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Limbic and olfactory cortical circuits in focal seizures. Neurobiol Dis 2023; 178:106007. [PMID: 36682502 DOI: 10.1016/j.nbd.2023.106007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Revised: 01/17/2023] [Accepted: 01/18/2023] [Indexed: 01/22/2023] Open
Abstract
Epilepsies affecting the limbic regions are common and generate seizures often resistant to pharmacological treatment. Clinical evidence demonstrates that diverse regions of the mesial portion of the temporal lobe participate in limbic seizures; these include the hippocampus, the entorhinal, perirhinal and parahippocampal regions and the piriform cortex. The network mechanisms involved in the generation of olfactory-limbic epileptiform patterns will be here examined, with particular emphasis on acute interictal and ictal epileptiform discharges obtained by treatment with pro-convulsive drugs and by high-frequency stimulations on in vitro preparations, such as brain slices and the isolated guinea pig brain. The interactions within olfactory-limbic circuits can be summarized as follows: independent, region-specific seizure-like events (SLE) are generated in the olfactory and in the limbic cortex; SLEs generated in the hippocampal-parahippocampal regions tend to remain within these areas; the perirhinal region controls the neocortical propagation and the generalization of limbic seizures; interictal spiking in the olfactory regions prevents the invasion by SLEs generated in limbic regions. The potential relevance of these observations for human focal epilepsy is discussed.
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Moraes MFD, de Castro Medeiros D, Mourao FAG, Cancado SAV, Cota VR. Epilepsy as a dynamical system, a most needed paradigm shift in epileptology. Epilepsy Behav 2021; 121:106838. [PMID: 31859231 DOI: 10.1016/j.yebeh.2019.106838] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 11/22/2019] [Accepted: 12/01/2019] [Indexed: 01/08/2023]
Abstract
The idea of the epileptic brain being highly excitable and facilitated to synchronic activity has guided pharmacological treatment since the early twentieth century. Although tackling epilepsy's seizure-prone feature, by tonically modifying overall circuit excitability and/or connectivity, the last 50 years of drug development has not seen a substantial improvement in seizure suppression of refractory epilepsies. This review presents a new conceptual framework for epilepsy in which the temporal dynamics of the disease plays a more critical role in both its understanding and therapeutic strategies. The repetitive epileptiform pattern (characteristic during ictal activity) and other well-defined electrographic signatures (i.e., present during the interictal period) are discussed in terms of the sequential activation of the circuit motifs. Lessons learned from the physiological activation of neural circuitry are used to further corroborate the argument and explore the transition from proper function to a state of instability. Furthermore, the review explores how interfering in the temporally dependent abnormal connectivity between circuits may work as a therapeutic approach. We also review the use of probing stimulation to access network connectivity and evaluate its power to determine transitional states of the dynamical system as it moves towards regions of instability, especially when conventional electrographic monitoring is proven inefficient. Unorthodox cases, with little or no scalp electrographic correlate, in which ictogenic circuitry and/or seizure spread is temporally restricted to neurovegetative, cognitive, and motivational areas are shown as possible explanations for sudden death in epilepsy (SUDEP) and other psychiatric comorbidities. In short, this review presents a paradigm shift in the way that we address the disease and is aimed to encourage debate rather than narrow the rationale epilepsy is currently engaged in. This article is part of the Special Issue "NEWroscience 2018".
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Affiliation(s)
- Márcio Flávio Dutra Moraes
- Núcleo de Neurociências, Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil; Centro de Tecnologia e Pesquisa em Magneto Ressonância, Programa de Pós-Graduação em Engenharia Elétrica, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
| | - Daniel de Castro Medeiros
- Núcleo de Neurociências, Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Flávio Afonso Gonçalves Mourao
- Núcleo de Neurociências, Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil; Centro de Tecnologia e Pesquisa em Magneto Ressonância, Programa de Pós-Graduação em Engenharia Elétrica, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | | | - Vinicius Rosa Cota
- Laboratório Interdisciplinar de Neuroengenharia e Neurociências, Departamento de Engenharia Elétrica, Universidade Federal de São João Del-Rei, São João Del-Rei, Brazil
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Kajiwara R, Tominaga T. Perirhinal cortex area 35 controls the functional link between the perirhinal and entorhinal-hippocampal circuitry: D-type potassium channel-mediated gating of neural propagation from the perirhinal cortex to the entorhinal-hippocampal circuitry. Bioessays 2020; 43:e2000084. [PMID: 33236360 DOI: 10.1002/bies.202000084] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 10/15/2020] [Accepted: 10/15/2020] [Indexed: 11/07/2022]
Abstract
In several experimental conditions, neuronal excitation at the perirhinal cortex (PC) does not propagate to the entorhinal cortex (EC) due to a "wall" of inhibition, which may help to create functional coupling and un-coupling of the PC and EC in the medial temporal lobe. However, little is known regarding the coupling control process. Herein, we propose that the deep layer of area 35 in the PC plays a pivotal role in opening the gate for coupling, thus allowing the activity in the PC to propagate to the EC. Using voltage-sensitive dye imaging for the brain slices of rodents, we show that a slowly inactivating potassium conductance in this area is essential to induce excitation overtaking the inhibitory control. This coupling between the distinct neural circuits persists for at least 1 h. We elucidate further implications of this network-level plastic behavior and its mechanism.
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Affiliation(s)
- Riichi Kajiwara
- Department of Electronics and Bioinformatics, School of Science and Technology, Meiji University, Kawasaki, Japan
| | - Takashi Tominaga
- Laboratory for Neural Circuit Systems, Institute of Neuroscience, Tokushima Bunri University, Sanuki, Japan
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Medeiros DDC, Cota VR, Oliveira ACP, Moreira FA, Moraes MFD. The Endocannabinoid System Activation as a Neural Network Desynchronizing Mediator for Seizure Suppression. Front Behav Neurosci 2020; 14:603245. [PMID: 33281577 PMCID: PMC7691588 DOI: 10.3389/fnbeh.2020.603245] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2020] [Accepted: 10/20/2020] [Indexed: 01/08/2023] Open
Abstract
The understanding that hyper-excitability and hyper-synchronism in epilepsy are indissociably bound by a cause-consequence relation has only recently been challenged. Thus, therapeutic strategies for seizure suppression have often aimed at inhibiting excitatory circuits and/or activating inhibitory ones. However, new approaches that aim to desynchronize networks or compromise abnormal coupling between adjacent neural circuitry have been proven effective, even at the cost of enhancing local neuronal activation. Although most of these novel perspectives targeting circuitry desynchronization and network coupling have been implemented by non-pharmacological devices, we argue that there may be endogenous neurochemical systems that act primarily in the desynchronization component of network behavior rather than dampening excitability of individual neurons. This review explores the endocannabinoid system as one such possible pharmacological landmark for mimicking a form of "on-demand" desynchronization analogous to those proposed by deep brain stimulation in the treatment of epilepsy. This essay discusses the evidence supporting the role of the endocannabinoid system in modulating the synchronization and/or coupling of distinct local neural circuitry; which presents obvious implications on the physiological setting of proper sensory-motor integration. Accordingly, the process of ictogenesis involves pathological circuit coupling that could be avoided, or at least have its spread throughout the containment of other areas, if such endogenous mechanisms of control could be activated or potentiated by pharmacological intervention. In addition, we will discuss evidence that supports not only a weaker role played on neuronal excitability but the potential of the endocannabinoid system strengthening its modulatory effect, only when circuitry coupling surpasses a level of activation.
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Affiliation(s)
- Daniel de Castro Medeiros
- Núcleo de Neurociências, Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Vinícius Rosa Cota
- Laboratório Interdisciplinar de Neuroengenharia e Neurociências, Departamento de Engenharia Elétrica, Universidade Federal de São João Del-Rei, São João Del-Rei, Brazil
| | - Antonio Carlos P Oliveira
- Departamento de Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Fabricio A Moreira
- Departamento de Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Márcio Flávio Dutra Moraes
- Núcleo de Neurociências, Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.,Centro de Tecnologia e Pesquisa em Magneto Ressonância, Programa de Pós-Graduação em Engenharia Elétrica, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
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Johnson A, Grove RA, Madhavan D, Boone CHT, Braga C, Kyllo H, Samson K, Simeone K, Simeone T, Helikar T, Hanson CK, Adamec J. Changes in lipid profiles of epileptic mouse model. Metabolomics 2020; 16:106. [PMID: 33021695 PMCID: PMC10614666 DOI: 10.1007/s11306-020-01729-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2020] [Accepted: 09/23/2020] [Indexed: 12/21/2022]
Abstract
INTRODUCTION Approximately 1% of the world's population is impacted by epilepsy, a chronic neurological disorder characterized by seizures. One-third of epileptic patients are resistant to AEDs, or have medically refractory epilepsy (MRE). One non-invasive treatment that exists for MRE includes the ketogenic diet, a high-fat, low-carbohydrate diet. Despite the KD's success in seizure attenuation, it has a few risks and its mechanisms remain poorly understood. The KD has been shown to improve metabolism and mitochondrial function in epileptic phenotypes. Potassium channels have implications in epileptic conditions as they have dual roles as metabolic sensors and control neuronal excitation. OBJECTIVES The goal of this study was to explore changes in the lipidome in hippocampal and cortical tissue from Kv1.1-KO model of epilepsy. METHODS FT-ICR/MS analysis was utilized to examine nonpolar metabolome of cortical and hippocampal tissue isolated from a Kv1.1 channel knockout mouse model of epilepsy (n = 5) and wild-type mice (n = 5). RESULTS Distinct metabolic profiles were observed, significant (p < 0.05) features in hippocampus often being upregulated (FC ≥ 2) and the cortex being downregulated (FC ≤ 0.5). Pathway enrichment analysis shows lipid biosynthesis was affected. Partition ratio analysis revealed that the ratio of most metabolites tended to be increased in Kv1.1-/-. Metabolites in hippocampal tissue were commonly upregulated, suggesting seizure initiation in the hippocampus. Aberrant mitochondrial function is implicated by the upregulation of cardiolipin, a common component in the mitochondrial membrane. CONCLUSION Generally, our study finds that the lipidome is changed in the hippocampus and cortex in response to Kv1.1-KO indicating changes in membrane structural integrity and synaptic transmission.
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Affiliation(s)
- Alicia Johnson
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
| | - Ryan A Grove
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
| | - Deepak Madhavan
- Department of Neurological Sciences, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Cory H T Boone
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
| | - Camila Braga
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
| | - Hannah Kyllo
- Department of Neurological Sciences, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Kaeli Samson
- Department of Pharmacology, Creighton University School of Medicine, Omaha, NE, 68178, USA
| | - Kristina Simeone
- Department of Pharmacology, Creighton University School of Medicine, Omaha, NE, 68178, USA
| | - Timothy Simeone
- Department of Pharmacology, Creighton University School of Medicine, Omaha, NE, 68178, USA
| | - Tomas Helikar
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
| | - Corrine K Hanson
- College of Allied Health Professions, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Jiri Adamec
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA.
