1
|
Barker-Haliski M, Hawkins NA. Innovative drug discovery strategies in epilepsy: integrating next-generation syndrome-specific mouse models to address pharmacoresistance and epileptogenesis. Expert Opin Drug Discov 2024; 19:1099-1113. [PMID: 39075876 PMCID: PMC11390315 DOI: 10.1080/17460441.2024.2384455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2024] [Accepted: 07/22/2024] [Indexed: 07/31/2024]
Abstract
INTRODUCTION Although there are numerous treatment options already available for epilepsy, over 30% of patients remain resistant to these antiseizure medications (ASMs). Historically, ASM discovery has relied on the demonstration of efficacy through the use of 'traditional' acute in vivo seizure models (e.g. maximal electroshock, subcutaneous pentylenetetrazol, and kindling). However, advances in genetic sequencing technologies and remaining medical needs for people with treatment-resistant epilepsy or special patient populations have encouraged recent efforts to identify novel compounds in syndrome-specific models of epilepsy. Syndrome-specific models, including Scn1a variant models of Dravet syndrome and APP/PS1 mice associated with familial early-onset Alzheimer's disease, have already led to the discovery of two mechanistically novel treatments for developmental and epileptic encephalopathies (DEEs), namely cannabidiol and soticlestat, respectively. AREAS COVERED In this review, the authors discuss how it is likely that next-generation drug discovery efforts for epilepsy will more comprehensively integrate syndrome-specific epilepsy models into early drug discovery providing the reader with their expert perspectives. EXPERT OPINION The percentage of patients with pharmacoresistant epilepsy has remained unchanged despite over 30 marketed ASMs. Consequently, there is a high unmet need to reinvent and revise discovery strategies to more effectively address the remaining needs of patients with specific epilepsy syndromes, including drug-resistant epilepsy and DEEs.
Collapse
Affiliation(s)
| | - Nicole A Hawkins
- Feinberg School of Medicine Chicago, Northwestern University, Chicago, IL, USA
| |
Collapse
|
2
|
Beitchman JA, Krishna G, Bromberg CE, Thomas TC. Effects of isoflurane and urethane anesthetics on glutamate neurotransmission in rat brain using in vivo amperometry. BMC Neurosci 2023; 24:52. [PMID: 37817064 PMCID: PMC10563344 DOI: 10.1186/s12868-023-00822-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Accepted: 09/19/2023] [Indexed: 10/12/2023] Open
Abstract
BACKGROUND Aspects of glutamate neurotransmission implicated in normal and pathological conditions are predominantly evaluated using in vivo recording paradigms in rats anesthetized with isoflurane or urethane. Urethane and isoflurane anesthesia influence glutamate neurotransmission through different mechanisms; however, real-time outcome measures of potassium chloride (KCl)-evoked glutamate overflow and glutamate clearance kinetics have not been compared within and between regions of the brain. In order to maintain rigor and reproducibility within the literature between the two most common methods of anesthetized in vivo recording of glutamate, we compared glutamate signaling as a function of anesthesia and brain region in the rat strain most used in neuroscience. METHODS In the following experiments, in vivo amperometric recordings of KCl-evoked glutamate overflow and glutamate clearance kinetics (uptake rate and T80) in the cortex, hippocampus, and thalamus were performed using glutamate-selective microelectrode arrays (MEAs) in young adult male, Sprague-Dawley rats anesthetized with either isoflurane or urethane. RESULTS Potassium chloride (KCl)-evoked glutamate overflow was similar under urethane and isoflurane anesthesia in all brain regions studied. Analysis of glutamate clearance determined that the uptake rate was significantly faster (53.2%, p < 0.05) within the thalamus under urethane compared to isoflurane, but no differences were measured in the cortex or hippocampus. Under urethane, glutamate clearance parameters were region-dependent, with significantly faster glutamate clearance in the thalamus compared to the cortex but not the hippocampus (p < 0.05). No region-dependent differences were measured for glutamate overflow using isoflurane. CONCLUSIONS These data support that amperometric recordings of KCl-evoked glutamate under isoflurane and urethane anesthesia result in similar and comparable data. However, certain parameters of glutamate clearance can vary based on choice of anesthesia and brain region. In these circumstances, special considerations are needed when comparing previous literature and planning future experiments.
Collapse
Affiliation(s)
- Joshua A Beitchman
- Department of Child Health, University of Arizona College of Medicine - Phoenix, 425 N. 5th St. | 322 ABC-1 Building, Phoenix, AZ, 85004-2127, USA
- Barrow Neurological Institute at Phoenix Children's Hospital, Phoenix Children's Hospital, Phoenix, AZ, USA
- College of Graduate Studies, Midwestern University, Glendale, AZ, USA
| | - Gokul Krishna
- Department of Child Health, University of Arizona College of Medicine - Phoenix, 425 N. 5th St. | 322 ABC-1 Building, Phoenix, AZ, 85004-2127, USA
- Barrow Neurological Institute at Phoenix Children's Hospital, Phoenix Children's Hospital, Phoenix, AZ, USA
| | - Caitlin E Bromberg
- Department of Child Health, University of Arizona College of Medicine - Phoenix, 425 N. 5th St. | 322 ABC-1 Building, Phoenix, AZ, 85004-2127, USA
- Barrow Neurological Institute at Phoenix Children's Hospital, Phoenix Children's Hospital, Phoenix, AZ, USA
| | - Theresa Currier Thomas
- Department of Child Health, University of Arizona College of Medicine - Phoenix, 425 N. 5th St. | 322 ABC-1 Building, Phoenix, AZ, 85004-2127, USA.
- Barrow Neurological Institute at Phoenix Children's Hospital, Phoenix Children's Hospital, Phoenix, AZ, USA.
