Evaluation of a novel calcium channel blocker, (S)-emopamil, on regional cerebral edema and neurobehavioral function after experimental brain injury

Mild Traumatic Brain Injury Impairs Fear Extinction and Network Excitability in the Infralimbic Cortex

Traumatic brain injury (TBI) is a leading cause of morbidity and disability, with mild TBI (concussions) representing over 80% of cases. Although often considered benign, mild TBI is associated with persistent neuropsychiatric conditions, including post-traumatic stress disorder, anxiety, and depression. A hallmark of these conditions is impaired fear extinction (FE), the process by which learned fear responses are inhibited in safe contexts. This dysfunction contributes to maladaptive fear expression and is linked to altered neurocircuitry, particularly in the infralimbic cortex (IL), a key region in FE. Despite extensive evidence of impaired FE in patients with mild TBI and animal models, the specific mechanisms underlying this deficit remain poorly understood. This study aimed to address this gap by combining cued-FE behavior, local field potential recordings, and whole-cell patch-clamp techniques to investigate how mild TBI affects IL network activity and excitability in a mouse model of TBI. Our results demonstrate that mild lateral fluid percussion injury significantly impairs FE memory, as evidenced by an elevated cued-fear response during extinction testing 10 days post-injury. Field potential recordings revealed decreased activation of the IL network in both layers II/III and V, which was consistent with the observed behavioral deficits. Further analysis of synaptic physiology revealed an imbalance in excitatory and inhibitory neurotransmission (E/I imbalance) in the IL, characterized by reduced excitatory input and enhanced inhibitory input to neurons in both layers. Moreover, intrinsic excitability was altered in IL neurons after mild TBI. This study provides novel insights into how mild TBI disrupts the neurocircuitry underlying FE, specifically by suppressing IL excitability. These results highlight the importance of understanding the mechanistic disruptions in IL activity for developing therapeutic strategies to address fear-based disorders in patients with mild TBI.

Temporal expression of brainstem neurotrophic proteins following mild traumatic brain injury

BDNF, a neurotrophic factor, and its receptors have been implicated in the pathophysiology of mild traumatic brain injury (mTBI). The brainstem houses many vital functions, that are also associated with signs and symptoms of mTBI, but has been understudied in mTBI animal models. We determined the extent to which neurotrophic protein and associated receptor expression is affected within the brainstem of adult rats following mTBI. Their behavioral function was assessed and temporal expression of the 'negative' regulators of neuronal function (p75, t-TrkB, and pro-BDNF) and 'positive' neuroprotective (FL-TrkB and m-BDNF) protein isoforms were determined via western blot and immunohistochemistry at 1, 3, 7, and 14 post-injury days (PID) following mTBI or sham (control) procedure. Within the brainstem, p75 expression increased at PID 1 vs. sham animals. t-TrkB and pro-BDNF expression increased at PID 7 and 14. The 'positive' protein isoforms of FL-TrkB and m-BDNF expression were increased only at PID 7. The ratio of t-TrkB:FL-TrkB (negative:positive) was substantial across groups and time points, suggesting a negative impact of neurotrophic signaling on neuronal function. Additional NeuN experiments revealed cell death occurring within a subset of neurons within the medulla. While behavioral measures improved by PID 7-14, negative neurotrophic biochemical responses persisted. Despite the assertion that mTBI produces "mild" injury, evidence of cell death was observed in the medulla. Ratios of TrkB and BDNF isoforms with conflicting functions suggest that future work should specifically measure each subtype since they induce opposing downstream effects on neuronal function.

Traumatic Brain Injuries: Pathophysiology and Potential Therapeutic Targets

Traumatic brain injury (TBI) remains one of the leading causes of morbidity and mortality amongst civilians and military personnel globally. Despite advances in our knowledge of the complex pathophysiology of TBI, the underlying mechanisms are yet to be fully elucidated. While initial brain insult involves acute and irreversible primary damage to the parenchyma, the ensuing secondary brain injuries often progress slowly over months to years, hence providing a window for therapeutic interventions. To date, hallmark events during delayed secondary CNS damage include Wallerian degeneration of axons, mitochondrial dysfunction, excitotoxicity, oxidative stress and apoptotic cell death of neurons and glia. Extensive research has been directed to the identification of druggable targets associated with these processes. Furthermore, tremendous effort has been put forth to improve the bioavailability of therapeutics to CNS by devising strategies for efficient, specific and controlled delivery of bioactive agents to cellular targets. Here, we give an overview of the pathophysiology of TBI and the underlying molecular mechanisms, followed by an update on novel therapeutic targets and agents. Recent development of various approaches of drug delivery to the CNS is also discussed.

In Vitro and In Vivo Pipeline for Validation of Disease-Modifying Effects of Systems Biology-Derived Network Treatments for Traumatic Brain Injury-Lessons Learned

We developed a pipeline for the discovery of transcriptomics-derived disease-modifying therapies and used it to validate treatments in vitro and in vivo that could be repurposed for TBI treatment. Desmethylclomipramine, ionomycin, sirolimus and trimipramine, identified by in silico LINCS analysis as candidate treatments modulating the TBI-induced transcriptomics networks, were tested in neuron-BV2 microglial co-cultures, using tumour necrosis factor α as a monitoring biomarker for neuroinflammation, nitrite for nitric oxide-mediated neurotoxicity and microtubule associated protein 2-based immunostaining for neuronal survival. Based on (a) therapeutic time window in silico, (b) blood-brain barrier penetration and water solubility, (c) anti-inflammatory and neuroprotective effects in vitro (p < 0.05) and (d) target engagement of Nrf2 target genes (p < 0.05), desmethylclomipramine was validated in a lateral fluid-percussion model of TBI in rats. Despite the favourable in silico and in vitro outcomes, in vivo assessment of clomipramine, which metabolizes to desmethylclomipramine, failed to demonstrate favourable effects on motor and memory tests. In fact, clomipramine treatment worsened the composite neuroscore (p < 0.05). Weight loss (p < 0.05) and prolonged upregulation of plasma cytokines (p < 0.05) may have contributed to the worsened somatomotor outcome. Our pipeline provides a rational stepwise procedure for evaluating favourable and unfavourable effects of systems-biology discovered compounds that modulate post-TBI transcriptomics.

Novel Positive Allosteric Modulators of Glutamate Transport Have Neuroprotective Properties in an in Vitro Excitotoxic Model

Dysfunction of excitatory amino acid transporters (EAATs) has been implicated in the pathogenesis of various neurological disorders, such as stroke, brain trauma, epilepsy, and several neurodegenerative disorders. EAAT2 is the main transporter subtype responsible for glutamate clearance in the brain, and plays a key role in regulating neurotransmission and preventing excitotoxicity. Therefore, compounds that increase the activity of EAAT2 have therapeutic potential for neuroprotection. In previous studies, we used virtual screening approaches to identify novel positive allosteric modulators (PAMs) of EAAT2. These compounds were shown to selectively increase the activity of EAAT2 and increase V_max of transport, without changing substrate affinity. In this work, our major effort was to investigate whether increasing the activity of EAAT2 by allosteric modulation would translate to neuroprotection in in vitro primary culture models of excitotoxicity. To investigate potential neuroprotective effects of one EAAT2 PAM, GT949, we subjected cultures to acute and prolonged excitotoxic insults by exogenous application of glutamate, or oxidative stress by application of hydrogen peroxide. GT949 administration did not result in neuroprotection in the oxidative stress model, likely due to damage of the glutamate transporters. However, GT949 displayed neuroprotective properties after acute and prolonged glutamate-mediated excitotoxicity. We propose that this compound prevents excess glutamate signaling by increasing the rate of glutamate clearance by EAAT2, thereby preventing excitotoxic damage and cell death. This novel class of compounds is therefore an innovative approach for neuroprotection with potential for translation in in vivo animal models of excitotoxicity.

