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Lado WE, Xu X, Hablitz JJ. Modulation of Epileptiform Activity by Three Subgroups of GABAergic Interneurons in Mouse Somatosensory Cortex. Epilepsy Res 2022; 183:106937. [DOI: 10.1016/j.eplepsyres.2022.106937] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 04/05/2022] [Accepted: 04/24/2022] [Indexed: 11/29/2022]
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2
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Righes Marafiga J, Vendramin Pasquetti M, Calcagnotto ME. GABAergic interneurons in epilepsy: More than a simple change in inhibition. Epilepsy Behav 2021; 121:106935. [PMID: 32035792 DOI: 10.1016/j.yebeh.2020.106935] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 01/08/2020] [Accepted: 01/09/2020] [Indexed: 12/20/2022]
Abstract
The pathophysiology of epilepsy has been historically grounded on hyperexcitability attributed to the oversimplified imbalance between excitation (E) and inhibition (I) in the brain. The decreased inhibition is mostly attributed to deficits in gamma-aminobutyric acid-containing (GABAergic) interneurons, the main source of inhibition in the central nervous system. However, the cell diversity, the wide range of spatiotemporal connectivity, and the distinct effects of the neurotransmitter GABA especially during development, must be considered to critically revisit the concept of hyperexcitability caused by decreased inhibition as a key characteristic in the development of epilepsy. Here, we will discuss that behind this known mechanism, there is a heterogeneity of GABAergic interneurons with distinct functions and sources, which have specific roles in controlling the neural network activity within the recruited microcircuit and altered network during the epileptogenic process. This article is part of the Special Issue "NEWroscience 2018.
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Affiliation(s)
- Joseane Righes Marafiga
- Neurophysiology and Neurochemistry of Neuronal Excitability and Synaptic Plasticity Laboratory, 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, 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, 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; Graduate Program in Neuroscience, Universidade Federal do Rio Grande do Sul, Porto Alegre 90046-900, RS, Brazil.
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3
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Regulation of GABA A Receptors Induced by the Activation of L-Type Voltage-Gated Calcium Channels. MEMBRANES 2021; 11:membranes11070486. [PMID: 34209589 PMCID: PMC8304739 DOI: 10.3390/membranes11070486] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 06/23/2021] [Accepted: 06/25/2021] [Indexed: 12/30/2022]
Abstract
GABAA receptors are pentameric ion channels that mediate most synaptic and tonic extrasynaptic inhibitory transmissions in the central nervous system. There are multiple GABAA receptor subtypes constructed from 19 different subunits in mammals that exhibit different regional and subcellular distributions and distinct pharmacological properties. Dysfunctional alterations of GABAA receptors are associated with various neuropsychiatric disorders. Short- and long-term plastic changes in GABAA receptors can be induced by the activation of different intracellular signaling pathways that are triggered, under physiological and pathological conditions, by calcium entering through voltage-gated calcium channels. This review discusses several mechanisms of regulation of GABAA receptor function that result from the activation of L-type voltage gated calcium channels. Calcium influx via these channels activates different signaling cascades that lead to changes in GABAA receptor transcription, phosphorylation, trafficking, and synaptic clustering, thus regulating the inhibitory synaptic strength. These plastic mechanisms regulate the interplay of synaptic excitation and inhibition that is crucial for the normal function of neuronal circuits.
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4
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Rasia-Filho AA, Guerra KTK, Vásquez CE, Dall’Oglio A, Reberger R, Jung CR, Calcagnotto ME. The Subcortical-Allocortical- Neocortical continuum for the Emergence and Morphological Heterogeneity of Pyramidal Neurons in the Human Brain. Front Synaptic Neurosci 2021; 13:616607. [PMID: 33776739 PMCID: PMC7991104 DOI: 10.3389/fnsyn.2021.616607] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 02/01/2021] [Indexed: 11/13/2022] Open
Abstract
Human cortical and subcortical areas integrate emotion, memory, and cognition when interpreting various environmental stimuli for the elaboration of complex, evolved social behaviors. Pyramidal neurons occur in developed phylogenetic areas advancing along with the allocortex to represent 70-85% of the neocortical gray matter. Here, we illustrate and discuss morphological features of heterogeneous spiny pyramidal neurons emerging from specific amygdaloid nuclei, in CA3 and CA1 hippocampal regions, and in neocortical layers II/III and V of the anterolateral temporal lobe in humans. Three-dimensional images of Golgi-impregnated neurons were obtained using an algorithm for the visualization of the cell body, dendritic length, branching pattern, and pleomorphic dendritic spines, which are specialized plastic postsynaptic units for most excitatory inputs. We demonstrate the emergence and development of human pyramidal neurons in the cortical and basomedial (but not the medial, MeA) nuclei of the amygdala with cells showing a triangular cell body shape, basal branched dendrites, and a short apical shaft with proximal ramifications as "pyramidal-like" neurons. Basomedial neurons also have a long and distally ramified apical dendrite not oriented to the pial surface. These neurons are at the beginning of the allocortex and the limbic lobe. "Pyramidal-like" to "classic" pyramidal neurons with laminar organization advance from the CA3 to the CA1 hippocampal regions. These cells have basal and apical dendrites with specific receptive synaptic domains and several spines. Neocortical pyramidal neurons in layers II/III and V display heterogeneous dendritic branching patterns adapted to the space available and the afferent inputs of each brain area. Dendritic spines vary in their distribution, density, shapes, and sizes (classified as stubby/wide, thin, mushroom-like, ramified, transitional forms, "atypical" or complex forms, such as thorny excrescences in the MeA and CA3 hippocampal region). Spines were found isolated or intermingled, with evident particularities (e.g., an extraordinary density in long, deep CA1 pyramidal neurons), and some showing a spinule. We describe spiny pyramidal neurons considerably improving the connectional and processing complexity of the brain circuits. On the other hand, these cells have some vulnerabilities, as found in neurodegenerative Alzheimer's disease and in temporal lobe epilepsy.
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Affiliation(s)
- Alberto A. Rasia-Filho
- Department of Basic Sciences/Physiology and Graduate Program in Biosciences, Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil
- Graduate Program in Neuroscience, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Kétlyn T. Knak Guerra
- Graduate Program in Neuroscience, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Carlos Escobar Vásquez
- Graduate Program in Neuroscience, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Aline Dall’Oglio
- Department of Basic Sciences/Physiology and Graduate Program in Biosciences, Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil
| | - Roman Reberger
- Medical Engineering Program, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Cláudio R. Jung
- Institute of Informatics, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Maria Elisa Calcagnotto
- Graduate Program in Neuroscience, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
- Neurophysiology and Neurochemistry of Neuronal Excitability and Synaptic Plasticity Laboratory, Department of Biochemistry and Biochemistry Graduate Program, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
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5
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Kuchenbuch M, Nabbout R, Yochum M, Sauleau P, Modolo J, Wendling F, Benquet P. In silico model reveals the key role of GABA in KCNT1-epilepsy in infancy with migrating focal seizures. Epilepsia 2021; 62:683-697. [PMID: 33617692 DOI: 10.1111/epi.16834] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 12/08/2020] [Accepted: 01/18/2021] [Indexed: 02/06/2023]
Abstract
OBJECTIVE This study was undertaken to investigate how gain of function (GOF) of slack channel due to a KCNT1 pathogenic variant induces abnormal neuronal cortical network activity and generates specific electroencephalographic (EEG) patterns of epilepsy in infancy with migrating focal seizures. METHODS We used detailed microscopic computational models of neurons to explore the impact of GOF of slack channel (explicitly coded) on each subtype of neurons and on a cortical micronetwork. Then, we adapted a thalamocortical macroscopic model considering results obtained in detailed models and immature properties related to epileptic brain in infancy. Finally, we compared simulated EEGs resulting from the macroscopic model with interictal and ictal patterns of affected individuals using our previously reported EEG markers. RESULTS The pathogenic variants of KCNT1 strongly decreased the firing rate properties of γ-aminobutyric acidergic (GABAergic) interneurons and, to a lesser extent, those of pyramidal cells. This change led to hyperexcitability with increased synchronization in a cortical micronetwork. At the macroscopic scale, introducing slack GOF effect resulted in epilepsy of infancy with migrating focal seizures (EIMFS) EEG interictal patterns. Increased excitation-to-inhibition ratio triggered seizure, but we had to add dynamic depolarizing GABA between somatostatin-positive interneurons and pyramidal cells to obtain migrating seizure. The simulated migrating seizures were close to EIMFS seizures, with similar values regarding the delay between the different ictal activities (one of the specific EEG markers of migrating focal seizures due to KCNT1 pathogenic variants). SIGNIFICANCE This study illustrates the interest of biomathematical models to explore pathophysiological mechanisms bridging the gap between the functional effect of gene pathogenic variants and specific EEG phenotype. Such models can be complementary to in vitro cellular and animal models. This multiscale approach provides an in silico framework that can be further used to identify candidate innovative therapies.