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Adotevi N, Lewczuk E, Sun H, Joshi S, Dabrowska N, Shan S, Williamson J, Kapur J. α-Amino-3-Hydroxy-5-Methyl-4-Isoxazolepropionic Acid Receptor Plasticity Sustains Severe, Fatal Status Epilepticus. Ann Neurol 2019; 87:84-96. [PMID: 31675128 DOI: 10.1002/ana.25635] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Revised: 10/30/2019] [Accepted: 10/30/2019] [Indexed: 01/06/2023]
Abstract
OBJECTIVE Generalized convulsive status epilepticus is associated with high mortality. We tested whether α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor plasticity plays a role in sustaining seizures, seizure generalization, and mortality observed during focal onset status epilepticus. We also determined whether modified AMPA receptors generated during status epilepticus could be targeted with a drug. METHODS Electrically induced status epilepticus was characterized by electroencephalogram and behavior in GluA1 knockout mice and in transgenic mice with selective knockdown of the GluA1 subunit in hippocampal principal neurons. Excitatory and inhibitory synaptic transmission in CA1 neurons was studied using patch clamp electrophysiology. The dose response of N,N,H,-trimethyl-5-([tricyclo(3.3.1.13,7)dec-1-ylmethyl]amino)-1-pentanaminiumbromide hydrobromide (IEM-1460), a calcium-permeable AMPA receptor antagonist, was determined. RESULTS Global removal of the GluA1 subunit did not affect seizure susceptibility; however, it reduced susceptibility to status epilepticus. GluA1 subunit knockout also reduced mortality, severity, and duration of status epilepticus. Absence of the GluA1 subunit prevented enhancement of glutamatergic synaptic transmission associated with status epilepticus; however, γ-aminobutyric acidergic synaptic inhibition was compromised. Selective removal of the GluA1 subunit from hippocampal principal neurons also reduced mortality, severity, and duration of status epilepticus. IEM-1460 rapidly terminated status epilepticus in a dose-dependent manner. INTERPRETATION AMPA receptor plasticity mediated by the GluA1 subunit plays a critical role in sustaining and amplifying seizure activity and contributes to mortality. Calcium-permeable AMPA receptors modified during status epilepticus can be inhibited to terminate status epilepticus. ANN NEUROL 2020;87:84-96.
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Affiliation(s)
- Nadia Adotevi
- Department of Neurology, University of Virginia, Charlottesville, VA
| | - Ewa Lewczuk
- Department of Neurology, University of Virginia, Charlottesville, VA
| | - Huayu Sun
- Department of Neurology, University of Virginia, Charlottesville, VA
| | - Suchitra Joshi
- Department of Neurology, University of Virginia, Charlottesville, VA
| | - Natalia Dabrowska
- Department of Neurology, University of Virginia, Charlottesville, VA
| | - Sarah Shan
- College of Arts and Sciences, University of Virginia, Charlottesville, VA
| | - John Williamson
- Department of Neurology, University of Virginia, Charlottesville, VA
| | - Jaideep Kapur
- Department of Neurology, University of Virginia, Charlottesville, VA.,Department of Neuroscience, University of Virginia, Charlottesville, VA.,UVA Brain Institute, University of Virginia, Charlottesville, VA
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Benkő Z, Moldován K, Szádeczky-Kardoss K, Zalányi L, Borbély S, Világi I, Somogyvári Z. Causal relationship between local field potential and intrinsic optical signal in epileptiform activity in vitro. Sci Rep 2019; 9:5171. [PMID: 30914731 PMCID: PMC6435742 DOI: 10.1038/s41598-019-41554-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Accepted: 03/11/2019] [Indexed: 11/10/2022] Open
Abstract
The directed causal relationship were examined between the local field potential (LFP) and the intrinsic optical signal (IOS) during induced epileptiform activity in in vitro cortical slices by the convergent cross-mapping causality analysis method. Two components of the IOS signal have been distinguished: a faster, activity dependent component (IOSh) which changes its sign between transmitted and reflected measurement, thus it is related to the reflectance or the scattering of the tissue and a slower component (IOSl), which is negative in both cases, thus it is resulted by the increase of the absorption of the tissue. We have found a strong, unidirectional, delayed causal effect from LFP to IOSh with 0.5-1s delay, without signs of feedback from the IOSh to the LFP, while the correlation was small and the peaks of the cross correlation function did not reflect the actual causal dependency. Based on these observations, a model has been set up to describe the dependency of the IOSh on the LFP power and IOSh was reconstructed, based on the LFP signal. This study demonstrates that causality analysis can lead to better understanding the physiological interactions, even in case of two data series with drastically different time scales.
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Affiliation(s)
- Zsigmond Benkő
- Theoretical Neuroscience and Complex Systems Research Group, Department of Computational Sciences, Wigner Research Center for Physics of the Hungarian Academy of Sciences, Budapest, H-1121, Hungary.,János Szentágothai Doctoral School of Neurosciences, Semmelweis University, Budapest, H-1085, Hungary
| | - Kinga Moldován
- Department of Physiology and Neurobiology, Eötvös Loránd University, Budapest, H-1117, Hungary
| | | | - László Zalányi
- Theoretical Neuroscience and Complex Systems Research Group, Department of Computational Sciences, Wigner Research Center for Physics of the Hungarian Academy of Sciences, Budapest, H-1121, Hungary
| | - Sándor Borbély
- Department of Physiology and Neurobiology, Eötvös Loránd University, Budapest, H-1117, Hungary
| | - Ildikó Világi
- Department of Physiology and Neurobiology, Eötvös Loránd University, Budapest, H-1117, Hungary
| | - Zoltán Somogyvári
- Theoretical Neuroscience and Complex Systems Research Group, Department of Computational Sciences, Wigner Research Center for Physics of the Hungarian Academy of Sciences, Budapest, H-1121, Hungary. .,Neuromicrosystems ltd., Budapest, H-1113, Hungary.
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Kajiwara R, Tominaga Y, Tominaga T. Network Plasticity Involved in the Spread of Neural Activity Within the Rhinal Cortices as Revealed by Voltage-Sensitive Dye Imaging in Mouse Brain Slices. Front Cell Neurosci 2019; 13:20. [PMID: 30804757 PMCID: PMC6378919 DOI: 10.3389/fncel.2019.00020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2018] [Accepted: 01/16/2019] [Indexed: 11/13/2022] Open
Abstract
The rhinal cortices, such as the perirhinal cortex (PC) and the entorhinal cortex (EC), are located within the bidirectional pathway between the neocortex and the hippocampus. Physiological studies indicate that the perirhinal transmission of neocortical inputs to the EC occurs at an extremely low probability, though many anatomical studies indicated strong connections exist in the pathway. Our previous study in rat brain slices indicated that an increase in excitability in deep layers of the PC/EC border initiated the neural activity transfer from the PC to the EC. In the present study, we hypothesized that such changes in network dynamics are not incidental observations but rather due to the plastic features of the perirhinal network, which links with the EC. To confirm this idea, we analyzed the network properties of neural transmission throughout the rhinal cortices and the plastic behavior of the network by performing a single-photon wide-field optical recording technique with a voltage-sensitive dye (VSD) in mouse brain slices of the PC, the EC, and the hippocampus. The low concentration of 4-aminopyridine (4-AP; 40 μM) enhanced neural activity in the PC, which eventually propagated to the EC via the deep layers of the PC/EC border. Interestingly, washout of 4-AP was unable to reverse entorhinal activation to the previous state. This change in the network property persisted for more than 1 h. This observation was not limited to the application of 4-AP. Burst stimulation to neurons in the perirhinal deep layers also induced the same change of network property. These results indicate the long-lasting modification of physiological connection between the PC and the EC, suggesting the existence of plasticity in the perirhinal-entorhinal network.
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Affiliation(s)
- Riichi Kajiwara
- Department of Electronics and Bioinformatics, School of Science and Technology, Meiji University, Kawasaki, Japan
| | - Yoko Tominaga
- Laboratory for Neural Circuit Systems, Institute of Neuroscience, Tokushima Bunri University, Sanuki, Japan
| | - Takashi Tominaga
- Laboratory for Neural Circuit Systems, Institute of Neuroscience, Tokushima Bunri University, Sanuki, Japan
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Lévesque M, Avoli M. Carbachol-Induced theta-like oscillations in the rodent brain limbic system: Underlying mechanisms and significance. Neurosci Biobehav Rev 2018; 95:406-420. [PMID: 30381251 DOI: 10.1016/j.neubiorev.2018.10.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 09/25/2018] [Accepted: 10/24/2018] [Indexed: 12/13/2022]
Abstract
Theta oscillations (4-12 Hz) represent one of the most prominent physiological oscillatory activity in the mammalian EEG. They are observed in several areas of the hippocampus and in parahippocampal structures. Theta oscillations play important roles in modulating synaptic plasticity during memory and learning; moreover, they are dependent on septal cholinergic inputs. Theta oscillations can be reproduced in vitro in several regions of the temporal lobe in the absence of the septum by employing the cholinergic agonist carbachol (CCh). Here, we review the mechanisms underlying CCh-induced theta oscillations. We address: (i) the ability of temporal lobe neuronal networks to oscillate independently at theta frequency during CCh treatment; (ii) the contribution of intrinsic ionic currents; (iii) the participation of principal cells and interneurons; and (iv) their pharmacological profiles. We also discuss the similarities between CCh-induced theta oscillations and physiological type II theta activity, as well as their roles in synaptic plasticity. Finally, we consider experimental evidence pointing to the contribution of spontaneous and CCh-induced theta activity to epileptiform synchronization.
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Affiliation(s)
- Maxime Lévesque
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery, and of Physiology, McGill University, 3801 University Street, Montréal, PQ, H3A 2B4, Canada
| | - Massimo Avoli
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery, and of Physiology, McGill University, 3801 University Street, Montréal, PQ, H3A 2B4, Canada; Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy.
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10
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Potassium dynamics and seizures: Why is potassium ictogenic? Epilepsy Res 2018; 143:50-59. [DOI: 10.1016/j.eplepsyres.2018.04.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 03/26/2018] [Accepted: 04/07/2018] [Indexed: 01/01/2023]
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11
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Tubi MA, Lutkenhoff E, Blanco MB, McArthur D, Villablanca P, Ellingson B, Diaz-Arrastia R, Van Ness P, Real C, Shrestha V, Engel J, Vespa PM. Early seizures and temporal lobe trauma predict post-traumatic epilepsy: A longitudinal study. Neurobiol Dis 2018; 123:115-121. [PMID: 29859872 DOI: 10.1016/j.nbd.2018.05.014] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 05/29/2018] [Indexed: 12/28/2022] Open
Abstract
OBJECTIVE Injury severity after traumatic brain injury (TBI) is a well-established risk factor for the development of post-traumatic epilepsy (PTE). However, whether lesion location influences the susceptibility of seizures and development of PTE longitudinally has yet to be defined. We hypothesized that lesion location, specifically in the temporal lobe, would be associated with an increased incidence of both early seizures and PTE. As secondary analysis measures, we assessed the degree of brain atrophy and functional recovery, and performed a between-group analysis, comparing patients who developed PTE with those who did not develop PTE. METHODS We assessed early seizure incidence (n = 90) and longitudinal development of PTE (n = 46) in a prospective convenience sample of patients with moderate-severe TBI. Acutely, patients were monitored with prospective cEEG and a high-resolution Magnetic Resonance Imaging (MRI) scan for lesion location classification. Chronically, patients underwent a high-resolution MRI, clinical assessment, and were longitudinally monitored for development of epilepsy for a minimum of 2 years post-injury. RESULTS Early seizures, occurring within the first week post-injury, occurred in 26.7% of the patients (n = 90). Within the cohort of subjects who had evidence of early seizures (n = 24), 75% had a hemorrhagic temporal lobe injury on admission. For longitudinal analyses (n = 46), 45.7% of patients developed PTE within a minimum of 2 years post-injury. Within the cohort of subjects who developed PTE (n = 21), 85.7% had a hemorrhagic temporal lobe injury on admission and 38.1% had early (convulsive or non-convulsive) seizures on cEEG monitoring during their acute ICU stay. In a between-group analysis, patients with PTE (n = 21) were more likely than patients who did not develop PTE (n = 25) to have a hemorrhagic temporal lobe injury (p < 0.001), worse functional recovery (p = 0.003), and greater temporal lobe atrophy (p = 0.029). CONCLUSION Our results indicate that in a cohort of patients with a moderate-severe TBI, 1) lesion location specificity (e.g. the temporal lobe) is related to both a high incidence of early seizures and longitudinal development of PTE, 2) early seizures, whether convulsive or non-convulsive in nature, are associated with an increased risk for PTE development, and 3) patients who develop PTE have greater chronic temporal lobe atrophy and worse functional outcomes, compared to those who do not develop PTE, despite matched injury severity characteristics. This study provides the foundation for a future prospective study focused on elucidating the mechanisms and risk factors for epileptogenesis.
