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Faustino-Mendes T, Machado-Pereira M, Castelo-Branco M, Ferreira R. The Ischemic Immature Brain: Views on Current Experimental Models. Front Cell Neurosci 2018; 12:277. [PMID: 30210301 PMCID: PMC6123378 DOI: 10.3389/fncel.2018.00277] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2018] [Accepted: 08/08/2018] [Indexed: 01/13/2023] Open
Affiliation(s)
| | - Marta Machado-Pereira
- Faculty of Health Sciences, University of Beira Interior, Covilhã, Portugal.,Health Sciences Research Centre (CICS-UBI), University of Beira Interior, Covilhã, Portugal
| | - Miguel Castelo-Branco
- Faculty of Health Sciences, University of Beira Interior, Covilhã, Portugal.,Health Sciences Research Centre (CICS-UBI), University of Beira Interior, Covilhã, Portugal.,Hospital Center of Cova da Beira, Covilhã, Portugal
| | - Raquel Ferreira
- Faculty of Health Sciences, University of Beira Interior, Covilhã, Portugal.,Health Sciences Research Centre (CICS-UBI), University of Beira Interior, Covilhã, Portugal
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2
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Hefter D, Marti HH, Gass P, Inta D. Perinatal Hypoxia and Ischemia in Animal Models of Schizophrenia. Front Psychiatry 2018; 9:106. [PMID: 29651259 PMCID: PMC5884869 DOI: 10.3389/fpsyt.2018.00106] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 03/16/2018] [Indexed: 12/12/2022] Open
Abstract
Intrauterine or perinatal complications constitute a major risk for psychiatric diseases. Infants who suffered from hypoxia-ischemia (HI) are at twofold risk to develop schizophrenia in later life. Several animal models attempt to reproduce these complications to study the yet unknown steps between an insult in early life and outbreak of the disease decades later. However, it is very challenging to find the right type and severity of insult leading to a disease-like phenotype in the animal, but not causing necrosis and focal neurological deficits. By contrast, too mild, repetitive insults may even be protective via conditioning effects. Thus, it is not surprising that animal models of hypoxia lead to mixed results. To achieve clinically translatable findings, better protocols are urgently needed. Therefore, we compare widely used models of hypoxia and HI and propose future directions for the field.
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Affiliation(s)
- Dimitri Hefter
- RG Animal Models in Psychiatry, Department of Psychiatry and Psychotherapy, Medical Faculty Mannheim, Central Institute of Mental Health, University of Heidelberg, Heidelberg, Germany.,RG Neuro- and Sensory Physiology, Institute of Physiology and Pathophysiology, University of Heidelberg, Heidelberg, Germany
| | - Hugo H Marti
- RG Neurovascular Research, Institute of Physiology and Pathophysiology, University of Heidelberg, Heidelberg, Germany
| | - Peter Gass
- RG Animal Models in Psychiatry, Department of Psychiatry and Psychotherapy, Medical Faculty Mannheim, Central Institute of Mental Health, University of Heidelberg, Heidelberg, Germany
| | - Dragos Inta
- RG Animal Models in Psychiatry, Department of Psychiatry and Psychotherapy, Medical Faculty Mannheim, Central Institute of Mental Health, University of Heidelberg, Heidelberg, Germany.,Department of Psychiatry, University of Basel, Basel, Switzerland
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3
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Zhang X, Qu H, Wang Y, Zhao S, Xiao T, Zhao C, Teng W. Aberrant plasticity in the hippocampus after neonatal seizures. Int J Neurosci 2017; 128:384-391. [PMID: 28937832 DOI: 10.1080/00207454.2017.1384380] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Xiaoqian Zhang
- Department of Neurology, The First Hospital of China Medical University, Shenyang, Liaoning, PR China
| | - Huiling Qu
- Department of Neurology, The People's Hospital of China Medical University, Shenyang, Liaoning, PR China
| | - Ying Wang
- Department of Neurology, The First Hospital of Dalian Medical University, Dalian, Liaoning, PR China
| | - Shanshan Zhao
- Department of Neurology, The First Hospital of China Medical University, Shenyang, Liaoning, PR China
| | - Ting Xiao
- Department of Dermatology, The First Hospital of China Medical University, Shenyang, Liaoning, PR China
- Key Laboratory of Immunodermatology, Ministry of Health, Ministry of Education, Shenyang, Liaoning, PR China
| | - Chuansheng Zhao
- Department of Neurology, The First Hospital of China Medical University, Shenyang, Liaoning, PR China
| | - Weiyu Teng
- Department of Neurology, The First Hospital of China Medical University, Shenyang, Liaoning, PR China
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4
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Millar LJ, Shi L, Hoerder-Suabedissen A, Molnár Z. Neonatal Hypoxia Ischaemia: Mechanisms, Models, and Therapeutic Challenges. Front Cell Neurosci 2017; 11:78. [PMID: 28533743 PMCID: PMC5420571 DOI: 10.3389/fncel.2017.00078] [Citation(s) in RCA: 207] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 03/07/2017] [Indexed: 12/11/2022] Open
Abstract
Neonatal hypoxia-ischaemia (HI) is the most common cause of death and disability in human neonates, and is often associated with persistent motor, sensory, and cognitive impairment. Improved intensive care technology has increased survival without preventing neurological disorder, increasing morbidity throughout the adult population. Early preventative or neuroprotective interventions have the potential to rescue brain development in neonates, yet only one therapeutic intervention is currently licensed for use in developed countries. Recent investigations of the transient cortical layer known as subplate, especially regarding subplate's secretory role, opens up a novel set of potential molecular modulators of neonatal HI injury. This review examines the biological mechanisms of human neonatal HI, discusses evidence for the relevance of subplate-secreted molecules to this condition, and evaluates available animal models. Neuroserpin, a neuronally released neuroprotective factor, is discussed as a case study for developing new potential pharmacological interventions for use post-ischaemic injury.
