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Naylor DE. In the fast lane: Receptor trafficking during status epilepticus. Epilepsia Open 2023; 8 Suppl 1:S35-S65. [PMID: 36861477 PMCID: PMC10173858 DOI: 10.1002/epi4.12718] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Accepted: 02/23/2023] [Indexed: 03/03/2023] Open
Abstract
Status epilepticus (SE) remains a significant cause of morbidity and mortality and often is refractory to standard first-line treatments. A rapid loss of synaptic inhibition and development of pharmacoresistance to benzodiazepines (BZDs) occurs early during SE, while NMDA and AMPA receptor antagonists remain effective treatments after BZDs have failed. Multimodal and subunit-selective receptor trafficking within minutes to an hour of SE involves GABA-A, NMDA, and AMPA receptors and contributes to shifts in the number and subunit composition of surface receptors with differential impacts on the physiology, pharmacology, and strength of GABAergic and glutamatergic currents at synaptic and extrasynaptic sites. During the first hour of SE, synaptic GABA-A receptors containing γ2 subunits move to the cell interior while extrasynaptic GABA-A receptors with δ subunits are preserved. Conversely, NMDA receptors containing N2B subunits are increased at synaptic and extrasynaptic sites, and homomeric GluA1 ("GluA2-lacking") calcium permeant AMPA receptor surface expression also is increased. Molecular mechanisms, largely driven by NMDA receptor or calcium permeant AMPA receptor activation early during circuit hyperactivity, regulate subunit-specific interactions with proteins involved with synaptic scaffolding, adaptin-AP2/clathrin-dependent endocytosis, endoplasmic reticulum (ER) retention, and endosomal recycling. Reviewed here is how SE-induced shifts in receptor subunit composition and surface representation increase the excitatory to inhibitory imbalance that sustains seizures and fuels excitotoxicity contributing to chronic sequela such as "spontaneous recurrent seizures" (SRS). A role for early multimodal therapy is suggested both for treatment of SE and for prevention of long-term comorbidities.
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Affiliation(s)
- David E Naylor
- VA Greater Los Angeles Healthcare System, Department of Neurology, David Geffen School of Medicine at UCLA, and The Lundquist Institute at Harbor-UCLA Medical Center, Los Angeles, California, USA
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2
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Volpe JJ. Commentary - Early discontinuation of antiseizure medication in neonatal seizures - Proceed with caution. J Neonatal Perinatal Med 2021; 15:203-207. [PMID: 34459421 PMCID: PMC9108580 DOI: 10.3233/npm-210849] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- J J Volpe
- Department of Neurology, Harvard Medical School, Boston, MA, USA.,Department of Pediatric Newborn Medicine, Harvard Medical School, Boston, MA, USA
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3
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Zhang M, Cui Y, Zhu W, Yu J, Cheng Y, Wu X, Zhang J, Xin W, Yu Y, Sun H. Attenuation of the mutual elevation of iron accumulation and oxidative stress may contribute to the neuroprotective and anti-seizure effects of xenon in neonatal hypoxia-induced seizures. Free Radic Biol Med 2020; 161:212-223. [PMID: 33075502 DOI: 10.1016/j.freeradbiomed.2020.09.030] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Revised: 09/20/2020] [Accepted: 09/21/2020] [Indexed: 12/21/2022]
Abstract
Previous studies have suggested that xenon inhalation has neuroprotective and antiepileptic effects; however, the underlying mechanisms involved remain unclear. This study aimed to investigate the possible xenon inhalation mechanisms involved in the neuroprotection and antiepileptic effects. A neonatal hypoxic C57BL/6J mouse model was used for the experiments. Immediately after hypoxia treatment, the treatment group inhaled a xenon mixture (70% xenon/21% oxygen/9% nitrogen) for 60 min, while the hypoxia group inhaled a non-xenon mixture (21% oxygen/79% nitrogen) for 60 min. Seizure activity was recorded at designated time points using electroencephalography. Oxidative stress levels, iron levels, neuronal injury, and learning and memory functions were also studied. The results showed that hypoxia increased the levels of iron, oxidative stress, mitophagy, and neurodegeneration, which were accompanied by seizures and learning and memory disorders. In addition, our results confirmed that xenon treatment significantly attenuated the hypoxia-induced seizures and cognitive defects in neonatal C57 mice. Moreover, the increased levels of iron, oxidative stress, mitophagy, and neuronal injury were reduced in xenon-treated mice. This study confirms the significant protective effects of a xenon mixture on hypoxia-induced damage in neonatal mice. Furthermore, our results suggest that reducing oxidative stress levels and iron accumulation may be the underlying mechanisms of xenon activity. Studying the protective mechanisms of xenon will advance its applications in potential therapeutic strategies.
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Affiliation(s)
- Mengdi Zhang
- School of Pharmaceutical Sciences, Binzhou Medical University, Yantai, 264003, China
| | - Yaru Cui
- School of Pharmaceutical Sciences, Binzhou Medical University, Yantai, 264003, China
| | - Wei Zhu
- Institute of Radiation Medicine, Shandong Academy of Medical Sciences, Shandong First Medical University, Jinan, 250062, China
| | - Jie Yu
- School of Pharmaceutical Sciences, Binzhou Medical University, Yantai, 264003, China
| | - Yao Cheng
- School of Pharmaceutical Sciences, Binzhou Medical University, Yantai, 264003, China
| | - Xiangdong Wu
- School of Pharmaceutical Sciences, Binzhou Medical University, Yantai, 264003, China
| | - Jinjin Zhang
- School of Pharmaceutical Sciences, Binzhou Medical University, Yantai, 264003, China
| | - Wenyu Xin
- School of Pharmaceutical Sciences, Binzhou Medical University, Yantai, 264003, China
| | - Yan Yu
- School of Pharmaceutical Sciences, Binzhou Medical University, Yantai, 264003, China
| | - Hongliu Sun
- School of Pharmaceutical Sciences, Binzhou Medical University, Yantai, 264003, China.
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Jung S, Ballheimer YE, Brackmann F, Zoglauer D, Geppert CI, Hartmann A, Trollmann R. Seizure-induced neuronal apoptosis is related to dysregulation of the RNA-edited GluR2 subunit in the developing mouse brain. Brain Res 2020; 1735:146760. [PMID: 32142720 DOI: 10.1016/j.brainres.2020.146760] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2019] [Revised: 02/27/2020] [Accepted: 03/02/2020] [Indexed: 12/28/2022]
Abstract
Ca2+-permeable AMPA receptors (AMPAR) which crucially modify maturational programs of the developing brain are involved in seizure-induced glutamate excitotoxicity and apoptosis. Regulatory effects on AMPAR subunit composition and RNA-editing in the developing brain and their significance as therapeutic targets are not well understood. Here, we analyzed acute effects of recurrent pilocarpine-induced neonatal seizures on age- and region-specific expression of AMPAR subunits and adenosine deaminases (ADAR) in the developing mouse brain (P10). After recurrent seizure activity and regeneration periods of 6-72 h cerebral mRNA levels of GluR (glutamate receptor subunit) 1, GluR2, GluR3, and GluR4 were unaffected compared to controls. However, ratio of GluR2 and GluR4 to pooled GluR1-4 mRNA concentration significantly decreased in seizure-exposed brains in comparison to controls. After a regeneration period of 24-72 h ADAR1 and ADAR2 mRNA expression was significantly lower in seizure-exposed brains than in those of controls. This was confirmed at the protein level in the hippocampal CA3 region. We observed a regionally increased apoptosis (TUNEL+ and CC3+ cells) in the hippocampus, parietal cortex and subventricular zone of seizure-exposed brains in comparison to controls. Together, present in vivo data demonstrate the maturational age-specific, functional role of RNA-edited GluR2 in seizure-induced excitotoxicity in the developing mouse brain. In response to recurrent seizure activity, we observed reduced expression of GluR2 and the GluR2 mRNA-editing enzymes ADAR1 and ADAR2 accompanied by increased apoptosis in a region-specific manner. Thus, AMPA receptor subtype-specific mRNA editing is assessed as a promising target of novel neuroprotective treatment strategies in consideration of age-related developmental mechanisms.
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Affiliation(s)
- Susan Jung
- Department of Pediatrics, Division of Neuropediatrics, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Yili E Ballheimer
- Department of Pediatrics, Division of Neuropediatrics, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Florian Brackmann
- Department of Pediatrics, Division of Neuropediatrics, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Daniel Zoglauer
- Department of Pediatrics, Division of Neuropediatrics, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Carol-Immanuel Geppert
- Institute of Pathology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Arndt Hartmann
- Institute of Pathology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Regina Trollmann
- Department of Pediatrics, Division of Neuropediatrics, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany.
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Xenon exerts anti-seizure and neuroprotective effects in kainic acid-induced status epilepticus and neonatal hypoxia-induced seizure. Exp Neurol 2019; 322:113054. [DOI: 10.1016/j.expneurol.2019.113054] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 07/27/2019] [Accepted: 09/01/2019] [Indexed: 12/16/2022]
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Sodium Valproate Ameliorates Neuronal Apoptosis in a Kainic Acid Model of Epilepsy via Enhancing PKC-Dependent GABA AR γ2 Serine 327 Phosphorylation. Neurochem Res 2018; 43:2343-2352. [PMID: 30311181 DOI: 10.1007/s11064-018-2659-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 09/19/2018] [Accepted: 10/09/2018] [Indexed: 02/06/2023]
Abstract
GABA is a dominant inhibitory neurotransmitter in the brain and A type GABA receptor (GABAAR) phosphorylation is critical for GABA-mediated inhibitory effect. However, its role in the neuroprotective effect of sodium valproate (VPA), a prevalent drug for treating patients with epilepsy, remains elusive. The present study was conducted to explore the role of GABAAR phosphorylation in the neuroprotection of VPA against a kainic acid-induced epileptic rat model and the potential molecular mechanisms. Neuronal apoptosis was evaluated by TUNEL assay, PI/Annexin V double staining, caspase-3 activity detection and Bax and Bcl-2 proteins expression via Western blot analysis. The primary rat hippocampal neurons were cultivated and cell viability was measured by CCK8 detection following KA- or free Mg2+-induced neuronal impairment. Our results found that VPA treatment significantly reduced neuronal apoptosis in the KA-induced rat model (including reductions of TUNEL-positive cells, caspase-3 activity and Bax protein expression, and increase of Bcl-2 protein level). In the in vitro experiments, VPA at the concentration of 1 mM for 24 h also increased cell survival and suppressed cell apoptosis in KA- or no Mg2+-induced models via CCK8 assay and PI/Annexin V double staining, respectively. What is more important, the phosphorylation of γ2 subunit at serine 327 residue for GABAAR was found to be robustly enhanced both in the KA-induced epileptic rat model and neuronal cultures following KA exposure after VPA treatment, while no evident alteration was found in terms of GABAAR β3 phosphorylation (408 or 409 serine residue). Additionally, pharmacological inhibition of protein kinase C (PKC) clearly abrogated the neuroprotective potential of VPA against KA- or free Mg2+-associated neuronal injury, indicating a critical role of PKC in the effect of GABAAR γ2 serine 327 phosphorylation in VPA's protection. In summary, our work reveals that VPA mitigates neuronal apoptosis in KA-triggered epileptic seizures, at least, via augmenting PKC-dependent GABAAR γ2 phosphorylation at serine 327 residue.
