1
|
Ma Z, Xu Y, Baier G, Liu Y, Li B, Zhang L. Dynamical modulation of hypersynchronous seizure onset with transcranial magneto-acoustic stimulation in a hippocampal computational model. CHAOS (WOODBURY, N.Y.) 2024; 34:043107. [PMID: 38558041 DOI: 10.1063/5.0181510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Accepted: 03/09/2024] [Indexed: 04/04/2024]
Abstract
Hypersynchronous (HYP) seizure onset is one of the frequently observed seizure-onset patterns in temporal lobe epileptic animals and patients, often accompanied by hippocampal sclerosis. However, the exact mechanisms and ion dynamics of the transition to HYP seizures remain unclear. Transcranial magneto-acoustic stimulation (TMAS) has recently been proposed as a novel non-invasive brain therapy method to modulate neurological disorders. Therefore, we propose a biophysical computational hippocampal network model to explore the evolution of HYP seizure caused by changes in crucial physiological parameters and design an effective TMAS strategy to modulate HYP seizure onset. We find that the cooperative effects of abnormal glial uptake strength of potassium and excessive bath potassium concentration could produce multiple discharge patterns and result in transitions from the normal state to the HYP seizure state and ultimately to the depolarization block state. Moreover, we find that the pyramidal neuron and the PV+ interneuron in HYP seizure-onset state exhibit saddle-node-on-invariant-circle/saddle homoclinic (SH) and saddle-node/SH at onset/offset bifurcation pairs, respectively. Furthermore, the response of neuronal activities to TMAS of different ultrasonic waveforms revealed that lower sine wave stimulation can increase the latency of HYP seizures and even completely suppress seizures. More importantly, we propose an ultrasonic parameter area that not only effectively regulates epileptic rhythms but also is within the safety limits of ultrasound neuromodulation therapy. Our results may offer a more comprehensive understanding of the mechanisms of HYP seizure and provide a theoretical basis for the application of TMAS in treating specific types of seizures.
Collapse
Affiliation(s)
- Zhiyuan Ma
- Department of Biomedical Engineering, College of Chemistry and Life Science, Beijing University of Technology, Beijing 100124, China
| | - Yuejuan Xu
- Department of Biomedical Engineering, College of Chemistry and Life Science, Beijing University of Technology, Beijing 100124, China
| | - Gerold Baier
- Cell and Developmental Biology, Faculty of Life Sciences, University College London, London WC1E 6BT, United Kingdom
| | - Youjun Liu
- Department of Biomedical Engineering, College of Chemistry and Life Science, Beijing University of Technology, Beijing 100124, China
| | - Bao Li
- Department of Biomedical Engineering, College of Chemistry and Life Science, Beijing University of Technology, Beijing 100124, China
| | - Liyuan Zhang
- Department of Biomedical Engineering, College of Chemistry and Life Science, Beijing University of Technology, Beijing 100124, China
| |
Collapse
|
2
|
Wenzel M, Huberfeld G, Grayden DB, de Curtis M, Trevelyan AJ. A debate on the neuronal origin of focal seizures. Epilepsia 2023; 64 Suppl 3:S37-S48. [PMID: 37183507 DOI: 10.1111/epi.17650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 04/26/2023] [Accepted: 05/12/2023] [Indexed: 05/16/2023]
Abstract
A critical question regarding how focal seizures start is whether we can identify particular cell classes that drive the pathological process. This was the topic for debate at the recent International Conference for Technology and Analysis of Seizures (ICTALS) meeting (July 2022, Bern, CH) that we summarize here. The debate has been fueled in recent times by the introduction of powerful new ways to manipulate subpopulations of cells in relative isolation, mostly using optogenetics. The motivation for resolving the debate is to identify novel targets for therapeutic interventions through a deeper understanding of the etiology of seizures.