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Affiliation(s)
- Lancelot J. Millar
- Molnár Group, Department of Physiology, Anatomy and Genetics, University of OxfordOxford, UK
| | - Lei Shi
- Molnár Group, Department of Physiology, Anatomy and Genetics, University of OxfordOxford, UK
- JNU-HKUST Joint Laboratory for Neuroscience and Innovative Drug Research, College of Pharmacy, Jinan UniversityGuangzhou, China
| | | | - Zoltán Molnár
- Molnár Group, Department of Physiology, Anatomy and Genetics, University of OxfordOxford, UK
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Rodriguez-Alvarez N, Jimenez-Mateos EM, Engel T, Quinlan S, Reschke CR, Conroy RM, Bhattacharya A, Boylan GB, Henshall DC. Effects of P2X7 receptor antagonists on hypoxia-induced neonatal seizures in mice. Neuropharmacology 2017; 116:351-363. [PMID: 28082183 DOI: 10.1016/j.neuropharm.2017.01.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Revised: 12/12/2016] [Accepted: 01/08/2017] [Indexed: 12/28/2022]
Abstract
Neonatal seizures are a common consequence of hypoxic/ischemic encephalopathy (HIE). Phenobarbital remains the frontline treatment for neonatal seizures but is often ineffective. The P2X7 receptor (P2X7R) is a cell surface-expressed ionotropic receptor activated by high amounts of ATP which may be released during seizures or as a consequence of tissue injury. Here, we explored the role of the P2X7R in a mouse model of neonatal seizures induced by hypoxia. Exposure of postnatal day 7 (P7) mouse pups to global hypoxia (5% O2 for 15 min) produced electrographically-defined seizures with behavioural correlates that persisted after restitution of normoxia. Expression of the P2X7R showed age-dependent increases in the hippocampus and neocortex of developing mice and was present in human neonatal brain. P2X7R transcript and protein levels were increased 24 h after neonatal hypoxia-induced seizures in mouse pups. EEG recordings in pups determined that injection of the P2X7R antagonist A-438079 (25 mg/kg-1, intraperitoneal) reduced electrographic seizure number, EEG power and spiking during hypoxia. A-438079 did not reduce post-hypoxia seizures. Caspase-1 processing and molecular markers of inflammation and microglia were reduced in A438079-treated mice. Electrographic seizure-suppressive effects were also observed with a second P2X7R antagonist, JNJ-47965567, in the same model. The present study shows hypoxia-induced seizures alter expression of purinergic and neuroinflammatory signalling components and suggest potential applications but also limitations of the P2X7R as a target for the treatment of HIE and other causes of neonatal seizures.
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Affiliation(s)
- Natalia Rodriguez-Alvarez
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, 123 St. Stephen's Green, Dublin 2, Ireland
| | - Eva M Jimenez-Mateos
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, 123 St. Stephen's Green, Dublin 2, Ireland
| | - Tobias Engel
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, 123 St. Stephen's Green, Dublin 2, Ireland
| | - Sean Quinlan
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, 123 St. Stephen's Green, Dublin 2, Ireland
| | - Cristina R Reschke
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, 123 St. Stephen's Green, Dublin 2, Ireland
| | - Ronán M Conroy
- Division of Population Health Sciences, Royal College of Surgeons in Ireland, Dublin, Ireland
| | | | - Geraldine B Boylan
- Irish Centre for Fetal and Neonatal Translational Research (INFANT) Cork, Ireland
| | - David C Henshall
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, 123 St. Stephen's Green, Dublin 2, Ireland; Irish Centre for Fetal and Neonatal Translational Research (INFANT) Cork, Ireland.
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6
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Farrell JS, Wolff MD, Teskey GC. Neurodegeneration and Pathology in Epilepsy: Clinical and Basic Perspectives. ADVANCES IN NEUROBIOLOGY 2017; 15:317-334. [PMID: 28674987 DOI: 10.1007/978-3-319-57193-5_12] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Epilepsy is commonly associated with a number of neurodegenerative and pathological alterations in those areas of the brain that are involved in repeated electrographic seizures. These most prominently include neuron loss and an increase in astrocyte number and size but may also include enhanced blood-brain barrier permeability, the formation of new capillaries, axonal sprouting, and central inflammation. In animal models in which seizures are either repeatedly elicited or are self-generated, a similar set of neurodegenerative and pathological alterations in brain anatomy are observed. The primary causal agent responsible for these alterations may be the cascade of events that follow a seizure and lead to an hypoperfusion/hypoxic episode. While epilepsy has long and correctly been considered an electrical disorder, the vascular system likely plays an important causal role in the neurodegeneration and pathology that occur as a consequence of repeated seizures.
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Affiliation(s)
- Jordan S Farrell
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - Marshal D Wolff
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - G Campbell Teskey
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada.
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7
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Zhou C, Sun H, Klein PM, Jensen FE. Neonatal seizures alter NMDA glutamate receptor GluN2A and 3A subunit expression and function in hippocampal CA1 neurons. Front Cell Neurosci 2015; 9:362. [PMID: 26441533 PMCID: PMC4585040 DOI: 10.3389/fncel.2015.00362] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 08/31/2015] [Indexed: 12/02/2022] Open
Abstract
Neonatal seizures are commonly caused by hypoxic and/or ischemic injury during birth and can lead to long-term epilepsy and cognitive deficits. In a rodent hypoxic seizure (HS) model, we have previously demonstrated a critical role for seizure-induced enhancement of the AMPA subtype of glutamate receptor (GluA) in epileptogenesis and cognitive consequences, in part due to GluA maturational upregulation of expression. Similarly, as the expression and function of the N-Methyl-D-aspartate (NMDA) subtype of glutamate receptor (GluN) is also developmentally controlled, we examined how early life seizures during the critical period of synaptogenesis could modify GluN development and function. In a postnatal day (P)10 rat model of neonatal seizures, we found that seizures could alter GluN2/3 subunit composition of GluNs and physiological function of synaptic GluNs. In hippocampal slices removed from rats within 48–96 h following seizures, the amplitudes of synaptic GluN-mediated evoked excitatory postsynaptic currents (eEPSCs) were elevated in CA1 pyramidal neurons. Moreover, GluN eEPSCs showed a decreased sensitivity to GluN2B selective antagonists and decreased Mg2+ sensitivity at negative holding potentials, indicating a higher proportion of GluN2A and GluN3A subunit function, respectively. These physiological findings were accompanied by a concurrent increase in GluN2A phosphorylation and GluN3A protein. These results suggest that altered GluN function and expression could potentially contribute to future epileptogenesis following neonatal seizures, and may represent potential therapeutic targets for the blockade of future epileptogenesis in the developing brain.