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Xiong TQ, Chen LM, Tan BH, Guo CY, Li YN, Zhang YF, Li SL, Zhao H, Li YC. The effects of calcineurin inhibitor FK506 on actin cytoskeleton, neuronal survival and glial reactions after pilocarpine-induced status epilepticus in mice. Epilepsy Res 2018; 140:138-147. [PMID: 29358156 DOI: 10.1016/j.eplepsyres.2018.01.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Revised: 12/05/2017] [Accepted: 01/03/2018] [Indexed: 01/03/2023]
Abstract
After status epilepticus (SE), actin cytoskeleton (F-actin) becomes progressively deconstructed in the hippocampus, which is consistent with the delayed pyramidal cell death in both time course and spatial distribution. A variety of experiments show that calcineurin inhibitors such as FK506 are able to inhibit the SE-induced actin depolymerization. However, it is still unclear what changes happen to the F-actin in the epileptic brain after FK506 treatment. A pilocarpine model of SE in mice was used to examine the effects of FK506 on the F-actin in the hippocampal neurons. The post SE (PSE) mice with or without FK506 treatment were monitored consecutively for 14 days to examine the frequency and duration of spontaneous seizures. The effects of FK506 on the activity of cofilin and actin dynamics were assessed at 7 and 14 d PSE by western blots. The organization of F-actin, neuronal cell death, and glial reactions were investigated by phalloidin staining, histological and immunocytochemical staining, respectively. As compared to the PSE + vehicle mice, FK506 treatment significantly decreased the frequency and duration of spontaneous seizures. Relative to the PSE + vehicle mice, western blots detected a partial restoration of phosphorylated cofilin and a significant increase of F/G ratio in the hippocampus after FK506 treatment. In the PSE + vehicle mice, almost no F-actin puncta were left in the CA1 and CA3 subfields at 7 and 14 d PSE. FK506-treated PSE mice showed a similar decrease of F-actin, but the extent of damage was significantly ameliorated. Consistently, the surviving neurons became significantly increased in number after FK506 treatment, relative to the PSE + vehicle groups. After FK506 treatment, microglial reaction was partially inhibited, but the expression of GFAP was not significantly changed, compared to the PSE + vehicle mice. The results suggest that post-epileptic treatment with FK506 ameliorated, but could not stop the deconstruction of F-actin or the delayed neuronal loss in the PSE mice.
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Affiliation(s)
- Tian-Qing Xiong
- Department of Histology and Embryology, College of Basic Medical Sciences, Norman Bethune Health Science Center of Jilin University, Jilin Province, 130021, PR China
| | - Ling-Meng Chen
- Department of Histology and Embryology, College of Basic Medical Sciences, Norman Bethune Health Science Center of Jilin University, Jilin Province, 130021, PR China
| | - Bai-Hong Tan
- Laboratory Teaching Center of Basic Medicine, Norman Bethune Health Science Center of Jilin University, Jilin Province, 130021, PR China
| | - Chun-Yan Guo
- Department of Histology and Embryology, College of Basic Medical Sciences, Norman Bethune Health Science Center of Jilin University, Jilin Province, 130021, PR China
| | - Yong-Nan Li
- Department of Neurology, Fourth Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang Province 150001, PR China
| | - Yan-Feng Zhang
- Department of Neurology, First Affiliated Hospital of Jilin University, Changchun, Jilin Province 130021, PR China
| | - Shu-Lei Li
- Department of Histology and Embryology, College of Basic Medical Sciences, Norman Bethune Health Science Center of Jilin University, Jilin Province, 130021, PR China
| | - Hui Zhao
- Department of Histology and Embryology, College of Basic Medical Sciences, Norman Bethune Health Science Center of Jilin University, Jilin Province, 130021, PR China
| | - Yan-Chao Li
- Department of Histology and Embryology, College of Basic Medical Sciences, Norman Bethune Health Science Center of Jilin University, Jilin Province, 130021, PR China.
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Lippman-Bell JJ, Zhou C, Sun H, Feske JS, Jensen FE. Early-life seizures alter synaptic calcium-permeable AMPA receptor function and plasticity. Mol Cell Neurosci 2016; 76:11-20. [PMID: 27521497 DOI: 10.1016/j.mcn.2016.08.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Revised: 07/15/2016] [Accepted: 08/09/2016] [Indexed: 12/31/2022] Open
Abstract
Calcium (Ca2+)-mediated4 signaling pathways are critical to synaptic plasticity. In adults, the NMDA glutamate receptor (NMDAR) represents a major route for activity-dependent synaptic Ca2+ entry. However, during neonatal development, when synaptic plasticity is particularly high, many AMPA glutamate receptors (AMPARs) are also permeable to Ca2+ (CP-AMPAR) due to low GluA2 subunit expression, providing an additional route for activity- and glutamate-dependent Ca2+ influx and subsequent signaling. Therefore, altered hippocampal Ca2+ signaling may represent an age-specific pathogenic mechanism. We thus aimed to assess Ca2+ responses 48h after hypoxia-induced neonatal seizures (HS) in postnatal day (P)10 rats, a post-seizure time point at which we previously reported LTP attenuation. We found that Ca2+ responses were higher in brain slices from post-HS rats than in controls and that this increase was CP-AMPAR-dependent. To determine whether synaptic CP-AMPAR expression was also altered post-HS, we assessed the expression of GluA2 at hippocampal synapses and the expression of long-term depression (LTD), which has been linked to the presence of synaptic GluA2. Here we report a decrease 48h after HS in synaptic GluA2 expression at synapses and LTD in hippocampal CA1. Given the potentially critical role of AMPAR trafficking in disease progression, we aimed to establish whether post-seizure in vivo AMPAR antagonist treatment prevented the enhanced Ca2+ responses, changes in GluA2 synaptic expression, and diminished LTD. We found that NBQX treatment prevents all three of these post-seizure consequences, further supporting a critical role for AMPARs as an age-specific therapeutic target.
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Affiliation(s)
- Jocelyn J Lippman-Bell
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States; Boston Children's Hospital, Boston, MA 02114, United States; Philadelphia College of Osteopathic Medicine, Philadelphia, PA 19131, United States
| | - Chengwen Zhou
- Boston Children's Hospital, Boston, MA 02114, United States
| | - Hongyu Sun
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States; Boston Children's Hospital, Boston, MA 02114, United States
| | - Joel S Feske
- Boston Children's Hospital, Boston, MA 02114, United States
| | - Frances E Jensen
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States; Boston Children's Hospital, Boston, MA 02114, United States.
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Sun H, Juul HM, Jensen FE. Models of hypoxia and ischemia-induced seizures. J Neurosci Methods 2015; 260:252-60. [PMID: 26434705 DOI: 10.1016/j.jneumeth.2015.09.023] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 09/22/2015] [Indexed: 01/19/2023]
Abstract
Despite greater understanding and improved management, seizures continue to be a major problem in childhood. Neonatal seizures are often refractory to conventional antiepileptic drugs, and can result in later life epilepsy and cognitive deficits, conditions for which there are no specific treatments. Hypoxic and/or ischemic encephalopathy (HIE) is the most common cause for neonatal seizures, and accounts for more than two-thirds of neonatal seizure cases. A better understanding of the cellular and molecular mechanisms is essential for identifying new therapeutic strategies that control the neonatal seizures and its cognitive consequences. This heavily relies on animal models that play a critical role in discovering novel mechanisms underlying both epileptogenesis and associated cognitive impairments. To date, a number of animal models have provided a tremendous amount of information regarding the pathophysiology of HIE-induced neonatal seizures. This review provides an overview on the most important features of the main animal models of HIE-induced seizures. In particular, we focus on the methodology of seizure induction and the characterizations of post-HIE injury consequences. These aspects of HIE-induced seizure models are discussed in the light of the suitability of these models in studying human HIE-induced seizures.
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Affiliation(s)
- Hongyu Sun
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Halvor M Juul
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Frances E Jensen
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States.
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Suchomelova L, Lopez-Meraz ML, Niquet J, Kubova H, Wasterlain CG. Hyperthermia aggravates status epilepticus-induced epileptogenesis and neuronal loss in immature rats. Neuroscience 2015; 305:209-24. [PMID: 26259902 DOI: 10.1016/j.neuroscience.2015.08.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 07/20/2015] [Accepted: 08/03/2015] [Indexed: 01/16/2023]
Abstract
This study tightly controlled seizure duration and severity during status epilepticus (SE) in postnatal day 10 (P10) rats, in order to isolate hyperthermia as the main variable and to study its consequences. Body temperature was maintained at 39 ± 1 °C in hyperthermic SE rats (HT+SE) or at 35 ± 1 °C in normothermic SE animals (NT+SE) during 30 min of SE, which was induced by lithium-pilocarpine (3 mEq/kg, 60 mg/kg) and terminated by diazepam and cooling to NT. All video/EEG measures of SE severity were similar between HT+SE and NT+SE pups. At 24h, neuronal injury was present in the amygdala in the HT+SE group only, and was far more severe in the hippocampus in HT+SE than NT+SE pups. Separate groups of animals were monitored four months later for spontaneous recurrent seizures (SRS). Only HT+SE animals developed convulsive SRS. Both HT+SE and NT+SE animals developed electrographic SRS (83% vs. 55%), but SRS frequency and severity were higher in hyperthermic animals (12.5 ± 3.5 vs. 4.2 ± 2.0 SRS/day). The density of hilar neurons was lower, thickness of the amygdala and perirhinal cortex was reduced, and lateral ventricles were enlarged in HT+SE over NT+SE littermates and HT/NT controls. In this model, hyperthermia greatly increased the epileptogenicity of SE and its neuropathological sequelae.