Pathophysiology and Treatment of Memory Dysfunction After Traumatic Brain Injury

Memory is fundamental to everyday life, and cognitive impairments resulting from traumatic brain injury (TBI) have devastating effects on TBI survivors. A contributing component to memory impairments caused by TBI is alteration in the neural circuits associated with memory function. In this review, we aim to bring together experimental findings that characterize behavioral memory deficits and the underlying pathophysiology of memory-involved circuits after TBI. While there is little doubt that TBI causes memory and cognitive dysfunction, it is difficult to conclude which memory phase, i.e., encoding, maintenance, or retrieval, is specifically altered by TBI. This is most likely due to variation in behavioral protocols and experimental models. Additionally, we review a selection of experimental treatments that hold translational potential to mitigate memory dysfunction following injury.

REVIEW ■ : Calcium and the Pathogenesis of Traumatic CNS Injury: Cellular and Molecular Mechanisms

Under normal conditions in the central nervous system (CNS), the calcium ion (Ca2+) is known to mediate a variety of neuronal functions, including synaptic neurotransmitter release, neuronal plasticity, protein phos phorylation, and gene expression. Whereas intracellular calcium concentrations ([Ca2+]i) are precisely reg ulated through intracellular buffering, binding, and sequestration, alterations in calcium ion homeostasis and influx of Ca 2+ have been implicated in the pathogenesis of neuronal death and degeneration, as well as cerebral vasospasm associated with multiple types of CNS injury. This review revisits the "calcium hypoth esis" of neuronal death associated with traumatic injury to the CNS and examines both the direct and indirect molecular and cellular evidence for calcium-mediated neuropathology, as well as the potential for novel therapeutic strategies targeted at the downstream intracellular effects of calcium signaling and calcium- activated neutral protease (calpain) activation. NEUROSCIENTIST 3:169-175, 1997

Neuroprotective Effects of the Glutamate Transporter Activator (R)-(-)-5-methyl-1-nicotinoyl-2-pyrazoline (MS-153) following Traumatic Brain Injury in the Adult Rat

Traumatic brain injury (TBI) in humans and in animals leads to an acute and sustained increase in tissue glutamate concentrations within the brain, triggering glutamate-mediated excitotoxicity. Excitatory amino acid transporters (EAATs) are responsible for maintaining extracellular central nervous system glutamate concentrations below neurotoxic levels. Our results demonstrate that as early as 5 min and up to 2 h following brain trauma in brain-injured rats, the activity (Vmax) of EAAT2 in the cortex and the hippocampus was significantly decreased, compared with sham-injured animals. The affinity for glutamate (KM) and the expression of glutamate transporter 1 (GLT-1) and glutamate aspartate transporter (GLAST) were not altered by the injury. Administration of (R)-(-)-5-methyl-1-nicotinoyl-2-pyrazoline (MS-153), a GLT-1 activator, beginning immediately after injury and continuing for 24 h, significantly decreased neurodegeneration, loss of microtubule-associated protein 2 and NeuN (+) immunoreactivities, and attenuated calpain activation in both the cortex and the hippocampus at 24 h after the injury; the reduction in neurodegeneration remained evident up to 14 days post-injury. In synaptosomal uptake assays, MS-153 up-regulated GLT-1 activity in the naïve rat brain but did not reverse the reduced activity of GLT-1 in traumatically-injured brains. This study demonstrates that administration of MS-153 in the acute post-traumatic period provides acute and long-term neuroprotection for TBI and suggests that the neuroprotective effects of MS-153 are related to mechanisms other than GLT-1 activation, such as the inhibition of voltage-gated calcium channels.

Long-Term Effects of Enriched Environment on Neurofunctional Outcome and CNS Lesion Volume After Traumatic Brain Injury in Rats

To determine whether the exposure to long term enriched environment (EE) would result in a continuous improvement of neurological recovery and ameliorate the loss of brain tissue after traumatic brain injury (TBI) vs. standard housing (SH). Male Sprague-Dawley rats (300-350 g, n=28) underwent lateral fluid percussion brain injury or SHAM operation. One TBI group was held under complex EE for 90 days, the other under SH. Neuromotor and sensorimotor dysfunction and recovery were assessed after injury and at days 7, 15, and 90 via Composite Neuroscore (NS), RotaRod test, and Barnes Circular Maze (BCM). Cortical tissue loss was assessed using serial brain sections. After day 7 EE animals showed similar latencies and errors as SHAM in the BCM. SH animals performed notably worse with differences still significant on day 90 (p<0.001). RotaRod test and NS revealed superior results for EE animals after day 7. The mean cortical volume was significantly higher in EE vs. SH animals (p=0.003). In summary, EE animals after lateral fluid percussion (LFP) brain injury performed significantly better than SH animals after 90 days of recovery. The window of opportunity may be wide and also lends further credibility to the importance of long term interventions in patients suffering from TBI.

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.

Progesterone inhibition of neuronal calcium signaling underlies aspects of progesterone-mediated neuroprotection

Progesterone is being utilized as a therapeutic means to ameliorate neuron loss and cognitive dysfunction following traumatic brain injury. Although there have been numerous attempts to determine the means by which progesterone exerts neuroprotective effects, studies describing the underlying molecular mechanisms are lacking. What has become clear, however, is the notion that progesterone can thwart several physiological processes that are detrimental to neuron function and survival, including inflammation, edema, demyelination and excitotoxicity. One clue regarding the means by which progesterone has restorative value comes from the notion that these aforementioned biological processes all share the common theme of eliciting pronounced increases in intracellular calcium. Thus, we propose the hypothesis that progesterone regulation of calcium signaling underlies its ability to mitigate these cellular insults, ultimately leading to neuroprotection. Further, we describe recent findings that indicate neuroprotection is achieved via progesterone block of voltage-gated calcium channels, although additional outcomes may arise from blockade of various other ion channels and neurotransmitter receptors. This article is part of a Special Issue entitled 'Neurosteroids'.

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.

Rehabilitation intervention in animal model can improve neuromotor and cognitive functions after traumatic brain injury: pilot study

The aim of the present study was to quantify the effect of multisensory rehabilitation on rats' cognition after an experimental brain trauma and to assess its possible clinical implications. The complex intermittent multisensory rehabilitation consisted of currently used major therapeutic procedures targeted at the improvement of cognitive functions; including multisensory and motor stimulation and enriched environment. We have confirmed this positive effect of early multisensory rehabilitation on the recovery of motor functions after traumatic brain injury. However, we have been able to prove a positive effect on the recovery of cognitive functions only with respect to the frequency of efficient search strategies in a Barnes maze test, while results for search time and travelled distance were not significantly different between study groups. We have concluded that the positive effects of an early treatment of functional deficits are comparable with the clinical results in early neurorehabilitation in human patients after brain trauma. It might therefore be reasonable to apply these experimental results to human medical neurorehabilitation care.

Minimally invasive assessment of the effect of mannitol and hypertonic saline therapy on traumatic brain edema using measurements of reduced scattering coefficient (μs')

Minimally invasive functional near infrared spectroscopy (fNIRs) technology was utilized to assess the effects of mannitol and hypertonic saline (HS) in treating traumatic brain edema (TBE). Rats with TBE models were given mannitol or HS in different dosages for different groups. The reduced scattering coefficient (μ(s)') of the local cortex of rats was simultaneously monitored and recorded in vivo and real time by the minimally invasive fNIRs system. Brain water content (BWC) was measured by the wet and dry weight method at 1, 6, 24, 72, and 120 h after injury and treatment. Effects of treating TBE with different dehydration agents were then assessed by recording μ(s)' and BWC before and after administration of dehydration. In this study, the dynamic changes of brain edema and the effects of dehydration therapy were continuously monitored. Results implied that μ(s)' of the local cortex in rats is a good indicator for assessing effects of treatment of TBE. By recording changes in the value of μ(s)', the following conclusions were obtained: HS is more effective than mannitol in reducing cerebral edema. The effect of dehydration of HS is only related to osmotic gradient and has no correlation with concentration.

