Rosiglitazone attenuates inflammation and CA3 neuronal loss following traumatic brain injury in rats.

Rosiglitazone, a potent peroxisome proliferator-activated receptor (PPAR)-γ agonist, has been shown to confer neuroprotective effects in stroke and spinal cord injury, but its role in the traumatic brain injury (TBI) is still controversial. Using a controlled cortical impact model in rats, the current study was designed to determine the effects of rosiglitazone treatment (6 mg/kg at 5 min, 6 h and 24 h post injury) upon inflammation and histological outcome at 21 d after TBI. In addition, the effects of rosiglitazone upon inflammatory cytokine transcription, vestibulomotor behavior and spatial memory function were determined at earlier time points (24 h, 1-5 d, 14-20 d post injury, respectively). Compared with the vehicle-treated group, rosiglitazone treatment suppressed production of TNFα at 24 h after TBI, attenuated activation of microglia/macrophages and increased survival of CA3 neurons but had no effect on lesion volume at 21 d after TBI. Rosiglitazone-treated animals had improved performance on beam balance testing, but there was no difference in spatial memory function as determined by Morris water maze. In summary, this study indicates that rosiglitazone treatment in the first 24 h after TBI has limited anti-inflammatory and neuroprotective effects in rat traumatic injury. Further study using an alternative dosage paradigm and more sensitive behavioral testing may be warranted.

Systemic treatment with ubiquitin carboxy terminal hydrolase L1 TAT protein ameliorates axonal injury and reduces functional deficits after traumatic brain injury in mice.

Traumatic brain injury (TBI) is often associated with axonal injury that leads to significant motor and cognitive deficits. Ubiquitin carboxy terminal hydrolase L1 (UCHL1) is highly expressed in neurons and loss of its activity plays an important role in the pathogenesis of TBI. Fusion protein was constructed containing wild type (WT) UCHL1 and the HIV trans-activator of transcription capsid protein transduction domain (TAT-UCHL1) that facilitates transport of the protein into neurons after systemic administration. Additional mutant proteins bearing cysteine to alanine UCHL1 mutations at cysteine 152 (C152A TAT-UCHL1) that prevents nitric oxide and reactive lipid binding of C152, and at cysteine 220 (C220A TAT-UCHL1) that inhibits farnesylation of the C220 site were also constructed. WT, C152A, and C220A TAT-UCHL1 proteins administered to mice systemically after controlled cortical impact (CCI) were detectable in brain at 1 h, 4 h and 24 h after CCI by immunoblot. Mice treated with C152A or WT TAT-UCHL1 decreased axonal injury detected by NF200 immunohistochemistry 24 h after CCI, but C220A TAT-UCHL1 treatment had no significant effect. Further study indicated that WT TAT-UCHL1 treatment administered 24 h after CCI alleviated axonal injury as detected by SMI32 immunoreactivity 7 d after CCI, improved motor and cognitive deficits, reduced accumulation of total and K48-linked poly-Ub proteins, and attenuated the increase of the autophagy marker Beclin-1. These results suggest that UCHL1 activity contributes to the pathogenesis of white matter injury, and that restoration of UCHL1 activity by systemic treatment with WT TAT-UCHL1 after CCI may improve motor and cognitive deficits. These results also suggest that farnesylation of the C220 site may be required for the protective effects of UCHL1.

Abolishing UCHL1's hydrolase activity exacerbates TBI-induced axonal injury and neuronal death in mice.