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Affiliation(s)
- L Suchomelova
- Veterans Administration Greater Los Angeles Healthcare System, Epilepsy Research (151), 11 301 Wilshire Boulevard, Building 114, Room 139, Los Angeles, CA 90073, USA.
| | - M L Lopez-Meraz
- Centro de Investigaciones Cerebrales, Universidad Veracruzana, Veracruz 91190, Mexico
| | - J Niquet
- Veterans Administration Greater Los Angeles Healthcare System, Epilepsy Research (151), 11 301 Wilshire Boulevard, Building 114, Room 139, Los Angeles, CA 90073, USA
| | - H Kubova
- Department of Developmental Epileptology, Institute of Physiology, Academy of Sciences of the Czech Republic, Videnska 1083, Prague 14220, Czech Republic
| | - C G Wasterlain
- Department of Neurology, David Geffen School of Medicine at UCLA, VA Medical Center (127), 11 301 Wilshire Boulevard, Los Angeles, CA 90073, USA
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Joshi S, Rajasekaran K, Hawk KM, Brar J, Ross BM, Tran CA, Chester SJ, Goodkin HP. Phosphatase inhibition prevents the activity-dependent trafficking of GABAA receptors during status epilepticus in the young animal. Epilepsia 2015; 56:1355-65. [PMID: 26248944 DOI: 10.1111/epi.13098] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/01/2015] [Indexed: 01/12/2023]
Abstract
OBJECTIVES To determine if the activity-dependent trafficking of γ2 subunit-containing γ-aminobutyric acid type A receptors (GABAA Rs) that has been observed in older animals and posited to contribute to benzodiazepine pharmacoresistance during status epilepticus (SE) is age-dependent, and to evaluate whether blockade of protein phosphatases can inhibit or reverse the activity-dependent plasticity of these receptors. METHODS The efficacy and potency of diazepam 0.2-10 mg/kg administered 3 or 60 min after the onset of a lithium/pilocarpine-induced seizure in postnatal day 15-16 rats was evaluated using video-electroencephalography (EEG) recordings. The surface expression of γ2 subunit-containing GABAA Rs was assessed using a biotinylation assay, and GABAA R-mediated miniature inhibitory postsynaptic currents (mIPSCs) were recorded using whole-cell patch-clamp recording techniques from dentate granule cells in hippocampal slices acutely obtained 60 min after seizure onset (SE-treated). The effect of the protein phosphatase inhibitors FK506 and okadaic acid (OA) on the surface expression of these receptors was determined in organotypic slice cultures exposed to high potassium and N-methyl-d-aspartate (NMDA) or in SE-treated slices. RESULTS Diazepam terminated seizures of 3 min but not 60 min duration, even at the highest dose. In the SE-treated slices, the surface expression of γ2 subunit-containing GABAA Rs was reduced and the amplitude of the mIPSCs was diminished. Inhibition of protein phosphatases prevented the activity-induced reduction of the γ2 subunit-containing GABAA Rs in organotypic slice cultures. Furthermore, treatment of SE-treated slices with FK506 or OA restored the surface expression of the γ2 subunit-containing GABAA Rs and the mIPSC amplitude. SIGNIFICANCE This study demonstrates that the plasticity of γ2 subunit-containing GABAA Rs associated with the development of benzodiazepine resistance in young and adult animals is similar. The findings of this study suggest that the mechanisms regulating the activity-dependent trafficking of GABAA Rs during SE can be targeted to develop novel adjunctive therapy for the treatment of benzodiazepine-refractory SE.
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Affiliation(s)
- Suchitra Joshi
- Department of Neurology, University of Virginia Health System, Charlottesville, Virginia, U.S.A
| | - Karthik Rajasekaran
- Department of Neurology, University of Virginia Health System, Charlottesville, Virginia, U.S.A
| | - Kyle M Hawk
- Department of Neurology, University of Virginia Health System, Charlottesville, Virginia, U.S.A
| | - Jasmit Brar
- Department of Neurology, University of Virginia Health System, Charlottesville, Virginia, U.S.A
| | - Brittany M Ross
- Department of Pediatrics, University of Virginia Health System, Charlottesville, Virginia, U.S.A
| | - Christine A Tran
- Department of Neurology, University of Virginia Health System, Charlottesville, Virginia, U.S.A
| | - Stephen J Chester
- Department of Neurology, University of Virginia Health System, Charlottesville, Virginia, U.S.A
| | - Howard P Goodkin
- Department of Neurology, University of Virginia Health System, Charlottesville, Virginia, U.S.A.,Department of Pediatrics, University of Virginia Health System, Charlottesville, Virginia, U.S.A
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Jensen FE. Developmental factors in the pathogenesis of neonatal seizures. JOURNAL OF PEDIATRIC NEUROLOGY 2015; 7:5-12. [PMID: 20191097 DOI: 10.3233/jpn-2009-0270] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Neonatal seizures are inherently different from seizures in the child and the adult. The phenotype, often exhibiting electroclinical dissociation, is unique: neonatal seizures can be refractory to antiepileptic drugs otherwise effect for older patients. Recent experimental and human-based research reveals that the mechanism of neonatal seizures, as well as their long-term sequelae on later brain development, appears to involve a large number of age-specific factors. These observations help explain the resistance of neonatal seizures to conventional therapy as well as identify potential areas of risk for later neurocognitive development. Emerging targets from this research may suggest new therapies for this unique population of patients.
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Affiliation(s)
- Frances E Jensen
- Department of Neurology, Children's Hospital, and Program in Neurobiology, Harvard Medical School, Boston, MA, USA
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13
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Liu J, Li X, Chen L, Xue P, Yang Q, Wang A. Increased calcineurin expression after pilocarpine-induced status epilepticus is associated with brain focal edema and astrogliosis. Int J Neurosci 2015; 126:560-567. [PMID: 26000933 DOI: 10.3109/00207454.2015.1045975] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Calcineurin plays an important role in the development of neuronal excitability, modulation of receptor's function and induction of apoptosis in neurons. It has been established in kindling models that status epilepticus induces brain focal edema and astrocyte activation. However, the role of calcineurin in brain focal edema and astrocyte activation in status epilepticus has not been fully understood. In this study, we employed a model of lithium-pilocarpine-induced status epilepticus and detected calcineurin expression in hippocampus by immunoblotting, brain focal edema by non-invasive magnetic resonance imaging (MRI-7T) and astrocyte expression by immunohistochemistry. We found that the brain focal edema was seen at 24 h after status epilepticus, and astrocyte expression was obviously seen at 7 d after status epilepticus. Meanwhile, calcineurin expression was seen at24 h and retained to 7 d after status epilepticus. A FK506, a calcineurin inhibitor, remarkably suppressed the status epilepticus-induced brain focal edema and astrocyte expression. Our data suggested that calcineurin overexpression plays a very important role in brain focal edema and astrocyte expression. Therefore, calcineurin may be a novel candidate for brain focal edema occurring and intracellular trigger of astrogliosis in status epilepticus.
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Affiliation(s)
- Jinzhi Liu
- a Department of Neurology, Shandong Provincial Qianfoshan Hospital , Shandong University , Jinan , P.R. China
| | - Xiaolin Li
- a Department of Neurology, Shandong Provincial Qianfoshan Hospital , Shandong University , Jinan , P.R. China
| | - Liguang Chen
- b Department of MRI Diagnosis , Shandong Medical Imaging Research Institute , Jinan , P.R. China
| | - Ping Xue
- a Department of Neurology, Shandong Provincial Qianfoshan Hospital , Shandong University , Jinan , P.R. China
| | - Qianqian Yang
- a Department of Neurology, Shandong Provincial Qianfoshan Hospital , Shandong University , Jinan , P.R. China
| | - Aihua Wang
- a Department of Neurology, Shandong Provincial Qianfoshan Hospital , Shandong University , Jinan , P.R. China
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Eghbalian F, Rasuli B, Monsef F. Frequency, Causes, and Findings of Brain CT Scans of Neonatal Seizure at Besat Hospital, Hamadan, Iran. IRANIAN JOURNAL OF CHILD NEUROLOGY 2015; 9:56-63. [PMID: 25767540 PMCID: PMC4322500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/25/2013] [Revised: 05/15/2014] [Accepted: 05/27/2014] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Neonatal seizures are the most common neurological symptoms and often signal an underlying serious neurologic condition. This study determines the frequency of neonatal seizure, predisposing factors, and brain computed tomography (CT) scan findings. MATERIALS & METHODS In a descriptive cross-sectional study, we evaluated all neonates with seizures who had been hospitalized in Besat hospital from 2007-2012. All data were gathered with questionnaires and used to compare with statistical tests by SPSS (ver 16). RESULTS 141 (4.08%) neonates (M:F; 1:2.2) were diagnosed with neonatal seizures. From the total number of 3,452 neonatal hospitalization, 78% of neonates with seizures were less than 10 days old and 60.3% of infants were born from natural vaginal delivery. As the most common cause, hypoxic-ischemic encephalopathy in this study was associated with 31.3% (n=44) of neonatal seizures and with the highest mortality rate (n=6). Among admitted neonates with seizures, the overall mortality rate was 12.8% (18 cases). A total of 33.3% of patients (47 cases) had abnormal CT scan reports and 24.8% (35 cases) of patients were not evaluated with a CT scan. Hypoxic-ischemic encephalopathy (47%) and local ischemic changes (25.5%) were the most common findings in the CT scans of neonates with seizures. CONCLUSION There was a significant correlation between neonatal seizures and delivery circumstances (p-value < 0.05). Therefore, with improvement of obstetric and delivery circumstances, early detection of predisposing factors and other rare conditions, and rapid effective treatment of these contributing factors, the rate of neonatal seizure in this period can be reduced.
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Affiliation(s)
- Fateme Eghbalian
- Pediatric Department, Hamadan University of Medical Sciences, Besat Hospital. Hamadan, Iran
| | - Bahman Rasuli
- Hamadan University of Medical Sciences, Besat Hospital. Hamadan, Iran
| | - Farnaz Monsef
- Hamadan University of Medical Sciences, Besat Hospital. Hamadan, Iran
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In vivo effects of bumetanide at brain concentrations incompatible with NKCC1 inhibition on newborn DGC structure and spontaneous EEG seizures following hypoxia-induced neonatal seizures. Neuroscience 2014; 286:203-15. [PMID: 25463517 DOI: 10.1016/j.neuroscience.2014.11.031] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 11/17/2014] [Accepted: 11/18/2014] [Indexed: 12/21/2022]
Abstract
Neonatal seizures caused by perinatal asphyxia and hypoxic-ischemic encephalopathy can be refractory to conventional anticonvulsants. This may be due to the depolarizing effects of gamma-aminobutyric acid (GABA) achieved by the activity of the Na(+)-K(+)-2Cl(-) cotransporter (NKCC1). The aim of this study is to evaluate the long-term effects of bumetanide, a NKCC1 inhibitor, on hippocampal neurogenesis and seizure susceptibility in hypoxia-induced neonatal seizure model. Wistar rats were subjected to hypoxia-induced neonatal seizures at postnatal day 10 (P10). Following acute seizures, the rats were treated with intraperitoneal injection (i.p.) of bumetanide at a dose of 0.5mg/kg for 3 weeks. In later adulthood, hypoxia-induced seizures increased the number of newborn dentate gyrus cells (DGCs), promoted mossy fiber sprouting (MFS) and reduced the apical dendritic complexity of newborn DGCs 1 month after the insults. In addition, these seizures resulted in long-lasting consequences, such as spontaneous electroencephalography (EEG) seizures, though spatial learning impairments were not seen. Bumetanide treatments significantly enhanced cell proliferation and dendritic development of newborn DGCs after neonatal seizures, accompanied by the decreased seizure activity. However, systemic administration of bumetanide resulted in much lower brain concentrations, and was incompatible with NKCC1 inhibition in blood-brain barrier (BBB)-protected brain tissue. Our results suggested that bumetanide might have long-term effects in suppressing seizure activity, and altering the neurogenesis after neonatal seizures. These effects of bumetanide may be mediated by the targets outside the BBB-protected central nerve system (CNS) or CNS-located target(s) other than NKCC1.
