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Cui J, Mivalt F, Sladky V, Kim J, Richner TJ, Lundstrom BN, Van Gompel JJ, Wang HL, Miller KJ, Gregg N, Wu LJ, Denison T, Winter B, Brinkmann BH, Kremen V, Worrell GA. Acute to long-term characteristics of impedance recordings during neurostimulation in humans. J Neural Eng 2024; 21:10.1088/1741-2552/ad3416. [PMID: 38484397 PMCID: PMC11044203 DOI: 10.1088/1741-2552/ad3416] [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: 04/10/2023] [Accepted: 03/14/2024] [Indexed: 03/26/2024]
Abstract
Objective.This study aims to characterize the time course of impedance, a crucial electrophysiological property of brain tissue, in the human thalamus (THL), amygdala-hippocampus, and posterior hippocampus over an extended period.Approach.Impedance was periodically sampled every 5-15 min over several months in five subjects with drug-resistant epilepsy using an investigational neuromodulation device. Initially, we employed descriptive piecewise and continuous mathematical models to characterize the impedance response for approximately three weeks post-electrode implantation. We then explored the temporal dynamics of impedance during periods when electrical stimulation was temporarily halted, observing a monotonic increase (rebound) in impedance before it stabilized at a higher value. Lastly, we assessed the stability of amplitude and phase over the 24 h impedance cycle throughout the multi-month recording.Main results.Immediately post-implantation, the impedance decreased, reaching a minimum value in all brain regions within approximately two days, and then increased monotonically over about 14 d to a stable value. The models accounted for the variance in short-term impedance changes. Notably, the minimum impedance of the THL in the most epileptogenic hemisphere was significantly lower than in other regions. During the gaps in electrical stimulation, the impedance rebound decreased over time and stabilized around 200 days post-implant, likely indicative of the foreign body response and fibrous tissue encapsulation around the electrodes. The amplitude and phase of the 24 h impedance oscillation remained stable throughout the multi-month recording, with circadian variation in impedance dominating the long-term measures.Significance.Our findings illustrate the complex temporal dynamics of impedance in implanted electrodes and the impact of electrical stimulation. We discuss these dynamics in the context of the known biological foreign body response of the brain to implanted electrodes. The data suggest that the temporal dynamics of impedance are dependent on the anatomical location and tissue epileptogenicity. These insights may offer additional guidance for the delivery of therapeutic stimulation at various time points post-implantation for neuromodulation therapy.
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Affiliation(s)
- Jie Cui
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
- Mayo College of Medicine and Science, Mayo Clinic, Rochester, Minnesota, USA
| | - Filip Mivalt
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czech Republic
- International Clinical Research Center, St. Anne’s University Hospital, Brno, Czech Republic
| | - Vladimir Sladky
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
- International Clinical Research Center, St. Anne’s University Hospital, Brno, Czech Republic
- Faculty of Biomedical Engineering, Czech Technical University in Prague, Kladno, Czech Republic
| | - Jiwon Kim
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
| | | | | | | | - Hai-long Wang
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
| | - Kai J. Miller
- Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, USA
| | - Nicholas Gregg
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
| | - Long Jun Wu
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
| | - Timothy Denison
- Department of Engineering Science, University of Oxford; MRC Brain Network Dynamics Unit, University of Oxford, OX3 7DQ UK
| | - Bailey Winter
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
- Mayo College of Medicine and Science, Mayo Clinic, Rochester, Minnesota, USA
| | - Benjamin H. Brinkmann
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Vaclav Kremen
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
- Czech Institute of Informatics, Robotics, and Cybernetics, Czech Technical University, Prague, Czech Republic
| | - Gregory A. Worrell
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
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Mazzitelli M, Ponomareva O, Presto P, John J, Neugebauer V. Impaired amygdala astrocytic signaling worsens neuropathic pain-associated neuronal functions and behaviors. Front Pharmacol 2024; 15:1368634. [PMID: 38576475 PMCID: PMC10991799 DOI: 10.3389/fphar.2024.1368634] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Accepted: 03/06/2024] [Indexed: 04/06/2024] Open
Abstract
Introduction: Pain is a clinically relevant health care issue with limited therapeutic options, creating the need for new and improved analgesic strategies. The amygdala is a limbic brain region critically involved in the regulation of emotional-affective components of pain and in pain modulation. The central nucleus of amygdala (CeA) serves major output functions and receives nociceptive information via the external lateral parabrachial nucleus (PB). While amygdala neuroplasticity has been linked causally to pain behaviors, non-neuronal pain mechanisms in this region remain to be explored. As an essential part of the neuroimmune system, astrocytes that represent about 40-50% of glia cells within the central nervous system, are required for physiological neuronal functions, but their role in the amygdala remains to be determined for pain conditions. In this study, we measured time-specific astrocyte activation in the CeA in a neuropathic pain model (spinal nerve ligation, SNL) and assessed the effects of astrocyte inhibition on amygdala neuroplasticity and pain-like behaviors in the pain condition. Methods and Results: Glial fibrillary acidic protein (GFAP, astrocytic marker) immunoreactivity and mRNA expression were increased at the chronic (4 weeks post-SNL), but not acute (1 week post-SNL), stage of neuropathic pain. In order to determine the contribution of astrocytes to amygdala pain-mechanisms, we used fluorocitric acid (FCA), a selective inhibitor of astrocyte metabolism. Whole-cell patch-clamp recordings were performed from neurons in the laterocapsular division of the CeA (CeLC) obtained from chronic neuropathic rats. Pre-incubation of brain slices with FCA (100 µM, 1 h), increased excitability through altered hyperpolarization-activated current (Ih) functions, without significantly affecting synaptic responses at the PB-CeLC synapse. Intra-CeA injection of FCA (100 µM) had facilitatory effects on mechanical withdrawal thresholds (von Frey and paw pressure tests) and emotional-affective behaviors (evoked vocalizations), but not on facial grimace score and anxiety-like behaviors (open field test), in chronic neuropathic rats. Selective inhibition of astrocytes by FCA was confirmed with immunohistochemical analyses showing decreased astrocytic GFAP, but not NeuN, signal in the CeA. Discussion: Overall, these results suggest a complex modulation of amygdala pain functions by astrocytes and provide evidence for beneficial functions of astrocytes in CeA in chronic neuropathic pain.
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Affiliation(s)
- Mariacristina Mazzitelli
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, United States
| | - Olga Ponomareva
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, United States
| | - Peyton Presto
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, United States
| | - Julia John
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, United States
| | - Volker Neugebauer
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, United States
- Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center, Lubbock, TX, United States
- Garrison Institute on Aging, Texas Tech University Health Sciences Center, Lubbock, TX, United States
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Fringuello AR, Colbourn R, Goodman JH, Michelson HB, Ling DSF, Hrabetova S. Rapid volume pulsations of the extracellular space accompany epileptiform activity in trauma-injured neocortex and depend on the sodium-bicarbonate cotransporter NBCe1. Epilepsy Res 2024; 201:107337. [PMID: 38461594 DOI: 10.1016/j.eplepsyres.2024.107337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 02/19/2024] [Accepted: 02/29/2024] [Indexed: 03/12/2024]
Abstract
Post traumatic epilepsy (PTE) is a treatment-resistant consequence of traumatic brain injury (TBI). Recently, it has been revealed that epileptiform activity in acute chemoconvulsant seizure models is accompanied by transient shrinkages of extracellular space (ECS) called rapid volume pulsations (RVPs). Shrinkage of the ECS surrounding neurons and glia may contribute to ictogenic hyperexcitability and hypersynchrony during the chronic phase of TBI. Here, we identify the phenomenon of RVPs occurring spontaneously in rat neocortex at ≥ 3 weeks after injury in the controlled cortical impact (CCI) model for PTE. We further report that blocking the electrogenic action of the astrocytic cotransporter NBCe1 with 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid (DIDS) eliminates both RVPs and epileptiform activity in ex-vivo CCI neocortical brain slices. We conclude that NBCe1-mediated extracellular volume shrinkage may represent a new target for therapeutic intervention in PTE.