Ubiquitin (Ub) C-terminal hydrolase L1 (UCHL1) is a multifunctional protein that is expressed in neurons throughout brain at high levels. UCHL1 deletion is associated with axonal degeneration, progressive sensory motor ataxia, and premature death in mice. UCHL1 has been hypothesized to play a role in the pathogenesis of neurodegenerative diseases and recovery after neuronal injury. UCHL1 hydrolyzes Ub from polyubiquitinated (poly-Ub) proteins, but also may ligate Ub to select neuronal proteins, and interact with cytoskeletal proteins. These and other mechanisms have been hypothesized to underlie UCHL1's role in neurodegeneration and response to brain injury. A UCHL1 knockin mouse containing a C90A mutation (C90A) devoid of hydrolase activity was constructed. The C90A mouse did not develop the sensory and motor deficits, degeneration of the gracile nucleus and tract, or premature death as seen in UCHL1 deficient mice. C90A and wild type (WT) mice were subjected to the controlled cortical impact (CCI) model of traumatic brain injury (TBI), and cell death, axonal injury and behavioral outcome were assessed. C90A mice exhibited decreased spared tissue volume, greater loss of CA1 hippocampal neurons and greater axonal injury as detected using anti-amyloid precursor protein (APP) antibody and anti- non-phosphorylated neurofilament H (SMI-32) antibody immunohistochemistry after CCI compared to WT controls. Poly-Ub proteins and Beclin-1 were elevated after CCI in C90A mice compared to WT controls. Vestibular motor deficits assessed using the beam balance test resolved by day 5 after CCI in WT mice but not in C90A mice. These results suggest that the hydrolase activity of UCHL1 does not account for the progressive neurodegeneration and premature death seen in mice that do not express full length UCHL1. The hydrolase activity of UCHL1 contributes to the function of the ubiquitin proteasome pathway (UPP), ameliorates activation of autophagy, and improves motor recovery after CCI. Thus, UCHL1 hydrolase activity plays an important role in acute injury response after TBI.

Mutation of a Ubiquitin Carboxy Terminal Hydrolase L1 Lipid Binding Site Alleviates Cell Death, Axonal Injury, and Behavioral Deficits After Traumatic Brain Injury in Mice.

Ubiquitin carboxy terminal hydrolase L1 (UCHL1) is a protein highly expressed in neurons that may play important roles in the ubiquitin proteasome pathway (UPP) in neurons, axonal integrity, and motor function after traumatic brain injury (TBI). Binding of reactive lipid species to cysteine 152 of UCHL1 results in unfolding, aggregation, and inactivation of the enzyme. To test the role of this mechanism in TBI, mice bearing a cysteine to alanine mutation at site 152 (C152A mice) that renders UCHL1 resistant to inactivation by reactive lipids were subjected to the controlled cortical impact model (CCI) of TBI and compared to wild type (WT) controls. Alterations in protein ubiquitination and activation of autophagy pathway markers in traumatized brain were detected by immunoblotting. Cell death and axonal injury were determined by histological assessment and anti-amyloid precursor protein (APP) immunohistochemistry. Behavioral outcomes were determined using the beam balance and Morris water maze tests. C152A mice had reduced accumulation of ubiquitinated proteins, decreased activation of the autophagy markers Beclin-1 and LC3B, a decreased number of abnormal axons, decreased CA1 cell death, and improved motor and cognitive function compared to WT controls after CCI; no significant change in spared tissue volume was observed. These results suggest that binding of lipid substrates to cysteine 152 of UCHL1 is important in the pathogenesis of injury and recovery after TBI and may be a novel target for future therapeutic approaches.

Neurogranin Protein Expression Is Reduced after Controlled Cortical Impact in Rats.

Traumatic brain injury (TBI) is known to cause short- and long-term synaptic changes in the brain, possibly underlying downstream cognitive impairments. Neuronal levels of neurogranin, a calcium-sensitive calmodulin-binding protein essential for synaptic plasticity and postsynaptic signaling, are correlated with cognitive function. This study aims to understand the effect of TBI on neurogranin by characterizing changes in protein expression at various time points after injury. Adult, male rats were subjected to either controlled cortical impact (CCI) or control surgery. Expression of neurogranin and post-synaptic density 95 (PSD-95) were evaluated by Western blot in the cortex and hippocampus at 24 h and 1, 2, and 4 weeks post-injury. We hypothesized that CCI reduces neurogranin levels in the cortex and hippocampus, and demonstrate different expression patterns from PSD-95. Neurogranin levels were reduced in the ipsilateral cortex and hippocampus up to 2 weeks after injury but recovered to sham levels by 4 weeks. The contralateral cortex and hippocampus were relatively resistant to changes in neurogranin expression post-injury. Qualitative immunohistochemical assessment corroborated the immunoblot findings. Particularly, the pericontusional cortex and ipsilateral Cornu Ammonis (CA)3 region showed marked reduction in immunoreactivity. PSD-95 demonstrated similar expression patterns to neurogranin in the cortex; however, in the hippocampus, protein expression was increased compared with sham at the 2 and 4 week time points. Our results indicate that CCI lowers neurogranin expression with temporal and regional specificity and that this occurs independently of dendritic loss. Further understanding of the role of neurogranin in synaptic biology after TBI will elucidate pathological mechanisms contributing to cognitive dysfunction.

