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Li W, Jiang Y, Li X, Huang H, Lei D, Li J, Zhang H, Yao D, Luo C, Gong Q, Zhou D, An D. More extensive structural damage in temporal lobe epilepsy with hippocampal sclerosis type 1. Seizure 2023; 111:130-137. [PMID: 37633152 DOI: 10.1016/j.seizure.2023.08.003] [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: 03/23/2023] [Revised: 08/04/2023] [Accepted: 08/06/2023] [Indexed: 08/28/2023] Open
Abstract
OBJECTIVE To explore clinical and structural differences between mesial temporal lobe epilepsy (mTLE) patients with different hippocampal sclerosis (HS) subtypes. METHODS High-resolution T1-weighted MRI and diffusion tensor imaging data were obtained in 41 refractory mTLE patients and 52 age- and sex-matched healthy controls. Postoperative histopathological examination confirmed HS type 1 in 30 patients and HS type 2 in eleven patients. Clinical features, postoperative seizure outcomes, hippocampal subfields volumes, fractional anisotropy (FA) values of white matter regions and graph theory parameters were explored and compared between the HS type 1 and HS type 2 groups. RESULTS No significant differences in clinical features and postsurgical seizure outcomes were found between the HS type 1 and type 2 groups. However, the HS type 1 group showed extra atrophy in ipsilateral parasubiculum than healthy controls and more severe atrophy in contralateral hippocampal fissure than the HS type 2 group. More extensive FA decrease were also observed in the HS type 1 group, involving ipsilateral optic radiation, superior fronto-occipital fasciculus, contralateral uncinate fasciculus, tapetum, bilateral hippocampal cingulum, corona radiata, etc. Furthermore, in spite of similar impairments in characteristic path length, global efficiency and local efficiency in two HS groups, the HS type 1 group showed additional decrease of clustering coefficient than healthy controls. CONCLUSIONS HS type 1 and 2 groups had similar clinical characteristics and postoperative seizure outcomes. More widespread neuronal cell loss in the HS type 1 group contributed to more extensive structural damage and connectivity abnormality. These results shed new light on the imaging correlates of different HS pathology.
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Affiliation(s)
- Wei Li
- Department of Neurology, West China Hospital, Sichuan University, Chengdu, Sichuan, China; National Clinical Research Center for Geriatrics, Department of Gerontology and Geriatrics, West China Hospital, Sichuan University, Chengdu, China
| | - Yuchao Jiang
- The Clinical Hospital of Chengdu Brain Science Institute, MOE Key Lab for Neuroinformation, Center for Information in Medicine, School of life Science and technology, University of Electronic Science and Technology of China, Chengdu, Sichuan, China
| | - Xiuli Li
- Huaxi MR Research Center, Department of Radiology, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Huan Huang
- The Clinical Hospital of Chengdu Brain Science Institute, MOE Key Lab for Neuroinformation, Center for Information in Medicine, School of life Science and technology, University of Electronic Science and Technology of China, Chengdu, Sichuan, China
| | - Du Lei
- Huaxi MR Research Center, Department of Radiology, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Jinmei Li
- Department of Neurology, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Heng Zhang
- Department of Neurosurgery, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Dezhong Yao
- The Clinical Hospital of Chengdu Brain Science Institute, MOE Key Lab for Neuroinformation, Center for Information in Medicine, School of life Science and technology, University of Electronic Science and Technology of China, Chengdu, Sichuan, China
| | - Cheng Luo
- The Clinical Hospital of Chengdu Brain Science Institute, MOE Key Lab for Neuroinformation, Center for Information in Medicine, School of life Science and technology, University of Electronic Science and Technology of China, Chengdu, Sichuan, China
| | - Qiyong Gong
- Huaxi MR Research Center, Department of Radiology, West China Hospital, Sichuan University, Chengdu, Sichuan, China.
| | - Dong Zhou
- Department of Neurology, West China Hospital, Sichuan University, Chengdu, Sichuan, China.
| | - Dongmei An
- Department of Neurology, West China Hospital, Sichuan University, Chengdu, Sichuan, China.
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Avoli M, Chen LY, Di Cristo G, Librizzi L, Scalmani P, Shiri Z, Uva L, de Curtis M, Lévesque M. Ligand-gated mechanisms leading to ictogenesis in focal epileptic disorders. Neurobiol Dis 2023; 180:106097. [PMID: 36967064 DOI: 10.1016/j.nbd.2023.106097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 03/14/2023] [Accepted: 03/22/2023] [Indexed: 04/03/2023] Open
Abstract
We review here the neuronal mechanisms that cause seizures in focal epileptic disorders and, specifically, those involving limbic structures that are known to be implicated in human mesial temporal lobe epilepsy. In both epileptic patients and animal models, the initiation of focal seizures - which are most often characterized by a low-voltage fast onset EEG pattern - is presumably dependent on the synchronous firing of GABA-releasing interneurons that, by activating post-synaptic GABAA receptors, cause large increases in extracellular [K+] through the activation of the co-transporter KCC2. A similar mechanism may contribute to seizure maintenance; accordingly, inhibiting KCC2 activity transforms seizure activity into a continuous pattern of short-lasting epileptiform discharges. It has also been found that interactions between different areas of the limbic system modulate seizure occurrence by controlling extracellular [K+] homeostasis. In line with this view, low-frequency electrical or optogenetic activation of limbic networks restrain seizure generation, an effect that may also involve the activation of GABAB receptors and activity-dependent changes in epileptiform synchronization. Overall, these findings highlight the paradoxical role of GABAA signaling in both focal seizure generation and maintenance, emphasize the efficacy of low-frequency activation in abating seizures, and provide experimental evidence explaining the poor efficacy of antiepileptic drugs designed to augment GABAergic function in controlling seizures in focal epileptic disorders.
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Affiliation(s)
- Massimo Avoli
- Montreal Neurological Institute-Hospital, Departments of Neurology, Canada; Neurology & Neurosurgery and of Physiology, McGill University, Montreal H3A 2B4, Que, Canada.
| | - Li-Yuan Chen
- Montreal Neurological Institute-Hospital, Departments of Neurology, Canada
| | - Graziella Di Cristo
- Neurosciences Department, Université de Montréal, Montréal, Québec H3T 1N8, Canada; CHU Sainte-Justine Research Center, Montréal, Québec H3T 1C5, Canada
| | - Laura Librizzi
- Epilepsy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Paolo Scalmani
- Epilepsy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Zahra Shiri
- Montreal Neurological Institute-Hospital, Departments of Neurology, Canada
| | - Laura Uva
- Epilepsy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Marco de Curtis
- Epilepsy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Maxime Lévesque
- Montreal Neurological Institute-Hospital, Departments of Neurology, Canada
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3
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Scalmani P, Paterra R, Mantegazza M, Avoli M, de Curtis M. Involvement of GABAergic Interneuron Subtypes in 4-Aminopyridine-Induced Seizure-Like Events in Mouse Entorhinal Cortex in Vitro. J Neurosci 2023; 43:1987-2001. [PMID: 36810229 PMCID: PMC10027059 DOI: 10.1523/jneurosci.1190-22.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 12/30/2022] [Accepted: 01/05/2023] [Indexed: 02/23/2023] Open
Abstract
Single-unit recordings performed in temporal lobe epilepsy patients and in models of temporal lobe seizures have shown that interneurons are active at focal seizure onset. We performed simultaneous patch-clamp and field potential recordings in entorhinal cortex slices of GAD65 and GAD67 C57BL/6J male mice that express green fluorescent protein in GABAergic neurons to analyze the activity of specific interneuron (IN) subpopulations during acute seizure-like events (SLEs) induced by 4-aminopyridine (4-AP; 100 μm). IN subtypes were identified as parvalbuminergic (INPV, n = 17), cholecystokinergic (INCCK), n = 13], and somatostatinergic (INSOM, n = 15), according to neurophysiological features and single-cell digital PCR. INPV and INCCK discharged at the start of 4-AP-induced SLEs characterized by either low-voltage fast or hyper-synchronous onset pattern. In both SLE onset types, INSOM fired earliest before SLEs, followed by INPV and INCCK discharges. Pyramidal neurons became active with variable delays after SLE onset. Depolarizing block was observed in ∼50% of cells in each INs subgroup, and it was longer in IN (∼4 s) than in pyramidal neurons (<1 s). As SLE evolved, all IN subtypes generated action potential bursts synchronous with the field potential events leading to SLE termination. High-frequency firing throughout the SLE occurred in one-third of INPV and INSOM We conclude that entorhinal cortex INs are very active at the onset and during the progression of SLEs induced by 4-AP. These results support earlier in vivo and in vivo evidence and suggest that INs have a preferential role in focal seizure initiation and development.SIGNIFICANCE STATEMENT Focal seizures are believed to result from enhanced excitation. Nevertheless, we and others demonstrated that cortical GABAergic networks may initiate focal seizures. Here, we analyzed for the first time the role of different IN subtypes in seizures generated by 4-aminopyridine in the mouse entorhinal cortex slices. We found that in this in vitro focal seizure model, all IN types contribute to seizure initiation and that INs precede firing of principal cells. This evidence is in agreement with the active role of GABAergic networks in seizure generation.