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Affiliation(s)
- Chengwen Zhou
- Department of Neurology, Division of Neuroscience, Boston Children's Hospital Boston, MA, USA ; Program in Neurobiology, Harvard Medical School Boston, MA, USA
| | - Hongyu Sun
- Department of Neurology, Division of Neuroscience, Boston Children's Hospital Boston, MA, USA ; Program in Neurobiology, Harvard Medical School Boston, MA, USA ; Department of Neurology, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA, USA
| | - Peter M Klein
- Department of Neurology, Division of Neuroscience, Boston Children's Hospital Boston, MA, USA
| | - Frances E Jensen
- Department of Neurology, Division of Neuroscience, Boston Children's Hospital Boston, MA, USA ; Program in Neurobiology, Harvard Medical School Boston, MA, USA ; Department of Neurology, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA, USA
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8
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Kang SK, Kadam SD. Neonatal Seizures: Impact on Neurodevelopmental Outcomes. Front Pediatr 2015; 3:101. [PMID: 26636052 PMCID: PMC4655485 DOI: 10.3389/fped.2015.00101] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 11/05/2015] [Indexed: 11/24/2022] Open
Abstract
Neonatal period is the most vulnerable time for the occurrence of seizures, and neonatal seizures often pose a clinical challenge both for their acute management and frequency of associated long-term co-morbidities. Etiologies of neonatal seizures are known to play a primary role in the anti-epileptic drug responsiveness and the long-term sequelae. Recent studies have suggested that burden of acute recurrent seizures in neonates may also impact chronic outcomes independent of the etiology. However, not many studies, either clinical or pre-clinical, have addressed the long-term outcomes of neonatal seizures in an etiology-specific manner. In this review, we briefly review the available clinical and pre-clinical research for long-term outcomes following neonatal seizures. As the most frequent cause of acquired neonatal seizures, we focus on the studies evaluating long-term effects of HIE-seizures with the goal to evaluate (1) what parameters evaluated during acute stages of neonatal seizures can reliably be used to predict long-term outcomes? and (2) what available clinical and pre-clinical data are available help determine importance of etiology vs. seizure burdens in long-term sequelae.
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Affiliation(s)
- Seok Kyu Kang
- Neuroscience Laboratory, Hugo Moser Research Institute at Kennedy Krieger , Baltimore, MD , USA
| | - Shilpa D Kadam
- Neuroscience Laboratory, Hugo Moser Research Institute at Kennedy Krieger , Baltimore, MD , USA ; Department of Neurology, Johns Hopkins University School of Medicine , Baltimore, MD , 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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10
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Lee SH, Kim BJ, Kim YB, Chung PW, Moon HS, Suh BC, Yoon WT, Jin DK, Park YS, Lee YT, Park KY. IL-1β induction and IL-6 suppression are associated with aggravated neuronal damage in a lipopolysaccharide-pretreated kainic acid-induced rat pup seizure model. Neuroimmunomodulation 2012; 19:319-25. [PMID: 22797174 DOI: 10.1159/000339579] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Accepted: 05/19/2012] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVES Reportedly, hippocampal neuronal degeneration by kainic acid (KA)-induced seizures in rats <14 days old was enhanced by lipopolysaccharide (LPS). This study was to test the hypothesis that cytokines such as interleukin (IL)-1β, IL-6 and tumor necrosis factor-α are associated with aggravated neuronal damage. MATERIALS AND METHODS Sixty male Sprague-Dawley, 14-day-old rats were used. Experiments were conducted in saline, LPS + saline, saline + KA and LPS + KA groups. Intraperitoneal LPS injections (0.04 mg/kg) were administered 3 h prior to KA injection (3 mg/kg). RESULTS The LPS + KA group showed a tendency toward shorter latency to seizure onset (p = 0.086) and significantly longer seizure duration (p < 0.05) compared with the KA group. Induction of the proconvulsant cytokine IL-1β in rat pup brains was significantly greater in the LPS + KA group compared to the KA group (38.8 ± 5.5 vs. 9.2 ± 1.0 pg/µg; p < 0.05); however, IL-6 levels were higher in the KA group than in the LPS + KA group (108.7 ± 6.8 vs. 60.9 ± 4.7 pg/µg; p < 0.05). The difference in tumor necrosis factor-α between the LPS + KA group and the KA group was insignificant (12.1 ± 0.6 vs. 10.9 ± 2.3 pg/µg; p = 0.64). CONCLUSIONS Our results showed an increase in the proconvulsant cytokine IL-1β and a decrease in a potentially neuroprotective cytokine, IL-6, in rat pups treated with LPS + KA. These results warrant further investigation into the possible role of IL-1β induction and IL-6 suppression in LPS-promoted neuronal damage.