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Affiliation(s)
- Anthony R Fringuello
- Department of Cell Biology, SUNY Downstate Health Sciences University, Brooklyn, NY, USA; Neural and Behavioral Science Graduate Program, SUNY Downstate Health Sciences University, Brooklyn, NY, USA
| | - Robert Colbourn
- Department of Cell Biology, SUNY Downstate Health Sciences University, Brooklyn, NY, USA; Neural and Behavioral Science Graduate Program, SUNY Downstate Health Sciences University, Brooklyn, NY, USA; Present address: Department of Pathology and Laboratory Medicine, Hospital of the University of Pennsylvania, Philadelphia, PA, USA
| | - Jeffrey H Goodman
- Department of Developmental Neurobiology, The New York State Institute for Basic Research in Developmental Disabilities, Staten Island, NY, USA; Department of Physiology and Pharmacology, SUNY Downstate Health Sciences University, Brooklyn, NY, USA; The Robert F. Furchgott Center for Neural and Behavioral Science, SUNY Downstate Health Sciences University, Brooklyn, NY, USA
| | - Hillary B Michelson
- Department of Physiology and Pharmacology, SUNY Downstate Health Sciences University, Brooklyn, NY, USA; The Robert F. Furchgott Center for Neural and Behavioral Science, SUNY Downstate Health Sciences University, Brooklyn, NY, USA
| | - Douglas S F Ling
- Department of Physiology and Pharmacology, SUNY Downstate Health Sciences University, Brooklyn, NY, USA; The Robert F. Furchgott Center for Neural and Behavioral Science, SUNY Downstate Health Sciences University, Brooklyn, NY, USA
| | - Sabina Hrabetova
- Department of Cell Biology, SUNY Downstate Health Sciences University, Brooklyn, NY, USA; The Robert F. Furchgott Center for Neural and Behavioral Science, SUNY Downstate Health Sciences University, Brooklyn, NY, USA.
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Cui J, Mivalt F, Sladky V, Kim J, Richner TJ, Lundstrom BN, Van Gompel JJ, Wang HL, Miller KJ, Gregg N, Wu LJ, Denison T, Winter B, Brinkmann BH, Kremen V, Worrell GA. Acute to long-term characteristics of impedance recordings during neurostimulation in humans. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2024:2024.01.23.24301672. [PMID: 38343858 PMCID: PMC10854350 DOI: 10.1101/2024.01.23.24301672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/17/2024]
Abstract
Objective This study aims to characterize the time course of impedance, a crucial electrophysiological property of brain tissue, in the human thalamus (THL), amygdala-hippocampus (AMG-HPC), and posterior hippocampus (post-HPC) over an extended period. Approach Impedance was periodically sampled every 5-15 minutes over several months in five subjects with drug-resistant epilepsy using an experimental neuromodulation device. Initially, we employed descriptive piecewise and continuous mathematical models to characterize the impedance response for approximately three weeks post-electrode implantation. We then explored the temporal dynamics of impedance during periods when electrical stimulation was temporarily halted, observing a monotonic increase (rebound) in impedance before it stabilized at a higher value. Lastly, we assessed the stability of amplitude and phase over the 24-hour impedance cycle throughout the multi-month recording. Main results Immediately post-implantation, the impedance decreased, reaching a minimum value in all brain regions within approximately two days, and then increased monotonically over about 14 days to a stable value. The models accounted for the variance in short-term impedance changes. Notably, the minimum impedance of the THL in the most epileptogenic hemisphere was significantly lower than in other regions. During the gaps in electrical stimulation, the impedance rebound decreased over time and stabilized around 200 days post-implant, likely indicative of the foreign body response and fibrous tissue encapsulation around the electrodes. The amplitude and phase of the 24-hour impedance oscillation remained stable throughout the multi-month recording, with circadian variation in impedance dominating the long-term measures. Significance Our findings illustrate the complex temporal dynamics of impedance in implanted electrodes and the impact of electrical stimulation. We discuss these dynamics in the context of the known biological foreign body response of the brain to implanted electrodes. The data suggest that the temporal dynamics of impedance are dependent on the anatomical location and tissue epileptogenicity. These insights may offer additional guidance for the delivery of therapeutic stimulation at various time points post-implantation for neuromodulation therapy.
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Affiliation(s)
- Jie Cui
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
- Mayo College of Medicine and Science, Mayo Clinic, Rochester, Minnesota, USA
| | - Filip Mivalt
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czech Republic
- International Clinical Research Center, St. Anne’s University Hospital, Brno, Czech Republic
| | - Vladimir Sladky
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
- International Clinical Research Center, St. Anne’s University Hospital, Brno, Czech Republic
- Faculty of Biomedical Engineering, Czech Technical University in Prague, Kladno, Czech Republic
| | - Jiwon Kim
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
| | | | | | | | - Hai-long Wang
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
| | - Kai J. Miller
- Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, USA
| | - Nicholas Gregg
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
| | - Long Jun Wu
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
| | - Timothy Denison
- Department of Engineering Science, University of Oxford; MRC Brain Network Dynamics Unit, University of Oxford, OX3 7DQ UK
| | - Bailey Winter
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
- Mayo College of Medicine and Science, Mayo Clinic, Rochester, Minnesota, USA
| | - Benjamin H. Brinkmann
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Vaclav Kremen
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
- Czech Institute of Informatics, Robotics, and Cybernetics, Czech Technical University, Prague, Czech Republic
| | - Gregory A. Worrell
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
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Gaspard N. Magnetic Resonance Imaging in Status Epilepticus: Useful Scrying Board or Expensive Stopwatch? Epilepsy Curr 2023. [DOI: 10.1177/15357597231160608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023] Open
Abstract
[Box: see text]
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Pawlik M, Czarnecka AM, Kołodziej M, Skowrońska K, Węgrzynowicz M, Podgajna M, Czuczwar SJ, Albrecht J. Attenuation of initial pilocarpine-induced electrographic seizures by methionine sulfoximine pretreatment tightly correlates with the reduction of extracellular taurine in the hippocampus. Epilepsia 2023; 64:1390-1402. [PMID: 36808593 DOI: 10.1111/epi.17554] [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: 11/22/2022] [Revised: 02/16/2023] [Accepted: 02/16/2023] [Indexed: 02/20/2023]
Abstract
OBJECTIVE Initiation and development of early seizures by chemical stimuli is associated with brain cell swelling resulting in edema of seizure-vulnerable brain regions. We previously reported that pretreatment with a nonconvulsive dose of glutamine (Gln) synthetase inhibitor methionine sulfoximine (MSO) mitigates the intensity of initial pilocarpine (Pilo)-induced seizures in juvenile rats. We hypothesized that MSO exerts its protective effect by preventing the seizure-initiating and seizure-propagating increase of cell volume. Taurine (Tau) is an osmosensitive amino acid, whose release reflects increased cell volume. Therefore, we tested whether the poststimulus rise of amplitude of Pilo-induced electrographic seizures and their attenuation by MSO are correlated with the release of Tau from seizure-affected hippocampus. METHODS Lithium-pretreated animals were administered MSO (75 mg/kg ip) 2.5 h before the induction of convulsions by Pilo (40 mg/kg ip). Electroencephalographic (EEG) power was analyzed during 60 min post-Pilo, at 5-min intervals. Extracellular accumulation of Tau (eTau) served as a marker of cell swelling. eTau, extracellular Gln (eGln), and extracellular glutamate (eGlu) were assayed in the microdialysates of the ventral hippocampal CA1 region collected at 15-min intervals during the whole 3.5-h observation period. RESULTS The first EEG signal became apparent at ~10 min post-Pilo. The EEG amplitude across most frequency bands peaked at ~40 min post-Pilo, and showed strong (r ~ .72-.96) temporal correlation with eTau, but no correlation with eGln or eGlu. MSO pretreatment delayed the first EEG signal in Pilo-treated rats by ~10 min, and depressed the EEG amplitude across most frequency bands, to values that remained strongly correlated with eTau (r > .92) and moderately correlated (r ~ -.59) with eGln, but not with eGlu. SIGNIFICANCE Strong correlation between attenuation of Pilo-induced seizures and Tau release indicates that the beneficial effect of MSO is due to the prevention of cell volume increase concurrent with the onset of seizures.