- Phoenix VA Healthcare System, Phoenix, AZ, USA.
| |
Collapse
|
3
|
Beitchman JA, Krishna G, Bromberg CE, Thomas TC. Effects of isoflurane and urethane anesthetics on glutamate neurotransmission in rat brain using in vivo amperometry. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.16.528856. [PMID: 36824899 PMCID: PMC9949081 DOI: 10.1101/2023.02.16.528856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
Aspects of glutamate neurotransmission implicated in normal and pathological conditions are often evaluated using in vivo recording paradigms in rats anesthetized with isoflurane or urethane. Urethane and isoflurane anesthesia influence glutamate neurotransmission through different mechanisms; however real-time outcome measures of potassium chloride (KCl)-evoked glutamate overflow and glutamate clearance kinetics have not been compared within and between regions of the brain. In the following experiments, in vivo amperometric recordings of KCl-evoked glutamate overflow and glutamate clearance kinetics (uptake rate and T80) in the cortex, hippocampus and thalamus were performed using glutamate-selective microelectrode arrays (MEAs) in young adult male, Sprague-Dawley rats anesthetized with isoflurane or urethane. Potassium chloride (KCl)-evoked glutamate overflow was similar under urethane and isoflurane anesthesia in all brain regions studied. Analysis of glutamate clearance determined that the uptake rate was significantly faster (53.2%, p<0.05) within the thalamus under urethane compared to isoflurane, but no differences were measured in the cortex or hippocampus. Under urethane, glutamate clearance parameters were region dependent, with significantly faster glutamate clearance in the thalamus compared to the cortex but not the hippocampus (p<0.05). No region dependent differences were measured for glutamate overflow using isoflurane. These data support that amperometric recordings of glutamate under isoflurane and urethane anesthesia result in mostly similar and comparable data. However, certain parameters of glutamate uptake vary based on choice of anesthesia and brain region. Special considerations must be given to these areas when considering comparison to previous literature and when planning future experiments.
Collapse
Affiliation(s)
- Joshua A. Beitchman
- BARROW Neurological Institute at Phoenix Children’s Hospital, Phoenix, AZ, USA
- Department of Child Health, University of Arizona College of Medicine-Phoenix, Phoenix, AZ, USA
- College of Graduate Studies, Midwestern University, Glendale, AZ, USA
| | - Gokul Krishna
- BARROW Neurological Institute at Phoenix Children’s Hospital, Phoenix, AZ, USA
- Department of Child Health, University of Arizona College of Medicine-Phoenix, Phoenix, AZ, USA
| | - Caitlin E. Bromberg
- BARROW Neurological Institute at Phoenix Children’s Hospital, Phoenix, AZ, USA
- Department of Child Health, University of Arizona College of Medicine-Phoenix, Phoenix, AZ, USA
| | - Theresa Currier Thomas
- BARROW Neurological Institute at Phoenix Children’s Hospital, Phoenix, AZ, USA
- Department of Child Health, University of Arizona College of Medicine-Phoenix, Phoenix, AZ, USA
- Phoenix VA Healthcare System, Phoenix, AZ, USA
| |
Collapse
|
4
|
Barker-Haliski M, Pitsch J, Galanopoulou AS, Köhling R. A companion to the preclinical common data elements for phenotyping seizures and epilepsy in rodent models. A report of the TASK3-WG1C: Phenotyping working group of the ILAE/AES joint translational task force. Epilepsia Open 2022. [PMID: 36461665 DOI: 10.1002/epi4.12676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 05/23/2022] [Indexed: 12/04/2022] Open
Abstract
Epilepsy is a heterogeneous disorder characterized by spontaneous seizures and behavioral comorbidities. The underlying mechanisms of seizures and epilepsy across various syndromes lead to diverse clinical presentation and features. Similarly, animal models of epilepsy arise from numerous dissimilar inciting events. Preclinical seizure and epilepsy models can be evoked through many different protocols, leaving the phenotypic reporting subject to diverse interpretations. Serendipity can also play an outsized role in uncovering novel drivers of seizures or epilepsy, with some investigators even stumbling into epilepsy research because of a new genetic cross or unintentional drug effect. The heightened emphasis on rigor and reproducibility in preclinical research, including that which is conducted for epilepsy, underscores the need for standardized phenotyping strategies. To address this goal as part of the TASK3-WG1C Working Group of the International League Against Epilepsy (ILAE)/American Epilepsy Society (AES) Joint Translational Task Force, we developed a case report form (CRF) to describe the common data elements (CDEs) necessary for the phenotyping of seizure-like behaviors in rodents. This companion manuscript describes the use of the proposed CDEs and CRF for the visual, behavioral phenotyping of seizure-like behaviors. These phenotyping CDEs and accompanying CRF can be used in parallel with video-electroencephalography (EEG) studies or as a first visual screen to determine whether a model manifests seizure-like behaviors before utilizing more specialized diagnostic tests, like video-EEG. Systematic logging of seizure-like behaviors may help identify models that could benefit from more specialized diagnostic tests to determine whether these are epileptic seizures, such as video-EEG.
