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Liu R, Xing Y, Zhang H, Wang J, Lai H, Cheng L, Li D, Yu T, Yan X, Xu C, Piao Y, Zeng L, Loh HH, Zhang G, Yang X. Imbalance between the function of Na+-K+-2Cl and K+-Cl impairs Cl– homeostasis in human focal cortical dysplasia. Front Mol Neurosci 2022; 15:954167. [PMID: 36324524 PMCID: PMC9621392 DOI: 10.3389/fnmol.2022.954167] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 09/27/2022] [Indexed: 11/29/2022] Open
Abstract
Objective Altered expression patterns of Na+-K+-2Cl– (NKCC1) and K+-Cl– (KCC2) co-transporters have been implicated in the pathogenesis of epilepsy. Here, we assessed the effects of imbalanced NKCC1 and KCC2 on γ-aminobutyric acidergic (GABAergic) neurotransmission in certain brain regions involved in human focal cortical dysplasia (FCD). Materials and methods We sought to map a micro-macro neuronal network to better understand the epileptogenesis mechanism. In patients with FCD, we resected cortical tissue from the seizure the onset zone (SOZ) and the non-seizure onset zone (non-SOZ) inside the epileptogenic zone (EZ). Additionally, we resected non-epileptic neocortical tissue from the patients with mesial temporal lobe epilepsy (MTLE) as control. All of tissues were analyzed using perforated patch recordings. NKCC1 and KCC2 co-transporters expression and distribution were analyzed by immunohistochemistry and western blotting. Results Results revealed that depolarized GABAergic signals were observed in pyramidal neurons in the SOZ and non-SOZ groups compared with the control group. The total number of pyramidal neurons showing GABAergic spontaneous postsynaptic currents was 11/14, 7/17, and 0/12 in the SOZ, non-SOZ, and control groups, respectively. The depolarizing GABAergic response was significantly dampened by the specific NKCC1 inhibitor bumetanide (BUM). Patients with FCD exhibited higher expression and internalized distribution of KCC2, particularly in the SOZ group. Conclusion Our results provide evidence of a potential neurocircuit underpinning SOZ epileptogenesis and non-SOZ seizure susceptibility. Imbalanced function of NKCC1 and KCC2 may affect chloride ion homeostasis in neurons and alter GABAergic inhibitory action, thereby contributing to epileptogenesis in FCDs. Maintaining chloride ion homeostasis in the neurons may represent a new avenue for the development of novel anti-seizure medications (ASMs).
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Affiliation(s)
- Ru Liu
- Guangzhou Laboratory, Guangzhou, China
- Beijing Tiantan Hospital, Capital Medical University, Beijing, China
- Beijing Institute of Brain Disorders, Capital Medical University, Beijing, China
- Neuroelectrophysiological Laboratory, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Yue Xing
- Guangzhou Laboratory, Guangzhou, China
| | | | - Junling Wang
- Guangzhou Laboratory, Guangzhou, China
- Beijing Tiantan Hospital, Capital Medical University, Beijing, China
- Beijing Institute of Brain Disorders, Capital Medical University, Beijing, China
- Neuroelectrophysiological Laboratory, Xuanwu Hospital, Capital Medical University, Beijing, China
| | | | - Lipeng Cheng
- Guangzhou Laboratory, Guangzhou, China
- Beijing Institute of Brain Disorders, Capital Medical University, Beijing, China
- Neuroelectrophysiological Laboratory, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Donghong Li
- Department of Neurology, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Tao Yu
- Department of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Xiaoming Yan
- Department of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Cuiping Xu
- Department of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Yueshan Piao
- Department of Pathology, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Linghui Zeng
- Department of Pharmacology, Zhejiang University City College, Hangzhou, China
| | | | - Guojun Zhang
- Department of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
- *Correspondence: Guojun Zhang,
| | - Xiaofeng Yang
- Guangzhou Laboratory, Guangzhou, China
- Neuroelectrophysiological Laboratory, Xuanwu Hospital, Capital Medical University, Beijing, China
- Xiaofeng Yang,
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Setkowicz Z, Gzielo K, Kielbinski M, Janeczko K. Structural changes in the neocortex as correlates of variations in EEG spectra and seizure susceptibility in rat brains with different degrees of dysplasia. J Comp Neurol 2021; 530:1379-1398. [PMID: 34861050 PMCID: PMC9305260 DOI: 10.1002/cne.25282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 10/26/2021] [Accepted: 11/23/2021] [Indexed: 11/13/2022]
Abstract
Disturbances of the early stages of neurogenesis lead to irreversible changes in the structure of the mature brain and its functional impairment, including increased excitability, which may be the basis for drug‐resistant epilepsy. The range of possible clinical symptoms is as wide as the different stages of disturbed neurogenesis may be. In this study, we used a quadruple model of brain dysplasia by comparing structural and functional disorders in animals whose neurogenesis was disturbed with a single dose of 1 Gy of gamma rays at one of the four stages of neurogenesis, that is, on days 13, 15, 17, or 19 of prenatal development. When reached adulthood, the prenatally irradiated rats received EEG teletransmitter implantation. Thereafter, pilocarpine was administered and significant differences in susceptibility to seizure behavioral symptoms were detected depending on the degree of brain dysplasia. Before, during, and after the seizures significant correlations were found between the density of parvalbumin‐immunopositive neurons located in the cerebral cortex and the intensity of behavioral seizure symptoms or increases in the power of particular EEG bands. Neurons expressing calretinin or NPY showed also dysplasia‐related increases without, however, correlations with parameters of seizure intensity. The results point to significant roles of parvalbumin‐expressing interneurons, and also to expression of NPY—an endogenous anticonvulsant and neuroprotectant reducing susceptibility to seizures and supporting neuronal survival.