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Affiliation(s)
- Meral A Tubi
- Imaging Genetics Center, Mark and Mary Stevens Neuroimaging and Informatics Institute, USC Keck School of Medicine, United States
| | | | | | | | | | | | | | - Paul Van Ness
- Department of Neurology and Neurophysiology, Baylor College of Medicine, United States
| | - Courtney Real
- David Geffen School of Medicine at UCLA, United States
| | | | - Jerome Engel
- David Geffen School of Medicine at UCLA, United States
| | - Paul M Vespa
- David Geffen School of Medicine at UCLA, United States.
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12
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Cota VR, Drabowski BMB, de Oliveira JC, Moraes MFD. The epileptic amygdala: Toward the development of a neural prosthesis by temporally coded electrical stimulation. J Neurosci Res 2017; 94:463-85. [PMID: 27091311 DOI: 10.1002/jnr.23741] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 03/09/2016] [Accepted: 03/09/2016] [Indexed: 02/06/2023]
Abstract
Many patients with epilepsy do not obtain proper control of their seizures through conventional treatment. We review aspects of the pathophysiology underlying epileptic phenomena, with a special interest in the role of the amygdala, stressing the importance of hypersynchronism in both ictogenesis and epileptogenesis. We then review experimental studies on electrical stimulation of mesiotemporal epileptogenic areas, the amygdala included, as a means to treat medically refractory epilepsy. Regular high-frequency stimulation (HFS) commonly has anticonvulsant effects and sparse antiepileptogenic properties. On the other hand, HFS is related to acute and long-term increases in excitability related to direct neuronal activation, long-term potentiation, and kindling, raising concerns regarding its safety and jeopardizing in-depth understanding of its mechanisms. In turn, the safer regular low-frequency stimulation (LFS) has a robust antiepileptogenic effect, but its pro- or anticonvulsant effect seems to vary at random among studies. As an alternative, studies by our group on the development and investigation of temporally unstructured electrical stimulation applied to the amygdala have shown that nonperiodic stimulation (NPS), which is a nonstandard form of LFS, is capable of suppressing both acute and chronic spontaneous seizures. We hypothesize two noncompetitive mechanisms for the therapeutic role of amygdala in NPS, 1) a direct desynchronization of epileptic circuitry in the forebrain and brainstem and 2) an indirect desynchronization/inhibition through nucleus accumbens activation. We conclude by reintroducing the idea that hypersynchronism, rather than hyperexcitability, may be the key for epileptic phenomena and epilepsy treatment.
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Affiliation(s)
- Vinícius Rosa Cota
- Laboratório Interdisciplinar de Neuroengenharia e Neurociências, Departamento de Engenharia Elétrica (DEPEL), Universidade Federal de São João Del-Rei, São João Del-Rei, Minas Gerais, Brazil
| | - Bruna Marcela Bacellar Drabowski
- Laboratório Interdisciplinar de Neuroengenharia e Neurociências, Departamento de Engenharia Elétrica (DEPEL), Universidade Federal de São João Del-Rei, São João Del-Rei, Minas Gerais, Brazil
| | - Jasiara Carla de Oliveira
- Laboratório Interdisciplinar de Neuroengenharia e Neurociências, Departamento de Engenharia Elétrica (DEPEL), Universidade Federal de São João Del-Rei, São João Del-Rei, Minas Gerais, Brazil
| | - Márcio Flávio Dutra Moraes
- Núcleo de Neurociências, Instituto de Ciências Biológicas (ICB), Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
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Hypersynchronous ictal onset in the perirhinal cortex results from dynamic weakening in inhibition. Neurobiol Dis 2015; 87:1-10. [PMID: 26699817 DOI: 10.1016/j.nbd.2015.12.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 11/23/2015] [Accepted: 12/10/2015] [Indexed: 11/23/2022] Open
Abstract
We obtained field, K(+) selective and "sharp" intracellular recordings from the rat entorhinal (EC) and perirhinal (PC) cortices in an in vitro brain slice preparation to identify the events occurring at interictal-to-ictal transition during 4-aminopyridine application. Field recordings revealed interictal- (duration: 1.1 to 2.2s) and ictal-like (duration: 31 to 103s) activity occurring synchronously in EC and PC; in addition, interictal spiking in PC increased in frequency shortly before the onset of ictal oscillatory activity thus resembling the hypersynchronous seizure onset seen in epileptic patients and in in vivo animal models. Intracellular recordings with K-acetate+QX314-filled pipettes in PC principal cells showed that spikes at ictal onset had post-burst hyperpolarizations (presumably mediated by postsynaptic GABAA receptors), which gradually decreased in amplitude. This trend was associated with a progressive positive shift of the post-burst hyperpolarization reversal potential. Finally, the transient elevations in [K(+)]o (up to 4.4mM from a base line of 3.2mM) - which occurred with the interictal events in PC - progressively increased (up to 7.3mM) with the spike immediately preceding ictal onset. Our findings indicate that hypersynchronous seizure onset in rat PC is caused by dynamic weakening of GABAA receptor signaling presumably resulting from [K(+)]o accumulation.
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Salaj M, Druga R, Cerman J, Kubová H, Barinka F. Calretinin and parvalbumin immunoreactive interneurons in the retrosplenial cortex of the rat brain: Qualitative and quantitative analyses. Brain Res 2015; 1627:201-15. [DOI: 10.1016/j.brainres.2015.09.031] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Revised: 09/20/2015] [Accepted: 09/26/2015] [Indexed: 02/04/2023]
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15
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Ortiz F, Gutiérrez R. Entorhinal cortex lesions result in adenosine-sensitive high frequency oscillations in the hippocampus. Exp Neurol 2015; 271:319-28. [DOI: 10.1016/j.expneurol.2015.06.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 05/19/2015] [Accepted: 06/07/2015] [Indexed: 12/17/2022]
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16
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Kano T, Inaba Y, D'Antuono M, Biagini G, Levésque M, Avoli M. Blockade of in vitro ictogenesis by low-frequency stimulation coincides with increased epileptiform response latency. J Neurophysiol 2015; 114:21-8. [PMID: 25925325 PMCID: PMC4493663 DOI: 10.1152/jn.00248.2015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Accepted: 04/29/2015] [Indexed: 11/22/2022] Open
Abstract
Low-frequency stimulation, delivered through transcranial magnetic or deep-brain electrical procedures, reduces seizures in patients with pharmacoresistant epilepsy. A similar control of ictallike discharges is exerted by low-frequency electrical stimulation in rodent brain slices maintained in vitro during convulsant treatment. By employing field and "sharp" intracellular recordings, we analyzed here the effects of stimuli delivered at 0.1 or 1 Hz in the lateral nucleus of the amygdala on ictallike epileptiform discharges induced by the K(+) channel blocker 4-aminopyridine in the perirhinal cortex, in a rat brain slice preparation. We found that 1) ictal events were nominally abolished when the stimulus rate was brought from 0.1 to 1 Hz; 2) this effect was associated with an increased latency of the epileptiform responses recorded in perirhinal cortex following each stimulus; and 3) both changes recovered to control values following arrest of the 1-Hz stimulation protocol. The control of ictal activity by 1-Hz stimulation and the concomitant latency increase were significantly reduced by GABAB receptor antagonism. We propose that this frequency-dependent increase in latency represents a short-lasting, GABAB receptor-dependent adaptive mechanism that contributes to decrease epileptiform synchronization, thus blocking seizures in epileptic patients and animal models.
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Affiliation(s)
- Toshiyuki Kano
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery and Physiology, McGill University, Montreal, Quebec, Canada
| | - Yuji Inaba
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery and Physiology, McGill University, Montreal, Quebec, Canada; Shinshu University, School of Medicine, Matsumoto, Japan; and
| | - Margherita D'Antuono
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery and Physiology, McGill University, Montreal, Quebec, Canada
| | - Giuseppe Biagini
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery and Physiology, McGill University, Montreal, Quebec, Canada; Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze, Università di Modena e Reggio Emilia, Modena, Italy
| | - Maxime Levésque
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery and Physiology, McGill University, Montreal, Quebec, Canada
| | - Massimo Avoli
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery and Physiology, McGill University, Montreal, Quebec, Canada;
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Vismer MS, Forcelli PA, Skopin MD, Gale K, Koubeissi MZ. The piriform, perirhinal, and entorhinal cortex in seizure generation. Front Neural Circuits 2015; 9:27. [PMID: 26074779 PMCID: PMC4448038 DOI: 10.3389/fncir.2015.00027] [Citation(s) in RCA: 116] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 05/15/2015] [Indexed: 12/11/2022] Open
Abstract
Understanding neural network behavior is essential to shed light on epileptogenesis and seizure propagation. The interconnectivity and plasticity of mammalian limbic and neocortical brain regions provide the substrate for the hypersynchrony and hyperexcitability associated with seizure activity. Recurrent unprovoked seizures are the hallmark of epilepsy, and limbic epilepsy is the most common type of medically-intractable focal epilepsy in adolescents and adults that necessitates surgical evaluation. In this review, we describe the role and relationships among the piriform (PIRC), perirhinal (PRC), and entorhinal cortex (ERC) in seizure-generation and epilepsy. The inherent function, anatomy, and histological composition of these cortical regions are discussed. In addition, the neurotransmitters, intrinsic and extrinsic connections, and the interaction of these regions are described. Furthermore, we provide evidence based on clinical research and animal models that suggest that these cortical regions may act as key seizure-trigger zones and, even, epileptogenesis.
