Comparison of behavioral deficits and acute neuronal degeneration in rat lateral fluid percussion and weight-drop brain injury models

Temporal pattern of neurodegeneration, programmed cell death, and neuroplastic responses in the thalamus after lateral fluid percussion brain injury in the rat

The effects of traumatic brain injury (TBI) on the thalamus are not well characterized. We analyzed neuronal degeneration and loss, apoptosis, programmed cell death-executing pathways, and neuroplastic responses in the rat thalamus during the first week after lateral fluid percussion injury (LFPI). The most prominent neurodegenerative and neuroplastic changes were observed in the region containing the posterior thalamic nuclear group and ventral posteromedial and posterolateral thalamic nuclei ipsilateral to the LFPI. There was progressive neurodegeneration in these regions, with maximal neuronal loss on Day 7. Increases in numbers of apoptotic cells were detected on Day 1 and were enhanced on Days 3 and 7 after TBI. There was unchanged expression of active caspase-3 at all postinjury time points, but there was increased expression of apoptosis-inducing factor (AIF) on Day 7. The AIF nuclear translocation was detected on Day 1 and was maximal on Day 7. Total thalamic synaptophysin expression was unchanged, but immunostaining intensities were increased at all time points after TBI. Decreased growth-associated protein-43 expression and signal intensity were observed on Day 1. Our results suggest that progressive neuronal damage and loss, AIF signaling pathway-dependent programmed cell death, and limited neuroplastic changes occur in the rat thalamus during the first week after LFPI induction.

A single dose of PPARγ agonist pioglitazone reduces cortical oxidative damage and microglial reaction following lateral fluid percussion brain injury in rats

Neuroprotective actions of the peroxisome proliferator-activated receptor-γ (PPARγ) agonists have been observed in various animal models of the brain injuries. In this study we examined the effects of a single dose of pioglitazone on oxidative and inflammatory parameters as well as on neurodegeneration and the edema formation in the rat parietal cortex following traumatic brain injury (TBI) induced by the lateral fluid percussion injury (LFPI) method. Pioglitazone was administered in a dose of 1mg/kg at 10min after the brain trauma. The animals of the control group were sham-operated and injected by vehicle. The rats were decapitated 24h after LFPI and their parietal cortices were analyzed by biochemical and histological methods. Cortical edema was evaluated in rats sacrificed 48h following TBI. Brain trauma caused statistically significant oxidative damage of lipids and proteins, an increase of glutathione peroxidase (GSH-Px) activity, the cyclooxygenase-2 (COX-2) overexpression, reactive astrocytosis, the microglia activation, neurodegeneration, and edema, but it did not influence the superoxide dismutase activity and the expressions of interleukin-1 beta, interleukin-6 and tumor necrosis factor-alpha in the rat parietal cortex. Pioglitazone significantly decreased the cortical lipid and protein oxidative damage, increased the GSH-Px activity and reduced microglial reaction. Although a certain degree of the TBI-induced COX-2 overexpression, neurodegeneration and edema decrease was detected in pioglitazone treated rats, it was not significant. In the injured animals, cortical reactive astrocytosis was unchanged by the tested PPARγ agonist. These findings demonstrate that pioglitazone, administered only in a single dose, early following LFPI, reduced cortical oxidative damage, increased antioxidant defense and had limited anti-inflammatory effect, suggesting the need for further studies of this drug in the treatment of TBI.

Significant head accelerations can influence immediate neurological impairments in a murine model of blast-induced traumatic brain injury

Although blast-induced traumatic brain injury (bTBI) is well recognized for its significance in the military population, the unique mechanisms of primary bTBI remain undefined. Animate models of primary bTBI are critical for determining these potentially unique mechanisms, but the biomechanical characteristics of many bTBI models are poorly understood. In this study, we examine some common shock tube configurations used to study blast-induced brain injury in the laboratory and define the optimal configuration to minimize the effect of torso overpressure and blast-induced head accelerations. Pressure transducers indicated that a customized animal holder successfully reduced peak torso overpressures to safe levels across all tested configurations. However, high speed video imaging acquired during the blast showed significant head accelerations occurred when animals were oriented perpendicular to the shock tube axis. These findings of complex head motions during blast are similar to previous reports [Goldstein et al., 2012, "Chronic Traumatic Encephalopathy in Blast-Exposed Military Veterans and a Blast Neurotrauma Mouse Model," Sci. Transl. Med., 4(134), 134ra160; Sundaramurthy et al., 2012, "Blast-Induced Biomechanical Loading of the Rat: An Experimental and Anatomically Accurate Computational Blast Injury Model," J. Neurotrauma, 29(13), pp. 2352-2364; Svetlov et al., 2010, "Morphologic and Biochemical Characterization of Brain Injury in a Model of Controlled Blast Overpressure Exposure," J. Trauma, 69(4), pp. 795-804]. Under the same blast input conditions, minimizing head acceleration led to a corresponding elimination of righting time deficits. However, we could still achieve righting time deficits under minimal acceleration conditions by significantly increasing the peak blast overpressure. Together, these data show the importance of characterizing the effect of blast overpressure on head kinematics, with the goal of producing models focused on understanding the effects of blast overpressure on the brain without the complicating factor of superimposed head accelerations.

The acute phase of mild traumatic brain injury is characterized by a distance-dependent neuronal hypoactivity

The consequences of mild traumatic brain injury (TBI) on neuronal functionality are only now being elucidated. We have now examined the changes in sensory encoding in the whisker-recipient barrel cortex and the brain tissue damage in the acute phase (24 h) after induction of TBI (n=9), with sham controls receiving surgery only (n=5). Injury was induced using the lateral fluid percussion injury method, which causes a mixture of focal and diffuse brain injury. Both population and single cell neuronal responses evoked by both simple and complex whisker stimuli revealed a suppression of activity that decreased with distance from the locus of injury both within a hemisphere and across hemispheres, with a greater extent of hypoactivity in ipsilateral barrel cortex compared with contralateral cortex. This was coupled with an increase in spontaneous output in Layer 5a, but only ipsilateral to the injury site. There was also disruption of axonal integrity in various regions in the ipsilateral but not contralateral hemisphere. These results complement our previous findings after mild diffuse-only TBI induced by the weight-drop impact acceleration method where, in the same acute post-injury phase, we found a similar depth-dependent hypoactivity in sensory cortex. This suggests a common sequelae of events in both diffuse TBI and mixed focal/diffuse TBI in the immediate post-injury period that then evolve over time to produce different long-term functional outcomes.

Electrophysiological monitoring of injury progression in the rat cerebellar cortex

The changes of excitability in affected neural networks can be used as a marker to study the temporal course of traumatic brain injury (TBI). The cerebellum is an ideal platform to study brain injury mechanisms at the network level using the electrophysiological methods. Within its crystalline morphology, the cerebellar cortex contains highly organized topographical subunits that are defined by two main inputs, the climbing (CFs) and mossy fibers (MFs). Here we demonstrate the use of cerebellar evoked potentials (EPs) mediated through these afferent systems for monitoring the injury progression in a rat model of fluid percussion injury (FPI). A mechanical tap on the dorsal hand was used as a stimulus, and EPs were recorded from the paramedian lobule (PML) of the posterior cerebellum via multi-electrode arrays (MEAs). Post-injury evoked response amplitudes (EPAs) were analyzed on a daily basis for 1 week and compared with pre-injury values. We found a trend of consistently decreasing EPAs in all nine animals, losing as much as 72 ± 4% of baseline amplitudes measured before the injury. Notably, our results highlighted two particular time windows; the first 24 h of injury in the acute period and day-3 to day-7 in the delayed period where the largest drops (~50% and 24%) were observed in the EPAs. In addition, cross-correlations of spontaneous signals between electrode pairs declined (from 0.47 ± 0.1 to 0.35 ± 0.04, p < 0.001) along with the EPAs throughout the week of injury. In support of the electrophysiological findings, immunohistochemical analysis at day-7 post-injury showed detectable Purkinje cell loss at low FPI pressures and more with the largest pressures used. Our results suggest that sensory evoked potentials (SEPs) recorded from the cerebellar surface can be a useful technique to monitor the course of cerebellar injury and identify the phases of injury progression even at mild levels.