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Affiliation(s)
- Mathieu Kuchenbuch
- LTSI-U1099, Université de Rennes 1, INSERM, Rennes, France.,Department of Pediatric Neurology, Reference Center for Rare Epilepsies, Hôpital Necker-Enfants malades, member of European Network EPICARE, Paris, France.,Laboratory of Translational Research for Neurological Disorders (UMR 1163), IHU Imagine Institute of Genetic Diseases, INSERM, University of Paris, Paris, France
| | - Rima Nabbout
- Department of Pediatric Neurology, Reference Center for Rare Epilepsies, Hôpital Necker-Enfants malades, member of European Network EPICARE, Paris, France.,Laboratory of Translational Research for Neurological Disorders (UMR 1163), IHU Imagine Institute of Genetic Diseases, INSERM, University of Paris, Paris, France
| | - Maxime Yochum
- LTSI-U1099, Université de Rennes 1, INSERM, Rennes, France
| | - Paul Sauleau
- CHU de Rennes (Department of Neurophysiology), "Behavior and Basal Ganglia" Research Unit (EA4712), University of Rennes, Rennes, France
| | - Julien Modolo
- LTSI-U1099, Université de Rennes 1, INSERM, Rennes, France
| | | | - Pascal Benquet
- LTSI-U1099, Université de Rennes 1, INSERM, Rennes, France
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6
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Villasana-Salazar B, Hernández-Soto R, Guerrero-Gómez ME, Ordaz B, Manrique-Maldonado G, Salgado-Puga K, Peña-Ortega F. Chronic intermittent hypoxia transiently increases hippocampal network activity in the gamma frequency band and 4-Aminopyridine-induced hyperexcitability in vitro. Epilepsy Res 2020; 166:106375. [PMID: 32745888 DOI: 10.1016/j.eplepsyres.2020.106375] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 04/21/2020] [Accepted: 05/28/2020] [Indexed: 12/12/2022]
Abstract
Chronic intermittent hypoxia (CIH) is the most distinct feature of obstructive sleep apnea (OSA), a common breathing and sleep disorder that leads to several neuropathological consequences, including alterations in the hippocampal network and in seizure susceptibility. However, it is currently unknown whether these alterations are permanent or remit upon normal oxygenation. Here, we investigated the effects of CIH on hippocampal spontaneous network activity and hyperexcitability in vitro and explored whether these alterations endure or fade after normal oxygenation. Results showed that applying CIH for 21 days to adult rats increases gamma-band hippocampal network activity and aggravates 4-Aminopyridine-induced epileptiform activity in vitro. Interestingly, these CIH-induced alterations remit after 30 days of normal oxygenation. Our findings indicate that hippocampal network alterations and increased seizure susceptibility induced by CIH are not permanent and can be spontaneously reverted, suggesting that therapeutic interventions against OSA in patients with epilepsy, such as surgery or continuous positive airway pressure (CPAP), could be favorable for seizure control.
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Affiliation(s)
- Benjamín Villasana-Salazar
- Departamento de Neurobiología del Desarrollo y Neurofisiología, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Querétaro, QRO 76230, México
| | - Rebeca Hernández-Soto
- Departamento de Neurobiología del Desarrollo y Neurofisiología, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Querétaro, QRO 76230, México
| | - María Estefanía Guerrero-Gómez
- Departamento de Neurobiología del Desarrollo y Neurofisiología, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Querétaro, QRO 76230, México
| | - Benito Ordaz
- Departamento de Neurobiología del Desarrollo y Neurofisiología, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Querétaro, QRO 76230, México
| | - Guadalupe Manrique-Maldonado
- Departamento de Neurobiología del Desarrollo y Neurofisiología, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Querétaro, QRO 76230, México
| | - Karla Salgado-Puga
- Departamento de Neurobiología del Desarrollo y Neurofisiología, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Querétaro, QRO 76230, México
| | - Fernando Peña-Ortega
- Departamento de Neurobiología del Desarrollo y Neurofisiología, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Querétaro, QRO 76230, México.
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7
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Bartholome O, de la Brassinne Bonardeaux O, Neirinckx V, Rogister B. A Composite Sketch of Fast-Spiking Parvalbumin-Positive Neurons. Cereb Cortex Commun 2020; 1:tgaa026. [PMID: 34296100 PMCID: PMC8153048 DOI: 10.1093/texcom/tgaa026] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 06/15/2020] [Accepted: 06/15/2020] [Indexed: 01/28/2023] Open
Abstract
Parvalbumin-positive neurons are inhibitory neurons that release GABA and are mostly represented by fast-spiking basket or chandelier cells. They constitute a minor neuronal population, yet their peculiar profiles allow them to react quickly to any event in the brain under normal or pathological conditions. In this review, we will summarize the current knowledge about the fundamentals of fast-spiking parvalbumin-positive neurons, focusing on their morphology and specific channel/protein content. Next, we will explore their development, maturation, and migration in the brain. Finally, we will unravel their potential contribution to the physiopathology of epilepsy.
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Affiliation(s)
| | | | | | - Bernard Rogister
- GIGA-Neurosciences, University of Liege, 4000 Liège, Belgium.,Neurology Department, CHU, Academic Hospital, University of Liege, 4000 Liège, Belgium
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8
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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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9
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Magloire V, Cornford J, Lieb A, Kullmann DM, Pavlov I. KCC2 overexpression prevents the paradoxical seizure-promoting action of somatic inhibition. Nat Commun 2019; 10:1225. [PMID: 30874549 PMCID: PMC6420604 DOI: 10.1038/s41467-019-08933-4] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Accepted: 02/01/2019] [Indexed: 11/09/2022] Open
Abstract
Although cortical interneurons are apparently well-placed to suppress seizures, several recent reports have highlighted a paradoxical role of perisomatic-targeting parvalbumin-positive (PV+) interneurons in ictogenesis. Here, we use an acute in vivo model of focal cortical seizures in awake behaving mice, together with closed-loop optogenetic manipulation of PV+ interneurons, to investigate their function during seizures. We show that photo-depolarization of PV+ interneurons rapidly switches from an anti-ictal to a pro-ictal effect within a few seconds of seizure initiation. The pro-ictal effect of delayed photostimulation of PV+ interneurons was not shared with dendrite-targeting somatostatin-positive (SOM+) interneurons. We also show that this switch can be prevented by overexpression of the neuronal potassium-chloride co-transporter KCC2 in principal cortical neurons. These results suggest that strategies aimed at improving the ability of principal neurons to maintain a trans-membrane chloride gradient in the face of excessive network activity can prevent interneurons from contributing to seizure perpetuation.
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Affiliation(s)
- Vincent Magloire
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, London, WC1N 3BG, UK.
| | - Jonathan Cornford
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Andreas Lieb
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Dimitri M Kullmann
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Ivan Pavlov
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, London, WC1N 3BG, UK.
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10
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Amakhin DV, Soboleva EB, Ergina JL, Malkin SL, Chizhov AV, Zaitsev AV. Seizure-Induced Potentiation of AMPA Receptor-Mediated Synaptic Transmission in the Entorhinal Cortex. Front Cell Neurosci 2018; 12:486. [PMID: 30618633 PMCID: PMC6297849 DOI: 10.3389/fncel.2018.00486] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2018] [Accepted: 11/29/2018] [Indexed: 11/22/2022] Open
Abstract
Excessive excitation is considered one of the key mechanisms underlying epileptic seizures. We investigated changes in the evoked postsynaptic responses of medial entorhinal cortex (ERC) pyramidal neurons by seizure-like events (SLEs), using the modified 4-aminopyridine (4-AP) model of epileptiform activity. Rat brain slices were perfused with pro-epileptic solution contained 4-AP and elevated potassium and reduced magnesium concentration. We demonstrated that 15-min robust epileptiform activity in slices leads to an increase in the amplitude of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-mediated component of the evoked response, as well as an increase in the polysynaptic γ-aminobutyric acid (GABA) and N-methyl-D-aspartate (NMDA) receptor-mediated components. The increase in AMPA-mediated postsynaptic conductance depends on NMDA receptor activation. It persists for at least 15 min after the cessation of SLEs and is partly attributed to the inclusion of calcium-permeable AMPA receptors in the postsynaptic membrane. The mathematical modeling of the evoked responses using the conductance-based refractory density (CBRD) approach indicated that such augmentation of the AMPA receptor function and depolarization by GABA receptors results in prolonged firing that explains the increase in polysynaptic components, which contribute to overall network excitability. Taken together, our data suggest that AMPA receptor enhancement could be a critical determinant of sustained status epilepticus (SE).
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Affiliation(s)
- Dmitry V Amakhin
- Laboratory of Molecular Mechanisms of Neural Interactions, Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, Saint Petersburg, Russia
| | - Elena B Soboleva
- Laboratory of Molecular Mechanisms of Neural Interactions, Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, Saint Petersburg, Russia
| | - Julia L Ergina
- Laboratory of Molecular Mechanisms of Neural Interactions, Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, Saint Petersburg, Russia
| | - Sergey L Malkin
- Laboratory of Molecular Mechanisms of Neural Interactions, Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, Saint Petersburg, Russia
| | - Anton V Chizhov
- Laboratory of Molecular Mechanisms of Neural Interactions, Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, Saint Petersburg, Russia.,Ioffe Institute, Russian Academy of Sciences, Saint Petersburg, Russia
| | - Aleksey V Zaitsev
- Laboratory of Molecular Mechanisms of Neural Interactions, Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, Saint Petersburg, Russia.,Institute of Experimental Medicine, Almazov National Medical Research Centre, Saint Petersburg, Russia
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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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Ye H, Kaszuba S. Inhibitory or excitatory? Optogenetic interrogation of the functional roles of GABAergic interneurons in epileptogenesis. J Biomed Sci 2017; 24:93. [PMID: 29202749 PMCID: PMC5715558 DOI: 10.1186/s12929-017-0399-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 11/28/2017] [Indexed: 01/22/2023] Open
Abstract
Alteration in the excitatory/inhibitory neuronal balance is believed to be the underlying mechanism of epileptogenesis. Based on this theory, GABAergic interneurons are regarded as the primary inhibitory neurons, whose failure of action permits hyperactivity in the epileptic circuitry. As a consequence, optogenetic excitation of GABAergic interneurons is widely used for seizure suppression. However, recent evidence argues for the context-dependent, possibly “excitatory” roles that GABAergic cells play in epileptic circuitry. We reviewed current optogenetic approaches that target the “inhibitory” roles of GABAergic interneurons for seizure control. We also reviewed interesting evidence that supports the “excitatory” roles of GABAergic interneurons in epileptogenesis. GABAergic interneurons can provide excitatory effects to the epileptic circuits via several distinct neurological mechanisms. (1) GABAergic interneurons can excite postsynaptic neurons, due to the raised reversal potential of GABA receptors in the postsynaptic cells. (2) Continuous activity in GABAergic interneurons could lead to transient GABA depletion, which prevents their inhibitory effect on pyramidal cells. (3) GABAergic interneurons can synchronize network activity during seizure. (4) Some GABAergic interneurons inhibit other interneurons, causing disinhibition of pyramidal neurons and network hyperexcitability. The dynamic, context-dependent role that GABAergic interneurons play in seizure requires further investigation of their functions at single cell and circuitry level. New optogenetic protocols that target GABAergic inhibition should be explored for seizure suppression.