Delayed increase of tyrosine hydroxylase expression in rat nigrostriatal system after traumatic brain injury.

Tyrosine hydroxylase (TH) is the key enzyme for synthesizing dopamine (DA) in dopaminergic neurons and its terminals. Emerging experimental and clinical evidence support the hypothesis of a disturbance in dopamine neurotransmission following traumatic brain injury (TBI). However, the effect of controlled cortical impact (CCI) injury on TH in the nigrostriatal system is currently unknown. To determine if there is an alteration in TH after CCI injury, we examined TH levels at 1 day, 7 days, and 28 days post-injury by utilizing a commercially available antibody specific to TH. Rats were anesthetized and surgically prepared for CCI injury (4 m/s, 3.2 mm) or sham surgery. Injured (N=6) and sham animals (N=6) were sacrificed and coronally sectioned (35 microm thick) through the striatum and substantia nigra (SN) for immunohistochemistry. Additionally, semiquantitative measurements of TH protein in striatal and SN homogenates from injured (N=6) and sham (N=6) rats sacrificed at the appropriate time post-surgery were assessed using Western blot analysis. TH protein is bilaterally increased at 28 days post-injury in nigrostriatal system revealed by immunohistochemistry in injured rats compared to sham controls. Western blot analysis confirms the findings of immunohistochemistry in both striatum and SN. We speculate that the increase in TH in the nigrostriatal system may reflect a compensatory response of dopaminergic neurons to upregulate their synthesizing capacity and a delayed increase in the efficiency of DA neurotransmission after TBI.

Sex and genetic associations with cerebrospinal fluid dopamine and metabolite production after severe traumatic brain injury.

OBJECT: Dopamine (DA) pathways have been implicated in cognitive deficits after traumatic brain injury (TBI). Both sex and the dopamine transporter (DAT) 3' variable number of tandem repeat polymorphism have been associated with differences in DAT protein density, and DAT protein affects both presynaptic DA release, through reverse transport, and DA reuptake. Catecholamines and associated metabolites are subject to autooxidation, resulting in the formation of reactive oxygen species that may contribute to subsequent oxidative injury. The purpose of this study was to determine associations between factors that affect DAT expression and cerebrospinal fluid (CSF) DA and metabolite levels after severe TBI. METHODS: Sixty-three patients with severe TBI (Glasgow Coma Scale score < or = 8) were evaluated. The patients' genotypes were obtained using previously banked samples of CSF, and serial CSF samples (416 samples) were used to evaluate DA and metabolite levels. High-performance liquid chromatography was used to determine CSF levels of DA, 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) during the first 5 days after injury. Mixed-effects multivariate regression modeling revealed that patients with the DAT 10/10 genotype had higher CSF DA levels than patients with either the DAT 9/9 or DAT 9/10 genotypes (p = 0.009). Females with the DAT 10/10 genotype had higher CSF DA levels than females with the DAT 9/9 or DAT 9/10 genotypes, and sex was associated with higher DOPAC levels (p = 0.004). Inotrope administration also contributed to higher DA levels (p = 0.002). CONCLUSIONS: In addition to systemic administration of DA, inherent factors such as sex and DAT genotype affect post-TBI CSF DA and DA metabolite levels, a phenomenon that may modulate susceptibility to DA-mediated oxidative injury.

In vivo transduction of neurons with TAT-UCH-L1 protects brain against controlled cortical impact injury.