Collapse
Affiliation(s)
- Melissa Barker-Haliski
- Department of Pharmacy, School of Pharmacy, University of Washington, Seattle, Washington, USA
| | - Julika Pitsch
- Department of Epileptology, University Hospital Bonn, Bonn, Germany
| | - Aristea S Galanopoulou
- Saul R. Korey Department of Neurology, Isabelle Rapin Division of Child Neurology, Laboratory of Developmental Epilepsy, Albert Einstein College of Medicine, Bronx, New York, USA
- Dominick P Purpura Department of Neuroscience, Isabelle Rapin Division of Child Neurology, Laboratory of Developmental Epilepsy, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Rüdiger Köhling
- Oscar-Langendorff-Institut für Physiologie, Universitätsmedizin Rostock, Rostock, Germany
| |
Collapse
|
5
|
Karimi SA, Hosseinmardi N, Sayyah M, Hajisoltani R, Janahmadi M. Enhancement of intrinsic neuronal excitability-mediated by a reduction in hyperpolarization-activated cation current (I h ) in hippocampal CA1 neurons in a rat model of traumatic brain injury. Hippocampus 2020; 31:156-169. [PMID: 33107111 DOI: 10.1002/hipo.23270] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2020] [Revised: 09/28/2020] [Accepted: 10/04/2020] [Indexed: 01/13/2023]
Abstract
Traumatic brain injury (TBI) is associated with epileptiform activity in the hippocampus; however, the underlying mechanisms have not been fully determined. The goal was to understand what changes take place in intrinsic neuronal physiology in the hippocampus after blunt force trauma to the cortex. In this context, hyperpolarization-activated cation current (Ih ) currents may have a critical role in modulating the neuronal intrinsic membrane excitability; therefore, its contribution to the TBI-induced hyperexcitability was assessed. In a model of TBI caused by controlled cortical impact (CCI), the intrinsic electrophysiological properties of pyramidal neurons were examined 1 week after TBI induction in rats. Whole-cell patch-clamp recordings were performed under current- and voltage-clamp conditions following ionotropic receptors blockade. Induction of TBI caused changes in the intrinsic excitability of pyramidal neurons, as shown by a significant increase and decrease in firing frequency and in the rheobase current, respectively (p < .05). The evoked firing rate and the action potential time to peak were also significantly increased and decreased, respectively (p < .05). In the TBI group, the amplitude of instantaneous and steady-state Ih currents was both significantly smaller than those in the control group (p < .05). The Ih current density was also significantly decreased (p < .001). Findings indicated that TBI led to an increase in the intrinsic excitability in CA1 pyramidal neurons and changes in Ih current could be, in part, one of the underlying mechanisms involved in this hyperexcitability.
Collapse
Affiliation(s)
- Seyed Asaad Karimi
- Neuroscience Research Center, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.,Department of Physiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.,Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran.,Department of Neuroscience, School of Science and Advanced Technologies in Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Narges Hosseinmardi
- Department of Physiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mohammad Sayyah
- Department of Physiology and Pharmacology, Pasteur Institute of Iran, Tehran, Iran
| | - Razieh Hajisoltani
- Department of Physiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mahyar Janahmadi
- Neuroscience Research Center, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.,Department of Physiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| |
Collapse
|
6
|
Acute treatment with doxorubicin affects glutamate neurotransmission in the mouse frontal cortex and hippocampus. Brain Res 2017; 1672:10-17. [PMID: 28705715 DOI: 10.1016/j.brainres.2017.07.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 06/08/2017] [Accepted: 07/04/2017] [Indexed: 11/21/2022]
Abstract
Doxorubicin (DOX) is a potent chemotherapeutic agent known to cause acute and long-term cognitive impairments in cancer patients. Cognitive function is presumed to be primarily mediated by neuronal circuitry in the frontal cortex (FC) and hippocampus, where glutamate is the primary excitatory neurotransmitter. Mice treated with DOX (25mg/kg i.p.) were subjected to in vivo recordings under urethane anesthesia at 24h post-DOX injection or 5 consecutive days of cognitive testing (Morris Water Maze; MWM). Using novel glutamate-selective microelectrode arrays, amperometric recordings measured parameters of extracellular glutamate clearance and potassium-evoked release of glutamate within the medial FC and dentate gyrus (DG) of the hippocampus. By 24h post-DOX injection, glutamate uptake was 45% slower in the FC in comparison to saline-treated mice. In the DG, glutamate took 48% longer to clear than saline-treated mice. Glutamate overflow in the FC was similar between treatment groups, however, it was significantly increased in the DG of DOX treated mice. MWM data indicated that a single dose of DOX impaired swim speed without impacting total length traveled. These data indicate that systemic DOX treatment changes glutamate neurotransmission in key nuclei associated with cognitive function within 24h, without a lasting impact on spatial learning and memory. Understanding the functional effects of DOX on glutamate neurotransmission may help us understand and prevent some of the debilitating side effects of chemotherapeutic treatment in cancer survivors.