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Affiliation(s)
- Marta S Vismer
- Department of Neurology, The George Washington University Washington, DC, USA
| | | | - Mark D Skopin
- Department of Neurology, The George Washington University Washington, DC, USA
| | - Karen Gale
- Department of Pharmacology, Georgetown University Washington, DC, USA
| | - Mohamad Z Koubeissi
- Department of Neurology, The George Washington University Washington, DC, USA
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Temporally unstructured electrical stimulation to the amygdala suppresses behavioral chronic seizures of the pilocarpine animal model. Epilepsy Behav 2014; 36:159-64. [PMID: 24935084 DOI: 10.1016/j.yebeh.2014.05.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Revised: 04/30/2014] [Accepted: 05/06/2014] [Indexed: 11/21/2022]
Abstract
Electrical stimulation applied to the basolateral amygdala in the pentylenetetrazole animal model of seizures may result in either a proconvulsant or an anticonvulsant effect depending on the interpulse intervals used: periodic or nonperiodic, respectively. We tested the effect of this electrical stimulation temporal coding on the spontaneous and recurrent behavioral seizures produced in the chronic phase of the pilocarpine animal model of temporal lobe epilepsy, an experimental protocol that better mimics the human condition. After 45 days of the pilocarpine-induced status epilepticus, male Wistar rats were submitted to a surgical procedure for the implantation of a bipolar electrical stimulation electrode in the right basolateral amygdala and were allowed to recover for seven days. The animals were then placed in a glass box, and their behaviors were recorded daily on DVD for 6h for 4 consecutive days (control period). Spontaneous recurrent behavioral seizures when showed in animals were further recorded for an extra 4-day period (treatment period), under periodic or nonperiodic electrical stimulation. The number, duration, and severity of seizures (according to the modified Racine's scale) during treatment were compared with those during the control period. The nonperiodically stimulated group displayed a significantly reduced total number and duration of seizures. There was no difference between control and treatment periods for the periodically stimulated group. Results corroborate previous findings from our group showing that nonperiodic electrical stimulation has a robust anticonvulsant property. In addition, results from the pilocarpine animal model further strengthen nonperiodic electrical stimulation as a valid therapeutic approach in current medical practice. Our working hypothesis is that temporally unstructured electrical stimulation may wield its effect by desynchronizing neural networks involved in the ictogenic process.
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Biagini G, D'Antuono M, Inaba Y, Kano T, Ragsdale D, Avoli M. Activity-dependent changes in excitability of perirhinal cortex networks in vitro. Pflugers Arch 2014; 467:805-16. [PMID: 24903241 DOI: 10.1007/s00424-014-1545-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 05/12/2014] [Accepted: 05/26/2014] [Indexed: 11/28/2022]
Abstract
Rat brain slices comprising the perirhinal cortex (PC) and a portion of the lateral nucleus of the amygdala (LA), in standard medium, can generate synchronous oscillatory activity that is associated with action potential discharge and reflects the activation of glutamatergic and GABAergic receptors. We report here that similar synchronous oscillatory events are recorded in the PC in response to single-shock, electrical stimuli delivered in LA. In addition, we found that the latency of these responses progressively increased when the stimulus interval was varied from 10 to 1 s; for example, the response latency during stimuli delivered at 1 Hz was more than twofold longer than that seen during stimulation at 0.1 Hz. This prolongation in latency occurred after approximately 5 stimuli, attained a steady value after 24-35 stimuli, and recovered to control values 30 s after stimulation arrest. These frequency-dependent changes in latency continued to occur during NMDA receptor antagonism but weakened following application of GABAA and/or GABAB receptor blockers. Our findings identify a new type of short-term plasticity that is mediated by GABA receptor function and may play a role in decreasing neuronal network synchronization during repeated activation. We propose that this frequency-dependent adaptive mechanism influences the excitability of limbic networks, thus potentially controlling epileptiform synchronization.
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Affiliation(s)
- Giuseppe Biagini
- Montreal Neurological Institute, McGill University, 3801 Rue University, Montreal, QC, H3A 2B4, Canada
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20
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Behr C, D'Antuono M, Hamidi S, Herrington R, Lévesque M, Salami P, Shiri Z, Köhling R, Avoli M. Limbic networks and epileptiform synchronization: the view from the experimental side. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2014; 114:63-87. [PMID: 25078499 DOI: 10.1016/b978-0-12-418693-4.00004-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In this review, we summarize findings obtained in acute and chronic epilepsy models and in particular experiments that have revealed how neuronal networks in the limbic system-which is closely involved in the pathophysiogenesis of mesial temporal lobe epilepsy (MTLE)-produce hypersynchronous discharges. MTLE is often associated with a typical pattern of brain damage known as mesial temporal sclerosis, and it is one of the most refractory forms of partial epilepsy in adults. Specifically, we will address the cellular and pharmacological features of abnormal electrographic events that, as in MTLE patients, can occur in in vivo and in vitro animal models; these include interictal and ictal discharges along with high-frequency oscillations. In addition, we will consider how different limbic structures made hyperexcitable by acute pharmacological manipulations interact during epileptiform discharge generation. We will also review the electrographic characteristics of two types of seizure onsets that are most commonly seen in human and experimental MTLE as well as in in vitro models of epileptiform synchronization. Finally, we will address the role played by neurosteroids in reducing epileptiform synchronization and in modulating epileptogenesis.
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Affiliation(s)
- Charles Behr
- Department of Neurology, Neurosurgery and Physiology, Montréal Neurological Institute, Montréal, Québec, Canada
| | - Margherita D'Antuono
- Department of Neurology, Neurosurgery and Physiology, Montréal Neurological Institute, Montréal, Québec, Canada
| | - Shabnam Hamidi
- Department of Neurology, Neurosurgery and Physiology, Montréal Neurological Institute, Montréal, Québec, Canada
| | - Rochelle Herrington
- Department of Neurology, Neurosurgery and Physiology, Montréal Neurological Institute, Montréal, Québec, Canada
| | - Maxime Lévesque
- Department of Neurology, Neurosurgery and Physiology, Montréal Neurological Institute, Montréal, Québec, Canada
| | - Pariya Salami
- Department of Neurology, Neurosurgery and Physiology, Montréal Neurological Institute, Montréal, Québec, Canada
| | - Zahra Shiri
- Department of Neurology, Neurosurgery and Physiology, Montréal Neurological Institute, Montréal, Québec, Canada
| | - Rüdiger Köhling
- Institute of Physiology, University of Rostock, Rostock, Germany
| | - Massimo Avoli
- Department of Neurology, Neurosurgery and Physiology, Montréal Neurological Institute, Montréal, Québec, Canada; Department of Experimental Medicine, Facoltà di Medicina e Odontoiatria, Sapienza Università di Roma, Roma, Italy.
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21
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Biagini G, D'Antuono M, Benini R, de Guzman P, Longo D, Avoli M. Perirhinal cortex and temporal lobe epilepsy. Front Cell Neurosci 2013; 7:130. [PMID: 24009554 PMCID: PMC3756799 DOI: 10.3389/fncel.2013.00130] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 08/01/2013] [Indexed: 12/30/2022] Open
Abstract
The perirhinal cortex—which is interconnected with several limbic structures and is intimately involved in learning and memory—plays major roles in pathological processes such as the kindling phenomenon of epileptogenesis and the spread of limbic seizures. Both features may be relevant to the pathophysiology of mesial temporal lobe epilepsy that represents the most refractory adult form of epilepsy with up to 30% of patients not achieving adequate seizure control. Compared to other limbic structures such as the hippocampus or the entorhinal cortex, the perirhinal area remains understudied and, in particular, detailed information on its dysfunctional characteristics remains scarce; this lack of information may be due to the fact that the perirhinal cortex is not grossly damaged in mesial temporal lobe epilepsy and in models mimicking this epileptic disorder. However, we have recently identified in pilocarpine-treated epileptic rats the presence of selective losses of interneuron subtypes along with increased synaptic excitability. In this review we: (i) highlight the fundamental electrophysiological properties of perirhinal cortex neurons; (ii) briefly stress the mechanisms underlying epileptiform synchronization in perirhinal cortex networks following epileptogenic pharmacological manipulations; and (iii) focus on the changes in neuronal excitability and cytoarchitecture of the perirhinal cortex occurring in the pilocarpine model of mesial temporal lobe epilepsy. Overall, these data indicate that perirhinal cortex networks are hyperexcitable in an animal model of temporal lobe epilepsy, and that this condition is associated with a selective cellular damage that is characterized by an age-dependent sensitivity of interneurons to precipitating injuries, such as status epilepticus.
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Affiliation(s)
- Giuseppe Biagini
- Laboratory of Experimental Epileptology, Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia Modena, Italy
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22
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Chen CR, Tan R, Qu WM, Wu Z, Wang Y, Urade Y, Huang ZL. Magnolol, a major bioactive constituent of the bark of Magnolia officinalis, exerts antiepileptic effects via the GABA/benzodiazepine receptor complex in mice. Br J Pharmacol 2012; 164:1534-46. [PMID: 21518336 DOI: 10.1111/j.1476-5381.2011.01456.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE The aim of this study was to evaluate the anti-convulsant effects of magnolol (6, 6', 7, 12-tetramethoxy-2, 2'-dimethyl-1-β-berbaman, C18H18O2) and the mechanisms involved. EXPERIMENTAL APPROACH Mice were treated with magnolol (20, 40 and 80 mg·kg(-1)) 30 min before injection with pentylenetetrazol (PTZ, 60 mg·kg(-1), i.p.). The anti-seizure effects of magnolol were analysed using seizure models of behaviour, EEG and in vitro electrophysiology and c-Fos expression in the hippocampus and cortex. KEY RESULTS Magnolol at doses of 40 and 80 mg·kg(-1) significantly delayed the onset of myoclonic jerks and generalized clonic seizures, and decreased the seizure stage and mortality compared with those of the vehicle-treated animals. EEG recordings showed that magnolol (40 and 80 mg·kg(-1)) prolonged the latency of seizure onset and decreased the number of seizure spikes. The anti-epileptic effect of magnolol was reversed by the GABA(A)/benzodiazepine receptor antagonist flumazenil. Pretreatment with flumazenil decreased the effects of magnolol on prolongation of seizure latency and decline of seizure stage. In a Mg(2+)-free model of epileptiform activity, using multi-electrode array recordings in mouse hippocampal slices, magnolol decreased spontaneous epileptiform discharges. Magnolol also significantly decreased seizure-induced Fos immunoreactivity in the piriform cortex, dentate gyrus and hippocampal area CA1. These effects were attenuated by pretreatment with flumazenil. CONCLUSIONS AND IMPLICATIONS These findings indicate that the inhibitory effects of magnolol on epileptiform activity were mediated by the GABA(A) /benzodiazepine receptor complex.
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Affiliation(s)
- C R Chen
- Department of Pharmacology, Shanghai Medical College, Fudan University, Shanghai, China
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23
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Calretinin, parvalbumin and calbindin immunoreactive interneurons in perirhinal cortex and temporal area Te3V of the rat brain: Qualitative and quantitative analyses. Brain Res 2012; 1436:68-80. [DOI: 10.1016/j.brainres.2011.12.014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Revised: 12/05/2011] [Accepted: 12/07/2011] [Indexed: 11/23/2022]
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Avoli M, de Curtis M. GABAergic synchronization in the limbic system and its role in the generation of epileptiform activity. Prog Neurobiol 2011; 95:104-32. [PMID: 21802488 PMCID: PMC4878907 DOI: 10.1016/j.pneurobio.2011.07.003] [Citation(s) in RCA: 193] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 07/14/2011] [Accepted: 07/15/2011] [Indexed: 11/30/2022]
Abstract
GABA is the main inhibitory neurotransmitter in the adult forebrain, where it activates ionotropic type A and metabotropic type B receptors. Early studies have shown that GABA(A) receptor-mediated inhibition controls neuronal excitability and thus the occurrence of seizures. However, more complex, and at times unexpected, mechanisms of GABAergic signaling have been identified during epileptiform discharges over the last few years. Here, we will review experimental data that point at the paradoxical role played by GABA(A) receptor-mediated mechanisms in synchronizing neuronal networks, and in particular those of limbic structures such as the hippocampus, the entorhinal and perirhinal cortices, or the amygdala. After having summarized the fundamental characteristics of GABA(A) receptor-mediated mechanisms, we will analyze their role in the generation of network oscillations and their contribution to epileptiform synchronization. Whether and how GABA(A) receptors influence the interaction between limbic networks leading to ictogenesis will be also reviewed. Finally, we will consider the role of altered inhibition in the human epileptic brain along with the ability of GABA(A) receptor-mediated conductances to generate synchronous depolarizing events that may lead to ictogenesis in human epileptic disorders as well.