Accumulation of connective tissue growth factor+ cells during the early phase of rat traumatic brain injury

BACKGROUND

Glial scar formation is a common histopathological feature of traumatic brain injury (TBI). Astrogliosis and expression of transforming growth factor beta (TGF-β) are key components of scar formation and blood-brain barrier modulation. Connective tissue growth factor (CTGF) is considered a cytokine mediating the effects of TGF-β.

METHODS

Here, we studied the CTGF expression in an open-skull weight-drop-induced TBI, with a focus on the early phase, most amenable to therapy.

RESULTS

In normal rat brains of our study, CTGF+ cells were rarely observed. Significant parenchymal accumulation of CTGF+ non-neuron cells was observed 72 h post-TBI and increased continuously during the investigating time. We also observed that the accumulated CTGF+ non-neuron cells were mainly distributed in the perilesional areas and showed activated astrocyte phenotypes with typical stellate morphologic characteristics.

CONCLUSION

Our observations demonstrated the time-dependent and lesion-associated accumulation of cellular CTGF expression in TBI, suggesting a pathological role of CTGF in TBI.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/3963462091241165.

Old dog, new tricks: the attentional set-shifting test as a novel cognitive behavioral task after controlled cortical impact injury

Cognitive impairment associated with prefrontal cortical dysfunction is a major component of disability in traumatic brain injury (TBI) survivors. Specifically, deficits of cognitive flexibility and attentional set-shifting are present across all levels of injury severity. Though alterations in spatial learning have been extensively described in experimental models of TBI, studies investigating more complex cognitive deficits are relatively scarce. Hence, the aim of this preclinical study was to expand on this important issue by evaluating the effect of three injury levels on executive function and behavioral flexibility performance as assessed using an attentional set-shifting test (AST). Isoflurane-anesthetized male rats received a controlled cortical impact (CCI) injury (2.6, 2.8, and 3.0 mm cortical depth at 4 m/sec) or sham injury, whereas an additional group had no surgical manipulation (naïve). Four weeks postsurgery, rats were tested on the AST, which involved a series of discriminative tasks of increasing difficulty, such as simple and compound discriminations, stimulus reversals, and intra- and extradimensional (ED) shifts. TBI produced accompanying impact depth-dependent increases in cortical lesion volumes, with the 3.0-mm cortical depth group displaying significantly larger injury volumes than the 2.6-mm group (p=0.05). Further, injury severity-induced deficits in ED set-shifting and stimulus reversals, as well as increases in total response error rates and total set loss errors, were observed. These novel findings demonstrate executive function and behavioral flexibility deficits in our animal model of CCI injury and provide the impetus to integrate the AST in the standard neurotrauma behavioral battery to further evaluate cognitive dysfunction after TBI. Ongoing experiments in our laboratory are assessing AST performance after pharmacological and rehabilitative therapies post-TBI, as well as elucidating possible mechanisms underlying the observed neuropsychological deficits.

Elucidating the severity of preclinical traumatic brain injury models: a role for functional assessment?

BACKGROUND

Concussion remains a symptom-based diagnosis clinically, yet preclinical studies investigating traumatic brain injury, of which concussion is believed to represent a "mild" form, emphasize histological end points with functional assessments often minimized or ignored all together. Recently, clinical studies have identified the importance of cognitive and neuropsychiatric symptoms, in addition to somatic concerns, following concussion. How these findings may translate to preclinical studies is unclear at present.

OBJECTIVE

To address the contrasting end points used clinically compared with those in preclinical studies and the potential role of functional assessments in a commonly used model of diffuse axonal injury (DAI).

METHODS

Animals were subjected to DAI by the use of the impact-acceleration model. Functional and behavioral assessments were conducted during 1 week following DAI before the completion of the histological assessment at 1 week post-DAI.

RESULTS

We show, despite the suggestion that this model represents concussive injury, no functional impairments as determined by using the common measures of motor, sensorimotor, cognitive, and neuropsychiatric function following injury over the course of 1 week. The lack of functional deficits is in sharp contrast to neuropathological findings indicating neural degeneration, astrocyte reactivity, and microglial activation.

CONCLUSION

Future studies are needed to identify functional assessments, neurophysiologic techniques, and imaging assessments more apt to distinguish differences following so-called "mild" traumatic brain injury in preclinical models and determine whether these models are truly studying concussive or subconcussive injury. These studies are needed not only to understand the mechanism of injury and production of subsequent deficits, but also to rigorously evaluate potential therapeutic agents.

Functional assessment of long-term deficits in rodent models of traumatic brain injury

Traumatic brain injury (TBI) ranks as the leading cause of mortality and disability in the young population worldwide. The annual US incidence of TBI in the general population is estimated at 1.7 million per year, with an estimated financial burden in excess of US$75 billion a year in the USA alone. Despite the prevalence and cost of TBI to individuals and society, no treatments have passed clinical trial to clinical implementation. The rapid expansion of stem cell research and technology offers an alternative to traditional pharmacological approaches targeting acute neuroprotection. However, preclinical testing of these approaches depends on the selection and characterization of appropriate animal models. In this article we consider the underlying pathophysiology for the focal and diffuse TBI subtypes, discuss the existing preclinical TBI models and functional outcome tasks used for assessment of injury and recovery, identify criteria particular to preclinical animal models of TBI in which stem cell therapies can be tested for safety and efficacy, and review these criteria in the context of the existing TBI literature. We suggest that 2 months post-TBI is the minimum period needed to evaluate human cell transplant efficacy and safety. Comprehensive review of the published TBI literature revealed that only 32% of rodent TBI papers evaluated functional outcome ≥1 month post-TBI, and only 10% evaluated functional outcomes ≥2 months post-TBI. Not all published papers that evaluated functional deficits at a minimum of 2 months post-TBI reported deficits; hence, only 8.6% of overall TBI papers captured in this review demonstrated functional deficits at 2 months or more postinjury. A 2-month survival and assessment period would allow sufficient time for differentiation and integration of human neural stem cells with the host. Critically, while trophic effects might be observed at earlier time points, it will also be important to demonstrate the sustainability of such an effect, supporting the importance of an extended period of in vivo observation. Furthermore, regulatory bodies will likely require at least 6 months survival post-transplantation for assessment of toxicology/safety, particularly in the context of assessing cell abnormalities.

Erythropoietin improves motor and cognitive deficit, axonal pathology, and neuroinflammation in a combined model of diffuse traumatic brain injury and hypoxia, in association with upregulation of the erythropoietin receptor

Background

Diffuse axonal injury is a common consequence of traumatic brain injury (TBI) and often co-occurs with hypoxia, resulting in poor neurological outcome for which there is no current therapy. Here, we investigate the ability of the multifunctional compound erythropoietin (EPO) to provide neuroprotection when administered to rats after diffuse TBI alone or with post-traumatic hypoxia.

Methods

Sprague–Dawley rats were subjected to diffuse traumatic axonal injury (TAI) followed by 30 minutes of hypoxic (Hx, 12% O₂) or normoxic ventilation, and were administered recombinant human EPO-α (5000 IU/kg) or saline at 1 and 24 hours post-injury. The parameters examined included: 1) behavioural and cognitive deficit using the Rotarod, open field and novel object recognition tests; 2) axonal pathology (NF-200); 3) callosal degradation (hematoxylin and eosin stain); 3) dendritic loss (MAP2); 4) expression and localisation of the EPO receptor (EpoR); 5) activation/infiltration of microglia/macrophages (CD68) and production of IL-1β.