Collapse
|
7
|
Hertz L, Chen Y. Importance of astrocytes for potassium ion (K+) homeostasis in brain and glial effects of K+ and its transporters on learning. Neurosci Biobehav Rev 2016; 71:484-505. [DOI: 10.1016/j.neubiorev.2016.09.018] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 08/12/2016] [Accepted: 09/23/2016] [Indexed: 10/20/2022]
|
8
|
Ortiz F, Gutiérrez R. Entorhinal cortex lesions result in adenosine-sensitive high frequency oscillations in the hippocampus. Exp Neurol 2015; 271:319-28. [DOI: 10.1016/j.expneurol.2015.06.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 05/19/2015] [Accepted: 06/07/2015] [Indexed: 12/17/2022]
|
9
|
Wahab RA, Neuberger EJ, Lyeth BG, Santhakumar V, Pfister BJ. Fluid percussion injury device for the precise control of injury parameters. J Neurosci Methods 2015; 248:16-26. [DOI: 10.1016/j.jneumeth.2015.03.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Revised: 03/05/2015] [Accepted: 03/06/2015] [Indexed: 01/06/2023]
|
10
|
Li Y, Korgaonkar AA, Swietek B, Wang J, Elgammal FS, Elkabes S, Santhakumar V. Toll-like receptor 4 enhancement of non-NMDA synaptic currents increases dentate excitability after brain injury. Neurobiol Dis 2014; 74:240-53. [PMID: 25497689 DOI: 10.1016/j.nbd.2014.11.021] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Revised: 11/21/2014] [Accepted: 11/26/2014] [Indexed: 11/18/2022] Open
Abstract
Concussive brain injury results in neuronal degeneration, microglial activation and enhanced excitability in the hippocampal dentate gyrus, increasing the risk for epilepsy and memory dysfunction. Endogenous molecules released during injury can activate innate immune responses including toll-like receptor 4 (TLR4). Recent studies indicate that immune mediators can modulate neuronal excitability. Since non-specific agents that reduce TLR4 signaling can limit post-traumatic neuropathology, we examined whether TLR4 signaling contributes to early changes in dentate excitability after brain injury. Concussive brain injury caused a transient increase in hippocampal TLR4 expression within 4h, which peaked at 24h. Post-injury increase in TLR4 expression in the dentate gyrus was primarily neuronal and persisted for one week. Acute, in vitro treatment with TLR4 ligands caused bidirectional modulation of dentate excitability in control and brain-injured rats, with a reversal in the direction of modulation after brain injury. TLR4 antagonists decreased, and agonist increased, afferent-evoked dentate excitability one week after brain injury. NMDA receptor antagonist did not occlude the ability of LPS-RS, a TLR4 antagonist, to decrease post-traumatic dentate excitability. LPS-RS failed to modulate granule cell NMDA EPSCs but decreased perforant path-evoked non-NMDA EPSC peak amplitude and charge transfer in both granule cells and mossy cells. Our findings indicate an active role for TLR4 signaling in early post-traumatic dentate hyperexcitability. The novel TLR4 modulation of non-NMDA glutamatergic currents, identified herein, could represent a general mechanism by which immune activation influences neuronal excitability in neurological disorders that recruit sterile inflammatory responses.
Collapse
Affiliation(s)
- Ying Li
- Department of Neurology and Neurosciences, Rutgers New Jersey Medical School, Newark, NJ 07103, USA
| | - Akshata A Korgaonkar
- Department of Neurology and Neurosciences, Rutgers New Jersey Medical School, Newark, NJ 07103, USA; Graduate School of Biomedical Sciences, Rutgers New Jersey Medical School, Newark, NJ 07103, USA
| | - Bogumila Swietek
- Department of Neurology and Neurosciences, Rutgers New Jersey Medical School, Newark, NJ 07103, USA
| | - Jianfeng Wang
- Department of Neurology and Neurosciences, Rutgers New Jersey Medical School, Newark, NJ 07103, USA
| | - Fatima S Elgammal
- Department of Neurology and Neurosciences, Rutgers New Jersey Medical School, Newark, NJ 07103, USA
| | - Stella Elkabes
- Graduate School of Biomedical Sciences, Rutgers New Jersey Medical School, Newark, NJ 07103, USA; Department of Neurological Surgery, Rutgers New Jersey Medical School, Newark, NJ 07103, USA
| | - Vijayalakshmi Santhakumar
- Department of Neurology and Neurosciences, Rutgers New Jersey Medical School, Newark, NJ 07103, USA; Graduate School of Biomedical Sciences, Rutgers New Jersey Medical School, Newark, NJ 07103, USA; Department of Pharmacology and Physiology, Rutgers New Jersey Medical School, Newark, NJ 07103, USA.
| |
Collapse
|
11
|
Neuberger EJ, Wahab RA, Jayakumar A, Pfister BJ, Santhakumar V. Distinct effect of impact rise times on immediate and early neuropathology after brain injury in juvenile rats. J Neurosci Res 2014; 92:1350-1361. [PMID: 24799156 DOI: 10.1002/jnr.23401] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Revised: 03/25/2014] [Accepted: 03/28/2014] [Indexed: 12/31/2022]
Abstract
Traumatic brain injury (TBI) can occur from physical trauma from a wide spectrum of insults ranging from explosions to falls. The biomechanics of the trauma can vary in key features, including the rate and magnitude of the insult. Although the effect of peak injury pressure on neurological outcome has been examined in the fluid percussion injury (FPI) model, it is unknown whether differences in rate of rise of the injury waveform modify cellular and physiological changes after TBI. Using a programmable FPI device, we examined juvenile rats subjected to a constant peak pressure at two rates of injury: a standard FPI rate of rise and a faster rate of rise to the same peak pressure. Immediate postinjury assessment identified fewer seizures and relatively brief loss of consciousness after fast-rise injuries than after standard-rise injuries at similar peak pressures. Compared with rats injured at standard rise, fewer silver-stained injured neuronal profiles and degenerating hilar neurons were observed 4-6 hr after fast-rise FPI. However, 1 week postinjury, both fast- and standard-rise FPI resulted in hilar cell loss and enhanced perforant path-evoked granule cell field excitability compared with sham controls. Notably, the extent of neuronal loss and increase in dentate excitability were not different between rats injured at fast and standard rates of rise to peak pressure. Our data indicate that reduced cellular damage and improved immediate neurological outcome after fast rising primary concussive injuries mask the severity of the subsequent cellular and neurophysiological pathology and may be unreliable as a predictor of prognosis.