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Affiliation(s)
| | - Rosina Paterra
- Neuro-Oncology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano 20133, Italy
| | - Massimo Mantegazza
- Université Côte d'Azur, 06560 Valbonne-Sophia Antipolis, France
- Institute of Molecular and Cellular Pharmacology, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7275, Laboratoire d'Excellence/Canaux Ioniques d'Intérêt Thérapeutique, 06650 Valbonne-Sophia Antipolis, France
- Institut National de la Santé et de la Recherche Médicale, 06650 Valbonne-Sophia Antipolis, France
| | - Massimo Avoli
- Montreal Neurological Institute-Hospital, McGill University, Montreal, Quebec H3A 2B4, Canada
- Departments of Neurology and Neurosurgery and Physiology, McGill University, Montreal, Quebec H3A 2B4, Canada
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4
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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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5
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Righes Marafiga J, Vendramin Pasquetti M, Calcagnotto ME. In vitro Oscillation Patterns Throughout the Hippocampal Formation in a Rodent Model of Epilepsy. Neuroscience 2021; 479:1-21. [PMID: 34710537 DOI: 10.1016/j.neuroscience.2021.10.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 10/14/2021] [Accepted: 10/18/2021] [Indexed: 11/29/2022]
Abstract
Specific oscillatory patterns are considered biomarkers of pathological neuronal network in brain diseases, such as epilepsy. However, the dynamics of underlying oscillations during the epileptogenesis throughout the hippocampal formation in the temporal lobe epilepsy is not clear. Here, we characterized in vitro oscillatory patterns within the hippocampal formation of epileptic rats, under 4-aminopyridine (4-AP)-induced hyperexcitability and during the spontaneous network activity, at two periods of epileptogenesis. First, at the beginning of epileptic chronic phase, 30 days post-pilocarpine-induced Status Epilepticus (SE). Second, at the established epilepsy, 60 days post-SE. The 4-AP-bathed slices from epileptic rats had increased susceptibility to ictogenesis in CA1 at 30 days post-SE, and in entorhinal cortex and dentate gyrus at 60 days post-SE. Higher power and phase coherence were detected mainly for gamma and/or high frequency oscillations (HFOs), in a region- and stage-specific manner. Interestingly, under spontaneous network activity, even without 4-AP-induced hyperexcitability, slices from epileptic animals already exhibited higher power of gamma and HFOs in different areas of hippocampal formation at both periods of epileptogenesis, and higher phase coherence in fast ripples at 60 days post-SE. These findings reinforce the critical role of gamma and HFOs in each one of the hippocampal formation areas during ongoing neuropathological processes, tuning the neuronal network to epilepsy.
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Affiliation(s)
- Joseane Righes Marafiga
- Neurophysiology and Neurochemistry of Neuronal Excitability and Synaptic Plasticity Laboratory (NNNESP Lab.), Department of Biochemistry, ICBS, Universidade Federal do Rio Grande do Sul, Porto Alegre 90035-003, RS, Brazil; Graduate Program in Biological Science: Biochemistry, Universidade Federal do Rio Grande do Sul, Porto Alegre 90035-003, RS, Brazil
| | - Mayara Vendramin Pasquetti
- Neurophysiology and Neurochemistry of Neuronal Excitability and Synaptic Plasticity Laboratory (NNNESP Lab.), Department of Biochemistry, ICBS, Universidade Federal do Rio Grande do Sul, Porto Alegre 90035-003, RS, Brazil; Graduate Program in Biological Science: Biochemistry, Universidade Federal do Rio Grande do Sul, Porto Alegre 90035-003, RS, Brazil
| | - Maria Elisa Calcagnotto
- Neurophysiology and Neurochemistry of Neuronal Excitability and Synaptic Plasticity Laboratory (NNNESP Lab.), Department of Biochemistry, ICBS, Universidade Federal do Rio Grande do Sul, Porto Alegre 90035-003, RS, Brazil; Graduate Program in Biological Science: Biochemistry, Universidade Federal do Rio Grande do Sul, Porto Alegre 90035-003, RS, Brazil.
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6
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Uva L, Aracri P, Forcaia G, de Curtis M. Mapping region-specific seizure-like patterns in the in vitro isolated guinea pig brain. Exp Neurol 2021; 342:113727. [PMID: 33930392 DOI: 10.1016/j.expneurol.2021.113727] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 04/09/2021] [Accepted: 04/22/2021] [Indexed: 10/21/2022]
Abstract
Specific neurophysiological seizure patterns in patients with focal epilepsy depend on cerebral location and the underlying neuropathology. Location-specific patterns have been also reported in experimental models. Two focal seizure patterns, named p-type and l-type, typical of neocortical and mesial temporal regions were identified in both patients explored with intracerebral EEG and in animal models. These two patterns were recorded in the olfactory regions and in the entorhinal cortex after either 4AP or BMI administration. Here we mapped epileptiform activities in other cortices to verify the existence of specific epileptiform patterns. Field potentials were simultaneously recorded at multiple locations in olfactory, limbic and neocortical regions of the isolated guinea pig brain after arterial administration of either 4AP or BMI. Most neocortical areas did not generate new distinctive focal seizure-like event (SLE), beside the p-type and l-type patterns. Spiking activity was typically recorded after BMI in all new analyzed regions, whereas SLEs were commonly observed during 4AP perfusion. We confirmed the presence of reproducible region-specific epileptiform patterns in all explored cortical areas and demonstrated that strongly inter-connected areas generate similar SLEs. Our study suggests that p- and l-type SLE represent the most common focal seizure patterns during acute manipulations with pro-epileptic compounds.
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Affiliation(s)
- Laura Uva
- Epilepsy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, via Amadeo 42, 20133 Milano, Italy.
| | - Patrizia Aracri
- Epilepsy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, via Amadeo 42, 20133 Milano, Italy
| | - Greta Forcaia
- School of Medicine and Surgery, University of Milano-Bicocca, via Cadore 48, 20900 Monza, MB, Italy.
| | - Marco de Curtis
- Epilepsy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, via Amadeo 42, 20133 Milano, Italy.
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7
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Activity- and pH-dependent adenosine shifts at the end of a focal seizure in the entorhinal cortex. Epilepsy Res 2020; 165:106401. [PMID: 32599416 DOI: 10.1016/j.eplepsyres.2020.106401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 06/05/2020] [Accepted: 06/14/2020] [Indexed: 11/24/2022]
Abstract
Adenosine (ADO) is an endogenous modulator of neuronal excitability, with anticonvulsant and neuroprotective effects. It has been proposed that the activity-dependent release of ADO promoted by the extracellular acidification occurring during seizures contributes to seizure termination. To verify this hypothesis, we recorded field potentials, pH and ADO changes measured with enzymatic biosensors during acute focal seizures in the medial entorhinal cortex (mEC) of the isolated guinea-pig brain maintained in vitro. The effect of ADO on seizure-like events (SLEs) induced by GABAa receptor antagonism with bicuculline methiodide (BMI; 50 μM) was assessed by arterial applications of 1 mM ADO. ADO either reduced or prevented epileptiform activity. The A1 receptor antagonist DPCPX (100-500 μM) prolonged BMI-induced seizures and was able to precipitate SLEs in the absence of proconvulsant. Simultaneous recordings of brain activity, extracellular ADO and pH shifts demonstrated that ADO decreases at the onset and progressively rises toward the end of SLEs induced by either BMI or 4-aminopyridine (4AP; 50 μM), reaching maximal values 1-5 min after SLE termination. ADO changes were preceded by a SLE-dependent extracellular acid shift. Both pH acidification and ADO changes were abolished by 22 mM HEPES in the arterial perfusate. In these conditions, SLE duration was prolonged. Our data confirm that ADO plays a role in regulating brain excitability. Its increase depends on seizure-induced acid pH shift and it is maximal after the end of the SLE. These findings strongly suggest that ADO contributes to termination of focal seizures and to the establishment of the postictal depression.