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Affiliation(s)
- Hui Ye
- Department of Biology, Loyola University Chicago, Quinlan Life Sciences Education and Research Center, 1032 W. Sheridan Rd, Chicago, IL, 60660, USA.
| | - Stephanie Kaszuba
- Department of Biology, Loyola University Chicago, Quinlan Life Sciences Education and Research Center, 1032 W. Sheridan Rd, Chicago, IL, 60660, USA
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13
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Sawano E, Iwatani K, Tominaga-Yoshino K, Ogura A, Tashiro T. Reduction in NPY-positive neurons and dysregulation of excitability in young senescence-accelerated mouse prone 8 (SAMP8) hippocampus precede the onset of cognitive impairment. J Neurochem 2015; 135:287-300. [PMID: 26250996 DOI: 10.1111/jnc.13274] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Revised: 07/16/2015] [Accepted: 07/28/2015] [Indexed: 12/16/2023]
Abstract
The senescence-accelerated mouse prone 8 (SAMP8) strain is considered a neurodegeneration model showing age-related cognitive deficits with little physical impairment. Young SAMP8 mice, however, exhibit signs of disturbances in development such as marked hyperactivity and reduced anxiety well before the onset of cognitive impairment. As the key enzyme in local regulation of thyroid hormone (TH) signaling, type 2 deiodinase, was significantly reduced in the SAMP8 hippocampus relative to that of the normally aging SAM-resistant 1 (SAMR1), we used these two strains to compare the development of the hippocampal GABAergic system, which is known to be strongly affected by hypothyroidism. Among GABAergic components, neuronal K+ /Cl- co-transporter 2 was down-regulated in SAMP8 transiently at 2 weeks. Although distribution of total GABAergic neurons was similar in both strains, 22-30% reduction was observed in the neuropeptide Y (NPY)-positive subpopulation of GABAergic neurons in SAMP8. Electrophysiological studies on hippocampal slices obtained at 4 weeks revealed that epileptiform activity, induced by high-frequency stimulation, lasted four times longer in SAMP8 compared with SAMR1, indicating a dysregulation of excitability that may be linked to the behavioral abnormalities of young SAMP8 and to neurodegeneration later on in life. Local attenuation of TH signaling may thus impact the normal development of the GABAergic system.
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Affiliation(s)
- Erika Sawano
- Department of Chemistry & Biological Science, School of Science & Engineering, Aoyama Gakuin University, Sagamihara, Kanagawa, Japan
| | - Kanako Iwatani
- Department of Chemistry & Biological Science, School of Science & Engineering, Aoyama Gakuin University, Sagamihara, Kanagawa, Japan
| | - Keiko Tominaga-Yoshino
- Department of Neuroscience, Osaka University Graduate School of Frontier Biosciences, Suita, Osaka, Japan
| | - Akihiko Ogura
- Department of Neuroscience, Osaka University Graduate School of Frontier Biosciences, Suita, Osaka, Japan
| | - Tomoko Tashiro
- Department of Chemistry & Biological Science, School of Science & Engineering, Aoyama Gakuin University, Sagamihara, Kanagawa, Japan
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14
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Parvalbumin-Positive Inhibitory Interneurons Oppose Propagation But Favor Generation of Focal Epileptiform Activity. J Neurosci 2015; 35:9544-57. [PMID: 26134638 DOI: 10.1523/jneurosci.5117-14.2015] [Citation(s) in RCA: 100] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Parvalbumin (Pv)-positive inhibitory interneurons effectively control network excitability, and their optogenetic activation has been reported to block epileptic seizures. An intense activity in GABAergic interneurons, including Pv interneurons, before seizures has been described in different experimental models of epilepsy, raising the hypothesis that an increased GABAergic inhibitory signal may, under certain conditions, initiate seizures. It is therefore unclear whether the activity of Pv interneurons enhances or opposes epileptiform activities. Here we use a mouse cortical slice model of focal epilepsy in which the epileptogenic focus can be identified and the role of Pv interneurons in the generation and propagation of seizure-like ictal events is accurately analyzed by a combination of optogenetic, electrophysiological, and imaging techniques. We found that a selective activation of Pv interneurons at the focus failed to block ictal generation and induced postinhibitory rebound spiking in pyramidal neurons, enhancing neuronal synchrony and promoting ictal generation. In contrast, a selective activation of Pv interneurons distant from the focus blocked ictal propagation and shortened ictal duration at the focus. We revealed that the reduced ictal duration was a direct consequence of the ictal propagation block, probably by preventing newly generated afterdischarges to travel backwards to the original focus of ictal initiation. Similar results were obtained upon individual Pv interneuron activation by intracellular depolarizing current pulses. The functional dichotomy of Pv interneurons here described opens new perspectives to our understanding of how local inhibitory circuits govern generation and spread of focal epileptiform activities.
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Unit Activity of Hippocampal Interneurons before Spontaneous Seizures in an Animal Model of Temporal Lobe Epilepsy. J Neurosci 2015; 35:6600-18. [PMID: 25904809 DOI: 10.1523/jneurosci.4786-14.2015] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Mechanisms of seizure initiation are unclear. To evaluate the possible roles of inhibitory neurons, unit recordings were obtained in the dentate gyrus, CA3, CA1, and subiculum of epileptic pilocarpine-treated rats as they experienced spontaneous seizures. Most interneurons in the dentate gyrus, CA1, and subiculum increased their firing rate before seizures, and did so with significant consistency from seizure to seizure. Identification of CA1 interneuron subtypes based on firing characteristics during theta and sharp waves suggested that a parvalbumin-positive basket cell and putative bistratified cells, but not oriens lacunosum moleculare cells, were activated preictally. Preictal changes occurred much earlier than those described by most previous in vitro studies. Preictal activation of interneurons began earliest (>4 min before seizure onset), increased most, was most prevalent in the subiculum, and was minimal in CA3. Preictal inactivation of interneurons was most common in CA1 (27% of interneurons) and included a putative ivy cell and parvalbumin-positive basket cell. Increased or decreased preictal activity correlated with whether interneurons fired faster or slower, respectively, during theta activity. Theta waves were more likely to occur before seizure onset, and increased preictal firing of subicular interneurons correlated with theta activity. Preictal changes by other hippocampal interneurons were largely independent of theta waves. Within seconds of seizure onset, many interneurons displayed a brief pause in firing and a later, longer drop that was associated with reduced action potential amplitude. These findings suggest that many interneurons inactivate during seizures, most increase their activity preictally, but some fail to do so at the critical time before seizure onset.
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Johnson SE, Hudson JL, Kapur J. Synchronization of action potentials during low-magnesium-induced bursting. J Neurophysiol 2015; 113:2461-70. [PMID: 25609103 PMCID: PMC4416584 DOI: 10.1152/jn.00286.2014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Accepted: 01/20/2015] [Indexed: 01/26/2023] Open
Abstract
The relationship between mono- and polysynaptic strength and action potential synchronization was explored using a reduced external Mg(2+) model. Single and dual whole cell patch-clamp recordings were performed in hippocampal cultures in three concentrations of external Mg(2+). In decreased Mg(2+) medium, the individual cells transitioned to spontaneous bursting behavior. In lowered Mg(2+) media the larger excitatory synaptic events were observed more frequently and fewer transmission failures occurred, suggesting strengthened synaptic transmission. The event synchronization was calculated for the neural action potentials of the cell pairs, and it increased in media where Mg(2+) concentration was lowered. Analysis of surrogate data where bursting was present, but no direct or indirect connections existed between the neurons, showed minimal action potential synchronization. This suggests the synchronization of action potentials is a product of the strengthening synaptic connections within neuronal networks.