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The Calcineurin Inhibitor Ascomicin Interferes with the Early Stage of the Epileptogenic Process Induced by Latrunculin A Microperfusion in Rat Hippocampus. J Neuroimmune Pharmacol 2014; 9:654-67. [DOI: 10.1007/s11481-014-9558-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Accepted: 07/21/2014] [Indexed: 01/01/2023]
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Casanova JR, Nishimura M, Swann JW. The effects of early-life seizures on hippocampal dendrite development and later-life learning and memory. Brain Res Bull 2013; 103:39-48. [PMID: 24140049 DOI: 10.1016/j.brainresbull.2013.10.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 10/04/2013] [Accepted: 10/07/2013] [Indexed: 01/08/2023]
Abstract
Severe childhood epilepsy is commonly associated with intellectual developmental disabilities. The reasons for these cognitive deficits are likely multifactorial and will vary between epilepsy syndromes and even among children with the same syndrome. However, one factor these children have in common is the recurring seizures they experience - sometimes on a daily basis. Supporting the idea that the seizures themselves can contribute to intellectual disabilities are laboratory results demonstrating spatial learning and memory deficits in normal mice and rats that have experienced recurrent seizures in infancy. Studies reviewed here have shown that seizures in vivo and electrographic seizure activity in vitro both suppress the growth of hippocampal pyramidal cell dendrites. A simplification of dendritic arborization and a resulting decrease in the number and/or properties of the excitatory synapses on them could help explain the observed cognitive disabilities. There are a wide variety of candidate mechanisms that could be involved in seizure-induced growth suppression. The challenge is designing experiments that will help focus research on a limited number of potential molecular events. Thus far, results suggest that growth suppression is NMDA receptor-dependent and associated with a decrease in activation of the transcription factor CREB. The latter result is intriguing since CREB is known to play an important role in dendrite growth. Seizure-induced dendrite growth suppression may not occur as a single process in which pyramidal cells dendrites simply stop growing or grow slower compared to normal neurons. Instead, recent results suggest that after only a few hours of synchronized epileptiform activity in vitro dendrites appear to partially retract. This acute response is also NMDA receptor dependent and appears to be mediated by the Ca(+2)/calmodulin-dependent phosphatase, calcineurin. An understanding of the staging of seizure-induced growth suppression and the underlying molecular mechanisms will likely prove crucial for developing therapeutic strategies aimed at ameliorating the intellectual developmental disabilities associated with intractable childhood epilepsy.
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Affiliation(s)
- J R Casanova
- The Department of Neuroscience, Baylor College of Medicine, USA; The Cain Foundation Laboratories, The Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, USA
| | - Masataka Nishimura
- The Cain Foundation Laboratories, The Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, USA; Department of Pediatrics, Baylor College of Medicine, USA
| | - John W Swann
- The Department of Neuroscience, Baylor College of Medicine, USA; The Cain Foundation Laboratories, The Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, USA; Department of Pediatrics, Baylor College of Medicine, USA.
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Lippman-Bell JJ, Rakhade SN, Klein PM, Obeid M, Jackson MC, Joseph A, Jensen FE. AMPA receptor antagonist NBQX attenuates later-life epileptic seizures and autistic-like social deficits following neonatal seizures. Epilepsia 2013; 54:1922-32. [PMID: 24117347 DOI: 10.1111/epi.12378] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/15/2013] [Indexed: 12/12/2022]
Abstract
PURPOSE To determine whether AMPA receptor (AMPAR) antagonist NBQX can prevent early mammalian target of rapamycin (mTOR) pathway activation and long-term sequelae following neonatal seizures in rats, including later-life spontaneous recurrent seizures, CA3 mossy fiber sprouting, and autistic-like social deficits. METHODS Long-Evans rats experienced hypoxia-induced neonatal seizures (HS) at postnatal day (P)10. NBQX (20 mg/kg) was administered immediately following HS (every 12 h × 4 doses). Twelve hours post-HS, we assessed mTOR activation marker phosphorylated p70-S6 kinase (p-p70S6K) in hippocampus and cortex of vehicle (HS + V) or NBQX-treated post-HS rats (HS + N) versus littermate controls (C + V). Spontaneous seizure activity was compared between groups by epidural cortical electroencephalography (EEG) at P70-100. Aberrant mossy fiber sprouting was measured using Timm staining. Finally, we assessed behavior between P30 and P38. KEY FINDINGS Postseizure NBQX treatment significantly attenuated seizure-induced increases in p-p70S6K in the hippocampus (p < 0.01) and cortex (p < 0.001). Although spontaneous recurrent seizures increased in adulthood in HS + V rats compared to controls (3.22 ± 1 seizures/h; p = 0.03), NBQX significantly attenuated later-life seizures (0.14 ± 0.1 seizures/h; p = 0.046). HS + N rats showed less aberrant mossy fiber sprouting (115 ± 8.0%) than vehicle-treated post-HS rats (174 ± 10%, p = 0.004), compared to controls (normalized to 100%). Finally, NBQX treatment prevented alterations in later-life social behavior; post-HS rats showed significantly decreased preference for a novel over a familiar rat (71.0 ± 12 s) compared to controls (99.0 ± 15.6 s; p < 0.01), whereas HS + N rats showed social novelty preference similar to controls (114.3 ± 14.1 s). SIGNIFICANCE Brief NBQX administration during the 48 h postseizure in P10 Long-Evans rats suppresses transient mTOR pathway activation and attenuates spontaneous recurrent seizures, social preference deficits, and mossy fiber sprouting observed in vehicle-treated adult rats after early life seizures. These results suggest that acute AMPAR antagonist treatment during the latent period immediately following neonatal HS can modify seizure-induced activation of mTOR, reduce the frequency of later-life seizures, and protect against CA3 mossy fiber sprouting and autistic-like social deficits.
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Affiliation(s)
- Jocelyn J Lippman-Bell
- Department of Neurology, Children's Hospital Boston and Harvard Medical School, Boston, Massachusetts, U.S.A; Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, U.S.A
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Nakane S, Fujita K, Shibuta Y, Matsui N, Harada M, Urushihara R, Nishida Y, Izumi Y, Kaji R. Successful treatment of stiff person syndrome with sequential use of tacrolimus. J Neurol Neurosurg Psychiatry 2013; 84:1177-80. [PMID: 23715915 DOI: 10.1136/jnnp-2013-305425] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Casanova JR, Nishimura M, Le J, Lam TT, Swann JW. Rapid hippocampal network adaptation to recurring synchronous activity--a role for calcineurin. Eur J Neurosci 2013; 38:3115-27. [PMID: 23879713 DOI: 10.1111/ejn.12315] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Revised: 06/10/2013] [Accepted: 06/19/2013] [Indexed: 11/29/2022]
Abstract
Neuronal networks are thought to gradually adapt to altered neuronal activity over many hours and days. For instance, when activity is increased by suppressing synaptic inhibition, excitatory synaptic transmission is reduced. The underlying compensatory cellular and molecular mechanisms are thought to contribute in important ways to maintaining normal network operations. Seizures, due to their massive and highly synchronised discharging, probably challenge the adaptive properties of neurons, especially when seizures are frequent and intense - a condition common in early childhood. In the experiments reported here, we used rat and mice hippocampal slice cultures to explore the effects that recurring seizure-like activity has on the developing hippocampus. We found that developing networks adapted rapidly to recurring synchronised activity in that the duration of seizure-like events was reduced by 42% after 4 h of activity. At the same time, the frequency of spontaneous excitatory postsynaptic currents in pyramidal cells, the expression of biochemical biomarkers for glutamatergic synapses and the branching of pyramidal cell dendrites were all dramatically reduced. Experiments also showed that the reduction in N-methyl-D-aspartate receptor subunits and postsynaptic density protein 95 expression were N-methyl-D-aspartate receptor-dependent. To explore calcium signaling mechanisms in network adaptation, we tested inhibitors of calcineurin, a protein phosphatase known to play roles in synaptic plasticity and activity-dependent dendrite remodeling. We found that FK506 was able to prevent all of the electrophysiological, biochemical, and anatomical changes produced by synchronised network activity. Our results show that hippocampal pyramidal cells and their networks adapt rapidly to intense synchronised activity and that calcineurin play an important role in the underlying processes.
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Affiliation(s)
- J R Casanova
- The Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA; The Cain Foundation Laboratories, The Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, 1250 Moursund Street, Suite 1225, Houston, TX, 77030, USA
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Shih JJ, Tatum WO, Rudzinski LA. New drug classes for the treatment of partial onset epilepsy: focus on perampanel. Ther Clin Risk Manag 2013; 9:285-93. [PMID: 23874099 PMCID: PMC3711947 DOI: 10.2147/tcrm.s37317] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Perampanel (2-[2-oxo-1-phenyl-5-pyridin-2-yl-1,2-dihydropyridin-3-yl] benzonitrile hydrate) is the latest in the line of new antiepileptic drugs with a novel mechanism of action. Perampanel inhibits α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA)-induced increases in intracellular Ca2+ and selectively blocks AMPA receptor-mediated synaptic transmission, thus reducing neuronal excitation. Three Phase III multicenter, randomized, double-blind, placebo-controlled trials demonstrated the efficacy and good tolerability of perampanel as adjunctive treatment in patients with refractory partial-onset seizures. The drug is approved for use in the European Union and United States, with expected release onto the American market in June–September 2013, pending US Drug Enforcement Agency classification. The pharmacology of perampanel offers potential as more than just another new antiepileptic drug. This first-in-class drug will provide another option for practitioners of rational polytherapy. As an AMPA-receptor antagonist, perampanel may possess antiepileptogenic properties in addition to its demonstrated antiseizure properties.