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8
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de Curtis M, Uva L, Lévesque M, Biella G, Avoli M. Piriform cortex ictogenicity in vitro. Exp Neurol 2019; 321:113014. [DOI: 10.1016/j.expneurol.2019.113014] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 05/07/2019] [Accepted: 07/15/2019] [Indexed: 02/05/2023]
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9
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de Curtis M, Librizzi L, Uva L, Gnatkovsky V. GABAA receptor-mediated networks during focal seizure onset and progression in vitro. Neurobiol Dis 2019; 125:190-197. [DOI: 10.1016/j.nbd.2019.02.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 01/08/2019] [Accepted: 02/07/2019] [Indexed: 02/02/2023] Open
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10
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Stereotypical patterns of epileptiform calcium signal in hippocampal CA1, CA3, dentate gyrus and entorhinal cortex in freely moving mice. Sci Rep 2019; 9:4518. [PMID: 30872744 PMCID: PMC6418290 DOI: 10.1038/s41598-019-41241-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 03/04/2019] [Indexed: 11/08/2022] Open
Abstract
Epilepsy is a multi-etiological brain dysfunction syndrome. Hippocampal neuronal damage induced by seizures may be one of the causes leading to cognitive impairment, but the underlying mechanism remains to be further elucidated. The kainic acid (KA) model of temporal lobe epilepsy is widely used in understanding of the epileptogenesis. Fiber photometry is a signal detection technology suitable for recording calcium activity of neurons in the deep brain of freely moving animal. Here, we used the optical fiber-based method to monitor the real-time neuronal population activities of freely moving mice after subcutaneous injection of KA. We observed that KA administration led to one to three kinds of stereotypical patterns of epileptiform calcium activity in CA1, CA3, and dentate gyrus (DG) of the hippocampus, as well as the entorhinal cortex (EC). There were three kinds of waves in the hippocampal CA1, which we named wave 1, wave 2 and slow flash. Wave 1 and wave 2 appeared in both the CA3 and DG regions, but the EC only showed wave 1. In these epileptiform calcium signals, we observed a high amplitude and long duration calcium wave as a part of wave 2, which resembled cortical spreading depression (CSD) and always appeared at or after the end of seizure. Because the same characteristic of epileptiform calcium signal appeared in different brain regions, calcium signal may not exist with region specificity, but may exhibit a cell type specific manner. Thus, our work provides a support for the pathogenesis of epilepsy and epileptiform signal transmission research.
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11
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Gnatkovsky V, Pelliccia V, de Curtis M, Tassi L. Two main focal seizure patterns revealed by intracerebral electroencephalographic biomarker analysis. Epilepsia 2018; 60:96-106. [DOI: 10.1111/epi.14610] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 10/08/2018] [Accepted: 10/29/2018] [Indexed: 02/06/2023]
Affiliation(s)
- Vadym Gnatkovsky
- Epilepsy Unit; Institute of Cure, Recovery, and Scientific Research (IRCCS) Foundation Carlo Besta Neurological Institute; Milan Italy
| | | | - Marco de Curtis
- Epilepsy Unit; Institute of Cure, Recovery, and Scientific Research (IRCCS) Foundation Carlo Besta Neurological Institute; Milan Italy
| | - Laura Tassi
- Claudio Munari Epilepsy Surgery Center; Niguarda Hospital; Milan Italy
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12
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Janz P, Hauser P, Heining K, Nestel S, Kirsch M, Egert U, Haas CA. Position- and Time-Dependent Arc Expression Links Neuronal Activity to Synaptic Plasticity During Epileptogenesis. Front Cell Neurosci 2018; 12:244. [PMID: 30154698 PMCID: PMC6102356 DOI: 10.3389/fncel.2018.00244] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Accepted: 07/18/2018] [Indexed: 12/14/2022] Open
Abstract
In mesial temporal lobe epilepsy (mTLE) an initial precipitating injury can trigger aberrant wiring of neuronal circuits causing seizure activity. While circuit reorganization is known to be largely activity-dependent, the interactions between neuronal activity and synaptic plasticity during the development of mTLE remain poorly understood. Therefore, the present study aimed at delineating the spatiotemporal relationship between epileptic activity, activity-dependent gene expression and synaptic plasticity during kainic acid-induced epileptogenesis in mice. We show that during epileptogenesis the sclerotic hippocampus differed from non-sclerotic regions by displaying a consistently lower power of paroxysmal discharges. However, the power of these discharges steadily increased during epileptogenesis. This increase was paralleled by the upregulation of the activity-related cytoskeleton protein (Arc) gene expression in dentate granule cells (DGCs) of the sclerotic hippocampus. Importantly, we found that Arc mRNA-upregulating DGCs exhibited increased spine densities and spine sizes, but at the same time decreased AMPA-type glutamate receptor (AMPAR) densities. Finally, we show that in vivo optogenetic stimulation of DGC synapses evoked robust seizure activity in epileptic mice, but failed to induce dendritic translocation of Arc mRNA as under healthy conditions, supporting the theory of a breakdown of the dentate gate in mTLE. We conclude that during epileptogenesis epileptic activity emerges early and persists in the whole hippocampus, however, only the sclerotic part shows modulation of discharge amplitudes accompanied by plasticity of DGCs. In this context, we identified Arc as a putative mediator between seizure activity and synaptic plasticity.
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Affiliation(s)
- Philipp Janz
- Experimental Epilepsy Research, Department of Neurosurgery, University Medical Center, University of Freiburg, Freiburg, Germany.,Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Pascal Hauser
- Experimental Epilepsy Research, Department of Neurosurgery, University Medical Center, University of Freiburg, Freiburg, Germany.,Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Katharina Heining
- Faculty of Biology, University of Freiburg, Freiburg, Germany.,Laboratory for Biomicrotechnology, Department of Microsystems Engineering, University of Freiburg, Freiburg, Germany.,Bernstein Center Freiburg, University of Freiburg, Freiburg, Germany
| | - Sigrun Nestel
- Institute for Anatomy and Cell Biology, Department of Neuroanatomy, University of Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Matthias Kirsch
- Institute for Anatomy and Cell Biology, Department of Neuroanatomy, University of Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany.,BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Freiburg, Germany
| | - Ulrich Egert
- Laboratory for Biomicrotechnology, Department of Microsystems Engineering, University of Freiburg, Freiburg, Germany.,Bernstein Center Freiburg, University of Freiburg, Freiburg, Germany.,BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Freiburg, Germany
| | - Carola A Haas
- Experimental Epilepsy Research, Department of Neurosurgery, University Medical Center, University of Freiburg, Freiburg, Germany.,Bernstein Center Freiburg, University of Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany.,BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Freiburg, Germany
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13
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Aracri P, de Curtis M, Forcaia G, Uva L. Enhanced thalamo-hippocampal synchronization during focal limbic seizures. Epilepsia 2018; 59:1774-1784. [DOI: 10.1111/epi.14521] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 07/05/2018] [Accepted: 07/05/2018] [Indexed: 01/21/2023]
Affiliation(s)
- Patrizia Aracri
- Epilepsy Unit; Fondazione Istituto Neurologico Carlo Besta; Milano Italy
| | - Marco de Curtis
- Epilepsy Unit; Fondazione Istituto Neurologico Carlo Besta; Milano Italy
| | - Greta Forcaia
- Epilepsy Unit; Fondazione Istituto Neurologico Carlo Besta; Milano Italy
| | - Laura Uva
- Epilepsy Unit; Fondazione Istituto Neurologico Carlo Besta; Milano Italy
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14
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Hébert M, Anfray A, Chevilley A, Martinez de Lizarrondo S, Quenault A, Louessard M, Roussel BD, Obiang P, Save E, Orset C, Maubert E, Vivien D, Agin V. Distant Space Processing is Controlled by tPA-dependent NMDA Receptor Signaling in the Entorhinal Cortex. Cereb Cortex 2018; 27:4783-4796. [PMID: 27613436 DOI: 10.1093/cercor/bhw275] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 08/10/2016] [Indexed: 11/14/2022] Open
Abstract
In humans, spatial cognition and navigation impairments are a frequent situation during physiological and pathological aging, leading to a dramatic deterioration in the quality of life. Despite the discovery of neurons with location-specific activity in rodents, that is, place cells in the hippocampus and later on grid cells in the entorhinal cortex (EC), the molecular mechanisms underlying spatial cognition are still poorly known. Our present data bring together in an unusual combination 2 molecules of primary biological importance: a major neuronal excitatory receptor, N-methyl-D-aspartate receptor (NMDAR), and an extracellular protease, tissue plasminogen activator (tPA), in the control of spatial navigation. By using tPA-deficient mice and a structure-selective pharmacological approach, we demonstrate that the tPA-dependent NMDAR signaling potentiation in the EC plays a key and selective role in the encoding and the subsequent use of distant landmarks during spatial learning. We also demonstrate that this novel function of tPA in the EC is reduced during aging. Overall, these results argue for the concept that encoding of proximal versus distal landmarks is mediated not only by different anatomical pathways but also by different molecular mechanisms, with the tPA-dependent potentiation of NMDAR signaling in the EC that plays an important role.
