Experimental Models Of Traumatic Brain Injury Research Articles

Age-dependent alterations in cAMP signaling contribute to synaptic plasticity deficits following traumatic brain injury

The elderly have comparatively worse cognitive impairments from traumatic brain injury (TBI) relative to younger adults, but the molecular mechanisms that underlie this exacerbation of cognitive deficits are unknown. Experimental models of TBI have demonstrated that the cyclic AMP-protein kinase A (cAMP-PKA) signaling pathway is downregulated after brain trauma. Since the cAMP-PKA signaling pathway is a key mediator of long-term memory formation, we investigated whether the TBI-induced decrease in cAMP levels is exacerbated in aged animals. Aged (19months) and young adult (3months) male Fischer 344 rats received sham surgery or mild (1.4–1.6 atmospheres, atm) or moderate (1.7–2.1atm) parasagittal fluid-percussion brain injury. At various time points after surgery, the ipsilateral parietal cortex, hippocampus, and thalamus were assayed for cAMP levels. Mild TBI lowered cAMP levels in the hippocampus of aged, but not young adult animals. Moderate TBI lowered cAMP levels in the hippocampus and parietal cortex of both age groups. In the thalamus, cAMP levels were significantly lowered after moderate, but not mild TBI. To determine if the TBI-induced decreases in cAMP had physiological consequences in aged animals, hippocampal long-term potentiation (LTP) in the Schaffer collateral pathway of the CA1 region was assessed. LTP was significantly decreased in both young adult and aged animals after mild and moderate TBI as compared to sham surgery animals. Rolipram rescued the LTP deficits after mild TBI for young adult animals and caused a partial recovery for aged animals. However, rolipram did not rescue LTP deficits after moderate TBI in either young adult or aged animals. These results indicate that the exacerbation of cognitive impairments in aged animals with TBI may be due to decreased cAMP levels and deficits in hippocampal LTP.

Transplantation of mesenchymal stem cells to the brain by topical application in an experimental traumatic brain injury model

Mesenchymal stem cells (MSCs) have been shown in various animal models to be capable of neurorepair and neuroprotection. To carry out a therapeutic function, MSCs must be delivered to the target organ. MSCs are administered to patients via systemic infusion, which has many drawbacks, including a low engraftment rate and the migration of MSCs to non-target organs. However, other approaches such as direct intracerebral injection of MSCs might cause cerebral bleeding. In this study, a traumatic brain injury (TBI) was induced over the right parietal cerebral cortex in Sprague Dawley rats, and green fluorescent protein (GFP)-expressing MSCs (GFP-MSCs), together with a thin layer of fibrin, were applied to the external surface of the contralateral side 2days later. Within 5days of topical application, the GFP-MSCs had migrated from the site of application on the cortical surface, through the white matter, and had emerged at the cortical surface of the TBI site on the contralateral cerebral hemisphere, apparently following axons along the corpus callosum. In sham-injured control animals, the topically applied GFP-MSCs proliferated superficially on the cortex at the site of application, and no GFP-MSCs were found at the contralateral cortical surface. In all instances, GFP-MSCs were not detected in other organs of either the test or the control animals. Our study demonstrated that MSCs topically applied to the brain surface can migrate to a TBI site.

Morris water maze function and histologic characterization of two age-at-injury experimental models of controlled cortical impact in the immature rat

Controlled cortical impact (CCI) is commonly used in adult animals to study focal traumatic brain injury (TBI). Our study aims to further study injury mechanisms in children and variable models of pathology in the developing brain. Develop a focal injury model of experimental TBI in the immature, postnatal days (PND) 7 and 17 rats that underwent a CCI at varying depths of deflection, 1.5-2.5mm compared with sham and then tested using the Morris water maze (MWM) beginning on post-injury day (PID) 11. Histopathologic analysis was performed at PID 1 and 28. In PND 7, the 1.75- and 2.0-mm deflections (diameter (d) = 3mm; velocity = 4m/s; and duration = 500ms) resulted in significant MWM deficits while the 1.5-mm injury did not produce MWM deficits vs. sham controls. In PND 17, all injury levels resulted in significant MWM deficits vs. sham controls with a graded response; the 1.5-mm deflection (d = 6mm; velocity = 4m/s; and duration = 500ms) produced significantly less deficits as compared WITH the 2.0- and 2.5-mm injuries. Histologically, a graded injury response was also seen in both ages at injury with cortical and more severe injuries, hippocampal damage. Cortical contusion volume increased in most injury severities from PID 1 to 28 in both ages at injury while hippocampal volumes subsequently decreased. CCI in PND 7 and 17 rat results in significant MWM deficits and cortical histopathology providing two different and unique experimental models of TBI in immature rats that may be useful in further investigations into the mechanisms and treatments of pediatric TBI.