Collapse
Affiliation(s)
- Eric J Neuberger
- Department of Neurology and Neurosciences, Rutgers New Jersey Medical School, Newark, New Jersey
| | - Radia Abdul Wahab
- Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, New Jersey
| | - Archana Jayakumar
- Department of Neurology and Neurosciences, Rutgers New Jersey Medical School, Newark, New Jersey
| | - Bryan J Pfister
- Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, New Jersey
| | - Vijayalakshmi Santhakumar
- Department of Neurology and Neurosciences, Rutgers New Jersey Medical School, Newark, New Jersey.,Department of Pharmacology and Physiology, Rutgers New Jersey Medical School, Newark, New Jersey
| |
Collapse
|
12
|
Volman V, Bazhenov M, Sejnowski TJ. Divide and conquer: functional segregation of synaptic inputs by astrocytic microdomains could alleviate paroxysmal activity following brain trauma. PLoS Comput Biol 2013; 9:e1002856. [PMID: 23357960 PMCID: PMC3554537 DOI: 10.1371/journal.pcbi.1002856] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Accepted: 11/09/2012] [Indexed: 12/12/2022] Open
Abstract
Traumatic brain injury often leads to epileptic seizures. Among other factors, homeostatic synaptic plasticity (HSP) mediates posttraumatic epileptogenesis through unbalanced synaptic scaling, partially compensating for the trauma-incurred loss of neural excitability. HSP is mediated in part by tumor necrosis factor alpha (TNFα), which is released locally from reactive astrocytes early after trauma in response to chronic neuronal inactivity. During this early period, TNFα is likely to be constrained to its glial sources; however, the contribution of glia-mediated spatially localized HSP to post-traumatic epileptogenesis remains poorly understood. We used computational model to investigate the reorganization of collective neural activity early after trauma. Trauma and synaptic scaling transformed asynchronous spiking into paroxysmal discharges. The rate of paroxysms could be reduced by functional segregation of synaptic input into astrocytic microdomains. Thus, we propose that trauma-triggered reactive gliosis could exert both beneficial and deleterious effects on neural activity.
Collapse
Affiliation(s)
- Vladislav Volman
- Howard Hughes Medical Institute, Computational Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, California, United States of America.
| | | | | |
Collapse
|
13
|
Dobiszewski KF, Deek MP, Ghaly A, Prodan C, Hill AA. Extracellular fluid conductivity analysis by dielectric spectroscopy for in vitro determination of cortical tissue vitality. Physiol Meas 2012; 33:1249-60. [PMID: 22735505 DOI: 10.1088/0967-3334/33/7/1249] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Brain tissue is extremely metabolically active in part due to its need to constantly maintain a precise extracellular ionic environment. Under pathological conditions, unhealthy cortical tissue loses its ability to maintain this precise environment and there is a net efflux of charged particles from the cells. Typically, this ionic efflux is measured using ion-selective microelectrodes, which measure a single ionic species at a time. In this paper, we have used a bio-sensing method, dielectric spectroscopy (DS), which allows for the simultaneous measurement of the net efflux of all charged particles from cells by measuring extracellular conductivity. We exposed cortical brain slices from the mouse to different solutions that mimic various pathological states such as hypokalemia, hyperkalemia and ischemia (via oxygen-glucose deprivation). We have found that the changes in conductivity of the extracellular solutions were proportional to the severity of the pathological insult experienced by the brain tissue. Thus, DS allows for the measurement of changes in extracellular conductivity with enough sensitivity to monitor the health of brain tissue in vitro.
Collapse
Affiliation(s)
- K F Dobiszewski
- Federated Department of Biological Sciences, New Jersey Institute of Technology and Rutgers University, Newark, NJ, USA
| | | | | | | | | |
Collapse
|
14
|
Thomas TC, Hinzman JM, Gerhardt GA, Lifshitz J. Hypersensitive glutamate signaling correlates with the development of late-onset behavioral morbidity in diffuse brain-injured circuitry. J Neurotrauma 2012; 29:187-200. [PMID: 21939393 PMCID: PMC3261793 DOI: 10.1089/neu.2011.2091] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In diffuse brain-injured rats, robust sensory sensitivity to manual whisker stimulation develops over 1 month post-injury, comparable to agitation expressed by brain-injured individuals with overstimulation. In the rat, whisker somatosensation relies on thalamocortical glutamatergic relays between the ventral posterior medial (VPM) thalamus and barrel fields of somatosensory cortex (S1BF). Using novel glutamate-selective microelectrode arrays coupled to amperometry, we test the hypothesis that disrupted glutamatergic neurotransmission underlies the whisker sensory sensitivity associated with diffuse brain injury. We report hypersensitive glutamate neurotransmission that parallels and correlates with the development of post-traumatic sensory sensitivity. Hypersensitivity is demonstrated by significant 110% increases in VPM extracellular glutamate levels, and 100% increase in potassium-evoked glutamate release in the VPM and S1BF, with no change in glutamate clearance. Further, evoked glutamate release showed 50% greater sensitivity to a calcium channel antagonist in brain-injured over uninjured VPM. In conjunction with no changes in glutamate transporter gene expression and exogenous glutamate clearance efficiency, these data support a presynaptic origin for enduring post-traumatic circuit alterations. In the anatomically-distinct whisker circuit, the injury-induced functional alterations correlate with the development of late-onset behavioral morbidity. Effective therapies to modulate presynaptic glutamate function in diffuse-injured circuits may translate into improvements in essential brain function and behavioral performance in other brain-injured circuits in rodents and in humans.
