Neurobehavioral protection by the neuronal calcium channel blocker ziconotide in a model of traumatic diffuse brain injury in rats

A Modern Approach to the Treatment of Traumatic Brain Injury

Background: Traumatic brain injury manifests itself in various forms, ranging from mild impairment of consciousness to severe coma and death. Traumatic brain injury remains one of the leading causes of morbidity and mortality. Currently, there is no therapy to reverse the effects associated with traumatic brain injury. New neuroprotective treatments for severe traumatic brain injury have not achieved significant clinical success. Methods: A literature review was performed to summarize the recent interdisciplinary findings on management of traumatic brain injury from both clinical and experimental perspective. Results: In the present review, we discuss the concepts of traditional and new approaches to treatment of traumatic brain injury. The recent development of different drug delivery approaches to the central nervous system is also discussed. Conclusions: The management of traumatic brain injury could be aimed either at the pathological mechanisms initiating the secondary brain injury or alleviating the symptoms accompanying the injury. In many cases, however, the treatment should be complex and include a variety of medical interventions and combination therapy.

Omega-conotoxin MVIIA reduces neuropathic pain after spinal cord injury by inhibiting N-type voltage-dependent calcium channels on spinal dorsal horn

Spinal cord injury (SCI) leads to the development of neuropathic pain. Although a multitude of pathological processes contribute to SCI-induced pain, excessive intracellular calcium accumulation and voltage-gated calcium-channel upregulation play critical roles in SCI-induced pain. However, the role of calcium-channel blockers in SCI-induced pain is unknown. Omega-conotoxin MVIIA (MVIIA) is a calcium-channel blocker that selectively inhibits N-type voltage-dependent calcium channels and demonstrates neuroprotective effects. Therefore, we investigated spinal analgesic actions and cellular mechanisms underlying the analgesic effects of MVIIA in SCI. We used SCI-induced pain model rats and conducted behavioral tests, immunohistochemical analyses, and electrophysiological experiments (in vitro whole-cell patch-clamp recording and in vivo extracellular recording). A behavior study suggested intrathecal MVIIA administration in the acute phase after SCI induced analgesia for mechanical allodynia. Immunohistochemical experiments and in vivo extracellular recordings suggested that MVIIA induces analgesia in SCI-induced pain by directly inhibiting neuronal activity in the superficial spinal dorsal horn. In vitro whole-cell patch-clamp recording showed that MVIIA inhibits presynaptic N-type voltage-dependent calcium channels expressed on primary afferent Aδ-and C-fiber terminals and suppresses the presynaptic glutamate release from substantia gelatinosa in the spinal dorsal horn. In conclusion, MVIIA administration in the acute phase after SCI may induce analgesia in SCI-induced pain by inhibiting N-type voltage-dependent calcium channels on Aδ-and C-fiber terminals in the spinal dorsal horn, resulting in decreased neuronal excitability enhanced by SCI-induced pain.

Intracerebroventricular administration of N-type calcium channel blocker ziconotide displays anticonvulsant, anxiolytic, and sedative effects in rats: A preclinical and pilot study

OBJECTIVE

Ziconotide (ω-conotoxin MVIIA peptide) is a novel analgesic agent acting on voltage-gated calcium channels and is administered intrathecally for neuropathic pain. While antiepileptic activities of other types of calcium channel blockers (T- or L-type) are well established, there is no information regarding the effect of ziconotide as an N-type calcium channel antagonist in pentylenetetrazol-induced seizures or its anxiolytic and sedative activities. The present study is the first to report on these effects.

METHODS

To evaluate the anticonvulsant activity of ziconotide in the pentylenetetrazol (60 mg/kg) seizure model, ziconotide was administered intracerebroventricular (i.c.v.) as a single dose (1 μg/rat) or repeatedly (chronic administration: 0.1, 0.3, or 1 μg/rat once a day for seven days). The anxiolytic and sedative actions of ziconotide were evaluated with the elevated plus maze, light/dark (LD) box, and pentobarbital-induced sleep tests. Immediately after behavioral testing, the amygdala was completely removed bilaterally to determine corticosterone levels by immunoassay.

RESULTS

In all dosing regimens, ziconotide significantly decreased the seizure frequency and also delayed the latency period compared with control. Chronic administration affected the percentage of mortality protection, while a single dose of ziconotide did not. In behavioral tests, ziconotide significantly increased both the number of entries and the percentage of time spent in the open arms of the elevated plus maze. Furthermore, ziconotide significantly increased the latency period and the number of entries into the light compartment during the LD box examination. Chronic administration of ziconotide significantly reduced the latency to sleep and increased sleeping time, whereas these parameters were not affected by a single dose. Additionally, amygdala corticosterone levels were significantly decreased in rats treated with ziconotide compared with control.

CONCLUSION

Ziconotide displays beneficial neurobehavioral effects in a model of epilepsy with anxiety as its comorbid event. It seems that at least one of the mechanisms involved in these effects is associated with a decrease in brain corticosterone levels. The main advantage of ziconotide over benzodiazepines (routine anxiolytic and sedative drugs) is that it does not cause tolerance, dependency, and addiction. Therefore, more than ever, it is necessary to improve the convenience of drug delivery protocols and attenuate the adverse effects associated with ziconotide-based therapies.

Antidepressant-like and memory-enhancing effects of the N-type calcium channel blocker ziconotide in rats

The lack of oral or injectable formulations of ziconotide (ω-conotoxin peptide), a novel analgesic agent, limits research on potential neurobehavioral protective properties of this substance, including antidepressant-like effects. Here we expose rats to a stress paradigm that induces depression and memory impairment to assess the effects of ziconotide treatment. Ziconotide was administered intracerebroventricular (i.c.v.) to rats undergoing stereotaxic surgery at a single dose (1 μg/rat) or in repeated long-term applications (dosage groups: 0.1, 0.3, and 1 μg/rat). The antidepressant activity and memory-enhancing effects of ziconotide were examined via the forced swimming test, the Morris water maze test, and the passive avoidance learning test. Behavioral results showed that long-term i.c.v. ziconotide administration significantly decreased the immobility time and delayed the latency period to immobility in a dose-dependent manner compared to controls. In the passive avoidance learning test, the latency period increased, and in the Morris water maze test, the platform location latency time decreased. A single dose of ziconotide (1 μg/rat) did not show a significant effect on memory function or depression parameters during the same tests. Animals were sacrificed immediately after behavioral testing, and both hippocampi were removed and prepared for BDNF evaluation. Hippocampal BDNF levels were significantly increased in rats receiving long-term i.c.v. ziconotide compared to controls. Our results suggest that long-term consumption of ziconotide may attenuate the severity of depression-like behavior and could be useful for preventing memory impairments in various learning models by elevating BDNF levels.