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Affiliation(s)
- Sung-Hyun Lee
- Department of Neurology, College of Medicine, Chungbuk National University Cheongju, Chungbuk, Republic of Korea
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11
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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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Mikati MA, Daderian R, Zeinieh M, Leonard AS, Azzam D, Kurdi R. Potential neuroprotective effects of continuous topiramate therapy in the developing brain. Epilepsy Behav 2011; 20:597-601. [PMID: 21450530 DOI: 10.1016/j.yebeh.2010.12.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Revised: 11/18/2010] [Accepted: 12/07/2010] [Indexed: 01/27/2023]
Abstract
Because antiepileptic drug therapy is usually given chronically with resulting concerns about long-term neurotoxicity, and because short-term topiramate (TPM) therapy has been reported to be neuroprotective against the effects of acute hypoxia, we investigated the long-term effects of continuous TPM therapy during early stages of development. Four groups of rat pups were studied: two sham manipulated normoxia groups and two acute hypoxia groups (at postnatal day [P] 10 down to 4% O(2)), each injected intraperitoneally daily with either vehicle or TPM (30 mg/kg) from P0 to P21. TPM therapy prevented hypoxia-induced long-term (P81) memory impairment (Morris water maze) as well as aggressivity (handling test). The hypoxia group receiving TPM also showed a trend toward reduced CA1 hippocampal cell loss. The aforementioned TPM therapy had no long-term deleterious effects on memory, hyperactivity, or CA1 cell counts in the TPM normoxia group as compared with normal controls.
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Affiliation(s)
- Mohamad A Mikati
- Department of Pediatrics and Adolescent Medicine, Faculty of Medicine, American University of Beirut, Beirut, Lebanon.
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13
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Zeinieh MP, Talhouk RS, El-Sabban ME, Mikati MA. Differential expression of hippocampal connexins after acute hypoxia in the developing brain. Brain Dev 2010; 32:810-7. [PMID: 20034754 DOI: 10.1016/j.braindev.2009.11.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2009] [Revised: 09/30/2009] [Accepted: 11/05/2009] [Indexed: 01/28/2023]
Abstract
Acute hypoxia at postnatal day (P) 10 is an accepted model of human neonatal hypoxia which results, among other consequences, in increased hippocampal excitability. Hypoxic-ischemic injury, which mimics stroke, has been shown to result in changes in connexins (Cxs), however, changes in Cxs have not been studied in the P10 hypoxia model. The aim of this study was to investigate changes in the hippocampal expression of three different connexins at consecutive developmental stages after acute hypoxia at P10 (10min and 30min after reoxygenation, P11, P14, P17, P29, and P45) as compared to sham manipulated pups. After acute hypoxia at P10, Cx30 protein levels were increased at 30min after reoxygenation, at P11 and at P14, and then returned to control levels. Cx36 protein levels transiently decreased at P11 after acute hypoxia then returned to control levels. Cx43 protein levels did not change at any of the time points. Although changes in mRNA expression were observed during development for Cx30 only, acute hypoxia did not result in changes in mRNA expression of all these Cxs when compared to age matched controls suggesting that acute hypoxia induced posttranslational changes in protein expression.
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Affiliation(s)
- Michele P Zeinieh
- Department of Biology, American University of Beirut, Beirut, Lebanon
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Greggio S, Rosa RM, Dolganov A, de Oliveira IM, Menegat FD, Henriques JA, DaCosta JC. NAP prevents hippocampal oxidative damage in neonatal rats subjected to hypoxia-induced seizures. Neurobiol Dis 2009; 36:435-44. [DOI: 10.1016/j.nbd.2009.08.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Revised: 08/08/2009] [Accepted: 08/17/2009] [Indexed: 11/29/2022] Open
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15
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Yager JY, Armstrong EA, Black AM. Treatment of the term newborn with brain injury: simplicity as the mother of invention. Pediatr Neurol 2009; 40:237-43. [PMID: 19218037 DOI: 10.1016/j.pediatrneurol.2008.12.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Accepted: 11/03/2008] [Indexed: 11/28/2022]
Abstract
Neonatal brain injury remains a common cause of developmental disability, despite tremendously enhanced obstetrical and neonatal care. The timing of brain injury occurs throughout gestation, labor, and delivery, providing an evolving form of brain injury and a moving target for therapeutic intervention. Nonetheless, markedly improved methods are available to identify those infants injured at birth, via clinical presentation with neonatal encephalopathy and neuroimaging techniques. Postischemic hypothermia has been shown to be of tremendous clinical promise in several completed and ongoing trials. As part of this approach to the treatment of the newborn, other parameters of physiologic homeostasis can and should be attended to, with strong animal and clinical evidence that their correction will have dramatic influence on the outcome of the newborn infant. This review addresses aspects of newborn care to which we can direct our attention currently, and which should result in a safe and efficacious improvement in the prognosis of the newborn with neonatal encephalopathy.
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Affiliation(s)
- Jerome Y Yager
- Department of Pediatrics, Stollery Children's Hospital, University of Alberta, Edmonton, Alberta, Canada.