Administration of palmitoylethanolamide (PEA) protects the neurovascular unit and reduces secondary injury after traumatic brain injury in mice

Traumatic brain injury (TBI) is a major cause of preventable death and morbidity in young adults. This complex condition is characterized by significant blood brain barrier leakage that stems from cerebral ischemia, inflammation, and redox imbalances in the traumatic penumbra of the injured brain. Recovery of function after TBI is partly through neuronal plasticity. In order to test whether treatments that enhance plasticity might improve functional recovery, a controlled cortical impact (CCI) in adult mice, as a model of TBI, in which a controlled cortical impactor produced full thickness lesions of the forelimb region of the sensorimotor cortex, was performed. Once trauma has occurred, combating these exacerbations is the keystone of an effective TBI therapy. The endogenous fatty acid palmitoylethanolamide (PEA) is one of the members of N-acyl-ethanolamines family that maintain not only redox balance but also inhibit the mechanisms of secondary injury. Therefore, we tested whether PEA shows efficacy in a mice model of experimental TBI. PEA treatment is able to reduced edema and brain infractions as evidenced by decreased 2,3,5-triphenyltetrazolium chloride staining across brain sections. PEA-mediated improvements in tissues histology shown by reduction of lesion size and improvement in apoptosis level further support the efficacy of PEA therapy. The PEA treatment blocked infiltration of astrocytes and restored CCI-mediated reduced expression of PAR, nitrotyrosine, iNOS, chymase, tryptase, CD11b and GFAP. PEA inhibited the TBI-mediated decrease in the expression of pJNK and NF-κB. PEA-treated injured animals improved neurobehavioral functions as evaluated by behavioral tests.

Controlled Cortical Impact Traumatic Brain Injury Acutely Disrupts Wakefulness and Extracellular Orexin Dynamics as Determined by Intracerebral Microdialysis in Mice

Among other deficits, traumatic brain injury (TBI) causes impaired arousal and cognitive dysfunction. Hypothalamic orexin neuropeptides (also called hypocretins) regulate levels of arousal, and cerebrospinal fluid orexin levels are reportedly low in TBI patients. We hypothesized that TBI acutely impairs the dynamics of orexin release into brain interstitial fluid, and that these extracellular orexin levels correlate with wakefulness and motor activity. To test this in mice, we combined an electromagnetic controlled cortical impact (CCI) model of experimental TBI with dual intracerebral microdialysis using one catheter in the hypothalamus and one catheter in the hippocampus, plus electroencephalography/electromyography (EEG/EMG), and motor activity monitoring. Baseline data were continuously collected in tethered but relatively freely moving mice for 2 days. Then, ipsilateral CCI or sham surgery was performed, and data collection was continued for 3 additional days. At baseline, extracellular orexin levels in the hypothalamus showed a circadian rhythm, with peak levels during the dark (wake) phase, and a nadir during the light (rest) phase. Following CCI but not sham surgery, orexin levels were depressed in both the hypothalamus and hippocampus, and diurnal fluctuation amplitudes were blunted in the hypothalamus. At baseline, correlations of orexin with wakefulness and motor activity were positive and highly significant. Following CCI but not sham surgery, the mice exhibited reduced wakefulness and motor activity, and correlations between orexin and these measures were diminished. These abnormal orexin dynamics were associated with hypothalamic astrogliosis, but not acute loss of orexin neurons, as assessed by immunohistochemistry 3 days after injury. Future studies involving experimental manipulations of the orexin system will be required to determine its contribution to neurological outcomes following injury.