Traumatic Brain Injury and Blood-Brain Barrier (BBB): Underlying Pathophysiological Mechanisms and the Influence of Cigarette Smoking as a Premorbid Condition

Traumatic brain injury (TBI) is among the most pressing global health issues and prevalent causes of cerebrovascular and neurological disorders all over the world. In addition to the brain injury, TBI may also alter the systemic immune response. Thus, TBI patients become vulnerable to infections, have worse neurological outcomes, and exhibit a higher rate of mortality and morbidity. It is well established that brain injury leads to impairments of the blood-brain barrier (BBB) integrity and function, contributing to the loss of neural tissue and affecting the response to neuroprotective drugs. Thus, stabilization/protection of the BBB after TBI could be a promising strategy to limit neuronal inflammation, secondary brain damage, and acute neurodegeneration. Herein, we present a review highlighting the significant post-traumatic effects of TBI on the cerebrovascular system. These include the loss of BBB integrity and selective permeability, impact on BBB transport mechanisms, post-traumatic cerebral edema formation, and significant pathophysiological factors that may further exacerbate post-traumatic BBB dysfunctions. Furthermore, we discuss the post-traumatic impacts of chronic smoking, which has been recently shown to act as a premorbid condition that impairs post-TBI recovery. Indeed, understanding the underlying molecular mechanisms associated with TBI damage is essential to better understand the pathogenesis and progression of post-traumatic secondary brain injury and the development of targeted treatments to improve outcomes and speed up the recovery process. Therapies aimed at restoring/protecting the BBB may reduce the post-traumatic burden of TBI by minimizing the impairment of brain homeostasis and help to restore an optimal microenvironment to support neuronal repair.

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 search of antiepileptogenic treatments for post-traumatic epilepsy

Post-traumatic epilepsy (PTE) is diagnosed in 20% of individuals with acquired epilepsy, and can impact significantly the quality of life due to the seizures and other functional or cognitive and behavioral outcomes of the traumatic brain injury (TBI) and PTE. There is no available antiepileptogenic or disease modifying treatment for PTE. Animal models of TBI and PTE have been developed, offering useful insights on the value of inflammatory, neurodegenerative pathways, hemorrhages and iron accumulation, calcium channels and other target pathways that could be used for treatment development. Most of the existing preclinical studies test efficacy towards pathologies of functional recovery after TBI, while a few studies are emerging testing the effects towards induced or spontaneous seizures. Here we review the existing preclinical trials testing new candidate treatments for TBI sequelae and PTE, and discuss future directions for efforts aiming at developing antiepileptogenic and disease-modifying treatments.

Conotoxin MVIIA improves cell viability and antioxidant system after spinal cord injury in rats

This study evaluates whether intrathecal MVIIA injection after spinal cord injury (SCI) elicits neuroprotective effects. The test rats were randomly distributed into six groups— sham, placebo, MVIIA 2.5 μM, MVIIA 5 μM, MVIIA 10 μM, and MVIIA 20 μM—and were administered the treatment four hours after SCI. After the optimal MVIIA dose (MVIIA 10 μM) was defined, the best time for application, one or four hours, was analyzed. Locomotor hind limb function and side effects were assessed. Forty-eight hours after the injury and immediately after euthanasia, spinal cord segments were removed from the test rats. Cell viability, reactive oxygen species, lipid peroxidation, and glutamate release were investigated. To examine the MVIIA mechanism of action, the gene expressions of pro-apoptotic (Bax, nNOS, and caspase-3, -8, -9, -12) and anti-apoptotic (Bcl-xl) factors in the spinal cord tissue samples were determined by real-time PCR, and the activities of antioxidant enzymes were also investigated. Application of intrathecal MVIIA 10 μM four hours after SCI prompted a neuroprotective effect: neuronal death decreased (22.46%), oxidative stress diminished, pro-apoptotic factors (Bax, nNOS, and caspase-3, -8) were expressed to a lesser extent, and mitochondrial viability as well as anti-apoptotic factor (Bcl-xl) expression increased. These results suggested that MVIIA provided neuroprotection through antioxidant effects. Indeed, superoxide dismutase (188.41%), and glutathione peroxidase (199.96%), reductase (193.86%), and transferase (175.93%) expressions increased. Therefore, intrathecal MVIIA (MVIIA 10 μM, 4 h) application has neuroprotective potential, and the possible mechanisms are related to antioxidant agent modulation and to intrinsic and extrinsic apoptotic pathways.

Diltiazem Promotes Regenerative Axon Growth

Axotomy results in permanent loss of function after brain and spinal cord injuries due to the minimal regenerative propensity of the adult central nervous system (CNS). To identify pharmacological enhancers of axon regeneration, 960 compounds were screened for cortical neuron axonal regrowth using an in vitro cortical scrape assay. Diltiazem, verapamil, and bromopride were discovered to facilitate axon regeneration in rat cortical cultures, in the presence of chondroitin sulfate proteoglycans (CSPGs). Diltiazem, an L-type calcium channel blocker (L-CCB), also promotes axon outgrowth in adult primary mouse dorsal root ganglion (DRG) and induced human sensory (iSensory) neurons.

Peptide Pharmacological Approaches to Treating Traumatic Brain Injury: a Case for Arginine-Rich Peptides

Traumatic brain injury (TBI) has a devastating effect on victims and their families, and has profound negative societal and economic impacts, a situation that is further compounded by the lack of effective treatments to minimise injury after TBI. The current strategy for managing TBI is partly through preventative measures and partly through surgical and rehabilitative interventions. Secondary brain damage remains the principal focus for the development of a neuroprotective therapeutic. However, the complexity of TBI pathophysiology has meant that single-action pharmacological agents have been largely unsuccessful in combatting the associated brain injury cascades, while combination therapies to date have proved equally ineffective. Peptides have recently emerged as promising lead agents for the treatment of TBI, especially those rich in the cationic amino acid, arginine. Having been shown to lessen the impact of ischaemic stroke in animal models, there are reasonable grounds to believe that arginine-rich peptides may have neuroprotective therapeutic potential in TBI. Here, we review a range of peptides previously examined as therapeutic agents for TBI. In particular, we focus on cationic arginine-rich peptides -- a new class of agents that growing evidence suggests acts through multiple neuroprotective mechanisms.