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Kobayashi M, Watanabe M, Nakamura J. [Pharmacology and clinical results of topiramate (TOPINA Tablets), a new antiepileptic drug]. Nihon Yakurigaku Zasshi 2008; 132:45-52. [PMID: 18622103 DOI: 10.1254/fpj.132.45] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
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Pamenter ME, Shin DSH, Buck LT. AMPA receptors undergo channel arrest in the anoxic turtle cortex. Am J Physiol Regul Integr Comp Physiol 2007; 294:R606-13. [PMID: 18056983 DOI: 10.1152/ajpregu.00433.2007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Without oxygen, all mammals suffer neuronal injury and excitotoxic cell death mediated by overactivation of the glutamatergic N-methyl-D-aspartate receptor (NMDAR). The western painted turtle can survive anoxia for months, and downregulation of NMDAR activity is thought to be neuroprotective during anoxia. NMDAR activity is related to the activity of another glutamate receptor, the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (AMPAR). AMPAR blockade is neuroprotective against anoxic insult in mammals, but the role of AMPARs in the turtle's anoxia tolerance has not been investigated. To determine whether AMPAR activity changes during hypoxia or anoxia in the turtle cortex, whole cell AMPAR currents, AMPAR-mediated excitatory postsynaptic potentials (EPSPs), and excitatory postsynaptic currents (EPSCs) were measured. The effect of AMPAR blockade on normoxic and anoxic NMDAR currents was also examined. During 60 min of normoxia, evoked peak AMPAR currents and the frequencies and amplitudes of EPSPs and EPSCs did not change. During anoxic perfusion, evoked AMPAR peak currents decreased 59.2 +/- 5.5 and 60.2 +/- 3.5% at 20 and 40 min, respectively. EPSP frequency (EPSP(f)) and amplitude decreased 28.7 +/- 6.4% and 13.2 +/- 1.7%, respectively, and EPSC(f) and amplitude decreased 50.7 +/- 5.1% and 51.3 +/- 4.7%, respectively. In contrast, hypoxic (Po(2) = 5%) AMPAR peak currents were potentiated 56.6 +/- 20.5 and 54.6 +/- 15.8% at 20 and 40 min, respectively. All changes were reversed by reoxygenation. AMPAR currents and EPSPs were abolished by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). In neurons pretreated with CNQX, anoxic NMDAR currents were reversibly depressed by 49.8 +/- 7.9%. These data suggest that AMPARs may undergo channel arrest in the anoxic turtle cortex.
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Affiliation(s)
- Matthew Edward Pamenter
- University of Toronto, Department of Cellular and Systems Biology, 25 Harbord Street, Toronto, Ontario, Canada
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18
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Williams PA, Dudek FE. A chronic histopathological and electrophysiological analysis of a rodent hypoxic-ischemic brain injury model and its use as a model of epilepsy. Neuroscience 2007; 149:943-61. [PMID: 17935893 PMCID: PMC2897748 DOI: 10.1016/j.neuroscience.2007.07.067] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2007] [Revised: 07/24/2007] [Accepted: 08/15/2007] [Indexed: 11/24/2022]
Abstract
Ischemic brain injury is one of the leading causes of epilepsy in the elderly, and there are currently no adult rodent models of global ischemia, unilateral hemispheric ischemia, or focal ischemia that report the occurrence of spontaneous motor seizures following ischemic brain injury. The rodent hypoxic-ischemic (H-I) model of brain injury in adult rats is a model of unilateral hemispheric ischemic injury. Recent studies have shown that an H-I injury in perinatal rats causes hippocampal mossy fiber sprouting and epilepsy. These experiments aimed to test the hypothesis that a unilateral H-I injury leading to severe neuronal loss in young-adult rats also causes mossy fiber sprouting and spontaneous motor seizures many months after the injury, and that the mossy fiber sprouting induced by the H-I injury forms new functional recurrent excitatory synapses. The right common carotid artery of 30-day old rats was permanently ligated, and the rats were placed into a chamber with 8% oxygen for 30 min. A quantitative stereologic analysis revealed that the ipsilateral hippocampus had significant hilar and CA1 pyramidal neuronal loss compared with the contralateral and sham-control hippocampi. The septal region from the ipsilateral and contralateral hippocampus had small but significantly increased amounts of Timm staining in the inner molecular layer compared with the sham-control hippocampi. Three of 20 lesioned animals (15%) were observed to have at least one spontaneous motor seizure 6-12 months after treatment. Approximately 50% of the ipsilateral and contralateral hippocampal slices displayed abnormal electrophysiological responses in the dentate gyrus, manifest as all-or-none bursts to hilar stimulation. This study suggests that H-I injury is associated with synaptic reorganization in the lesioned region of the hippocampus, and that new recurrent excitatory circuits can predispose the hippocampus to abnormal electrophysiological activity and spontaneous motor seizures.
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Chan CY, Lam WP, Wai MSM, Wang M, Foster EL, Yew DTW. Perinatal hypoxia induces anterior chamber changes in the eyes of offspring fish. J Reprod Dev 2007; 53:1159-67. [PMID: 17693701 DOI: 10.1262/jrd.19018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Hypoxia is a consistent challenge for aquatic animals. It is a pressing environmental problem; hypoxia can cause cranial edema and ovarium dysfunction in fish. Although several studies have reported the effect of hypoxic insult to the visual system, the hypoxic effect on perinatal animals and in particular their offspring has yet to be elucidated. In this study, activated caspase-3 activity was investigated using immunohistochemistry in order to examine the perinatal hypoxic damage in offspring fish. Offspring were divided into groups based on different time points of sacrifice. This allowed assessment of ocular development for different age groups. The results indicated that perinatal hypoxia induced ocular developmental defects in the offspring. The defects took the form of trabecular cell death and fibre degeneration, corneal thinning and lens fibre derangement. A concomitant change in intraocular pressure was recorded by tonometer in the experimental animals compared with the controls. Further investigation should be initiated to develop strategies to prevent developmental disability due to perinatal hypoxia and to increase survivability of the offspring.
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Affiliation(s)
- Chu Yan Chan
- Department of Anatomy, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, PR China
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20
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Sankar R, Auvin S, Mazarati A, Shin D. Inflammation contributes to seizure-induced hippocampal injury in the neonatal rat brain. Acta Neurol Scand 2007; 115:16-20. [PMID: 17362271 DOI: 10.1111/j.1600-0404.2007.00804.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE The extent of neuronal injury in the hippocampus produced by experimental status epilepticus (SE) is age dependent and is not readily demonstrable in many models of neonatal seizures. Neonatal seizures often occur in clinical settings that include an inflammatory component. We examined the potential contributory role of pre-existing inflammation as an important variable in mediating neuronal injury. MATERIALS AND METHODS Postnatal day 7 (P7) and P14 rat pups were injected with lipopolysaccharide (LPS), 2 h prior to SE induced by lithium-pilocarpine (LiPC). Neuronal injury was assessed by well-described histologic methods. RESULTS While LPS by itself did not produce any discernible cell injury at either age, this treatment exacerbated hippocampal damage induced by LiPC-SE. The effect was highly selective for the CA1 subfield. CONCLUSIONS Inflammation can contribute substantially to the vulnerability of immature hippocampus to seizure-induced neuronal injury. The combined effects of inflammation and prolonged seizures in early life may impact long-term outcomes of neonatal seizures.