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Affiliation(s)
- Marie Hébert
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Antoine Anfray
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Arnaud Chevilley
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Sara Martinez de Lizarrondo
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Aurélien Quenault
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Morgane Louessard
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Benoit D Roussel
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Pauline Obiang
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Etienne Save
- Laboratory of Cognitive Neuroscience UMR 7291, Aix-Marseille University, CNRS, 3 Place Victor Hugo, F-13331 Marseille Cedex 3, France
| | - Cyrille Orset
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Eric Maubert
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Denis Vivien
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France.,Biology Department, Clinical Research Department Medical Center, Normandie Université, UNICAEN, 14000 Caen, France
| | - Véronique Agin
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
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15
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Interneuronal Network Activity at the Onset of Seizure-Like Events in Entorhinal Cortex Slices. J Neurosci 2017; 37:10398-10407. [PMID: 28947576 DOI: 10.1523/jneurosci.3906-16.2017] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 07/05/2017] [Accepted: 07/08/2017] [Indexed: 12/19/2022] Open
Abstract
The onset of focal seizures in humans and in different animal models of focal epilepsy correlates with reduction of neuronal firing and enhanced interneuronal network activity. Whether this phenomenon contributes to seizure generation is still unclear. We used the in vitro entorhinal cortex slices bathed in 4-aminopirydine (4-AP) as an experimental paradigm model to evaluate the correlation between interneuronal GABAergic network activity and seizure-like events. Epileptiform discharges were recorded in layer V-VI pyramidal neurons and fast-spiking interneurons in slices from male and female mice and in the isolated female guinea pig brain preparation during perfusion with 4-AP. We observed that 90% of seizure-like events recorded in principal cells were preceded by outward currents coupled with extracellular potassium shifts, abolished by pharmacological blockade of GABAA receptors. Potassium elevations associated to GABAA receptor-mediated population events were confirmed in the entorhinal cortex of the in vitro isolated whole guinea pig brain. Fast-rising and sustained extracellular potassium increases associated to interneuronal network activity consistently preceded the initiation of seizure-like events. We conclude that in the 4-AP seizure model, interneuronal network activity occurs before 4-AP-induced seizures and therefore supports a role of interneuron activity in focal seizure generation.SIGNIFICANCE STATEMENT The paper focuses on the mechanisms of ictogenesis, a topic that requires a step beyond the simplistic view that seizures, and epilepsy, are due to an increase of excitatory network activity. Focal temporal lobe seizures in humans and in several experimental epilepsies likely correlate with a prevalent activation of interneurons. The potassium channel blocker 4-aminopyridine reliably induces seizure-like events in temporal lobe structures. Herein, we show that a majority of seizures in the entorhinal cortex starts with interneuronal network activity accompanied by a fast and sustained increase in extracellular potassium. Our new findings reinforce and add a new piece of evidence to the proposal that limbic seizures can be supported by GABAergic hyperactivity.
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16
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Neumann AR, Raedt R, Steenland HW, Sprengers M, Bzymek K, Navratilova Z, Mesina L, Xie J, Lapointe V, Kloosterman F, Vonck K, Boon PAJM, Soltesz I, McNaughton BL, Luczak A. Involvement of fast-spiking cells in ictal sequences during spontaneous seizures in rats with chronic temporal lobe epilepsy. Brain 2017; 140:2355-2369. [PMID: 29050390 PMCID: PMC6248724 DOI: 10.1093/brain/awx179] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 05/25/2017] [Accepted: 06/08/2017] [Indexed: 11/14/2022] Open
Abstract
See Lenck-Santini (doi:10.1093/awx205) for a scientific commentary on this article. Epileptic seizures represent altered neuronal network dynamics, but the temporal evolution and cellular substrates of the neuronal activity patterns associated with spontaneous seizures are not fully understood. We used simultaneous recordings from multiple neurons in the hippocampus and neocortex of rats with chronic temporal lobe epilepsy to demonstrate that subsets of cells discharge in a highly stereotypical sequential pattern during ictal events, and that these stereotypical patterns were reproducible across consecutive seizures. In contrast to the canonical view that principal cell discharges dominate ictal events, the ictal sequences were predominantly composed of fast-spiking, putative inhibitory neurons, which displayed unusually strong coupling to local field potential even before seizures. The temporal evolution of activity was characterized by unique dynamics where the most correlated neuronal pairs before seizure onset displayed the largest increases in correlation strength during the seizures. These results demonstrate the selective involvement of fast spiking interneurons in structured temporal sequences during spontaneous ictal events in hippocampal and neocortical circuits in experimental models of chronic temporal lobe epilepsy.