Amlodipine treatment of hypertension associates with a decreased dementia risk

Hypertension has been shown to be a risk factor for development of dementia. However, medical treatment of hypertension failed to reduce consistently the risk of dementia. Experimental study pointed to the possibility of difference between different calcium channel blockers (CCB) in their neuro-protective effect. The aim of our study was to evaluate the risk of dementia during treatment of hypertension with different CCBs. This is a retrospective cohort study based on electronic database of a large public health care organization. Study period was 11 years and it included patients aged 40-75 years old, having diagnosis of hypertension without diagnosis of dementia at the starting point, treated with either single specific CCB (study group) or with other than CCBs antihypertensive medications (control group) for at least 30 months during the study period. A total of 15,664 patients that satisfied these criteria were identified: 3,884 were treated with amlodipine, 2,062 were treated with nifedipine, 609 were treated with lercanidipine, and 9,109 never received CCBs. Dementia developed in 765 (4.9%) patients. Adjusted hazard ratio (HR) for dementia in patients treated with amlodipine, nifedipine, and lercanidipine was 0.60 (p < 0.001), 0.89 (NS), and 0.90 (NS). Decreased adjusted HR of dementia with amlodipine was demonstrated in the patients aged 60 or more (HR 0.61 [0.49-0.77], p < 0.001), but not in the patients aged less than 60 years old. This study shows that amlodipine therapy may be associated with a decreased dementia risk in hypertensive individuals older than 60 years, compared to those treated without CCBs.

Animal models of chronic pain: Advances and challenges for clinical translation

Chronic pain is a global problem that has reached epidemic proportions. An estimated 20% of adults suffer from pain, and another 10% are diagnosed with chronic pain each year (Goldberg and McGee, ). Despite the high prevalence of chronic pain (an estimated 1.5 billion people are afflicted worldwide), much remains to be understood about the underlying causes of this condition, and there is an urgent requirement for better pain therapies. The discovery of novel targets and the development of better analgesics rely on an assortment of preclinical animal models; however, there are major challenges to translating discoveries made in animal models to realized pain therapies in humans. This review discusses common animal models used to recapitulate clinical chronic pain conditions (such as neuropathic, inflammatory, and visceral pain) and the methods for assessing the sensory and affective components of pain in animals. We also discuss the advantages and limitations of modeling chronic pain in animals as well as highlighting strategies for improving the predictive validity of preclinical pain studies. © 2016 Wiley Periodicals, Inc.

Gramine Derivatives Targeting Ca(2+) Channels and Ser/Thr Phosphatases: A New Dual Strategy for the Treatment of Neurodegenerative Diseases

We describe the synthesis of gramine derivatives and their pharmacological evaluation as multipotent drugs for the treatment of Alzheimer's disease. An innovative multitarget approach is presented, targeting both voltage-gated Ca(2+) channels, classically studied for neurodegenerative diseases, and Ser/Thr phosphatases, which have been marginally aimed, even despite their key role in protein τ dephosphorylation. Twenty-five compounds were synthesized, and mostly their neuroprotective profile exceeded that offered by the head compound gramine. In general, these compounds reduced the entry of Ca(2+) through VGCC, as measured by Fluo-4/AM and patch clamp techniques, and protected in Ca(2+) overload-induced models of neurotoxicity, like glutamate or veratridine exposures. Furthermore, we hypothesize that these compounds decrease τ hyperphosphorylation based on the maintenance of the Ser/Thr phosphatase activity and their neuroprotection against the damage caused by okadaic acid. Hence, we propose this multitarget approach as a new and promising strategy for the treatment of neurodegenerative diseases.

Calcium channel blockers and dementia

Degenerative dementia is mainly caused by Alzheimer's disease and/or cerebrovascular abnormalities. Disturbance of the intracellular calcium homeostasis is central to the pathophysiology of neurodegeneration. In Alzheimer's disease, enhanced calcium load may be brought about by extracellular accumulation of amyloid-β. Recent studies suggest that soluble forms facilitate influx through calcium-conducting ion channels in the plasma membrane, leading to excitotoxic neurodegeneration. Calcium channel blockade attenuates amyloid-β-induced neuronal decline in vitro and is neuroprotective in animal models. Vascular dementia, on the other hand, is caused by cerebral hypoperfusion and may benefit from calcium channel blockade due to relaxation of the cerebral vasculature. Several calcium channel blockers have been tested in clinical trials of dementia and the outcome is heterogeneous. Nimodipine as well as nilvadipine prevent cognitive decline in some trials, whereas other calcium channel blockers failed. In trials with a positive outcome, BP reduction did not seem to play a role in preventing dementia, indicating a direct protecting effect on neurons. An optimization of calcium channel blockers for the treatment of dementia may involve an increase of selectivity for presynaptic calcium channels and an improvement of the affinity to the inactivated state. Novel low molecular weight compounds suitable for proof-of-concept studies are now available.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Voltage-gated calcium channel antagonists and traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of death and disability in the United States. Despite more than 30 years of research, no pharmacological agents have been identified that improve neurological function following TBI. However, several lines of research described in this review provide support for further development of voltage gated calcium channel (VGCC) antagonists as potential therapeutic agents. Following TBI, neurons and astrocytes experience a rapid and sometimes enduring increase in intracellular calcium ([Ca²⁺]_i). These fluxes in [Ca²⁺]_i drive not only apoptotic and necrotic cell death, but also can lead to long-term cell dysfunction in surviving cells. In a limited number of in vitro experiments, both L-type and N-type VGCC antagonists successfully reduced calcium loads as well as neuronal and astrocytic cell death following mechanical injury. In rodent models of TBI, administration of VGCC antagonists reduced cell death and improved cognitive function. It is clear that there is a critical need to find effective therapeutics and rational drug delivery strategies for the management and treatment of TBI, and we believe that further investigation of VGCC antagonists should be pursued before ruling out the possibility of successful translation to the clinic.