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Affiliation(s)
- Jerry J Shih
- Department of Neurology, Mayo Clinic, Jacksonville, FL, USA
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Glutamate receptor 1 phosphorylation at serine 831 and 845 modulates seizure susceptibility and hippocampal hyperexcitability after early life seizures. J Neurosci 2013; 32:17800-12. [PMID: 23223299 DOI: 10.1523/jneurosci.6121-11.2012] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neonatal seizures can lead to later life epilepsy and neurobehavioral deficits, and there are no treatments to prevent these sequelae. We showed previously that hypoxia-induced seizures in a neonatal rat model induce rapid phosphorylation of serine-831 (S831) and Serine 845 (S845) sites of the AMPA receptor GluR1 subunit and later neuronal hyperexcitability and epilepsy, suggesting that seizure-induced posttranslational modifications may represent a novel therapeutic target. To unambiguously assess the contribution of these sites, we examined seizure susceptibility in wild-type mice versus transgenic knock-in mice with deficits in GluR1 S831 and S845 phosphorylation [GluR1 double-phosphomutant (GluR1 DPM) mice]. Phosphorylation of the GluR1 S831 and S845 sites was significantly increased in the hippocampus and cortex after a single episode of pentyleneterazol-induced seizures in postnatal day 7 (P7) wild-type mouse pups and that transgenic knock-in mice have a higher threshold and longer latencies to seizures. Like the rat, hypoxic seizures in P9 C57BL/6N wild-type mice resulted in transient increases in GluR1 S831 and GluR1 S845 phosphorylation in cortex and were associated with enhanced seizure susceptibility to later-life kainic-acid-induced seizures. In contrast, later-life seizure susceptibility after hypoxia-induced seizures was attenuated in GluR1 DPM mice, supporting a role for posttranslational modifications in seizure-induced network excitability. Finally, human hippocampal samples from neonatal seizure autopsy cases also showed an increase in GluR1 S831 and S845, supporting the validation of this potential therapeutic target in human tissue.
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Peng BW, Justice JA, He XH, Sanchez RM. Decreased A-currents in hippocampal dentate granule cells after seizure-inducing hypoxia in the immature rat. Epilepsia 2013; 54:1223-31. [PMID: 23815572 DOI: 10.1111/epi.12150] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/13/2013] [Indexed: 11/29/2022]
Abstract
PURPOSE Cerebral hypoxia is a major cause of neonatal seizures, and can lead to epilepsy. Pathologic anatomic and physiologic changes in the dentate gyrus have been associated with epileptogenesis in many experimental models, as this region is widely believed to gate the propagation of limbic seizures. However, the consequences of hypoxia-induced seizures for the immature dentate gyrus have not been extensively examined. METHODS Seizures were induced by global hypoxia (5-7% O2 for 15 min) in rat pups on postnatal day 10. Whole-cell voltage-clamp recordings were used to examine A-type potassium currents (IA ) in dentate granule cells in hippocampal slices obtained 1-17 days after hypoxia treatment. KEY FINDINGS Seizure-inducing hypoxia resulted in decreased maximum IA amplitude in dentate granule cells recorded within the first week but not at later times after hypoxia treatment. The decreased IA amplitude was not associated with changes in the voltage-dependence of activation or inactivation removal, or in sensitivity to inhibition by 4-aminopyridine (4-AP). However, consistent with the role of IA in shaping firing patterns, we observed in the hypoxia group a significantly decreased latency to first spike with depolarizing current injection from hyperpolarized potentials. These differences were not associated with changes in resting membrane potential or input resistance, and were eliminated by application of 10 m 4-AP. SIGNIFICANCE Given the role of IA to slow action potential firing, decreased IA could contribute to long-term hippocampal pathology after neonatal seizure-inducing hypoxia by increasing dentate granule cell excitability during a critical window of activity-dependent hippocampal maturation.
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Affiliation(s)
- Bi-Wen Peng
- Department of Physiology, Wuhan University School of Basic Medical Sciences, Wuhan, Hubei, China
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Abstract
The human brain is a tremendously complex and still enigmatic three-dimensional structure, composed of countless interconnected neurons and glia. The temporal evolution of the brain throughout life provides a fourth dimension, one that influences every element of the brain's function in health and disease. This temporal evolution contributes to the probability of seizure generation and to the type and the nature of these seizures. The age-specific properties of the brain also influence the consequences of seizures on neuronal structure and behavior. These, in turn, govern epileptic activity and cognitive and emotional functions, contributing to the diverse consequences of seizures and epilepsy throughout life.
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Abstract
Benign epilepsy with centrotemporal spikes, early-onset childhood occipital epilepsy (Panayiotopoulos syndrome [PS]) and late-onset childhood occipital epilepsy (Gastaut type [LOCE-G]) are the principal pediatric focal epilepsy syndromes. They share major common characteristics: the appearance and resolution of electroclinical features are age related, there is a strong genetic predisposition, the clinical course is often mild with infrequent and easy to control seizures, interictal epileptiform activity is disproportionately abundant when compared with the clinical correlate, and tends to potentiate and generalize during sleep. In this review, we outline the relevant pathophysiology underlying this electroclinical spectrum. Then, the initial description of individual syndromes is followed by a summary of overlapping features and intermediate presentations that question the boundaries between these entities and provide the basis for the concept of a childhood seizure susceptibility syndrome. Additionally, we outline the main features of the related epileptic encephalopathies. An outlook on potential future lines of research completes this review.
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Abstract
BACKGROUND Neonatal seizures can result in chronic epilepsy and long-term behavioral and cognitive deficits. Levetiracetam (LEV), an antiepileptic drug that binds to the synaptic vesicle protein 2A (SV2A), has been increasingly used off-label for the therapy of neonatal seizures. Preclinical data regarding the acute or long-term efficacy of LEV are lacking. METHODS We tested the anticonvulsant efficacy of LEV in a rat model of hypoxia-induced neonatal seizures. In addition, we evaluated the protective effects of postnatal day (P)10 LEV treatment on later-life kainic acid (KA)-induced seizure susceptibility and seizure-induced neuronal injury. Western blot and immunohistochemistry were used to assess the developmental regulation of SV2A in the rat and human brain. RESULTS LEV pretreatment at P10 significantly decreased the cumulative duration of behavioral and electrographic seizures at both 25 and 50 mg/kg. At P40, KA-induced seizures and neuronal loss were significantly diminished in rats previously treated with LEV. LEV target SV2A is present in both neonatal rat and human brain and increases steadily to adulthood. CONCLUSION LEV suppressed acute seizures induced by perinatal hypoxia and diminished later-life seizure susceptibility and seizure-induced neuronal injury, providing evidence for disease modification. These results support consideration of a clinical trial of LEV in neonatal seizures.
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Rajasekaran K, Todorovic M, Kapur J. Calcium-permeable AMPA receptors are expressed in a rodent model of status epilepticus. Ann Neurol 2012; 72:91-102. [PMID: 22829271 DOI: 10.1002/ana.23570] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE A study was undertaken to characterize the plasticity of AMPA receptor (AMPAR)-mediated neurotransmission in the hippocampus during status epilepticus (SE). METHODS SE was induced by pilocarpine, and animals were studied 10 minutes (refractory SE) or 60 minutes (late SE) after the onset of the first grade 5 seizures. AMPAR-mediated currents were recorded from CA1 pyramidal neurons and dentate granule cells (DGCs) by voltage clamp technique. The surface expression of GluA2 subunit on hippocampal membranes was determined using a biotinylation assay. GluA2 internalization and changes in intracellular calcium ([Ca](i)) levels were studied in hippocampal cultures using immunocytochemical and live-imaging techniques. AMPAR antagonist treatment of SE was evaluated by video and electroencephalography. RESULTS AMPAR-mediated currents recorded from CA1 neurons from refractory and late SE animals were inwardly rectifying, and philanthotoxin-sensitive; similar changes were observed in recordings obtained from DGCs from refractory SE animals. GluA2 subunit surface expression was reduced in the hippocampus during refractory and late SE. In cultured hippocampal pyramidal neurons, recurrent bursting diminished surface expression of the GluA2 subunit and enhanced its internalization rate. Recurrent bursting-induced increase in [Ca](i) levels was reduced by selective inhibition of GluA2-lacking AMPARs. GYKI-52466 terminated diazepam-refractory SE. INTERPRETATION During SE, there is rapid, ongoing plasticity of AMPARs with the expression of GluA2-lacking AMPARs. These receptors provide another source of Ca(2+) entry into the principal neurons. Benzodiazepam-refractory SE can be terminated by AMPAR antagonism. The data identify AMPARs as a potential therapeutic target for the treatment of SE.
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Yatsenko L, Pozdnyakova N, Dudarenko M, Himmelreich N. The dynamics of changes in hippocampal GABAergic system in rats exposed to early-life hypoxia-induced seizures. Neurosci Lett 2012; 524:69-73. [PMID: 22841699 DOI: 10.1016/j.neulet.2012.07.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Revised: 07/02/2012] [Accepted: 07/11/2012] [Indexed: 10/28/2022]
Abstract
Hypoxia-evoked seizures (H/S) early in life lead to multiple chronic neurological deficits. Here, we present the results of studying GABA release and uptake in hippocampal axon terminals of rats exposed to H/S at 10-12 days of age. We characterized (i) exocytotic release of GABA; (ii) the initial rate of GABA uptake; (iii) the regulation of GABA release by presynaptic GABA(B) receptors. Rats were used for experiments 2, 4 and 8 weeks after H/S. We found that exocytotic [(3)H]GABA release was higher in rats exposed to H/S, and a maximal difference in the release was observed between the control and experimental rats tested 2 weeks after H/S. In contrast, the initial rate of GABA uptake decreased with age, and this tendency was more pronounced in rats exposed to H/S. Using (±)-baclofen and SKF 97541 as agonists of GABA(B) receptor, we revealed that a significant difference in the auto-inhibition of exocytotic [(3)H]GABA release was detected only between the control and experimental adult rats (8 weeks after hypoxia). The inhibitory effect dropped dramatically in the control adults, but only slightly decreased in adult rats exposed to H/S, thus becoming threefold more potent after hypoxic injury. Together, the results show that H/S affects the dynamics of age-dependent changes in the GABAergic system, and that the enhanced GABA(B) receptor-mediated auto-inhibition can be an important factor in weakening the postsynaptic inhibition and in the development of hyperexcitability in rats exposed to H/S.