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Affiliation(s)
- Adam R Neumann
- Department of Neuroscience, Canadian Centre for Behavioural
Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4,
Canada
| | - Robrecht Raedt
- Department of Neurology, Ghent University, Gent, Belgium
| | - Hendrik W Steenland
- Department of Neuroscience, Canadian Centre for Behavioural
Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4,
Canada
| | | | - Katarzyna Bzymek
- Department of Neuroscience, Canadian Centre for Behavioural
Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4,
Canada
| | - Zaneta Navratilova
- Department of Neuroscience, Canadian Centre for Behavioural
Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4,
Canada
- Neuro-Electronics Research Flanders, Leuven, Belgium
| | - Lilia Mesina
- Department of Neuroscience, Canadian Centre for Behavioural
Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4,
Canada
| | - Jeanne Xie
- Department of Neuroscience, Canadian Centre for Behavioural
Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4,
Canada
| | - Valerie Lapointe
- Department of Neuroscience, Canadian Centre for Behavioural
Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4,
Canada
| | - Fabian Kloosterman
- Neuro-Electronics Research Flanders, Leuven, Belgium
- VIB, Leuven, Belgium
- Brain and Cognition Research unit, KU Leuven, Leuven, Belgium
| | - Kristl Vonck
- Department of Neurology, Ghent University, Gent, Belgium
| | | | - Ivan Soltesz
- Department of Neurosurgery, and Stanford Neurosciences Institute,
Stanford University, Stanford, CA, USA
| | - Bruce L McNaughton
- Department of Neuroscience, Canadian Centre for Behavioural
Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4,
Canada
- Department of Neurobiology and Behavior, University of California at
Irvine, Center for the Neurobiology of Learning and Memory, Irvine, CA, USA
| | - Artur Luczak
- Department of Neuroscience, Canadian Centre for Behavioural
Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4,
Canada
- Department of Neurosurgery, and Stanford Neurosciences Institute,
Stanford University, Stanford, CA, USA
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17
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Lévesque M, Salami P, Shiri Z, Avoli M. Interictal oscillations and focal epileptic disorders. Eur J Neurosci 2017. [DOI: 10.1111/ejn.13628] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Maxime Lévesque
- Department of Neurology & Neurosurgery; Montreal Neurological Institute; McGill University; 3801 University Street Montréal QC Canada H3A 2B4
| | - Pariya Salami
- Department of Neurology & Neurosurgery; Montreal Neurological Institute; McGill University; 3801 University Street Montréal QC Canada H3A 2B4
| | - Zahra Shiri
- Department of Neurology & Neurosurgery; Montreal Neurological Institute; McGill University; 3801 University Street Montréal QC Canada H3A 2B4
| | - Massimo Avoli
- Department of Neurology & Neurosurgery; Montreal Neurological Institute; McGill University; 3801 University Street Montréal QC Canada H3A 2B4
- Dipartimento di Medicina Sperimentale; Sapienza University of Rome; Roma Italy
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18
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A Novel Focal Seizure Pattern Generated in Superficial Layers of the Olfactory Cortex. J Neurosci 2017; 37:3544-3554. [PMID: 28264979 DOI: 10.1523/jneurosci.2239-16.2016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 12/06/2016] [Accepted: 12/16/2016] [Indexed: 02/03/2023] Open
Abstract
Seizure patterns identified in focal epilepsies caused by diverse etiologies are likely due to different pathogenic mechanisms. We describe here a novel, region-specific focal seizure pattern that mimics seizure activity observed in a subpopulation of patients submitted to presurgical monitoring with intracerebral electrodes. Distinctive seizure-like events (SLEs) are induced in the olfactory regions by acute treatment of both tangential brain slices and the isolated guinea pig brain with the potassium channel blocker 4-aminopyridine. Analysis of field potentials, intracellular activities, and extracellular potassium changes demonstrates that SLEs in the piriform cortex initiate in the superficial layer 1 lacking principal neurons with an activity-dependent increase of extracellular potassium. SLE progression (but not onset) does not require the participation of synaptic transmission and is mediated by diffusion of potassium to deep cortical layers. The novel seizure pattern here described is not observed in other cortical regions; it is proposed to rely on the peculiar organization of the superficial piriform cortex layers, which are characterized by unmyelinated axons and perisynaptic astroglial envelopes. This study reveals a sequence of ictogenic events in the olfactory cortex that were never described before in other cortical structures and supports the notion that altered potassium homeostasis and unmyelinated fibers may represent a potential vehicle for focal ictogenesis.SIGNIFICANCE STATEMENT We describe a novel seizure pattern peculiar of the olfactory cortex that resembles focal seizures with low-voltage fast activity at onset observed in humans. The findings suggest that network mechanisms responsible for seizure onset can be region specific.
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19
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Avoli M, de Curtis M, Gnatkovsky V, Gotman J, Köhling R, Lévesque M, Manseau F, Shiri Z, Williams S. Specific imbalance of excitatory/inhibitory signaling establishes seizure onset pattern in temporal lobe epilepsy. J Neurophysiol 2016; 115:3229-37. [PMID: 27075542 DOI: 10.1152/jn.01128.2015] [Citation(s) in RCA: 102] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 04/06/2016] [Indexed: 11/22/2022] Open
Abstract
Low-voltage fast (LVF) and hypersynchronous (HYP) patterns are the seizure-onset patterns most frequently observed in intracranial EEG recordings from mesial temporal lobe epilepsy (MTLE) patients. Both patterns also occur in models of MTLE in vivo and in vitro, and these studies have highlighted the predominant involvement of distinct neuronal network/neurotransmitter receptor signaling in each of them. First, LVF-onset seizures in epileptic rodents can originate from several limbic structures, frequently spread, and are associated with high-frequency oscillations in the ripple band (80-200 Hz), whereas HYP onset seizures initiate in the hippocampus and tend to remain focal with predominant fast ripples (250-500 Hz). Second, in vitro intracellular recordings from principal cells in limbic areas indicate that pharmacologically induced seizure-like discharges with LVF onset are initiated by a synchronous inhibitory event or by a hyperpolarizing inhibitory postsynaptic potential barrage; in contrast, HYP onset is associated with a progressive impairment of inhibition and concomitant unrestrained enhancement of excitation. Finally, in vitro optogenetic experiments show that, under comparable experimental conditions (i.e., 4-aminopyridine application), the initiation of LVF- or HYP-onset seizures depends on the preponderant involvement of interneuronal or principal cell networks, respectively. Overall, these data may provide insight to delineate better therapeutic targets in the treatment of patients presenting with MTLE and, perhaps, with other 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, Montréal, Québec, Canada; Facoltà di Medicina e Odontoiatria, Sapienza Università di Roma, Rome, Italy;
| | - Marco de Curtis
- Epilepsy Unit, Fondazione Istituto Neurologico Carlo Besta, Milan, Italy
| | - Vadym Gnatkovsky
- Epilepsy Unit, Fondazione Istituto Neurologico Carlo Besta, Milan, Italy
| | - Jean Gotman
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery and of Physiology, McGill University, Montréal, Québec, Canada
| | - Rüdiger Köhling
- Oscar-Langendorff-Institute of Physiology, Rostock University Medical Center, Rostock, Germany; and
| | - Maxime Lévesque
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery and of Physiology, McGill University, Montréal, Québec, Canada
| | - Frédéric Manseau
- Douglas Mental Health University Institute, McGill University, Montréal, Québec, Canada
| | - Zahra Shiri
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery and of Physiology, McGill University, Montréal, Québec, Canada
| | - Sylvain Williams
- Douglas Mental Health University Institute, McGill University, Montréal, Québec, Canada
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20
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de Curtis M, Avoli M. GABAergic networks jump-start focal seizures. Epilepsia 2016; 57:679-87. [PMID: 27061793 DOI: 10.1111/epi.13370] [Citation(s) in RCA: 89] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/19/2016] [Indexed: 01/20/2023]
Abstract
Abnormally enhanced glutamatergic excitation is commonly believed to mark the onset of a focal seizure. This notion, however, is not supported by firm evidence, and it will be challenged here. A general reduction of unit firing has been indeed observed in association with low-voltage fast activity at the onset of seizures recorded during presurgical intracranial monitoring in patients with focal, drug-resistant epilepsies. Moreover, focal seizures in animal models start with increased γ-aminobutyric acid (GABA)ergic interneuronal activity that silences principal cells. In vitro studies have shown that synchronous activation of GABAA receptors occurs at seizure onset and causes sizeable elevations in extracellular potassium, thus facilitating neuronal recruitment and seizure progression. A paradoxical involvement of GABAergic networks is required for the initiation of focal seizures characterized by low-voltage fast activity, which represents the most common seizure-onset pattern in focal epilepsies.
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Affiliation(s)
| | - Massimo Avoli
- Montreal Neurological Institute, McGill University, Montréal, Quebec, Canada.,Faculty of Medicine and Dentistry, La Sapienza University, Rome, Italy
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21
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Lu Y, Zhong C, Wang L, Wei P, He W, Huang K, Zhang Y, Zhan Y, Feng G, Wang L. Optogenetic dissection of ictal propagation in the hippocampal-entorhinal cortex structures. Nat Commun 2016; 7:10962. [PMID: 26997093 PMCID: PMC4802168 DOI: 10.1038/ncomms10962] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 02/05/2016] [Indexed: 12/17/2022] Open
Abstract
Temporal lobe epilepsy (TLE) is one of the most common drug-resistant forms of epilepsy in adults and usually originates in the hippocampal formations. However, both the network mechanisms that support the seizure spread and the exact directions of ictal propagation remain largely unknown. Here we report the dissection of ictal propagation in the hippocampal-entorhinal cortex (HP-EC) structures using optogenetic methods in multiple brain regions of a kainic acid-induced model of TLE in VGAT-ChR2 transgenic mice. We perform highly temporally precise cross-area analyses of epileptic neuronal networks and find a feed-forward propagation pathway of ictal discharges from the dentate gyrus/hilus (DGH) to the medial entorhinal cortex, instead of a re-entrant loop. We also demonstrate that activating DGH GABAergic interneurons can significantly inhibit the spread of ictal seizures and largely rescue behavioural deficits in kainate-exposed animals. These findings may shed light on future therapeutic treatments of TLE.