A review of neuroprotection pharmacology and therapies in patients with acute traumatic brain injury

Traumatic brain injury (TBI) affects 1.6 million Americans annually. The injury severity impacts the overall outcome and likelihood for survival. Current treatment of acute TBI includes surgical intervention and supportive care therapies. Treatment of elevated intracranial pressure and optimizing cerebral perfusion are cornerstones of current therapy. These approaches do not directly address the secondary neurological sequelae that lead to continued brain injury after TBI. Depending on injury severity, a complex cascade of processes are activated and generate continued endogenous changes affecting cellular systems and overall outcome from the initial insult to the brain. Homeostatic cellular processes governing calcium influx, mitochondrial function, membrane stability, redox balance, blood flow and cytoskeletal structure often become dysfunctional after TBI. Interruption of this cascade has been the target of numerous pharmacotherapeutic agents investigated over the last two decades. Many agents such as selfotel, pegorgotein (PEG-SOD), magnesium, deltibant and dexanabinol were ineffective in clinical trials. While progesterone and ciclosporin have shown promise in phase II studies, success in larger phase III, randomized, multicentre, clinical trials is pending. Consequently, no neuroprotective treatment options currently exist that improve neurological outcome after TBI. Investigations to date have extended understanding of the injury mechanisms and sites for intervention. Examination of novel strategies addressing both pathological and pharmacological factors affecting outcome, employing novel trial design methods and utilizing biomarkers validated to be reflective of the prognosis for TBI will facilitate progress in overcoming the obstacles identified from previous clinical trials.

In vitro models of traumatic brain injury

In vitro models of traumatic brain injury (TBI) are helping elucidate the pathobiological mechanisms responsible for dysfunction and delayed cell death after mechanical stimulation of the brain. Researchers have identified compounds that have the potential to break the chain of molecular events set in motion by traumatic injury. Ultimately, the utility of in vitro models in identifying novel therapeutics will be determined by how closely the in vitro cascades recapitulate the sequence of cellular events that play out in vivo after TBI. Herein, the major in vitro models are reviewed, and a discussion of the physical injury mechanisms and culture preparations is employed. A comparison between the efficacy of compounds tested in vitro and in vivo is presented as a critical evaluation of the fidelity of in vitro models to the complex pathobiology that is TBI. We conclude that in vitro models were greater than 88% predictive of in vivo results.

Impact of pharmacological treatments on outcome in adult rodents after traumatic brain injury: a meta-analysis

Pharmacological treatments have been widely investigated in pre-clinical animal trials to evaluate their usefulness in reducing cognitive, behavioural and motor problems after traumatic brain injury (TBI). However, the relative efficacy of these agents has yet to be evaluated, making it difficult to assess the strength of evidence for their use in a clinical population. A meta-analytic review of research (1980-2009) was therefore conducted to examine the impact of pharmacological treatments administered to adult male rodents after experimental TBI on cognitive, behavioural, and motor outcome. The PubMed and PsycInfo databases were searched using 35 terms. Weighted Cohen's d effect sizes, percent overlap, Fail-Safe N statistics and confidence intervals were calculated for each treatment. In total, 91 treatments were evaluated in 223 pre-clinical trials, comprising 5988 rodents. Treatments that were investigated by multiple studies and showed large and significant treatment effects were of greatest interest. Of the 16 treatments that were efficacious, six improved cognition, 10 improved motor function and no treatment improved behaviour (depression/anxiety, aggression, zoosocial behaviour). Treatment benefits were found across a range of TBI models. Drug dosage and treatment interval impacted on treatment effects.

Modeling the pathobiology of repetitive traumatic brain injury in immortalized neuronal cell lines

Repetitive mild traumatic brain injury (mTBI) represents a major public health problem. Many individuals who suffer repetitive mTBIs suffer from Post-Concussion Syndrome, a constellation of neuropsychiatric symptoms that includes depression, anxiety, and problems with memory and other cognitive processes. Significantly, Post-Concussion Syndrome is resistant to existing therapeutic strategies. To provide better treatment options for this patient population, the underlying pathophysiology of repetitive mTBI must be understood. A first step in this process is the establishment of an in vitro model system that recapitulates the biological changes that occur in the brains of repetitively injured humans. The availability of a model with immortalized cell lines would remove the considerable barriers of time, expense, and difficulties with genetic manipulation that exist with the use of primary neuronal cultures. Here we report the development and functional characterization of an in vitro laboratory model of repetitive TBI using immortalized neuronal cell lines. These results indicate that the moderate, repetitive injury reduces viability, numbers and lengths of neurites, and that the neuronal loss mechanism includes caspase activation.

Aroclor 1254, a developmental neurotoxicant, alters energy metabolism- and intracellular signaling-associated protein networks in rat cerebellum and hippocampus

The vast literature on the mode of action of polychlorinated biphenyls (PCBs) indicates that PCBs are a unique model for understanding the mechanisms of toxicity of environmental mixtures of persistent chemicals. PCBs have been shown to adversely affect psychomotor function and learning and memory in humans. Although the molecular mechanisms for PCB effects are unclear, several studies indicate that the disruption of Ca(2+)-mediated signal transduction plays significant roles in PCB-induced developmental neurotoxicity. Culminating events in signal transduction pathways include the regulation of gene and protein expression, which affects the growth and function of the nervous system. Our previous studies showed changes in gene expression related to signal transduction and neuronal growth. In this study, protein expression following developmental exposure to PCB is examined. Pregnant rats (Long Evans) were dosed with 0.0 or 6.0mg/kg/day of Aroclor-1254 from gestation day 6 through postnatal day (PND) 21, and the cerebellum and hippocampus from PND14 animals were analyzed to determine Aroclor 1254-induced differential protein expression. Two proteins were found to be differentially expressed in the cerebellum following PCB exposure while 18 proteins were differentially expressed in the hippocampus. These proteins are related to energy metabolism in mitochondria (ATP synthase, sub unit β (ATP5B), creatine kinase, and malate dehydrogenase), calcium signaling (voltage-dependent anion-selective channel protein 1 (VDAC1) and ryanodine receptor type II (RyR2)), and growth of the nervous system (dihydropyrimidinase-related protein 4 (DPYSL4), valosin-containing protein (VCP)). Results suggest that Aroclor 1254-like persistent chemicals may alter energy metabolism and intracellular signaling, which might result in developmental neurotoxicity.