Collapse
Affiliation(s)
- Michael Wenzel
- Department of Epileptology, University Hospital Bonn, University of Bonn, Bonn, Germany
| | - Gilles Huberfeld
- Neurology Department, Hopital Fondation Adolphe de Rothschild, Paris, France
- Center for Interdisciplinary Research in Biology (CIRB), College de France, CNRS, INSERM, Université PSL, Paris, France
| | - David B Grayden
- Department of Biomedical Engineering, The University of Melbourne, Melbourne, Victoria, Australia
- Department of Medicine, St Vincent's Hospital, The University of Melbourne, Melbourne, Victoria, Australia
- Graeme Clark Institute, The University of Melbourne, Melbourne, Victoria, Australia
| | - Marco de Curtis
- Epilepsy Unit, Fondazione I.R.C.C.S., Istituto Neurologico Carlo Besta, Milan, Italy
| | - Andrew J Trevelyan
- Newcastle University Biosciences Institute, Medical School, Framlington Place, Newcastle upon Tyne, UK
| |
Collapse
|
3
|
Dong L, Song LL, Zhao WJ, Zhao L, Tian L, Zheng Y. Modulatory effects of real-time electromagnetic stimulation on epileptiform activity in juvenile rat hippocampus based on multi-electrode array recordings. Brain Res Bull 2023; 198:27-35. [PMID: 37084982 DOI: 10.1016/j.brainresbull.2023.04.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2023] [Revised: 04/10/2023] [Accepted: 04/18/2023] [Indexed: 04/23/2023]
Abstract
Electromagnetic stimulation (EMS) has proven to be useful for the focal suppression of epileptiform activity (EFA) in the hippocampus. There is a critical period during EFA for achieving the transition from brief interictal discharges (IIDs) to prolonged ictal discharges (IDs), and it is unknown whether EMS can modulate this transition. Therefore, this study aimed to evaluate the intensity- and time-dependent effect of EMS on the transition of EFA. A juvenile rat EFA model was constructed by perfusing magnesium-free artificial cerebrospinal fluid (aCSF) on brain slices, and the induced EFA was recorded using a micro-electrode array (MEA) platform. After a stable EFA event was recorded for some time, real-time pulsed magnetic stimulation with low and high peak-to-peak input magnetic field intensities was carried out. A 5-min intervention with real-time magnetic fields with low intensity was found to reduce the amplitude of IDs (ID events still existed), whereas a 5-min intervention with real-time magnetic fields with high input voltages completely suppressed IDs. Short-time magnetic fields (9s and 1min) with high or low input intensity had no effect on EFA. Real-time magnetic fields can block the normal EFA process from IIDs to IDs (i.e., a complete EFA cycle) and this suppression effect is dependent on input intensities and intervention duration. The experimental findings further indicate that magnetic stimulation may be chosen as an alternative antiepileptic therapy.
Collapse
Affiliation(s)
- Lei Dong
- School of Life Sciences, Tiangong University, Tianjin 300387, China; State Key Laboratory of Precision Measurement Technology and Instruments, Tianjin University, Tianjin 300072, China
| | - Lin-Lin Song
- School of Life Sciences, Tiangong University, Tianjin 300387, China; School of Electronic and Information Engineering, Tiangong University, Tianjin 300387, China
| | - Wen-Jun Zhao
- School of Life Sciences, Tiangong University, Tianjin 300387, China
| | - Ling Zhao
- School of Life Sciences, Tiangong University, Tianjin 300387, China
| | - Lei Tian
- School of Life Sciences, Tiangong University, Tianjin 300387, China
| | - Yu Zheng
- School of Life Sciences, Tiangong University, Tianjin 300387, China.
| |
Collapse
|
4
|
Avoli M, Chen LY, Di Cristo G, Librizzi L, Scalmani P, Shiri Z, Uva L, de Curtis M, Lévesque M. Ligand-gated mechanisms leading to ictogenesis in focal epileptic disorders. Neurobiol Dis 2023; 180:106097. [PMID: 36967064 DOI: 10.1016/j.nbd.2023.106097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 03/14/2023] [Accepted: 03/22/2023] [Indexed: 04/03/2023] Open
Abstract
We review here the neuronal mechanisms that cause seizures in focal epileptic disorders and, specifically, those involving limbic structures that are known to be implicated in human mesial temporal lobe epilepsy. In both epileptic patients and animal models, the initiation of focal seizures - which are most often characterized by a low-voltage fast onset EEG pattern - is presumably dependent on the synchronous firing of GABA-releasing interneurons that, by activating post-synaptic GABAA receptors, cause large increases in extracellular [K+] through the activation of the co-transporter KCC2. A similar mechanism may contribute to seizure maintenance; accordingly, inhibiting KCC2 activity transforms seizure activity into a continuous pattern of short-lasting epileptiform discharges. It has also been found that interactions between different areas of the limbic system modulate seizure occurrence by controlling extracellular [K+] homeostasis. In line with this view, low-frequency electrical or optogenetic activation of limbic networks restrain seizure generation, an effect that may also involve the activation of GABAB receptors and activity-dependent changes in epileptiform synchronization. Overall, these findings highlight the paradoxical role of GABAA signaling in both focal seizure generation and maintenance, emphasize the efficacy of low-frequency activation in abating seizures, and provide experimental evidence explaining the poor efficacy of antiepileptic drugs designed to augment GABAergic function in controlling seizures in focal epileptic disorders.