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Affiliation(s)
- Massimo Avoli
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery, and of Physiology, McGill University, Montreal H3A 2B4 Quebec, Canada.
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25
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Salah A, Perkins KL. Persistent ictal-like activity in rat entorhinal/perirhinal cortex following washout of 4-aminopyridine. Epilepsy Res 2011; 94:163-76. [PMID: 21353480 DOI: 10.1016/j.eplepsyres.2011.01.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Revised: 01/25/2011] [Accepted: 01/26/2011] [Indexed: 11/27/2022]
Abstract
Application of 4-aminopyridine (4-AP, 100μM) in a solution containing 0.6mM Mg(2+) and 1.2mM Ca(2+) to hippocampal-entorhinal-perirhinal slices of adult rat brain induced ictal-like epileptiform activity in entorhinal and perirhinal cortices as revealed by electrophysiological field potential recordings. The ictal-like activity persisted after washing out the 4-AP. This persistence indicated that a change had occurred in the slice so that it was now "epileptic" in the absence of the convulsant 4-AP. Induction of persistent ictal-like activity was dependent upon the concentration of divalent cations during 4-AP exposure; that is, although 4-AP caused ictal-like activity in approximately half the slices in solution containing 1.6mM Mg(2+) and 2.0mM Ca(2+), this ictal-like activity did not persist upon washout of the 4-AP. Expression of the persistent ictal-like epileptiform activity required ionotropic glutamate-mediated synaptic transmission: application of the AMPA/kainate receptor antagonist NBQX after 4-AP washout reduced persistent ictal-like activity, and the combined application of NBQX and the NMDA receptor antagonist d-AP5 completely blocked it. In order to investigate the mechanism of induction of persistent ictal-like activity, several agents were applied before the introduction of 4-AP. Application of d-AP5 did not block the onset of ictal-like activity upon introduction of 4-AP but did prevent the persistence of the ictal-like activity upon washout of the 4-AP. In contrast, induction of persistent ictal-like activity was not prevented by simultaneous application of the group I metabotropic glutamate receptor (mGluR) antagonists LY 367385 and MPEP or by application of the protein synthesis inhibitor cycloheximide. In conclusion, we have characterized a new in vitro model of epileptogenesis in which induction of ictal-like activity is dependent upon NMDA receptor activation but not upon group I mGluR activation or protein synthesis.
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Affiliation(s)
- Alejandro Salah
- Program in Neural and Behavioral Science, State University of New York, Downstate Medical Center, Brooklyn, NY 11203, United States
| | - Katherine L Perkins
- Program in Neural and Behavioral Science, State University of New York, Downstate Medical Center, Brooklyn, NY 11203, United States; Department of Physiology and Pharmacology, State University of New York, Downstate Medical Center, Brooklyn, NY 11203, United States; Robert F. Furchgott Center for Neural and Behavioral Science, State University of New York, Downstate Medical Center, Brooklyn, NY 11203, United States
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26
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Cataldi M, Panuccio G, Cavaccini A, D'Antuono M, Taglialatela M, Avoli M. Involvement of inward rectifier and M-type currents in carbachol-induced epileptiform synchronization. Neuropharmacology 2010; 60:653-61. [PMID: 21144855 DOI: 10.1016/j.neuropharm.2010.11.023] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Revised: 11/25/2010] [Accepted: 11/29/2010] [Indexed: 11/16/2022]
Abstract
Exposure to cholinergic agonists is a widely used paradigm to induce epileptogenesis in vivo and synchronous activity in brain slices maintained in vitro. However, the mechanisms underlying these effects remain unclear. Here, we used field potential recordings from the lateral entorhinal cortex in horizontal rat brain slices to explore whether two different K(+) currents regulated by muscarinic receptor activation, the inward rectifier (K(IR)) and the M-type (K(M)) currents, have a role in carbachol (CCh)-induced field activity, a prototypical model of cholinergic-dependent epileptiform synchronization. To establish whether K(IR) or K(M) blockade could replicate CCh effects, we exposed slices to blockers of these currents in the absence of CCh. K(IR) channel blockade with micromolar Ba(2+) concentrations induced interictal-like events with duration and frequency that were lower than those observed with CCh; by contrast, the K(M) blocker linopirdine was ineffective. Pre-treatment with Ba(2+) or linopirdine increased the duration of epileptiform discharges induced by subsequent application of CCh. Baclofen, a GABA(B) receptor agonist that activates K(IR), abolished CCh-induced field oscillations, an effect that was abrogated by the GABA(B) receptor antagonist CGP 55845, and prevented by Ba(2+). Finally, when applied after CCh, the K(M) activators flupirtine and retigabine shifted leftward the cumulative distribution of CCh-induced event duration; this effect was opposite to what seen during linopirdine application under similar experimental conditions. Overall, our findings suggest that K(IR) rather than K(M) plays a major regulatory role in controlling CCh-induced epileptiform synchronization.
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Affiliation(s)
- Mauro Cataldi
- Division of Pharmacology, Department of Neuroscience, School of Medicine, Federico II University of Naples, Naples, Italy.
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de Lanerolle NC, Lee TS, Spencer DD. Astrocytes and epilepsy. Neurotherapeutics 2010; 7:424-38. [PMID: 20880506 PMCID: PMC5084304 DOI: 10.1016/j.nurt.2010.08.002] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2010] [Revised: 07/28/2010] [Accepted: 08/04/2010] [Indexed: 01/07/2023] Open
Abstract
Astrocytes form a significant constituent of seizure foci in the human brain. For a long time it was believed that astrocytes play a significant role in the causation of seizures. With the increase in our understanding of the unique biology of these cells, their precise role in seizure foci is receiving renewed attention. This article reviews the information now available on the role of astrocytes in the hippocampal seizure focus in patients with temporal lobe epilepsy with hippocampal sclerosis. Our intent is to try to integrate the available data. Astrocytes at seizure foci seem to not be a homogeneous population of cells, and in addition to typical glial fibrillary acidic protein, positive reactive astrocytes also include a population of neuron glia-2-like cells The astrocytes in sclerotic hippocampi differ from those in nonsclerotic hippocampi in their membrane physiology, having elevated Na+ channels and reduced inwardly rectifying potassium ion channels, and some having the capacity to generate action potentials. They also have reduced glutamine synthetase and increased glutamate dehydrogenase activity. The molecular interface between the astrocyte and microvasculature is also changed. The astrocytes are also associated with increased expression of many molecules normally concerned with immune and inflammatory functions. A speculative mechanism postulates that neuron glia-2-like cells may be involved in creating a high glutamate environment, whereas the function of more typical reactive astrocytes contribute to maintain high extracellular K+ levels; both factors contributing to the hyperexcitability of subicular neurons to generate epileptiform activity. The functions of the astrocyte vascular interface may be more critical to the processes involved in epileptogenesis.
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Affiliation(s)
- Nihal C de Lanerolle
- Department of Neurosurgery, Yale School of Medicine, New Haven, Connecticut 06520, USA.
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Kharatishvili I, Pitkänen A. Association of the severity of cortical damage with the occurrence of spontaneous seizures and hyperexcitability in an animal model of posttraumatic epilepsy. Epilepsy Res 2010; 90:47-59. [PMID: 20435440 DOI: 10.1016/j.eplepsyres.2010.03.007] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 02/07/2010] [Accepted: 03/12/2010] [Indexed: 11/29/2022]
Abstract
Posttraumatic epilepsy is a common consequence of traumatic brain injury in humans. Major predictors for the development of posttraumatic epilepsy include the severity of injury and occurrence of cortical contusions. The effect of the size or location of the cortical lesion on the risk of epileptogenesis, however, is poorly understood. Here, we investigated the extent and location of cortical damage and its association with a lowered seizure threshold and the occurrence of spontaneous seizures in rats (n=77) that had experienced moderate or severe lateral fluid-percussion brain injury (FPBI) 12 months earlier. Spontaneous seizures were detected with video-electroencephalography monitoring and a lowered seizure threshold was determined based on a pentylenetetrazol (PTZ) test. Cortical atrophy was evaluated from thionin-stained sections using the Cavalieri estimation in four different experiments in which rats developed either spontaneous recurrent seizures (i.e., epilepsy) or a lowered seizure threshold. Our data show that damage to the cortex ipsilateral to the injury was more severe and extended more caudally in epileptic animals than in those without epilepsy (p<0.05 and p<0.001 for 2 independent experiments). Further, the extent of the cortical damage correlated positively with chronically increased hyperexcitability (number of spikes in PTZ test) in animals with traumatic brain injury (r=-0.54, p<0.05; r=-0.72, p<0.01 for 2 independent experiments). Specifically, cortical lesions located at the level of the perirhinal, entorhinal, and postrhinal cortices were associated with a lowered seizure threshold and seizures. The severity of the cortical injury did not correlate with the severity of hippocampal damage. These findings indicate that, like in humans, the severity of cortical injury correlates with epileptogenesis and epilepsy in an experimental model of posttraumatic epilepsy.
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Affiliation(s)
- Irina Kharatishvili
- Epilepsy Research Laboratory, Department of Neurobiology, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, and Department of Neurology, Kuopio University Hospital, FIN-70211 Kuopio, Finland
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Laitinen T, Sierra A, Pitkänen A, Gröhn O. Diffusion tensor MRI of axonal plasticity in the rat hippocampus. Neuroimage 2010; 51:521-30. [DOI: 10.1016/j.neuroimage.2010.02.077] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 02/03/2010] [Accepted: 02/26/2010] [Indexed: 10/19/2022] Open
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Panuccio G, D'Antuono M, de Guzman P, De Lannoy L, Biagini G, Avoli M. In vitro ictogenesis and parahippocampal networks in a rodent model of temporal lobe epilepsy. Neurobiol Dis 2010; 39:372-80. [PMID: 20452424 DOI: 10.1016/j.nbd.2010.05.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2010] [Revised: 04/14/2010] [Accepted: 05/01/2010] [Indexed: 12/29/2022] Open
Abstract
Temporal lobe epilepsy (TLE) is a chronic epileptic disorder involving the hippocampal formation. Details on the interactions between the hippocampus proper and parahippocampal networks during ictogenesis remain, however, unclear. In addition, recent findings have shown that epileptic limbic networks maintained in vitro are paradoxically less responsive than non-epileptic control (NEC) tissue to application of the convulsant drug 4-aminopyridine (4AP). Field potential recordings allowed us to establish here the effects of 4AP in brain slices obtained from NEC and pilocarpine-treated epileptic rats; these slices included the hippocampus and parahippocampal areas such as entorhinal and perirhinal cortices and the amygdala. First, we found that both types of tissue generate epileptiform discharges with similar electrographic characteristics. Further investigation showed that generation of robust ictal-like discharges in the epileptic rat tissue is (i) favored by decreased hippocampal output (ii) reinforced by EC-subiculum interactions and (iii) predominantly driven by amygdala networks. We propose that a functional switch to alternative synaptic routes may promote network hyperexcitability in the epileptic limbic system.