Collapse
Affiliation(s)
- Theresa Currier Thomas
- Spinal Cord & Brain Injury Research Center, University of Kentucky College of Medicine, Lexington, Kentucky
- Department of Anatomy & Neurobiology, University of Kentucky College of Medicine, Lexington, Kentucky
| | - Jason M. Hinzman
- Spinal Cord & Brain Injury Research Center, University of Kentucky College of Medicine, Lexington, Kentucky
- Department of Anatomy & Neurobiology, University of Kentucky College of Medicine, Lexington, Kentucky
- Center for Microelectrode Technology, University of Kentucky College of Medicine, Lexington, Kentucky
- Morris K. Udall Parkinson's Disease Research Center of Excellence, University of Kentucky College of Medicine, Lexington, Kentucky
| | - Greg A. Gerhardt
- Spinal Cord & Brain Injury Research Center, University of Kentucky College of Medicine, Lexington, Kentucky
- Department of Anatomy & Neurobiology, University of Kentucky College of Medicine, Lexington, Kentucky
- Center for Microelectrode Technology, University of Kentucky College of Medicine, Lexington, Kentucky
- Morris K. Udall Parkinson's Disease Research Center of Excellence, University of Kentucky College of Medicine, Lexington, Kentucky
| | - Jonathan Lifshitz
- Spinal Cord & Brain Injury Research Center, University of Kentucky College of Medicine, Lexington, Kentucky
- Department of Anatomy & Neurobiology, University of Kentucky College of Medicine, Lexington, Kentucky
- Department of Physical Medicine & Rehabilitation, University of Kentucky College of Medicine, Lexington, Kentucky
| |
Collapse
|
15
|
Lei Z, Deng P, Li J, Xu ZC. Alterations of A-type potassium channels in hippocampal neurons after traumatic brain injury. J Neurotrauma 2011; 29:235-45. [PMID: 21895522 DOI: 10.1089/neu.2010.1537] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Traumatic brain injury (TBI) is associated with cognitive deficits, memory impairment, and epilepsy. Previous studies have reported neuronal loss and neuronal hyperexcitability in the post-traumatic hippocampus. A-type K+ currents (I(A)) play a critical role in modulating the intrinsic membrane excitability of hippocampal neurons. The disruption of I(A) is reportedly linked to hippocampal dysfunction. The present study investigates the changes of I(A) in the hippocampus after TBI. TBI in rats was induced by controlled cortical impact. The impact induced a reproducible lesion in the cortex and an obvious neuronal death in the ipsilateral hippocampus CA3 region. At one week after TBI, immunohistochemical staining and Western blotting showed that the expression of I(A) channel subunit Kv4.2 was markedly decreased in the ipsilateral hippocampus, but remained unchanged in the contralateral hippocampus. Meanwhile, electrophysiological recording showed that I(A) currents in ipsilateral CA1 pyramidal neurons were significantly reduced, which was associated with an increased neuronal excitability. Furthermore, there was an increased sensitivity to bicuculline-induced seizures in TBI rats. At 8 weeks after TBI, immunohistochemical staining and electrophysiological recording indicated that I(A) returned to control levels. These findings suggest that TBI causes a transient downregulation of I(A) in hippocampal CA1 neurons, which might be associated with the hyperexcitability in the post-traumatic hippocampus, and in turn leads to seizures and epilepsy.
Collapse
Affiliation(s)
- Zhigang Lei
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | | | | | | |
Collapse
|
16
|
The impact of the glial spatial buffering on the K(+) Nernst potential. Cogn Neurodyn 2011; 5:285-91. [PMID: 22942917 DOI: 10.1007/s11571-011-9165-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Revised: 06/28/2011] [Accepted: 07/07/2011] [Indexed: 10/18/2022] Open
Abstract
Astrocytes play a critical role in CNS metabolism, regulation of volume and ion homeostasis of the interstitial space. Of special relevance is their clearance of K(+) that is released by active neurons into the extracellular space. Mathematical analysis of a modified Nernst equation for the electrochemical equilibrium of neuronal plasma membranes, suggests that K(+) uptake by glial cells is not only relevant during neuronal activity but also has a non-neglectable impact on the basic electrical membrane properties, specifically the resting membrane potential, of neurons and might be clinically valuable as a factor in the genetics and epigenetics of the epilepsy and tuberous sclerosis complex.
Collapse
|
17
|
Yu Z, Graudejus O, Tsay C, Lacour SP, Wagner S, Morrison B. Monitoring hippocampus electrical activity in vitro on an elastically deformable microelectrode array. J Neurotrauma 2010; 26:1135-45. [PMID: 19594385 DOI: 10.1089/neu.2008.0810] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Interfacing electronics and recording electrophysiological activity in mechanically active biological tissues is challenging. This challenge extends to recording neural function of brain tissue in the setting of traumatic brain injury (TBI), which is caused by rapid (within hundreds of milliseconds) and large (greater than 5% strain) brain deformation. Interfacing electrodes must be biocompatible on multiple levels and should deform with the tissue to prevent additional mechanical damage. We describe an elastically stretchable microelectrode array (SMEA) that is capable of undergoing large, biaxial, 2-D stretch while remaining functional. The new SMEA consists of elastically stretchable thin metal films on a silicone membrane. It can stimulate and detect electrical activity from cultured brain tissue (hippocampal slices), before, during, and after large biaxial deformation. We have incorporated the SMEA into a well-characterized in vitro TBI research platform, which reproduces the biomechanics of TBI by stretching the SMEA and the adherent brain slice culture. Mechanical injury parameters, such as strain and strain rate, can be precisely controlled to generate specific levels of damage. The SMEA allowed for quantification of neuronal function both before and after injury, without breaking culture sterility or repositioning the electrodes for the injury event, thus enabling serial and long-term measurements. We report tests of the SMEA and an initial application to study the effect of mechanical stimuli on neuron function, which could be employed as a high-content, drug-screening platform for TBI.