N-type calcium channel in the pathogenesis of experimental autoimmune encephalomyelitis

One of the family of voltage-gated calcium channels (VGCC), the N-type Ca(2+) channel, is located predominantly in neurons and is associated with a variety of neuronal responses, including neurodegeneration. A precise mechanism for how the N-type Ca(2+) channel plays a role in neurodegenerative disease, however, is unknown. In this study, we immunized N-type Ca(2+) channel α(1B)-deficient (α(1B)(-/-)) mice and their wild type (WT) littermates with myelin oligodendrocyte glycoprotein 35-55 and analyzed the progression of experimental autoimmune encephalomyelitis (EAE). The neurological symptoms of EAE in the α(1B)(-/-) mice were less severe than in the WT mice. In conjunction with these results, sections of the spinal cord (SC) from α(1B)(-/-) mice revealed a reduction in both leukocytic infiltration and demyelination compared with WT mice. No differences were observed in the delayed-type hypersensitivity response, spleen cell proliferation, or cytokine production from splenocytes between the two genotypes. On the other hand, Western blot array analysis and RT-PCR revealed that a typical increase in the expression of MCP-1 in the SC showed a good correlation with the infiltration of leukocytes into the SC. Likewise, immunohistochemical analysis showed that the predominant source of MCP-1 was activated microglia. The cytokine-induced production of MCP-1 in primary cultured microglia from WT mice was significantly higher than that from α(1B)(-/-) mice and was significantly inhibited by a selective N-type Ca(2+) channel antagonist, ω-conotoxin GVIA or a withdrawal of extracellular Ca(2+). These results suggest that the N-type Ca(2+) channel is involved in the pathogenesis of EAE at least in part by regulating MCP-1 production by microglia.

Traumatic brain injury and the effects of diazepam, diltiazem, and MK-801 on GABA-A receptor subunit expression in rat hippocampus

Background

Excitatory amino acid release and subsequent biochemical cascades following traumatic brain injury (TBI) have been well documented, especially glutamate-related excitotoxicity. The effects of TBI on the essential functions of inhibitory GABA-A receptors, however, are poorly understood.

Methods

We used Western blot procedures to test whether in vivo TBI in rat altered the protein expression of hippocampal GABA-A receptor subunits α1, α2, α3, α5, β3, and γ2 at 3 h, 6 h, 24 h, and 7 days post-injuy. We then used pre-injury injections of MK-801 to block calcium influx through the NMDA receptor, diltiazem to block L-type voltage-gated calcium influx, or diazepam to enhance chloride conductance, and re-examined the protein expressions of α1, α2, α3, and γ2, all of which were altered by TBI in the first study and all of which are important constituents in benzodiazepine-sensitive GABA-A receptors.

Results

Western blot analysis revealed no injury-induced alterations in protein expression for GABA-A receptor α2 or α5 subunits at any time point post-injury. Significant time-dependent changes in α1, α3, β3, and γ2 protein expression. The pattern of alterations to GABA-A subunits was nearly identical after diltiazem and diazepam treatment, and MK-801 normalized expression of all subunits 24 hours post-TBI.

Conclusions

These studies are the first to demonstrate that GABA-A receptor subunit expression is altered by TBI in vivo, and these alterations may be driven by calcium-mediated cascades in hippocampal neurons. Changes in GABA-A receptors in the hippocampus after TBI may have far-reaching consequences considering their essential importance in maintaining inhibitory balance and their extensive impact on neuronal function.

Neuroprotective effects of selective N-type VGCC blockade on stretch-injury-induced calcium dynamics in cortical neurons

Acute elevation in intracellular calcium ([Ca(2+)](i)) following traumatic brain injury (TBI) can trigger cellular mechanisms leading to neuronal dysfunction and death. The mechanisms underlying these processes are not completely understood, but calcium influx through N-type voltage-gated calcium channels (VGCCs) appears to play a central role. The present study examined the time course of [Ca(2+)](i) flux, glutamate release, and loss of cell viability following injury using an in vitro neuronal-glial cortical cell-culture model of TBI. The effects of N-channel blockade with SNX-185 (e.g. omega-conotoxin TVIA) before or after injury were also examined. Neuronal injury produced a transient elevation in [Ca(2+)](i), increased glutamate release, and resulted in neuronal and glial death. SNX-185 administered before or immediately after cell injury reduced glutamate release and increased the survival of neurons and astrocytes, whereas delayed treatment did not improve cell survival but significantly facilitated the return of [Ca(2+)](i) to baseline levels. The new findings that N-type VGCCs are critically involved in injury-induced glutamate release and recovery of [Ca(2+)](i) argue for continued investigation of this treatment strategy for the clinical management of TBI. In particular, SNX-185 may represent an effective class of drugs that can significantly protect injured neurons from the secondary insults that commonly occur after TBI.

A novel PARP inhibitor L-2286 in a rat model of impact acceleration head injury: an immunohistochemical and behavioral study

We examined the neuro/axono-protective potential of a novel poly (ADP-ribose) polymerase (PARP) inhibitor L-2286 in a rat impact acceleration brain injury model. Male Wistar rats (n = 70) weighing 300–350 grams were used to determine the most effective intracerebroventricular (i.c.v.) dose of L-2286 administered 30 min after injury, and to test the neuroprotective effect at two time points (immediately, and 30 min after injury). The neuroprotective effect of L-2286 was tested using immunohistochemical (amyloid precursor protein and mid-sized mouse anti-neurofilament clone RMO-14.9 antibody) and behavioral tests (beam-balance, open-field and elevated plus maze). At both time-points, a 100 μg/rat dose of i.c.v. L-2286 significantly (p < 0.05) reduced the density of damaged axons in the corticospinal tract and medial longitudinal fascicle compared to controls. In the behavioral tests, treatment 30 min post-injury improved motor function, while the level of anxiety was reduced in both treatment protocols.

Changes of mGluR4 and the effects of its specific agonist L-AP4 in a rodent model of diffuse brain injury

OBJECTIVE

Excessive release of glutamate from nerve terminals following diffuse brain injury (DBI) is thought to contribute to neuronal calcium overload leading to calcium-mediated cell damage. Metabotropic glutamate receptor subtype 4 (mGluR4) is regarded as one of the neuroprotective receptors in mammalian brains. Therefore, the mGluR4 specific agonists might exert neuroprotective effects after DBI. The focus of this study is to examine the changes of expression of mGluR4 after DBI and the role of its specific agonist L-AP4 in vivo.