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Affiliation(s)
- G Panuccio
- Montreal Neurological Institute and Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada
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31
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Benini R, Longo D, Biagini G, Avoli M. Perirhinal cortex hyperexcitability in pilocarpine-treated epileptic rats. Hippocampus 2010; 21:702-13. [PMID: 20865722 DOI: 10.1002/hipo.20785] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/22/2010] [Indexed: 11/09/2022]
Abstract
The perirhinal cortex (PC), which is heavily connected with several epileptogenic regions of the limbic system such as the entorhinal cortex and amygdala, is involved in the generation and spread of seizures. However, the functional alterations occurring within an epileptic PC network are unknown. Here, we analyzed this issue by using in vitro electrophysiology and immunohistochemistry in brain tissue obtained from pilocarpine-treated epileptic rats and age-matched, nonepileptic controls (NECs). Neurons recorded intracellularly from the PC deep layers in the two experimental groups had similar intrinsic and firing properties and generated spontaneous depolarizing and hyperpolarizing postsynaptic potentials with comparable duration and amplitude. However, spontaneous and stimulus-induced epileptiform discharges were seen with field potential recordings in over one-fifth of pilocarpine-treated slices but never in NEC tissue. These network events were reduced in duration by antagonizing NMDA receptors and abolished by NMDA + non-NMDA glutamatergic receptor antagonists. Pharmacologically isolated isolated inhibitory postsynaptic potentials had reversal potentials for the early GABA(A) receptor-mediated component that were significantly more depolarized in pilocarpine-treated cells. Experiments with a potassium-chloride cotransporter 2 antibody identified, in pilocarpine-treated PC, a significant immunostaining decrease that could not be explained by neuronal loss. However, interneurons expressing parvalbumin and neuropeptide Y were found to be decreased throughout the PC, whereas cholecystokinin-positive cells were diminished in superficial layers. These findings demonstrate synaptic hyperexcitability that is contributed by attenuated inhibition in the PC of pilocarpine-treated epileptic rats and underscore the role of PC networks in temporal lobe epilepsy.
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Affiliation(s)
- Ruba Benini
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, Canada
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Diverse antiepileptic drugs increase the ratio of background synaptic inhibition to excitation and decrease neuronal excitability in neurones of the rat entorhinal cortex in vitro. Neuroscience 2010; 167:456-74. [PMID: 20167261 PMCID: PMC2877872 DOI: 10.1016/j.neuroscience.2010.02.021] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2009] [Revised: 01/26/2010] [Accepted: 02/10/2010] [Indexed: 12/22/2022]
Abstract
Although most anti-epileptic drugs are considered to have a primary molecular target, it is clear that their actions are unlikely to be limited to effects on a single aspect of inhibitory synaptic transmission, excitatory transmission or voltage-gated ion channels. Systemically administered drugs can obviously simultaneously access all possible targets, so we have attempted to determine the overall effect of diverse agents on the balance between GABAergic inhibition, glutamatergic excitation and cellular excitability in neurones of the rat entorhinal cortex in vitro. We used an approach developed for estimating global background synaptic excitation and inhibition from fluctuations in membrane potential obtained by intracellular recordings. We have previously validated this approach in entorhinal cortical neurones [Greenhill and Jones (2007a) Neuroscience 147:884–892]. Using this approach, we found that, despite their differing pharmacology, the drugs tested (phenytoin, lamotrigine, valproate, gabapentin, felbamate, tiagabine) were unified in their ability to increase the ratio of background GABAergic inhibition to glutamatergic excitation. This could occur as a result of decreased excitation concurrent with increased inhibition (phenytoin, lamotrigine, valproate), a decrease in excitation alone (gabapentin, felbamate), or even with a differential increase in both (tiagabine). Additionally, we found that the effects on global synaptic conductances agreed well with whole cell patch recordings of spontaneous glutamate and GABA release (our previous studies and further data presented here). The consistency with which the synaptic inhibition:excitation ratio was increased by the antiepileptic drugs tested was matched by an ability of all drugs to concurrently reduce intrinsic neuronal excitability. Thus, it seems possible that specific molecular targets among antiepileptic drugs are less important than the ability to increase the inhibition:excitation ratio and reduce overall neuronal and network excitability.
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Pillay N, Fabinyi GC, Myles TS, Fitt GJ, Berkovic SF, Jackson GD. Parahippocampal epilepsy with subtle dysplasia: A cause of âimaging negativeâ partial epilepsy. Epilepsia 2009; 50:2611-8. [DOI: 10.1111/j.1528-1167.2009.02103.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Sankar T, Bernasconi N, Kim H, Bernasconi A. Temporal lobe epilepsy: differential pattern of damage in temporopolar cortex and white matter. Hum Brain Mapp 2008; 29:931-44. [PMID: 17636561 PMCID: PMC6870675 DOI: 10.1002/hbm.20437] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Our purpose was to quantify structural changes of the temporopolar cortex (TPC) and its white matter (TPWM) in temporal lobe epilepsy (TLE) using MRI volumetry and texture analysis. We studied 23 patients with hippocampal atrophy, and 20 healthy controls. Gradient magnitude and entropy were calculated to model signal intensity blurring on T1-MRI. Two observers assessed signal changes and atrophy visually. Compared to controls, TLE patients had a decrease in TPC and TPWM volume ipsilateral to the seizure focus. The gradient magnitude and entropy were decreased ipsilateral to the focus only in TPWM, indicating blurring of this compartment. Eighty-seven percent of TLE patients had at least one volumetric or textural abnormality. Although sensitivity of visual and quantitative assessment of TPC atrophy was comparable (43 and 39%), specificity was higher for volumetry (54% vs. 95%). Compared to visual analysis of signal changes in TPWM on T1-MRI, texture metrics had higher sensitivity (65% vs. 17%) and specificity (100% vs. 69%). The proportion of patients with blurring of TPWM as determined by texture analysis was higher than that seen on visual inspection of T2 images (78% vs. 43%). We found no clear association between volumetric or textural changes of TPC and TPWM and outcome after surgery. Structural changes of the anatomically distinct TPC and TPWM are found ipsilateral to the seizure focus in the majority of TLE patients with hippocampal sclerosis. MRI post-processing allows dissociating different pathological tissue characteristics and shows that atrophy involves gray and white matter, whereas blurring is confined to white matter.
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Affiliation(s)
- Tejas Sankar
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
- Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Neda Bernasconi
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
- Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Hosung Kim
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
- Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Andrea Bernasconi
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
- Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
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Zahn RK, Tolner EA, Derst C, Gruber C, Veh RW, Heinemann U. Reduced ictogenic potential of 4-aminopyridine in the perirhinal and entorhinal cortex of kainate-treated chronic epileptic rats. Neurobiol Dis 2008; 29:186-200. [DOI: 10.1016/j.nbd.2007.08.013] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2007] [Revised: 07/26/2007] [Accepted: 08/22/2007] [Indexed: 01/02/2023] Open
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de Guzman P, Inaba Y, Baldelli E, de Curtis M, Biagini G, Avoli M. Network hyperexcitability within the deep layers of the pilocarpine-treated rat entorhinal cortex. J Physiol 2008; 586:1867-83. [PMID: 18238812 DOI: 10.1113/jphysiol.2007.146159] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
In this study we report that in the presence of normal buffer, epileptiform discharges occur spontaneously (duration = 2.60 +/- 0.49 s) or can be induced by electrical stimuli (duration = 2.50 +/- 0.62 s) in the entorhinal cortex (EC) of brain slices obtained from pilocarpine-treated rats but not in those from age-matched, nonepileptic control (NEC) animals. These network-driven epileptiform events consist of field oscillatory sequences at frequencies greater than 200 Hz that most often initiate in the lateral EC and propagate to the medial EC with 4-63 ms delays. The NMDA receptor antagonist CPP depresses the rate of occurrence (P < 0.01) of these spontaneous epileptiform discharges but fails in blocking them. Paradoxically, stimulus-induced epileptiform responses are enhanced in duration during CPP application. However, concomitant application of NMDA and non-NMDA glutamatergic antagonists abolishes spontaneous and stimulus-induced epileptiform events. Intracellular recordings from lateral EC layer V cells indicate a lower frequency of spontaneous hyperpolarizing postsynaptic potentials in pilocarpine-treated tissue than in NEC (P < 0.002) both under control conditions and with glutamatergic receptor blockade; the reversal potential of pharmacologically isolated GABA(A) receptor-mediated inhibitory postsynaptic potentials has similar values in the two types of tissue. Finally, immunohistochemical analysis shows that parvalbumin-positive interneurons are selectively reduced in number in EC deep layers. Collectively, these results indicate that reduced inhibition within the pilocarpine-treated EC layer V may promote network epileptic hyperexcitability.
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Affiliation(s)
- Philip de Guzman
- Montreal Neurological Institute and Department of Neurology & Neurosurgery, McGill University, Montreal, QC H3A 2B4, Canada
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Ma DL, Tang YC, Tang FR. Cytoarchitectonics and afferent/efferent reorganization of neurons in layers II and III of the lateral entorhinal cortex in the mouse pilocarpine model of temporal lobe epilepsy. J Neurosci Res 2008; 86:1324-42. [DOI: 10.1002/jnr.21583] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Sudbury JR, Avoli M. Epileptiform synchronization in the rat insular and perirhinal cortices in vitro. Eur J Neurosci 2007; 26:3571-82. [PMID: 18052975 DOI: 10.1111/j.1460-9568.2007.05962.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The hippocampus plays a primary role in temporal lobe epilepsy, a common form of partial epilepsy in adults. Recent studies, however, indicate that extrahippocampal areas such as the perirhinal and insular cortices represent important participants in this epileptic disorder. By employing field potential recordings in the in vitro 4-aminopyridine model of temporal lobe epilepsy, we have investigated here the contribution of glutamatergic and GABAergic signaling to epileptiform activity in these structures. First, we provide evidence of epileptiform synchronicity between the perirhinal and insular cortices, and resolve some pharmacological and network mechanisms involved in sustaining the interictal- and ictal-like discharges recorded there. Second, we report that in the absence of ionotropic glutamatergic transmission, GABAergic networks produce synchronous potentials that spread between the perirhinal and insular cortices. Finally, we have established that such activity is modulated by activating micro-opioid receptors. Our findings support clinical and experimental evidence concerning the involvement of the perirhinal and insular cortex networks in temporal lobe epilepsy, and provide observations that may impact research focussing on the role of the insular cortex in nociception.