Results

EPO significantly improved sensorimotor and cognitive recovery when administered to TAI rats with hypoxia (TAI + Hx). A single dose of EPO at 1 hour reduced axonal damage in the white matter of TAI + Hx rats at 1 day by 60% compared to vehicle. MAP2 was decreased in the lateral septal nucleus of TAI + Hx rats; however, EPO prevented this loss, and maintained MAP2 density over time. EPO administration elicited an early enhanced expression of EpoR 1 day after TAI + Hx compared with a 7-day peak in vehicle controls. Furthermore, EPO reduced IL-1β to sham levels 2 hours after TAI + Hx, concomitant to a decrease in CD68 positive cells at 7 and 14 days.

Conclusions

When administered EPO, TAI + Hx rats had improved behavioural and cognitive performance, attenuated white matter damage, resolution of neuronal damage spanning from the axon to the dendrite, and suppressed neuroinflammation, alongside enhanced expression of EpoR. These data provide compelling evidence of EPO’s neuroprotective capability. Few benefits were observed when EPO was administered to TAI rats without hypoxia, indicating that EPO’s neuroprotective capacity is bolstered under hypoxic conditions, which may be an important consideration when EPO is employed for neuroprotection in the clinic.

Lesional accumulation of heme oxygenase-1+ microglia/macrophages in rat traumatic brain injury

Heme oxygenase-1 (HO-1) is an inducible rate-limiting enzyme for heme degradation. Here, we studied the HO-1 expression in an open-skull weight-drop-induced traumatic brain injury, with a focus on the early phase, most amenable to therapy. In normal rat brains of our study, HO-1 cells were rarely observed. Significant parenchymal accumulation of HO-1 non-neuron cells was observed 18 h post-traumatic brain injury and increased continuously during the investigating time. We also observed that the accumulated HO-1 non-neuron cells were mainly distributed in the perilesional areas and showed activated microglia/macrophage phenotypes with ramified or amoeboid morphologic characteristics. Further double-labeling experiments showed that most HO-1 non-neuron cells coexpressed CD68 and CD163, but not glial fibrillary acid protein. Our data suggest that HO-1 expression defines a subtype of activated microglia/macrophages involved in the early processes following traumatic brain injury.

Loss of Acid sensing ion channel-1a and bicarbonate administration attenuate the severity of traumatic brain injury

Traumatic brain injury (TBI) is a common cause of morbidity and mortality in people of all ages. Following the acute mechanical insult, TBI evolves over the ensuing minutes and days. Understanding the secondary factors that contribute to TBI might suggest therapeutic strategies to reduce the long-term consequences of brain trauma. To assess secondary factors that contribute to TBI, we studied a lateral fluid percussion injury (FPI) model in mice. Following FPI, the brain cortex became acidic, consistent with data from humans following brain trauma. Administering HCO₃⁻ after FPI prevented the acidosis and reduced the extent of neurodegeneration. Because acidosis can activate acid sensing ion channels (ASICs), we also studied ASIC1a^−/− mice and found reduced neurodegeneration after FPI. Both HCO₃⁻ administration and loss of ASIC1a also reduced functional deficits caused by FPI. These results suggest that FPI induces cerebral acidosis that activates ASIC channels and contributes to secondary injury in TBI. They also suggest a therapeutic strategy to attenuate the adverse consequences of TBI.

Medial septal nucleus theta frequency deep brain stimulation improves spatial working memory after traumatic brain injury

More than 5,000,000 survivors of traumatic brain injury (TBI) live with persistent cognitive deficits, some of which likely derive from hippocampal dysfunction. Oscillatory activity in the hippocampus is critical for normal learning and memory functions, and can be modulated using deep brain stimulation techniques. In this pre-clinical study, we demonstrate that lateral fluid percussion TBI results in the attenuation of hippocampal theta oscillations in the first 6 days after injury, which correlate with deficits in the Barnes maze spatial working memory task. Theta band stimulation of the medial septal nucleus (MSN) results in a transient increase in hippocampal theta activity, and when delivered 1 min prior to training in the Barnes maze, it significantly improves spatial working memory. These results suggest that MSN theta stimulation may be an effective neuromodulatory technique for treatment of persistent learning and memory deficits after TBI.

Characterising effects of impact velocity on brain and behaviour in a model of diffuse traumatic axonal injury

The velocity of impact between an object and the human head is a critical factor influencing brain injury outcomes but has not been explored in any detail in animal models. Here we provide a comprehensive overview of the interplay between impact velocity and injury severity in a well-established weight-drop impact acceleration (WDIA) model of diffuse brain injury in rodents. We modified the standard WDIA model to produce impact velocities of 5.4, 5.85 and 6.15 m/s while keeping constant the weight and the drop height. Gradations in impact velocity produced progressive degrees of injury severity measured behaviourally, electrophysiologically and anatomically, with the former two methods showing greater sensitivity to changes in impact velocity. There were impact velocity-dependent reductions in sensorimotor performance and in cortical depth-related depression of sensory cortex responses; however axonal injury (demonstrated by immunohistochemistry for β-amyloid precursor protein and neurofilament heavy-chain) was discernible only at the highest impact velocity. We conclude that the WDIA model is capable of producing graded axonal injury in a repeatable manner, and as such will prove useful in the study of the biomechanics, pathophysiology and potential treatment of diffuse axonal injury.

Resuscitation from experimental traumatic brain injury by magnolol therapy

BACKGROUND

The purpose of the present study was to determine whether magnolol, a free radical scavenger, mitigates the deleterious effects of traumatic brain injury (TBI).

MATERIAL AND METHODS

Traumatic brain injuries were induced in anesthetized male Sprague-Dawley rats using fluid percussion, and the rats were divided into groups treated with magnolol (2 mg/kg, intravenously) or vehicle. A group of rats that did not undergo TBI induction was also studied as controls. Biomarkers of TBI, including glycerol and 2,3-dihydroxybenzoic acid, were evaluated by microdialysis. Infraction volume, extent of neuronal apoptosis, and antiapoptosis factor transforming growth factor β1 (TGF-β1) were also measured. Functional outcomes were assessed by motor assays.

RESULTS

Compared with the rats without TBI, the animals with TBI exhibited higher hippocampal glycerol and 2,3-dihydroxybenzoic acid. Relative to the vehicle-treated group, the magnolol-treated group showed decreased hippocampal levels of glycerol and hydroxyl radical levels. The magnolol-treated rats also exhibited decreased cerebral infarction volume and neuronal apoptosis and increased antiapoptosis-associated factor TGF-β1 expression. These effects were translated into improved motor function post TBI.

CONCLUSIONS

Our results suggest that intravenous magnolol injection mitigates the deleterious effects of TBI in rats based on its potent free radical scavenging capability, and the mechanism of anti-neuronal apoptosis is partly due to an increase in TGF-β1 expression in the ischemic cortex.