Ghrelin Prevents TBI‐induced Neuronal Apoptosis via Induction of Mitochondrial Uncoupling Protein 2 (UCP2)

Traumatic brain injury (TBI) is a significant cause of morbidity and mortality in humans. Presently, no pharmacologic agent exists to prevent neuronal loss; however, the second wave of cellular death that follows TBI occurs within a timeframe amenable to therapeutic intervention. Previous research has demonstrated that transient mitochondrial uncoupling may help prevent initiation of apoptosis via the intrinsic pathway. Among the several endogenous mitochondrial uncoupling proteins identified, UCP2 has been shown to be expressed throughout the central nervous system and to provide a protective role in a variety of neural injury models. Moreover, production of UCP2 is upregulated when levels of ghrelin, a protein with anti‐inflammatory and anti‐apoptotic properties, are elevated. Our study sought to correlate these two observations in an experimental model of TBI. We hypothesized that ghrelin administration would inhibit neuronal apoptosis via induction of UCP2. BALB/c mice were divided into sham, TBI, and TBI/ghrelin treatment groups, and TBI was induced with a weight drop model following anesthesia. Neuronal apoptosis was characterized by staining coronal brain sections with the TUNEL method, and relative expression levels of UCP2 and the apoptotic protein caspase‐3 were analyzed with immunohistochemistry. We found that increased UCP2 expression in response to TBI/ghrelin treatment correlated with decreased neuronal apoptosis, suggesting that ghrelin treatment may provide an amenable therapeutic target for reducing neurodegeneration following TBI.

Mannose binding lectin deficiency attenuates neurobehavioral deficits following experimental traumatic brain injury

Mannose binding lectin (MBL) is the activator of the lectin complement pathway. After cerebral ischemia it has been shown that MBL could be a mediator of secondary brain damage, in contrast after traumatic brain injury (TBI) there are data suggesting that it could be linked to neuroprotection. We tested the hypothesis that MBL is involved in the pathophysiology of TBI. We characterized (1) the temporal activation of MBL and (2) the effects of its inhibition in a model of experimental TBI.

Immediate, but not delayed, microsurgical skull reconstruction exacerbates brain damage in experimental traumatic brain injury model.

Moderate to severe traumatic brain injury (TBI) often results in malformations to the skull. Aesthetic surgical maneuvers may offer normalized skull structure, but inconsistent surgical closure of the skull area accompanies TBI. We examined whether wound closure by replacement of skull flap and bone wax would allow aesthetic reconstruction of the TBI-induced skull damage without causing any detrimental effects to the cortical tissue. Adult male Sprague-Dawley rats were subjected to TBI using the controlled cortical impact (CCI) injury model. Immediately after the TBI surgery, animals were randomly assigned to skull flap replacement with or without bone wax or no bone reconstruction, then were euthanized at five days post-TBI for pathological analyses. The skull reconstruction provided normalized gross bone architecture, but 2,3,5-triphenyltetrazolium chloride and hematoxylin and eosin staining results revealed larger cortical damage in these animals compared to those that underwent no surgical maneuver at all. Brain swelling accompanied TBI, especially the severe model, that could have relieved the intracranial pressure in those animals with no skull reconstruction. In contrast, the immediate skull reconstruction produced an upregulation of the edema marker aquaporin-4 staining, which likely prevented the therapeutic benefits of brain swelling and resulted in larger cortical infarcts. Interestingly, TBI animals introduced to a delay in skull reconstruction (i.e., 2 days post-TBI) showed significantly reduced edema and infarcts compared to those exposed to immediate skull reconstruction. That immediate, but not delayed, skull reconstruction may exacerbate TBI-induced cortical tissue damage warrants a careful consideration of aesthetic repair of the skull in TBI.

Traumatic Brain Injury during Warfarin Anticoagulation: An Experimental Study in Mice

The number of patients who are on long-term anticoagulation therapy while experiencing traumatic brain injury (TBI) is rising. This experimental study evaluated whether warfarin pre-treatment increases brain hemorrhage and worsens functional outcome after TBI, and whether the rapid reversal of anticoagulation after TBI prevents warfarin-exacerbated brain damage. Normal CD-1 mice (C) and mice pre-treated with warfarin (W) to an International Normalized Ratio of 3.5±0.9 underwent TBI using a controlled cortical impact model. Mean hemorrhage volume 24 h after TBI was 1.2±0.4 μL in C mice and 10.9±6.9 μL in W mice (p=0.029, n=4 per group). In a second study, anticoagulated mice received either saline (W-S) or prothrombin complex concentrate (W-PCC, 100 U/kg) intravenously 60 min after TBI. Anticoagulation reversal using PCC (W-PCC mice) reduced hemorrhage volumes as compared to W-S animals (7.3±6.0 versus 19.8±14.0 μL, p=0.045, n=8 per group). In a third study, we examined motor deficits and lesion volume in C, W-S, and W-PCC mice until 33 days after injury. Functional outcome and lesion volume were no different between groups (n=10 per group). In conclusion, we characterized an experimental model of TBI occurring during warfarin anticoagulation. Anticoagulation led to higher intracerebral blood volumes, but did not significantly worsen functional outcome. The rapid reversal of anticoagulation may be effective in preventing excess bleeding.