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Affiliation(s)
- Zuzanna Setkowicz
- Laboratory of Experimental Neuropathology, Institute of Zoology and Biomedical Research, Faculty of Biology, Jagiellonian University, Kraków, Poland
| | - Kinga Gzielo
- Laboratory of Experimental Neuropathology, Institute of Zoology and Biomedical Research, Faculty of Biology, Jagiellonian University, Kraków, Poland
| | - Michal Kielbinski
- Laboratory of Experimental Neuropathology, Institute of Zoology and Biomedical Research, Faculty of Biology, Jagiellonian University, Kraków, Poland
| | - Krzysztof Janeczko
- Laboratory of Experimental Neuropathology, Institute of Zoology and Biomedical Research, Faculty of Biology, Jagiellonian University, Kraków, Poland
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Ardalan M, Svedin P, Baburamani AA, Supramaniam VG, Ek J, Hagberg H, Mallard C. Dysmaturation of Somatostatin Interneurons Following Umbilical Cord Occlusion in Preterm Fetal Sheep. Front Physiol 2019; 10:563. [PMID: 31178744 PMCID: PMC6538799 DOI: 10.3389/fphys.2019.00563] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 04/24/2019] [Indexed: 12/20/2022] Open
Abstract
INTRODUCTION Cerebral white matter injury is the most common neuropathology observed in preterm infants. However, there is increasing evidence that gray matter development also contributes to neurodevelopmental abnormalities. Fetal cerebral ischemia can lead to both neuronal and non-neuronal structural-functional abnormalities, but less is known about the specific effects on interneurons. OBJECTIVE In this study we used a well-established animal model of fetal asphyxia in preterm fetal sheep to study neuropathological outcome. We used comprehensive stereological methods to investigate the total number of oligodendrocytes, neurons and somatostatin (STT) positive interneurons as well as 3D morphological analysis of STT cells 14 days following umbilical cord occlusion (UCO) in fetal sheep. MATERIALS AND METHODS Induction of asphyxia was performed by 25 min of complete UCO in five preterm fetal sheep (98-100 days gestational age). Seven, non-occluded twins served as controls. Quantification of the number of neurons (NeuN), STT interneurons and oligodendrocytes (Olig2, CNPase) was performed on fetal brain regions by applying optical fractionator method. A 3D morphological analysis of STT interneurons was performed using IMARIS software. RESULTS The number of Olig2, NeuN, and STT positive cells were reduced in IGWM, caudate and putamen in UCO animals compared to controls. There were also fewer STT interneurons in the ventral part of the hippocampus, the subiculum and the entorhinal cortex in UCO group, while other parts of cortex were virtually unaffected (p > 0.05). Morphologically, STT positive interneurons showed a markedly immature structure, with shorter dendritic length and fewer dendritic branches in cortex, caudate, putamen, and subiculum in the UCO group compared with control group (p < 0.05). CONCLUSION The significant reduction in the total number of neurons and oligodendrocytes in several brain regions confirm previous studies showing susceptibility of both neuronal and non-neuronal cells following fetal asphyxia. However, in the cerebral cortex significant dysmaturation of STT positive neurons occurred in the absence of cell loss. This suggests an abnormal maturation pattern of GABAergic interneurons in the cerebral cortex, which might contribute to neurodevelopmental impairment in preterm infants and could implicate a novel target for neuroprotective therapies.
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Affiliation(s)
- Maryam Ardalan
- Centre for Perinatal Medicine and Health, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Pernilla Svedin
- Centre for Perinatal Medicine and Health, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Ana A. Baburamani
- Centre for the Developing Brain, Department of Perinatal Imaging and Health, School of Biomedical Engineering and Imaging Sciences, King’s College London, London, United Kingdom
| | - Veena G. Supramaniam
- Centre for the Developing Brain, Department of Perinatal Imaging and Health, School of Biomedical Engineering and Imaging Sciences, King’s College London, London, United Kingdom
| | - Joakim Ek
- Centre for Perinatal Medicine and Health, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Henrik Hagberg
- Centre for the Developing Brain, Department of Perinatal Imaging and Health, School of Biomedical Engineering and Imaging Sciences, King’s College London, London, United Kingdom
- Centre for Perinatal Medicine and Health, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Carina Mallard
- Centre for Perinatal Medicine and Health, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
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Abstract
Focal cortical dysplasia is a common cause of medication resistant epilepsy. A better understanding of its presentation, pathophysiology and consequences have helped us improved its treatment and outcome. This paper reviews the most recent classification, pathophysiology and imaging findings in clinical research as well as the knowledge gained from studying genetic and lesional animal models of focal cortical dysplasia. This review of this recently gained knowledge will most likely help develop new research models and new therapeutic targets for patients with epilepsy associated with focal cortical dysplasia.
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Kugelman T, Zuloaga DG, Weber S, Raber J. Post-training gamma irradiation-enhanced contextual fear memory associated with reduced neuronal activation of the infralimbic cortex. Behav Brain Res 2015; 298:1-11. [PMID: 26522840 DOI: 10.1016/j.bbr.2015.10.050] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 10/21/2015] [Accepted: 10/25/2015] [Indexed: 01/07/2023]
Abstract
The brain might be exposed to irradiation under a variety of situations, including clinical treatments, nuclear accidents, dirty bomb scenarios, and military and space missions. Correctly recalling tasks learned prior to irradiation is important but little is known about post-learning effects of irradiation. It is not clear whether exposure to X-ray irradiation during memory consolidation, a few hours following training, is associated with altered contextual fear conditioning 24h after irradiation and which brain region(s) might be involved in these effects. Brain immunoreactivity patterns of the immediately early gene c-Fos, a marker of cellular activity was used to determine which brain areas might be altered in post-training irradiation memory retention tasks. In this study, we show that post-training gamma irradiation exposure (1 Gy) enhanced contextual fear memory 24h later and is associated with reduced cellular activation in the infralimbic cortex. Reduced GABA-ergic neurotransmission in parvalbumin-positive cells in the infralimbic cortex might play a role in this post-training radiation-enhanced contextual fear memory.
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Affiliation(s)
- Tara Kugelman
- Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, OR 97239, USA
| | - Damian G Zuloaga
- Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, OR 97239, USA
| | - Sydney Weber
- Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, OR 97239, USA
| | - Jacob Raber
- Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, OR 97239, USA; Oregon Health and Science University, Portland, OR 97239, USA; Division of Neuroscience, ONPRC, Oregon Health and Science University, Portland, OR 97239, USA.
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Wong M, Roper SN. Genetic animal models of malformations of cortical development and epilepsy. J Neurosci Methods 2015; 260:73-82. [PMID: 25911067 DOI: 10.1016/j.jneumeth.2015.04.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 04/03/2015] [Accepted: 04/08/2015] [Indexed: 12/31/2022]
Abstract
Malformations of cortical development constitute a variety of pathological brain abnormalities that commonly cause severe, medically-refractory epilepsy, including focal lesions, such as focal cortical dysplasia, heterotopias, and tubers of tuberous sclerosis complex, and diffuse malformations, such as lissencephaly. Although some cortical malformations result from environmental insults during cortical development in utero, genetic factors are increasingly recognized as primary pathogenic factors across the entire spectrum of malformations. Genes implicated in causing different cortical malformations are involved in a variety of physiological functions, but many are focused on regulation of cell proliferation, differentiation, and neuronal migration. Advances in molecular genetic methods have allowed the engineering of increasingly sophisticated animal models of cortical malformations and associated epilepsy. These animal models have identified some common mechanistic themes shared by a number of different cortical malformations, but also revealed the diversity and complexity of cellular and molecular mechanisms that lead to the development of the pathological lesions and resulting epileptogenesis.