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Affiliation(s)
- L Yatsenko
- Department of Neurochemistry, Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Leontovich Str. 9, Kyiv 01601, Ukraine
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Xiang K, Earl D, Dwyer T, Behrle BL, Tietz EI, Greenfield LJ. Hypoxia enhances high-voltage-activated calcium currents in rat primary cortical neurons via calcineurin. Epilepsy Res 2012; 99:293-305. [PMID: 22245138 PMCID: PMC3341530 DOI: 10.1016/j.eplepsyres.2011.12.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Revised: 12/04/2011] [Accepted: 12/18/2011] [Indexed: 01/09/2023]
Abstract
Hypoxia regulates neuronal ion channels, sometimes resulting in seizures. We evaluated the effects of brief sustained hypoxia (1% O(2), 4h) on voltage-gated calcium channels (VGCCs) in cultured rat primary cortical neurons. High-voltage activated (HVA) Ca(2+) currents were acquired immediately after hypoxic exposure or after 48h recovery in 95% air/5% CO(2). Maximal Ca(2+) current density increased 1.5-fold immediately after hypoxia, but reverted to baseline after 48h normoxia. This enhancement was primarily due to an increase in L-type VGCC activity, since nimodipine-insensitive residual Ca(2+) currents were unchanged. The half-maximal potentials of activation and steady-state inactivation were unchanged. The calcineurin inhibitors FK-506 (in the recording pipette) or cyclosporine A (during hypoxia) prevented the post-hypoxic increase in HVA Ca(2+) currents, while rapamycin and okadaic acid did not. L-type VGCCs were the source of Ca(2+) for calcineurin activation, as nimodipine during hypoxia prevented post-hypoxic enhancement. Hypoxia transiently potentiated L-type VGCC currents via calcineurin, suggesting a positive feedback loop to amplify neuronal calcium signaling that may contribute to seizure generation.
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Affiliation(s)
- Kun Xiang
- Department of Neurology, University of Toledo College of Medicine, Toledo, OH, USA
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Hypoxia-induced neonatal seizures diminish silent synapses and long-term potentiation in hippocampal CA1 neurons. J Neurosci 2012; 31:18211-22. [PMID: 22171027 DOI: 10.1523/jneurosci.4838-11.2011] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Neonatal seizures can lead to epilepsy and long-term cognitive deficits into adulthood. Using a rodent model of the most common form of human neonatal seizures, hypoxia-induced seizures (HS), we aimed to determine whether these seizures modify long-term potentiation (LTP) and silent NMDAR-only synapses in hippocampal CA1. At 48-72 h after HS, electrophysiology and immunofluorescent confocal microscopy revealed a significant decrease in the incidence of silent synapses, and an increase in AMPARs at the synapses. Coincident with this decrease in silent synapses, there was an attenuation of LTP elicited by either tetanic stimulation of Schaffer collaterals or a pairing protocol, and persistent attenuation of LTP in slices removed in later adulthood after P10 HS. Furthermore, postseizure treatment in vivo with the AMPAR antagonist 2,3-dihydroxy-6-nitro-7-sulfonyl-benzo[f]quinoxaline (NBQX) protected against the HS-induced depletion of silent synapses and preserved LTP. Thus, this study demonstrates a novel mechanism by which early life seizures could impair synaptic plasticity, suggesting a potential target for therapeutic strategies to prevent long-term cognitive deficits.
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Downregulation of hippocampal GABA after hypoxia-induced seizures in neonatal rats. Neurochem Res 2011; 36:2409-16. [PMID: 21833845 DOI: 10.1007/s11064-011-0565-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2010] [Revised: 05/28/2011] [Accepted: 07/27/2011] [Indexed: 02/04/2023]
Abstract
This study aims to determine the expression of Gamma-aminobutyric acid (GABA) following hypoxia in neonatal rats and explore how it may increase susceptibility to epilepsy later in life. A modified model of neonatal hypoxia-induced epileptic susceptibility was simulated by 17 min of hypoxia (5% O(2) and 95% N(2)) in postnatal day (P) 10 rats. Hippocampal glutamate decarboxylase (GAD) and parvalbumin (PV) during the development with or without hypoxia were examined using immunohistochemistry. No detectable neuronal loss was observed in the hippocampus either immediately or 14 days after hypoxia. During the development GAD- and PV-immunoreactivity increased substantially during P 11-13 and reached mature expression in the control rats, and decreased significantly at different time points except for a transient increase during P 11-13 in the hypoxic groups. Our study indicates that downregulation of hippocampal GABA after hypoxia-induced seizures in neonatal rats may contribute to higher epileptic susceptibility in later life.
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Kim KH, Pessah IN. Perinatal exposure to environmental polychlorinated biphenyls sensitizes hippocampus to excitotoxicity ex vivo. Neurotoxicology 2011; 32:981-5. [PMID: 21571002 DOI: 10.1016/j.neuro.2011.04.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2011] [Revised: 04/12/2011] [Accepted: 04/14/2011] [Indexed: 11/16/2022]
Abstract
Ortho-substituted polychlorinated biphenyls (PCBs) are a concern to human developmental health. Rat dams were exposed to an environmentally relevant mixture of PCBs, Aroclor 1254, or pure congener PCB 95 (6 mg/kg/day) during the perinatal period (GD 5 through PD 21). Hippocampal slices prepared from offspring 1-3 weeks post-weaning were tested for persisting changes in sensitivity to the excitotoxicant picrotoxin. Hippocampal slices were placed on multielectrode arrays. Field excitatory postsynaptic potentials (fEPSPs) were recorded from Schaffer Collateral/Commissural fibers in striatum radiatum of the CA1 region in response to single pulse stimuli. After recording baseline excitability, GABA(A) receptors were blocked by inclusion of picrotoxin (100 μM) in the aCSF perfusate. Picrotoxin produced negligible changes in fEPSP slope in slices isolated from offspring exposed to vehicle, whereas slices from either PCB test group invariably showed >200% (p<0.01) synaptic facilitation. Picrotoxin produced prominent after-discharges (epileptic wave forms) in the evoked potentials measured from PCB exposed, but not control, hippocampal slices. These results show that developmental exposure to non-coplanar PCBs is sufficient to produce changes in synaptic plasticity that can be unmasked in the presence of GABA(A) receptor deficits that persist 1-3 weeks after exposure ceased. Developmental exposure to PCBs may sensitize seizure susceptibility postnatally, especially in susceptible populations with GABA(A) receptor signaling deficits.
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Affiliation(s)
- Kyung Ho Kim
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, One Shields Avenue, Davis, CA 95616, USA
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Rakhade SN, Klein PM, Huynh T, Hilario-Gomez C, Kosaras B, Rotenberg A, Jensen FE. Development of later life spontaneous seizures in a rodent model of hypoxia-induced neonatal seizures. Epilepsia 2011; 52:753-65. [PMID: 21366558 DOI: 10.1111/j.1528-1167.2011.02992.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE To study the development of epilepsy following hypoxia-induced neonatal seizures in Long-Evans rats and to establish the presence of spontaneous seizures in this model of early life seizures. METHODS Long-Evans rat pups were subjected to hypoxia-induced neonatal seizures at postnatal day 10 (P10). Epidural cortical electroencephalography (EEG) and hippocampal depth electrodes were used to detect the presence of seizures in later adulthood (> P60). In addition, subdermal wire electrode recordings were used to monitor age at onset and progression of seizures in the juvenile period, at intervals between P10 and P60. Timm staining was performed to evaluate mossy fiber sprouting in the hippocampi of P100 adult rats that had experienced neonatal seizures. KEY FINDINGS In recordings made from adult rats (P60-180), the prevalence of epilepsy in cortical and hippocampal EEG recordings was 94.4% following early life hypoxic seizures. These spontaneous seizures were identified by characteristic spike and wave activity on EEG accompanied by behavioral arrest and facial automatisms (electroclinical seizures). Phenobarbital injection transiently abolished spontaneous seizures. EEG in the juvenile period (P10-60) showed that spontaneous seizures first occurred approximately 2 weeks after the initial episode of hypoxic seizures. Following this period, spontaneous seizure frequency and duration increased progressively with time. Furthermore, significantly increased sprouting of mossy fibers was observed in the CA3 pyramidal cell layer of the hippocampus in adult animals following hypoxia-induced neonatal seizures. Notably, Fluoro-Jade B staining confirmed that hypoxic seizures at P10 did not induce acute neuronal death. SIGNIFICANCE The rodent model of hypoxia-induced neonatal seizures leads to the development of epilepsy in later life, accompanied by increased mossy fiber sprouting. In addition, this model appears to exhibit a seizure-free latent period, following which there is a progressive increase in the frequency of electroclinical seizures.
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Affiliation(s)
- Sanjay N Rakhade
- Department of Neurology, Children's Hospital Boston and Harvard Medical School, Boston, Massachusetts, USA
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Baram TZ, Jensen FE, Brooks-Kayal A. Does acquired epileptogenesis in the immature brain require neuronal death. Epilepsy Curr 2011; 11:21-6. [PMID: 21461261 PMCID: PMC3063568 DOI: 10.5698/1535-7511-11.1.21] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Because epilepsy often occurs during development, understanding the mechanisms by which this process takes place (epileptogenesis) is important. In addition, the age-specificity of seizures and epilepsies of the neonatal, infancy, and childhood periods suggests that the processes and mechanisms that culminate in epilepsy might be age specific as well. Here we provide an updated review of recent and existing literature and discuss evidence that neuronal loss may occur during epileptogenesis in the developing brain, but is not required for the epileptogenic process. We speculate about the mechanisms for the resilience of neurons in immature limbic structures to epileptogenic insults, and propose that the type, duration and severity of these insults influence the phenomenology of the resulting spontaneous seizures.
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Affiliation(s)
- Tallie Z Baram
- Departments of Anatomy/Neurobiology and Pediatrics, University of California Irvine, Irvine, CA
| | - Frances E Jensen
- Children's Hospital Boston and Harvard Medical School, Neurology, Boston, MA
| | - Amy Brooks-Kayal
- Pediatrics and Neurology, University of Colorado Denver School of Medicine and The Children's Hospital Denver and Aurora, CO
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Giblin KA, Blumenfeld H. Is epilepsy a preventable disorder? New evidence from animal models. Neuroscientist 2010; 16:253-75. [PMID: 20479472 DOI: 10.1177/1073858409354385] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Epilepsy accounts for 0.5% of the global burden of disease, and primary prevention of epilepsy represents one of the three 2007 NINDS Epilepsy Research Benchmarks. In the past decade, efforts to understand and intervene in the process of epileptogenesis have yielded fruitful preventative strategies in animal models.This article reviews the current understanding of epileptogenesis, introduces the concept of a "critical period" for epileptogenesis, and examines strategies for epilepsy prevention in animal models of both acquired and genetic epilepsies. We discuss specific animal models, which may yield important insights into epilepsy prevention including kindling, poststatus epilepticus, prolonged febrile seizures, traumatic brain injury, hypoxia, the tuberous sclerosis mouse model, and the WAG/Rij rat model of primary generalized epilepsy. Hopefully, further investigation of antiepileptogenesis in animal models will soon enable human therapeutic trials to be initiated, leading to long-term epilepsy prevention and improved patient quality of life.