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Affiliation(s)
- Marek Pawlik
- Department of Neurotoxicology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Warsaw, Poland
| | - Anna Maria Czarnecka
- Department of Neurotoxicology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Warsaw, Poland
| | - Marcin Kołodziej
- Institute of Theory of Electrical Engineering, Measurement, and Information Systems, Warsaw University of Technology, Warsaw, Poland
| | - Katarzyna Skowrońska
- Department of Neurotoxicology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Warsaw, Poland
| | - Michał Węgrzynowicz
- Laboratory of Molecular Basis of Neurodegeneration, Mossakowski Medical Research Institute, Polish Academy of Sciences, Warsaw, Poland
| | - Martyna Podgajna
- Laboratory of Molecular Basis of Neurodegeneration, Mossakowski Medical Research Institute, Polish Academy of Sciences, Warsaw, Poland
| | | | - Jan Albrecht
- Department of Neurotoxicology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Warsaw, Poland
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From spreading depolarization to epilepsy with neuroinflammation: The role of CGRP in cortex. Exp Neurol 2022; 356:114152. [PMID: 35760098 DOI: 10.1016/j.expneurol.2022.114152] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 06/03/2022] [Accepted: 06/18/2022] [Indexed: 11/23/2022]
Abstract
CGRP release plays a major role in migraine pain by activating the trigeminal pain pathways. Here we explored putative additional effects of CGRP on cortical circuits and investigated whether CGRP affects cortical excitability, cortical spreading depolarization (CSD), a phenomenon associated with migraine aura, blood-brain-barrier (BBB) and microglial morphology. We used immunohistochemistry to localize CGRP and the CGRP receptor (CGRP-R) in native cortex and evaluated morphology of microglia and integrity of the BBB after exposure to CGRP. In anesthetized rats we applied CGRP and the CGRP-R antagonist BIBN4096BS locally to the exposed cortex and monitored the spontaneous electrocorticogram and CSDs evoked by remote KCl pressure microinjection. In mouse brain slices CGRP effects on neuronal activity were explored by multielectrode array. CGRP immunoreactivity was detectable in intracortical vessels, and all cortical neurons showed CGRP-R immunoreactivity. In rat cortex in vivo, topical CGRP induced periods of epileptiform discharges, however, also dose-dependently reduced CSD amplitudes and propagation velocity. BIBN4096BS prevented these effects. CGRP evoked synchronized bursting activity in mouse cortical but not in cerebellar slices. Topical application of CGRP to rat cortex induced plasma extravasation and this was associated with reduced ramification of microglial cells. From these findings we conclude that CGRP induces a pathophysiological state in the cortex, consisting in neuronal hyperexcitability and neuroinflammation Thus, CGRP may have a pronounced impact on brain functions during migraine episodes supporting the benefit of CGRP antagonists for clinical use. However, increased cortical CGRP may end the CSD-induced aura phase of migraine.
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Nonperiodic stimulation for the treatment of refractory epilepsy: Applications, mechanisms, and novel insights. Epilepsy Behav 2021; 121:106609. [PMID: 31704250 DOI: 10.1016/j.yebeh.2019.106609] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2019] [Revised: 10/14/2019] [Accepted: 10/14/2019] [Indexed: 11/21/2022]
Abstract
Electrical stimulation of the central nervous system is a promising alternative for the treatment of pharmacoresistant epilepsy. Successful clinical and experimental stimulation is most usually carried out as continuous trains of current or voltage pulses fired at rates of 100 Hz or above, since lower frequencies yield controversial results. On the other hand, stimulation frequency should be as low as possible, in order to maximize implant safety and battery efficiency. Moreover, the development of stimulation approaches has been largely empirical in general, while they should be engineered with the neurobiology of epilepsy in mind if a more robust, efficient, efficacious, and safe application is intended. In an attempt to reconcile evidence of therapeutic effect with the understanding of the underpinnings of epilepsy, our group has developed a nonstandard form of low-frequency stimulation with randomized interpulse intervals termed nonperiodic stimulation (NPS). The rationale was that an irregular temporal pattern would impair neural hypersynchronization, which is a hallmark of epilepsy. In this review, we start by briefly revisiting the literature on the molecular, cellular, and network level mechanisms of epileptic phenomena in order to highlight this often-overlooked emergent property of cardinal importance in the pathophysiology of the disease. We then review our own studies on the efficacy of NPS against acute and chronic experimental seizures and also on the anatomical and physiological mechanism of the method, paying special attention to the hypothesis that the lack of temporal regularity induces desynchronization. We also put forward a novel insight regarding the temporal structure of NPS that may better encompass the set of findings published by the group: the fact that intervals between stimulation pulses have a distribution that follows a power law and thus may induce natural-like activity that would compete with epileptiform discharge for the recruitment of networks. We end our discussion by mentioning ongoing research and future projects of our lab.
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Wu L, Ji NN, Wang H, Hua JY, Sun GL, Chen PP, Hua R, Zhang YM. Domino Effect of Interleukin-15 and CD8 T-Cell-Mediated Neuronal Apoptosis in Experimental Traumatic Brain Injury. J Neurotrauma 2021; 38:1450-1463. [PMID: 30430911 DOI: 10.1089/neu.2017.5607] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The effects of local factors on activation of immune cells infiltrating the central nervous system (CNS) in a rat model of traumatic brain injury (TBI) remain elusive. The cytokine, interleukin (IL)-15, is crucial for development and activation of CD8 T lymphocytes, a prominent lymphocytic population present in TBI lesions. We investigated whether IL-15 originates from astrocytes and whether IL-15 can evoke the CD8 T-lymphocyte response in TBI. We observed that astrocytes were activated in a rat model of TBI and that IL-15 was overexpressed on the surface of astrocytes. Further, CD8 T lymphocytes infiltrating TBI lesions colocalized with IL-15-expressing astrocytes. Activated CD8 T lymphocytes released granzyme B (Gra-b), which, in turn, activated caspase-3-induced poly(ADP-ribose) polymerase cleavage and, ultimately, neuronal apoptosis. Conversely, inhibition of astrocyte activation by pre-treatment with the specific inhibitor, fluorocitrate (FC), that reduces carbon flux through the Krebs cycle in astrocytes resulted in improved neurological function and memory. FC pre-treatment was also associated with downregulated IL-15 expression and CD8 T-cell activation as well as decreased levels of neuronal apoptosis, suggesting that IL-15 initiated a domino effect toward apoptosis. In contrast, rats pre-treated with recombinant rat IL-15 showed upregulated CD8 T-cell numbers and Gra-b levels, in addition to induction of neuronal apoptosis. Together, our results indicated that IL-15 could induce neuronal apoptosis by enhancing CD8 T-cell function in a rat model of TBI.