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Affiliation(s)
- Sarah E Johnson
- Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia; and
| | - John L Hudson
- Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia; and
| | - Jaideep Kapur
- Departments of Neurology and Neuroscience, University of Virginia School of Medicine, Charlottesville, Virginia
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Szilágyi T, Száva I, Metz EJ, Mihály I, Orbán-Kis K. Untangling the pathomechanisms of temporal lobe epilepsy—The promise of epileptic biomarkers and novel therapeutic approaches. Brain Res Bull 2014; 109:1-12. [DOI: 10.1016/j.brainresbull.2014.08.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Revised: 08/11/2014] [Accepted: 08/14/2014] [Indexed: 12/30/2022]
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How can we identify ictal and interictal abnormal activity? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 813:3-23. [PMID: 25012363 DOI: 10.1007/978-94-017-8914-1_1] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The International League Against Epilepsy (ILAE) defined a seizure as "a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain." This definition has been used since the era of Hughlings Jackson, and does not take into account subsequent advances made in epilepsy and neuroscience research. The clinical diagnosis of a seizure is empirical, based upon constellations of certain signs and symptoms, while simultaneously ruling out a list of potential imitators of seizures. Seizures should be delimited in time, but the borders of ictal (during a seizure), interictal (between seizures) and postictal (after a seizure) often are indistinct. EEG recording is potentially very helpful for confirmation, classification and localization. About a half-dozen common EEG patterns are encountered during seizures. Clinicians rely on researchers to answer such questions as why seizures start, spread and stop, whether seizures involve increased synchrony, the extent to which extra-cortical structures are involved, and how to identify the seizure network and at what points interventions are likely to be helpful. Basic scientists have different challenges in use of the word 'seizure,' such as distinguishing seizures from normal behavior, which would seem easy but can be very difficult because some rodents have EEG activity during normal behavior that resembles spike-wave discharge or bursts of rhythmic spiking. It is also important to define when a seizure begins and stops so that seizures can be quantified accurately for pre-clinical studies. When asking what causes seizures, the transition to a seizure and differentiating the pre-ictal, ictal and post-ictal state is also important because what occurs before a seizure could be causal and may warrant further investigation for that reason. These and other issues are discussed by three epilepsy researchers with clinical and basic science expertise.
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Blauwblomme T, Jiruska P, Huberfeld G. Mechanisms of ictogenesis. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2014; 114:155-85. [PMID: 25078502 DOI: 10.1016/b978-0-12-418693-4.00007-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Epilepsy is a paroxysmal condition characterized by repeated transient seizures separated by longer interictal periods. Ictogenesis describes the processes of transition from the interictal state to a seizure. The processes include a preictal state, with specific clinical signs and a distinct electrophysiology which may provide opportunities to anticipate, or even prevent, seizures. Biological mechanisms of ictogenesis remain poorly understood and may vary between conditions/syndromes. We review here ictogenic processes including the involvement of pyramidal cells, interneurons and astrocytes, GABAergic and glutamatergic signaling, and ionic perturbations. Our review suggests that specific excitatory influences at the transition to an ictal event include (1) GABA receptor activation with a neuronal Cl(-) load and (2) a transient increase in external K(+).
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Affiliation(s)
- Thomas Blauwblomme
- Neurosurgery Unit, Hopital Necker-Enfants Malades, APHP, Paris, France; Université Paris Descartes, Paris, France; INSERM U1129-Infantile Epilepsies and Brain Plasticity, Paris, France; University Paris Descartes, PRES Sorbonne Paris Cité, Paris, France; CEA, Gif sur Yvette, France
| | - 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
| | - Gilles Huberfeld
- INSERM U1129-Infantile Epilepsies and Brain Plasticity, Paris, France; University Paris Descartes, PRES Sorbonne Paris Cité, Paris, France; CEA, Gif sur Yvette, France; Clinical Neurophysiology Department, CHU Pitié-Salpêtrière, APHP, Paris, France; Université Pierre et Marie Curie, Paris, France.
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Grasse DW, Karunakaran S, Moxon KA. Neuronal synchrony and the transition to spontaneous seizures. Exp Neurol 2013; 248:72-84. [DOI: 10.1016/j.expneurol.2013.05.004] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Revised: 04/30/2013] [Accepted: 05/07/2013] [Indexed: 11/28/2022]
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Kitchigina V, Popova I, Sinelnikova V, Malkov A, Astasheva E, Shubina L, Aliev R. Disturbances of septohippocampal theta oscillations in the epileptic brain: Reasons and consequences. Exp Neurol 2013; 247:314-27. [DOI: 10.1016/j.expneurol.2013.01.029] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Revised: 01/21/2013] [Accepted: 01/28/2013] [Indexed: 01/05/2023]
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Huberfeld G, Le Duigou C, Le Van Quyen M, Navarro V, Baulac M, Miles R. The paradox of the paroxysm: can seizure precipitants help explain human ictogenesis? Neuroscientist 2013; 19:523-40. [PMID: 23881918 DOI: 10.1177/1073858413497430] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
An epileptic brain is permanently in a diseased state, but seizures occur rarely and without warning. Here we examine this paradox, common to paroxysmal diseases. We review the problem in the context of the prototypic acquired epilepsies of the medial temporal lobe. We ask how an epileptic temporal lobe differs from a healthy one and examine biological mechanisms that may explain the transition to seizure. Attempts to predict seizure timing from analyses of brain electrical activity suggest that the neurological processes involved may be initiated significantly before a seizure. Furthermore, whereas seizures are said to occur without warning, some patients say they know when a seizure is imminent. Several factors, including sleep deprivation, oscillations in hormonal levels, or withdrawal from drugs, increase the probability of a seizure. We ask whether these seizure precipitants might act through common neuronal mechanisms. Several precipitating factors seem to involve relief from a neurosteroid modulation of gamma-amino butyric acid receptor type A (GABAA) receptors. We propose tests of this hypothesis.
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Affiliation(s)
- Gilles Huberfeld
- INSERM U975, Institut du Cerveau et la Moëlle Epinière, Paris, France
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Žiburkus J, Cressman JR, Schiff SJ. Seizures as imbalanced up states: excitatory and inhibitory conductances during seizure-like events. J Neurophysiol 2012; 109:1296-306. [PMID: 23221405 DOI: 10.1152/jn.00232.2012] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Precisely timed and dynamically balanced excitatory (E) and inhibitory (I) conductances underlie the basis of neural network activity. Normal E/I balance is often shifted in epilepsy, resulting in neuronal network hyperexcitability and recurrent seizures. However, dynamics of the actual excitatory and inhibitory synaptic conductances (ge and gi, respectively) during seizures remain unknown. To study the dynamics of E and I network balance, we calculated ge and gi during the initiation, body, and termination of seizure-like events (SLEs) in the rat hippocampus in vitro. Repetitive emergent SLEs in 4-aminopyridine (100 μM) and reduced extracellular magnesium (0.6 mM) were recorded in the identified CA1 pyramidal cells (PC) and oriens-lacunosum moleculare (O-LM) interneurons. Calculated ge/gi ratio dynamics showed that the initiation stage of the SLEs was dominated by inhibition in the PCs and was more balanced in the O-LM cells. During the body of the SLEs, the balance shifted toward excitation, with ge and gi peaking in both cell types at nearly the same time. In the termination phase, PCs were again dominated by inhibition, whereas O-LM cells experienced persistent excitatory synaptic barrage. In this way, increased excitability of interneurons may play roles in both seizure initiation (žiburkus J, Cressman JR, Barreto E, Schiff SJ. J Neurophysiol 95: 3948-3954, 2006) and in their termination. Overall, SLE stages can be characterized in PC and O-LM cells by dynamically distinct changes in the balance of ge and gi, where a temporal sequence of imbalance shifts with the changing firing patterns of the cellular subtypes comprising the hyperexcitable microcircuits.
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Affiliation(s)
- Jokubas Žiburkus
- Department of Biology and Biochemistry, University of Houston, Houston, TX, USA.
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Cammarota M, Losi G, Chiavegato A, Zonta M, Carmignoto G. Fast spiking interneuron control of seizure propagation in a cortical slice model of focal epilepsy. J Physiol 2012. [PMID: 23207591 DOI: 10.1113/jphysiol.2012.238154] [Citation(s) in RCA: 112] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
In different animal models of focal epilepsy, seizure-like ictal discharge propagation is transiently opposed by feedforward inhibition. The specific cellular source of this signal and the mechanism by which inhibition ultimately becomes ineffective are, however, undefined. We used a brain slice model to study how focal ictal discharges that were repetitively evoked from the same site, and at precise times, propagate across the cortex. We used Ca(2+) imaging and simultaneous single/dual cell recordings from pyramidal neurons (PyNs) and different classes of interneurons in rodents, including G42 and GIN transgenic mice expressing the green fluorescence protein in parvalbumin (Pv)-fast spiking (FS) and somatostatin (Som) interneurons, respectively. We found that these two classes of interneurons fired intensively shortly after ictal discharge generation at the focus. The inhibitory barrages that were recorded in PyNs occurred in coincidence with Pv-FS, but not with Som interneuron burst discharges. Furthermore, the strength of inhibitory barrages increased or decreased in parallel with increased or decreased firing in Pv-FS interneurons but not in Som interneurons. A firing impairment of Pv-FS interneurons caused by a membrane depolarization was found to precede ictal discharge onset in neighbouring pyramidal neurons. This event may account for the collapse of local inhibition that allows spatially defined clusters of PyNs to be recruited into propagating ictal discharges. Our study demonstrates that Pv-FS interneurons are a major source of the inhibitory barrages that oppose ictal discharge propagation and raises the possibility that targeting Pv-FS interneurons represents a new therapeutic strategy to prevent the generalization of human focal seizures.