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Affiliation(s)
- Michael Wong
- Department of Neurology and the Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO 63110, USA.
| | - Steven N Roper
- Department of Neurosurgery, University of Florida, Gainesville, FL 32610, USA
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7
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Models of cortical malformation--Chemical and physical. J Neurosci Methods 2015; 260:62-72. [PMID: 25850077 DOI: 10.1016/j.jneumeth.2015.03.034] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Revised: 03/27/2015] [Accepted: 03/30/2015] [Indexed: 11/21/2022]
Abstract
Pharmaco-resistant epilepsies, and also some neuropsychiatric disorders, are often associated with malformations in hippocampal and neocortical structures. The mechanisms leading to these cortical malformations causing an imbalance between the excitatory and inhibitory system are largely unknown. Animal models using chemical or physical manipulations reproduce different human pathologies by interfering with cell generation and neuronal migration. The model of in utero injection of methylazoxymethanol (MAM) acetate mimics periventricular nodular heterotopia. The freeze lesion model reproduces (poly)microgyria, focal heterotopia and schizencephaly. The in utero irradiation model causes microgyria and heterotopia. Intraperitoneal injections of carmustine 1-3-bis-chloroethyl-nitrosurea (BCNU) to pregnant rats produces laminar disorganization, heterotopias and cytomegalic neurons. The ibotenic acid model induces focal cortical malformations, which resemble human microgyria and ulegyria. Cortical dysplasia can be also observed following prenatal exposure to ethanol, cocaine or antiepileptic drugs. All these models of cortical malformations are characterized by a pronounced hyperexcitability, few of them also produce spontaneous epileptic seizures. This dysfunction results from an impairment in GABAergic inhibition and/or an increase in glutamatergic synaptic transmission. The cortical region initiating or contributing to this hyperexcitability may not necessarily correspond to the site of the focal malformation. In some models wide-spread molecular and functional changes can be observed in remote regions of the brain, where they cause pathophysiological activities. This paper gives an overview on different animal models of cortical malformations, which are mostly used in rodents and which mimic the pathology and to some extent the pathophysiology of neuronal migration disorders associated with epilepsy in humans.
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Zhou FW, Roper SN. Reduced chemical and electrical connections of fast-spiking interneurons in experimental cortical dysplasia. J Neurophysiol 2014; 112:1277-90. [PMID: 24944214 DOI: 10.1152/jn.00126.2014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Aberrant neural connections are regarded as a principal factor contributing to epileptogenesis. This study examined chemical and electrical connections between fast-spiking (FS), parvalbumin (PV)-immunoreactive (FS-PV) interneurons and regular-spiking (RS) neurons (pyramidal neurons or spiny stellate neurons) in a rat model of prenatal irradiation-induced cortical dysplasia. Presynaptic action potentials were evoked by current injection and the elicited unitary inhibitory or excitatory postsynaptic potentials (uIPSPs or uEPSPs) were recorded in the postsynaptic cell. In dysplastic cortex, connection rates between presynaptic FS-PV interneurons and postsynaptic RS neurons and FS-PV interneurons, and uIPSP amplitudes were significantly smaller than controls, but both failure rates and coefficient of variation of uIPSP amplitudes were larger than controls. In contrast, connection rates from RS neurons to FS-PV interneurons and uEPSPs amplitude were similar in the two groups. Assessment of the paired pulse ratio showed a significant decrease in synaptic release probability at FS-PV interneuronal terminals, and the density of terminal boutons on axons of biocytin-filled FS-PV interneurons was also decreased, suggesting presynaptic dysfunction in chemical synapses formed by FS-PV interneurons. Electrical connections were observed between FS-PV interneurons, and the connection rates and coupling coefficients were smaller in dysplastic cortex than controls. In dysplastic cortex, we found a reduced synaptic efficiency for uIPSPs originating from FS-PV interneurons regardless of the type of target cell, and impaired electrical connections between FS-PV interneurons. This expands our understanding of the fundamental impairment of inhibition in this model and may have relevance for certain types of human cortical dysplasia.
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Affiliation(s)
- Fu-Wen Zhou
- Department of Neurosurgery and the McKnight Brain Institute, University of Florida, Gainesville, Florida
| | - Steven N Roper
- Department of Neurosurgery and the McKnight Brain Institute, University of Florida, Gainesville, Florida
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Zhou FW, Roper SN. TRPC3 mediates hyperexcitability and epileptiform activity in immature cortex and experimental cortical dysplasia. J Neurophysiol 2013; 111:1227-37. [PMID: 24353305 DOI: 10.1152/jn.00607.2013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Neuronal hyperexcitability plays an important role in epileptogenesis. Conditions of low extracellular calcium (Ca) or magnesium (Mg) can induce hyperexcitability and epileptiform activity with unclear mechanisms. Transient receptor potential canonical type 3 (TRPC3) channels play a pivotal role in neuronal excitability and are activated in low-Ca and/or low-Mg conditions to depolarize neurons. TRPC3 staining was highly enriched in immature, but very weak in mature, control cortex, whereas it was strong in dysplastic cortex at all ages. Depolarization and susceptibility to epileptiform activity increased with decreasing Ca and Mg. Combinations of low Ca and low Mg induced larger depolarization in pyramidal neurons and greater susceptibility to epileptiform activity in immature and dysplastic cortex than in mature and control cortex, respectively. Intracellular application of anti-TRPC3 antibody to block TRPC3 channels and bath application of the selective TRPC3 inhibitor Pyr3 greatly diminished depolarization in immature control and both immature and mature dysplastic cortex with strong TRPC3 expression. Epileptiform activity was initiated in low Ca and low Mg when synaptic activity was blocked, and Pyr3 completely suppressed this activity. In conclusion, TRPC3 primarily mediates low Ca- and low Mg-induced depolarization and epileptiform activity, and the enhanced expression of TRPC3 could make dysplastic and immature cortex more hyperexcitable and more susceptible to epileptiform activity.
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Affiliation(s)
- Fu-Wen Zhou
- Department of Neurosurgery and McKnight Brain Institute, University of Florida, Gainesville, Florida
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Setkowicz Z, Gzieło-Jurek K, Uram Ł, Janicka D, Janeczko K. Brain dysplasia evoked by gamma irradiation at different stages of prenatal development leads to different tonic and clonic seizure reactivity. Epilepsy Res 2013; 108:66-80. [PMID: 24239322 DOI: 10.1016/j.eplepsyres.2013.10.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Revised: 09/27/2013] [Accepted: 10/18/2013] [Indexed: 11/17/2022]
Abstract
Rats with brain dysplasia evoked by interruption of different stages of prenatal neurogenesis show characteristic variations in susceptibility to seizures depending on the neurochemical specificity of pharmacological agents used to evoke seizures. To verify a discrepancy between the data obtained using different pharmacological models, neurochemically neutral electroshocks were applied here. To produce brain dysplasia of different degrees, pregnant Wistar rats were exposed to a single 1.0Gy dose of gamma rays on gestation days 13, 15, 17 or 19. From the postnatal day 60, their male offspring (E13s, E15s, E17s and E19s, respectively) were subjected to 21 daily electrical stimulations to evoke seizures. Profiles of tonic and clonic reactivity to electrical stimulation significantly differed from those observed following pilocarpine or kainic acid administration. E17s showed minimal intensity of tonic but maximal of clonic responses. On the contrary, very high tonic and low clonic reactivity was observed in E13s and E15s. Periventricular nodular heterotopias (PNHs) were observed exclusively in E15s and E17s. Generally, the size of PNHs was correlated positively with susceptibility to tonic seizures but negatively with susceptibility to clonic seizures. Analogous correlations with the size of the neocortex were opposite. E13s and E19s had brains devoid PNHs but showed high tonic seizure susceptibility similar to that in E15s. It can therefore be concluded that PNHs modified the type of seizure reactivity from tonic to clonic, depending of their size, but the presence of PNHs was not necessary for the development of seizure susceptibility itself.