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Affiliation(s)
- Liang Wu
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, China.,Department of Anesthesiology, Xuzhou Municipal Hospital Affiliated with Xuzhou Medical University, Xuzhou, China
| | - Ning-Ning Ji
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, China.,Department of Anesthesiology, Xuzhou Municipal Hospital Affiliated with Xuzhou Medical University, Xuzhou, China
| | - Hang Wang
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, China
| | - Jing-Yu Hua
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, China
| | - Guo-Lin Sun
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, China
| | - Pan-Pan Chen
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, China
| | - Rong Hua
- Faculty of Emergency Rescue Medicine, Xuzhou Medical University, Xuzhou, China.,Emergency Center of the Affiliated Hospital of Xuzhou Medical University, Xuzhou, China
| | - Yong-Mei Zhang
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, China
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Avery J, Dowrick T, Witkowska-Wrobel A, Faulkner M, Aristovich K, Holder D. Simultaneous EIT and EEG using frequency division multiplexing. Physiol Meas 2019; 40:034007. [DOI: 10.1088/1361-6579/ab0bbc] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Hannan S, Faulkner M, Aristovich K, Avery J, Walker M, Holder D. Imaging fast electrical activity in the brain during ictal epileptiform discharges with electrical impedance tomography. NEUROIMAGE-CLINICAL 2018; 20:674-684. [PMID: 30218899 PMCID: PMC6140294 DOI: 10.1016/j.nicl.2018.09.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 07/27/2018] [Accepted: 09/02/2018] [Indexed: 12/19/2022]
Abstract
Electrical Impedance Tomography (EIT) is an emerging medical imaging technique which can produce tomographic images of internal impedance changes within an object using non-penetrating surface electrodes. It has previously been used to image impedance changes due to neuronal depolarisation during evoked potentials in the rat somatosensory cortex with a resolution of 2 ms and <200 μm, using an epicortical electrode array. The purpose of this work was to use this technique to elucidate the intracortical spatiotemporal trajectory of ictal spike-and-wave discharges (SWDs), induced by electrical stimulation in an acute rat model of epilepsy, throughout the cerebral cortex. Seizures lasting 16.5 ± 5.3 s with repetitive 2-5 Hz SWDs were induced in five rats anaesthetised with fentanyl-isoflurane. Transfer impedance measurements were obtained during each seizure with a 57-electrode epicortical array by applying 50 μA current at 1.7 kHz to two electrodes and recording voltages from all remaining electrodes. Images were reconstructed from averaged SWD-related impedance traces obtained from EIT measurements in successive seizures. We report the occurrence of reproducible impedance changes during the initial spike phase, which had an early onset in the whisker barrel cortex and spread posteriorly, laterally and ventrally over 20 ms (p < 0.03125, N = 5). These findings, which confirm and extend knowledge of SWD initiation and expression, suggest that EIT is a valuable neuroimaging tool for improving understanding of neural circuits implicated in epileptic phenomena.
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Affiliation(s)
- Sana Hannan
- Department of Medical Physics and Biomedical Engineering, University College London, UK.
| | - Mayo Faulkner
- Department of Medical Physics and Biomedical Engineering, University College London, UK
| | - Kirill Aristovich
- Department of Medical Physics and Biomedical Engineering, University College London, UK
| | - James Avery
- Department of Medical Physics and Biomedical Engineering, University College London, UK
| | | | - David Holder
- Department of Medical Physics and Biomedical Engineering, University College London, UK
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Hannan S, Faulkner M, Aristovich K, Avery J, Holder D. Frequency-dependent characterisation of impedance changes during epileptiform activity in a rat model of epilepsy. Physiol Meas 2018; 39:085003. [DOI: 10.1088/1361-6579/aad5f4] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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13
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Turning down the volume: Astrocyte volume change in the generation and termination of epileptic seizures. Neurobiol Dis 2017; 104:24-32. [PMID: 28438505 DOI: 10.1016/j.nbd.2017.04.016] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 04/18/2017] [Accepted: 04/20/2017] [Indexed: 12/20/2022] Open
Abstract
Approximately 1% of the global population suffers from epilepsy, a class of disorders characterized by recurrent and unpredictable seizures. Of these cases roughly one-third are refractory to current antiepileptic drugs, which typically target neuronal excitability directly. The events leading to seizure generation and epileptogenesis remain largely unknown, hindering development of new treatments. Some recent experimental models of epilepsy have provided compelling evidence that glial cells, especially astrocytes, could be central to seizure development. One of the proposed mechanisms for astrocyte involvement in seizures is astrocyte swelling, which may promote pathological neuronal firing and synchrony through reduction of the extracellular space and elevated glutamate concentrations. In this review, we discuss the common conditions under which astrocytes swell, the resultant effects on neural excitability, and how seizure development may ultimately be influenced by these effects.
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Cota VR, Drabowski BMB, de Oliveira JC, Moraes MFD. The epileptic amygdala: Toward the development of a neural prosthesis by temporally coded electrical stimulation. J Neurosci Res 2017; 94:463-85. [PMID: 27091311 DOI: 10.1002/jnr.23741] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 03/09/2016] [Accepted: 03/09/2016] [Indexed: 02/06/2023]
Abstract
Many patients with epilepsy do not obtain proper control of their seizures through conventional treatment. We review aspects of the pathophysiology underlying epileptic phenomena, with a special interest in the role of the amygdala, stressing the importance of hypersynchronism in both ictogenesis and epileptogenesis. We then review experimental studies on electrical stimulation of mesiotemporal epileptogenic areas, the amygdala included, as a means to treat medically refractory epilepsy. Regular high-frequency stimulation (HFS) commonly has anticonvulsant effects and sparse antiepileptogenic properties. On the other hand, HFS is related to acute and long-term increases in excitability related to direct neuronal activation, long-term potentiation, and kindling, raising concerns regarding its safety and jeopardizing in-depth understanding of its mechanisms. In turn, the safer regular low-frequency stimulation (LFS) has a robust antiepileptogenic effect, but its pro- or anticonvulsant effect seems to vary at random among studies. As an alternative, studies by our group on the development and investigation of temporally unstructured electrical stimulation applied to the amygdala have shown that nonperiodic stimulation (NPS), which is a nonstandard form of LFS, is capable of suppressing both acute and chronic spontaneous seizures. We hypothesize two noncompetitive mechanisms for the therapeutic role of amygdala in NPS, 1) a direct desynchronization of epileptic circuitry in the forebrain and brainstem and 2) an indirect desynchronization/inhibition through nucleus accumbens activation. We conclude by reintroducing the idea that hypersynchronism, rather than hyperexcitability, may be the key for epileptic phenomena and epilepsy treatment.