Collapse
Affiliation(s)
- Zhe Yu
- Department of Biomedical Engineering, Columbia University, New York, New York 10027, USA
| | | | | | | | | | | |
Collapse
|
18
|
Tominaga T, Tominaga Y. GABAA receptor-mediated modulation of neuronal activity propagation upon tetanic stimulation in rat hippocampal slices. Pflugers Arch 2010; 460:875-89. [DOI: 10.1007/s00424-010-0870-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2010] [Revised: 07/29/2010] [Accepted: 08/09/2010] [Indexed: 11/24/2022]
|
19
|
Shlosberg D, Benifla M, Kaufer D, Friedman A. Blood-brain barrier breakdown as a therapeutic target in traumatic brain injury. Nat Rev Neurol 2010; 6:393-403. [PMID: 20551947 DOI: 10.1038/nrneurol.2010.74] [Citation(s) in RCA: 618] [Impact Index Per Article: 44.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Traumatic brain injury (TBI) is the leading cause of death in young adults and children. The treatment of TBI in the acute phase has improved substantially; however, the prevention and management of long-term complications remain a challenge. Blood-brain barrier (BBB) breakdown has often been documented in patients with TBI, but the role of such vascular pathology in neurological dysfunction has only recently been explored. Animal studies have demonstrated that BBB breakdown is involved in the initiation of transcriptional changes in the neurovascular network that ultimately lead to delayed neuronal dysfunction and degeneration. Brain imaging data have confirmed the high incidence of BBB breakdown in patients with TBI and suggest that such pathology could be used as a biomarker in the clinic and in drug trials. Here, we review the neurological consequences of TBI, focusing on the long-term complications of such injuries. We present the clinical evidence for involvement of BBB breakdown in TBI and examine the primary and secondary mechanisms that underlie such pathology. We go on to consider the consequences of BBB injury, before analyzing potential mechanisms linking vascular pathology to neuronal dysfunction and degeneration, and exploring possible targets for treatment. Finally, we highlight areas for future basic research and clinical studies into TBI.
Collapse
Affiliation(s)
- Dan Shlosberg
- Department of Physiology and Neurobiology, Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | | | | | | |
Collapse
|
20
|
Park YK, Kim SJ. Impaired glial buffering hampers antidromic conduction of CA1 neurons during hypoxia. Brain Res 2009; 1280:90-7. [DOI: 10.1016/j.brainres.2009.05.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2009] [Revised: 04/29/2009] [Accepted: 05/02/2009] [Indexed: 11/29/2022]
|
21
|
Fröhlich F, Bazhenov M, Iragui-Madoz V, Sejnowski TJ. Potassium dynamics in the epileptic cortex: new insights on an old topic. Neuroscientist 2009; 14:422-33. [PMID: 18997121 PMCID: PMC2854295 DOI: 10.1177/1073858408317955] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The role of changes in the extracellular potassium concentration [K(+)](o) in epilepsy has remained unclear. Historically, it was hypothesized that [K(+)]( o) is the causal factor for epileptic seizures. This so-called potassium accumulation hypothesis led to substantial debate but subsequently failed to find wide acceptance. However, recent studies on the pathophysiology of tissue from epileptic human patients and animal epilepsy models revealed aberrations in [K(+)](o) regulation. Computational models of cortical circuits that include ion concentration dynamics have catalyzed a renewed interest in the role of [K(+)](o) in epilepsy. The authors here connect classical and more recent insights on [K(+)]( o) dynamics in the cortex with the goal of providing starting points for a next generation of [K(+)](o) research. Such research may ultimately lead to an entirely new class of antiepileptic drugs that act on the [K(+)](o) regulation system.
Collapse
Affiliation(s)
- Flavio Fröhlich
- Salk Institute for Biological Studies, Computational Neurobiology Laboratory, La Jolla, CA, USA
| | | | | | | |
Collapse
|
22
|
A novel apparatus for lateral fluid percussion injury in the rat. J Neurosci Methods 2008; 177:267-72. [PMID: 19022291 DOI: 10.1016/j.jneumeth.2008.10.022] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2007] [Revised: 10/09/2008] [Accepted: 10/10/2008] [Indexed: 11/22/2022]
Abstract
Lateral fluid percussion injury (LFPI) is the most commonly used experimental model of human traumatic brain injury (TBI). To date, investigators using this model have produced injury using a pendulum-and-piston-based device (PPBD) to drive fluid against an intact dural surface. Two disadvantages of this method, however, are (1) the necessary reliance on operator skill to position and release the pendulum, and (2) reductions in reproducibility due to variable friction between the piston's o-rings and the cylinder. To counteract these disadvantages, we designed a low-priced, novel, fluid percussion apparatus that delivers a pressure pulse of air to a standing column of fluid, forcing it against the intact dural surface. The pressure waveforms generated by this apparatus are similar to those reported in the LFPI/PPBD literature and had little variation in appearance between trials. In addition, our apparatus produced an acute and chronic TBI syndrome similar to that in the LFPI/PPBD literature, as quantified by histological changes, MRI structural changes and chronic behavioral sequelae.
Collapse
|
23
|
Matzen J, Buchheim K, van Landeghem FKH, Meierkord H, Holtkamp M. Functional and morphological changes in the dentate gyrus after experimental status epilepticus. Seizure 2007; 17:76-83. [PMID: 17728157 DOI: 10.1016/j.seizure.2007.07.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2007] [Revised: 06/26/2007] [Accepted: 07/10/2007] [Indexed: 10/22/2022] Open
Abstract
Status epilepticus may cause long-term functional and structural consequences possibly resulting in brain dysfunctions such as chronic epilepsy. In epileptogenesis, the dentate gyrus plays a key role in regulating the excitability of highly vulnerable and potentially epileptogenic downstream structures in the hippocampus proper. One, four and eight weeks after electrically induced status epilepticus, excitability and neuronal degeneration in the rat dentate gyrus were examined with intracerebral electrodes and Fluoro Jade (FJ) staining, respectively. Half of the animals had developed chronic epilepsy by 8 weeks after status epilepticus. Sham-operated controls did not exhibit seizures, and the excitatory parameters remained unchanged. Compared to controls, 8 weeks after status epilepticus the population spike latency in the dentate gyrus was significantly reduced (p<0.05) and substantial neuronal degeneration was seen (p<0.05). In summary, status epilepticus results in functional and morphological alterations in the dentate gyrus likely contributing to epileptogenesis.