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Affiliation(s)
- Jessica R Sudbury
- Montreal Neurological Institute and Department of Neurology & Neurosurgery, McGill University, Montreal, H3A 2B4 QC, Canada
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Labyt E, Frogerais P, Uva L, Bellanger JJ, Wendling F. Modeling of Entorhinal Cortex and Simulation of Epileptic Activity: Insights Into the Role of Inhibition-Related Parameters. ACTA ACUST UNITED AC 2007; 11:450-61. [PMID: 17674628 PMCID: PMC2230631 DOI: 10.1109/titb.2006.889680] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
This paper describes a macroscopic neurophysiologically relevant model of the entorhinal cortex (EC), a brain structure largely involved in human mesio-temporal lobe epilepsy. This model is intervalidated in the experimental framework of ictogenesis animal model (isolated guinea-pig brain perfused with bicuculline). Using sensitivity and stability analysis, an investigation of model parameters related to GABA neurotransmission (recognized to be involved in epileptic activity generation) was performed. Based on spectral and statistical features, simulated signals generated from the model for multiple GABAergic inhibition-related parameter values were classified into eight classes of activity. Simulated activities showed striking agreement (in terms of realism) with typical epileptic activities identified in field potential recordings performed in the experimental model. From this combined computational/experimental approach, hypotheses are suggested about the role of different types of GABAergic neurotransmission in the generation of epileptic activities in EC.
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Affiliation(s)
- Etienne Labyt
- Inserm U642, Laboratoire Traitement du Signal et de L'Image, University of Rennes 1, 35042 Rennes, France.
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Gorter JA, van Vliet EA, Aronica E, Breit T, Rauwerda H, Lopes da Silva FH, Wadman WJ. Potential new antiepileptogenic targets indicated by microarray analysis in a rat model for temporal lobe epilepsy. J Neurosci 2006; 26:11083-110. [PMID: 17065450 PMCID: PMC6674659 DOI: 10.1523/jneurosci.2766-06.2006] [Citation(s) in RCA: 254] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
To get insight into the mechanisms that may lead to progression of temporal lobe epilepsy, we investigated gene expression during epileptogenesis in the rat. RNA was obtained from three different brain regions [CA3, entorhinal cortex (EC), and cerebellum (CB)] at three different time points after electrically induced status epilepticus (SE): acute phase [group D (1 d)], latent period [group W (1 week)], and chronic epileptic period [group M (3-4 months)]. A group that was stimulated but that had not experienced SE and later epilepsy was also included (group nS). Gene expression analysis was performed using the Affymetrix Gene Chip System (RAE230A). We used GENMAPP and Gene Ontology to identify global biological trends in gene expression data. The immune response was the most prominent process changed during all three phases of epileptogenesis. Synaptic transmission was a downregulated process during the acute and latent phases. GABA receptor subunits involved in tonic inhibition were persistently downregulated. These changes were observed mostly in both CA3 and EC but not in CB. Rats that were stimulated but that did not develop spontaneous seizures later on had also some changes in gene expression, but this was not reflected in a significant change of a biological process. These data suggest that the targeting of specific genes that are involved in these biological processes may be a promising strategy to slow down or prevent the progression of epilepsy. Especially genes related to the immune response, such as complement factors, interleukins, and genes related to prostaglandin synthesis and coagulation pathway may be interesting targets.
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Affiliation(s)
- Jan A Gorter
- Center for Neuroscience, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 SM, Amsterdam, The Netherlands.
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Noulhiane M, Samson S, Clémenceau S, Dormont D, Baulac M, Hasboun D. A volumetric MRI study of the hippocampus and the parahippocampal region after unilateral medial temporal lobe resection. J Neurosci Methods 2006; 156:293-304. [PMID: 16569437 DOI: 10.1016/j.jneumeth.2006.02.021] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2005] [Revised: 02/16/2006] [Accepted: 02/23/2006] [Indexed: 10/24/2022]
Abstract
Segmentation guidelines on high-resolution MRI designed to assess remaining volumes of the hippocampus and the parahippocampal cortices after medial temporal lobe (MTL) surgery could provide a useful tool to investigate the involvement of these anatomical regions in surgical outcomes and in human memory. For this purpose, we implemented an MRI volumetric analysis, already applied to healthy population or epileptic patient before surgery, to quantify the volume of the hippocampus, the temporopolar cortex and the regions of the parahippocampal gyrus (perirhinal, entorhinal and parahippocampal cortices) spared after unilateral MTL resection carried out to treat medically uncontrolled temporal lobe epilepsy (TLE). Based on the locations of remaining anatomical landmarks, we quantified the volume of these regions in 24 patients after MTL resection and in 16 control participants. Our results show that (1) mean volumes of these regions contralateral to the epileptic focus were similar to those of normal subjects, (2) volumetric measures obtained from the resected side were much smaller than those from the non-resected side or from normal values and (3) the extent of MTL resection was comparable in right or left MTL surgery. Individual analysis of patients showed that the parahippocampal cortex, as opposed to the other regions, was not systematically removed across patients. As a post-operative MRI-based method, it therefore proves valuable to assess group data as well as to explore differences between individual patients.
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Affiliation(s)
- M Noulhiane
- Unité de Neurosciences Cognitives et Imagerie Cérébrale, LENA-CNRS UPR 640, Paris, France.
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Gavrilovici C, D'Alfonso S, Dann M, Poulter MO. Kindling-induced alterations in GABAAreceptor-mediated inhibition and neurosteroid activity in the rat piriform cortex. Eur J Neurosci 2006; 24:1373-84. [PMID: 16987222 DOI: 10.1111/j.1460-9568.2006.05012.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The piriform cortex makes strong interconnections with limbic structures (amygdala, entorhinal cortex and hippocampus) that are involved in memory processing. These connections have also been implicated in the development of temporal lobe epilepsy. However, little is known about how neurones in this region may change during seizure genesis. Here we tested the hypothesis that in the kindling model of temporal lobe epilepsy GABAA receptor-mediated inhibition is altered in the piriform cortex. To do this we performed whole-cell patch-clamp recordings in piriform cortex brain slices obtained from non-kindled and amygdala-kindled adult rats. We found that kindling coincided with an increase in the amplitude and duration of miniature inhibitory post-synaptic currents (mIPSCs) recorded from non-pyramidal neurones, whereas the mIPSCs occurring on pyramidal (excitatory) cells did not change. Non-stationary noise analysis of mIPSCs occurring on the non-pyramidal neurones showed that inferred unitary conductance of synaptic channels were the same before and after kindling, implying that the channel number increased significantly. Immunocytochemical analysis of the inhibitory innervation showed that it was also unaltered by seizure induction. We also found that the effect of the positive modulator tetrahydrodeoxycorticosterone was reduced on the pyramidal neurones after kindling. In contrast, the potentiating effects of tetrahydrodeoxycorticosterone on non-pyramidal cells were about the same after kindling as in control (sham) rats. These data indicate that amygdala kindling causes a shift in the inhibition 'balance' between the pyramidal and non-pyramidal cells, perhaps leading to the disinhibition of pyramidal cells.
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Affiliation(s)
- Cezar Gavrilovici
- Neuroscience Research Institute, Department of Psychology, Carleton University, Ottawa, Ontario, Canada
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Peña F, Alavez-Pérez N. Epileptiform activity induced by pharmacologic reduction of M-current in the developing hippocampus in vitro. Epilepsia 2006; 47:47-54. [PMID: 16417531 DOI: 10.1111/j.1528-1167.2006.00369.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
PURPOSE Benign familial neonatal convulsions (BFNCs), an inheritable epilepsy that occurs in neonates but not in adults, is caused by hypofunctional mutations in genes codifying for the M-type K+ current. In an attempt to develop an in vitro model of this disease, we tested whether blocking M-current with linopirdine induces epileptiform activity in brain slices from animals of different ages. METHODS Horizontal hippocampus-entorhinal cortex slices were obtained from neonatal (1-2 weeks after birth) and adult (8-9 weeks after birth) rats. Extracellular field recordings of the CA1 region were performed. After recording control conditions, linopirdine was added to the bath, and field activity was recorded continuously for 3 h. 4-Aminopyridine, a drug commonly used to induce epileptiform activity in vitro, was used as a control for our experimental conditions. RESULTS Bath perfusion of linopirdine induced epileptiform activity only in slices from neonatal rats. Epileptiform activity consisted of interictal-like and ictal-like activity. In slices from adult rats, linopirdine induced erratic interictal-like activity. In contrast, 4-aminopyridine was able to induce epileptiform activity in slices from both neonatal and adult rats. CONCLUSIONS We demonstrated that blockade of M-current in vitro produces epileptiform activity with a developmental pattern similar to that observed in BNFCs. This could be an in vitro model that can be used to study the cellular mechanisms of epileptogenesis and the developmental features of BFNCs, as well as to develop some therapeutic strategies.
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Affiliation(s)
- Fernando Peña
- Departamento de Farmacobiología, Cinvestav-Coapa, México City, México.
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Labyt E, Uva L, De Curtis M, Wendling F. Realistic modeling of entorhinal cortex field potentials and interpretation of epileptic activity in the guinea pig isolated brain preparation. J Neurophysiol 2006; 96:363-77. [PMID: 16598061 PMCID: PMC2486351 DOI: 10.1152/jn.01342.2005] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mechanisms underlying epileptic activities recorded from entorhinal cortex (EC) were studied through a computational model based on review of cytoarchitectonic and neurobiological data about this structure. The purpose of this study is to describe and use this model to interpret epileptiform discharge patterns recorded in an experimental model of ictogenesis (guinea pig isolated brain perfused with bicuculline). A macroscopic modeling approach representing synaptic interactions between cells subpopulations in the EC was chosen for its adequacy to mimic field potentials reflecting overall dynamics rising from interconnected cells populations. Therefore intrinsic properties of neurons were not included in the modeling design. Model parameters were adjusted from an identification procedure based on quantitative comparison between real and simulated signals. For both EC deep and superficial layers, results show that the model generates very realistic signals regarding temporal dynamics, spectral features, and cross-correlation values. These simulations allowed us to infer information about the evolution of synaptic transmission between principal cell and interneuronal populations and about connectivity between deep and superficial layers during the transition from background to ictal activity. In the model, this transition was obtained for increased excitation in deep versus superficial layers. Transitions between epileptiform activities [interictal spikes, fast onset activity (25 Hz), ictal bursting activity] were explained by changes of parameters mainly related to GABAergic interactions. Notably, the model predicted an important role of GABAa,fast- and GABAb-receptor-mediated inhibition in the generation of ictal fast onset and burst activities, respectively. These findings are discussed with respect to experimental data.
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Affiliation(s)
- Etienne Labyt
- LTSI, Laboratoire Traitement du Signal et de l'Image
INSERM : U642Université Rennes ICampus de Beaulieu,
263 Avenue du Général Leclerc - CS 74205 - 35042 Rennes Cedex,FR
| | - Laura Uva
- Department Experimental Neurophysiology
Istituto Nazionale Neurologico C. Bestavia Celoria 11
20133 Milan,IT
| | - Marco De Curtis
- Department Experimental Neurophysiology
Istituto Nazionale Neurologico C. Bestavia Celoria 11
20133 Milan,IT
| | - Fabrice Wendling
- LTSI, Laboratoire Traitement du Signal et de l'Image
INSERM : U642Université Rennes ICampus de Beaulieu,
263 Avenue du Général Leclerc - CS 74205 - 35042 Rennes Cedex,FR
- * Correspondence should be adressed to: Fabrice Wendling
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Abstract
Male mice (Mus musculus) from 15 standard inbred strains were exposed to a nearly constant concentration of ethanol (EtOH) vapor for 72 hr, averaging 1.59 +/- 0.03 mg EtOH/mL blood at withdrawal. EtOH- and air-exposed groups were tested hourly for handling-induced convulsions for 10 hr and at Hours 24 and 25. Strains differed markedly in the severity of withdrawal (after subtraction of control values), and by design these differences were independent of strain differences in EtOH metabolism. Correlation of strain mean withdrawal severity with other responses to EtOH supported previously reported genetic relationships of high EtOH withdrawal with low drinking, high conditioned taste aversion, low tolerance to EtOH-induced hypothermia, and high stimulated activity after low-dose EtOH. Also supported were the positive genetic correlations among EtOH, barbiturate, and benzodiazepine withdrawal. Sensitivity of naive mice to several chemical convulsant-induced seizures was also correlated with EtOH withdrawal.