Analysis of functional pathways altered after mild traumatic brain injury

Concussive injury (or mild traumatic brain injury; mTBI) can exhibit features of focal or diffuse injury patterns. We compared and contrasted the cellular and molecular responses after mild controlled cortical impact (mCCI; a focal injury) or fluid percussion injury (FPI; a diffuse injury) in rats. The rationale for this comparative analysis was to investigate the brain's response to mild diffuse versus mild focal injury to identify common molecular changes triggered by these injury modalities and to determine the functional pathways altered after injury that may provide novel targets for therapeutic intervention. Microarrays containing probes against 21,792 unique messenger RNAs (mRNAs) were used to investigate the changes in cortical mRNA expression levels at 3 and 24 h postinjury. Of the 354 mRNAs with significantly altered expression levels after mCCI, over 89% (316 mRNAs) were also contained within the mild FPI (mFPI) data set. However, mFPI initiated a more widespread molecular response, with over 2300 mRNAs differentially expressed. Bioinformatic analysis of annotated gene ontology molecular function and biological pathway terms showed a significant overrepresentation of genes belonging to inflammation, stress, and signaling categories in both data sets. We therefore examined changes in the protein levels of a panel of 23 cytokines and chemokines in cortical extracts using a Luminex-based bead immunoassay and detected significant increases in macrophage inflammatory protein (MIP)-1α (CCL3), GRO-KC (CXCL1), interleukin (IL)-1α, IL-1β, and IL-6. Immunohistochemical localization of MIP-1α and IL-1β showed marked increases at 3 h postinjury in the cortical vasculature and microglia, respectively, that were largely resolved by 24 h postinjury. Our findings demonstrate that both focal and diffuse mTBI trigger many shared pathobiological processes (e.g., inflammatory responses) that could be targeted for mechanism-based therapeutic interventions.

Administration of MS-275 improves cognitive performance and reduces cell death following traumatic brain injury in rats

AIMS

The MS-275 is a selective inhibitor of class I histone deacetylases (HDACs), which has been reported as a potential strategy in some central nervous system diseases associated with neurodegeneration and disturbed learning. However, its role in traumatic brain injury is not well defined. In this study, we examined the behavioral-cognitive performance as well as histology outcome in adult rats to evaluate whether postinjury administration of MS-275 (15 and 45 mg/kg) would provide neuroprotection benefits and ameliorate cognitive deficits following fluid percussion injury.

METHODS

Traumatic brain injury (˜2.15 ATMs) was produced using a fluid percussion device with the lateral orientation. MS-275 was administered (15 and 45 mg/kg) systemically once daily for 7 days starting at 30 min after lateral fluid percussion TBI. Acquisition of spatial learning and memory retention was assessed using the Morris water maze (MWM) on days 10-14 after TBI. Brain tissues were collected and stained with Fluoro-Jade B histofluorescence (for degenerating neurons) at 24 h after injury and cresyl violet (for long-term neuronal survival) on day 14 postinjury.

RESULTS

Behavioral outcome after TBI revealed MS-275 treatment groups, at all doses examined, performed significantly better in the Morris Water Maze (P < 0.001). Acute histology analysis demonstrated that 45 mg/kg MS-275 significantly reduced the number of degenerating neurons in the ipsilateral CA2-3 hippocampus at 24 h postinjury (P = 0.007). There was a trend for MS-275 to increase the survival of neurons in the CA2-3 hippocampus on 14 days after TBI (P = 0.164).

CONCLUSION

Our present data highlight the fact that MS-275 may provide neuroprotective effect and improve cognitive performance after TBI. We concluded that MS-275 is a potential novel treatment and will have an ameliorative effect on some of the pathological features associated with TBI.

Treatment of mild traumatic brain injury with an erythropoietin-mimetic peptide

Mild traumatic brain injury (mTBI) results in an estimated 75-90% of the 1.7 million TBI-related emergency room visits each year. Post-concussion symptoms, which can include impaired memory problems, may persist for prolonged periods of time in a fraction of these cases. The purpose of this study was to determine if an erythropoietin-mimetic peptide, pyroglutamate helix B surface peptide (pHBSP), would improve neurological outcomes following mTBI. Sixty-four rats were randomly assigned to pHBSP or control (inactive peptide) 30 μg/kg IP every 12 h for 3 days, starting at either 1 hour (early treatment) or 24 h (delayed treatment), after mTBI (cortical impact injury 3 m/sec, 2.5 mm deformation). Treatment with pHBSP resulted in significantly improved performance on the Morris water maze task. Rats that received pHBSP required 22.3±1.3 sec to find the platform, compared to 26.3±1.3 sec in control rats (p=0.022). The rats that received pHBSP also traveled a significantly shorter distance to get to the platform, 5.0±0.3 meters, compared to 6.1±0.3 meters in control rats (p=0.019). Motor tasks were only transiently impaired in this mTBI model, and no treatment effect on motor performance was observed with pHBSP. Despite the minimal tissue injury with this mTBI model, there was significant activation of inflammatory cells identified by labeling with CD68, which was reduced in the pHBSP-treated animals. The results suggest that pHBSP may improve cognitive function following mTBI.

Attenuating inflammation but stimulating both angiogenesis and neurogenesis using hyperbaric oxygen in rats with traumatic brain injury

BACKGROUND

Inflammation, angiogenesis, neurogenesis, and gliosis are involved in traumatic brain injury (TBI). Several studies provide evidence supporting the neuroprotective effect of hyperbaric oxygen (HBO2) therapy in TBI. The aim of this study was to ascertain whether inflammation, angiogenesis, neurogenesis, and gliosis during TBI are affected by HBO2 therapy.

METHODS

Rats were randomly divided into three groups: TBI + NBA (normobaric air: 21% O2 at 1 absolute atmospheres), TBI + HBO2, and Sham operation + NBA. TBI + HBO2 rats received 100% O2 at 2.0 absolute atmospheres for 1 hr/d for three consecutive days. Behavioral tests and biochemical and histologic evaluations were done 4 days after TBI onset.

RESULTS

TBI + NBA rats displayed: (1) motor and cognitive dysfunction; (2) cerebral infarction and apoptosis; (3) activated inflammation (evidenced by increased brain myeloperoxidase activity and higher serum levels of tumor necrosis factor-α); (4) neuronal loss (evidenced by fewer NeuN-positive cells); and (5) gliosis (evidenced by more glial fibrillary protein-positive cells). In TBI + HBO2 rats, HBO2 therapy significantly reduced TBI-induced motor and cognitive dysfunction, cerebral infarction and apoptosis, activated inflammation, neuronal loss, and gliosis. In addition, HBO2 therapy stimulated angiogenesis (evidenced by more bromodeoxyuridine-positive endothelial and vascular endothelial growth factor-positive cells), neurogenesis (evidenced by more bromodeoxyuridine-NeuN double-positive and glial cells-derived neurotrophic factor-positive cells), and overproduction of interleukin-10 (an anti-inflammatory cytokine).

CONCLUSIONS

Collectively, these results suggest that HBO2 therapy may improve outcomes of TBI in rats by inhibiting activated inflammation and gliosis while stimulating both angiogenesis and neurogenesis in the early stage.

Animal model for sport-related concussion; ICP and cognitive function

BACKGROUND

We have recently developed and characterized a rat model of mild traumatic brain injury which simulates the concussive injuries frequently encountered by players in American professional football.

OBJECTIVES

To study the effect of multiple impacts to the head on intracranial pressure, cognitive function, and exploratory behavior.

MATERIALS AND METHODS

The model was employed to cause concussion. Intracranial pressure, cognitive function, and exploratory behavior were examined following the multiple impacts of a 50 or 100 g projectile at a velocity of 9.3 or 11.2 m/s to the helmet protected head.

RESULTS

Intracranial pressure measured at 6 and 10 h, and 1, 2, 3, 5, and 7 days. It was maximally elevated 10 h after impact and returned to the control levels 7 days later. Morris Water Maze assessment, 48 h after impact, revealed impaired cognitive function. Open field testing 2-4 days and 1 and 2 weeks after impacts indicated consistently reduced spontaneous exploratory activity.

CONCLUSION

Multiple impacts to the head raise intracranial pressure and impair cognitive function and exploratory activity in this animal model.