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Affiliation(s)
- Vinícius Rosa Cota
- Laboratório Interdisciplinar de Neuroengenharia e Neurociências, Departamento de Engenharia Elétrica (DEPEL), Universidade Federal de São João Del-Rei, São João Del-Rei, Minas Gerais, Brazil
| | - Bruna Marcela Bacellar Drabowski
- Laboratório Interdisciplinar de Neuroengenharia e Neurociências, Departamento de Engenharia Elétrica (DEPEL), Universidade Federal de São João Del-Rei, São João Del-Rei, Minas Gerais, Brazil
| | - Jasiara Carla de Oliveira
- Laboratório Interdisciplinar de Neuroengenharia e Neurociências, Departamento de Engenharia Elétrica (DEPEL), Universidade Federal de São João Del-Rei, São João Del-Rei, Minas Gerais, Brazil
| | - Márcio Flávio Dutra Moraes
- Núcleo de Neurociências, Instituto de Ciências Biológicas (ICB), Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
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15
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Haenisch S, von Rüden EL, Wahmkow H, Rettenbeck ML, Michler C, Russmann V, Bruckmueller H, Waetzig V, Cascorbi I, Potschka H. miRNA-187-3p-Mediated Regulation of the KCNK10/TREK-2 Potassium Channel in a Rat Epilepsy Model. ACS Chem Neurosci 2016; 7:1585-1594. [PMID: 27609046 DOI: 10.1021/acschemneuro.6b00222] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Regulatory RNAs play a key role in the regulation of protein expression patterns in neurological diseases. Here we studied the regulation of miRNAs in a chronic rat model of temporal lobe epilepsy. The analysis was focused on a putative link with pharmacoresponsiveness as well as the functional implications of the regulation of a selected miRNA. The findings did not reveal a difference in hippocampal miRNA expression between phenobarbital responders and nonresponders. However, when comparing rats following status epilepticus with control rats we identified 13 differentially expressed miRNAs with miRNA-187-3p being most strongly regulated. mRNAs encoding KCNK10/TREK-2 as well as DYRK2 were confirmed as targets of miRNA-187-3p. Expression of the potassium channel protein KCNK10/TREK-2 negatively correlated with hippocampal miRNA-187-3p expression and proved to be upregulated in the chronic phase of the epilepsy model. In conclusion, our data do not suggest a relevant impact of miRNA expression patterns on pharmacoresponsiveness. However, we confirmed regulation of miRNA-187-3p and demonstrated that it impacts the expression of the two-pore domain potassium channel protein KCNK10/TREK-2. Considering evidence from brain ischemia models, KCNK10/TREK-2 upregulation might serve a protective function with a beneficial impact on astrocytic potassium and glutamate homeostasis.
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Affiliation(s)
- Sierk Haenisch
- Institute of Experimental and Clinical Pharmacology, University Hospital Schleswig-Holstein , 24105 Campus Kiel, Germany
| | - Eva-Lotta von Rüden
- Institute of Pharmacology, Toxicology, and Pharmacy, Ludwig-Maximilians-University (LMU) , 80539 Munich, Germany
| | - Hannes Wahmkow
- Institute of Experimental and Clinical Pharmacology, University Hospital Schleswig-Holstein , 24105 Campus Kiel, Germany
| | - Maruja L Rettenbeck
- Institute of Pharmacology, Toxicology, and Pharmacy, Ludwig-Maximilians-University (LMU) , 80539 Munich, Germany
| | - Christina Michler
- Institute of Pharmacology, Toxicology, and Pharmacy, Ludwig-Maximilians-University (LMU) , 80539 Munich, Germany
| | - Vera Russmann
- Institute of Pharmacology, Toxicology, and Pharmacy, Ludwig-Maximilians-University (LMU) , 80539 Munich, Germany
| | - Henrike Bruckmueller
- Institute of Experimental and Clinical Pharmacology, University Hospital Schleswig-Holstein , 24105 Campus Kiel, Germany
| | - Vicki Waetzig
- Institute of Experimental and Clinical Pharmacology, University Hospital Schleswig-Holstein , 24105 Campus Kiel, Germany
| | - Ingolf Cascorbi
- Institute of Experimental and Clinical Pharmacology, University Hospital Schleswig-Holstein , 24105 Campus Kiel, Germany
| | - Heidrun Potschka
- Institute of Pharmacology, Toxicology, and Pharmacy, Ludwig-Maximilians-University (LMU) , 80539 Munich, Germany
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Lauderdale K, Murphy T, Tung T, Davila D, Binder DK, Fiacco TA. Osmotic Edema Rapidly Increases Neuronal Excitability Through Activation of NMDA Receptor-Dependent Slow Inward Currents in Juvenile and Adult Hippocampus. ASN Neuro 2015; 7:7/5/1759091415605115. [PMID: 26489684 PMCID: PMC4623564 DOI: 10.1177/1759091415605115] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Cellular edema (cell swelling) is a principal component of numerous brain disorders including ischemia, cortical spreading depression, hyponatremia, and epilepsy. Cellular edema increases seizure-like activity in vitro and in vivo, largely through nonsynaptic mechanisms attributable to reduction of the extracellular space. However, the types of excitability changes occurring in individual neurons during the acute phase of cell volume increase remain unclear. Using whole-cell patch clamp techniques, we report that one of the first effects of osmotic edema on excitability of CA1 pyramidal cells is the generation of slow inward currents (SICs), which initiate after approximately 1 min. Frequency of SICs increased as osmolarity decreased in a dose-dependent manner. Imaging of real-time volume changes in astrocytes revealed that neuronal SICs occurred while astrocytes were still in the process of swelling. SICs evoked by cell swelling were mainly nonsynaptic in origin and NMDA receptor-dependent. To better understand the relationship between SICs and changes in neuronal excitability, recordings were performed in increasingly physiological conditions. In the absence of any added pharmacological reagents or imposed voltage clamp, osmotic edema induced excitatory postsynaptic potentials and burst firing over the same timecourse as SICs. Like SICs, action potentials were blocked by NMDAR antagonists. Effects were more pronounced in adult (8-20 weeks old) compared with juvenile (P15-P21) mice. Together, our results indicate that cell swelling triggered by reduced osmolarity rapidly increases neuronal excitability through activation of NMDA receptors. Our findings have important implications for understanding nonsynaptic mechanisms of epilepsy in relation to cell swelling and reduction of the extracellular space.