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Affiliation(s)
- R Sankar
- Division of Neurology, Department of Pediatrics, David Geffen School of Medicine at UCLA and Mattel Children's Hospital at UCLA, Los Angeles, CA 90095, USA.
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21
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Valdez SR, Patterson SI, Ezquer ME, Torrecilla M, Lama MC, Seltzer AM. Acute sublethal global hypoxia induces transient increase of GAP-43 immunoreactivity in the striatum of neonatal rats. Synapse 2007; 61:124-37. [PMID: 17146769 DOI: 10.1002/syn.20353] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We assessed immunoreactivity (IR) in the cerebral cortex (CC), hippocampus (Hipp), and striatum (ST) of a growth-associated protein, GAP-43, and of proteins of the synaptic vesicle fusion complex: VAMP-2, Syntaxin-1, and SNAP-25 (SNARE proteins) throughout postnatal development of rats after submitting the animals to acute global postnatal hypoxia (6.5% O(2), 70 min) at postnatal day 4 (PND4). In the CC only the IR of the SNARE protein SNAP-25 increased significantly with age. The hypoxic animals showed the same pattern of IR for SNAP-25, although with lower levels at PND11, and also a significant increase of VAMP-2. SNAP-25 (control): PND11 P < 0.001 vs. PND18, 25, and 40, SNAP-25 (hypoxic): P < 0.001 vs. PND18, 25, and 40; VAMP-2 (hypoxic): P < 0.05 PND11 vs. PND18, and P < 0.01 vs. PND25 and PND40; one-way ANOVA and Bonferroni post-test. In the Hipp, SNAP-25 and syntaxin-1 increased significantly with age, reaching a plateau at PND25 through PND40 in control animals (one-way ANOVA: syntaxin-1: P = 0.043; Bonferroni: NS; SNAP-25: P = 0.013; Bonferroni: P < 0.01 PND11 vs. PND40). Hypoxic rats showed higher levels of significance in the one-way ANOVA than controls (syntaxin-1: P = 0.009; Bonferroni: P < 0.05 PND11 vs. PND25 and P < 0.001 PND11 vs. PND40). In the ST, GAP-43 differed significantly among hypoxic and control animals and the two-way ANOVA revealed significant differences with age (F = 3.23; P = 0.037) and treatment (F = 4.84; P = 0.036). VAMP-2 expression also reached statistical significance when comparing control and treated animals (F = 6.25, P = 0.018) without changes regarding to age. Elevated plus maze test performed at PND40 indicated a lower level of anxiety in the hypoxic animals. At adulthood (12 weeks) learning, memory and locomotor abilities were identical in both groups of animals. With these results, we demonstrate that proteins of the presynaptic structures of the ST are sensitive to acute disruption of homeostatic conditions, such as a temporary decrease of the O(2) concentration. Modifications in the activity of these proteins could contribute to the long term altered responses to stress due to acute hypoxic insult in the neonatal period.
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Affiliation(s)
- Susana R Valdez
- IMBECU-CRICYT, Centro Regional de Investigaciones Científicas y Tecnológicas, Mendoza, Argentina
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Mikati MA, Zeinieh MP, Kurdi RM, Harb SA, El Hokayem JA, Daderian RH, Shamseddine A, Obeid M, Bitar FF, El Sabban M. Long-term effects of acute and of chronic hypoxia on behavior and on hippocampal histology in the developing brain. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2005; 157:98-102. [PMID: 15939090 DOI: 10.1016/j.devbrainres.2005.03.007] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2004] [Revised: 03/09/2005] [Accepted: 03/11/2005] [Indexed: 11/21/2022]
Abstract
Ten-day-old rat pups (P10) subjected to acute hypoxia (down to 4% O2) had as adults increased aggression (handling test), memory impairment (water maze test), and decreased CA1 cell counts. Pups subjected to chronic hypoxia (10% O2 from P0 to P21) had increased aggression, hyperactivity (open-field test), and decreased CA1 cell counts. Chronic hypoxia with superimposed acute hypoxia resulted in consequences that were not different from those of chronic hypoxia.
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Affiliation(s)
- Mohamad A Mikati
- Adult and Pediatric Epilepsy Program, Department of Pediatrics, PO Box 11-0236/B52 Riad el Solh, American University of Beirut, Beirut 1107-2020, Lebanon.
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23
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Zhao Q, Hu Y, Holmes GL. Effect of topiramate on cognitive function and activity level following neonatal seizures. Epilepsy Behav 2005; 6:529-36. [PMID: 15878305 DOI: 10.1016/j.yebeh.2005.03.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2005] [Revised: 02/28/2005] [Accepted: 03/01/2005] [Indexed: 11/29/2022]
Abstract
Topiramate, an antiepileptic drug with a number of mechanisms of action including blockade of AMPA/KA receptor subtypes, was assessed as a neuroprotective agent following seizures. We administered topiramate or saline chronically during and following a series of 25 neonatal seizures. After completion of the topiramate treatment, animals were tested in the water maze for spatial learning and the open field for activity level. Brains were then examined for cell loss and sprouting of mossy fibers. Rats treated with topiramate performed significantly better in the water maze than rats treated with saline. Topiramate treatment also reduced the amount of seizure-induced sprouting in the supragranular region. There were no differences between topiramate- and saline-treated rats in activity level in the open field, swimming speed, or weight gain. These findings show that long-term treatment with topiramate after neonatal seizures changes the long-term consequences of seizures and improves cognitive function.
