of total free fatty acids in the cortex adjacent to the injury site were also increased in injured animals at 2.5 h and 24 h after injury (p < 0.05). Only stearic and arachidonic acids were observed to be significantly increased (p < 0.05) in the adjacent cortex of injured animals at all times after injury. Although no significant increases in total free fatty acids were observed in the left hippocampus adjacent to the injury site, stearate and arachidonate concentrations were increased at 30 min and 2.5 h after injury (p < 0.05). Extravasation of Evans blue was found to be significantly increased in the ipsilateral cortex of injured animals at 30 min and 10 h after brain injury. These results indicate the degradation of membrane phospholipids and blood-brain barrier breakdown in the ipsilateral cortex after lateral CCI brain injury. These results also suggest that arachidonic acid and its metabolites may play a role as a mediator in the blood-brain barrier breakdown associated with cortical impact brain injury in rats.

Application of 2,3,5-triphenyltetrazolium chloride staining to evaluate injury volume after controlled cortical impact brain injury: role of brain edema in evolution of injury volume.

A reliable method for measuring injury volume after traumatic brain injury (TBI) is of great importance when studying pharmacological protective agents in the field of head trauma research. Utilization of 2,3,5-triphenyltetrazolium chloride (TTC) has gained extensive acceptance in stroke research and has recently been applied to injury volume measurement in the lateral fluid percussion model. The present study was undertaken to apply this method to the controlled cortical impact (CCI) model and to study the role of brain edema. Male Sprague-Dawley rats were subjected to CCI brain injury at a velocity of 3 m/sec and 1 mm (mild), 2 mm (moderate), and 3 mm (severe injury) deformation, while rats in the control group were subjected to the same surgical procedure but received no injury. Absolute and corrected injury volumes with TTC staining and brain edema measurements with the wet-dry method were evaluated at 1, 2, 3, 4, and 7 days after TBI. The most prominent injury volume in the moderate injury group (2 mm deformation) was seen at postinjury day 1 and 2 (day 1, absolute: 49.1+/-5.6, corrected: 40.5+/-7.9; day 2, absolute: 46+/-6.9, corrected: 40.2+/-10.5), whereas the smallest injury volume was found at postinjury day 7 (absolute: 24.9+/-7, corrected: 27.4+/-7.4). The time course of brain edema studies demonstrates that brain edema formation peaks at postinjury day 1. A statistically significant reduction of injury volume was observed after postinjury day 4. We also observed that due to the presence of brain edema absolute injury volume is more than corrected injury volume in the first 3 days after injury as opposed to injury volume at postinjury day 7. These results suggest that the measurement of injury volume with TTC staining should be corrected for brain edema in the CCI brain injury model.

Traumatic injury to rat brain upregulates neuronal nitric oxide synthase expression and L-[3H]nitroarginine binding.

Overstimulation of N-methyl-D-aspartate (NMDA) receptors is felt to precipitate the neuronal damage following traumatic brain injury (TBI). NMDA receptor-mediated, glutamate-induced excitotoxicity is thought to be mediated via nitric oxide (NO) formed by neuronal nitric oxide synthase (nNOS). The present study examined the mRNA and protein levels of nNOS in the ipsilateral and contralateral cortex of rats as a function of time (5 minutes to 1 week) after controlled cortical impact (CCI) brain injury. Sham-operated rats served as controls. TBI resulted in a significant increase in the levels of nNOS mRNA (1.5- to 2.8-fold, p < .05) between 2 and 4 hours after the injury. There was also a significant increase in the levels of nNOS protein (by 55% to 90%, p < .05) and binding densities of the nNOS-specific ligand L-[3H]nitroarginine (L-[3H]NOARG) (by 35% to 59%, p < .05) between 2 and 12 hours after the injury. Increased nNOS expression and function may contribute to the concomitant excitotoxic neuronal death after TBI.