Aquaporin-1-mediated cerebral edema following traumatic brain injury: effects of acidosis and corticosteroid administration

OBJECT

Dysregulation of water homeostasis induces cerebral edema. Edema is a major cause of morbidity and mortality following traumatic brain injury (TBI). Aquaporin-1 (AQP-1), a water channel found in the brain, can function as a transporter for CO2 across the cellular membrane. Additionally, AQP-1's promoter contains a glucocorticoid response element. Thus, AQP-1 may be involved with edema-related brain injury and might be modulated by external conditions such as the pH and the presence of steroids. In this study, the authors investigated the hypotheses that: 1) AQP-1 participates in brain water homeostasis following TBI; 2) secondary injury (for example, acidosis) alters the expression of AQP-1 and exacerbates cerebral edema; and 3) corticosteroids augment brain AQP-1 expression and differentially affect cerebral edema under nonacidotic and acidotic conditions.

METHODS

Anesthetized Sprague-Dawley rats were subjected to moderate to severe TBI (2.5-3.5 atm) or surgery without injury, and they were randomized to receive a 3-mg/kg bolus of intravenous dexamethasone within 10 minutes after injury or surgery, a 3-mg/kg bolus of dexamethasone followed by 1-mg/kg maintenance doses every 8 hours for 24 hours, or saline boluses at similar time intervals. A second group of animals was subjected to respiratory acidosis with target arterial blood pH 6.8-7.2 for 1 hour following the surgery or injury. To evaluate selective blockage of AQP-1, some animals received a single intraperitoneal dose of HgCl2 (0.3-30.0 mmol/L) within 30 minutes of injury or surgery. At 4 or 24 hours postinjury, animals were killed and their brains were harvested for mRNA, protein, or water content analyses.

RESULTS

The authors demonstrated elevated cerebral edema levels at 4 and 24 hours following TBI. Dexamethasone administration within 1 hour of TBI attenuated the cerebral edema under nonacidotic conditions but worsened it under acidotic conditions. Selective blockage of AQP-1 channels with HgCl2 attenuated the edematous effects of corticosteroids and acidosis. Reverse transcriptase polymerase chain reaction and immunohistochemical analyses demonstrated a paucity of AQP-1 in the cerebral cortices of the uninjured animals. In contrast, AQP-1 mRNA and protein levels were higher in the cerebral cortices of animals that sustained a TBI.

CONCLUSIONS

These findings implicate an important, modifiable role for AQP-1 in water homeostasis within the CNS following TBI.

Pharyngeal selective brain cooling improves neurofunctional and neurocognitive outcome after fluid percussion brain injury in rats

Therapeutic hypothermia (TH) after cardiac arrest reduces mortality and improves neurological outcome. Experimental TH after traumatic brain injury (TBI) indicated similar effects, but benefits were not reproducible in large clinical trials. Therefore, a novel approach of pharyngeal selective brain cooling (pSBC) was tested in respect to neurological outcome in a model of experimental TBI. Male Sprague-Dawley rats were subjected to lateral fluid percussion (LFP) brain injury and received pSBC for 3h post-injury. All animals were examined for neuromotor and sensorimotor dysfunction and coordination: before and after injury, and during recovery on day post-injury (DPI) 7 and 14 using (i) the standardized Composite Neuroscore (NS) test and (ii) the Rotarod test. Recovery of cognitive function was assessed on days 10-14 using (iii) the Barnes Circular Maze (BCM). In pSBC-animals, brain temperature was selectively lowered to 33 +/- 0.5 degrees C at 15 min post-injury, keeping rectal temperature at a physiologic level. All animals subjected to TBI via LFP showed an identical pattern of severe neurofunctional impairment at 24 h after injury. In the time course of the experiment, pSBC-animals showed superior neurofunctional recovery on DPI 7 (p = 0.03) and 14 (p = 0.002). Similarly, distance, time, and maximum speed on the Rota-Rod were significantly increased in pSBC-animals on DPI 7 (p < 0.01) and 14 (p < 0.01), as well as latency, distance, and mean number of errors in the BCM on DPI 14 (p < 0.01). The novel approach of pSBC was associated with improved neuromotor, sensormotor, and neurocognitive outcome after experimental TBI.

Late effects of enriched environment (EE) plus multimodal early onset stimulation (MEOS) after traumatic brain injury in rats: Ongoing improvement of neuromotor function despite sustained volume of the CNS lesion

Recently we showed that the combination between MEOS and EE applied to rats for 7-15 days after traumatic brain injury (TBI) was associated with reduced CNS lesion volume and enhanced reversal of neuromotor dysfunction. In a continuation of this work, we tested whether these effects persisted for longer post-operative periods, e.g. 30 days post-injury (dpi). Rats were subjected to lateral fluid percussion (LFP) or to sham injury. After LFP, one third of the animals (injured and sham) was placed under conditions of standard housing (SH), one third was kept in EE-only, and one third received EE+MEOS. Standardized composite neuroscore (NS) for neurological functions and computerized analysis of the vibrissal motor performance were used to assess post-traumatic neuromotor deficits. These were followed by evaluation of the cortical lesion volume (CLV) after immunostaining for neuron-specific enolase, caspase 3 active, and GFAP. Finally, the volume of cortical lesion containing regeneration-associated proteins (CLV-RAP) was determined in sections stained for GAP-43, MAP2, and neuronal class III beta-tubulin. We found (i) no differences in the vibrissal motor performance; (ii) EE+MEOS rats performed significantly better than SH rats in NS; (iii) EE-only and EE+MEOS animals, but not SH rats, showed better recovery at 30 dpi than at 15 dpi; (iv) no differences among all groups in CLV (larger than that at 15 dpi) and CLV-RAP, despite a clear tendency to reduction in the EE-only and EE+MEOS rats. We conclude that EE+MEOS retards, but cannot prevent the increase of lesion volume. This retardation is sufficient for a continuous restoration of neurological functions.

Reversal of neuromotor and cognitive dysfunction in an enriched environment combined with multimodal early onset stimulation after traumatic brain injury in rats

This study was designed to investigate the additional benefits of a multimodal early onset stimulation (MEOS) paradigm when combined with enriched environment (EE) versus EE only and standard housing (SH) on the recovery after experimental traumatic brain injury (TBI). Male Sprague- Dawley rats were subjected to moderate lateral fluid percussion (LFP) brain injury (n = 40) or sham operation (n = 6). Thereafter, the injured and sham/EE + MEOS and EE only groups were placed into a complex EE consisting of tunnel-connected wide-bodied cages with various beddings, inclining platforms, and toys. Along with group living and environmental complexity, injured and sham/EE + MEOS animals were additionally exposed to a standardized paradigm of multimodal stimulation including auditory, visual, olfactory, and motor stimuli. In contrast, injured and sham/SH groups were housed individually without stimulation. A standardized composite neuroscore (NS) test was used to assess acute post-traumatic neuromotor deficits (24 h after injury) and recovery on days 7 and 15; recovery of cognitive function was assessed on days 11-15 using the Barnes maze. Neuromotor impairment was comparable in all injured animals at 24 h post-injury, but braininjured EE + MEOS rats performed significantly better than both brain-injured SH and EE groups when tested on post-injury days 7 and 15 (p = 0.004). Similarly, latencies to locate the hidden box under the Barnes maze platform were significantly shortened in EE + MEOS animals at day 15 (p = 0.003). These results indicate that the reversal of neuromotor and cognitive dysfunction after TBI can be substantially enhanced when MEOS is added to EE.