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Affiliation(s)
- Kelli Lauderdale
- Department of Cell Biology and Neuroscience, Riverside, CA, USA Center for Glial-Neuronal Interactions, University of California Riverside, CA, USA
| | - Thomas Murphy
- Department of Cell Biology and Neuroscience, Riverside, CA, USA Center for Glial-Neuronal Interactions, University of California Riverside, CA, USA
| | - Tina Tung
- Department of Cell Biology and Neuroscience, Riverside, CA, USA
| | - David Davila
- Department of Cell Biology and Neuroscience, Riverside, CA, USA
| | - Devin K Binder
- Center for Glial-Neuronal Interactions, University of California Riverside, CA, USA Division of Biomedical Sciences, UC Riverside School of Medicine, CA, USA
| | - Todd A Fiacco
- Department of Cell Biology and Neuroscience, Riverside, CA, USA Center for Glial-Neuronal Interactions, University of California Riverside, CA, USA
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17
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Vongerichten AN, Santos GSD, Aristovich K, Avery J, McEvoy A, Walker M, Holder DS. Characterisation and imaging of cortical impedance changes during interictal and ictal activity in the anaesthetised rat. Neuroimage 2015; 124:813-823. [PMID: 26375207 PMCID: PMC4655942 DOI: 10.1016/j.neuroimage.2015.09.015] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 08/16/2015] [Accepted: 09/07/2015] [Indexed: 11/18/2022] Open
Abstract
Epilepsy affects approximately 50 million people worldwide, and 20–30% of these cases are refractory to antiepileptic drugs. Many patients with intractable epilepsy can benefit from surgical resection of the tissue generating the seizures; however, difficulty in precisely localising seizure foci has limited the number of patients undergoing surgery as well as potentially lowered its effectiveness. Here we demonstrate a novel imaging method for monitoring rapid changes in cerebral tissue impedance occurring during interictal and ictal activity, and show that it can reveal the propagation of pathological activity in the cortex. Cortical impedance was recorded simultaneously to ECoG using a 30-contact electrode mat placed on the exposed cortex of anaesthetised rats, in which interictal spikes (IISs) and seizures were induced by cortical injection of 4-aminopyridine (4-AP), picrotoxin or penicillin. We characterised the tissue impedance responses during IISs and seizures, and imaged these responses in the cortex using Electrical Impedance Tomography (EIT). We found a fast, transient drop in impedance occurring as early as 12 ms prior to the IISs, followed by a steep rise in impedance within ~ 120 ms of the IIS. EIT images of these impedance changes showed that they were co-localised and centred at a depth of 1 mm in the cortex, and that they closely followed the activity propagation observed in the surface ECoG signals. The fast, pre-IIS impedance drop most likely reflects synchronised depolarisation in a localised network of neurons, and the post-IIS impedance increase reflects the subsequent shrinkage of extracellular space caused by the intense activity. EIT could also be used to picture a steady rise in tissue impedance during seizure activity, which has been previously described. Thus, our results demonstrate that EIT can detect and localise different physiological changes during interictal and ictal activity and, in conjunction with ECoG, may in future improve the localisation of seizure foci in the clinical setting. Cortical impedance was measured simultaneously to EEG during epileptic activity. Interictal spikes were preceded by fast decreases in cortical impedance. Steep increases in impedance followed both interictal spikes and onset of ictal activity. Imaging with Electrical Impedance Tomography revealed the location of epilepsy-related impedance changes.
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Affiliation(s)
- Anna N Vongerichten
- Dept. of Medical Physics and Biomedical Engineering, University College London, UK.
| | | | - Kirill Aristovich
- Dept. of Medical Physics and Biomedical Engineering, University College London, UK
| | - James Avery
- Dept. of Medical Physics and Biomedical Engineering, University College London, UK
| | - Andrew McEvoy
- Institute of Neurology, University College London, UK
| | | | - David S Holder
- Dept. of Medical Physics and Biomedical Engineering, University College London, UK
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18
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Naze S, Bernard C, Jirsa V. Computational modeling of seizure dynamics using coupled neuronal networks: factors shaping epileptiform activity. PLoS Comput Biol 2015; 11:e1004209. [PMID: 25970348 PMCID: PMC4430284 DOI: 10.1371/journal.pcbi.1004209] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 02/24/2015] [Indexed: 11/21/2022] Open
Abstract
Epileptic seizure dynamics span multiple scales in space and time. Understanding seizure mechanisms requires identifying the relations between seizure components within and across these scales, together with the analysis of their dynamical repertoire. Mathematical models have been developed to reproduce seizure dynamics across scales ranging from the single neuron to the neural population. In this study, we develop a network model of spiking neurons and systematically investigate the conditions, under which the network displays the emergent dynamic behaviors known from the Epileptor, which is a well-investigated abstract model of epileptic neural activity. This approach allows us to study the biophysical parameters and variables leading to epileptiform discharges at cellular and network levels. Our network model is composed of two neuronal populations, characterized by fast excitatory bursting neurons and regular spiking inhibitory neurons, embedded in a common extracellular environment represented by a slow variable. By systematically analyzing the parameter landscape offered by the simulation framework, we reproduce typical sequences of neural activity observed during status epilepticus. We find that exogenous fluctuations from extracellular environment and electro-tonic couplings play a major role in the progression of the seizure, which supports previous studies and further validates our model. We also investigate the influence of chemical synaptic coupling in the generation of spontaneous seizure-like events. Our results argue towards a temporal shift of typical spike waves with fast discharges as synaptic strengths are varied. We demonstrate that spike waves, including interictal spikes, are generated primarily by inhibitory neurons, whereas fast discharges during the wave part are due to excitatory neurons. Simulated traces are compared with in vivo experimental data from rodents at different stages of the disorder. We draw the conclusion that slow variations of global excitability, due to exogenous fluctuations from extracellular environment, and gap junction communication push the system into paroxysmal regimes. We discuss potential mechanisms underlying such machinery and the relevance of our approach, supporting previous detailed modeling studies and reflecting on the limitations of our methodology. Neurons communicate via different types of synapses on very fast time scales. The combination of hundred thousand of such interconnected cells within a fluctuating extracellular environment forms a complex network that gives rise to function and behavior via the formation of dynamical patterns of activity. In the context of epilepsy, the functional properties of the network at the source of a seizure are disrupted by a possibly large set of factors at the cellular and molecular levels. It is therefore needed to sacrifice some biological accuracy to model seizure dynamics in favor of macroscopic realizations. Here, we present a neuronal network model that convenes both neuronal and network representations with the goal to describe brain dynamics involved in the development of epilepsy. We compare our modeling results with animal in vivo recordings to validate our approach in the context of seizures. Such system-level methodology has significant bearing in understanding neuronal network dynamics that entangle multiple synaptic and extracellular modalities.
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Affiliation(s)
- Sebastien Naze
- UMR1106 Inserm, Institut de Neurosciences des Systèmes, Marseille, France
- Aix-Marseille University, Marseille, France
- * E-mail: (SN); (VJ)
| | - Christophe Bernard
- UMR1106 Inserm, Institut de Neurosciences des Systèmes, Marseille, France
- Aix-Marseille University, Marseille, France
| | - Viktor Jirsa
- UMR1106 Inserm, Institut de Neurosciences des Systèmes, Marseille, France
- Aix-Marseille University, Marseille, France
- * E-mail: (SN); (VJ)
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19
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Karus C, Mondragão MA, Ziemens D, Rose CR. Astrocytes restrict discharge duration and neuronal sodium loads during recurrent network activity. Glia 2015; 63:936-57. [PMID: 25639699 DOI: 10.1002/glia.22793] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Accepted: 01/08/2015] [Indexed: 12/31/2022]
Abstract
Influx of sodium ions into active neurons is a highly energy-expensive process which must be strictly limited. Astrocytes could play an important role herein because they take up glutamate and potassium from the extracellular space, thereby dampening neuronal excitation. Here, we performed sodium imaging in mouse hippocampal slices combined with field potential and whole-cell patch-clamp recordings and measurement of extracellular potassium ([K(+)]o). Network activity was induced by Mg(2+)-free, bicuculline-containing saline, during which neurons showed recurring epileptiform bursting, accompanied by transient increases in [K(+)]o and astrocyte depolarizations. During bursts, neurons displayed sodium increases by up to 22 mM. Astrocyte sodium concentration increased by up to 8.5 mM, which could be followed by an undershoot below baseline. Network sodium oscillations were dependent on action potentials and activation of ionotropic glutamate receptors. Inhibition of glutamate uptake caused acceleration, followed by cessation of electrical activity, irreversible sodium increases, and swelling of neurons. The gliotoxin NaFAc (sodium-fluoroacetate) resulted in elevation of astrocyte sodium concentration and reduced glial uptake of glutamate and potassium uptake through Na(+) /K(+)-ATPase. Moreover, NaFAc extended epileptiform bursts, caused elevation of neuronal sodium, and dramatically prolonged accompanying sodium signals, most likely because of the decreased clearance of glutamate and potassium by astrocytes. Our experiments establish that recurrent neuronal bursting evokes sodium transients in neurons and astrocytes and confirm the essential role of glutamate transporters for network activity. They suggest that astrocytes restrict discharge duration and show that an intact astrocyte metabolism is critical for the neurons' capacity to recover from sodium loads during synchronized activity.