The Role of Free Radicals in Traumatic Brain Injury

Traumatic brain injury (TBI) is a significant cause of death and disability in both the civilian and the military populations. The primary impact causes initial tissue damage, which initiates biochemical cascades, known as secondary injury, that expand the damage. Free radicals are implicated as major contributors to the secondary injury. Our review of recent rodent and human research reveals the prominent role of the free radicals superoxide anion, nitric oxide, and peroxynitrite in secondary brain injury. Much of our current knowledge is based on rodent studies, and the authors identified a gap in the translation of findings from rodent to human TBI. Rodent models are an effective method for elucidating specific mechanisms of free radical-induced injury at the cellular level in a well-controlled environment. However, human TBI does not occur in a vacuum, and variables controlled in the laboratory may affect the injury progression. Additionally, multiple experimental TBI models are accepted in rodent research, and no one model fully reproduces the heterogeneous injury seen in humans. Free radical levels are measured indirectly in human studies based on assumptions from the findings from rodent studies that use direct free radical measurements. Further study in humans should be directed toward large samples to validate the findings in rodent studies. Data obtained from these studies may lead to more targeted treatment to interrupt the secondary injury cascades.

Development of Post-Traumatic Epilepsy after Controlled Cortical Impact and Lateral Fluid-Percussion-Induced Brain Injury in the Mouse

The present study investigated the development of hyperexcitability and epilepsy in mice with traumatic brain injury (TBI) induced by controlled cortical impact (CCI) or lateral fluid-percussion injury (FPI), which are the two most commonly used experimental models of human TBI in rodents. TBI was induced with CCI to 50 (14 controls) and with lateral FPI to 45 (15 controls) C57BL/6S adult male mice. The animals were followed-up for 9 months, including three 2-week periods of continuous video-electroencephalographic (EEG) monitoring, and a seizure susceptibility test with pentylenetetrazol (PTZ). In the end, the animals were perfusion-fixed for histology. The experiment included two independent cohorts of animals. Late post-traumatic spontaneous electrographic seizures were detected in 9% of mice after CCI and 3% after lateral FPI. Eighty-two percent of mice after CCI and 71% after lateral FPI had spontaneous epileptiform spiking on EEG. In addition, 58% of mice with lateral FPI showed spontaneous epileptiform discharges. A PTZ test demonstrated increased seizure susceptibility in the majority of mice in both models, compared to control mice. There was no further progression in the occurrence of epilepsy or epileptiform spiking when follow-up was extended from 6 to 9 months. The severity of cortical or hippocampal damage did not differentiate mice with or without epileptiform activity in either model. Finally, two independent series of experiments in both injury models provided comparable data demonstrating reproducibility of the modeling. These data show that different types of impact can trigger epileptogenesis in mice. Even though the frequency of spontaneous seizures in C57BL/6S mice is low, a large majority of animals develop hyperexcitability.

Effect of Recombinant Human Erythropoietin on Survivin Expression in Brain Tissues after Traumatic Brain Injury in Rats

Objective: To explore the regulative effect on Survivin of r-HuEPO after traumatic brain injury (TBI) in rats, and understand the neuroprotection mechanisms of r-HuEPO. Methods: Seventy-eight adult Wistar rats were randomly divided into sham operation group (n = 6), TBI group (n = 36) and r-HuEPO group (n = 36). The experimental TBI model was created by Feeney’s method. Samples were obtained after injury for measuring apoptosis of cells by Epics XL Flow Cytometer. Immunochemical method was performed for inspection of expressions of Survivin and NF-κB proteins. Results: Compared to the sham group, the number of apoptotic cells and Survivin, NF-κB immunopositive cells was significantly increased in the injured brain after TBI (P < 0.01). R-HuEPO significantly increased the expression of survivin and NF-κB, but decreased the apoptotic rates. Conclusion: Increased expression of NF-κB by r-HuEPO may play important role in regulating Survivin level, inhibiting neuronal apoptosis in cortex and exerting protective function to neurons.