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Affiliation(s)
- Pamela Metten
- Portland Alcohol Research Center, Veterans Affairs Medical Center, Portland, OR 97239, USA.
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Jamali S, Bartolomei F, Robaglia-Schlupp A, Massacrier A, Peragut JC, Régis J, Dufour H, Ravid R, Roll P, Pereira S, Royer B, Roeckel-Trevisiol N, Fontaine M, Guye M, Boucraut J, Chauvel P, Cau P, Szepetowski P. Large-scale expression study of human mesial temporal lobe epilepsy: evidence for dysregulation of the neurotransmission and complement systems in the entorhinal cortex. ACTA ACUST UNITED AC 2006; 129:625-41. [PMID: 16399808 DOI: 10.1093/brain/awl001] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Human mesial temporal lobe epilepsies (MTLE) are the most frequent form of partial epilepsies and display frequent pharmacoresistance. The molecular alterations underlying human MTLE remain poorly understood. A two-step transcriptional analysis consisting in cDNA microarray experiments followed by quantitative RT-PCR validations was performed. Because the entorhinal cortex (EC) plays an important role in the pathophysiology of the MTLE and usually discloses no detectable or little cell loss, resected EC and each corresponding lateral temporal neocortex (LTC) of MTLE patients were used as the source of disease-associated and control RNAs, respectively. Six genes encoding (i) a serotonin receptor (HTR2A) and a neuropeptide Y receptor type 1 (NPY1R), (ii) a protein (FHL2) associating with the KCNE1 (minK) potassium channel subunit and with presenilin-2 and (iii) three immune system-related proteins (C3, HLA-DR-gamma and CD99), were found consistently downregulated or upregulated in the EC of MTLE patients as compared with non-epileptic autopsy controls. Quantitative western blot analyses confirmed decreased expression of NPY1R in all eight MTLE patients tested. Immunohistochemistry experiments revealed the existence of a perivascular infiltration of C3 positive leucocytes and/or detected membrane attack complexes on a subset of neurons, within the EC of nine out of eleven MTLE patients. To summarize, a large-scale microarray expression study on the EC of MTLE patients led to the identification of six candidate genes for human MTLE pathophysiology. Altered expression of NPY1R and C3 was also demonstrated at the protein level. Overall, our data indicate that local dysregulation of the neurotransmission and complement systems in the EC is a frequent event in human MTLE.
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Affiliation(s)
- Sarah Jamali
- INSERM UMR 491, Université de la Méditerranée, France
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Uva L, Librizzi L, Wendling F, de Curtis M. Propagation Dynamics of Epileptiform Activity Acutely Induced by Bicuculline in the Hippocampal-Parahippocampal Region of the Isolated Guinea Pig Brain. Epilepsia 2005; 46:1914-25. [PMID: 16393157 DOI: 10.1111/j.1528-1167.2005.00342.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE Aim of the study is to investigate the involvement of parahippocampal subregions in the generation and in the propagation of focal epileptiform discharges in an acute model of seizure generation in the temporal lobe induced by arterial application of bicuculline in the in vitro isolated guinea pig brain preparation. METHODS Electrophysiological recordings were simultaneously performed with single electrodes and multichannel silicon probes in the entorhinal, perirhinal, and piriform cortices and in the area CA1 of the hippocampus of the in vitro isolated guinea pig brain. Interictal and ictal epileptiform discharges restricted to the temporal region were induced by a brief (3-5 min) arterial perfusion of the GABA(A) receptor antagonist, bicuculline methiodide (50 microM). Current source density analysis of laminar field profiles performed with the silicon probes was carried out at different sites to establish network interactions responsible for the generation of epileptiform potentials. Nonlinear regression analysis was conducted on extracellular recordings during ictal onset in order to quantify the degree of interaction between fast activities generated at different sites, as well as time delays. RESULTS Experiments were performed in 31 isolated guinea pig brains. Bicuculline-induced interictal and ictal epileptiform activities that showed variability of spatial propagation and time course in the olfactory-temporal region. The most commonly observed pattern (n = 23) was characterized by the initial appearance of interictal spikes (ISs) in the piriform cortex (PC), which propagated to the lateral entorhinal region. Independent and asynchronous preictal spikes originated in the entorhinal cortex (EC)/hippocampus and progressed into ictal fast discharges (around 25 Hz) restricted to the entorhinal/hippocampal region. The local generation of fast activity was verified and confirmed both by CSD and phase shift analysis performed on laminar profiles. Fast activity was followed by synchronous afterdischarges that propagated to the perirhinal cortex (PRC) (but not to the PC). Within 1-9 min, the ictal discharge ceased and a postictal period of depression occurred, after which periodic ISs in the PC resumed. Unlike preictal ISs, postictal ISs propagated to the PRC. CONCLUSIONS Several studies proposed that reciprocal connections between the entorhinal and the PRC are under a very efficient inhibitory control (1). We report that ISs determined by acute bicuculline treatment in the isolated guinea pig brain progress from the PC to the hippocampus/EC just before ictal onset. Ictal discharges are characterized by a peculiar pattern of fast activity that originates from the entorhinal/hippocampal region and only secondarily propagates to the PRC. Postictal propagation of ISs to the PRC occurred exclusively when an ictal discharge was generated in the hippocampal/entorhinal region. The results suggest that reiteration of ictal events may promote changes in propagation pattern of epileptiform discharges that could act as trigger elements in the development of temporal lobe epilepsy.
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Affiliation(s)
- Laura Uva
- Department of Experimental Neurophysiology, Istituto Nazionale Neurologico, via Celoria 11, 20133 Milan, Italy
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Kopniczky Z, Dobó E, Borbély S, Világi I, Détári L, Krisztin-Péva B, Bagosi A, Molnár E, Mihály A. Lateral entorhinal cortex lesions rearrange afferents, glutamate receptors, increase seizure latency and suppress seizure-induced c-fos expression in the hippocampus of adult rat. J Neurochem 2005; 95:111-24. [PMID: 16181416 DOI: 10.1111/j.1471-4159.2005.03347.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The entorhinal cortex (EC) provides the predominant excitatory drive to the hippocampal CA1 and subicular neurones in chronic epilepsy. Here we analysed the effects of one-sided lateral EC (LEC) and temporoammonic (alvear) path lesion on the development and properties of 4-aminopyridine-induced seizures. Electroencephalography (EEG) analysis of freely moving rats identified that the lesion increased the latency of the hippocampal seizure significantly and decreased the number of brief convulsions. Seizure-induced neuronal c-fos expression was reduced in every hippocampal area following LEC lesion. Immunocytochemical analysis 40 days after the ablation of the LEC identified sprouting of cholinergic and calretinin-containing axons into the dentate molecular layer. Region and subunit specific changes in the expression of ionotropic glutamate receptors (iGluRs) were identified. Although the total amount of AMPA receptor subunits remained unchanged, GluR1(flop) displayed a significant decrease in the CA1 region. An increase in NR1 and NR2B N-methyl-d-aspartate (NMDA) receptor subunits and KA-2 kainate receptor subunit was identified in the deafferented layers of the hippocampus. These results further emphasize the importance of the lateral entorhinal area in the spread and regulation of hippocampal seizures and highlight the potential role of the rewiring of afferents and rearrangement of iGluRs in the dentate gyrus in hippocampal convulsive activity.
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Affiliation(s)
- Zsolt Kopniczky
- Department of Neurosurgery, Faculty of Medicine, University of Szeged, Szeged, Hungary
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de Lanerolle NC, Lee TS. New facets of the neuropathology and molecular profile of human temporal lobe epilepsy. Epilepsy Behav 2005; 7:190-203. [PMID: 16098816 DOI: 10.1016/j.yebeh.2005.06.003] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2005] [Accepted: 06/01/2005] [Indexed: 11/27/2022]
Abstract
This review summarizes the salient features of the anatomical and molecular neuropathology of the hippocampus from patients with intractable temporal lobe epilepsy (TLE). It argues that sclerotic hippocampus is essential for seizure expression and that sclerosis is not a consequence of seizures, but is related to the epileptogenicity of the seizure focus. While neurons in sclerotic hippocampus may contribute to hippocampal hyperexcitability, this role is perhaps less important than that of the astrocytes. The astrocytes in sclerotic hippocampus may directly influence excitability through altered water homeostasis and K+ buffering by redistribution of AQP4 transporters on their plasma membrane. It is proposed that they contribute to a high extracellular glutamate level through reduced glutamine synthetase, and activation through pro-inflammatory factors that release chemokines and cytokines, which enhance calcium-dependent glutamate release. Such a focal pool of glutamate may diffuse to surrounding neuron-rich areas to generate seizure activity in TLE.
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Affiliation(s)
- Nihal C de Lanerolle
- Department of Neurosurgery, Yale University School of Medicine, New Haven, CT 06520, USA.
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Weissinger F, Buchheim K, Siegmund H, Meierkord H. Seizure spread through the life cycle: optical imaging in combined brain slices from immature, adult, and senile rats in vitro. Neurobiol Dis 2005; 19:84-95. [PMID: 15837564 DOI: 10.1016/j.nbd.2004.11.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2004] [Revised: 11/15/2004] [Accepted: 11/18/2004] [Indexed: 11/19/2022] Open
Abstract
The semiology of epileptic seizures changes during the lifetime. Hence, it can be assumed that age-related changes in brain plasticity influence the patterns of seizure onset, spread and propagation velocity. We employed the 4-aminopyridine model of epilepsy to study seizure-like events in vitro. Combined entorhinal cortex-hippocampus brain slices from juvenile (10-13 days), adult (2-3 months), and senile (24-27 months) rats were examined using electrophysiological recordings and imaging of intrinsic optical signals. In the juvenile group, seizure onset was multifocal in all slice regions including the hippocampus. Onset in adult animals was confined to the entorhinal cortex and to neocortical regions. In slices from senile animals, there was a preponderance of seizure onsets in the neocortex. Spread patterns were highly variable in the juvenile group and became gradually more monomorph with increasing age. Propagation velocities were highest in the adult group, with maximum values of 1.51 +/- 0.68 mm/s. In the juvenile group, they amounted to 0.97 +/- 0.39 mm/s, and to 1.18 +/- 0.42 mm/s in senile slices. The results of this study indicate that age-related changes in brain plasticity profoundly affect spread patterns, which may contribute to the clinically observed changes in seizure semiology during early childhood, adulthood and senescence.
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Affiliation(s)
- Florian Weissinger
- Department of Neurology, Charité--Universitary Medicine Berlin, Humboldt-University Berlin, Schumannstr. 20/21, D-10117 Berlin, Germany.
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