METHODS

One hundred and sixty-one male SD rats were randomized into two groups. Group A included normal control, sham-operated control and DBI group. DBI was produced by Marmarou's diffuse head injury model. The mRNA expression of mGluR4 was detected by hybridization in situ. Group B included DBI alone, DBI treated with normal saline and DBI treated with L-AP4. All DBI rats were trained in a series of performance tests, following which they were subjected to DBI. At 1 and 12 h, animals were injected intracerebroventricularly with L-AP4 (100 mM, 10 microl) or normal saline, respectively. The rats were tested for motor and cognitive performance at 1, 3, 7, 14 days post-injury and the damaged neurons were detected.

RESULTS

There was no significant difference between the normal control group and sham-operated group in the expression of mGluR4 (P>0.05). The animals exposed to DBI showed a significant increased expression of mRNA of mGluR4 compared with that of the sham-operated animals 1 h after injuries (P<0.05). At 6 h, the evolution of neuronal expression of mGluR4 in the trauma alone group was relatively static. Compared with saline-treated control animals, rats treated with L-AP4 showed decreased number of damaged neurons and a better motor and cognitive performance.

CONCLUSIONS

The increased expression of mGluR4 is an important process in the pathophysiological of DBI and its specific agonist L-AP4 can provide a remarkable neuroprotection against DBI not only at the histopathological level but also in the motor and cognitive performance.

Impact of early pharmacological treatment on cognitive and behavioral outcome after traumatic brain injury in adults: a meta-analysis

Early pharmacological treatment has the potential to reduce some of the disabling cognitive and behavioral problems that result from traumatic brain injury (TBI). Although a large number of treatments have been developed, clinical research has yielded inconsistent findings with respect to the effectiveness of these pharmacological treatments on cognitive and behavioral outcomes. Furthermore, their relative efficacy has not been evaluated, thereby hindering advances in the treatment of TBI. A meta-analysis of research that examined the impact of pharmacological treatments on cognitive and behavioral outcomes in the early stages after TBI between January 1980 and May 2008 was therefore undertaken. The PubMed and PsycINFO databases were searched using 35 terms. All articles were screened using detailed inclusion criteria. Weighted Cohen's d effect sizes, percent overlap statistics, and fail-safe N statistics were calculated for each pharmacological agent. Studies that used different experimental designs were examined separately. Eleven pharmacological treatments were investigated by 22 clinical studies, comprising 6472 TBI patients in the treatment groups and 6460 TBI controls. One dopamine agonist (amantadine) and 1 bradykinin antagonist (CP-0127 [Bradycor]) produced marked treatment benefits (d > or = 0.8) for a single measure of arousal (Glasgow Coma Scale). Notably, drug dosage and the measure chosen to assess outcome influenced the probability of finding a treatment benefit.

Extent of nerve cell injury in Marmarou's model compared to other brain trauma models

OBJECTIVES

We sought to determine the extent of nerve cell injury in the Marmarou's acceleration impact model of diffuse brain injury.

METHODS

Sensitive markers for cell injury including immunostaining for beta-amyloid precursor protein (beta-APP, a marker for diffuse axonal injury, DAI), Fluoro-Jade (FJ) histochemistry and electron microscopy (EM) were used in sham-operated and traumatized brains.

RESULTS

APP immunostaining confirmed and extended previous findings of DAI in association and subcortical fiber systems in the white matter after injury. Increasing FJ labeling of neurons in layers II-III of sensorimotor cortex (smCx) from 4 to 48 hours after trauma and scattered labeled cells were found in the lower cortical layers. EM confirmed the presence of dystrophic pyramidal neurons in layers II-III of smCx 24 and 48 hours post-trauma.

DISCUSSION

Taken together, the data revealed significant nerve cell injury without apparent cell death in this model.

Behavioral pre-conditioning enhances angiogenesis and cognitive outcome after brain trauma

OBJECTIVES

In this study, we used Marmarou's model of traumatic brain injury (TBI) and sought to determine: (1) the effect of TBI on cognitive outcome measured on a radial arm maze; (2) the effect of behavioral conditioning before TBI, i.e. pre-conditioning, on cognitive outcome; (3) the effect of pre-conditioning on angiogenesis.

METHODS

Cognitive outcome was measured by performance on an eight-arm radial maze. Behavioral conditioning consisted of daily exposure of animals to the radial arm maze. Latency and number of errors were recorded as an index of overall performance and acquisition of the test. Extent of angiogenesis was measured by vascular endothelial growth factor receptor 2 (VEGFR2) immunofluorescence and by determining capillary density.

RESULTS

Our results indicated that trauma alone causes significant cognitive impairments. Pre-conditioning caused a marked improvement in radial arm maze performance following injury. These results coincide with both a significant increase in VEGFR2 expression and increased capillary density within the cortex and hippocampus.

DISCUSSION

TBI causes significant impairments in cognition. These deficits can be ameliorated using a pre-conditioning paradigm. While the precise mechanism has yet to be elucidated, our results indicate that angiogenesis may underlie the cognitive sparing seen in pre-conditioned animals.

Metabotropic glutamate receptor antagonists and agonists: potential neuroprotectors in diffuse brain injury

Our previous study has suggested that metabotropic glutamate receptors (mGluRs) were significantly involved in the secondary processes after diffuse brain injury (DBI) and that mGluRs antagonists or agonists may be used for the treatment of DBI. In the present study, the neuroprotective effects of antagonists or agonists of mGluRs on DBI were further investigated. Sprague-Dawly rats were randomized into the following six groups: (i) normal control; (ii) sham-operated control; (iii) DBI; (iv) DBI treated with normal saline (NS); (v) DBI treated with alpha-methyl-4-carboxy-phenylglycine (MCPG); and (vi) DBI treated with (2S,1'R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV). Animals were injected intracerebroventricularly (icv) with 10 microL MCPG (100mmol/L), DCG-IV (10nmol/L) or the equivalent volume of normal saline 1 h after injury. The neurological severity score (NSS), brain water content and the number of damaged neurons were determined 6, 12, 24, 72 and 168 h after injury. In rats with DBI, it was found that the NSS was improved and the water content in the frontal cortex and the number of damaged neurons in the parietal cortex were significantly reduced following icv injection of either MCPG or DCG-IV. This suggests that icv injection of the mGluR group I antagonist MCPG or the mGluR group II agonist DCG-IV may exert neuroprotective effects in the early stage after DBI.