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Affiliation(s)
- Zuzanna Setkowicz
- Department of Neuroanatomy, Institute of Zoology, Jagiellonian University, ul. Gronostajowa 9, 30-387 Kraków, Poland
| | - Kinga Gzieło-Jurek
- Department of Neuroanatomy, Institute of Zoology, Jagiellonian University, ul. Gronostajowa 9, 30-387 Kraków, Poland
| | - Łukasz Uram
- Department of Neuroanatomy, Institute of Zoology, Jagiellonian University, ul. Gronostajowa 9, 30-387 Kraków, Poland
| | - Dominika Janicka
- Department of Neuroanatomy, Institute of Zoology, Jagiellonian University, ul. Gronostajowa 9, 30-387 Kraków, Poland
| | - Krzysztof Janeczko
- Department of Neuroanatomy, Institute of Zoology, Jagiellonian University, ul. Gronostajowa 9, 30-387 Kraków, Poland.
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Akakin D, Martinez-Diaz H, Chen HX, Roper SN. Reduced densities of parvalbumin- and somatostatin-expressing interneurons in experimental cortical dysplasia and heterotopia in early postnatal development. Epilepsy Res 2013; 104:226-33. [DOI: 10.1016/j.eplepsyres.2012.11.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Revised: 09/20/2012] [Accepted: 11/09/2012] [Indexed: 10/27/2022]
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Zhou FW, Roper SN. Impaired hippocampal memory function and synaptic plasticity in experimental cortical dysplasia. Epilepsia 2012; 53:850-9. [PMID: 22417090 DOI: 10.1111/j.1528-1167.2012.03431.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
PURPOSE Memory impairment is a common comorbidity in people with epilepsy-associated malformations of cortical development. We studied spatial memory performance and hippocampal synaptic plasticity in an animal model of cortical dysplasia. METHODS Embryonic day 17 rats were exposed to 2.25 Gy external radiation. One-month-old rats were tested for spatial recognition memory. After behavioral testing, short-term and long-term synaptic plasticity in the hippocampal CA1 region was studied in an in vitro slice preparation. KEY FINDINGS Behavioral assessments showed impaired hippocampal CA1-dependent spatial recognition memory in irradiated rats. Neurophysiologic assessments showed that baseline synaptic transmission was significantly enhanced, whereas paired-pulse facilitation, long-term potentiation, and long-term depression of the field excitatory postsynaptic potential (fEPSP) slope at Schaffer collateral/commissural fiber-CA1 synapses were significantly reduced in the irradiated rats. Histologic observations showed dysplastic cortex and dispersed hippocampal pyramidal neurons. SIGNIFICANCE This study has shown that prenatally irradiated rats with cortical dysplasia exhibit a severe impairment of spatial recognition memory accompanied by disrupted short-term and long-term synaptic plasticity and may help to guide development of potential therapeutic interventions for this important problem.
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Affiliation(s)
- Fu-Wen Zhou
- Departments of Neurosurgery and the McKnight Brain Institute, University of Florida, 100 South Newell Drive, Gainesville, FL 32610, U.S.A.
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Moroni R, Cipelletti B, Inverardi F, Regondi M, Spreafico R, Frassoni C. Development of cortical malformations in BCNU-treated rat, model of cortical dysplasia. Neuroscience 2011; 175:380-93. [DOI: 10.1016/j.neuroscience.2010.11.061] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2010] [Revised: 11/25/2010] [Accepted: 11/30/2010] [Indexed: 01/30/2023]
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Zhou FW, Roper SN. Altered firing rates and patterns in interneurons in experimental cortical dysplasia. ACTA ACUST UNITED AC 2010; 21:1645-58. [PMID: 21084454 DOI: 10.1093/cercor/bhq234] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Cortical dysplasia (CD) is associated with severe epilepsy in humans, and the in utero irradiation of fetal rats provides a model of this disorder. These animals show a selective loss of inhibitory interneurons, and the surviving interneurons have a reduced excitatory synaptic drive. The current study was undertaken to see how alterations in synaptic input would affect spontaneous firing of interneurons in dysplastic cortex. We recorded spontaneous action potentials and excitatory and inhibitory postsynaptic currents (EPSCs and IPSCs, respectively) from somatostatin (SST)-, parvalbumin (PV)-, and calretinin (CR)-immunoreactive (ir) interneurons. We found that SST- and PV-ir interneurons fired less frequently and with less regularity than controls. This corresponded to a relative imbalance in the ratio of EPSCs to IPSCs that favored inhibition. In contrast, CR-ir interneurons from CD showed no differences from controls in spontaneous firing or ratio of EPSCs to IPSCs. Additional studies demonstrated that synaptic input had a powerful effect on spontaneous firing in all interneurons. These findings demonstrate that a relative reduction in excitatory drive results in less active SST- and PV-ir interneurons in irradiated rats. This would further impair cortical inhibition in these animals and may be an important mechanism of epileptogenesis.
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Affiliation(s)
- Fu-Wen Zhou
- Department of Neurosurgery and the McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
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Baka M, Uyanikgil Y, Ateş U, Kültürsay N. Investigation of maternal melatonin effect on the hippocampal formation of newborn rat model of intrauterine cortical dysplasia. Childs Nerv Syst 2010; 26:1575-81. [PMID: 20461523 DOI: 10.1007/s00381-010-1147-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2009] [Accepted: 03/31/2010] [Indexed: 10/19/2022]
Abstract
OBJECTIVES Cortical dysplasia is a cortical malformation resulting from any developmental defects during different periods of development. This study aims to investigate the hippocampal histopathological alterations in the neonates with cortical dysplasia due to the prenatal exposure to carmustine (1,3-bis (2-chloroethyl)-1-nitrosourea; BCNU) and the possible effects of prophylaxis with melatonin, a neuroprotective agent. METHODS Wistar albino female rats were randomly divided into four experimental groups; control, melatonin-treated, BCNU-exposed and BCNU-exposed+melatonin-treated. Light microscopy and immunohistochemistry were carried out on the newborn hippocampus. RESULTS Histopathology of hippocampus from the control and melatonin-treated groups showed continuity of migration and maturation as pathognomonic signs of the normal newborn hippocampus. Hippocampal cortex from the newborns exposed in utero to BCNU showed the histology of early embryonic hippocampal formation with immunohistochemical increase in the number of nestin positive cells and decreases in the immunoreactivity of glial fibrillary acidic protein (GFAP) and synaptophysin. These findings indicate a significant delay in hippocampal maturation, migration, and synaptogenesis. Intrauterine treatment of BCNU-exposed rats with melatonin resulted in histopathological features almost similar to control group. CONCLUSION It has been concluded that cortical dysplasia induced by intrauterine BCNU administration results in delayed hippocampal maturation, which is successfully restored by intrauterine melatonin treatment.