Many mechanisms or pathways are involved in secondary post-traumatic brain injury, such as the ubiquitin-proteasome pathway (UPP), axonal degeneration and neuronal cell apoptosis. UCH-L1 is a protein that is expressed in high levels in neurons and may have important roles in the UPP, autophagy and axonal integrity. The current study aims to evaluate the role of UCH-L1 in post-traumatic brain injury (TBI) and its potential therapeutic effects. A novel protein was constructed that fused the protein transduction domain (PTD) of trans-activating transduction (TAT) protein with UCH-L1 (TAT-UCH-L1) in order to promote neuronal transduction. The TAT-UCH-L1 protein was readily detected in brain by immunoblotting and immunohistochemistry after i.p. administration in mice. TBI was induced in mice using the controlled cortical impact (CCI) model. TAT-UCH-L1 treatment significantly attenuated K48-linkage polyubiquitin (polyUb)-protein accumulation in hippocampus after CCI compared to vehicle controls, but had no effects on K65-linkage polyUb-protein. TAT-UCH-L1 treatment also attenuated expression of Beclin-1 and LC3BII after CCI. TAT-UCH-L1-treated mice had significantly increased spared tissue volumes and increased survival of CA3 neurons 21 d after CCI compared to control vehicle-treated mice. Axonal injury, detected by APP immunohistochemistry, was reduced in thalamus 24 h and 21 d after CCI in TAT-UCH-L1-treated mice. These results suggest that TAT-UCH-L1 treatment improves function of the UPP and decreases activation of autophagy after CCI. Furthermore, TAT-UCH-L1 treatment also attenuates axonal injury and increases hippocampal neuronal survival after CCI. Taken together these results suggest that UCH-L1 may play an important role in the pathogenesis of cell death and axonal injury after TBI.

Bromocriptine reduces lipid peroxidation and enhances spatial learning and hippocampal neuron survival in a rodent model of focal brain trauma.

Oxidative stress is a significant contributor to the secondary sequelae of traumatic brain injury (TBI), and may mediate subsequent neurobehavioral deficits and histopathology. The present study examined the neuroprotective effects of bromocriptine (BRO), a dopamine D2 receptor agonist with significant antioxidant properties, on cognition, histopathology, and lipid peroxidation in a rodent model of focal brain trauma. BRO (5 mg/kg) or a comparable volume of vehicle (VEH) was administered intraperitoneally 15 min prior to cortical impact or sham injury. In experiment 1, spatial learning was assessed in an established water maze task on post-surgery days 14-18, followed by quantification of hippocampal cell survival and cortical lesion volume at 4 weeks. In experiment 2, rats were sacrificed 1 hr post-surgery, and malondialdehyde (MDA), the end product of lipid peroxidation, was measured in the frontal cortex, striatum, and substantia nigra using a thiobarbituric acid reactive substances assay. The TBI+BRO group was significantly more adept at locating a hidden platform in the water maze compared to the TBI+VEH group and also exhibited a greater percentage of surviving CA3 hippocampal neurons. TBI increased MDA in all examined regions of the VEH-treated, but not BRO-treated group versus SHAMs. MDA was significantly decreased in both the striatum (4.22 +/- 0.52 versus 5.60 +/- 0.44 nmol per mg/tissue +/- SEM) and substantia nigra (4.18 +/- 0.35 versus 7.76 +/- 2.05) of the TBI+BRO versus TBI+VEH groups, respectively, while only a trend toward decreased MDA was observed in the frontal cortex (5.44 +/- 0.44 versus 6.96 +/- 0.77). These findings suggest that TBI-induced oxidative stress is attenuated by acute BRO treatment, which may, in part, explain the benefit in cognitive and histological outcome.

Traumatic brain injury reduces dopamine transporter protein expression in the rat frontal cortex.

Disturbances in dopamine neurotransmission contribute to frontal lobe dysfunction after traumatic brain injury. The changes in dopamine neurotransmission may be mediated by alterations in the dopamine transporter, which plays a key role in maintaining dopamine homeostasis. To determine whether the dopamine transporter system is altered after traumatic brain injury, dopamine transporter protein was examined bilaterally in the rat frontal cortex by Western blot at 1, 7, and 28 days after controlled cortical impact or sham injury ( = 6/group). Dopamine transporter protein expression was decreased in the injured (ipsilateral) cortex at 7 days and bilaterally at 28 days in injured sham control rats. The decrease in dopamine transporter protein levels may reflect a traumatic brain-injury-induced down-regulation of dopamine transporter and/or a loss of dopaminergic fibers.