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Affiliation(s)
- Yi Lu
- Shenzhen Key Lab of Neuropsychiatric Modulation and Collaborative Innovation Center for Brain Science, CAS Center for Excellence in Brain Science and Intelligence Technology, the Brain Cognition and Brain Disease Institute (BCBDI) for Collaboration Research of SIAT at CAS and the McGovern Institute at MIT, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Cheng Zhong
- Shenzhen Key Lab of Neuropsychiatric Modulation and Collaborative Innovation Center for Brain Science, CAS Center for Excellence in Brain Science and Intelligence Technology, the Brain Cognition and Brain Disease Institute (BCBDI) for Collaboration Research of SIAT at CAS and the McGovern Institute at MIT, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lulu Wang
- Shenzhen Key Lab of Neuropsychiatric Modulation and Collaborative Innovation Center for Brain Science, CAS Center for Excellence in Brain Science and Intelligence Technology, the Brain Cognition and Brain Disease Institute (BCBDI) for Collaboration Research of SIAT at CAS and the McGovern Institute at MIT, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Pengfei Wei
- Shenzhen Key Lab of Neuropsychiatric Modulation and Collaborative Innovation Center for Brain Science, CAS Center for Excellence in Brain Science and Intelligence Technology, the Brain Cognition and Brain Disease Institute (BCBDI) for Collaboration Research of SIAT at CAS and the McGovern Institute at MIT, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Wei He
- Shenzhen Key Lab of Neuropsychiatric Modulation and Collaborative Innovation Center for Brain Science, CAS Center for Excellence in Brain Science and Intelligence Technology, the Brain Cognition and Brain Disease Institute (BCBDI) for Collaboration Research of SIAT at CAS and the McGovern Institute at MIT, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Kang Huang
- Shenzhen Key Lab of Neuropsychiatric Modulation and Collaborative Innovation Center for Brain Science, CAS Center for Excellence in Brain Science and Intelligence Technology, the Brain Cognition and Brain Disease Institute (BCBDI) for Collaboration Research of SIAT at CAS and the McGovern Institute at MIT, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yi Zhang
- Shenzhen Key Lab of Neuropsychiatric Modulation and Collaborative Innovation Center for Brain Science, CAS Center for Excellence in Brain Science and Intelligence Technology, the Brain Cognition and Brain Disease Institute (BCBDI) for Collaboration Research of SIAT at CAS and the McGovern Institute at MIT, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Yang Zhan
- Shenzhen Key Lab of Neuropsychiatric Modulation and Collaborative Innovation Center for Brain Science, CAS Center for Excellence in Brain Science and Intelligence Technology, the Brain Cognition and Brain Disease Institute (BCBDI) for Collaboration Research of SIAT at CAS and the McGovern Institute at MIT, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Guoping Feng
- McGovern Institute for Brain Research, Department of Brain and Cognitive Sciences, MIT, Cambridge, Massachusetts 02139, USA
| | - Liping Wang
- Shenzhen Key Lab of Neuropsychiatric Modulation and Collaborative Innovation Center for Brain Science, CAS Center for Excellence in Brain Science and Intelligence Technology, the Brain Cognition and Brain Disease Institute (BCBDI) for Collaboration Research of SIAT at CAS and the McGovern Institute at MIT, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
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22
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Sandler RA, Song D, Hampson RE, Deadwyler SA, Berger TW, Marmarelis VZ. Hippocampal closed-loop modeling and implications for seizure stimulation design. J Neural Eng 2015; 12:056017. [PMID: 26355815 DOI: 10.1088/1741-2560/12/5/056017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
OBJECTIVE Traditional hippocampal modeling has focused on the series of feedforward synapses known as the trisynaptic pathway. However, feedback connections from CA1 back to the hippocampus through the entorhinal cortex (EC) actually make the hippocampus a closed-loop system. By constructing a functional closed-loop model of the hippocampus, one may learn how both physiological and epileptic oscillations emerge and design efficient neurostimulation patterns to abate such oscillations. APPROACH Point process input-output models where estimated from recorded rodent hippocampal data to describe the nonlinear dynamical transformation from CA3 → CA1, via the schaffer-collateral synapse, and CA1 → CA3 via the EC. Each Volterra-like subsystem was composed of linear dynamics (principal dynamic modes) followed by static nonlinearities. The two subsystems were then wired together to produce the full closed-loop model of the hippocampus. MAIN RESULTS Closed-loop connectivity was found to be necessary for the emergence of theta resonances as seen in recorded data, thus validating the model. The model was then used to identify frequency parameters for the design of neurostimulation patterns to abate seizures. SIGNIFICANCE Deep-brain stimulation (DBS) is a new and promising therapy for intractable seizures. Currently, there is no efficient way to determine optimal frequency parameters for DBS, or even whether periodic or broadband stimuli are optimal. Data-based computational models have the potential to be used as a testbed for designing optimal DBS patterns for individual patients. However, in order for these models to be successful they must incorporate the complex closed-loop structure of the seizure focus. This study serves as a proof-of-concept of using such models to design efficient personalized DBS patterns for epilepsy.
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Affiliation(s)
- Roman A Sandler
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA
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23
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Hatch RJ, Reid CA, Petrou S. Generation of Local CA1 γ Oscillations by Tetanic Stimulation. J Vis Exp 2015:e52877. [PMID: 26327580 DOI: 10.3791/52877] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Neuronal network oscillations are important features of brain activity in health and disease and can be modulated by a range of clinically used drugs. A protocol is provided to generate a model for studying CA1 γ oscillations (20-80 Hz). These γ oscillations are stable for at least 30 min and depend upon excitatory and inhibitory synaptic activity in addition to activation of pacemaker currents. Tetanically stimulated oscillations have a number of reproducible and easily quantifiable characteristics including spike count, oscillation duration, latency and frequency that report upon the network state. The advantages of the electrically stimulated oscillations include stability, reproducibility and episodic acquisition enabling robust characterization of network function. This model of CA1 γ oscillations can be used to study cellular mechanisms and to systematically investigate how neuronal network activity is altered in disease and by drugs. Disease state pharmacology can be readily incorporated by the use of brain slices from genetically modified or interventional animal models to enable selection of drugs that specifically target disease mechanisms.
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Affiliation(s)
- Robert J Hatch
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne
| | - Christopher A Reid
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne
| | - Steven Petrou
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne;
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24
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Status Epilepticus Induced Spontaneous Dentate Gyrus Spikes: In Vivo Current Source Density Analysis. PLoS One 2015; 10:e0132630. [PMID: 26148195 PMCID: PMC4492740 DOI: 10.1371/journal.pone.0132630] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2015] [Accepted: 06/16/2015] [Indexed: 11/20/2022] Open
Abstract
The dentate gyrus is considered to function as an inhibitory gate limiting excitatory input to the hippocampus. Following status epilepticus (SE), this gating function is reduced and granule cells become hyper-excitable. Dentate spikes (DS) are large amplitude potentials observed in the dentate gyrus (DG) of normal animals. DS are associated with membrane depolarization of granule cells, increased activity of hilar interneurons and suppression of CA3 and CA1 pyramidal cell firing. Therefore, DS could act as an anti-excitatory mechanism. Because of the altered gating function of the dentate gyrus following SE, we sought to investigate how DS are affected following pilocarpine-induced SE. Two weeks following lithium-pilocarpine SE induction, hippocampal EEG was recorded in male Sprague-Dawley rats with 16-channel silicon probes under urethane anesthesia. Probes were placed dorso-ventrally to encompass either CA1-CA3 or CA1-DG layers. Large amplitude spikes were detected from EEG recordings and subject to current source density analysis. Probe placement was verified histologically to evaluate the anatomical localization of current sinks and the origin of DS. In 9 of 11 pilocarpine-treated animals and two controls, DS were confirmed with large current sinks in the molecular layer of the dentate gyrus. DS frequency was significantly increased in pilocarpine-treated animals compared to controls. Additionally, in pilocarpine-treated animals, DS displayed current sinks in the outer, middle and/or inner molecular layers. However, there was no difference in the frequency of events when comparing between layers. This suggests that following SE, DS can be generated by input from medial and lateral entorhinal cortex, or within the dentate gyrus. DS were associated with an increase in multiunit activity in the granule cell layer, but no change in CA1. These results suggest that following SE there is an increase in DS activity, potentially arising from hyperexcitability along the hippocampal-entorhinal pathway or within the dentate gyrus itself.