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Affiliation(s)
- Claudia Karus
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Universitätsstrasse 1, D-40225, Düsseldorf, Germany
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20
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Broberg M, Pope KJ, Olsson T, Shuttleworth CW, Willoughby JO. Spreading depression: Evidence of five electroencephalogram phases. J Neurosci Res 2014; 92:1384-94. [DOI: 10.1002/jnr.23412] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2013] [Revised: 03/05/2014] [Accepted: 04/15/2014] [Indexed: 11/11/2022]
Affiliation(s)
- Marita Broberg
- Center for Neuroscience and Department of Neurology; Flinders University; Adelaide South Australia Australia
| | - Kenneth J. Pope
- School of Informatics and Engineering; Flinders University; Adelaide South Australia Australia
| | - Torsten Olsson
- Department of Signals and Systems; Chalmers University of Technology; Göteborg Sweden
| | - C. William Shuttleworth
- Department of Neurosciences; University of New Mexico School of Medicine; Albuquerque New Mexico
| | - John O. Willoughby
- Center for Neuroscience and Department of Neurology; Flinders University; Adelaide South Australia Australia
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21
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Effects of anesthetic agents on seizure-induction with intra-cortical injection of convulsants. Epilepsy Res 2013; 105:52-61. [DOI: 10.1016/j.eplepsyres.2012.12.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Revised: 12/02/2012] [Accepted: 12/13/2012] [Indexed: 11/21/2022]
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Abstract
Great effort has been made toward defining and characterizing the pre-ictal state. Many studies have pursued the idea that there are recognizable electrographic (EEG-based) features which occur before overt clinical seizure activity. However, development of reliable EEG-based seizure detection and prediction algorithms has been difficult. In this review, we discuss the concepts of seizure detection vs. prediction and the pre-ictal "clinical milieu" and "EEG milieu". We proceed to discuss novel concepts of seizure detection based on the pre-ictal "physiological milieu"; in particular, we indicate some early evidence for the hypothesis that pre-ictal cell swelling/extracellular space constriction can be detected with novel optical methods. Development and validation of optical seizure detection technology could provide an entirely new translational approach for the many patients with intractable epilepsy.
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Affiliation(s)
- Devin K. Binder
- Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, University of California, Riverside, CA
| | - Sheryl R. Haut
- Montefiore-Einstein Epilepsy Center, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY
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23
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Das A, Wallace GC, Holmes C, McDowell ML, Smith JA, Marshall JD, Bonilha L, Edwards JC, Glazier SS, Ray SK, Banik NL. Hippocampal tissue of patients with refractory temporal lobe epilepsy is associated with astrocyte activation, inflammation, and altered expression of channels and receptors. Neuroscience 2012; 220:237-46. [PMID: 22698689 DOI: 10.1016/j.neuroscience.2012.06.002] [Citation(s) in RCA: 150] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2012] [Revised: 05/17/2012] [Accepted: 06/03/2012] [Indexed: 11/24/2022]
Abstract
Temporal lobe epilepsy (TLE) is the most common form of focal epilepsy. Previous research has demonstrated several trends in human tissue that, undoubtedly, contribute to the development and progression of TLE. In this study we examined resected human hippocampus tissue for a variety of changes including gliosis that might contribute to the development and presentation of TLE. The study subjects consisted of six TLE patients and three sudden-death controls. Clinicopathological characteristics were evaluated by H&E staining. Immunohistological staining and Western blotting methods were used to analyze the samples. Neuronal hypertrophy was observed in resected epileptic tissue. Immunohistological staining demonstrated that activation of astrocytes was significantly increased in epileptic tissue as compared to corresponding regions of the control group. The Western blot data also showed increased CX43 and AQP4 in the hippocampus and downregulation of Kir4.1, α-syntrophin, and dystrophin, the key constituents of AQP4 multi-molecular complex. These tissues also demonstrated changes in inflammatory factors (COX-2, TGF-β, NF-κB) suggesting that these molecules may play an important role in TLE pathogenesis. In addition we detected increases in metabotropic glutamate receptor (mGluR) 2/3, mGluR5 and kainic acid receptor subunits KA1 (Grik4) and KA2 (Grik5) in patients' hippocampi. We noted increased expression of the α1c subunit comprising class C L-type Ca(2+) channels and calpain expression in these tissues, suggesting that these subunits might have an integral role in TLE pathogenesis. These changes found in the resected tissue suggest that they may contribute to TLE and that the kainic acid receptor (KAR) and deregulation of GluR2 receptor may play an important role in TLE development and disease course. This study identifies alterations in number of commonly studied molecular targets associated with astrogliosis, cellular hypertrophy, water homeostasis, inflammation, and modulation of excitatory neurotransmission in hippocampal tissues from TLE patients.
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Affiliation(s)
- A Das
- Department of Neurosciences (Divisions of Neurology and Neurosurgery), Medical University of South Carolina, Charleston, SC 29425, USA
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Hyzinski-García MC, Vincent MY, Haskew-Layton RE, Dohare P, Keller RW, Mongin AA. Hypo-osmotic swelling modifies glutamate-glutamine cycle in the cerebral cortex and in astrocyte cultures. J Neurochem 2011; 118:140-52. [PMID: 21517854 DOI: 10.1111/j.1471-4159.2011.07289.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
In our previous work, we found that perfusion of the rat cerebral cortex with hypo-osmotic medium triggers massive release of the excitatory amino acid L-glutamate but decreases extracellular levels of L-glutamine (R. E. Haskew-Layton et al., PLoS ONE, 3: e3543). The release of glutamate was linked to activation of volume-regulated anion channels, whereas mechanism(s) responsible for alterations in extracellular glutamine remained unclear. When mannitol was added to the hypo-osmotic medium to reverse reductions in osmolarity, changes in microdialysate levels of glutamine were prevented, indicating an involvement of cellular swelling. As the main source of brain glutamine is astrocytic synthesis and export, we explored the impact of hypo-osmotic medium on glutamine synthesis and transport in rat primary astrocyte cultures. In astrocytes, a 40% reduction in medium osmolarity moderately stimulated the release of L-[(3) H]glutamine by ∼twofold and produced no changes in L-[(3) H]glutamine uptake. In comparison, hypo-osmotic medium stimulated the release of glutamate (traced with D-[(3) H]aspartate) by more than 20-fold. In whole-cell enzymatic assays, we discovered that hypo-osmotic medium caused a 20% inhibition of astrocytic conversion of L-[(3) H]glutamate into L-[(3) H]glutamine by glutamine synthetase. Using an HPLC assay, we further found a 35% reduction in intracellular levels of endogenous glutamine. Overall, our findings suggest that cellular swelling (i) inhibits astrocytic glutamine synthetase activity, and (ii) reduces substrate availability for this enzyme because of the activation of volume-regulated anion channels. These combined effects likely lead to reductions in astrocytic glutamine export in vivo and may partially explain occurrence of hyperexcitability and seizures in human hyponatremia.