Time dependent alterations in dopamine tissue levels and metabolism after experimental traumatic brain injury in rats.

Several studies have demonstrated alterations in the dopamine (DA) system after traumatic brain injury (TBI). The present study investigated the temporal changes in DA tissue levels and metabolism at 1-h or 1, 7, 14, and 28 days after cortical impact or sham injury in rats. DA and DOPAC levels were measured by HPLC in the frontal cortex (FC) and striatum. DA levels were significantly increased at 1h in the contralateral FC and at 1 day in the ipsilateral FC versus respective sham groups. DA and DOPAC levels were significantly increased bilaterally at 1h in the striatum versus sham. These data indicate that TBI induces an early increase in DA and DOPAC, which returns to sham levels over time.

Differential effect of traumatic brain injury on the nuclear factor of activated T Cells C3 and C4 isoforms in the rat hippocampus.

The interaction between the phosphatase calcineurin and transcription factor nuclear factor of activated T cells (NFAT) plays an important role numerous signaling and the regulatory events. Although NFAT is mostly known for its transcription function in the immune system, NFAT also has essential functions even in the central nervous system (CNS). The effects of traumatic brain injury (TBI) on NFAT are currently unknown. To determine if there is an alteration in NFAT after TBI, we examined NFATc3 and c4 levels at 6 h, 1 day, 1 week, 2 weeks and 4 weeks post injury. Rats were anesthetized and surgically prepared for controlled cortical impact (CCI) injury or sham surgery. Semi-quantitative measurements of NFATc3 and c4 in the hippocampal homogenates from injured and sham rats sacrificed at the appropriate time after injury were assessed using Western blot analysis. After TBI insult, in the hippocampus ipsilateral to the injury, NFATc3 expression levels were decreased both in the cytoplasmic and nuclear fractions. However, NFATc4 expression levels were increased in the cytoplasmic fraction but decreased in the nuclear fraction. Double labeling (with NeuN and GFAP) immunohistochemistry revealed that NFATc3 was expressed in subset of astrocytes and NFATc4 was expressed primarily in neurons. These differential responses in NFATc3 and c4 expression after TBI insult may indicate long-term changes in hippocampal excitability and may contribute to behavioral deficits. Further study is warranted to illustrate the role of NFATc3 and c4 in the setting of TBI.

Effect of an inductive hydrogel composed of urinary bladder matrix upon functional recovery following traumatic brain injury.

Traumatic brain injury (TBI) is a major public health problem with no effective clinical treatment. Use of bioactive scaffold materials has been shown to be a promising strategy for tissue regeneration and repair in a number of injury models. Of these scaffold materials, urinary bladder matrix (UBM) derived from porcine bladder tissue, has demonstrated desirable properties for supporting and promoting the growth of neural cells in vitro, suggesting its potential as a scaffold for brain tissue repair in the treatment of TBI. Herein we evaluate the biocompatibility of UBM within brain tissue and the effects of UBM delivery upon functional outcome following TBI. A hydrogel form of UBM was injected into healthy rat brains for 1, 3, and 21 days to examine the tissue response to UBM. Multiple measures of tissue injury, including reactive astrocytosis, microglial activation, and neuron degeneration showed that UBM had no deleterious effects on normal brain. Following TBI, the brains were evaluated histologically and behaviorally between sham-operated controls and UBM- and vehicle-treated groups. Application of UBM reduced lesion volume and attenuated trauma-induced myelin disruption. Importantly, UBM treatment resulted in significant neurobehavioral recovery following TBI as demonstrated by improvements in vestibulomotor function; however, no differences in cognitive recovery were observed between the UBM- and vehicle-treated groups. The present study demonstrated that UBM is not only biocompatible within the brain tissue, but also can exert protective effects upon injured brain.

The dopamine and cAMP regulated phosphoprotein, 32 kDa (DARPP-32) signaling pathway: a novel therapeutic target in traumatic brain injury.