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Affiliation(s)
- Meral Baka
- Department of Histology and Embryology, Ege University School of Medicine, Bornova, Izmir, Turkey
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André VM, Cepeda C, Vinters HV, Huynh M, Mathern GW, Levine MS. Interneurons, GABAA currents, and subunit composition of the GABAA receptor in type I and type II cortical dysplasia. Epilepsia 2010; 51 Suppl 3:166-70. [PMID: 20618425 DOI: 10.1111/j.1528-1167.2010.02634.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Interneurons, gamma-aminobutyric acid (GABA)(A) receptor density, and subunit composition determine inhibitory function in pyramidal neurons and control excitability in cortex. Abnormalities in GABAergic cells or GABA(A) receptors could contribute to seizures in malformations of cortical development. Herein we review data obtained in resected cortex from pediatric epilepsy surgery patients with type I and type II cortical dysplasia (CD) and non-CD pathologies. Our studies found fewer interneurons immunolabeled for glutamic acid decarboxylase (GAD) in type II CD, whereas there were no changes in tissue from type I CD. GAD-labeled neurons had larger somata, and GABA transporter (VGAT and GAT1) staining showed a dense plexus surrounding cytomegalic neurons in type II CD. Functionally, neurons from type I CD tissue showed GABA currents with increased half maximal effective concentration compared to cells from the other groups. In type II CD, cytomegalic pyramidal neurons showed alterations in GABA currents, decreased sensitivity to zolpidem and zinc, and increased sensitivity to bretazenil. In addition, pyramidal neurons from type II CD displayed higher frequency of spontaneous inhibitory post synaptic currents. The GABAergic system is therefore, altered differently in cortex from type I and type II CD patients. Alterations in zolpidem, zinc, and bretazenil sensitivity and spontaneous inhibitory postsynaptic currents (IPSCs) suggest that type II CD neurons have altered GABA(A) receptor subunit composition and receive dense GABA inputs. These findings support the hypothesis that patients with type I and type II CD will respond differently to GABA receptor-mediated antiepileptic drugs and that cytomegalic neurons have features similar to immature neurons.
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Affiliation(s)
- Véronique M André
- Intellectual and Developmental Disabilities Research Center, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095, USA
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Zhou FW, Roper SN. Densities of glutamatergic and GABAergic presynaptic terminals are altered in experimental cortical dysplasia. Epilepsia 2010; 51:1468-76. [PMID: 20477846 DOI: 10.1111/j.1528-1167.2010.02583.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE Cortical dysplasia (CD) is a major cause of epilepsy in children and adults, but underlying mechanisms of epileptogenesis in this disorder are poorly understood. We have utilized the irradiated rat model to study an injury-based form of diffuse CD in rats. Prior studies in this model have shown reduced numbers of γ-aminobutyric acid (GABA)ergic interneurons and reduced inhibitory synaptic currents in pyramidal cells in CD. We analyzed the number of excitatory and inhibitory presynaptic terminals in the neocortex of irradiated rats to better characterize altered connectivity in experimental CD. METHODS Antibodies to vesicular glutamate transporter 1 (VGLUT1), vesicular glutamate transporter 2 (VGLUT2), vesicular GABA transporter (VGAT), and parvalbumin (PV) were used to quantify glutamatergic and GABAergic presynaptic terminals in control and dysplastic cortex. RESULTS We found that the density of VGLUT1 terminals was increased in CD in comparison to layers IV, V, and VI in control cortex. VGLUT2 terminals were increased in CD compared to layers IV and VI. VGAT terminals were reduced in CD compared to layers II/III, IV, and V in controls as were PV-immunoreactive somata and terminals. DISCUSSION These findings suggest an overall increase in excitatory synaptic connectivity and decrease in inhibitory synaptic connectivity in CD in irradiated rat. We propose that these changes contribute to hyperexcitability in these animals and may contribute to epileptogenicity in some forms of human CD.
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Affiliation(s)
- Fu-Wen Zhou
- Department of Neurosurgery and the McKnight Brain Institute, University of Florida, Gainesville, Florida, USA
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Zhou FW, Chen HX, Roper SN. Balance of inhibitory and excitatory synaptic activity is altered in fast-spiking interneurons in experimental cortical dysplasia. J Neurophysiol 2009; 102:2514-25. [PMID: 19692507 PMCID: PMC2775391 DOI: 10.1152/jn.00557.2009] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2009] [Accepted: 08/17/2009] [Indexed: 11/22/2022] Open
Abstract
Cortical dysplasia (CD) is a common cause of intractable epilepsy in children and adults. We have studied rats irradiated in utero as a model of CD to better understand mechanisms that underlie dysplasia-associated epilepsy. Prior studies have shown a reduction in the number of cortical interneurons and in the frequency of inhibitory postsynaptic currents (IPSCs) in pyramidal cells in this model. They have also shown a reduced frequency of spontaneous and miniature excitatory postsynaptic currents (EPSCs) in the surviving cortical interneurons. However, the inhibitory synaptic contacts were not examined in that study. The current experiments were performed to assess inhibitory synaptic activity in fast-spiking (FS) interneurons in irradiated rats and controls and the balance of excitatory and inhibitory synaptic activity in these cells. Whole cell recordings were obtained from layer IV FS cells in controls and comparable FS cells in irradiated rats. The frequency of spontaneous and miniature IPSCs was reduced in dysplastic cortex, but the amplitude of these currents was unchanged. Stimulus-evoked IPSCs showed short-term depression in control and short-term facilitation in dysplastic cortex. Simultaneous recording of spontaneous EPSCs and IPSCs showed a shift in the ratio of excitation-to-inhibition in favor of inhibition in FS cells from dysplastic cortex. The same shift toward inhibition was seen when miniature EPSCs and IPSCs were examined. These results show that FS cells in dysplastic cortex have a relative lack of excitatory drive. This may result in an important class of inhibitory cells that are less able to perform their normal function especially in periods of increased excitatory activity.