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Affiliation(s)
- Kathryn A Giblin
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06520-8018, USA
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Rajasekaran K, Zanelli SA, Goodkin HP. Lessons from the laboratory: the pathophysiology, and consequences of status epilepticus. Semin Pediatr Neurol 2010; 17:136-43. [PMID: 20727481 PMCID: PMC2943667 DOI: 10.1016/j.spen.2010.06.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Status epilepticus (SE) is the most common neurologic emergency of childhood. Experimental models parallel several clinical features of SE including (1) treatment is complicated by an increasing probability that benzodiazepines will fail with increasing seizure duration and (2) outcome varies with age and etiology. Studies using these models showed that the activity-dependent trafficking of GABA(A) receptors contributes in part to the progressive decline in GABA-mediated inhibition and the failure of the benzodiazepines. Furthermore, laboratory studies have provided evidence that age and inciting stimulus interact to determine the neuronal circuits activated during SE (ie, functional anatomy) and that differences in functional anatomy can partially account for variations in SE outcome. Future laboratory studies are likely to provide an additional understanding of the cellular and molecular mechanisms that underlie SE and its consequences. Such studies are necessary in the development of rational emergent therapy for SE and its long-term outcomes.
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Affiliation(s)
| | | | - Howard P Goodkin
- Department of Neurology, University of Virginia, Charlottesville, VA, Department of Pediatrics, University of Virginia, Charlottesville, VA
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Abstract
Kainate Seizures Cause Acute Dendritic Injury and Actin Depolymerization In Vivo. Zeng LH, Xu L, Rensing NR, Sinatra PM, Rothman SM, Wong M. J Neurosci 2007;27(43):11604–11613. Seizures may cause brain injury via a variety of mechanisms, potentially contributing to cognitive deficits in epilepsy patients. Although seizures induce neuronal death in some situations, they may also have “nonlethal” pathophysiological effects on neuronal structure and function, such as modifying dendritic morphology. Previous studies involving conventional fixed tissue analysis have demonstrated a chronic loss of dendritic spines after seizures in animal models and human tissue. More recently, in vivo time-lapse imaging methods have been used to monitor acute changes in spines directly during seizures, but documented spine loss only under severe conditions. Here, we examined effects of secondary generalized seizures induced by kainate, on dendritic structure of neocortical neurons using multiphoton imaging in live mice in vivo and investigated molecular mechanisms mediating these structural changes. Higher-stage kainate-induced seizures caused dramatic dendritic beading and loss of spines within minutes, in the absence of neuronal death or changes in systemic oxygenation. Although the dendritic beading improved rapidly after the seizures, the spine loss recovered only partially over a 24 h period. Kainate seizures also resulted in activation of the actin-depolymerizing factor, cofilin, and a corresponding decrease in filamentous actin, indicating that depolymerization of actin may mediate the morphological dendritic changes. Finally, an inhibitor of the calcium-dependent phosphatase, calcineurin, antagonized the effects of seizures on cofilin activation and spine morphology. These dramatic in vivo findings demonstrate that seizures produce acute dendritic injury in neocortical neurons via calcineurin-dependent regulation of the actin cytoskeleton, suggesting novel therapeutic targets for preventing seizure-induced brain injury.
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Downregulation of dendritic HCN channel gating in epilepsy is mediated by altered phosphorylation signaling. J Neurosci 2010; 30:6678-88. [PMID: 20463230 DOI: 10.1523/jneurosci.1290-10.2010] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The onset of spontaneous seizures in the pilocarpine model of epilepsy causes a hyperpolarized shift in the voltage-dependent activation of hyperpolarization-activated cyclic nucleotide-gated (HCN) channel-mediated current (Ih) in CA1 hippocampal pyramidal neuron dendrites, contributing to neuronal hyperexcitability and possibly to epileptogenesis. However, the specific mechanisms by which spontaneous seizures cause downregulation of HCN channel gating are yet unknown. We asked whether the seizure-dependent downregulation of HCN channel gating was due to altered phosphorylation signaling mediated by the phosphatase calcineurin (CaN) or the kinase p38 mitogen-activated protein kinase (p38 MAPK). We first found that CaN inhibition upregulated HCN channel gating and reduced neuronal excitability under normal conditions, showing that CaN is a strong modulator of HCN channels. We then found that an in vitro model of seizures (1 h in 0 Mg2+ and 50 microM bicuculline at 35-37 degrees C) reproduced the HCN channel gating change seen in vivo. Pharmacological inhibition of CaN or activation of p38 MAPK partially reversed the in vitro seizure-induced hyperpolarized shift in HCN channel gating, and the shift was fully reversed by the combination of CaN inhibition and p38 MAPK activation. We then demonstrated enhanced CaN activity as well as reduced p38 MAPK activity in vivo in the CA1 hippocampal area of chronically epileptic animals. Pharmacological reversal of these phosphorylation changes restored HCN channel gating downregulation and neuronal hyperexcitability in epileptic tissue to control levels. Together, these results suggest that alteration of two different phosphorylation pathways in epilepsy contributes to the downregulation of HCN channel gating, which consequently produces neuronal hyperexcitability and thus may be a target for novel antiepileptic therapies.
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Abstract
AMPA/Kainate Receptor–mediated Downregulation of GABAergic Synaptic Transmission by Calcineurin after Seizures in the Developing Rat Brain Sanchez RM, Dai W, Levada RE, Lippman JJ, Jensen FE J Neurosci 2005;25:3442–3451 Hypoxia is the most common cause of perinatal seizures and can be refractory to conventional anticonvulsant drugs, suggesting an age-specific form of epileptogenesis. A model of hypoxia-induced seizures in immature rats reveals that seizures result in immediate activation of the phosphatase calcineurin (CaN) in area CA1 of hippocampus. After seizures, CA1 pyramidal neurons exhibit a downregulation of GABAA receptor (GABAAR)-mediated inhibition that was reversed by CaN inhibitors. CaN activation appears to be dependent on seizure-induced activation of Ca2+-permeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors (AMPARs), because the upregulation of CaN activation and GABAAR inhibition were attenuated by GYKI 52466 [1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine hydrochloride] or Joro spider toxin. GABAAR β2/3 subunit protein was dephosphorylated at 1 h after seizures, suggesting this subunit as a possible substrate of CaN in this model. Finally, in vivo administration of the CaN inhibitor FK-506 significantly suppressed hypoxic seizures, and posttreatment with NBQX (2,3-dihydroxy-6-nitro-7-sulfonylbenzo[ f]quinoxaline) or FK-506 blocked the hypoxic seizure-induced increase in CaN expression. These data suggest that Ca2+-permeable AMPARs and CaN regulate inhibitory synaptic transmission in a novel plasticity pathway that may play a role in epileptogenesis in the immature brain.
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Isaeva E, Isaev D, Savrasova A, Khazipov R, Holmes GL. Recurrent neonatal seizures result in long-term increases in neuronal network excitability in the rat neocortex. Eur J Neurosci 2010; 31:1446-55. [PMID: 20384780 DOI: 10.1111/j.1460-9568.2010.07179.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Neonatal seizures are associated with a high likelihood of adverse neurological outcomes, including mental retardation, behavioral disorders, and epilepsy. Early seizures typically involve the neocortex, and post-neonatal epilepsy is often of neocortical origin. However, our understanding of the consequences of neonatal seizures for neocortical function is limited. In the present study, we show that neonatal seizures induced by flurothyl result in markedly enhanced susceptibility of the neocortex to seizure-like activity. This change occurs in young rats studied weeks after the last induced seizure and in adult rats studied months after the initial seizures. Neonatal seizures resulted in reductions in the amplitude of spontaneous inhibitory postsynaptic currents and the frequency of miniature inhibitory postsynaptic currents, and significant increases in the amplitude and frequency of spontaneous excitatory postsynaptic currents (sEPSCs) and in the frequency of miniature excitatory postsynaptic currents (mEPSCs) in pyramidal cells of layer 2/3 of the somatosensory cortex. The selective N-methyl-D-aspartate (NMDA) receptor antagonist D-2-amino-5-phosphonovalerate eliminated the differences in amplitude and frequency of sEPSCs and mEPSCs in the control and flurothyl groups, suggesting that NMDA receptors contribute significantly to the enhanced excitability seen in slices from rats that experienced recurrent neonatal seizures. Taken together, our results suggest that recurrent seizures in infancy result in a persistent enhancement of neocortical excitability.
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Affiliation(s)
- Elena Isaeva
- Department of Neurology, Neuroscience Center at Dartmouth, Dartmouth Medical School, Lebanon, NH 03756, USA.
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Abstract
Epileptogenesis is defined as the process of developing epilepsy-a disorder characterized by recurrent seizures-following an initial insult. Seizure incidence during the human lifespan is at its highest in infancy and childhood. Animal models of epilepsy and human tissue studies suggest that epileptogenesis involves a cascade of molecular, cellular and neuronal network alterations. Within minutes to days following the initial insult, there are acute early changes in neuronal networks, which include rapid alterations to ion channel kinetics as a result of membrane depolarization, post-translational modifications to existing functional proteins, and activation of immediate early genes. Subacute changes occur over hours to weeks, and include transcriptional events, neuronal death and activation of inflammatory cascades. The chronic changes that follow over weeks to months include anatomical changes, such as neurogenesis, mossy fiber sprouting, network reorganization, and gliosis. These epileptogenic processes are developmentally regulated and might contribute to differences in epileptogenesis between adult and developing brains. Here we review the factors responsible for enhanced seizure susceptibility in the developing brain, and consider age-specific mechanisms of epileptogenesis. An understanding of these factors could yield potential therapeutic targets for the prevention of epileptogenesis and also provide biomarkers for identifying patients at risk of developing epilepsy or for monitoring disease progression.
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Abstract
The lifespan risk of seizures is highest in the neonatal period. Current therapies have limited efficacy. Although the treatment of neonatal seizures has not changed significantly in the last several decades, there has been substantial progress in understanding developmental mechanisms that influence seizure generation and responsiveness to anticonvulsants. This article provides an overview of current approaches to the diagnosis and treatment of neonatal seizures, and some of the recent insights about the pathophysiology of neonatal seizures that may provide the foundation for better treatment are identified.
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Affiliation(s)
- Frances E Jensen
- Children's Hospital Boston, CLS 14073, 300 Longwood Avenue, Boston, MA 02115, USA.