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Affiliation(s)
- Qian Zhao
- Section of Neurology, Neuroscience Center at Dartmouth, Dartmouth Medical School, Hanover, NH, USA
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Williams PA, Dou P, Dudek FE. Epilepsy and synaptic reorganization in a perinatal rat model of hypoxia-ischemia. Epilepsia 2004; 45:1210-8. [PMID: 15461675 DOI: 10.1111/j.0013-9580.2004.60403.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE One of the potential consequences of perinatal hypoxia-ischemia (H-I) is the development of epilepsy, and synaptic reorganization in the hippocampus has been associated with epilepsy after an injury. We tested the hypothesis that perinatal H-I will induce spontaneous motor seizures, hippocampal lesions, and synaptic reorganization in the dentate gyrus. METHODS The right common carotid artery of 7-day-old rats was permanently ligated, and the rats were placed for 120 min into a chamber filled with 8% oxygen (37 degrees C). Animals were directly observed for chronic motor seizures for 7 to 24 months after the H-I insult. RESULTS Nearly half of the rats (i.e., eight of 20) were seen to have spontaneous motor seizures after the H-I injury. The ipsilateral hippocampi from both the rats with seizures and the rats not seen to have seizures had hippocampal lesions and increased amounts of Timm stain in the inner molecular layer (IML) compared with controls. The contralateral hippocampi from the rats with seizures, but not the hippocampi from the rats not seen to have seizures, had significantly increased amounts of Timm stain in the IML. CONCLUSIONS These results suggest that perinatal H-I can induce epilepsy, ipsilateral hippocampal lesions, and mossy fiber sprouting in the lesioned and contralateral hippocampus.
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Affiliation(s)
- Philip A Williams
- Department of Biomedical Sciences, Section of Anatomy and Neurobiology, Colorado State University, Fort Collins, Colorado 80523, USA
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25
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Velísek L, Moshé SL. Temporal Lobe Epileptogenesis and Epilepsy in the Developing Brain: Bridging the Gap Between the Laboratory and the Clinic. Progression, But in What Direction? Epilepsia 2003; 44 Suppl 12:51-9. [PMID: 14641561 DOI: 10.1111/j.0013-9580.2003.12008.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The origins of human mesial temporal lobe epilepsy and hippocampal sclerosis are still not well understood. Hippocampal sclerosis and temporal lobe epileptogenesis involve a series of pathologies including hippocampal neuronal loss and gliosis, axonal reorganization, and maybe hippocampal neoneurogenesis. However, the causality of these events is unclear as well as their relation to the factors that may precipitate epileptogenesis. Significant differences between temporal lobe epileptogenesis in the adult and immature brain may require differential approaches. Hereditary factors also may participate in some cases of hippocampal sclerosis. The key point is to identify the significance of these age-dependent changes and to design preventive treatments. Novel strategies for the prevention and treatment of mesial temporal lobe epilepsy and hippocampal sclerosis may include rational use of neuroprotective agents, hormonotherapy, immunizations, and immunotherapy.
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Affiliation(s)
- L Velísek
- Department of Neurology K314, and Montefiore/Einstein Epilepsy Management Center, Albert Einstein College of Medicine, 1410 Pelham Parkway South, Bronx, NY 10461, U.S.A.
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26
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Rubaj A, Zgodziński W, Sieklucka-Dziuba M. The epileptogenic effect of seizures induced by hypoxia: the role of NMDA and AMPA/KA antagonists. Pharmacol Biochem Behav 2003; 74:303-11. [PMID: 12479949 DOI: 10.1016/s0091-3057(02)00998-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Hypoxia of the brain may alter further seizure susceptibility in a different way. In this study, we tried to answer the question how episode of convulsion induced by hypoxia (HS) changes further seizure susceptibility, and how N-methyl-D-aspartic acid (NMDA) and AMPA/KA receptor antagonists influence this process. Adult Albino Swiss mice exposed to hypoxia (5% O(2)) developed clonic/tonic convulsions after about 340 s. Mice which underwent 10 s but not 5 s seizures episode subsequently exhibited significantly increased seizure susceptibility to low doses (equal ED(16)) of bicuculline (BCC) and NMDA during a 3-week observation period. No morphological signs of brain tissue damage were seen in light microscope on the third day after a hypoxia-induced seizure (HS). Learning abilities assessed in passive avoidance test as well as spontaneous alternation were not disturbed after an HS episode. Pretreatment with AMPA/KA receptor antagonist NBQX effectively prolonged latency to HS and given immediately after seizure episode also attenuated subsequent convulsive susceptibility rise, however, NMDA receptor antagonist, MK-801, appeared to be ineffective. These results suggest that a seizure episode induced by hypoxia, depending on its duration, may play an epileptogenic role. The AMPA/KA receptor antagonist prolongs the latency to HS, and given after this episode, prevents the long-term epileptogenic effect.
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Affiliation(s)
- Andrzej Rubaj
- Department of Cardiology, Medical University of Lublin, Jaczewskiego 8, 20-090 Lublin, Poland.