Collapse
Affiliation(s)
- Massimo Avoli
- Montreal Neurological Institute-Hospital, Departments of Neurology, Canada; Neurology & Neurosurgery and of Physiology, McGill University, Montreal H3A 2B4, Que, Canada.
| | - Li-Yuan Chen
- Montreal Neurological Institute-Hospital, Departments of Neurology, Canada
| | - Graziella Di Cristo
- Neurosciences Department, Université de Montréal, Montréal, Québec H3T 1N8, Canada; CHU Sainte-Justine Research Center, Montréal, Québec H3T 1C5, Canada
| | - Laura Librizzi
- Epilepsy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Paolo Scalmani
- Epilepsy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Zahra Shiri
- Montreal Neurological Institute-Hospital, Departments of Neurology, Canada
| | - Laura Uva
- Epilepsy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Marco de Curtis
- Epilepsy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Maxime Lévesque
- Montreal Neurological Institute-Hospital, Departments of Neurology, Canada
| |
Collapse
|
5
|
Scalmani P, Paterra R, Mantegazza M, Avoli M, de Curtis M. Involvement of GABAergic Interneuron Subtypes in 4-Aminopyridine-Induced Seizure-Like Events in Mouse Entorhinal Cortex in Vitro. J Neurosci 2023; 43:1987-2001. [PMID: 36810229 PMCID: PMC10027059 DOI: 10.1523/jneurosci.1190-22.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 12/30/2022] [Accepted: 01/05/2023] [Indexed: 02/23/2023] Open
Abstract
Single-unit recordings performed in temporal lobe epilepsy patients and in models of temporal lobe seizures have shown that interneurons are active at focal seizure onset. We performed simultaneous patch-clamp and field potential recordings in entorhinal cortex slices of GAD65 and GAD67 C57BL/6J male mice that express green fluorescent protein in GABAergic neurons to analyze the activity of specific interneuron (IN) subpopulations during acute seizure-like events (SLEs) induced by 4-aminopyridine (4-AP; 100 μm). IN subtypes were identified as parvalbuminergic (INPV, n = 17), cholecystokinergic (INCCK), n = 13], and somatostatinergic (INSOM, n = 15), according to neurophysiological features and single-cell digital PCR. INPV and INCCK discharged at the start of 4-AP-induced SLEs characterized by either low-voltage fast or hyper-synchronous onset pattern. In both SLE onset types, INSOM fired earliest before SLEs, followed by INPV and INCCK discharges. Pyramidal neurons became active with variable delays after SLE onset. Depolarizing block was observed in ∼50% of cells in each INs subgroup, and it was longer in IN (∼4 s) than in pyramidal neurons (<1 s). As SLE evolved, all IN subtypes generated action potential bursts synchronous with the field potential events leading to SLE termination. High-frequency firing throughout the SLE occurred in one-third of INPV and INSOM We conclude that entorhinal cortex INs are very active at the onset and during the progression of SLEs induced by 4-AP. These results support earlier in vivo and in vivo evidence and suggest that INs have a preferential role in focal seizure initiation and development.SIGNIFICANCE STATEMENT Focal seizures are believed to result from enhanced excitation. Nevertheless, we and others demonstrated that cortical GABAergic networks may initiate focal seizures. Here, we analyzed for the first time the role of different IN subtypes in seizures generated by 4-aminopyridine in the mouse entorhinal cortex slices. We found that in this in vitro focal seizure model, all IN types contribute to seizure initiation and that INs precede firing of principal cells. This evidence is in agreement with the active role of GABAergic networks in seizure generation.