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Affiliation(s)
- Mario Cammarota
- Institute of Neuroscience, National Research Council and Department of Biomedical Sciences, University of Padova, Padova, Italy
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Lewin N, Aksay E, Clancy CE. Computational modeling reveals dendritic origins of GABA(A)-mediated excitation in CA1 pyramidal neurons. PLoS One 2012; 7:e47250. [PMID: 23071770 PMCID: PMC3470566 DOI: 10.1371/journal.pone.0047250] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Accepted: 09/11/2012] [Indexed: 12/16/2022] Open
Abstract
GABA is the key inhibitory neurotransmitter in the adult central nervous system, but in some circumstances can lead to a paradoxical excitation that has been causally implicated in diverse pathologies from endocrine stress responses to diseases of excitability including neuropathic pain and temporal lobe epilepsy. We undertook a computational modeling approach to determine plausible ionic mechanisms of GABA(A)-dependent excitation in isolated post-synaptic CA1 hippocampal neurons because it may constitute a trigger for pathological synchronous epileptiform discharge. In particular, the interplay intracellular chloride accumulation via the GABA(A) receptor and extracellular potassium accumulation via the K/Cl co-transporter KCC2 in promoting GABA(A)-mediated excitation is complex. Experimentally it is difficult to determine the ionic mechanisms of depolarizing current since potassium transients are challenging to isolate pharmacologically and much GABA signaling occurs in small, difficult to measure, dendritic compartments. To address this problem and determine plausible ionic mechanisms of GABA(A)-mediated excitation, we built a detailed biophysically realistic model of the CA1 pyramidal neuron that includes processes critical for ion homeostasis. Our results suggest that in dendritic compartments, but not in the somatic compartments, chloride buildup is sufficient to cause dramatic depolarization of the GABA(A) reversal potential and dominating bicarbonate currents that provide a substantial current source to drive whole-cell depolarization. The model simulations predict that extracellular K(+) transients can augment GABA(A)-mediated excitation, but not cause it. Our model also suggests the potential for GABA(A)-mediated excitation to promote network synchrony depending on interneuron synapse location - excitatory positive-feedback can occur when interneurons synapse onto distal dendritic compartments, while interneurons projecting to the perisomatic region will cause inhibition.
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Affiliation(s)
- Naomi Lewin
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, New York, United States of America
- Tri-Institutional MD-PhD Program, Physiology, Biophysics and Systems Biology Graduate Program, Department of Pharmacology, University of California Davis, Davis, California, United States of America
| | - Emre Aksay
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Colleen E. Clancy
- Tri-Institutional MD-PhD Program, Physiology, Biophysics and Systems Biology Graduate Program, Department of Pharmacology, University of California Davis, Davis, California, United States of America
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Albus K, Wahab A, Heinemann U. Primary afterdischarge in organotypic hippocampal slice cultures: Effects of standard antiepileptic drugs. Epilepsia 2012; 53:1928-36. [DOI: 10.1111/j.1528-1167.2012.03597.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Pyramidal cells accumulate chloride at seizure onset. Neurobiol Dis 2012; 47:358-66. [PMID: 22677032 DOI: 10.1016/j.nbd.2012.05.016] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2012] [Revised: 05/21/2012] [Accepted: 05/24/2012] [Indexed: 01/09/2023] Open
Abstract
Seizures are thought to originate from a failure of inhibition to quell hyperactive neural circuits, but the nature of this failure remains unknown. Here we combine high-speed two-photon imaging with electrophysiological recordings to directly evaluate the interaction between populations of interneurons and principal cells during the onset of seizure-like activity in mouse hippocampal slices. Both calcium imaging and dual patch clamp recordings reveal that in vitro seizure-like events (SLEs) are preceded by pre-ictal bursts of activity in which interneurons predominate. Corresponding changes in intracellular chloride concentration were observed in pyramidal cells using the chloride indicator Clomeleon. These changes were measurable at SLE onset and became very large during the SLE. Pharmacological manipulation of GABAergic transmission, either by blocking GABA(A) receptors or by hyperpolarizing the GABA(A) reversal potential, converted SLEs to short interictal-like bursts. Together, our results support a model in which pre-ictal GABA(A) receptor-mediated chloride influx shifts E(GABA) to produce a positive feedback loop that contributes to the initiation of seizure activity.
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Hazra A, Rosenbaum R, Bodmann B, Cao S, Josić K, Žiburkus J. β-Adrenergic modulation of spontaneous spatiotemporal activity patterns and synchrony in hyperexcitable hippocampal circuits. J Neurophysiol 2012; 108:658-71. [PMID: 22496530 DOI: 10.1152/jn.00708.2011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
A description of healthy and pathological brain dynamics requires an understanding of spatiotemporal patterns of neural activity and characteristics of its propagation between interconnected circuits. However, the structure and modulation of the neural activation maps underlying these patterns and their propagation remain elusive. We investigated effects of β-adrenergic receptor (β-AR) stimulation on the spatiotemporal characteristics of emergent activity in rat hippocampal circuits. Synchronized epileptiform-like activity, such as interictal bursts (IBs) and ictal-like events (ILEs), were evoked by 4-aminopyridine (4-AP), and their dynamics were studied using a combination of electrophysiology and fast voltage-sensitive dye imaging. Dynamic characterization of the spontaneous IBs showed that they originated in dentate gyrus/CA3 border and propagated toward CA1. To determine how β-AR modulates spatiotemporal characteristics of the emergent IBs, we used the β-AR agonist isoproterenol (ISO). ISO significantly reduced the spatiotemporal extent and propagation velocity of the IBs and significantly altered network activity in the 1- to 20-Hz range. Dual whole cell recordings of the IBs in CA3/CA1 pyramidal cells and optical analysis of those regions showed that ISO application reduced interpyramidal and interregional synchrony during the IBs. In addition, ISO significantly reduced duration not only of the shorter duration IBs but also the prolonged ILEs in 4-AP. To test whether the decrease in ILE duration was model dependent, we used a different hyperexcitability model, zero magnesium (0 Mg(2+)). Prolonged ILEs were readily formed in 0 Mg(2+), and addition of ISO significantly reduced their durations. Taken together, these novel results provide evidence that β-AR activation dynamically reshapes the spatiotemporal activity patterns in hyperexcitable circuits by altering network rhythmogenesis, propagation velocity, and intercellular/regional synchronization.
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Affiliation(s)
- Anupam Hazra
- Department of Biology and Biochemistry, University of Houston, Houston, TX 77204-5001, USA
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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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Abstract
A variety of epileptic seizure models have shown that activation of glutamatergic pyramidal cells is usually required for rhythm generation and/or synchronization in hippocampal seizure-like oscillations in vitro. However, it still remains unclear whether GABAergic interneurons may be able to drive the seizure-like oscillations without glutamatergic transmission. Here, we found that electrical stimulation in rat hippocampal CA1 slices induced a putative prototype of seizure-like oscillations ("prototypic afterdischarge," 1.8-3.8 Hz) in mature pyramidal cells and interneurons in the presence of ionotropic glutamate receptor antagonists. The prototypic afterdischarge was abolished by GABA(A) receptor antagonists or gap junction blockers, but not by a metabotropic glutamate receptor antagonist or a GABA(B) receptor antagonist. Gramicidin-perforated patch-clamp and voltage-clamp recordings revealed that pyramidal cells were depolarized and frequently excited directly through excitatory GABAergic transmissions in each cycle of the prototypic afterdischarge. Interneurons that were actively spiking during the prototypic afterdischarge were mostly fast-spiking (FS) interneurons located in the strata oriens and pyramidale. Morphologically, these interneurons that might be "potential seizure drivers" included basket, chandelier, and bistratified cells. Furthermore, they received direct excitatory GABAergic input during the prototypic afterdischarge. The O-LM cells and most of the interneurons in the strata radiatum and lacunosum moleculare were not essential for the generation of prototypic afterdischarge. The GABA-mediated prototypic afterdischarge was observed later than the third postnatal week in the rat hippocampus. Our results suggest that an FS interneuron network alone can drive the prototypic form of electrically induced seizure-like oscillations through their excitatory GABAergic transmissions and presumably through gap junction-mediated communications.
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Molaee-Ardekani B, Benquet P, Bartolomei F, Wendling F. Computational modeling of high-frequency oscillations at the onset of neocortical partial seizures: From ‘altered structure’ to ‘dysfunction’. Neuroimage 2010; 52:1109-22. [PMID: 20034581 DOI: 10.1016/j.neuroimage.2009.12.049] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2009] [Revised: 12/09/2009] [Accepted: 12/10/2009] [Indexed: 11/29/2022] Open
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Hama-Tomioka K, Kinoshita H, Azma T, Nakahata K, Matsuda N, Hatakeyama N, Kikuchi H, Hatano Y. The Role of 20-Hydroxyeicosatetraenoic Acid in Cerebral Arteriolar Constriction and the Inhibitory Effect of Propofol. Anesth Analg 2009; 109:1935-42. [DOI: 10.1213/ane.0b013e3181bd1ebe] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Lasztóczi B, Nyitrai G, Héja L, Kardos J. Synchronization of GABAergic Inputs to CA3 Pyramidal Cells Precedes Seizure-Like Event Onset in Juvenile Rat Hippocampal Slices. J Neurophysiol 2009; 102:2538-53. [DOI: 10.1152/jn.91318.2008] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Here we address how dynamics of glutamatergic and GABAergic synaptic input to CA3 pyramidal cells contribute to spontaneous emergence and evolution of recurrent seizure-like events (SLEs) in juvenile (P10-13) rat hippocampal slices bathed in low-[Mg2+] artificial cerebrospinal fluid. In field potential recordings from the CA3 pyramidal layer, a short epoch of high-frequency oscillation (HFO; 400–800 Hz) was observed during the first 10 ms of SLE onset. GABAergic synaptic input currents to CA3 pyramidal cells were synchronized and coincided with HFO, whereas the glutamatergic input lagged by ∼10 ms. If the intracellular [Cl−] remained unperturbed (cell-attached recordings) or was set high with whole cell electrode solution, CA3 pyramidal cell firing peaked with HFO and GABAergic input. By contrast, with low intracellular [Cl−], spikes of CA3 pyramidal cells lagged behind HFO and GABAergic input. This temporal arrangement of HFO, synaptic input sequence, synchrony of GABAergic currents, and pyramidal cell firing emerged gradually with preictal discharges until the SLE onset. Blockade of GABAA receptor-mediated currents by picrotoxin reduced the inter-SLE interval and the number of preictal discharges and did not block recurrent SLEs. Our data suggest that dynamic changes of the functional properties of GABAergic input contribute to ictogenesis and GABAergic and glutamatergic inputs are both excitatory at the instant of SLE onset. At the SLE onset GABAergic input contributes to synchronization and recruitment of pyramidal cells. We conjecture that this network state is reached by an activity-dependent shift in GABA reversal potential during the preictal phase.