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Affiliation(s)
- Fu-Wen Zhou
- Department of Neurosurgery and the McKnight Brain Institute, University of Florida, Gainesville, Florida 32610, USA
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Kanold PO. Subplate neurons: crucial regulators of cortical development and plasticity. Front Neuroanat 2009; 3:16. [PMID: 19738926 PMCID: PMC2737439 DOI: 10.3389/neuro.05.016.2009] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2009] [Accepted: 08/03/2009] [Indexed: 01/14/2023] Open
Abstract
The developing cerebral cortex contains a distinct class of cells, subplate neurons, which form one of the first functional cortical circuits. Subplate neurons reside in the cortical white matter, receive thalamic inputs and project into the developing cortical plate, mostly to layer 4. Subplate neurons are present at key time points during development. Removal of subplate neurons profoundly affects cortical development. Subplate removal in visual cortex prevents the maturation of thalamocortical synapse, the maturation of inhibition in layer 4, the development of orientation selective responses in individual cortical neurons, and the formation of ocular dominance columns. In addition, monocular deprivation during development reveals that ocular dominance plasticity is paradoxical in the absence of subplate neurons. Because subplate neurons projecting to layer 4 are glutamatergic, these diverse deficits following subplate removal were hypothesized to be due to lack of feed-forward thalamic driven cortical excitation. A computational model of the developing thalamocortical pathway incorporating feed-forward excitatory subplate projections replicates both normal development and plasticity of ocular dominance as well as the effects of subplate removal. Therefore, we postulate that feed-forward excitatory projections from subplate neurons into the developing cortical plate enhance correlated activity between thalamus and layer 4 and, in concert with Hebbian learning rules in layer 4, allow maturational and plastic processes in layer 4 to commence. Thus subplate neurons are a crucial regulator of cortical development and plasticity, and damage to these neurons might play a role in the pathology of many neurodevelopmental disorders.
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Affiliation(s)
- Patrick O. Kanold
- Department of Biology, Institute for Systems Research, and Program in Neuroscience and Cognitive Science, University of MarylandCollege Park, MD, USA,*Correspondence: Patrick O. Kanold, Department of Biology, University of Maryland, 1116 Biosciences Research Building, College Park, MD 20742, USA. e-mail:
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André VM, Cepeda C, Vinters HV, Huynh M, Mathern GW, Levine MS. Pyramidal cell responses to gamma-aminobutyric acid differ in type I and type II cortical dysplasia. J Neurosci Res 2009; 86:3151-62. [PMID: 18615638 DOI: 10.1002/jnr.21752] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Abnormalities in the gamma-aminobutyric acid (GABA)-ergic system could be responsible for seizures in cortical dysplasia (CD). We examined responses of pyramidal neurons to exogenous application of GABA, as well as alterations of GABAergic interneuron number and size in pediatric epilepsy surgery patients with non-CD, type I CD, and type II CD pathologies. We used the dissociated cell preparation for electrophysiology along with immunohistochemistry to identify number and size of GABAergic cells. Pyramidal neurons from type I CD tissue showed increased EC(50) and faster kinetics compared with cells from non-CD and type II CD tissue. Cytomegalic pyramidal neurons showed increased GABA peak currents and decreased peak current densities, longer kinetics, and decreased sensitivity to zolpidem and zinc compared with normal pyramidal cells from non-CD and type I CD. There were fewer but larger glutamic acid decarboxylase (GAD)-containing cells in type II CD tissue with cytomegalic neurons compared with non-CD, type I CD, and type II CD without cytomegalic neurons. In addition, GABA transporters (VGAT and GAT-1) showed increased staining surrounding cytomegalic neurons in type II CD tissue. These results indicate that there are differences in GABA(A) receptor-mediated pyramidal cell responses in type I and type II CD. Alterations in zolpidem and zinc sensitivities also suggest that cytomegalic neurons have altered GABA(A) receptor subunit composition. These findings support the hypothesis that patients with type I and type II CD will respond differently to GABA-mediated antiepileptic drugs and that cytomegalic neurons have features similar to immature neurons with prolonged GABA(A) receptor open channel times.
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Affiliation(s)
- Véronique M André
- Mental Retardation Research Center, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA.
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Schaefer AW, Juliano SL. Migration of transplanted neural progenitor cells in a ferret model of cortical dysplasia. Exp Neurol 2007; 210:67-82. [PMID: 18061166 DOI: 10.1016/j.expneurol.2007.10.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2007] [Revised: 09/19/2007] [Accepted: 10/03/2007] [Indexed: 01/17/2023]
Abstract
Although altered gene expression clearly causes failure of the neocortex to form properly, many causes of neocortical dysplasia arise from environmental or unknown factors. Our lab studies a model of cortical dysplasia induced by injection of methylazoxymethanol (MAM) into pregnant ferrets on embryonic day 33 (E33), which shares many features of neocortical dysplasia in humans. E33 MAM treatment results in characteristic deficits that include dramatic reduction of layer 4 in somatosensory cortex, widespread termination of thalamic afferents, and altered distribution of GABAergic elements. We determined the ability of immature cells to migrate into MAM-treated cortex using ferret neural progenitor cells obtained at E27 and E33 and mouse neural progenitor cells obtained at E14. When these cells were transplanted into organotypic cultures obtained from normal and E33 MAM-treated ferret cortex prepared on postnatal day 0 (P0), all progenitor cells migrated similarly in both hosts, preferentially residing in the upper cortical plate. The site of transplantation was significant, however, so that injections into the ventricular zone were more likely to reach the cortical plate than transplants into the intermediate zone. When similar cells were transplanted into ferret kits, approximately P7-P9, and allowed to survive for 2-4 weeks, the donor cells migrated differently and also reached distinct destinations in normal and MAM-treated hosts. MAM-treated cortex was more permissive to invasion by donor cells as they migrated to widespread aspects of the cortex, whereas transplants in normal host cortex were more restricted. E27 neural progenitor cells populated more cortical layers than later born E33 neural progenitor cells, suggesting that the fate of transplanted cells is governed by a combination of extrinsic and intrinsic factors.
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Uyanikgil Y, Baka M, Ateş U, Turgut M, Yavaşoğlu A, Ulker S, Sözmen EY, Sezer E, Elmas C, Yurtseven ME. Neuroprotective effects of melatonin upon the offspring cerebellar cortex in the rat model of BCNU-induced cortical dysplasia. Brain Res 2007; 1160:134-44. [PMID: 17572393 DOI: 10.1016/j.brainres.2007.05.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2007] [Revised: 05/15/2007] [Accepted: 05/17/2007] [Indexed: 10/23/2022]
Abstract
Cortical dysplasia is a malformation characterized by defects in proliferation, migration and maturation. This study was designed to evaluate the alterations in offspring rat cerebellum induced by maternal exposure to carmustine-[1,3-bis (2-chloroethyl)-1-nitrosoure] (BCNU) and to investigate the effects of exogenous melatonin upon cerebellar BCNU-induced cortical dysplasia, using histological and biochemical analyses. Pregnant Wistar rats were assigned to five groups: intact-control, saline-control, melatonin-treated, BCNU-exposed and BCNU-exposed plus melatonin. Rats were exposed to BCNU on embryonic day 15 and melatonin was given until delivery. Immuno/histochemistry and electron microscopy were carried out on the offspring cerebellum, and levels of malondialdehyde and superoxide dismutase were determined. Histopathologically, typical findings were observed in the cerebella from the control groups, but the findings consistent with early embryonic development were noted in BCNU-exposed cortical dysplasia group. There was a marked increase in the number of TUNEL positive cells and nestin positive cells in BCNU-exposed group, but a decreased immunoreactivity to glial fibrillary acidic protein, synaptophysin and transforming growth factor beta1 was observed, indicating a delayed maturation, and melatonin significantly reversed these changes. Malondialdehyde level in BCNU-exposed group was higher than those in control groups and melatonin decreased malondialdehyde levels in BCNU group (P<0.01), while there were no significant differences in the superoxide dismutase levels between these groups. These data suggest that exposure of animals to BCNU during pregnancy leads to delayed maturation of offspring cerebellum and melatonin protects the cerebellum against the effects of BCNU.