Chapter 15. Analgesics, sedatives, and neuromuscular blockade

Chapter 15. Analgesics, sedatives, and neuromuscular blockade

Lateral Fluid Percussion: Model of Traumatic Brain Injury in Mice

Traumatic brain injury (TBI) research has attained renewed momentum due to the increasing awareness of head injuries, which result in morbidity and mortality. Based on the nature of primary injury following TBI, complex and heterogeneous secondary consequences result, which are followed by regenerative processes 1,2. Primary injury can be induced by a direct contusion to the brain from skull fracture or from shearing and stretching of tissue causing displacement of brain due to movement 3,4. The resulting hematomas and lacerations cause a vascular response 3,5, and the morphological and functional damage of the white matter leads to diffuse axonal injury 6-8. Additional secondary changes commonly seen in the brain are edema and increased intracranial pressure 9. Following TBI there are microscopic alterations in biochemical and physiological pathways involving the release of excitotoxic neurotransmitters, immune mediators and oxygen radicals 10-12, which ultimately result in long-term neurological disabilities 13,14. Thus choosing appropriate animal models of TBI that present similar cellular and molecular events in human and rodent TBI is critical for studying the mechanisms underlying injury and repair.Various experimental models of TBI have been developed to reproduce aspects of TBI observed in humans, among them three specific models are widely adapted for rodents: fluid percussion, cortical impact and weight drop/impact acceleration 1. The fluid percussion device produces an injury through a craniectomy by applying a brief fluid pressure pulse on to the intact dura. The pulse is created by a pendulum striking the piston of a reservoir of fluid. The percussion produces brief displacement and deformation of neural tissue 1,15. Conversely, cortical impact injury delivers mechanical energy to the intact dura via a rigid impactor under pneumatic pressure 16,17. The weight drop/impact model is characterized by the fall of a rod with a specific mass on the closed skull 18. Among the TBI models, LFP is the most established and commonly used model to evaluate mixed focal and diffuse brain injury 19. It is reproducible and is standardized to allow for the manipulation of injury parameters. LFP recapitulates injuries observed in humans, thus rendering it clinically relevant, and allows for exploration of novel therapeutics for clinical translation 20.We describe the detailed protocol to perform LFP procedure in mice. The injury inflicted is mild to moderate, with brain regions such as cortex, hippocampus and corpus callosum being most vulnerable. Hippocampal and motor learning tasks are explored following LFP.

Lateral Fluid Percussion: Model of Traumatic Brain Injury in Mice

Traumatic brain injury (TBI) research has attained renewed momentum due to the increasing awareness of head injuries, which result in morbidity and mortality. Based on the nature of primary injury following TBI, complex and heterogeneous secondary consequences result, which are followed by regenerative processes 1,2. Primary injury can be induced by a direct contusion to the brain from skull fracture or from shearing and stretching of tissue causing displacement of brain due to movement 3,4. The resulting hematomas and lacerations cause a vascular response 3,5, and the morphological and functional damage of the white matter leads to diffuse axonal injury 6-8. Additional secondary changes commonly seen in the brain are edema and increased intracranial pressure 9. Following TBI there are microscopic alterations in biochemical and physiological pathways involving the release of excitotoxic neurotransmitters, immune mediators and oxygen radicals 10-12, which ultimately result in long-term neurological disabilities 13,14. Thus choosing appropriate animal models of TBI that present similar cellular and molecular events in human and rodent TBI is critical for studying the mechanisms underlying injury and repair. Various experimental models of TBI have been developed to reproduce aspects of TBI observed in humans, among them three specific models are widely adapted for rodents: fluid percussion, cortical impact and weight drop/impact acceleration 1. The fluid percussion device produces an injury through a craniectomy by applying a brief fluid pressure pulse on to the intact dura. The pulse is created by a pendulum striking the piston of a reservoir of fluid. The percussion produces brief displacement and deformation of neural tissue 1,15. Conversely, cortical impact injury delivers mechanical energy to the intact dura via a rigid impactor under pneumatic pressure 16,17. The weight drop/impact model is characterized by the fall of a rod with a specific mass on the closed skull 18. Among the TBI models, LFP is the most established and commonly used model to evaluate mixed focal and diffuse brain injury 19. It is reproducible and is standardized to allow for the manipulation of injury parameters. LFP recapitulates injuries observed in humans, thus rendering it clinically relevant, and allows for exploration of novel therapeutics for clinical translation 20. We describe the detailed protocol to perform LFP procedure in mice. The injury inflicted is mild to moderate, with brain regions such as cortex, hippocampus and corpus callosum being most vulnerable. Hippocampal and motor learning tasks are explored following LFP.