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Affiliation(s)
- Bálint Lasztóczi
- Department of Neurochemistry, Institute of Biomolecular Chemistry, Chemical Research Center, Hungarian Academy of Sciences, Budapest, Hungary
| | - Gabriella Nyitrai
- Department of Neurochemistry, Institute of Biomolecular Chemistry, Chemical Research Center, Hungarian Academy of Sciences, Budapest, Hungary
| | - László Héja
- Department of Neurochemistry, Institute of Biomolecular Chemistry, Chemical Research Center, Hungarian Academy of Sciences, Budapest, Hungary
| | - Julianna Kardos
- Department of Neurochemistry, Institute of Biomolecular Chemistry, Chemical Research Center, Hungarian Academy of Sciences, Budapest, Hungary
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de Curtis M, Gnatkovsky V. Reevaluating the mechanisms of focal ictogenesis: The role of low-voltage fast activity. Epilepsia 2009; 50:2514-25. [PMID: 19674056 DOI: 10.1111/j.1528-1167.2009.02249.x] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The mechanisms that control the transition into a focal seizure are still uncertain. The introduction of presurgical intracranial recordings to localize the epileptogenic zone in patients with drug-resistant focal epilepsies opened a new window to the interpretation of seizure generation (ictogenesis). One of the most frequent focal patterns observed with intracranial electrodes at seizure onset is characterized by low-voltage fast activity in the beta-gamma range that may or may not be preceded by changes of ongoing interictal activities. In the present commentary, the mechanisms of generation of focal seizures are reconsidered, focusing on low-voltage fast activity patterns. Experimental findings on models of temporal lobe seizures support the view that the low-voltage fast activity observed at seizure onset is associated with reinforcement and synchronization of inhibitory networks. A minor role for the initiation of the ictal pattern is played by principal neurons that are progressively recruited with a delay, when inhibition declines and synchronous high-voltage discharges ensue. The transition from inhibition into excitatory recruitment is probably mediated by local increase in potassium concentration associated with synchronized interneuronal firing. These findings challenge the classical theory that proposes an increment of excitation and/or a reduction of inhibition as a cause for the transition to seizure in focal epilepsies. A new definition of ictogenesis mechanisms, as herewith hypothesized, might possibly help to develop new therapeutic strategies for focal epilepsies.
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Affiliation(s)
- Marco de Curtis
- Unit of Experimental Neurophysiology and Epileptology, Fondazione Istituto Neurologico Carlo Besta, Milano, Italy.
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36
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Ullah G, Cressman JR, Barreto E, Schiff SJ. The influence of sodium and potassium dynamics on excitability, seizures, and the stability of persistent states. II. Network and glial dynamics. J Comput Neurosci 2008; 26:171-83. [PMID: 19083088 DOI: 10.1007/s10827-008-0130-6] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2008] [Revised: 10/17/2008] [Accepted: 11/24/2008] [Indexed: 11/28/2022]
Abstract
In these companion papers, we study how the interrelated dynamics of sodium and potassium affect the excitability of neurons, the occurrence of seizures, and the stability of persistent states of activity. We seek to study these dynamics with respect to the following compartments: neurons, glia, and extracellular space. We are particularly interested in the slower time-scale dynamics that determine overall excitability, and set the stage for transient episodes of persistent oscillations, working memory, or seizures. In this second of two companion papers, we present an ionic current network model composed of populations of Hodgkin-Huxley type excitatory and inhibitory neurons embedded within extracellular space and glia, in order to investigate the role of micro-environmental ionic dynamics on the stability of persistent activity. We show that these networks reproduce seizure-like activity if glial cells fail to maintain the proper micro-environmental conditions surrounding neurons, and produce several experimentally testable predictions. Our work suggests that the stability of persistent states to perturbation is set by glial activity, and that how the response to such perturbations decays or grows may be a critical factor in a variety of disparate transient phenomena such as working memory, burst firing in neonatal brain or spinal cord, up states, seizures, and cortical oscillations.
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Affiliation(s)
- Ghanim Ullah
- Center for Neural Engineering, Department of Engineering Science and Mechanics, The Pennsylvania State University, 212 Earth Engineering Science Building, University Park, PA 16802, USA.
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37
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Gnatkovsky V, Librizzi L, Trombin F, de Curtis M. Fast activity at seizure onset is mediated by inhibitory circuits in the entorhinal cortex in vitro. Ann Neurol 2008; 64:674-86. [DOI: 10.1002/ana.21519] [Citation(s) in RCA: 160] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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38
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Isomura Y, Fujiwara-Tsukamoto Y, Takada M. A network mechanism underlying hippocampal seizure-like synchronous oscillations. Neurosci Res 2008; 61:227-33. [DOI: 10.1016/j.neures.2008.04.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2008] [Revised: 04/04/2008] [Accepted: 04/07/2008] [Indexed: 10/22/2022]
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39
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Balanced excitatory and inhibitory inputs to cortical neurons decouple firing irregularity from rate modulations. J Neurosci 2008; 27:13802-12. [PMID: 18077692 DOI: 10.1523/jneurosci.2452-07.2007] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In vivo cortical neurons are known to exhibit highly irregular spike patterns. Because the intervals between successive spikes fluctuate greatly, irregular neuronal firing makes it difficult to estimate instantaneous firing rates accurately. If, however, the irregularity of spike timing is decoupled from rate modulations, the estimate of firing rate can be improved. Here, we introduce a novel coding scheme to make the firing irregularity orthogonal to the firing rate in information representation. The scheme is valid if an interspike interval distribution can be well fitted by the gamma distribution and the firing irregularity is constant over time. We investigated in a computational model whether fluctuating external inputs may generate gamma process-like spike outputs, and whether the two quantities are actually decoupled. Whole-cell patch-clamp recordings of cortical neurons were performed to confirm the predictions of the model. The output spikes were well fitted by the gamma distribution. The firing irregularity remained approximately constant regardless of the firing rate when we injected a balanced input, in which excitatory and inhibitory synapses are activated concurrently while keeping their conductance ratio fixed. The degree of irregular firing depended on the effective reversal potential set by the balance between excitation and inhibition. In contrast, when we modulated conductances out of balance, the irregularity varied with the firing rate. These results indicate that the balanced input may improve the efficiency of neural coding by clamping the firing irregularity of cortical neurons. We demonstrate how this novel coding scheme facilitates stimulus decoding.
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Derchansky M, Jahromi SS, Mamani M, Shin DS, Sik A, Carlen PL. Transition to seizures in the isolated immature mouse hippocampus: a switch from dominant phasic inhibition to dominant phasic excitation. J Physiol 2007; 586:477-94. [PMID: 17991696 DOI: 10.1113/jphysiol.2007.143065] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The neural dynamics and mechanisms responsible for the transition from the interictal to the ictal state (seizures) are unresolved questions in epilepsy. It has been suggested that a shift from inhibitory to excitatory GABAergic drive can promote seizure generation. In this study, we utilized an experimental model of temporal lobe epilepsy which produces recurrent seizure-like events in the isolated immature mouse hippocampus (P8-16), perfused with low magnesium ACSF, to investigate the cellular dynamics of seizure transition. Whole-cell and perforated patch recordings from CA1 pyramidal cells and from fast- and non-fast-spiking interneurons in the CA1 stratum oriens hippocampal region showed a change in intracellular signal integration during the transition period, starting with dominant phasic inhibitory synaptic input, followed by dominant phasic excitation prior to a seizure. Efflux of bicarbonate ions through the GABA A receptor did not fully account for this excitation and GABAergic excitation via reversed IPSPs was also excluded as the prime mechanism generating the dominant excitation, since somatic and dendritic GABA A responses to externally applied muscimol remained hyperpolarizing throughout the transition period. In addition, abolishing EPSPs in a single neuron by intracellularly injected QX222, revealed that inhibitory synaptic drive was maintained throughout the entire transition period. We suggest that rather than a major shift from inhibitory to excitatory GABAergic drive prior to seizure onset, there is a change in the interaction between afferent synaptic inhibition, and afferent and intrinsic excitatory processes in pyramidal neurons and interneurons, with maintained inhibition and increasing, entrained 'overpowering' excitation during the transition to seizure.