Collapse
Affiliation(s)
| | - Rosina Paterra
- Neuro-Oncology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano 20133, Italy
| | - Massimo Mantegazza
- Université Côte d'Azur, 06560 Valbonne-Sophia Antipolis, France
- Institute of Molecular and Cellular Pharmacology, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7275, Laboratoire d'Excellence/Canaux Ioniques d'Intérêt Thérapeutique, 06650 Valbonne-Sophia Antipolis, France
- Institut National de la Santé et de la Recherche Médicale, 06650 Valbonne-Sophia Antipolis, France
| | - Massimo Avoli
- Montreal Neurological Institute-Hospital, McGill University, Montreal, Quebec H3A 2B4, Canada
- Departments of Neurology and Neurosurgery and Physiology, McGill University, Montreal, Quebec H3A 2B4, Canada
| | | |
Collapse
|
6
|
Gentiletti D, de Curtis M, Gnatkovsky V, Suffczynski P. Focal seizures are organized by feedback between neural activity and ion concentration changes. eLife 2022; 11:68541. [PMID: 35916367 PMCID: PMC9377802 DOI: 10.7554/elife.68541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Accepted: 07/12/2022] [Indexed: 11/13/2022] Open
Abstract
Human and animal EEG data demonstrate that focal seizures start with low-voltage fast activity, evolve into rhythmic burst discharges and are followed by a period of suppressed background activity. This suggests that processes with dynamics in the range of tens of seconds govern focal seizure evolution. We investigate the processes associated with seizure dynamics by complementing the Hodgkin-Huxley mathematical model with the physical laws that dictate ion movement and maintain ionic gradients. Our biophysically realistic computational model closely replicates the electrographic pattern of a typical human focal seizure characterized by low voltage fast activity onset, tonic phase, clonic phase and postictal suppression. Our study demonstrates, for the first time in silico, the potential mechanism of seizure initiation by inhibitory interneurons via the initial build-up of extracellular K+ due to intense interneuronal spiking. The model also identifies ionic mechanisms that may underlie a key feature in seizure dynamics, i.e., progressive slowing down of ictal discharges towards the end of seizure. Our model prediction of specific scaling of inter-burst intervals is confirmed by seizure data recorded in the whole guinea pig brain in vitro and in humans, suggesting that the observed termination pattern may hold across different species. Our results emphasize ionic dynamics as elementary processes behind seizure generation and indicate targets for new therapeutic strategies.
Collapse
|
7
|
Cherubini E, Di Cristo G, Avoli M. Dysregulation of GABAergic Signaling in Neurodevelomental Disorders: Targeting Cation-Chloride Co-transporters to Re-establish a Proper E/I Balance. Front Cell Neurosci 2022; 15:813441. [PMID: 35069119 PMCID: PMC8766311 DOI: 10.3389/fncel.2021.813441] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Accepted: 11/30/2021] [Indexed: 01/01/2023] Open
Abstract
The construction of the brain relies on a series of well-defined genetically and experience- or activity -dependent mechanisms which allow to adapt to the external environment. Disruption of these processes leads to neurological and psychiatric disorders, which in many cases are manifest already early in postnatal life. GABA, the main inhibitory neurotransmitter in the adult brain is one of the major players in the early assembly and formation of neuronal circuits. In the prenatal and immediate postnatal period GABA, acting on GABAA receptors, depolarizes and excites targeted cells via an outwardly directed flux of chloride. In this way it activates NMDA receptors and voltage-dependent calcium channels contributing, through intracellular calcium rise, to shape neuronal activity and to establish, through the formation of new synapses and elimination of others, adult neuronal circuits. The direction of GABAA-mediated neurotransmission (depolarizing or hyperpolarizing) depends on the intracellular levels of chloride [Cl−]i, which in turn are maintained by the activity of the cation-chloride importer and exporter KCC2 and NKCC1, respectively. Thus, the premature hyperpolarizing action of GABA or its persistent depolarizing effect beyond the postnatal period, leads to behavioral deficits associated with morphological alterations and an excitatory (E)/inhibitory (I) imbalance in selective brain areas. The aim of this review is to summarize recent data concerning the functional role of GABAergic transmission in building up and refining neuronal circuits early in development and its dysfunction in neurodevelopmental disorders such as Autism Spectrum Disorders (ASDs), schizophrenia and epilepsy. In particular, we focus on novel information concerning the mechanisms by which alterations in cation-chloride co-transporters (CCC) generate behavioral and cognitive impairment in these diseases. We discuss also the possibility to re-establish a proper GABAA-mediated neurotransmission and excitatory (E)/inhibitory (I) balance within selective brain areas acting on CCC.