Traumatic brain injury and trichloroethylene exposure interact and produce functional, histological, and mitochondrial deficits

Mitochondria play a pivotal role in the development of pathology associated with Parkinson's disease (PD), traumatic brain injury (TBI), and following exposure to the environmental toxin trichloroethylene (TCE). Evidence from humans indicates that both TBI and TCE can play a role in the development of PD and that each of these insults result in significant mitochondrial dysfunction. In the current studies we hypothesized that exposure to both TCE and TBI would result in increased pathology associated with PD. To test this hypothesis, 16 week old male Fischer 344 rats were administered TCE for either one or two weeks by oral gavage. Following exposure to TCE, rats were subjected to either a sham, mild (1.0mm), or moderate (2.0mm) controlled cortical impact TBI. Given the strong connection between mitochondrial function and PD, TBI, and TCE, tissue from the striatum and substantia nigra were analyzed 6h after the TBI. Neither TCE exposure, TBI, nor the combination of the two insults resulted in mitochondrial deficits at 6h post-TBI in the substantia nigra. Unlike the substantia nigra, the striatum exhibited significant mitochondrial dysfunction. Exposure to TCE alone for two weeks resulted in approximately a 75% reduction in mitochondrial function (p<0.05) in the striatum whereas TBI alone resulted in approximately a 30% reduction in striatal mitochondrial function. Following 1 week exposure to TCE followed by TBI, there was a significant reduction (50%) in mitochondrial function (p<0.05) which required the presence of both insults. Beginning 12 days after the injury significant motor impairment was observed with Rotarod testing. Animals exposed to TCE and a moderate TBI exhibited performance which was approximately 50% of controls (p<0.01). Cylinder testing revealed that at 30 days post-injury animals exposed to TCE and a moderate TBI also had about a 34% reduction in the usage of the contralateral fore paw and this impairment was significantly worse than both control animals and animals exposed to TCE and a mild TBI (p<0.05). At 30 days post-injury there was a 13-17% reduction in the number of tyrosine hydroxylase (TH) positive neurons in the substantia nigra (p<0.05), which was the result of protein loss and not cell death. Loss of TH positive neurons did not result in changes in striatal TH fiber density or levels of the dopamine transporter or type-2 dopamine receptor. Additionally, exposure to TCE prior to the TBI did not increase the loss of cortical tissue, indicating regional specificity for TCE induced deficits. These studies provide further evidence for the connection between TCE, TBI, and PD and lend support to the concept that PD develops from a multifactorial injury scenario.

Microsurgical anatomy of the anterior commissure: correlations with diffusion tensor imaging fiber tracking and clinical relevance

BACKGROUND

Detailed anatomy of the anterior commissure is unknown in the literature.

OBJECTIVE

To describe the anterior commissure with the use of a fiber dissection technique by focusing on the morphology (length and breadth of the 2 portions), the course, and the relations with neighboring fasciculi, particularly in the temporal stem.

METHODS

We dissected 8 previously frozen, formalin-fixed human brains under the operating microscope using the fiber dissection described by Klingler. Lateral, inferior, and medial approaches were made.

RESULTS

The anterior olfactive limb of the anterior commissure was sometimes absent during dissection. The cross-sectional 3-dimensional magnetic resonance rendering images showed that fibers of the anterior commissure curved laterally within the basal forebrain. The tip of the temporal limb of the anterior commissure was intermingled with other fasciculi in various directions to form a dense 3-dimensional network.

CONCLUSION

Functional anatomy and comparative anatomy are described. The anterior commissure can be involved in various pathologies such as diffuse axonal injury, schizophrenia, and cerebral tumoral dissemination.

Post-traumatic hypoxia exacerbates neuronal cell death in the hippocampus

Hypoxia frequently occurs in patients with traumatic brain injury (TBI) and is associated with increased morbidity and mortality. This study examined the effects of immediate or delayed post-traumatic hypoxia (fraction of inspired oxygen [FiO(2)] 11%) on acute neuronal degeneration and long-term neuronal survival in hippocampal fields after moderate fluid percussion injury in rats. In Experiment 1, hypoxia was induced for 15 or 30 min alone or immediately following TBI. In Experiments 2 and 3, 30 min of hypoxia was induced immediately after TBI or delayed until 60 min after TBI. In Experiment 1, acute neurodegeneration was evaluated in the hippocampal fields 24 h after insults using Fluoro-Jade staining and stereological quantification. During hypoxia alone, or in combination with TBI, mean arterial blood pressure was significantly reduced by approximately 30%, followed by a rapid return to normal values upon return to pre-injury FiO(2). Hypoxia alone failed to cause hippocampal neuronal degeneration when measured at 24 h after insult. TBI alone resulted in neuronal degeneration in each ipsilateral hippocampal field, predominantly in CA2-CA3 and the dentate gyrus. Compared to TBI alone, TBI plus immediate hypoxia for either 15 or 30 min significantly increased neuronal loss in most ipsilateral hippocampal fields and in the contralateral hilus and dentate gyrus. In Experiment 2, TBI plus hypoxia delayed 30 min significantly increased degeneration only in ipsilateral CA2-CA3. In Experiment 3, 30 min of immediate hypoxia significantly reduced the numbers of surviving neurons in the CA3 at 14 days after TBI. The greatly increased vulnerability in all hippocampal fields by immediate 30 min post-traumatic hypoxia provides a relevant model of TBI complicated with hypoxia/hypotension. These data underscore the significance of the secondary insult, the necessity to better characterize the range of injuries experienced by the TBI patient, and the importance of strictly avoiding hypoxia in the early management of TBI patients.

Microenvironment changes in mild traumatic brain injury

Traumatic brain injury (TBI) is a major public-health problem for which mild TBI (MTBI) makes up majority of the cases. MTBI is a poorly-understood health problem and can persist for years manifesting into neurological and non-neurological problems that can affect functional outcome. Presently, diagnosis of MTBI is based on symptoms reporting with poor understanding of ongoing pathophysiology, hence precluding prognosis and intervention. Other than rehabilitation, there is still no pharmacological treatment for the treatment of secondary injury and prevention of the development of cognitive and behavioural problems. The lack of external injuries and absence of detectable brain abnormalities lend support to MTBI developing at the cellular and biochemical level. However, the paucity of suitable and validated non-invasive methods for accurate diagnosis of MTBI poses as a substantial challenge. Hence, it is crucial that a clinically useful evaluation and management procedure be instituted for MTBI that encompasses both molecular pathophysiology and functional outcome. The acute microenvironment changes post-MTBI presents an attractive target for modulation of MTBI symptoms and the development of cognitive changes later in life.

Hypersensitive glutamate signaling correlates with the development of late-onset behavioral morbidity in diffuse brain-injured circuitry

In diffuse brain-injured rats, robust sensory sensitivity to manual whisker stimulation develops over 1 month post-injury, comparable to agitation expressed by brain-injured individuals with overstimulation. In the rat, whisker somatosensation relies on thalamocortical glutamatergic relays between the ventral posterior medial (VPM) thalamus and barrel fields of somatosensory cortex (S1BF). Using novel glutamate-selective microelectrode arrays coupled to amperometry, we test the hypothesis that disrupted glutamatergic neurotransmission underlies the whisker sensory sensitivity associated with diffuse brain injury. We report hypersensitive glutamate neurotransmission that parallels and correlates with the development of post-traumatic sensory sensitivity. Hypersensitivity is demonstrated by significant 110% increases in VPM extracellular glutamate levels, and 100% increase in potassium-evoked glutamate release in the VPM and S1BF, with no change in glutamate clearance. Further, evoked glutamate release showed 50% greater sensitivity to a calcium channel antagonist in brain-injured over uninjured VPM. In conjunction with no changes in glutamate transporter gene expression and exogenous glutamate clearance efficiency, these data support a presynaptic origin for enduring post-traumatic circuit alterations. In the anatomically-distinct whisker circuit, the injury-induced functional alterations correlate with the development of late-onset behavioral morbidity. Effective therapies to modulate presynaptic glutamate function in diffuse-injured circuits may translate into improvements in essential brain function and behavioral performance in other brain-injured circuits in rodents and in humans.