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Affiliation(s)
- M Derchansky
- Division of Cellular and Molecular Biology, Toronto Western Hospital, 399 Bathurst St, 12-413, Toronto, Ontario, Canada M5T2S8
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41
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Tsubo Y, Takada M, Reyes AD, Fukai T. Layer and frequency dependencies of phase response properties of pyramidal neurons in rat motor cortex. Eur J Neurosci 2007; 25:3429-41. [PMID: 17553012 DOI: 10.1111/j.1460-9568.2007.05579.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
It is postulated that synchronous firing of cortical neurons plays an active role in cognitive functions of the brain. An important issue is whether pyramidal neurons in different cortical layers exhibit similar tendencies to synchronise. To address this issue, we performed intracellular and whole-cell recordings of regular-spiking pyramidal neurons in slice preparations of the rat motor cortex (18-45 days old) and analysed the phase response curves of these pyramidal neurons in layers 2/3 and 5. The phase response curve represents how an external stimulus affects the timing of spikes immediately after the stimulus in repetitively firing neurons. The phase response curve can be classified into two categories, type 1 (the spike is always advanced) and type 2 (the spike is advanced or delayed depending on the stimulus phase), and are important determinants of whether or not rhythmic synchronization of neuron pairs occurs. We found that pyramidal neurons in layer 2/3 tend to display type-2 phase response curves whereas those in layer 5 tend to exhibit type-1 phase response curves. The differences were prominent particularly in the gamma-frequency range (20-45 Hz). Our results imply that the layer-2/3 pyramidal neurons, when coupled mutually through fast excitatory synapses, may exhibit a much stronger tendency for rhythmic synchronization than layer-5 neurons in the gamma-frequency range.
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Affiliation(s)
- Yasuhiro Tsubo
- Laboratory for Neural Circuit Theory, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
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42
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Spampanato J, Mody I. Spike Timing of Lacunosom-Moleculare Targeting Interneurons and CA3 Pyramidal Cells During High-Frequency Network Oscillations In Vitro. J Neurophysiol 2007; 98:96-104. [PMID: 17475718 DOI: 10.1152/jn.00188.2007] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Network activity in the 200- to 600-Hz range termed high-frequency oscillations (HFOs) has been detected in epileptic tissue from both humans and rodents and may underlie the mechanism of epileptogenesis in experimental rodent models. Slower network oscillations including theta and gamma oscillations as well as ripples are generated by the complex spike timing and interactions between interneurons and pyramidal cells of the hippocampus. We determined the activity of CA3 pyramidal cells, stratum oriens lacunosum-moleculare (O-LM) and s. radiatum lacunosum-moleculare (R-LM) interneurons during HFO in the in vitro low-Mg2+ model of epileptiform activity in GIN mice. In these animals, interneurons can be identified prior to cell-attached recordings by the expression of green-fluorescent protein (GFP). Simultaneous local field potential recordings from s. pyramidale and on-cell recordings of individual interneurons and principal cells revealed three primary firing behaviors of the active cells: 36% of O-LM interneurons and 60% of pyramidal cells fired action potentials at high frequencies during the HFO. R-LM interneurons were biphasic in that they fired at high frequency at the beginning of the HFO but stopped firing before its end. When considering only the highest frequency component of the oscillations most pyramidal cells fired on the rising phase of the oscillation. These data provide evidence for functional distinction during HFOs within otherwise homogeneous groups of O-LM interneurons and pyramidal cells.
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Affiliation(s)
- Jay Spampanato
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095-7335, USA
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43
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Fujiwara-Tsukamoto Y, Isomura Y, Imanishi M, Fukai T, Takada M. Distinct types of ionic modulation of GABA actions in pyramidal cells and interneurons during electrical induction of hippocampal seizure-like network activity. Eur J Neurosci 2007; 25:2713-25. [PMID: 17459104 DOI: 10.1111/j.1460-9568.2007.05543.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
It has recently been shown that electrical stimulation in normal extracellular fluid induces seizure-like afterdischarge activity that is always preceded by GABA-dependent slow depolarization. These afterdischarge responses are synchronous among mature hippocampal neurons and driven by excitatory GABAergic input. However, the differences in the mechanisms whereby the GABAergic signals in pyramidal cells and interneurons are transiently converted from hyperpolarizing to depolarizing (and even excitatory) have remained unclear. To clarify the network mechanisms underlying this rapid GABA conversion that induces afterdischarges, we examined the temporal changes in GABAergic responses in pyramidal cells and/or interneurons of the rat hippocampal CA1 area in vitro. The extents of slow depolarization and GABA conversion were much larger in the pyramidal cell group than in any group of interneurons. Besides GABA(A) receptor activation, neuronal excitation by ionotropic glutamate receptors enhanced GABA conversion in the pyramidal cells and consequent induction of afterdischarge. The slow depolarization was confirmed to consist of two distinct phases; an early phase that depended primarily on GABA(A)-mediated postsynaptic Cl- accumulation, and a late phase that depended on extracellular K+ accumulation, both of which were enhanced by glutamatergic neuron excitation. Moreover, extracellular K+ accumulation augmented each oscillatory response of the afterdischarge, probably by further Cl- accumulation through K+-coupled Cl- transporters. Our findings suggest that the GABA reversal potential may be elevated above their spike threshold predominantly in the pyramidal cells by biphasic Cl- intrusion during the slow depolarization in GABA- and glutamate-dependent fashion, leading to the initiation of seizure-like epileptiform activity.
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Affiliation(s)
- Yoko Fujiwara-Tsukamoto
- Department of System Neuroscience, Tokyo Metropolitan Institute for Neuroscience, 2-6 Musashidai, Fuchu, Tokyo 183-8526, Japan
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44
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Stief F, Zuschratter W, Hartmann K, Schmitz D, Draguhn A. Enhanced synaptic excitation-inhibition ratio in hippocampal interneurons of rats with temporal lobe epilepsy. Eur J Neurosci 2007; 25:519-28. [PMID: 17284194 DOI: 10.1111/j.1460-9568.2006.05296.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A common feature of all epileptic syndromes is the repetitive occurrence of pathological patterns of synchronous neuronal activity, usually combined with increased neuronal discharge rates. Inhibitory interneurons of the hippocampal formation control both neuronal synchronization as well as the global level of activity and are therefore of crucial importance for epilepsy. Recent evidence suggests that changes in synaptic inhibition during temporal lobe epilepsy are rather specific, resulting from selective death or alteration of interneurons in specific hippocampal layers. Hence, epilepsy-induced changes have to be analysed separately for different types of interneurons. Here, we focused on GABAergic neurons located at the border between stratum radiatum and stratum lacunosum-moleculare of hippocampal area CA1 (SRL interneurons), which are included in feedforward inhibitory circuits. In chronically epileptic rats at 6-8 months after pilocarpine-induced status epilepticus, frequencies of spontaneous and miniature inhibitory postsynaptic currents were reduced, yielding an almost three-fold increase in excitation-inhibition ratio. Consistently, action potential frequency of SRL interneurons was about two-fold enhanced. Morphological alterations of the interneurons indicate that these functional changes were accompanied by remodelling of the local network, probably resulting in a loss of functional inhibitory synapses without conceivable cell death. Our data indicate a strong increase in activity of interneurons in dendritic layers of the chronically epileptic CA1 region. This alteration may enhance feedforward inhibition and rhythmogenesis and--together with specific changes in other interneurons--contribute to seizure susceptibility and pathological synchronization.
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Affiliation(s)
- F Stief
- Neurowissenschaftliches Forschungszentrum der Charité, Humboldt-University Berlin, Germany
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45
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Li X, Zhou W, Zeng S, Liu M, Luo Q. Long-term recording on multi-electrode array reveals degraded inhibitory connection in neuronal network development. Biosens Bioelectron 2007; 22:1538-43. [PMID: 16829068 DOI: 10.1016/j.bios.2006.05.030] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2006] [Revised: 05/22/2006] [Accepted: 05/31/2006] [Indexed: 11/16/2022]
Abstract
Spontaneous neuronal activity plays an important role in development. However, the mechanism that underlies the long-term spontaneous developmental change of cultured neuronal networks in vitro is not well understood. To investigate the contribution of inhibitory and excitatory connections to the development of neuronal networks, dissociated neurons from an embryonic rat hippocampal formation were cultured on a multi-electrode array plate and spontaneous activities were recorded by multi-channel system. These spontaneous activities were compared to bicuculline-induced firings, which were recorded by 60 electrodes simultaneously from 1 to 14 weeks in vitro (WIV). The phenomena showed that the spontaneous firing activities changed from an initial pattern of synchronized bursts to a later pattern of high frequency random spikes. The bicuculline-induced firing activities transformed from a pattern of synchronized bursts throughout all active sites in 3 WIV, to a pattern of local synchronized or random spikes appearing in the intervals of synchronized bursts after 11 WIV, while the firing rate hardly changed. Kynurenic acid, a broad-spectrum glutamate receptor antagonist, blocked all activities while CNQX inhibited only the local synchronized or random spikes. These suggest that the inhibitory connection was age-dependent degraded in vitro and the developmental spontaneous firing pattern was built by the homeostatic balance of the excitatory-inhibitory connection networks. Long-term cultures on MEA provided a useful tool to measure the relationship between spontaneous developmental change and pharmacological influence in vitro.