Collapse
Affiliation(s)
- Enrico Cherubini
- European Brain Research Institute (EBRI)-Rita Levi-Montalcini, Roma, Italy
- *Correspondence: Enrico Cherubini
| | - Graziella Di Cristo
- Neurosciences Department, Université de Montréal and CHU Sainte-Justine Research Center, Montreal, QC, Canada
| | - Massimo Avoli
- Montreal Neurological Institute-Hospital and Departments of Neurology and Neurosurgery and of Physiology, McGill University, Montreal, QC, Canada
| |
Collapse
|
8
|
Liu H, Zhang S, Zhang L. Epileptiform activity in mouse hippocampal slices induced by moderate changes in extracellular Mg 2+, Ca 2+, and K . BMC Neurosci 2021; 22:46. [PMID: 34301200 PMCID: PMC8305515 DOI: 10.1186/s12868-021-00650-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Accepted: 07/16/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Rodent brain slices-particularly hippocampal slices-are widely used in experimental investigations of epileptiform activity. Oxygenated artificial cerebrospinal fluid (ACSF) is used to maintain slices in vitro. Physiological or standard ACSF containing 3-3.5 mM K+, 1-2 mM Mg2+, and 1-3 mM Ca2+ generally does not induce population epileptiform activity, which can be induced by ACSF with high K+ (8-10 mM), low Mg2+, or low Ca2+ alone or in combination. While low-Mg2+ ACSF without intentionally added Mg salt but with contaminating Mg2+ (≤ 50-80 µM) from other salts can induce robust epileptiform activity in slices, it is unclear whether such epileptiform activity can be achieved using ACSF with moderately decreased Mg2+. To explore this issue, we examined the effects of moderately modified (m)ACSF with 0.8 mM Mg2+, 1.3 mM Ca2+, and 5.7 mM K+ on induction of epileptiform discharges in mouse hippocampal slices. RESULTS Hippocampal slices were prepared from young (21-28 days old), middle-aged (13-14 months old), and aged (24-26 months old) C57/BL6 mice. Conventional thin (0.4 mm) and thick (0.6 mm) slices were obtained using a vibratome and pretreated with mACSF at 35-36 °C for 1 h prior to recordings. During perfusion with mACSF at 35-36 °C, spontaneous or self-sustained epileptiform field potentials following high-frequency stimulation were frequently recorded in slices pretreated with mACSF but not in those without the pretreatment. Seizure-like ictal discharges were more common in thick slices than in thin slices. CONCLUSIONS Prolonged exposure to mACSF by pretreatment and subsequent perfusion can induce epileptiform field potentials in mouse hippocampal slices.
Collapse
Affiliation(s)
- Haiyu Liu
- Department of Neurosurgery, The First Hospital of Jilin University, Jilin, China.,Graduate School of Tianjin Medical University, Tianjin, China.,Krembil Research Institute, University Health Network, Toronto, ON, Canada
| | - Sai Zhang
- Graduate School of Tianjin Medical University, Tianjin, China.
| | - Liang Zhang
- Krembil Research Institute, University Health Network, Toronto, ON, Canada. .,Department of Medicine (Neurology), University of Toronto, Toronto, ON, Canada.