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de Curtis M, Avoli M. Initiation, Propagation, and Termination of Partial (Focal) Seizures. Cold Spring Harb Perspect Med 2015; 5:a022368. [PMID: 26134843 PMCID: PMC4484951 DOI: 10.1101/cshperspect.a022368] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The neurophysiological patterns that correlate with partial (focal) seizures are well defined in humans by standard electroencephalogram (EEG) and presurgical depth electrode recordings. Seizure patterns with similar features are reproduced in animal models of partial seizures and epilepsy. However, the network determinants that support interictal spikes, as well as the initiation, progression, and termination of seizures, are still elusive. Recent findings show that inhibitory networks are prominently involved at the onset of these seizures, and that extracellular changes in potassium contribute to initiate and sustain seizure progression. The end of a partial seizure correlates with an increase in network synchronization, which possibly involves both excitatory and inhibitory mechanisms.
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Affiliation(s)
- Marco de Curtis
- Unit of Epileptology and Experimental Neurophysiology and Fondazione Istituto Neurologico Carlo Besta, 20133 Milano, Italy
| | - Massimo Avoli
- Montreal Neurological Institute and Departments of Neurology and Neurosurgery and Physiology, McGill University, Montréal, H3A 2B4 Québec, Canada Department of Experimental Medicine, Facoltà di Medicina e Odontoiatria, Sapienza Università di Roma, 00185 Roma, Italy
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Synchronous inhibitory potentials precede seizure-like events in acute models of focal limbic seizures. J Neurosci 2015; 35:3048-55. [PMID: 25698742 DOI: 10.1523/jneurosci.3692-14.2015] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Interictal spikes in models of focal seizures and epilepsies are sustained by the synchronous activation of glutamatergic and GABAergic networks. The nature of population spikes associated with seizure initiation (pre-ictal spikes; PSs) is still undetermined. We analyzed the networks involved in the generation of both interictal and PSs in acute models of limbic cortex ictogenesis induced by pharmacological manipulations. Simultaneous extracellular and intracellular recordings from both principal cells and interneurons were performed in the medial entorhinal cortex of the in vitro isolated guinea pig brain during focal interictal and ictal discharges induced in the limbic network by intracortical and brief arterial infusions of either bicuculline methiodide (BMI) or 4-aminopyridine (4AP). Local application of BMI in the entorhinal cortex did not induce seizure-like events (SLEs), but did generate periodic interictal spikes sensitive to the glutamatergic non-NMDA receptor antagonist DNQX. Unlike local applications, arterial perfusion of either BMI or 4AP induced focal limbic SLEs. PSs just ahead of SLE were associated with hyperpolarizing potentials coupled with a complete blockade of firing in principal cells and burst discharges in putative interneurons. Interictal population spikes recorded from principal neurons between two SLEs correlated with a depolarizing potential. We demonstrate in two models of acute limbic SLE that PS events are different from interictal spikes and are sustained by synchronous activation of inhibitory networks. Our findings support a prominent role of synchronous network inhibition in the initiation of a focal seizure.
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de Curtis M, Librizzi L, Uva L. The in vitro isolated whole guinea pig brain as a model to study epileptiform activity patterns. J Neurosci Methods 2015; 260:83-90. [PMID: 25843067 DOI: 10.1016/j.jneumeth.2015.03.026] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Revised: 03/23/2015] [Accepted: 03/24/2015] [Indexed: 01/02/2023]
Abstract
BACKGROUND Research on ictogenesis is based on the study of activity between seizures and during seizures in animal models of epilepsy (chronic condition) or in in vitro slices obtained from naïve non-epileptic brains after treatment with pro-convulsive drugs, manipulations of the extracellular medium and specific stimulation protocols. NEW METHOD The in vitro isolated guinea pig brain retains the functional connectivity between brain structures and maintains interactions between neuronal, glial and vascular compartments. It is a close-to-in vivo preparation that offers experimental advantages not achieved with the use of other experimental models. Neurophysiological and imaging techniques can be utilized in this preparation to study brain activity during and between seizures induced by pharmacological or functional manipulations. RESULTS Cellular and network determinants of interictal and ictal discharges that reproduce abnormal patterns observed in human focal epilepsies and the associated changes in extracellular ion and blood-brain permeability can be identified and analyzed in the isolated guinea pig brain. COMPARISON WITH EXISTING METHODS Ictal and interictal patterns recorded in in vitro slices may show substantial differences from seizure activity recorded in vivo due to slicing procedure itself. The isolated guinea pig brain maintained in vitro by arterial perfusion combines the typical facilitated access of in vitro preparations, that are difficult to approach during in vivo experiments, with the preservation of larger neuronal networks. CONCLUSIONS The in vitro whole isolated guinea pig brain preparation offers an unique experimental model to study systemic and neurovascular changes during ictogenesis.
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Affiliation(s)
- Marco de Curtis
- Unit of Epileptology and Experimental Neurophysiology, Fondazione Istituto Neurologico Carlo Besta, Milano, Italy.
| | - Laura Librizzi
- Unit of Epileptology and Experimental Neurophysiology, Fondazione Istituto Neurologico Carlo Besta, Milano, Italy
| | - Laura Uva
- Unit of Epileptology and Experimental Neurophysiology, Fondazione Istituto Neurologico Carlo Besta, Milano, Italy
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Adams C, Adams NE, Traub RD, Whittington MA. Electrographic waveform structure predicts laminar focus location in a model of temporal lobe seizures in vitro. PLoS One 2015; 10:e0121676. [PMID: 25799020 PMCID: PMC4370580 DOI: 10.1371/journal.pone.0121676] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 02/03/2015] [Indexed: 11/20/2022] Open
Abstract
Temporal lobe epilepsy is the most common form of partial-onset epilepsy and accounts for the majority of adult epilepsy cases in most countries. A critical role for the hippocampus (and to some extent amygdala) in the pathology of these epilepsies is clear, with selective removal of these regions almost as effective as temporal lobectomy in reducing subsequent seizure risk. However, there is debate about whether hippocampus is ‘victim’ or ‘perpetrator’: The structure is ideally placed to ‘broadcast’ epileptiform activity to a great many other brain regions, but removal often leaves epileptiform events still occurring in cortex, particularly in adjacent areas, and recruitment of the hippocampus into seizure-like activity has been shown to be difficult in clinically-relevant models. Using a very simple model of acute epileptiform activity with known, single primary pathology (GABAA Receptor partial blockade), we track the onset and propagation of epileptiform events in hippocampus, parahippocampal areas and neocortex. In this model the hippocampus acts as a potential seizure focus for the majority of observed events. Events with hippocampal focus were far more readily propagated throughout parahippocampal areas and into neocortex than vice versa. The electrographic signature of events of hippocampal origin was significantly different to those of primary neocortical origin – a consequence of differential laminar activation. These data confirm the critical role of the hippocampus in epileptiform activity generation in the temporal lobe and suggest the morphology of non-invasive electrical recording of neocortical interictal events may be useful in confirming this role.