Environmental enrichment increases progenitor cell survival in the dentate gyrus following lateral fluid percussion injury

Neurons in the hilus of the dentate gyrus are lost following a lateral fluid percussion injury. Environmental enrichment is known to increase neurogenesis in the dentate in intact rats, suggesting that it might also do so following fluid percussion injury, and potentially provide replacements for lost neurons. We report that 1 h of daily environmental enrichment for 3 weeks increased the number of progenitor cells in the dentate following fluid percussion injury, but only on the ipsilesional side. In the dentate granule cell layer, but not the hilus, most progenitors had a neuronal phenotype. The rate of on going cell proliferation was similar across groups. Collectively, these results suggest that the beneficial effects of environmental enrichment on behavioral recovery following FP injury are not attributable to neuronal replacement in the hilus but may be related to increased neurogenesis in the granule cell layer.

Multimodal early onset stimulation combined with enriched environment is associated with reduced CNS lesion volume and enhanced reversal of neuromotor dysfunction after traumatic brain injury in rats

This study was designed to determine whether exposure to multimodal early onset stimulation (MEOS) combined with environmental enrichment (EE) after traumatic brain injury (TBI) would improve neurological recovery and to elucidate its morphological correlates. Male Sprague-Dawley rats were subjected to lateral fluid percussion (LFP) brain injury or to sham operation. After LFP, one-third of the animals (injured and sham) were placed under conditions of standard housing (SH), one-third were kept in EE only, and one-third received EE + MEOS. Assessment of neuromotor function 24 h post-injury using a standardized composite neuroscore test revealed an identical pattern of neurological impairment in all animals subjected to LFP. Neuromotor dysfunction in SH animals remained on a similar level throughout the experiment, while improvements were noted in both other groups 7 days post-injury (dpi). On 15 dpi, reversal of neuromotor dysfunction was significantly better in EE + MEOS animals vs. SH- and EE-only groups. In parallel, the comparison of lesion volume in EE + MEOS- vs. EE-only vs. SH rats revealed that animals exposed to EE + MEOS had consistently the lowest values (mm3, mean +/- SD; n = 6 rats in each group) as measured in serial brain sections immunostained for neuron-specific enolase (5.2 +/- 3.4 < or = 5.5 +/- 4.1 < 9.5 +/- 1.9), caspase 3-active/C3A (5.9 +/- 4.0 < or = 6.4 +/- 3.9 < 10.3 +/- 1.8) and glial fibrillary acidic protein (6.0 +/- 3.4 < or = 6.5 +/- 4.3 < 10.7 +/- 1.2). This first report on the effect of EE + MEOS treatment strongly indicates that the combined exposure reduces CNS scar formation and reverses neuromotor deficits after TBI in rats.

Animal models of head trauma

Animal models of traumatic brain injury (TBI) are used to elucidate primary and secondary sequelae underlying human head injury in an effort to identify potential neuroprotective therapies for developing and adult brains. The choice of experimental model depends upon both the research goal and underlying objectives. The intrinsic ability to study injury-induced changes in behavior, physiology, metabolism, the blood/tissue interface, the blood brain barrier, and/or inflammatory- and immune-mediated responses, makes in vivo TBI models essential for neurotrauma research. Whereas human TBI is a highly complex multifactorial disorder, animal trauma models tend to replicate only single factors involved in the pathobiology of head injury using genetically well-defined inbred animals of a single sex. Although such an experimental approach is helpful to delineate key injury mechanisms, the simplicity and hence inability of animal models to reflect the complexity of clinical head injury may underlie the discrepancy between preclinical and clinical trials of neuroprotective therapeutics. Thus, a search continues for new animal models, which would more closely mimic the highly heterogeneous nature of human TBI, and address key factors in treatment optimization.

Lateral fluid percussion brain injury: a 15-year review and evaluation

This article comprehensively reviews the lateral fluid percussion (LFP) model of traumatic brain injury (TBI) in small animal species with particular emphasis on its validity, clinical relevance and reliability. The LFP model, initially described in 1989, has become the most extensively utilized animal model of TBI (to date, 232 PubMed citations), producing both focal and diffuse (mixed) brain injury. Despite subtle variations in injury parameters between laboratories, universal findings are evident across studies, including histological, physiological, metabolic, and behavioral changes that serve to increase the reliability of the model. Moreover, demonstrable histological damage and severity-dependent behavioral deficits, which partially recover over time, validate LFP as a clinically-relevant model of human TBI. The LFP model, also has been used extensively to evaluate potential therapeutic interventions, including resuscitation, pharmacologic therapies, transplantation, and other neuroprotective and neuroregenerative strategies. Although a number of positive studies have identified promising therapies for moderate TBI, the predictive validity of the model may be compromised when findings are translated to severely injured patients. Recently, the clinical relevance of LFP has been enhanced by combining the injury with secondary insults, as well as broadening studies to incorporate issues of gender and age to better approximate the range of human TBI within study design. We conclude that the LFP brain injury model is an appropriate tool to study the cellular and mechanistic aspects of human TBI that cannot be addressed in the clinical setting, as well as for the development and characterization of novel therapeutic interventions. Continued translation of pre-clinical findings to human TBI will enhance the predictive validity of the LFP model, and allow novel neuroprotective and neuroregenerative treatment strategies developed in the laboratory to reach the appropriate TBI patients.

CHARACTERIZATION OF A NEW RAT MODEL OF EXPERIMENTAL COMBINED NEUROTRAUMA

Traumatic brain injury (TBI) is present in two-thirds of patients with multiple injuries and in one-third combined with injuries of the extremities. Studies on interactive effects between central and peripheral injuries are scarce due to the absence of clinically relevant models. To meet the demand for "more-hit" models, an experimental model of combined neurotrauma (CNT) incorporating a standardized TBI via lateral fluid percussion (LFP) together with a peripheral bone fracture, i.e., tibia fracture, is introduced. Sprague-Dawley rats were randomized to four experimental groups: controls (n = 10), animals with TBI (n = 30), animals with tibia fracture (n = 30), and animals with CNT (n = 30). Morphological aspects of brain and bone injury were analyzed via standard histopathological procedures and x-ray. Trauma-induced neuromotor dysfunction was assessed using a standardized neuroscore. For interactive effects between injuries, we studied the extent and temporal pattern of circulating interleukin 6 (IL-6) levels via immunoassay and callus formation at fracture sites by means of microradiography. LFP produced an ipsilateral lesion with cortical contusion, hemorrhage, mass shift, and neuronal cell loss (adjacent cortex and hippocampus CA-2/-3), along with contralateral neuromotor dysfunction. X-rays confirmed complete fractures in the middle of the bone shaft. The type of injury (P < 0.001) and time (P = 0.022) were significantly associated with increased IL-6 levels. CNT produced the highest IL-6 plasma levels with a maximum peak at 6 h after trauma (P < 0.001). Similarly, callus formation at fracture sites in CNT was significantly increased versus fracture only (P < 0,01). The CNT model mimics a variety of clinically relevant features known from human multiple injury, including TBI, and offers novel approaches for investigation of interactive mechanisms and therapeutic approaches.