Collapse
Affiliation(s)
- Julia Matzen
- Department of Neurology, Charité--Universitätsmedizin Berlin (Campus Mitte), Charitéplatz 1, 10117 Berlin, Germany.
| | | | | | | | | |
Collapse
|
24
|
Echegoyen J, Neu A, Graber KD, Soltesz I. Homeostatic plasticity studied using in vivo hippocampal activity-blockade: synaptic scaling, intrinsic plasticity and age-dependence. PLoS One 2007; 2:e700. [PMID: 17684547 PMCID: PMC1933594 DOI: 10.1371/journal.pone.0000700] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2007] [Accepted: 07/05/2007] [Indexed: 11/18/2022] Open
Abstract
Homeostatic plasticity is thought to be important in preventing neuronal circuits from becoming hyper- or hypoactive. However, there is little information concerning homeostatic mechanisms following in vivo manipulations of activity levels. We investigated synaptic scaling and intrinsic plasticity in CA1 pyramidal cells following 2 days of activity-blockade in vivo in adult (postnatal day 30; P30) and juvenile (P15) rats. Chronic activity-blockade in vivo was achieved using the sustained release of the sodium channel blocker tetrodotoxin (TTX) from the plastic polymer Elvax 40W implanted directly above the hippocampus, followed by electrophysiological assessment in slices in vitro. Three sets of results were in general agreement with previous studies on homeostatic responses to in vitro manipulations of activity. First, Schaffer collateral stimulation-evoked field responses were enhanced after 2 days of in vivo TTX application. Second, miniature excitatory postsynaptic current (mEPSC) amplitudes were potentiated. However, the increase in mEPSC amplitudes occurred only in juveniles, and not in adults, indicating age-dependent effects. Third, intrinsic neuronal excitability increased. In contrast, three sets of results sharply differed from previous reports on homeostatic responses to in vitro manipulations of activity. First, miniature inhibitory postsynaptic current (mIPSC) amplitudes were invariably enhanced. Second, multiplicative scaling of mEPSC and mIPSC amplitudes was absent. Third, the frequencies of adult and juvenile mEPSCs and adult mIPSCs were increased, indicating presynaptic alterations. These results provide new insights into in vivo homeostatic plasticity mechanisms with relevance to memory storage, activity-dependent development and neurological diseases.
Collapse
Affiliation(s)
- Julio Echegoyen
- Department of Anatomy and Neurobiology, University of California at Irvine, California, United States of America.
| | | | | | | |
Collapse
|
25
|
Cater HL, Gitterman D, Davis SM, Benham CD, Morrison B, Sundstrom LE. Stretch-induced injury in organotypic hippocampal slice cultures reproduces in vivo post-traumatic neurodegeneration: role of glutamate receptors and voltage-dependent calcium channels. J Neurochem 2007; 101:434-47. [PMID: 17250683 DOI: 10.1111/j.1471-4159.2006.04379.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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.
Collapse
Affiliation(s)
- Heather L Cater
- Division of Clinical Neurosciences, University of Southampton, Southampton, UK.
| | | | | | | | | | | |
Collapse
|
26
|
Statler KD. Pediatric posttraumatic seizures: epidemiology, putative mechanisms of epileptogenesis and promising investigational progress. Dev Neurosci 2006; 28:354-63. [PMID: 16943659 DOI: 10.1159/000094162] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2005] [Accepted: 03/03/2006] [Indexed: 11/19/2022] Open
Abstract
Posttraumatic seizures and epilepsy are common in children experiencing traumatic brain injury and portend worse functional outcome. Unfortunately, the pathogenesis of pediatric posttraumatic seizures and epilepsy remains poorly understood, and no efficacious preventive therapy for post-traumatic epilepsy has been identified. This article reviews the epidemiology of pediatric posttraumatic seizures, discusses prominent putative mechanisms of posttraumatic epileptogenesis and highlights recent promising progress in experimental investigations of posttraumatic seizures and epilepsy.
Collapse
Affiliation(s)
- Kimberly D Statler
- Division of Critical Care, Department of Pediatrics, The University of Utah School of Medicine, Salt Lake City, Utah 84158-0289, USA.
| |
Collapse
|
27
|
Santhakumar V, Aradi I, Soltesz I. Role of mossy fiber sprouting and mossy cell loss in hyperexcitability: a network model of the dentate gyrus incorporating cell types and axonal topography. J Neurophysiol 2004; 93:437-53. [PMID: 15342722 DOI: 10.1152/jn.00777.2004] [Citation(s) in RCA: 170] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mossy cell loss and mossy fiber sprouting are two characteristic consequences of repeated seizures and head trauma. However, their precise contributions to the hyperexcitable state are not well understood. Because it is difficult, and frequently impossible, to independently examine using experimental techniques whether it is the loss of mossy cells or the sprouting of mossy fibers that leads to dentate hyperexcitability, we built a biophysically realistic and anatomically representative computational model of the dentate gyrus to examine this question. The 527-cell model, containing granule, mossy, basket, and hilar cells with axonal projections to the perforant-path termination zone, showed that even weak mossy fiber sprouting (10-15% of the strong sprouting observed in the pilocarpine model of epilepsy) resulted in the spread of seizure-like activity to the adjacent model hippocampal laminae after focal stimulation of the perforant path. The simulations also indicated that the spatially restricted, lamellar distribution of the sprouted mossy fiber contacts reported in in vivo studies was an important factor in sustaining seizure-like activity in the network. In contrast to the robust hyperexcitability-inducing effects of mossy fiber sprouting, removal of mossy cells resulted in decreased granule cell responses to perforant-path activation in agreement with recent experimental data. These results indicate the crucial role of mossy fiber sprouting even in situations where there is only relatively weak mossy fiber sprouting as is the case after moderate concussive experimental head injury.
Collapse
|