Traumatic brain injury (TBI) causes persistent neurologic deficits. Current therapies, predominantly focused upon cortical and hippocampal cellular survival, have limited benefit on cognitive outcomes. Striatal damage is associated with deficits in executive function, learning, and memory. Dopamine and cAMP regulated phosphoprotein 32 (DARPP-32) is expressed within striatal medium spiny neurons and regulates striatal function. We found that controlled cortical impact injury in rats produces a chronic decrease in DARPP-32 phosphorylation at threonine-34 and an increase in protein phosphatase-1 activity. There is no effect of injury on threonine-75 phosphorylation or on DARPP-32 protein. Amantadine, shown to be efficacious in treating post-TBI cognitive deficits, given daily for two weeks is able to restore the loss of DARPP-32 phosphorylation and reduce protein phosphatase-1 activity. Amantadine also decreases the phosphorylation of threonine-75 consistent with activity as a partial N-methyl-D-aspartate (NMDA) receptor antagonist and partial dopamine agonist. These data demonstrate that targeting the DARPP-32 signaling cascade represents a promising novel therapeutic approach in the treatment of persistent deficits following a TBI.

Regional calcineurin subunit B isoform expression in rat hippocampus following a traumatic brain injury.

Calcineurin subunit isoforms are implicated in long term potentiation, long term depression, and structural plasticity. Calcineurin inhibitors benefit axonal damage, cellular dysfunction, and cognitive outcomes in animal models of traumatic brain injury (TBI). Distribution of the catalytic calcineurin A subunit is altered and calcineurin activity increased following fluid percussion injury. Alterations in calcineurin subunit A isoform distribution within the hippocampus also occur post controlled cortical impact (CCI) demonstrating a reduction in catalytic subunit distribution in CA1-2 dendritic fields. Furthermore the effect of TBI on the regulatory subunit, calcineurin B, is unknown. Understanding the role of both subunits is necessary to effectively target alterations in calcineurin signaling as current calcineurin inhibitors, such as cyclosporin A and FK-506, rely upon binding sites on both subunits for complete inhibition. The effect of moderate CCI on the expression and distribution of calcineurin B isoforms within the hippocampus was examined at 2h and 2weeks post injury. Calcineurin B isoforms showed increased expression throughout the CA1 and CA2 while there was a decrease in expression within the ipsilateral dentate gyrus. Alterations in CnB isoform expression within the CA1, CA1-2, and dentate gyrus have significant implications for persistent hippocampal dysfunction following TBI. Regional changes in regulatory subunit expression may alter the effect of calcineurin inhibitors regionally following a traumatic brain injury.

Expression of protein phosphatase 2B (calcineurin) subunit A isoforms in rat hippocampus after traumatic brain injury.

Calcineurin (CaN) is a calcium/calmodulin-dependent phosphatase directly activated by calcium as a result of neuronal activation that is important for neuronal function. CaN subunit isoforms are implicated in long-term potentiation (LTP), long-term depression (LTD), and structural plasticity. CaN inhibitors are also beneficial to cognitive outcomes in animal models of traumatic brain injury (TBI). There are known changes in the CaN A (CnA) subunit following fluid percussion injury (FPI). The CnA subunit has two isoforms: CnAalpha and CnAbeta. The effect of moderate controlled cortical impact (CCI) on distribution of CnA isoforms was examined at 2 h and 2 weeks post-injury. CnA distribution was assayed by immunohistochemistry and graded for non-parametric analysis. Acutely CnA isoforms showed reduced immunoreactivity in stratum radiatum processes of the ipsilateral CA1 and CA1-2. There was also a significant alteration in the immunoreactivity of both CnA isoforms in the ipsilateral dentate gyrus, predominantly within the hidden blade. Alterations in CnA isoform regional distribution within the CA1, CA1-2, and dentate gyrus may have significant implications for persistent hippocampal dysfunction following TBI, including dysfunction in hippocampal plasticity. Understanding alterations in CnA isoform distribution may help improve the targeting of current therapeutic interventions and/or the development of new treatments for TBI.

Synaptosomal dopamine uptake in rat striatum following controlled cortical impact.