Differential Effects of the Anticonvulsant Topiramate on Neurobehavioral and Histological Outcomes following Traumatic Brain Injury in Rats

The efficacy of topiramate, a novel therapeutic agent approved for the treatment of seizure disorders, was evaluated in a model of traumatic brain injury (TBI). Adult male rats were anesthetized (sodium pentobarbital, 60 mg/kg, i.p.), subjected to lateral fluid percussion brain injury (n = 60) or sham injury (n = 47) and randomized to receive either topiramate or vehicle at 30 min (30 mg/kg, i.p.), and 8, 20 and 32 h postinjury (30 mg/kg, p.o.). In Study A, memory was evaluated using a Morris water maze at 48 h postinjury, after which brain tissue was evaluated for regional cerebral edema. In Study B, animals were evaluated for motor function at 48 h and 1, 2, 3, and 4 weeks postinjury using a composite neuroscore and the rotating pole test and for learning ability at 4 weeks. Brains were analyzed for hemispheric tissue loss and hippocampal CA3 cell loss. Topiramate had no effect on posttraumatic cerebral edema or histologic damage when compared to vehicle. At 48 h, topiramate treatment improved memory function in sham but not brain-injured animals, while at one month postinjury it impaired learning performance in brain-injured but not sham animals. Topiramate significantly improved composite neuroscores at 4 weeks postinjury and rotating pole performance at 1 and 4 weeks postinjury, suggesting a potentially beneficial effect on motor function following TBI.

Moderate zinc deficiency increases cell death after brain injury in the rat

Zinc supplementation has been used clinically to reduce Zn losses and protein turnover in patients suffering from traumatic brain injury. Despite the known role of zinc in cell survival and integrity, the influence of zinc status on central nervous system wound healing in the weeks and months after brain injury has not been addressed. In this investigation, we examined cell death after unilateral cortical stab wounds in adult rats (n = 5 per group) that were provided diets containing adequate zinc (30 mg Zn/kg diet), supplemental zinc (180 mg/kg), or moderately deficient zinc (5 mg/kg). Four weeks following the brain injury there was a 1.82-2.65-fold increase in terminal deoxynucleotidyl transferase-mediated biotinylated dUTP nick-end labeling (TUNEL)-positive cells with DNA fragmentation at the site of injury in animals receiving a moderately zinc deficient diet compared to animals receiving a zinc-adequate or supplemented diet (p0.05). Examination of the nuclear morphology of these cells suggested the presence of both apoptosis and necrosis. Immunohistochemistry showed that the TUNEL-positive cells expressed both ED-1 and OX-42, identifying them as microglia/macrophages. Thus it appears that adequate zinc status may be necessary to minimize the amount of neuroimmune cell death after brain injury.

Environmental enrichment attenuates cognitive deficits, but does not alter neurotrophin gene expression in the hippocampus following lateral fluid percussion brain injury

Environmental enrichment attenuates neurological deficits associated with experimental brain injury. The molecular events that mediate these environmentally induced improvements in function after injury are largely unknown, but neurotrophins have been hypothesized to be a neural substrate because of their role in cell survival and neural plasticity. Furthermore, exposure to complex environments in normal animals increases neurotrophin gene expression. However, following an ischemic injury, environmental enrichment decreases neurotrophin mRNA levels. Whether these contrasting findings are attributable to differences between injured and uninjured animals or are dependent upon the specific type of brain injury has not been determined. We examined the effects of 14 days of environmental enrichment following a lateral fluid percussion brain injury on behavior and gene expression of brain-derived neurotrophic factor, its high-affinity receptor, TrkB, and neurotrophin-3 in the rat hippocampus. Environmental enrichment attenuated learning deficits in the injured animals, but neither the injury nor housing conditions influenced neurotrophin/receptor mRNA levels. From these data we suggest that following brain trauma, improvements in learning associated with environmental enrichment are not mediated by alterations in brain-derived neurotrophic factor, TrkB or neurotrophin-3 gene expression.

The maxi-K channel opener BMS-204352 attenuates regional cerebral edema and neurologic motor impairment after experimental brain injury

Large-conductance, calcium-activated potassium (maxi-K) channels regulate neurotransmitter release and neuronal excitability, and openers of these channels have been shown to be neuroprotective in models of cerebral ischemia. The authors evaluated the effects of postinjury systemic administration of the maxi-K channel opener, BMS-204352, on behavioral and histologic outcome after lateral fluid percussion (FP) traumatic brain injury (TBI) in the rat. Anesthetized Sprague-Dawley rats (n = 142) were subjected to moderate FP brain injury (n = 88) or surgery without injury (n = 54) and were randomized to receive a bolus of 0.1 mg/kg BMS-204352 (n = 26, injured; n = 18, sham), 0.03 mg/kg BMS-204352 (n = 25, injured; n = 18, sham), or 2% dimethyl sulfoxide (DMSO) in polyethylene glycol (vehicle, n = 27, injured; n = 18, sham) at 10 minutes postinjury. One group of rats was tested for memory retention (Morris water maze) at 42 hours postinjury, then killed for evaluation of regional cerebral edema. A second group of injured/sham rats was assessed for neurologic motor function from 48 hours to 2 weeks postinjury and cortical lesion area. Administration of 0.1 mg/kg BMS-204352 improved neurologic motor function at 1 and 2 weeks postinjury (P < 0.05) and reduced the extent of cerebral edema in the ipsilateral hippocampus, thalamus, and adjacent cortex (P < 0.05). Administration of 0.03 mg/kg BMS-204352 significantly reduced cerebral edema in the ipsilateral thalamus (P < 0.05). No effects on cognitive function or cortical tissue loss were observed with either dose. These results suggest that the novel maxi-K channel opener BMS-204352 may be selectively beneficial in the treatment of experimental TBI.

Infusion of prostacyclin following experimental brain injury in the rat reduces cortical lesion volume

Endothelial-derived prostacyclin is an important regulator of microvascular function, and its main actions are inhibition of platelet/leukocyte aggregation and adhesion, and vasodilation. Disturbances in endothelial integrity following traumatic brain injury (TBI) may result in insufficient prostacyclin production and participate in the pathophysiological sequelae of brain injury. The objective of this study was to evaluate the potential therapeutic effects of a low-dose prostacyclin infusion on cortical lesion volume, CA3 neuron survival and functional outcome following TBI in the rat. Anesthetized animals (sodium pentobarbital, 60 mg/kg, i.p.) were subjected to a lateral fluid percussion brain injury (2.5 atm) or sham injury. Following TBI, animals were randomized to receive a constant infusion of either prostacyclin (1 ng/kg x min(-1) i.v.) or vehicle over 48 h. All sham animals received vehicle (n = 6). Evaluation of neuromotor function, lesion volume, and CA3 neuronal loss was performed blindly. By 7 days postinjury, cortical lesion volume was significantly reduced by 43% in the prostacyclin-treated group as compared to the vehicle treated group (p < 0.01; n = 12 prostacyclin, n = 12 vehicle). No differences were observed in neuromotor function (48 h and 7 days following TBI), or in hippocampal cell loss (7 days following TBI) between the prostacyclin- and vehicle-treated groups. We conclude that prostacyclin in a low dose reduces loss of neocortical neurons following TBI and may be a potential clinical therapeutic agent to reduce neuronal cell death associated with brain trauma.

Nicardipine improves the antidepressant action of ECT but does not improve cognition

INTRODUCTION

Cognitive impairment, the most important adverse effect of electroconvulsive therapy (ECT), may involve elevated intracellular calcium ion signaling. Animal research suggests that calcium channel-blocking agents, which attenuate excessive intracellular calcium activity, may reduce cognitive dysfunction caused by ECT.