Stretch-induced injury in organotypic hippocampal slice cultures reproduces in vivo post-traumatic neurodegeneration: role of glutamate receptors and voltage-dependent calcium channels

The relationship between an initial mechanical event causing brain tissue deformation and delayed neurodegeneration in vivo is complex because of the multiplicity of factors involved. We have used a simplified brain surrogate based on rat hippocampal slices grown on deformable silicone membranes to study stretch-induced traumatic brain injury. Traumatic injury was induced by stretching the culture substrate, and the biological response characterized after 4 days. Morphological abnormalities consistent with traumatic injury in humans were widely observed in injured cultures. Synaptic function was significantly reduced after a severe injury. The N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 attenuated neuronal damage, prevented loss of microtubule-associated protein 2 immunoreactivity and attenuated reduction of synaptic function. In contrast, the NMDA receptor antagonists 3-[(R)-2-carboxypiperazin-4-yl]-propyl-1-phosphonic acid (CPP) and GYKI53655, were neuroprotective in a moderate but not a severe injury paradigm. Nifedipine, an L-type voltage-dependent calcium channel antagonist was protective only after a moderate injury, whereas omega-conotoxin attenuated damage following severe injury. These results indicate that the mechanism of damage following stretch injury is complex and varies depending on the severity of the insult. In conclusion, the pharmacological, morphological and electrophysiological responses of organotypic hippocampal slice cultures to stretch injury were similar to those observed in vivo. Our model provides an alternative to animal testing for understanding the mechanisms of post-traumatic delayed cell death and could be used as a high-content screen to discover neuroprotective compounds before advancing to in vivo models.

Current concepts of cerebral oxygen transport and energy metabolism after severe traumatic brain injury

Before energy metabolism can take place, brain cells must be supplied with oxygen and glucose. Only then, in combination with normal mitochondrial function, sufficient energy (adenosine tri-phosphate (ATP)) can be produced. Glucose is virtually the sole fuel for the human brain. The brain lacks fuel stores and requires a continuous supply of glucose and oxygen. Therefore, continuous cerebral blood flow (CBF), cerebral oxygen tension and delivery, and normal mitochondrial function are of vital importance for the maintenance of brain function and tissue viability. This review focuses on three main issues: (1) Cerebral oxygen transport (CBF, and oxygen partial pressure (PO2) and delivery to the brain); (2) Energy metabolism (glycolysis, mitochondrial function: citric acid cycle and oxidative phosphorylation); and (3) The role of the above in the pathophysiology of severe head injury. Basic understanding of these issues in the normal as well as in the traumatized brain is essential in developing new treatment strategies. These issues also play a key role in interpreting data collected from monitoring techniques such as cerebral tissue PO2, jugular bulb oxygen saturation (SjvO2), near infra red spectroscopy (NIRS), microdialysis, intracranial pressure monitoring (ICP), laser Doppler flowmetry, and transcranial Doppler flowmetry--both in the experimental and in the clinical setting.

Clinical treatments for mitochondrial dysfunctions after brain injury

PURPOSE OF REVIEW

This review provides a comprehensive look at the evidence supporting the role of mitochondrial dysfunction in promoting neuronal death after acute brain injury, and critically discusses the most recent proposed therapies that could limit the deleterious effects of such a dysfunction on neurological outcome.

RECENT FINDINGS

Following acute brain injury, disruption of calcium homeostasis, overproduction of reactive oxygen species, and opening of the mitochondrial permeability transition pore, are key factors in promoting mitochondrial dysfunction, with ensuing activation of either necrotic or apoptotic cell death pathways. Growing interest has been focused on developing new therapeutic strategies able to oppose these mechanisms. Several pharmacological agents are currently under investigation, including novel calcium channel blockers and antioxidants, uncoupling proteins and mitochondrial permeability transition pore inhibitors. Although a 'magic bullet' has not yet been identified, the results of both preclinical and clinical studies are encouraging.

SUMMARY

Therapeutic interventions directly targeting processes and mechanisms responsible for mitochondrial dysfunction, may offer neuroprotection in brain-injured patients. The multifactorial cause of mitochondrial dysfunction suggests, however, the need for further studies aimed at clarifying optimal dose and time for drug administration, as well as the logical combination/sequence of those approaches that may ultimately achieve improvement in neurological outcome.

Neuroprotection in the rat lateral fluid percussion model of traumatic brain injury by SNX-185, an N-type voltage-gated calcium channel blocker

Overload of intracellular calcium ([Ca(2+)](i)) following traumatic brain injury (TBI) has been implicated in the pathogenesis of neuronal injury and death. Voltage-gated calcium channels (VGCCs) provide one of the major sources of Ca(2+) entry into cells. Therefore, the potential neuroprotective activity of SNX-185, a specific N-type VGCC blocker, was tested in rats using the lateral fluid percussion (LFP) model of TBI. SNX-185 (50, 100, or 200 pmol) or vehicle was injected 5 min after injury into the CA2-3 subregion of the hippocampus ipsilateral to TBI. Acute neuronal degeneration was visualized in brain sections 24 h postinjury using the histofluorescent marker Fluoro-Jade (FJ), and the number of surviving neurons in the CA2-3 subregion of the hippocampus 42 days after injury was determined stereologically. Behavioral outcome after TBI and drug treatment was assessed in the beam walk test and Morris water maze. Direct injection of SNX-185 into the CA2-3 region of the hippocampus reduced neuronal injury 24 h after TBI and increased neuronal survival at 42 days at each of the three drug concentrations. Behavioral outcome in both the beam walk and Morris water maze were also improved by SNX-185, with 100 and 200 pmol, but not 50 pmol SNX-185 providing neuroprotection. These data support previous studies demonstrating substantial neuroprotection after TBI by treatment with N-type VGCC blockers.

Motor and cognitive function evaluation following experimental traumatic brain injury

Traumatic brain injury (TBI) in humans may cause extensive sensorimotor and cognitive dysfunction. As a result, many TBI researchers are beginning to assess behavioral correlates of histologically determined damage in animal models. Although this is an important step in TBI research, there is a need for standardization between laboratories. The ability to reliably test treatments across laboratories and multiple injury models will close the gap between treatment success in the lab and success in the clinic. The goal of this review is to describe and evaluate the tests employed to assess functional outcome after TBI and to overview aspects of cognitive, sensory, and motor function that may be suitable targets for therapeutic intervention.