Cognitive dysfunction associated with diabetic ketoacidosis in rats

BACKGROUND

Type 1 diabetes mellitus in children may be associated with neurocognitive deficits of unclear cause. A recent retrospective study in children suggested possible associations between diabetic ketoacidosis (DKA) and decreased memory. The current investigation was undertaken to determine whether cognitive deficits could be detected after a single episode of DKA in an animal model.

METHODS

Streptozotocin was used to induce diabetes in juvenile rats, and rats were then treated with subcutaneous insulin injections. In one group, insulin was subsequently withdrawn to allow development of DKA, which was then treated with insulin and saline. After recovery from DKA, subcutaneous insulin injections were re-started. In the diabetes control group, rats continued to receive subcutaneous insulin and underwent sham procedures identical to the DKA group. One week after recovery, cognitive function was tested using the Morris Water Maze, a procedure that requires rats to locate a hidden platform in a water pool using visual cues. During a 10 day period, mean time to locate the platform (latency) during 4 trials per day was recorded.

RESULTS

Comparison of latency curves demonstrated longer mean latency times on days 7 and 8 in the DKA group indicating delayed learning compared to diabetic controls.

CONCLUSIONS

These data demonstrate that a single DKA episode results in measurable deficits in learning in rats, consistent with findings that DKA may contribute to neurocognitive deficits in children with type 1 diabetes.

Fluorophilia: fluorophore-containing compounds adhere non-specifically to injured neurons

Ionic (free) zinc (Zn(2+)) is implicated in apoptotic neuronal degeneration and death. In our attempt to examine the effects of Zn(2+) in neurodegeneration following brain injury, we serendipitously discovered that injured neurons bind fluorescein moieties, either alone or as part of an indicator dye, in histologic sections. This phenomenon, that we have termed "fluorophilia", is analogous to the ability of degenerating neuronal somata and axons to bind silver ions (argyrophilia - the basis of silver degeneration stains). To provide evidence that fluorophilia occurs in sections of brain tissue, we used a wide variety of indicators such as Fluoro-Jade (FJ), a slightly modified fluorescein sold as a marker for degenerating neurons; Newport Green, a fluorescein-containing Zn(2+) probe; Rhod-5N, a rhodamine-containing Ca(2+) probe; and plain fluorescein. All yielded remarkably similar staining of degenerating neurons in the traumatic brain-injured tissue with the absence of staining in our sham-injured brains. Staining of presumptive injured neurons by these agents was not modified when Zn(2+) in the brain section was removed by prior chelation with EDTA or TPEN, whereas staining by a non-fluorescein containing Zn(2+) probe, N-(6-methoxy-8-quinolyl)-p-toluenesulfonamide (TSQ), was suppressed by prior chelation. Thus, certain fluorophore-containing compounds nonspecifically stain degenerating neuronal tissue in histologic sections and may not reflect the presence of Zn(2+). This may be of concern to researchers using indicator dyes to detect metals in brain tissue sections. Further experiments may be advised to clarify whether Zn(2+)-binding dyes bind more specifically in intact neurons in culture or organotypic slices.

Post-traumatic hypoxia exacerbates neurological deficit, neuroinflammation and cerebral metabolism in rats with diffuse traumatic brain injury

Background

The combination of diffuse brain injury with a hypoxic insult is associated with poor outcomes in patients with traumatic brain injury. In this study, we investigated the impact of post-traumatic hypoxia in amplifying secondary brain damage using a rat model of diffuse traumatic axonal injury (TAI). Rats were examined for behavioral and sensorimotor deficits, increased brain production of inflammatory cytokines, formation of cerebral edema, changes in brain metabolism and enlargement of the lateral ventricles.

Methods

Adult male Sprague-Dawley rats were subjected to diffuse TAI using the Marmarou impact-acceleration model. Subsequently, rats underwent a 30-minute period of hypoxic (12% O₂/88% N₂) or normoxic (22% O₂/78% N₂) ventilation. Hypoxia-only and sham surgery groups (without TAI) received 30 minutes of hypoxic or normoxic ventilation, respectively. The parameters examined included: 1) behavioural and sensorimotor deficit using the Rotarod, beam walk and adhesive tape removal tests, and voluntary open field exploration behavior; 2) formation of cerebral edema by the wet-dry tissue weight ratio method; 3) enlargement of the lateral ventricles; 4) production of inflammatory cytokines; and 5) real-time brain metabolite changes as assessed by microdialysis technique.

Results

TAI rats showed significant deficits in sensorimotor function, and developed substantial edema and ventricular enlargement when compared to shams. The additional hypoxic insult significantly exacerbated behavioural deficits and the cortical production of the pro-inflammatory cytokines IL-6, IL-1β and TNF but did not further enhance edema. TAI and particularly TAI+Hx rats experienced a substantial metabolic depression with respect to glucose, lactate, and glutamate levels.

Conclusion

Altogether, aggravated behavioural deficits observed in rats with diffuse TAI combined with hypoxia may be induced by enhanced neuroinflammation, and a prolonged period of metabolic dysfunction.

Mechanisms of dendritic spine remodeling in a rat model of traumatic brain injury

Traumatic brain injury (TBI), a leading cause of death and disability in the United States, causes potentially preventable damage in part through the dysregulation of neural calcium levels. Calcium dysregulation could affect the activity of the calcium-sensitive phosphatase calcineurin (CaN), with serious implications for neural function. The present study used both an in vitro enzymatic assay and Western blot analyses to characterize the effects of lateral fluid percussion injury on CaN activity and CaN-dependent signaling in the rat forebrain. TBI resulted in an acute alteration of CaN phosphatase activity and long-lasting alterations of its downstream effector, cofilin, an actin-depolymerizing protein. These changes occurred bilaterally in the neocortex and hippocampus, appeared to persist for hours after injury, and coincided with synapse degeneration, as suggested by a loss of the excitatory post-synaptic protein PSD-95. Interestingly, the effect of TBI on cofilin in some brain regions was blocked by a single bolus of the CaN inhibitor FK506, given 1 h post-TBI. Overall, these findings suggest a loss of synapse stability in both hemispheres of the laterally-injured brain, and offer evidence for region-specific, CaN-dependent mechanisms.

Concussive brain trauma in the mouse results in acute cognitive deficits and sustained impairment of axonal function

Concussive brain injury (CBI) accounts for approximately 75% of all brain-injured people in the United States each year and is particularly prevalent in contact sports. Concussion is the mildest form of diffuse traumatic brain injury (TBI) and results in transient cognitive dysfunction, the neuropathologic basis for which is traumatic axonal injury (TAI). To evaluate the structural and functional changes associated with concussion-induced cognitive deficits, adult mice were subjected to an impact on the intact skull over the midline suture that resulted in a brief apneic period and loss of the righting reflex. Closed head injury also resulted in an increase in the wet weight:dry weight ratio in the cortex suggestive of edema in the first 24 h, and the appearance of Fluoro-Jade-B-labeled degenerating neurons in the cortex and dentate gyrus of the hippocampus within the first 3 days post-injury. Compared to sham-injured mice, brain-injured mice exhibited significant deficits in spatial acquisition and working memory as measured using the Morris water maze over the first 3 days (p<0.001), but not after the fourth day post-injury. At 1 and 3 days post-injury, intra-axonal accumulation of amyloid precursor protein in the corpus callosum and cingulum was accompanied by neurofilament dephosphorylation, impaired transport of Fluoro-Gold and synaptophysin, and deficits in axonal conductance. Importantly, deficits in retrograde transport and in action potential of myelinated axons continued to be observed until 14 days post-injury, at which time axonal degeneration was apparent. These data suggest that despite recovery from acute cognitive deficits, concussive brain trauma leads to axonal degeneration and a sustained perturbation of axonal function.