METHOD

The lipid-soluble calcium channel-blocking drug nicardipine or matching placebo were randomly assigned to 26 patients with major depressive disorder receiving ECT. A rater blind to the experimental condition administered the Hamilton Depression Rating Scale, the Montgomery-Asberg Depression Rating Scale, the Beck Depression Inventory, the Mini-Mental State Examination and a comprehensive battery of neuropsychological tests prior to ECT, at the completion of ECT, and 6 months after ECT completion.

RESULTS

Compared with patients receiving placebo, patients taking nicardipine had significantly lower scores on the Hamilton and Montgomery-Asberg but not the Beck Depression rating scale scores at the completion of ECT. There were no differences between placebo and nicardipine groups in depression scores 6 months after ECT. Cognitive function declined over the course of ECT and improved over the next 6 months in both groups, but changes were statistically significant for only two subtests on the neuropsychological battery. Changes in Mini-Mental State Examination scores were small and were not significant at any point. There were no significant differences between nicardipine and placebo treated groups in any assessment of cognition.

DISCUSSION

Standard approaches to ECT in younger patients without preexisting neurological impairment do not produce cognitive side effects of sufficient severity for calcium channel-blocking agents to reduce these side effects demonstrably. Studies of treatments for cognitive impairment should be conducted in patients with risk factors for more severe cognitive impairment such as geriatric patients or patients with a history of interictal delirium during previous treatment with ECT. A possible effect of nicardipine in enhancing the antidepressant action of ECT requires further investigation in a study designed to test this action.

Brain-derived neurotrophic factor administration after traumatic brain injury in the rat does not protect against behavioral or histological deficits

Brain-derived neurotrophic factor has been shown to be neuroprotective in models of excitotoxicity, axotomy and cerebral ischemia. The present study evaluated the therapeutic potential of brain-derived neurotrophic factor following traumatic brain injury in the rat. Male Sprague-Dawley rats (N=99) were anesthetized and subjected to lateral fluid percussion brain injury of moderate severity (2.4-2.8 atm) or sham injury. Four hours after injury, the animals were reanesthetized, an indwelling, intraparenchymal cannula was implanted, and infusion of brain-derived neurotrophic factor or phosphate-buffered saline vehicle was initiated from a mini-osmotic pump and continued for two weeks. In Study 1 (N=48), vehicle or 12 microg/day of brain-derived neurotrophic factor was infused into the dorsal hippocampus. In Study 2 (N=51), vehicle or brain-derived neurotrophic factor at a high (12 microg/day) or low dose (1.2 microg/day) was infused into the injured parietal cortex. All animals were evaluated for neurological motor function at two days, one week and two weeks post-injury. Cognitive function (learning and memory) was assessed at two weeks post-injury using a Morris Water Maze. At two weeks post-injury, neuronal loss in the hippocampal CA3 and dentate hilus and in the injured cortex was evaluated. In Study 2, neuronal loss was also quantified in the thalamic medial geniculate nucleus. All of the above outcome measures demonstrated significant deleterious effects of brain injury (P<0.05 compared to sham). However, post-traumatic brain-derived neurotrophic factor infusion did not significantly affect neuromotor function, learning, memory or neuronal loss in the hippocampus, cortex or thalamus when compared to vehicle infusion in brain-injured animals, regardless of the infusion site or infusion dose (P>0.05 for each). In contrast to previous studies of axotomy, ischemia and excitotoxicity, our data indicate that brain-derived neurotrophic factor is not protective against behavioral or histological deficits caused by experimental traumatic brain injury using the delayed, post-traumatic infusion protocol examined in these studies.

The rotating pole test: evaluation of its effectiveness in assessing functional motor deficits following experimental head injury in the rat

Neurological motor dysfunction is often an integral component of the neurological sequelae of traumatic brain injury (TBI). In experimental TBI, neurological motor testing is an outcome measure used to monitor severity of injury, and the response to treatment. This study evaluates the effectiveness and sensitivity of the rotating pole test (RP) to characterize and evaluate the temporal course of motor deficits after lateral fluid percussion (FP) injury to the rat brain. The results are compared with the previously characterized and widely used composite neuroscore of motor function (NS). The animals were required to walk across an elevated wooden pole that was either stationary or rotating to left or right directions at different speeds. Male Wistar rats underwent lateral FP injury of moderate severity (mean 2.4 atm, n = 9) or sham surgery (n = 9), and were tested at 48 h and 7 days post-injury using the NS and RP. The results of the NS directly correlated to the results of the RP, showing a significant injury effect at both 48 h and 7 days. This is the first study to show that the RP-test detects neurological motor deficits after lateral FP injury, and suggests that this technique is a reliable behavioral tool for evaluating neurological motor function in the acute period after experimental TBI.

The novel compound LOE 908 attenuates acute neuromotor dysfunction but not cognitive impairment or cortical tissue loss following traumatic brain injury in rats

Experimental traumatic brain injury (TBI) initiates massive disturbances in Ca2+ concentrations in the brain that may contribute to neuronal damage. Intracellular Ca2+ may be elevated via influx through voltage-operated cation channels, ligand-gated ionotropic channels, and store-operated cation channels (SOCs). In the present study, we evaluated the neurobehavioral and histological effects of acute posttraumatic administration of (R,S)-(3,4-dihydro-6,7-dimethoxy-isoquinoline-1-yl)-2-phenyl-N,N-di[2-(2 ,3,4-trimethoxyphenyl)ethyl]-acetamide (LOE 908), a broad spectrum inhibitor of voltage-operated cation channels and SOCs. Male Sprague-Dawley rats (n = 53) were trained in the Morris water maze, anesthetized (60 mg/kg pentobarbital, i.p.), and subjected to lateral fluid percussion brain injury (2.5-2.7 atm; n = 38) or surgery without injury (n = 15). At 15 min postinjury, animals were randomized to receive intravenous administration of either a high dose of LOE 908 (4 mg/kg bolus followed by 160 mg/kg over 24 h; n = 13), a low dose of LOE 908 (2 mg/kg bolus followed by 80 mg/kg over 24 h; n = 12), or vehicle (n = 13). Uninjured controls received the high dose of LOE 908 (n = 8) or vehicle (n = 7). Treatment with either dose of LOE 908 significantly improved neuromotor function at 48 h postinjury when compared to vehicle treatment. Although a significant deficit in visuospatial memory was observed in brain-injured animals at this timepoint when compared to uninjured animals, neither dose of LOE 908 attenuated injury-induced cognitive dysfunction. Histological evaluation revealed that neither dose of LOE 908 affected cortical lesion size at 48 h postinjury. These data suggest that broad spectrum cation channel blockers may be beneficial in the treatment of neurological motor dysfunction when administered in the acute posttraumatic period.

Sequential pharmacotherapy with magnesium chloride and basic fibroblast growth factor after fluid percussion brain injury results in less neuromotor efficacy than that achieved with magnesium alone

Combinational pharmacotherapy with individually efficacious agents is a potential strategy for the treatment of traumatic central nervous system (CNS) injury. Basic fibroblast growth factor (bFGF) has been shown to be neuroprotective against excitotoxic, ischemic, and traumatic injury to the CNS, while acute posttraumatic treatment with magnesium (Mg2+) has been shown to decrease the motor and cognitive deficits following experimental brain injury. In this study, bFGF and Mg2+ were evaluated separately and in combination to assess their potential additive effects on posttraumatic neurological recovery and histological cell loss (lesion volume). Twenty minutes after fluid percussion (FP) brain injury of moderate severity (2.2-2.4 atm), anesthetized rats received a 15-min intravenous infusion of either 125 mumol of MgCl2 or vehicle, followed 5 min later by a 24-h constant intravenous infusion of either bFGF (16 micrograms/h) or vehicle. Injured animals had a significant motor deficit when compared to sham (uninjured) animals at both 48 h and 7 days postinjury. At 48 h postinjury, there were no significant differences among injured animals when compared by treatment. By 7 days postinjury, injured animals treated with MgCl2 alone displayed significantly improved motor function when compared to brain-injured, vehicle-treated animals (p < 0.05). Animals treated with either bFGF alone or a combination of MgCl2 and bFGF displayed no significant neurological improvement relative to vehicle-treated injured animals at 7 days. No effect of any drug treatment of combination was observed on the extent of the postinjury lesion volume in the injured cortex. These results suggest that caution must be exercised when combining "cocktails" of potentially neuroprotective compounds in the setting of traumatic brain injury.