| |
Collapse
|
9
|
Dong L, Li G, Gao Y, Lin L, Cao XB, Zheng Y. Exploring the Inhibitory Effect of Low-frequency Magnetic Fields on Epileptiform Discharges in Juvenile Rat Hippocampus. Neuroscience 2021; 467:1-15. [PMID: 34033871 DOI: 10.1016/j.neuroscience.2021.05.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 05/12/2021] [Accepted: 05/13/2021] [Indexed: 10/01/2022]
Abstract
Stimulation with a low frequency electromagnetic field (LF-EMF) has proven to represent a powerful method for the suppression of seizures, as demonstrated in select clinical and laboratory studies. However, the mechanism by which LF-EMF suppresses seizures remains unclear. The purpose of the present study was to explore the modulatory effect of LF-EMF on epileptiform discharges (EDs) using rat hippocampal slices and investigate the underlying mechanisms that mediate these effects. EDs in hippocampal slices was induced by magnesium-free (zero-Mg2+) artificial cerebrospinal fluid (ACSF) and recorded using an in vitro micro-electrode array (MEA). A small sub-decimeter coil was designed and incorporated in a flexible magnetic stimulation device that allowed electromagnetic fields with different parameters to be delivered to slices. After a stable ED event was recorded, magnetic fields of 0.5 Hz (30 min) with a magnetic intensity of 0.13 mT (5 Vpp voltage input) and 0.25 mT (20 Vpp voltage input) were applied. The results indicated that a high-amplitude 0.5 Hz magnetic field could lead to persistent suppression of ictal discharges (IDs), while low-amplitude magnetic fields did not influence IDs. The persistent suppression of complex ED was prevented if the magnetic fields were applied in the presence of 10 μmol/L bicuculline (BIC), a γ-aminobutyric acid type A (GABAA) receptor antagonist, while the application of BIC subsequent to a magnetic field application led to the reappearance of ID. The addition of BIC resulted in EDs that had previously been inhibited by magnetic fields, reappearing. Low-frequency magnetic stimulation was able to inhibit the conversion from interictal discharges (IIDs) or preictal discharges (PIDs) to IDs. This suppression was attributed to the modulation of GABAA receptor activity.
Collapse
Affiliation(s)
- Lei Dong
- State Key Laboratory of Precision Measurement Technology and Instruments, Tianjin University, Tianjin 300072, China; Tianjin Key Laboratory of Biomedical Detecting Techniques & Instruments, Tianjin University, Tianjin 300072, China
| | - Gang Li
- State Key Laboratory of Precision Measurement Technology and Instruments, Tianjin University, Tianjin 300072, China; Tianjin Key Laboratory of Biomedical Detecting Techniques & Instruments, Tianjin University, Tianjin 300072, China
| | - Yang Gao
- School of Information Technology and Electrical Engineering, The University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia
| | - Ling Lin
- State Key Laboratory of Precision Measurement Technology and Instruments, Tianjin University, Tianjin 300072, China; Tianjin Key Laboratory of Biomedical Detecting Techniques & Instruments, Tianjin University, Tianjin 300072, China
| | - Xue-Bin Cao
- Department of Cardiology, 252 Hospital of PLA, Baoding, Hebei 071000, China.
| | - Yu Zheng
- School of Life Sciences, Tiangong University, Tianjin 300387, China.
| |
Collapse
|
10
|
Uva L, Aracri P, Forcaia G, de Curtis M. Mapping region-specific seizure-like patterns in the in vitro isolated guinea pig brain. Exp Neurol 2021; 342:113727. [PMID: 33930392 DOI: 10.1016/j.expneurol.2021.113727] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 04/09/2021] [Accepted: 04/22/2021] [Indexed: 10/21/2022]
Abstract
Specific neurophysiological seizure patterns in patients with focal epilepsy depend on cerebral location and the underlying neuropathology. Location-specific patterns have been also reported in experimental models. Two focal seizure patterns, named p-type and l-type, typical of neocortical and mesial temporal regions were identified in both patients explored with intracerebral EEG and in animal models. These two patterns were recorded in the olfactory regions and in the entorhinal cortex after either 4AP or BMI administration. Here we mapped epileptiform activities in other cortices to verify the existence of specific epileptiform patterns. Field potentials were simultaneously recorded at multiple locations in olfactory, limbic and neocortical regions of the isolated guinea pig brain after arterial administration of either 4AP or BMI. Most neocortical areas did not generate new distinctive focal seizure-like event (SLE), beside the p-type and l-type patterns. Spiking activity was typically recorded after BMI in all new analyzed regions, whereas SLEs were commonly observed during 4AP perfusion. We confirmed the presence of reproducible region-specific epileptiform patterns in all explored cortical areas and demonstrated that strongly inter-connected areas generate similar SLEs. Our study suggests that p- and l-type SLE represent the most common focal seizure patterns during acute manipulations with pro-epileptic compounds.