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Affiliation(s)
- María C Hyzinski-García
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, New York, USA
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25
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Inyushin M, Kucheryavykh LY, Kucheryavykh YV, Nichols CG, Buono RJ, Ferraro TN, Skatchkov SN, Eaton MJ. Potassium channel activity and glutamate uptake are impaired in astrocytes of seizure-susceptible DBA/2 mice. Epilepsia 2010; 51:1707-13. [PMID: 20831751 DOI: 10.1111/j.1528-1167.2010.02592.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
PURPOSE KCNJ10 encodes subunits of inward rectifying potassium (Kir) channel Kir4.1 found predominantly in glial cells within the brain. Genetic inactivation of these channels in glia impairs extracellular K(+) and glutamate clearance and produces a seizure phenotype. In both mice and humans, polymorphisms and mutations in the KCNJ10 gene have been associated with seizure susceptibility. The purpose of the present study was to determine whether there are differences in Kir channel activity and potassium- and glutamate-buffering capabilities between astrocytes from seizure resistant C57BL/6 (B6) and seizure susceptible DBA/2 (D2) mice that are consistent with an altered K(+) channel activity as a result of genetic polymorphism of KCNJ10. METHODS Using cultured astrocytes and hippocampal brain slices together with whole-cell patch-clamp, we determined the electrophysiologic properties, particularly K(+) conductances, of B6 and D2 mouse astrocytes. Using a colorimetric assay, we determined glutamate clearance capacity by B6 and D2 astrocytes. RESULTS Barium-sensitive Kir currents elicited from B6 astrocytes are substantially larger than those elicited from D2 astrocytes. In addition, potassium and glutamate buffering by D2 cortical astrocytes is impaired, relative to buffering by B6 astrocytes. DISCUSSION In summary, the activity of Kir4.1 channels differs between seizure-susceptible D2 and seizure-resistant B6 mice. Reduced activity of Kir4.1 channels in astrocytes of D2 mice is associated with deficits in potassium and glutamate buffering. These deficits may, in part, explain the relatively low seizure threshold of D2 mice.
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Affiliation(s)
- Mikhail Inyushin
- Department of Physiology, Universidad Central del Caribe, School of Medicine, Bayamón, Puerto Rico 00960-6032, USA
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Brain volume regulation: osmolytes and aquaporin perspectives. Neuroscience 2010; 168:871-84. [DOI: 10.1016/j.neuroscience.2009.11.074] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Revised: 11/13/2009] [Accepted: 11/25/2009] [Indexed: 02/08/2023]
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Hayakawa K, Nakano T, Irie K, Higuchi S, Fujioka M, Orito K, Iwasaki K, Jin G, Lo EH, Mishima K, Fujiwara M. Inhibition of reactive astrocytes with fluorocitrate retards neurovascular remodeling and recovery after focal cerebral ischemia in mice. J Cereb Blood Flow Metab 2010; 30:871-82. [PMID: 19997116 PMCID: PMC2949171 DOI: 10.1038/jcbfm.2009.257] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Glial scarring is traditionally thought to be detrimental after stroke. But emerging studies now suggest that reactive astrocytes may also contribute to neurovascular remodeling. Here, we assessed the effects and mechanisms of metabolic inhibition of reactive astrocytes in a mouse model of stroke recovery. Five days after stroke onset, astrocytes were metabolically inhibited with fluorocitrate (FC, 1 nmol). Markers of reactive astrocytes (glial fibrillary acidic protein (GFAP), HMGB1), markers of neurovascular remodeling (CD31, synaptophysin, PSD95), and behavioral outcomes (neuroscore, rotarod latency) were quantified from 1 to 14 days. As expected, focal cerebral ischemia induced significant neurological deficits in mice. But over the course of 14 days after stroke onset, a steady improvement in neuroscore and rotarod latencies were observed as the mice spontaneously recovered. Reactive astrocytes coexpressing GFAP and HMGB1 increased in peri-infarct cortex from 1 to 14 days after cerebral ischemia in parallel with an increase in the neurovascular remodeling markers CD31, synaptophysin, and PSD95. Compared with stroke-only controls, FC-treated mice demonstrated a significant decrease in HMGB1-positive reactive astrocytes and neurovascular remodeling, as well as a corresponding worsening of behavioral recovery. Our results suggest that reactive astrocytes in peri-infarct cortex may promote neurovascular remodeling, and these glial responses may aid functional recovery after stroke.
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Toward rational design of electrical stimulation strategies for epilepsy control. Epilepsy Behav 2010; 17:6-22. [PMID: 19926525 PMCID: PMC2818293 DOI: 10.1016/j.yebeh.2009.10.017] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2009] [Accepted: 10/12/2009] [Indexed: 11/21/2022]
Abstract
Electrical stimulation is emerging as a viable alternative for patients with epilepsy whose seizures are not alleviated by drugs or surgery. Its attractions are temporal and spatial specificity of action, flexibility of waveform parameters and timing, and the perception that its effects are reversible unlike resective surgery. However, despite significant advances in our understanding of mechanisms of neural electrical stimulation, clinical electrotherapy for seizures relies heavily on empirical tuning of parameters and protocols. We highlight concurrent treatment goals with potentially conflicting design constraints that must be resolved when formulating rational strategies for epilepsy electrotherapy, namely, seizure reduction versus cognitive impairment, stimulation efficacy versus tissue safety, and mechanistic insight versus clinical pragmatism. First, treatment markers, objectives, and metrics relevant to electrical stimulation for epilepsy are discussed from a clinical perspective. Then the experimental perspective is presented, with the biophysical mechanisms and modalities of open-loop electrical stimulation, and the potential benefits of closed-loop control for epilepsy.
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Schachter SC, Guttag J, Schiff SJ, Schomer DL. Advances in the application of technology to epilepsy: the CIMIT/NIO Epilepsy Innovation Summit. Epilepsy Behav 2009; 16:3-46. [PMID: 19780225 PMCID: PMC8118381 DOI: 10.1016/j.yebeh.2009.06.028] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In 2008, a group of clinicians, scientists, engineers, and industry representatives met to discuss advances in the application of engineering technologies to the diagnosis and treatment of patients with epilepsy. The presentations also provided a guide for further technological development, specifically in the evaluation of patients for epilepsy surgery, seizure onset detection and seizure prediction, intracranial treatment systems, and extracranial treatment systems. This article summarizes the discussions and demonstrates that cross-disciplinary interactions can catalyze collaborations between physicians and engineers to address and solve many of the pressing unmet needs in epilepsy.
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Affiliation(s)
- Steven C Schachter
- Center for Integration of Medicine and Innovative Technology, Boston, MA, USA.
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