Functional deficits following traumatic brain injury (TBI) are associated with alterations in markers of dopaminergic neurotransmission. To assess the effects of TBI on the expression and functional integrity of dopamine transporters, we measured transporter protein levels and investigated synaptosomal dopamine uptake in the rat striatum. Two or four weeks after lateral controlled cortical impact or sham injury, Western blotting revealed a decrease in transporter protein in the ipsilateral striatum of injured rats relative to shams (P < 0.05). However, no significant difference in synaptosomal uptake (K(m), V(max)) was found between injured and sham-injured animals. Our data suggest that striatal dopamine transporters are capable of normal function at 2 weeks and 4 weeks after injury. However, it is unclear whether neurons in the injured striatum can properly regulate the activity of dopamine transporters in vivo.

Acute etomidate treatment reduces cognitive deficits and histopathology in rats with traumatic brain injury.

OBJECTIVE: To test the hypothesis that etomidate treatment improves functional, cognitive, and histologic outcome after experimental traumatic brain injury. DESIGN: Controlled animal study. SETTING: University research laboratory. SUBJECTS: Male Sprague-Dawley rats. INTERVENTIONS: Traumatic brain injury was produced by controlled cortical impact injury (4 m/sec, 2.6 mm of tissue deformation). Etomidate (2 mg/kg) was administered intravenously immediately before injury (n = 13) or 5 mins after injury (n = 12). Additional rats received saline treatment 5 mins after injury (n = 12) or served as sham controls (n = 10). MEASUREMENTS AND MAIN RESULTS: Rats were evaluated on beam balance and beam walk tasks on postoperative days 1-5 and then trained in the Morris water maze on postoperative days 14-18. On day 28, the rats were killed, and hippocampal CA1 and CA3 neuron counts and cortical lesion volume were measured in histologic brain sections. Preinjury etomidate attenuated beam balance deficits, water maze deficits, hippocampal CA3 neuronal loss, and cortical tissue loss but did not attenuate beam walk deficits or hippocampal CA1 neuronal loss. Postinjury etomidate attenuated water maze deficits, but it did not affect any other outcome measure. CONCLUSIONS: Administration of etomidate both before and after injury attenuates secondary injury resulting from traumatic brain injury, but the effect is more pronounced with pretreatment. The ineffectiveness of postinjury etomidate on motor and histologic tasks suggests a brief therapeutic treatment window in rats. However, the treatment window in humans is unknown. Lastly, postinjury etomidate did not exacerbate neurologic or histologic outcome.

Amantadine improves water maze performance without affecting motor behavior following traumatic brain injury in rats.

Amantadine, a dopamine agonist, is reported to have beneficial effects on the neurobehavioral sequelae of clinical brain injury. However, there are currently no published laboratory reports on its use in the assessment of functional or histopathological outcome following experimental traumatic brain injury (TBI). To this end, we examined the effects of daily amantadine treatment on functional recovery (motor and Morris water maze performance) and hippocampal neuronal survival following controlled cortical impact (CCI) injury (4 meters/sec, 2.7 mm tissue deformation). Male Sprague-Dawley rats were pretrained on motor performance tasks (beam balance and beam walking) one day prior to injury and tested on post-operative days 1-5. Additionally, all subjects were trained on the Morris water maze on post-operative days 14-18. Beginning one day after CCI injury or sham surgery, animals were injected once daily for 18 days with either amantadine (10 mg/kg, i.p.) or saline. The amantadine treatment regimen was ineffective in promoting motor recovery and increasing survival of hippocampal neurons in both the CA1 and CA3 regions following TBI, but did show improved swim latencies during the five days of water maze testing (Day 14 vs. Day 18, p < 0.01) when compared to saline controls. Mean (+/- SE) swim latencies on Day 18 were 15.12 +/- 2.8, 13.25 +/- 4.18, 70.83 +/- 11.1, and 38.5 +/- 3.55 sec for the sham/saline, sham/amantadine, injured/saline, and injured/amantadine treatment groups, respectively. Thus, while the daily administration of amantadine exhibited a neutral effect on motor behavior, it produced a modest attenuation of water maze performance deficits. This latter finding is consistent with published clinical data suggesting a beneficial effect on functional outcome with amantadine therapy.