Effect of Coenzyme Q10 on ischemia and neuronal damage in an experimental traumatic brain-injury model in rats

BackgroundHead trauma is one of the most important clinical issues that not only can be fatal and disabling, requiring long-term treatment and care, but also can cause heavy financial burden. Formation or distribution of free oxygen radicals should be decreased to enable fixing of poor neurological outcomes and to prevent neuronal damage secondary to ischemia after trauma. Coenzyme Q10 (CoQ10), a component of the mitochondrial electron transport chain, is a strong antioxidant that plays a role in membrane stabilization. In this study, the role of CoQ10 in the treatment of head trauma is researched by analyzing the histopathological and biochemical effects of CoQ10 administered after experimental traumatic brain injury in rats. A traumatic brain-injury model was created in all rats. Trauma was inflicted on rats by the free fall of an object of 450 g weight from a height of 70 cm on the frontoparietal midline onto a metal disc fixed between the coronal and the lambdoid sutures after a midline incision was carried out.ResultsIn the biochemical tests, tissue malondialdehyde (MDA) levels were significantly higher in the traumatic brain-injury group compared to the sham group (p < 0.05). Administration of CoQ10 after trauma was shown to be protective because it significantly lowered the increased MDA levels (p < 0.05). Comparing the superoxide dismutase (SOD) levels of the four groups, trauma + CoQ10 group had SOD levels ranging between those of sham group and traumatic brain-injury group, and no statistically significant increase was detected. Histopathological results showed a statistically significant difference between the CoQ10 and the other trauma-subjected groups with reference to vascular congestion, neuronal loss, nuclear pyknosis, nuclear hyperchromasia, cytoplasmic eosinophilia, and axonal edema (p < 0.05).ConclusionNeuronal degenerative findings and the secondary brain damage and ischemia caused by oxidative stress are decreased by CoQ10 use in rats with traumatic brain injury.

Repetitive Closed-Skull Traumatic Brain Injury in Mice Causes Persistent Multifocal Axonal Injury and Microglial Reactivity

Repetitive mild or "concussive" traumatic brain injury (TBI) can cause substantial neurologic impairment, but the pathological features of this type of injury are not fully understood. We report an experimental model of TBI in which the closed skulls of anesthetized male C57BL/6J mice are struck with an electromagnetically controlled rubber impactor twice with an interval of 24 hours between impacts. The mice had deficits in Morris water maze performance in the first week after injury that only partially resolved 7 weeks later. By routine histology, there was no apparent bleeding, neuronal cell loss, or tissue disruption, and amyloid precursor protein immunohistochemistry demonstrated very few immunoreactive axonal varicosities. In contrast, silver staining revealed extensive abnormalities in the corpus callosum and bilateral external capsule, the ipsilateral cortex and thalamus, and the contralateral hippocampal CA1 stratum radiatum and stratum oriens. Electron microscopy of white matter regions demonstrated axonal cytoskeletal disruption, intra-axonal organelle compaction, and irregularities in axon caliber. Reactive microglia were observed in the same areas as the injured axons by both electron microscopy and Iba1 immunohistochemistry. Quantitative analyses of silver staining and Iba1 immunohistochemistry at multiple time points demonstrated transient cortical and thalamic abnormalities but persistent white matter pathology as late as 7 weeks after injury.Thus, prominent and long-lasting abnormalities in this TBI model were underestimated using conventional approaches. The model may be useful for mechanistic investigations and preclinical assessment of candidate therapeutics.

Preclinical efficacy testing in middle-aged rats: nicotinamide, a novel neuroprotectant, demonstrates diminished preclinical efficacy after controlled cortical impact.