Collapse
Affiliation(s)
- Laura Uva
- Epilepsy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, via Amadeo 42, 20133 Milano, Italy.
| | - Patrizia Aracri
- Epilepsy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, via Amadeo 42, 20133 Milano, Italy
| | - Greta Forcaia
- School of Medicine and Surgery, University of Milano-Bicocca, via Cadore 48, 20900 Monza, MB, Italy.
| | - Marco de Curtis
- Epilepsy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, via Amadeo 42, 20133 Milano, Italy.
| |
Collapse
|
11
|
A novel methodology to describe neuronal networks activity reveals spatiotemporal recruitment dynamics of synchronous bursting states. J Comput Neurosci 2021; 49:375-394. [PMID: 33904004 DOI: 10.1007/s10827-021-00786-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 04/08/2021] [Accepted: 04/12/2021] [Indexed: 09/29/2022]
Abstract
We propose a novel phase based analysis with the purpose of quantifying the periodic bursts of activity observed in various neuronal systems. The way bursts are intiated and propagate in a spatial network is still insufficiently characterized. In particular, we investigate here how these spatiotemporal dynamics depend on the mean connection length. We use a simplified description of a neuron's state as a time varying phase between firings. This leads to a definition of network bursts, that does not depend on the practitioner's individual judgment as the usage of subjective thresholds and time scales. This allows both an easy and objective characterization of the bursting dynamics, only depending on system's proper scales. Our approach thus ensures more reliable and reproducible measurements. We here use it to describe the spatiotemporal processes in networks of intrinsically oscillating neurons. The analysis rigorously reveals the role of the mean connectivity length in spatially embedded networks in determining the existence of "leader" neurons during burst initiation, a feature incompletely understood observed in several neuronal cultures experiments. The precise definition of a burst with our method allowed us to rigorously characterize the initiation dynamics of bursts and show how it depends on the mean connectivity length. Although presented with simulations, the methodology can be applied to other forms of neuronal spatiotemporal data. As shown in a preliminary study with MEA recordings, it is not limited to in silico modeling.
Collapse
|
12
|
Dong L, Li G, Gao Y, Lin L, Zhang KH, Tian CX, Cao XB, Zheng Y. Effect of priming low-frequency magnetic fields on zero-Mg2+ -induced epileptiform discharges in rat hippocampal slices. Epilepsy Res 2020; 167:106464. [DOI: 10.1016/j.eplepsyres.2020.106464] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 09/02/2020] [Accepted: 09/05/2020] [Indexed: 12/16/2022]
|
13
|
Serrano-Reyes M, García-Vilchis B, Reyes-Chapero R, Cáceres-Chávez VA, Tapia D, Galarraga E, Bargas J. Spontaneous Activity of Neuronal Ensembles in Mouse Motor Cortex: Changes after GABAergic Blockade. Neuroscience 2020; 446:304-322. [PMID: 32860933 DOI: 10.1016/j.neuroscience.2020.08.025] [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: 06/09/2020] [Revised: 08/02/2020] [Accepted: 08/18/2020] [Indexed: 01/12/2023]
Abstract
The mouse motor cortex exhibits spontaneous activity in the form of temporal sequences of neuronal ensembles in vitro without the need of tissue stimulation. These neuronal ensembles are defined as groups of neurons with a strong correlation between its firing patterns, generating what appears to be a predetermined neural conduction mode that needs study. Each ensemble is commonly accompanied by one or more parvalbumin expressing neurons (PV+) or fast spiking interneurons. Many of these interneurons have functional connections between them, helping to form a circuit configuration similar to a small-world network. However, rich club metrics show that most connected neurons are neurons not expressing parvalbumin, mainly pyramidal neurons (PV-) suggesting feed-forward propagation through pyramidal cells. Ensembles with PV+ neurons are connected to these hubs. When ligand-gated fast GABAergic transmission is blocked, temporal sequences of ensembles collapse into a unique synchronous and recurrent ensemble, showing the need of inhibition for coding cortical spontaneous activity. This new ensemble has a duration and electrophysiological characteristics of brief recurrent interictal epileptiform discharges (IEDs) composed by the coactivity of both PV- and PV+ neurons, demonstrating that GABA transmission impedes its occurrence. Synchronous ensembles are clearly divided into two clusters one of them lasting longer and mainly composed by PV+ neurons. Because an ictal-like event was not recorded after several minutes of IEDs recording, it is inferred that an external stimulus and/or fast GABA transmission are necessary for its appearance, making this preparation ideal to study both the neuronal machinery to encode cortical spontaneous activity and its transformation into brief non-ictal epileptiform discharges.