Hippocampal θ dysfunction after lateral fluid percussion injury

Chronic memory deficits are a major cause of morbidity following traumatic brain injury (TBI). In the rat, the hippocampal theta rhythm is a well-studied correlate of memory function. This study sought to investigate disturbances in hippocampal theta rhythm following lateral fluid percussion injury in the rat. A total of 13 control rats and 12 TBI rats were used. Electrodes were implanted in bilateral hippocampi and an electroencephalogram (EEG) was recorded while the rats explored a new environment, and also while navigating a modified version of the Barnes maze. Theta power and peak theta frequency were significantly attenuated in the injured animals. Further, injured rats were less likely to develop a spatial strategy for Barnes maze navigation compared to control rats. In conclusion, rats sustaining lateral fluid percussion injury demonstrated deficits in hippocampal theta activity. These deficits may contribute to the underlying memory problems seen in chronic TBI.

Post-injury administration of NAAG peptidase inhibitor prodrug, PGI-02776, in experimental TBI

Traumatic brain injury (TBI) leads to a rapid and excessive increase in glutamate concentration in the extracellular milieu, which is strongly associated with excitotoxicity and neuronal degeneration. N-acetylaspartylglutamate (NAAG), a prevalent peptide neurotransmitter in the vertebrate nervous system, is released along with glutamate and suppresses glutamate release by actions at pre-synaptic metabotropic glutamate autoreceptors. Extracellular NAAG is hydrolyzed to N-acetylaspartate and glutamate by peptidase activity. In the present study PGI-02776, a newly designed di-ester prodrug of the urea-based NAAG peptidase inhibitor ZJ-43, was tested for neuroprotective potential when administered intraperitoneally 30 min after lateral fluid percussion TBI in the rat. Stereological quantification of hippocampal CA2-3 degenerating neurons at 24 h post injury revealed that 10 mg/kg PGI-02776 significantly decreased the number of degenerating neurons (p<0.05). Both average latency analysis of Morris water maze performance and assessment of 24-hour memory retention revealed significant differences between sham-TBI and TBI-saline. In contrast, no significant difference was found between sham-TBI and PGI-02776 treated groups in either analysis indicating an improvement in cognitive performance with PGI-02776 treatment. Histological analysis on day 16 post-injury revealed significant cell death in injured animals regardless of treatment. In vitro NAAG peptidase inhibition studies demonstrated that the parent compound (ZJ-43) exhibited potent inhibitory activity while the mono-ester (PGI-02749) and di-ester (PGI-02776) prodrug compounds exhibited moderate and weak levels of inhibitory activity, respectively. Pharmacokinetic assays in uninjured animals found that the di-ester (PGI-02776) crossed the blood-brain barrier. PGI-02776 was also readily hydrolyzed to both the mono-ester (PGI-02749) and the parent compound (ZJ-43) in both blood and brain. Overall, these findings suggest that post-injury treatment with the ZJ-43 prodrug PGI-02776 reduces both acute neuronal pathology and longer term cognitive deficits associated with TBI.

Spatiotemporal pattern of neuronal injury induced by DFP in rats: a model for delayed neuronal cell death following acute OP intoxication

Organophosphate (OP) neurotoxins cause acute cholinergic toxicity and seizures resulting in delayed brain damage and persistent neurological symptoms. Testing novel strategies for protecting against delayed effects of acute OP intoxication has been hampered by the lack of appropriate animal models. In this study, we characterize the spatiotemporal pattern of cellular injury after acute intoxication with the OP diisopropylfluorophosphate (DFP). Adult male Sprague-Dawley rats received pyridostigmine (0.1 mg/kg, im) and atropine methylnitrate (20mg/kg, im) prior to DFP (9 mg/kg, ip) administration. All DFP-treated animals exhibited moderate to severe seizures within minutes after DFP injection but survived up to 72 h. AChE activity was significantly depressed in the cortex, hippocampus, subcortical brain tissue and cerebellum at 1h post-DFP injection and this inhibition persisted for up to 72 h. Analysis of neuronal injury by Fluoro-Jade B (FJB) labeling revealed delayed neuronal cell death in the hippocampus, cortex, amygdala and thalamus, but not the cerebellum, starting at 4h and persisting until 72 h after DFP treatment, although temporal profiles varied between brain regions. At 24h post-DFP injection, the pattern of FJB labeling corresponded to TUNEL staining in most brain regions, and FJB-positive cells displayed reduced NeuN immunoreactivity but were not immunopositive for astrocytic (GFAP), oligodendroglial (O4) or macrophage/microglial (ED1) markers, demonstrating that DFP causes a region-specific delayed neuronal injury mediated in part by apoptosis. These findings indicate the feasibility of this model for testing neuroprotective strategies, and provide insight regarding therapeutic windows for effective pharmacological intervention following acute OP intoxication.

Impaired performance on the angle board test is induced in a model of painful whiplash injury but is only transient in a model of cervical radiculopathy

Although clinical studies report motor impairment associated with some painful injuries of the neck, assessment of motor function in animal models has been largely limited only to studies of direct trauma to the nervous system. The incline plane test was modified to evaluate motor function in two rodent pain models of facet joint distraction (FJD) and nerve root compression (NRC) injury (n = 5/group). Sham groups were also included as controls. Motor function was measured using the modified inclined plane test with rats facing downward before surgery (baseline) and following surgery on days corresponding to when mechanical sensitivity is established and remains elevated. Mean baseline values of the board angle inducing slip for FJD (45.8 ± 3.1°) was significantly greater (p = 0.014) than that for NRC (43.5 ± 2.5°), but baseline measurements did not vary for either group over time. No changes in motor function were found for shams. Motor function after FJD significantly decreased (p < 0.001) at days 1 and 7 after injury. In contrast, at day 1 after NRC injury, slip occurred at significantly lower (p = 0.0016) incline angles, but returned to baseline levels by day 7. These results show motor function impairment is induced following painful FJD and suggest the incline plane test offers utility to evaluate functional deficits in painful injuries.

Brain cooling-stimulated angiogenesis and neurogenesis attenuated traumatic brain injury in rats

BACKGROUND

Although brain cooling has been reported to be effective in improving the outcome after traumatic brain injury (TBI) in rats, the mechanisms of brain cooling-induced neuroprotective actions remain unclear. This study was to test whether angiogenesis and neurogenesis attenuating TBI could be brain cooling stimulated.

METHODS

Anesthetized rats, immediately after the onset of TBI, were divided into two groups and given the brain cooling (infusing 5 mL of 4°C saline via the external jugular vein) or no brain cooling (infusing 5 mL of 37°C saline via the external jugular vein).

RESULTS

Brain cooling without interference with the core temperature in rats significantly attenuated TBI-induced cerebral infarction (90 mm³ vs. 250 mm³) and motor (61 degrees vs. 57 degrees maximal angle) and proprioceptive (14% vs. 42% maximal possible effect) function deficits, significantly reduced TBI-induced neuronal (24 vs. 62 neuronal-specific nuclear [NeuN]-TUNEL double-positive cells) and glial (5 vs. 35 GFAP-TUNEL double-positive cells) apoptosis (increased TUNEL-positive and caspase-3-positive cells), neuronal loss (102 vs. 66 NeuN-positive cells), and gliosis (40 vs. 66 GFAP-positive cells; 66 vs. 89 Iba1-positive cells), and significantly promoted angiogenesis (5-bromodeoxyuridine [BrdU]/endothelial cells vs. 1-BrdU/endothelial cell; 58 vs. 31 vascular endothelial growth factor-positive cells), and neurogenesis (33 vs. 14 BrdU/NeuN positive cells).