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43
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Nagarkatti N, Deshpande LS, DeLorenzo RJ. Development of the calcium plateau following status epilepticus: role of calcium in epileptogenesis. Expert Rev Neurother 2009; 9:813-24. [PMID: 19496685 DOI: 10.1586/ern.09.21] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Status epilepticus is a clinical emergency defined as continuous seizure activity or rapid, recurrent seizures without regaining consciousness and can lead to the development of acquired epilepsy, characterized by spontaneous, recurrent seizures. Understanding epileptogenesis--the transformation of healthy brain tissue into hyperexcitable neuronal networks--is an important challenge and the elucidation of molecular mechanisms can lend insight into new therapeutic targets to halt this progression. It has been demonstrated that intracellular calcium increases during status epilepticus and that these elevations are maintained past the duration of the injury (Ca(2+) plateau). As an important second messenger, Ca(2+) elevations can lead to changes in gene expression, neurotransmitter release and plasticity. Thus, characterization of the post-injury Ca(2+) plateau may be important in eventually understanding the pathophysiology of epileptogenesis and preventing the progression to chronic epilepsy after brain injury.
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Affiliation(s)
- Nisha Nagarkatti
- Department of , Virginia Commonwealth University, Richmond, VA 23298, USA.
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44
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Activity-dependent tuning of inhibitory neurotransmission based on GABAAR diffusion dynamics. Neuron 2009; 62:670-82. [PMID: 19524526 DOI: 10.1016/j.neuron.2009.04.023] [Citation(s) in RCA: 234] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Revised: 02/11/2009] [Accepted: 04/21/2009] [Indexed: 11/20/2022]
Abstract
An activity-dependent change in synaptic efficacy is a central tenet in learning, memory, and pathological states of neuronal excitability. The lateral diffusion dynamics of neurotransmitter receptors are one of the important parameters regulating synaptic efficacy. We report here that neuronal activity modifies diffusion properties of type-A GABA receptors (GABA(A)R) in cultured hippocampal neurons: enhanced excitatory synaptic activity decreases the cluster size of GABA(A)Rs and reduces GABAergic mIPSC. Single-particle tracking of the GABA(A)R gamma2 subunit labeled with quantum dots reveals that the diffusion coefficient and the synaptic confinement domain size of GABA(A)R increases in parallel with neuronal activity, depending on Ca(2+) influx and calcineurin activity. These results indicate that GABA(A)R diffusion dynamics are directly linked to rapid and plastic modifications of inhibitory synaptic transmission in response to changes in intracellular Ca(2+) concentration. This transient activity-dependent reduction of inhibition would favor the onset of LTP during conditioning.
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45
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Wang A, Chi Z, Wang S, Wang S, Sun Q. Calcineurin-mediated GABA(A) receptor dephosphorylation in rats after kainic acid-induced status epilepticus. Seizure 2009; 18:519-23. [PMID: 19497770 DOI: 10.1016/j.seizure.2009.05.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2008] [Revised: 04/15/2009] [Accepted: 05/07/2009] [Indexed: 11/17/2022] Open
Abstract
Calcineurin (CaN) is a neuronally enriched, calcium-dependent phosphatase, which plays an important role in a number of neuronal processes including development of learning and memory, and modulation of receptor's function and neuronal excitability as well as induction of apoptosis. It has been established in kindling model that the status epilepticus (SE)-induced increase in CaN activity is involved in the development of seizures through down-regulation of gamma-aminobutyric acid A receptor (GABA(A)R) activation. However, the mechanism by which CaN mediates GABA(A) receptor dephosphorylation in SE is not fully understood. Here, using a model of kainic acid (KA)-induced SE and CaN inhibitor FK506, we observed the behaviors induced by KA and levels of CaN activity and CaN expression in hippocampus by immunobloting. The results showed that the SE-induced CaN activity was time-dependent, with a peak at 2h and a return to basal level at 24h, whereas a significant increase in CaN expression was seen at 24h after SE. It is proposed that the rapid elevation in CaN activity after KA-induced SE is not likely due to an increase in CaN expression but rather an increase in CaN activation state or kinetics. In addition, we also demonstrated that pre-treatment with FK506 remarkably suppressed the SE-induced CaN activity and its expression, and reversed the SE-induced dephosphorylation of GABA(A)R 2/3 subunits. Taken together, our data suggest that down-regulation in inhibition of GABA(A)R 2/3 by CaN activity contributes to an elevation in neuronal excitability of hippocampus, which may be involved in development of chronic processes of seizures.
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Affiliation(s)
- Aihua Wang
- Department of Neurology, Qianfoshan Hospital, Medical School of Shandong University, No. 66, Jingshi Road, Jinan, Shandong 250014, PR China.
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Febrile seizures: mechanisms and relationship to epilepsy. Brain Dev 2009; 31:366-71. [PMID: 19232478 PMCID: PMC2698702 DOI: 10.1016/j.braindev.2008.11.010] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Revised: 10/23/2008] [Accepted: 11/04/2008] [Indexed: 12/31/2022]
Abstract
Studies of febrile seizures have been driven by two major enigmas: first, how these most common of human seizures are generated by fever has not been known. Second, epidemiological studies have linked prolonged febrile seizures with the development of temporal lobe epilepsy, yet whether long or recurrent febrile seizures cause temporal lobe epilepsy has remained unresolved. To investigate these questions, a model of prolonged (complex) febrile seizures was developed in immature rats and mice, permitting mechanistic examination of the potential causal relationships of fever and seizures, and of febrile seizures and limbic epilepsy. Although the model relied on hyperthermia, it was discovered that the hyperthermia-induced secretion of endogenous fever mediators including interleukin-1beta, which contributed to the generation of these 'febrile' seizures. In addition, prolonged experimental febrile seizures provoked epilepsy in a third of the animals. Investigations of the mechanisms of this epileptogenesis demonstrated that expression of specific ion (HCN) channels and of endocannabinoid signaling, may be involved. These may provide novel drug targets for intervention in the epileptogenic process.
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47
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Dyhrfjeld-Johnsen J, Morgan RJ, Soltesz I. Double Trouble? Potential for Hyperexcitability Following Both Channelopathic up- and Downregulation of I(h) in Epilepsy. Front Neurosci 2009; 3:25-33. [PMID: 19753094 PMCID: PMC2695388 DOI: 10.3389/neuro.01.005.2009] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2009] [Accepted: 03/04/2009] [Indexed: 11/13/2022] Open
Abstract
Studies of pathological ion channel regulation as an underlying mechanism of epilepsy have revealed alterations in the h-current in several animal models. While earlier reports indicate that downregulation of the h-current is pro-excitatory on the single neuron level, we found an upregulation of I(h) in hyperexcitable CA1 pyramidal neuron dendrites following experimental febrile seizures. In addition, in several CA1 pyramidal neuron computational models of different complexity, h-current upregulation has been shown to lead to pro-excitable effects. This focused review examines the complex impact of altered h-current on neuronal resting membrane potential (RMP) and input resistance (R(in)), as well as reported interactions with other ionic conductances.
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48
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Jacobs MP, Leblanc GG, Brooks-Kayal A, Jensen FE, Lowenstein DH, Noebels JL, Spencer DD, Swann JW. Curing epilepsy: progress and future directions. Epilepsy Behav 2009; 14:438-45. [PMID: 19341977 PMCID: PMC2822433 DOI: 10.1016/j.yebeh.2009.02.036] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2009] [Accepted: 02/14/2009] [Indexed: 01/10/2023]
Abstract
During the past decade, substantial progress has been made in delineating clinical features of the epilepsies and the basic mechanisms responsible for these disorders. Eleven human epilepsy genes have been identified and many more are now known from animal models. Candidate targets for cures are now based upon newly identified cellular and molecular mechanisms that underlie epileptogenesis. However, epilepsy is increasingly recognized as a group of heterogeneous syndromes characterized by other conditions that co-exist with seizures. Cognitive, emotional and behavioral co-morbidities are common and offer fruitful areas for study. These advances in understanding mechanisms are being matched by the rapid development of new diagnostic methods and therapeutic approaches. This article reviews these areas of progress and suggests specific goals that once accomplished promise to lead to cures for epilepsy.
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Affiliation(s)
- Margaret P. Jacobs
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Rockville, MD, USA
| | - Gabrielle G. Leblanc
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Rockville, MD, USA
| | - Amy Brooks-Kayal
- Neurology and Pediatrics, University of Pennsylvania, Philadelphia, PA, USA
| | | | - Dan H. Lowenstein
- Department of Neurology, Box 0114, University of California, San Francisco, San Francisco, CA, USA
| | | | - Dennis D. Spencer
- Department of Neurosurgery, Yale University, School of Medicine, New Haven, CT, USA
| | - John W. Swann
- Baylor College of Medicine, Texas Children’s Hospital, Houston, TX, USA
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Thibeault-Eybalin MP, Lortie A, Carmant L. Neonatal seizures: do they damage the brain? Pediatr Neurol 2009; 40:175-80. [PMID: 19218030 DOI: 10.1016/j.pediatrneurol.2008.10.026] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Revised: 10/01/2008] [Accepted: 10/01/2008] [Indexed: 01/10/2023]
Abstract
Seizures are an early sign of brain injury in newborns. These seizures are in most cases repetitive or associated with asymptomatic electrographic seizures. Despite the relative resistance of the immature brain to seizure-induced brain damage, there is more and more evidence that neonatal seizures impair normal brain development. This review addresses the changes associated with neonatal seizures and discusses current and future potential neuroprotective strategies.
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Aujla PK, Fetell MR, Jensen FE. Talampanel suppresses the acute and chronic effects of seizures in a rodent neonatal seizure model. Epilepsia 2009; 50:694-701. [PMID: 19220413 DOI: 10.1111/j.1528-1167.2008.01947.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
PURPOSE To test the efficacy of the novel candidate anticonvulsant talampanel (GYKI 53773) in a rodent model of hypoxic neonatal seizures. Talampanel is a noncompetitive antagonist of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid subtype of the glutamate receptor (AMPAR). We have previously shown that AMPARs play a critical role in the generation of acute seizures and later-life seizure susceptibility in this model of neonatal seizures. METHODS Seizures were induced in postnatal day (P) 10 Long-Evans rat pups by a 15 min exposure to global hypoxia. Acute seizure activity at P10 and subsequent susceptibility to seizure-induced neuronal injury with a "second-hit" kainate-induced seizure at P30-31 were compared between animals receiving talampanel (1, 5, 7.5, or 10 mg/kg) intraperitoneally (i.p.) versus saline vehicle treatment. RESULTS Talampanel treatment suppressed seizures in a dose-dependent manner, with maximal effect at 7.5 and 10 mg/kg. In addition, talampanel treatment 30 min before hypoxia prevented later-life increases in seizure-induced neuronal injury as assessed by in situ DNA nick end-labeling (ISEL). DISCUSSION We have previously demonstrated efficacy of other AMPAR antagonists such as NBQX and topiramate in this model. The present finding shows that the novel agent talampanel, under evaluation as an antiepileptic drug in children and adults, may have clinical potential in the treatment of neonatal seizures, particularly those occurring in the context of hypoxic encephalopathy.
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Affiliation(s)
- Paven K Aujla
- Department of Neurology, Children's Hospital Boston, Boston, Massachusetts 02115, USA
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