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Affiliation(s)
- Yiğit Uyanikgil
- Department of Histology and Embryology, Ege University School of Medicine, TR-35100 Izmir, Turkey
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Poluch S, Jablonska B, Juliano SL. Alteration of interneuron migration in a ferret model of cortical dysplasia. ACTA ACUST UNITED AC 2007; 18:78-92. [PMID: 17443019 DOI: 10.1093/cercor/bhm032] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
During cerebral cortical development, gamma-aminobutyric acidergic (GABAergic) interneurons arise from a different site than projection neurons. GABAergic cells are generated in the subpallial ganglionic eminence (GE), while excitatory projection neurons arise from the neocortical ventricular zone. Our laboratory studies a model of cortical dysplasia that displays specific disruption of GABAergic mechanisms and an alteration in the overall balance of excitation in the neocortex. To produce this model, the birth of neurons on a specific gestational day in ferrets (embryonic day 33 [E33]) is interrupted by injection of the antimitotic methylazoxymethanol (MAM). We hypothesized that migration of interneurons might be disrupted in this cortical dysplasia paradigm. We observed that although interneurons migrate into the neocortex in both normal and dysplastic cortex, the migrating cells become disoriented over time after E33 MAM treatment. Coculture experiments using normal GE and MAM-treated cortex (and vice versa) demonstrate that cues dictating proper orientation of migrating interneurons arise from the cortex and are not intrinsic to the migrating cells. As a consequence, interneurons in mature brains of MAM-treated animals are abnormally distributed. We report that GABA(A) receptor activation is crucial to the proper positioning of interneurons migrating into the cortex from the GE in normal and MAM-treated animals.
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Affiliation(s)
- Sylvie Poluch
- Department of Anatomy, Physiology and Genetics, USUHS, Bethesda, MD 20814, USA
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Temporal Lobe Epilepsy. Neurobiol Dis 2007. [DOI: 10.1016/b978-012088592-3/50035-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] Open
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Cepeda C, André VM, Levine MS, Salamon N, Miyata H, Vinters HV, Mathern GW. Epileptogenesis in pediatric cortical dysplasia: the dysmature cerebral developmental hypothesis. Epilepsy Behav 2006; 9:219-35. [PMID: 16875879 DOI: 10.1016/j.yebeh.2006.05.012] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2006] [Revised: 05/22/2006] [Accepted: 05/26/2006] [Indexed: 10/24/2022]
Abstract
Cortical dysplasia (CD) is the most frequent pathology found in pediatric epilepsy surgery patients with a nearly 80% incidence in children younger than 3 years of age. Younger cases are more likely to have multilobar and severe forms of CD compared with older patients with focal and mild CD. Using clinico-pathologic techniques, we have initiated studies that unravel the timing of CD pathogenesis that in turn suggest mechanisms of epileptogenesis. Morphological comparisons provided the first clue when we observed that cytomegalic neurons have similarities with human subplate cells, and balloon cells have features analogous to radial glia. This suggested that failure of prenatal cell degeneration before birth could explain the presence of postnatal dysmorphic cells in CD tissue. Neuronal density and MRI volumes indicate that there were more neurons than expected in CD tissue, and they were probably produced in later neurogenesis cell cycles. Together these findings imply that there is partial failure in later phases of cortical development that might explain the distinctive histopathology of CD. If correct, epileptogenesis should be the consequence of incomplete cellular maturation in CD tissue. In vitro electrophysiological findings are consistent with this notion. They show that balloon cells have glial features, cytomegalic neurons and recently discovered cytomegalic interneurons reveal atypical hyperexcitable intrinsic membrane properties, there are more GABA than glutamate spontaneous synaptic inputs onto neurons, and in a subset of cells NMDA and GABA(A) receptor-mediated responses and subunit expression are similar to those of immature neurons. Our studies support the hypothesis that there are retained prenatal cells and neurons with immature cellular and synaptic properties in pediatric CD tissue. We propose that local interactions of dysmature cells with normal postnatal neurons produce seizures. This hypothesis will drive future studies aimed at elucidating mechanisms of epileptogenesis in pediatric CD tissue.
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Affiliation(s)
- Carlos Cepeda
- Division of Neurosurgery, Department of Neurology, The Brain Research Institute and The Mental Retardation Research Center, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
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Robinson S, Li Q, Dechant A, Cohen ML. Neonatal loss of gamma-aminobutyric acid pathway expression after human perinatal brain injury. J Neurosurg 2006; 104:396-408. [PMID: 16776375 PMCID: PMC1762128 DOI: 10.3171/ped.2006.104.6.396] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT Perinatal brain injury leads to chronic neurological deficits in children. Damage to the premature brain produces white matter lesions (WMLs), but the impact on cortical development is less well defined. Gamma-aminobutyric acid(GABA)ergic neurons destined for the cerebral cortex migrate through the developing white matter and form the subplate during late gestation. The authors hypothesized that GABAergic neurons are vulnerable to perinatal systemic insults in premature infants, and that damage to these neurons contributes to impaired cortical development. METHODS An immunohistochemical analysis involving markers for oligodendrocytes, GABAergic neurons, axons, and apoptosis was performed on a consecutive series of 15 human neonatal telencephalon samples obtained postmortem from infants born at 25 to 32 weeks of gestation. The tissue samples were divided into two groups based on the presence or absence of WMLs by performing routine histological analyses. The expression of GABAergic neurons was compared between the two groups by using age-matched samples. Two-tailed t-tests were used for statistical analyses. Ten infants had WMLs and five did not. Significant losses of oligodendrocytes and axons and markedly increased apoptosis were appreciated in tissue samples from the infants with WMLs. Samples from infants with WMLs also showed significant losses of glutamic acid decarboxylase-67-positive cells and calretinin-positive cells, shorter neuropeptide Y-positive neurite lengths, and losses of cells expressing GABA(A)alpha1, GABA(B)R1, and N-acetylaspartate diethylamide NR1 receptors when these factors were compared with those in samples from infants without WMLs (all p < 0.02). CONCLUSIONS In addition to oligodendrocyte loss, axonal disruption, and excess apoptosis, a significant loss of telencephalon GABAergic neuron expression was found in neonatal brains with WMLs, compared with neonates' brains without WMLs. The loss of GABAergic subplate neurons in infants with WMLs may contribute to the pathogenesis of neurological deficits in children.