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27
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Godukhin O, Savin A, Kalemenev S, Levin S. Neuronal hyperexcitability induced by repeated brief episodes of hypoxia in rat hippocampal slices: involvement of ionotropic glutamate receptors and L-type Ca(2+) channels. Neuropharmacology 2002; 42:459-66. [PMID: 11955517 DOI: 10.1016/s0028-3908(02)00005-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Repeated exposures of rat hippocampal slices to short episodes of hypoxia induce a sustained decrease in the threshold of the development of stimulus-evoked epileptiform discharges in CA1 pyramidal neurons. We have previously demonstrated that the K(+)(o)-induced hyperexcitability required functional L-type voltage-dependent Ca(2+) channels and NMDA-receptors, but was independent of AMPA/kainate-receptor activation. As hypoxia/ischaemia can lead to increased K(+)(o), the epileptiform activity observed after exposure to these challenges could also result from high K(+)(o). The purpose of this study was: (i) to determine whether ionotropic glutamate receptors and L-type Ca(2+) channels are involved in the development of epileptiform activity induced by repeated exposures of hippocampal slices to hypoxia; and (ii) to compare the properties of hypoxia- and high K(+)(o)-induced hyperexcitability. Population spike of presynaptic fibres with field excitatory postsynaptic potential from the stratum radiatum, and population spike of CA1 pyramidal neurons from the stratum pyramidale, were recorded simultaneously in the CA1 area of rat hippocampal slices in response to electrical stimulation of the Schaffer collateral/commissural fibres. Repeated, brief hypoxic episodes induced a sustained decrease in the threshold for development of evoked epileptiform discharges that was associated with long-term potentiation of the CA3-CA1 synapses, but without EPSP-spike potentiation (i.e. in contrast to high K(+)(o)-induced hyperexcitability). The selective antagonist of NMDA receptors, D-APV (25 microM), and the selective blocker of L-type Ca(2+) channels, nifedipine (10 microM) depressed the development of hypoxia-induced hyperexcitability. However, in contrast to high K(+)(o)-induced hyperexcitability, hypoxia-induced hyperexcitability was also blocked by the AMPA/kainite-receptor antagonist, CNQX (5 microM). The present findings confirm that repeated, brief episodes of hypoxia, like exposure to high extracellular K(+), can induce a pro-epileptic state in the CA1 neuronal network, but that the mechanisms leading to hyperexcitability are different for the two stimuli.
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Affiliation(s)
- O Godukhin
- Institute of Theoretical and Experimental Biophysics of the Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
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28
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Abstract
Animal models are crucial for understanding human pathophysiological processes and for understanding how connections are injured, lost, or even regenerated and/or repaired. When animal models are used in conjunction with theoretical computational models, an ideal combination is achieved that potentially yields insight and encourages the formation of new theories concerning connectionism, cognitive functioning, and synaptic mechanisms. Mechanisms regulating glutamate receptor activation and intracellular calcium levels are important for normal synaptic transmission. These mechanisms (and others) are also critical during and after brain injury when the potential exists for these mechanisms to function pathologically. Interestingly enough, the regulation of glutamate receptor activation and intracellular calcium levels is also involved in normal processes of neuronal and synaptic plasticity. In addition, studies have shown that neurotrophins and cytokines, which are released after brain injury, can be neuroprotective and may also be important in synaptic plasticity. Furthermore, synaptic plasticity is a phenomenon thought by many to be necessary for memory encoding. If this is the case, then research described in this review has significant scientific merit concerning plasticity and memory and clinical benefit for understanding pathophysiologic processes associated with brain injury and memory impairment. This paper reviews the application of experimental animal models of brain injury for simulating conditions of stroke, trauma, and epilepsy (and/or seizure generation) and the associated cellular mechanisms of brain injury. The paper also briefly addresses the advantage of using computational models in combination with experimental models for hypothesis building and for aiding in the interpretation of empirical data. Finally, it reviews studies concerning brain injury and synaptic plasticity.
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Affiliation(s)
- B C Albensi
- The Cleveland Clinic Foundation, Department of Neurological Surgery, 9500 Euclid Ave., Cleveland, OH 44195, USA
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Abstract
A diversity of animal models are available for the study of epilepsy and these models have a proven history in advancing our understanding of basic mechanisms underlying epileptogenesis and have been instrumental in the screening of novel antiepileptic drugs. This review addresses the criteria that should be met in a valid animal model and provides an overview of current animal models that are relevant to human conditions. In addition, models not specific for any one human condition but rather exhibiting partial or generalized seizures are discussed. While most human disorders are without any animal model, those models that are clinically relevant have strengths and weaknesses. Finally, although few relevant, well-characterized animal models have been added to the list over recent years, major advancements in molecular genetics are contributing to the discovery of novel pathways involved in epileptogenesis.
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30
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Engel J. Critical evaluation of animal models for localization-related epilepsies. ITALIAN JOURNAL OF NEUROLOGICAL SCIENCES 1995; 16:9-16. [PMID: 7642358 DOI: 10.1007/bf02229069] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
There are many forms of human partial seizures and many human localization-related epilepsies. Idiopathic epilepsies undoubtedly have pathophysiologic substrates different from those of symptomatic epilepsies, and there is evidence that some forms of limbic epilepsy involve different epileptogenic mechanisms than neocortical epilepsies. Although these mechanisms are best studied and understood by direct investigations of patients, this is often impractical and experimental animal models are also necessary. The use of experimental animals requires that the relevance of each model to a human condition be determined. Human epilepsies are comprised of multiple component parts which can be modeled independently. For instance, acute animal models provide opportunities to study epileptic seizures, but chronic models are necessary for investigation of processes relevant to epileptic conditions, such as epileptogenesis, transition from interictal to ictal state, and long-term consequences of epilepsy. Interactions between localized epileptic activity and cerebral maturation can also be studied in the animal laboratory. Experimental animal models of human partial seizures and localization-related epilepsies can be used to further investigations on basic mechanisms that cannot be pursued in patients, and to develop hypotheses concerning the fundamental neuronal processes underlying epilepsy and epilepsy-related phenomena that subsequently can be validated in patients. In addition, it would be of great clinical utility to develop animal models of partial seizures or localization-related epilepsy that could be used cost-effectively to screen potential anti-epileptic drugs.
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Affiliation(s)
- J Engel
- Department of Neurology, UCLA School of Medicine, CA, USA
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