CONCLUSIONS

Brain cooling-stimulated angiogenesis and neurogenesis attenuated a fluid percussion TBI in rats.

Beneficial effect of agmatine on brain apoptosis, astrogliosis, and edema after rat transient cerebral ischemia

Background

Although agmatine therapy in a mouse model of transient focal cerebral ischemia is highly protective against neurological injury, the mechanisms underlying the protective effects of agmatine are not fully elucidated. This study aimed to investigate the effects of agmatine on brain apoptosis, astrogliosis and edema in the rats with transient cerebral ischemia.

Methods

Following surgical induction of middle cerebral artery occlusion (MCAO) for 90 min, agmatine (100 mg/kg, i.p.) was injected 5 min after beginning of reperfusion and again once daily for the next 3 post-operative days. Four days after reperfusion, both motor and proprioception functions were assessed and then all rats were sacrificed for determination of brain infarct volume (2, 3, 5-triphenyltetrazolium chloride staining), apoptosis (TUNEL staining), edema (both cerebral water content and amounts of aquaporin-4 positive cells), gliosis (glial fibrillary acidic protein [GFAP]-positive cells), and neurotoxicity (inducible nitric oxide synthase [iNOS] expression).

Results

The results showed that agmatine treatment was found to accelerate recovery of motor (from 55 degrees to 62 degrees) and proprioception (from 54% maximal possible effect to 10% maximal possible effect) deficits and to prevent brain infarction (from 370 mm³ to 50 mm³), gliosis (from 80 GFAP-positive cells to 30 GFAP-positive cells), edema (cerebral water contents decreased from 82.5% to 79.4%; AQP4 positive cells decreased from 140 to 84 per section), apoptosis (neuronal apoptotic cells decreased from 100 to 20 per section), and neurotoxicity (iNOS expression cells decreased from 64 to 7 per section) during MCAO ischemic injury in rats.

Conclusions

The data suggest that agmatine may improve outcomes of transient cerebral ischemia in rats by reducing brain apoptosis, astrogliosis and edema.

Histopathological features of the brain, liver, kidney and spleen following an innovative polytrauma model of the mouse

OBJECT

Among the various introduced experimental traumatic brain injury models, there is a clear paucity of proper experimental polytrauma models. To overcome this experimental gap we introduced such a polytrauma model in the mouse including traumatic brain injury. Here, we report on the histopathological features of the brain, lung, kidney, spleen and liver.

MATERIALS AND METHODS

20 male C57BL mice with a mean weight of 23 g were anesthetized with ketamine and xylazine. The anaesthetized animals were subjected to a controlled cortical impact (CCI) over the left parieto-temporal cortex using rounded-tip impounder for application of a standardized brain injury. Following fracture of the right femur using a guillotine, a volume-controlled hemorrhagic shock was induced. The control groups included animals with CCI only (n=20) and animals with femur fracture plus hemorrhagic shock without CCI (n=20). Subjects were sacrified at 96 h following trauma. Brain, lung, kidney, spleen and liver of the animals underwent histopathological examinations.

RESULTS

The mortality rate at 96 h was 25% in the polytrauma group versus 10% in the control groups. Within the histopathological investigations, polytraumatized animals differ from those with a single trauma (traumatic brain injury or femur fracture with hemorrhagic shock) with various severity.

CONCLUSION

The findings of this study show that such a polytrauma model can be standardized resulting in a reproducible damage. This model fulfills the requirements of a standardized animal model. It allows adequate analogies and inferences to the clinical situation of a polytrauma in humans.

Effect of treadmill exercise on Purkinje cell loss and astrocytic reaction in the cerebellum after traumatic brain injury

The cerebellum is one of the brain areas, which is selectively vulnerable to forebrain traumatic brain injuries (TBI). Physical exercise in animals is known to promote cell survival and functional recovery after brain injuries. However, the detailed pathologic and functional alterations by exercise following an indirect cerebellar injury induced by a TBI are largely unknown. We determined the effects of treadmill exercise on survival of Purkinje neurons and on a population of reactive astrocytes in the gyrus of lobules VIII and IX of the cerebellum after TBI. The rats were divided into four groups: the sham-operation group, the sham-operation with exercise group, the TBI-induction group, and the TBI-induction with exercise group. Cell biological changes of Purkinje neurons following indirect cerebellar injury were analyzed by immunohistochemistry. TBI-induced loss of calbindin-stained Purkinje neurons in the posterior region of the cerebellum and TBI also increased formation of reactive astroyctes in both the granular and molecular layers of the cerebellar posterior region. Treadmill exercise for 10 days after TBI increased the number of calbindin-stained Purkinje neurons and suppressed formation of reactive astroyctes. The present study provides the possibility that treadmill exercise may be an important mediator to enhance survival of Purkinje neurons in TBI-induced indirect cerebellar injury.

Proteolysis of submembrane cytoskeletal proteins ankyrin-G and αII-spectrin following diffuse brain injury: a role in white matter vulnerability at Nodes of Ranvier

A high membrane-to-cytoplasm ratio makes axons particularly vulnerable to traumatic injury. Posttraumatic shifts in ionic homeostasis promote spectrin cleavage, disrupt ankyrin linkages and destabilize axolemmal proteins. This study contrasted ankyrin-G and αII-spectrin degradation in cortex and corpus callosum following diffuse axonal injury produced by fluid percussion insult. Ankyrin-G lysis occurred preferentially in white matter, with acute elevation of all fragments and long-term reduction of a low kD form. Calpain-generated αII-spectrin fragments increased in both regions. Caspase-3 lysis of αII-spectrin showed a small, acute rise in cortex but was absent in callosum. White matter displayed nodal damage, with horseradish peroxidase permeability into the submyelin space. Ankyrin-G-binding protein neurofascin and spectrin-binding protein ankyrin-B showed acute alterations in expression. These results support ankyrin-G vulnerability in white matter following trauma and suggest that ankyrin-G and αII-spectrin proteolysis disrupts Node of Ranvier integrity. The time course of such changes were comparable to previously observed functional deficits in callosal fibers.

A novel decalcification method for adult rodent bone for histological analysis of peripheral-central nervous system connections

Histological analysis of bone encased tissue is severely hampered by technical difficulties associated with sectioning calcified tissue. Cryosectioning of bone is possible but requires significant technical adaptation and expensive materials and is often time-consuming. Some decalcifying reagents in common use result in successful cryosectioning in less time but the integrity of the soft tissue of the spinal column is often compromised during processing. This can result in significant loss of cellular detail. In order to find a method that would allow cryosectioning of the bone without loss of structural integrity of the underlying soft tissue we assessed the efficacy of four different decalcifying reagents with respect to their effects on the cellular structure of the myelin of the grey and white matter of the spinal cord. The antigenic integrity of the spinal cord white matter was evaluated using tissue structural integrity and quality of myelin basic protein immunostaining. The result of this research shows that 6% TCA not only decalcifies intact spinal column suitably for cryosectioning but does so without compromising the antigenic integrity of the tissue. The ease of application, speed of processing and a favorable cost-effective profile were secondary benefits noted with the use of the 6% TCA decalcifying solution. The ability to utilize a decalcifying solution that allows for both histomorphometry and immunohistochemistry in the same spinal column segment represents a novel technique that will provide new insights into pathophysiological aspects and therapeutic approaches ispinal cord damage or disease.