Effects of six weeks of chronic ethanol administration on the behavioral outcome of rats after lateral fluid percussion brain injury

This study examined the effects of 6 weeks of chronic ethanol administration on the behavioral outcome in rats after lateral fluid percussion (FP) brain injury. Rats were given either an ethanol liquid diet (ethanol diet-groups) or a pair-fed isocaloric sucrose control diet (control diet groups) for 6 weeks. After 6 weeks, the ethanol diet was discontinued for the ethanol diet rats and they were then given the control sucrose diet for 2 days. During those 2 days, the rats were trained to perform a beam-walking task and subjected to either lateral FP brain injury of low to moderate severity (1.8 atm) or to sham operation. In both the control diet and the ethanol diet groups, lateral FP brain injury caused beam-walking impairment on days 1 and 2 and spatial learning disability on days 7 and 8 after brain injury. There were no significant differences in beam-walking performance and spatial learning disability between brain injured animals from the control and ethanol diet groups. However, a trend towards greater behavioral deficits was observed in brain injured animals in the ethanol diet group. Histologic analysis of both diet groups after behavioral assessment revealed comparable ipsilateral cortical damage and observable CA3 neuronal loss in the ipsilateral hippocampus. These results only suggest that chronic ethanol administration, longer than six weeks of administration, may worsen behavioral outcome following lateral FP brain injury. For more significant behavioral and/or morphological change to occur, we would suggest that the duration of chronic ethanol administration must be increased.

Enduring cognitive, neurobehavioral and histopathological changes persist for up to one year following severe experimental brain injury in rats

Clinical studies have demonstrated that patients sustain prolonged behavioral deficits following traumatic brain injury, in some cases culminating in the cognitive and histopathological hallmarks of Alzheimer's disease. However, few studies have examined the long-term consequences of experimental traumatic brain injury. In the present study, anesthetized male Sprague-Dawley rats (n = 185) were subjected to severe lateral fluid-percussion brain injury (n = 115) or sham injury (n = 70) and evaluated up to one year post-injury for cognitive and neurological deficits and histopathological changes. Compared with sham-injured controls, brain-injured animals showed a spatial learning impairment that persisted up to one year post-injury. In addition, deficits in specific neurologic motor function tasks also persisted up to one year post-injury. Immunohistochemistry using multiple antibodies to the amyloid precursor protein and/or amyloid precursor protein-like proteins revealed novel axonal degeneration in the striatum, corpus callosum and injured cortex up to one year post-injury and in the thalamus up to six months post-injury. Histologic evaluation of injured brains demonstrated a progressive expansion of the cortical cavity, enlargement of the lateral ventricles, deformation of the hippocampus, and thalamic calcifications. Taken together, these findings indicate that experimental traumatic brain injury can cause long-term cognitive and neurologic motor dysfunction accompanied by continuing neurodegeneration.

Novel pharmacologic strategies in the treatment of experimental traumatic brain injury: 1998

The mechanisms underlying secondary or delayed cell death following traumatic brain injury are poorly understood. Recent evidence from experimental models suggests that widespread neuronal loss is progressive and continues in selectively vulnerable brain regions for months to years after the initial insult. The mechanisms underlying delayed cell death are believed to result, in part, from the release or activation of endogenous "autodestructive" pathways induced by the traumatic injury. The development of sophisticated neurochemical, histopathological and molecular techniques to study animal models of TBI have enabled researchers to begin to explore the cellular and genomic pathways that mediate cell damage and death. This new knowledge has stimulated the development of novel therapeutic agents designed to modify gene expression, synthesis, release, receptor or functional activity of these pathological factors with subsequent attenuation of cellular damage and improvement in behavioral function. This article represents a compendium of recent studies suggesting that modification of post-traumatic neurochemical and cellular events with targeted pharmacotherapy can promote functional recovery following traumatic injury to the central nervous system.

The Dorothy Russell Memorial Lecture. The molecular and cellular sequelae of experimental traumatic brain injury: pathogenetic mechanisms

The mechanisms underlying secondary or delayed cell death following traumatic brain injury (TBI) are poorly understood. Recent evidence from experimental models of TBI suggest that diffuse and widespread neuronal damage and loss is progressive and prolonged for months to years after the initial insult in selectively vulnerable regions of the cortex, hippocampus, thalamus, striatum, and subcortical nuclei. The development of new neuropathological and molecular techniques has generated new insights into the cellular and molecular sequelae of brain trauma. This paper will review the literature suggesting that alterations in intracellular calcium with resulting changes in gene expression, activation of reactive oxygen species (ROS), activation of intracellular proteases (calpains), expression of neurotrophic factors, and activation of cell death genes (apoptosis) may play a role in mediating delayed cell death after trauma. Recent data suggesting that TBI should be considered as both an inflammatory and/or a neurodegenerative disease is also presented. Further research concerning the complex molecular and neuropathological cascades following brain trauma should be conducted, as novel therapeutic strategies continue to be developed.

Clinical evaluation of the effect of calcium-channel blockers on verbal learning

The effect of verapamil and nimodipine on verbal learning was evaluated in a double-blind clinical trial. Thirty-seven healthy volunteers were distributed in three groups to receive a treatment with nimodipine, verapamil or placebo. Neither verapamil nor nimodipine modifies verbal learning as measured by the selective remembering test of Buschke and Fuld.

Time course of cerebral edema after traumatic brain injury in rats: effects of riluzole and mannitol

Brain trauma is the main cause of morbidity and mortality in young adults. One delayed events that occurs after a head trauma and compromises the survival of patients is cerebral edema. The present study examined first the occurrence of cerebral edema after a traumatic brain injury (TBI) induced by moderate fluid percussion in rats. Brain water content was measured from 1 h to 7 days posttrauma, in the hippocampus and cortex, on both ipsi- and contralateral hemispheres. Second, the effects of mannitol, an osmotic agent frequently used in the clinic, and riluzole, a neuroprotective compound, were investigated on regional edema formation. After TBI, the ipsilateral edema began early at 1-6 h, was maximal at 48 h and was resorbed by 5-7 days. No edema was observed in the contralateral hemisphere. Mannitol at 1 g/kg or vehicle was administered iv 15 min, 2 h and 4 h postinjury. At this dose, mannitol significantly attenuated the ipsilateral injured cortex edema measured at 6 h (p < 0.05). Riluzole at 4 and 8 mg/kg or vehicle was administered 15 min (IV) and 6 h, 24 h, and 30 h (SC) post-TBI. Riluzole at 4 x 4 mg/kg significantly reduced edema measured at 48 h, in the ipsilateral hippocampus (p < 0.05), whereas at 4 x 8 mg/kg, the reduction was observed in the hippocampus (p < 0.01) and the injured cortex (p < 0.05). Our results demonstrate that (1) cerebral edema begins early after the injury and is resorbed over 1 week; (2) mannitol could attenuate cerebral edema; and (iii) riluzole in addition to its neuroprotective effects reduces the brain edema. Thus, riluzole could be useful in human TBI treatment.