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Affiliation(s)
- Xiangning Li
- The Key Laboratory of Biomedical Photonics of Ministry of Education-Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
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46
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Kramer MA, Szeri AJ, Sleigh JW, Kirsch HE. Mechanisms of seizure propagation in a cortical model. J Comput Neurosci 2006; 22:63-80. [PMID: 16998642 DOI: 10.1007/s10827-006-9508-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2006] [Revised: 06/13/2006] [Accepted: 06/16/2006] [Indexed: 11/30/2022]
Abstract
We consider a mathematical model of mesoscopic human cortical ictal electrical activity. We compare the model results with ictal electrocortical data recorded from three human subjects and show how the two agree. We determine that, in the model system, seizures result from increased connectivity between excitatory and inhibitory cell populations, or from decreased connectivity within either excitatory or inhibitory cell populations. We compare the model results with the disinhibition and 4-AP models of epilepsy and suggest how the model may guide the development of new anticonvulsant therapies.
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Affiliation(s)
- Mark A Kramer
- Applied Science and Technology Graduate Group, University of California, Berkeley, CA 94720-1740, USA
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47
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Žiburkus J, Cressman JR, Barreto E, Schiff. SJ. Interneuron and pyramidal cell interplay during in vitro seizure-like events. J Neurophysiol 2006; 95:3948-54. [PMID: 16554499 PMCID: PMC1469233 DOI: 10.1152/jn.01378.2005] [Citation(s) in RCA: 192] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Excitatory and inhibitory (EI) interactions shape network activity. However, little is known about the EI interactions in pathological conditions such as epilepsy. To investigate EI interactions during seizure-like events (SLEs), we performed simultaneous dual and triple whole cell and extracellular recordings in pyramidal cells and oriens interneurons in rat hippocampal CA1. We describe a novel pattern of interleaving EI activity during spontaneous in vitro SLEs generated by the potassium channel blocker 4-aminopyridine in the presence of decreased magnesium. Interneuron activity was increased during interictal periods. During ictal discharges interneurons entered into long-lasting depolarization block (DB) with suppression of spike generation; simultaneously, pyramidal cells produced spike trains with increased frequency (6-14 Hz) and correlation. After this period of runaway excitation, interneuron postictal spiking resumed and pyramidal cells became progressively quiescent. We performed correlation measures of cell-pair interactions using either the spikes alone or the subthreshold postsynaptic interspike signals. EE spike correlation was notably increased during interneuron DB, whereas subthreshold EE correlation decreased. EI spike correlations increased at the end of SLEs, whereas II subthreshold correlations increased during DB. Our findings underscore the importance of complex cell-type-specific neuronal interactions in the formation of seizure patterns.
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Affiliation(s)
- Jokūbas Žiburkus
- Center for Neural Dynamics, Krasnow Institute
- Contact information Jokūbas Žiburkus, George Mason University, MS2A1, Krasnow Institute, Center for Neural Dynamics, Fairfax, VA 22030, Tel. 703-993-4372/4332, Fax. 703-993-4440, e-mail:
| | | | - Ernest Barreto
- Center for Neural Dynamics, Krasnow Institute
- Department of Physics and Astronomy
- Program in Neuroscience and
| | - Steven J. Schiff.
- Center for Neural Dynamics, Krasnow Institute
- Program in Neuroscience and
- Department of Psychology, George Mason University, MS2A1, Fairfax, VA 22030
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48
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Fujiwara-Tsukamoto Y, Isomura Y, Takada M. Comparable GABAergic Mechanisms of Hippocampal Seizurelike Activity in Posttetanic and Low-Mg2+ Conditions. J Neurophysiol 2006; 95:2013-9. [PMID: 16339009 DOI: 10.1152/jn.00238.2005] [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] [Indexed: 11/22/2022] Open
Abstract
It is known that GABA is a major inhibitory neurotransmitter in mature mammalian brains, but the effect of this substance is sometimes converted into depolarizing or even excitatory when the postsynaptic Cl– concentration becomes high. Recently we have shown that seizurelike afterdischarge induced by tetanic stimulation in normal extracellular fluid (posttetanic afterdischarge) is mediated through GABAergic excitation in mature hippocampal CA1 pyramidal cells. In this study, we examined the possible contribution of similar depolarizing/excitatory GABAergic input to the CA1 pyramidal cells to the seizurelike afterdischarge induced in a low extracellular Mg2+ condition, another experimental model of epileptic seizure activity (low-Mg2+ afterdischarge). Perfusion of the GABAA antagonist bicuculline abolished the low-Mg2+ afterdischarge, but not the interictal-like activity, in most cases. Each oscillatory response during the low-Mg2+ afterdischarge was dependent on Cl– conductance and contained an F–-insensitive depolarizing component in the pyramidal cells, thus indicating that the afterdischarge response may be mediated through both GABAergic and nonGABAergic transmissions. In addition, local GABA application to the recorded cells revealed that GABA responses were indeed depolarizing during the low-Mg2+ afterdischarge. Furthermore, the GABAergic interneurons located in the strata pyramidale and oriens fired in oscillatory cycles more actively than those in other layers of the CA1 region. These results suggest that the depolarizing GABAergic input may facilitate oscillatory synchronization among the hippocampal CA1 pyramidal cells during the low-Mg2+ afterdischarge in a manner similar to the expression of the posttetanic afterdischarge.
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Affiliation(s)
- Yoko Fujiwara-Tsukamoto
- Dept. of System Neuroscience, Tokyo Metropolitan Inst. for Neuroscience, 2-6 Musashidai, Fuchu, Tokyo 183-8526, Japan.
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49
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Watanabe H, Aihara T, Tsukada M. Phase shift of subthreshold theta oscillation in hippocampal CA1 pyramidal cell membrane by excitatory synaptic inputs. Neuroscience 2006; 140:1189-99. [PMID: 16677773 DOI: 10.1016/j.neuroscience.2006.02.085] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2006] [Revised: 02/23/2006] [Accepted: 02/24/2006] [Indexed: 11/23/2022]
Abstract
Hippocampal CA1 neurons receive multiple rhythmical inputs with relatively independent phases during theta activity. It, however, remains to be determined how these multiple rhythmical inputs affect oscillation properties in membrane potential of the CA1 pyramidal cell. In order to investigate oscillation properties in the subthreshold membrane potential, we generated oscillations in the membrane potential of the CA1 pyramidal cells in rat hippocampal slices in vitro with a sinusoidal current injection into the pyramidal soma at theta band frequencies (4-7 Hz), and analyzed effect of rhythmically excitatory synaptic inputs. The Schaffer collaterals were stimulated with a cyclic Gaussian stimulation method, whose pulse intervals were distributed at 10 pulses/cycle (5 cycles/s). We found that the cyclic Gaussian stimulations induced membrane potential oscillations and their phase delays from the mean of the pulse distribution were dependent on membrane potential oscillation amplitude. We applied four pairs of cyclic Gaussian stimulations and somatic sinusoidal current stimulations at the same frequency (5 Hz) with varying phase differences (-pi/2, 0, pi/2, pi rad). The paired stimulations induced phase distributions of the oscillation in the membrane potential, which showed a dependency on an increasing membrane potential oscillation amplitude response to cyclic Gaussian stimulation. This membrane potential dynamic was exhibited by the mixture of the membrane potential oscillation-amplitude-dependent phase delay and the linear summation of the two sinusoidal waves. These suggest that phases of the membrane potential oscillation are modulated by excitatory synaptic inputs. This phase-modulation by excitatory synaptic inputs may play a crucial role for memory operation in the hippocampus.
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Affiliation(s)
- H Watanabe
- Research Institute, Tamagawa University, 6-1-1 Tamagawa-gakuen, Machida, Tokyo 194-8610, Japan.
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50
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Kaneda K, Fujiwara-Tsukamoto Y, Isomura Y, Takada M. Region-specific modulation of electrically induced synchronous oscillations in the rat hippocampus and cerebral cortex. Neurosci Res 2005; 52:83-94. [PMID: 15811556 DOI: 10.1016/j.neures.2005.01.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2004] [Revised: 01/25/2005] [Accepted: 01/31/2005] [Indexed: 10/25/2022]
Abstract
Strong tetanization induces synchronous membrane potential oscillations (seizure-like afterdischarge) in mature pyramidal cells of the hippocampal CA1 region. To investigate whether local networks in other brain regions can generate such an afterdischarge independently, we studied the inducibility of afterdischarge in individual 'isolated slices' of the rat hippocampal CA1 and CA3 regions, dentate gyrus (DG), entorhinal cortex (EC), and temporal cortex (TC) using intracellular and extracellular recordings. The strong tetanization constantly induced afterdischarges in the CA1 and CA3 pyramidal cells as well as in the EC and TC superficial principal cells. However, parameters of the afterdischarges, such as the frequency and duration of afterdischarges, varied among the regions. A mixture of N-methyl-D-aspartate (NMDA) and non-NMDA receptor antagonists or a GABA(A) receptor antagonist completely blocked the afterdischarges. Local GABA application during the afterdischarge elicited depolarization, rather than hyperpolarization. Moreover, reversal potentials of the afterdischarge were around -40 mV. In contrast, the tetanization resulted in occasional afterdischarge-like activities in DG slices, which were blocked by the non-NMDA or GABA(A) receptor antagonist. These findings suggest that the afterdischarges mediated through the excitatory GABAergic and glutamatergic transmissions might be common to, but be modulated differently by individual local networks in the hippocampus and cortex.
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Affiliation(s)
- Katsuyuki Kaneda
- Department of System Neuroscience, Tokyo Metropolitan Institute for Neuroscience, Fuchu, Tokyo 183-8526, Japan.
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