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Affiliation(s)
- Christopher Adams
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Natalie E. Adams
- Hull York Medical School, The University of York, York, United Kingdom
| | - Roger D. Traub
- Dept. Physical Sciences, IBM TJ Watson Research Center, New York, New York, United States of America
- Department of Neurology, Columbia University, New York, New York, United States of America
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Chung S, Spruston N, Koh S. Age-dependent changes in intrinsic neuronal excitability in subiculum after status epilepticus. PLoS One 2015; 10:e0119411. [PMID: 25775210 PMCID: PMC4361192 DOI: 10.1371/journal.pone.0119411] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Accepted: 01/30/2015] [Indexed: 12/03/2022] Open
Abstract
Kainic acid-induced status epilepticus (KA-SE) in mature rats results in the development of spontaneous recurrent seizures and a pattern of cell death resembling hippocampal sclerosis in patients with temporal lobe epilepsy. In contrast, KA-SE in young animals before postnatal day (P) 18 is less likely to cause cell death or epilepsy. To investigate whether changes in neuronal excitability occur in the subiculum after KA-SE, we examined the age-dependent effects of SE on the bursting neurons of subiculum, the major output region of the hippocampus. Patch-clamp recordings were used to monitor bursting in pyramidal neurons in the subiculum of rat hippocampal slices. Neurons were studied either one or 2-3 weeks following injection of KA or saline (control) in immature (P15) or more mature (P30) rats, which differ in their sensitivity to KA as well as the long-term sequelae of the KA-SE. A significantly greater proportion of subicular pyramidal neurons from P15 rats were strong-bursting neurons and showed increased frequency-dependent bursting compared to P30 animals. Frequency-dependent burst firing was enhanced in P30, but not in P15 rats following KA-SE. The enhancement of bursting induced by KA-SE in more mature rats suggests that the frequency-dependent limitation of repetitive burst firing, which normally occurs in the subiculum, is compromised following SE. These changes could facilitate the initiation of spontaneous recurrent seizures or their spread from the hippocampus to other parts of the brain.
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Affiliation(s)
- Sungkwon Chung
- Department of Physiology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, South Korea
| | - Nelson Spruston
- Scientific Program, Janelia Research Campus, Ashburn, Virginia, United States of America
| | - Sookyong Koh
- Neurobiology Program, Stanley Manne Children’s Research Institute, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America
- * E-mail:
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Sandler RA, Song D, Hampson RE, Deadwyler SA, Berger TW, Marmarelis VZ. Model-based asessment of an in-vivo predictive relationship from CA1 to CA3 in the rodent hippocampus. J Comput Neurosci 2014; 38:89-103. [PMID: 25260381 DOI: 10.1007/s10827-014-0530-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 09/02/2014] [Accepted: 09/05/2014] [Indexed: 01/02/2023]
Abstract
Although an anatomical connection from CA1 to CA3 via the Entorhinal Cortex (EC) and through backprojecting interneurons has long been known it exist, it has never been examined quantitatively on the single neuron level, in the in-vivo nonpatholgical, nonperturbed brain. Here, single spike activity was recorded using a multi-electrode array from the CA3 and CA1 areas of the rodent hippocampus (N = 7) during a behavioral task. The predictive power from CA3→CA1 and CA1→CA3 was examined by constructing Multivariate Autoregressive (MVAR) models from recorded neurons in both directions. All nonsignificant inputs and models were identified and removed by means of Monte Carlo simulation methods. It was found that 121/166 (73 %) CA3→CA1 models and 96/145 (66 %) CA1→CA3 models had significant predictive power, thus confirming a predictive 'Granger' causal relationship from CA1 to CA3. This relationship is thought to be caused by a combination of truly causal connections such as the CA1→EC→CA3 pathway and common inputs such as those from the Septum. All MVAR models were then examined in the frequency domain and it was found that CA3 kernels had significantly more power in the theta and beta range than those of CA1, confirming CA3's role as an endogenous hippocampal pacemaker.
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Affiliation(s)
- Roman A Sandler
- Department of Biomedical Engineering, University of Southern California, DRB 367, 1042 Downey Way Los Angeles, Los Angeles, CA, 90089, USA,
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Boido D, Gnatkovsky V, Uva L, Francione S, de Curtis M. Simultaneous enhancement of excitation and postburst inhibition at the end of focal seizures. Ann Neurol 2014; 76:826-36. [PMID: 24916758 DOI: 10.1002/ana.24193] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Revised: 06/04/2014] [Accepted: 06/04/2014] [Indexed: 11/10/2022]
Abstract
OBJECTIVE Comprehension of the events that lead to seizure termination contributes to the development of strategies to confine propagation of ictal discharges. It is commonly assumed that the inhibitory control fails during seizures and recovers after the end of the ictal event. We examine the possibility that a progressive increase of inhibition that counters an increase in the strength of excitation contributes to terminating a focal seizure. METHODS We analyzed seizures acutely induced by pharmacological manipulations (bicuculline and 4-aminopyridine) in the entorhinal cortex and in the hippocampus of the in vitro isolated guinea pig brain. RESULTS As seizures ended, extracellular and intracellular recordings showed periodic bursting that progressively decreased in frequency. During the late bursting phase, the duration, number, and rate of occurrence of spikes within single bursts remained constant, whereas cumulative spike amplitude (index of excitation during a burst) and interburst interval (index of inhibition between bursts) progressively increased. The increment of average/cumulative burst excitation and interburst interval toward seizure end was confirmed in human focal seizures recorded with intracerebral electrodes in patients with drug-resistant partial epilepsies. A postburst refractory period of circa 2 seconds that increases with time toward the end of the seizure was confirmed in the experimental model by probing interburst epochs in the CA1 region with local dentate gyrus stimulation just suprathreshold for burst generation. INTERPRETATION Our findings support the concept that focal seizures are terminated by the simultaneous and opposing enhancement of excitation (burst activity) in addition to postburst inhibition. We hypothesize that a seizure stops when postburst inhibition becomes large enough to prevent reactivation of excitation.
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Affiliation(s)
- Davide Boido
- Unit of Epileptology and Experimental Neurophysiology, Carlo Besta Neurological Institute Foundation, Milan, Italy
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Hatch RJ, Reid CA, Petrou S. Enhanced in vitro CA1 network activity in a sodium channel β1(C121W) subunit model of genetic epilepsy. Epilepsia 2014; 55:601-8. [PMID: 24605816 DOI: 10.1111/epi.12568] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/15/2014] [Indexed: 11/30/2022]
Abstract
OBJECTIVE A NaV β1(C121W) mouse model of human genetic epilepsy has enhanced neuronal excitability and temperature sensitivity attributed to a decreased threshold for action potential firing in the axon initial segment. To investigate the network consequences of this neuronal dysfunction and to establish a genetic disease state model we developed an in vitro assay to investigate CA1 network properties and antiepileptic drug sensitivity. METHODS CA1 network oscillations were induced by tetanic stimulation and average number of spikes, interspike interval (ISI), duration, and latency were measured in slices from control and NaV β1(C121W) heterozygous mice in the presence and absence of retigabine or carbamazepine. Retigabine was also tested in a thermogenic seizure model. RESULTS Oscillations were reliably induced by tetanic stimulation and were maintained after severing connections between CA3 and CA1, suggesting a local recurrent circuit. Blocking α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), γ-aminobutyric acid receptor A (GABAA ), Ih , and T-type Ca(2+) channels/receptors reduced the number of spikes. Slices from NaV β1(C121W) heterozygous mice displayed several hallmarks of increased network excitability including increases in duration of the oscillation, the number and frequency of spikes and a decrease in their onset latency. The effect of genotype on network excitability was temperature sensitive, as it was seen only at elevated temperatures. Carbamazepine and retigabine were more effective in reducing network excitability in slices from NaV β1(C121W) heterozygous mice. Retigabine appeared to be more effective in suppressing time to thermogenic seizures in NaV β1(C121W) heterozygous mice compared to wild-type (WT) controls. SIGNIFICANCE Hippocampal networks of the NaV β1(C121W) heterozygous mouse model of genetic epilepsy show enhanced excitability consistent with earlier single neuron studies bridging important scales of brain complexity relevant to seizure genesis. Altered pharmacosensitivity further suggests that genetic epilepsy models may be useful in the development of novel antiepileptic drugs that target disease state pathology. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here.
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Affiliation(s)
- Robert J Hatch
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
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Jiruska P, de Curtis M, Jefferys JGR. Modern concepts of focal epileptic networks. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2014; 114:1-7. [PMID: 25078496 DOI: 10.1016/b978-0-12-418693-4.00001-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Premysl Jiruska
- Department of Developmental Epileptology, Institute of Physiology, Academy of Sciences of Czech Republic, Prague, Czech Republic; Department of Neurology, 2nd Faculty of Medicine, Charles University in Prague, Motol University Hospital, Prague, Czech Republic.
| | - Marco de Curtis
- Department of Epileptology and Experimental Neurophysiology, Fondazione IRCCS, Istituto Neurologico C Besta, Milan, Italy
| | - John G R Jefferys
- Neuronal Networks Group, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, United Kingdom; Department of Pharmacology, University of Oxford, Oxford, United Kingdom
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