Insulin-like growth factor-1 (IGF-1) improves both neurological motor and cognitive outcome following experimental brain injury

We evaluated the efficacy of insulin-like growth factor-1 (IGF-1) in attenuating neurobehavioral deficits following lateral fluid percussion (FP) brain injury. Male Sprague-Dawley rats (345-425 g, n = 88) were anesthetized and subjected to FP brain injury of moderate severity (2.4-2.9 atm). In Study 1, IGF-1 (1.0 mg/kg, n = 9) or vehicle (n = 14) was administered by subcutaneous injection at 15 min postinjury and similarly at 12-h intervals for 14 days. In animals evaluated daily for 14 days, IGF-1 treatment attenuated motor dysfunction over the 2-week period (P < 0.02). In Study 2, IGF-1 (4 mg/kg/day, n = 8 uninjured, n = 13 injured) or vehicle (n = 8 uninjured, n = 13 injured) was administered for 2 weeks via a subcutaneous pump implanted 15 min postinjury. IGF-1 administration was associated with increased body weight and mild, transient hypoglycemia which was more pronounced in brain-injured animals. At 2 weeks postinjury (P < 0.05), but not at 48 h or 1 week, brain-injured animals receiving IGF-1 showed improved neuromotor function compared with those receiving vehicle. IGF-1 administration also enhanced learning ability (P < 0.03) and memory retention (P < 0.01) in brain-injured animals at 2 weeks postinjury. Taken together, these data suggest that chronic, posttraumatic administration of the trophic factor IGF-1 may be efficacious in ameliorating neurobehavioral dysfunction associated with traumatic brain injury.

Central nervous system resuscitation

Traumatic injury to the central nervous system induces delayed neuronal death, which may be mediated by acute and chronic neurochemical changes. Experimental identification of these injury mechanisms and elucidation of the neurochemical cascade following trauma may provide enhanced opportunities for treatment with novel neuroprotective strategies.

Paradoxical effects of acute ethanolism in experimental brain injury

Acute ethanol intoxication is a frequent complicating factor in human head injury, yet its impact on neurological outcome remains poorly defined. This study was undertaken to assess the effect of varying levels of preinjury ethanol on early postinjury mortality, recovery of motor function, and degree of neural degeneration after cortical contusion injury in the rat. Adult rats were pretrained on a beam-walking task, then randomized to one of five groups: low-dose ethanol and injury (1 g/kg, 16 animals); moderate-dose ethanol and injury (2.5 g/kg, 11 animals); high-dose ethanol and injury (3 g/kg, 17 animals); no ethanol and injury (nine animals); or ethanol and sham injury (seven animals). Forty minutes after intraperitoneal injection of ethanol or saline, the rats received a pneumatic piston-induced contusion injury of the left primary motor cortex. Their beam-walking ability was assessed daily for the next 7 days. At 4 weeks postinjury, the brains were sectioned and the dimensions of the cortical lesions were determined. Preinjury ethanol administration was associated with an acute postinjury mortality rate of 29.5% (p < 0.05); the highest mortality rate (47.1%) occurred in the high-dose ethanol group, whereas no deaths occurred in the animals in the no ethanol or sham-injured groups (p < 0.01). However, injured animals receiving low- and moderate-dose ethanol had significantly less severe beam-walking impairment initially, and a more rapid return to normal beam-walking ability, compared to the no and high-dose ethanol groups (p < 0.05). Additionally, the mean lesion volumes were significantly smaller in the low- and moderate-dose ethanol treatment groups compared to the no and high-dose ethanol groups (23.2 +/- 8 mm3 and 29 +/- 6.7 mm3 vs. 52 +/- 8.8 mm3 and 53.7 +/- 10.9 mm3, respectively, p < 0.01). In this cortical contusion model, the presence of ethanol before injury appears to exert a potent neuroprotective effect when administered in low or moderate doses. This action is postulated to result from ethanol-induced inhibition of N-methyl-D-aspartate receptor-mediated excitotoxicity. The loss of neuroprotection and increased mortality rates observed with high-dose ethanol may be related to ethanol-induced hemodynamic and respiratory depression.

Delayed administration of basic fibroblast growth factor (bFGF) attenuates cognitive dysfunction following parasagittal fluid percussion brain injury in the rat

The present study evaluates the therapeutic effects of delayed administration of bFGF on cognitive dysfunction and histopathological damage following lateral fluid-percussion (FP) brain injury. Male Sprague-Dawley rats were trained to learn a visuospatial task in a Morris Water Maze (MWM) paradigm and then were anesthetized and subjected to either FP brain injury of moderate severity (2.5-2.8 atm, n = 32) or surgery without brain injury (n = 10). Twenty-four hours postinjury, an infusion cannula connected to a mini-osmotic pump was implanted into the area of maximal cortical injury to continuously infuse either bFGF (2.0 g) or vehicle for 7 days. Treatment with bFGF significantly attenuated posttraumatic memory dysfunction in the MWM at 8 days postinjury when compared to vehicle treatment (p < 0.05). The cortical lesion and significant cell loss in the ipsilateral CA3 region of the hippocampus, produced by FP injury, was not affected by bFGF treatment. However, immunohistochemical evaluation of glial fibrillary acidic protein revealed a trend toward increased astrocytosis in the injured cortex of bFGF-treated animals compared to vehicle-treated animals (p < 0.1). These results indicate that bFGF may be efficacious in attenuating cognitive dysfunction associated with traumatic brain injury.

Effects of the novel NMDA antagonists CP-98,113, CP-101,581 and CP-101,606 on cognitive function and regional cerebral edema following experimental brain injury in the rat

The present study evaluated the effects of two novel N-methyl-D-aspartate (NMDA) receptor blockers and ifenprodil derivatives, CP-101,606 and CP-101,581, and their racemic mixture CP-98,113, on spatial memory and regional cerebral edema following experimental fluid-percussion (FP) brain injury in the rat (n = 66). Fifteen minutes after brain injury (2.5 atm), animals received either (1) CP-98,113 (5 mg/kg, i.p., n = 11), (2) CP-101,581 (5 mg/kg, i.p., n = 13), (3) CP-101,606 (6.5 mg/kg, i.p., n = 12), or (4) DMSO vehicle (equal volume, n = 12); followed by a continuous 24-h subcutaneous infusion of drug at a rate of 1.5 mg/kg/h by means of miniature osmotic (Alzet) pumps implanted subcutaneously. Control (uninjured) animals were subjected to identical anesthesia and surgery without injury and received DMSO vehicle (n = 8); CP-98,113 (5 mg/kg, i.p., n = 3); CP-101,581 (5 mg/kg, i.p., n = 3); or CP-101,606 (6.5 mg/kg, i.p., n = 3). FP brain injury produced a significant cognitive impairment assessed at 2 days postinjury using a well-characterized testing paradigm of visuospatial memory in the Morris Water Maze (MWM) (p < 0.001). Administration of either CP-98,113, CP-101,581, or CP-101,606 had no effect on sham (uninjured) animals, but significant attenuated spatial memory impairment assessed at 2 days postinjury (p = 0.004, p = 0.02, or p = 0.02, respectively). Administration of CP-89,113 but not CP-101,581 or CP-101,606 significantly reduced the extent of regional cerebral edema in the cortex adjacent to the site of injury (p < 0.05) and in the ipsilateral hippocampus (p < 0.05) and thalamus (p < 0.05). These results suggest that excitatory neurotransmission may play a pivotal role in the pathogenesis of memory dysfunction following traumatic brain injury (TBI) and that blockade of the NMDA receptor may significantly attenuate cognitive deficits associated with TBI.