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Affiliation(s)
- Shenandoah Robinson
- Department of Neurosurgery, Division of Neuropathology, University Hospitals of Cleveland, Case Research Institute, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.
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Xiang H, Chen HX, Yu XX, King MA, Roper SN. Reduced excitatory drive in interneurons in an animal model of cortical dysplasia. J Neurophysiol 2006; 96:569-78. [PMID: 16641376 DOI: 10.1152/jn.01133.2005] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cortical dysplasia (CD) is strongly associated with epilepsy. Enhanced excitability in dysplastic neuronal networks is believed to contribute to epileptogenesis, but the underlying mechanisms for the hyperexcitability are poorly understood. Cortical GABAergic interneurons provide the principal inhibition in the neuronal networks by forming inhibitory synapses on excitatory neurons. The aim of the present study was to determine if the function of interneurons in CD is compromised. In a rat model of CD, in utero irradiation, we studied spontaneous and miniature excitatory postsynaptic currents (sEPSCs and mEPSCs) in cortical interneurons using whole cell recording techniques. Two types of interneurons, type I and type II, were identified based on their distinctive spike patterns and short-term synaptic plasticity. We found that the frequencies of sEPSCs and mEPSCs were significantly decreased in both types of interneurons in CD. However, the amplitude and kinetics of sEPSCs and mEPSCs were not different. Five-pulse, 20-Hz stimulation produced short-term depression in type I interneurons in both CD and control tissue. Type II interneurons showed a robust short-term facilitation in both CD and control tissue. Morphological analysis of biocytin-filled neurons revealed that dendritic trees of both types of interneurons were not altered in CD. Our results demonstrate that the excitatory drive, namely sEPSCs and mEPSCs, in two main types of interneuron is largely attenuated in CD, probably due to a reduction in the number of excitatory synapses on both types of interneurons in CD.
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Affiliation(s)
- Hui Xiang
- Department of Neurological Surgery and McKnight Brain Institute, University of Florida College of Medicine, Gainesville, USA
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Setkowicz Z, Janicka D, Kowalczyk A, Turlej A, Janeczko K. Congenital brain dysplasias of different genesis can differently affect susceptibility to pilocarpine- or kainic acid-induced seizures in the rat. Epilepsy Res 2005; 67:123-31. [PMID: 16226430 DOI: 10.1016/j.eplepsyres.2005.09.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2005] [Revised: 09/14/2005] [Accepted: 09/15/2005] [Indexed: 10/25/2022]
Abstract
Interruption of neurogenesis and/or neuronal migration produces brain dysplasia modifying susceptibility to epileptic seizures in adulthood. The course of neurogenesis has a strictly defined time-table. Consequently, the developmental stage at which the interruption occurs determines what functional subsystem potentially involved in epileptogenesis will suffer from irreversible neuronal deficit. The present study attempts to verify a hypothesis that brain dysplasias of different genesis should also lead to different susceptibility to seizures evoked by receptor agonists of different functional specificity, like kainic acid or pilocarpine, a cholinergic or glutaminergic agonist, respectively. Pregnant Wistar rats were exposed to gamma-rays on gestation days 13, 15, 17 or 19 (E13, E15, E17 or E19). Sixty-day-old offsprings of the females were injected with kainic acid or pilocarpine to evoke status epilepticus. During a 6-h period following the injection, motor manifestations of seizure activity were recorded. Generally, the intensity of pilocarpine-induced symptoms was relatively low in rats irradiated on E13 or E15 but high in rats irradiated on E17 or E19. In rats treated with kainic acid, the trend was opposite, viz. the later the prenatal irradiation was performed, the less intense epileptic symptoms were induced in adulthood. The data provide evidence that dysplasias acquired during prenatal development may significantly amplify or reduce the brain susceptibility to seizures. However, this relation depends not only on the developmental stage at which the dysplasias were produced but also on the functional specificity of epileptogenic stimuli used in the experimental model of epilepsy.
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Affiliation(s)
- Zuzanna Setkowicz
- Department of Neuroanatomy, Institute of Zoology, Jagiellonian University, 6 Ingardena St, 30 060 Kraków, Poland
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Setkowicz Z, Janeczko K. A strong epileptogenic effect of mechanical injury can be reduced in the dysplastic rat brain. Epilepsy Res 2005; 66:165-72. [PMID: 16150574 DOI: 10.1016/j.eplepsyres.2005.08.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2005] [Revised: 08/04/2005] [Accepted: 08/08/2005] [Indexed: 11/23/2022]
Abstract
An exposure of rats to gamma-radiation at different stages of prenatal development produces brain dysplasias of different degree displaying also different susceptibility to pilocarpine-induced seizures. Following irradiation on prenatal day 13 (E13), the susceptibility is minimal and significantly lower even in relation to non-irradiated rats [Setkowicz, Z., Janeczko, K., 2003. Long-term changes in susceptibility to pilocarpine-induced status epilepticus following neocortical injuries in the rat at different developmental stages. Epilepsy Res. 53, 216-224]. On the other hand, the rat brain injured on postnatal day 30 presents very high susceptibility to seizures in the same pilocarpine model of epilepsy [Setkowicz, Z., Kluk, K., Janeczko, K., 2003. Long-term changes in postnatal susceptibility to pilocarpine-induced seizures in rats exposed to gamma radiation at different stages of prenatal development. Epilepsia 44, 1267-1273]. It could, therefore, be hypothesised that the congenital brain dysplasia produced by irradiation on E13 would minimize the highly increased susceptibility to seizures observed in the injured brain. Wistar rats were exposed to gamma-rays on E13 and they received a mechanical brain injury on postnatal day 30 (P30). On postnatal day 60, pilocarpine was injected to evoke status epilepticus. During a 6-h period following the injection, motor manifestations of seizure activity were recorded and rated. Seven days after pilocarpine injection, the animals were sacrificed and their brains were fixed. Pilocarpine injections in non-irradiated rats with brains injured on P30 evoked seizures of very high intensity and extremely high mortality in relation to non-injured controls. This high susceptibility to seizures following the brain injury was considerably decreased in rats irradiated on E13. The data provide evidence that the brain dysplasia in the rat acquired at this stage of prenatal development can significantly reduce the increased susceptibility to seizures evoked by the postnatal brain injury.
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Affiliation(s)
- Zuzanna Setkowicz
- Department of Neuroanatomy, Institute of Zoology, Jagiellonian University, 6 Ingardena St., 30 060 Kraków, Poland
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