Neuroprotection and peptide toxins

Neurodegeneration induced by excitatory neurotransmitter glutamate is considered to be of particular relevance in several types of acute and chronic neurological impairments ranging from cerebral ischaemia to neuropathological conditions such as motor neuron disease, Alzheimer's, Parkinson's disease and epilepsy. The hyperexcitation of glutamate receptors coupled with calcium overload can be prevented or modulated by using well-established competitive and non-competitive antagonists targeting ion/receptor channels. The exponentially increasing body of pharmacological evidence over the years indicates potential applications of peptide toxins, due to their exquisite subtype selectivity on ion channels and receptors, as lead structures for the development of drugs for the treatment of wide variety of neurological disorders. This review comprehensively highlights the overview of the diversity in the molecular as well as neurobiological mechanisms of different peptide toxins derived from venomous animals with particular reference to neuroprotection. In addition, the potential applications of peptide toxins in the diagnosis and treatment of neurological disorders such as neuromuscular disorders, epilepsy, Alzheimer's and Parkinson's diseases, gliomas and ischaemic stroke and their future prospects in the diagnosis as well as in the therapy are addressed.

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

The behavioral and histological effects of the lateral fluid percussion (LFP) brain injury model were compared with the weight drop impact-acceleration model with 10 min of secondary hypoxia (WDIA + H). LFP injury resulted in significant motor deficits on the beam walk and inclined plane, and memory deficits on the radial arm maze and Morris water maze. Motor deficits following LFP remained throughout 6 weeks of behavioral testing. WDIA + H injury produced significant motor deficits on the beam walk and inclined plane immediately following injury, but these effects were transient and recovered by 14 days post-injury. In contrast to the LFP injury, the WDIA + H injured animals showed no memory deficits on the radial arm maze and Morris water maze. In order to determine if the differences in behavioral outcome between models were due to differences in injury mechanism or injury severity, 10 LFP-injured animals were matched with 10 WDIA-injured animals based on injury severity (i.e., time to regain righting reflex after brain injury). The LFP-matched injury group showed greater impairment than the WDIA + H matched injury group on the radial arm maze and Morris water maze. Histological examination of LFP-injured brains with Fluoro-Jade staining 24 h, 48 h, and 7 days post-injury revealed degenerating neurons in the cortex, thalamus, hippocampus, caudate-putamen, brainstem, and cerebellum, with degenerating fibers tracts in the corpus callosum and other major tracts throughout the brain. Fluoro-Jade staining following WDIA+H injury revealed damage to fibers in the optic tract, lateral olfactory tract, corpus callosum, anterior commissure, caudate-putamen, brain stem, and cerebellum. While both models produce reliable and characteristic behavioral and neuronal pathologies, their differences are important to consider when choosing a brain injury model.

Secondary injuries in brain trauma: effects of hypothermia

Hypothermia has been shown to be cerebroprotective in traumatized brains. Although a large number of traumatic brain injury (TBI) studies in animals have shown that hypothermia is effective in suppressing a variety of damaging mechanisms, clinical investigations have shown less consistent results. The complexity of damaging mechanisms in human TBI may contribute to these discrepancies. In particular, secondary injuries such as hypotension and hypoxemia may promote poor outcome. However, few experimental TBI studies have employed complex models that included such secondary injuries to clarify the efficacy of hypothermia. This review discusses the effects of hypothermia in various TBI models addressing primary and acute secondary injuries. Included are recently published clinical data using hypothermia as a therapeutic tool for preventing or reducing the detrimental posttraumatic secondary injuries and neurobehavioral deficits. Also discussed are recent successful applications of hypothermia from outside the TBI realm. Based on all available data, some general considerations for the application of hypothermia in TBI patients are given.

Improvement in mitochondrial dysfunction as a new surrogate efficiency measure for preclinical trials: dose-response and time-window profiles for administration of the calcium channel blocker Ziconotide in experimental brain injury

OBJECT

Determining the efficacy of a drug used in experimental traumatic brain injury (TBI) requires the use of one or more outcome measures such as decreased mortality or fewer neurological and neuropsychological deficits. Unfortunately, outcomes in these test batteries have a fairly large variability, requiring relatively large sample sizes, and administration of the tests themselves is also very time consuming. The authors previously demonstrated that experimental TBI and human TBI induce mitochondrial dysfunction. Because mitochondrial dysfunction is easy to assess compared with neurobehavioral endpoints, it might prove useful as an outcome measure to establish therapeutic time windows and dose-response curves in preclinical drug testing. This idea was tested in a model of TBI in rats.

METHODS

Animals treated with the selective N-type voltage-sensitive calcium channel blocker Ziconotide (also known as SNX-111 and CI-1009) after cortical impact displayed significant improvement in brain mitochondrial function. When a single intravenous bolus injection of 4 mg/kg Ziconotide was given at different time intervals, ranging from 15 minutes before injury to 10 hours after injury, mitochondrial function was improved at all time points, but more so between 2 and 6 hours postinjury. The authors evaluated the effects on mitochondrial function of Ziconotide at different doses by administering 0.5 to 6 mg/kg as a single bolus injection 4 hours after injury, and found 4 mg/kg to be the optimum dose.

CONCLUSIONS

The authors established these time-window profiles and dose-response curves on the basis of mitochondrial outcome measures in a total of 42 rats because there were such low standard deviations in these tests. Establishing similar time-window profiles and dose-response curves by using neurobehavioral endpoints would have required using 114 rats in much more elaborate experiments.

Impaired cerebral mitochondrial function after traumatic brain injury in humans

OBJECT

Oxygen supply to the brain is often insufficient after traumatic brain injury (TBI), and this results in decreased energy production (adenosine triphosphate [ATP]) with consequent neuronal cell death. It is obviously important to restore oxygen delivery after TBI; however, increasing oxygen delivery alone may not improve ATP production if the patient's mitochondria (the source of ATP) are impaired. Traumatic brain injury has been shown to impair mitochondrial function in animals; however, no human studies have been previously reported.

METHODS

Using tissue fractionation procedures, living mitochondria derived from therapeutically removed brain tissue were analyzed in 16 patients with head injury (Glasgow Coma Scale Scores 3-14) and two patients without head injury. Results revealed that in head-injured patients mitochondrial function was impaired, with subsequent decreased ATP production.

CONCLUSIONS

Decreased oxygen metabolism due to mitochondrial dysfunction must be taken into account when clinically defining ischemia and interpreting oxygen measurements such as jugular venous oxygen saturation, arteriovenous difference in oxygen content, direct tissue oxygen tension, and cerebral blood oxygen content determined using near-infrared spectroscopy. Restoring mitochondrial function might be as important as maintaining oxygen delivery.