Age is a consistent predictor of poor outcome following traumatic brain injury (TBI). Although the elderly population has one of the highest rates of TBI-related hospitalization and death, few preclinical studies have attempted to model and treat TBI in the aged population. Recent studies have indicated that nicotinamide (NAM), a soluble B-group vitamin, improved functional recovery in experimental models of TBI in young animals. The purpose of the present study was to examine the preclinical efficacy of NAM in middle-aged rats. Groups of middle-aged (14-month-old) rats were assigned to NAM (500 mg/kg or 50 mg/kg) or saline alone (1 mL/kg) treatment conditions, and received unilateral cortical contusion injuries (CCI) and injections at 1 h and 24 h following injury. The animals were tested on a variety of tasks to assess vestibulomotor (tapered beam) and cognitive performance (reference and working memory in the Morris water maze), and were evaluated for lesion size, blood-brain barrier compromise, astrocytic activation, and edema formation. In summary, the preclinical efficacy of NAM as a treatment following CCI in middle-aged rats differs from that previously documented in younger rats; while treatment with 50 mg/kg NAM appeared to have no effect, the 500-mg/kg dose worsened performance in middle-aged animals. Histological indicators demonstrated more nuanced group differences, indicating that NAM may positively impact some of the cellular cascades following injury, but were not substantial enough to improve functional recovery. These findings emphasize the need to examine potential treatments for TBI utilizing non-standard populations, and may explain why so many treatments have failed in clinical trials.

Pharyngeal Selective Brain Cooling Is Associated with Reduced CNS Cortical Lesion after Experimental Traumatic Brain Injury in Rats

Therapeutic hypothermia (TH) is still being explored as a therapeutic option after traumatic brain injury (TBI) but clinical data has not supported its efficacy. Experimental approaches were promising, but clinical data did not support its efficacy in the treatment of TBI. A novel approach of pharyngeal selective brain cooling (pSBC), recently introduced by our group, has been accompanied by superior neurofunctional, sensorimotor, and cognitive outcomes. This work is now extended by data on histomorphological and physical outcomes after pSBC in a model of experimental TBI. Male Sprague-Dawley rats were subjected to lateral fluid-percussion (LFP) brain injury, and randomized to the following experimental groups: (1) TBI with pSBC, (2) TBI without pSBC, and (3) sham animals. On day post-injury (DPI) 14, the animals were sacrificed and their brains were harvested for immunohistochemistry using the following antibodies: (1) glial fibrillary acidic protein (GFAP), (2) neurofilament (NF), and (3) synaptophysin (SY). In pSBC animals brain temperature was selectively lowered to 33 ± 0.5°C within 15 min post-injury, and maintained for 180 min after induction, while keeping rectal temperatures at physiological levels. Animals that had undergone pSBC showed a significantly faster recovery of body weight starting on DPI 3, and had gained substantially more weight than TBI-only animals on DPI 14 (p < 0.001), indicating superior physical recovery. Areas of cortical damage were significantly smaller in pSBC animals compared to TBI-only animals (p < 0.01). pSBC was associated with preservation of cortical tissue ipsilateral to the lesion, and superior physical recovery after experimental TBI. These results complement earlier reports in which pSBC was associated with superior neurofunctional and cognitive outcomes using the same experimental model.

Effects of Traumatic Brain Injury of Different Severities on Emotional, Cognitive, and Oxidative Stress-Related Parameters in Mice

Cognitive deficits and psychiatric disorders are significant sequelae of traumatic brain injury (TBI). Animal models have been widely employed in TBI research, but few studies have addressed the effects of experimental TBI of different severities on emotional and cognitive parameters. In this study, mice were subjected to weight-drop TBI to induce mild, intermediate, or severe TBI. After neurological assessment, the mice recovered for 10 days, and were then subjected to a battery of behavioral tests, which included open-field, elevated plus-maze, forced swimming, tail suspension, and step-down inhibitory avoidance tests. Oxidative stress-related parameters (nonprotein thiols [NPSH], glutathione peroxidase [GPx], glutathione reductase [GR], and thiobarbituric acid reactive species [TBARS]) were quantified in the cortex and hippocampus at 2 and 24 h and 14 days after TBI, and histopathological analysis was performed 15 days after TBI. Mice subjected to mild TBI showed increased anxiety and depressive-like behaviors, while intermediate and severe TBI induced robust memory deficits. The severe TBI group also displayed increased locomotor activity. Intermediate and severe TBI caused extensive macroscopic and microscopic brain damage, while mild TBI typically had no histological abnormalities. Moreover, a significant increase in TBARS in the ipsilateral cortex and GPx in the ipsilateral hippocampus was observed at 24 h and 14 days, respectively, following intermediate TBI. The current experimental TBI model induced emotional and cognitive changes comparable to sequelae seen in human TBI, and it might therefore represent a useful approach to the study of mechanisms of and new treatments for TBI and related disorders.