Collapse
Affiliation(s)
- Miguel Serrano-Reyes
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México City 04510, Mexico
| | - Brisa García-Vilchis
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México City 04510, Mexico
| | - Rosa Reyes-Chapero
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México City 04510, Mexico
| | | | - Dagoberto Tapia
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México City 04510, Mexico
| | - Elvira Galarraga
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México City 04510, Mexico
| | - José Bargas
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México City 04510, Mexico.
| |
Collapse
|
14
|
Zheng Y, Zhang K, Dong L, Tian C. Study on the mechanism of high-frequency stimulation inhibiting low-Mg 2+-induced epileptiform discharges in juvenile rat hippocampal slices. Brain Res Bull 2020; 165:1-13. [PMID: 32961285 DOI: 10.1016/j.brainresbull.2020.09.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Revised: 09/02/2020] [Accepted: 09/09/2020] [Indexed: 11/29/2022]
Abstract
Study on the mechanism of high-frequency stimulation inhibiting low-Mg2+-induced epileptiform discharges in juvenile rat hippocampal slices High-frequency stimulation (HFS) has been demonstrated to be an effective treatment for inhibiting epilepsy in some clinical and laboratory studies. However, the mechanisms underlying the therapeutic effects of HFS are not yet fully understood. In our present study, epileptiform discharges (EDs) in acutely isolated hippocampal slices of male Sprague-Dawley (SD) juvenile rats induced by low-Mg2+ artificial cerebrospinal fluid (ACSF), and electrical stimulation (square wave, 900 pulses, 50 % duty-cycle, 130 Hz) was performed on the CA3 using concentric bipolar electrodes. EDs of neurons in hippocampal were recorded by multi-electrode arrays (MEA). After stable EDs events had been recorded for at least 20 min, HFS was added, followed by 10 μmol/L gamma-aminobutyric acid type A (GABAA) receptors blocker bicuculline (BIC). The results show that the HFS can increase the discharges frequency of inter-ictal discharges (IIDs) and decrease the duration of ictal discharges (IDs). However, the HFS had no effect on the slices with 10 μmol/L BIC. These results indicated that the GABAA receptors are activated when HFS inhibited EDs, thereby achieving the inhibition of low-Mg2+-induced EDs in slices.
Collapse
Affiliation(s)
- Yu Zheng
- School of Life Sciences, Tiangong University, Tianjin, 300387, China.
| | - Kanghui Zhang
- School of Life Sciences, Tiangong University, Tianjin, 300387, China
| | - Lei Dong
- State Key Laboratory of Precision Measurement Technology and Instruments, Tianjin University, Tianjin, 300072, China
| | - Chunxiao Tian
- School of Life Sciences, Tiangong University, Tianjin, 300387, China
| |
Collapse
|
15
|
Victor TR, Tsirka SE. Microglial contributions to aberrant neurogenesis and pathophysiology of epilepsy. NEUROIMMUNOLOGY AND NEUROINFLAMMATION 2020; 7:234-247. [PMID: 33154976 PMCID: PMC7641338 DOI: 10.20517/2347-8659.2020.02] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Microglia are dynamic cells that constitute the brain's innate immune system. Recently, research has demonstrated microglial roles beyond immunity, which include homeostatic roles in the central nervous system. The function of microglia is an active area of study, with insights into changes in neurogenesis and synaptic pruning being discovered in both health and disease. In epilepsy, activated microglia contribute to several changes that occur during epileptogenesis. In this review, we focus on the effects of microglia on neurogenesis and synaptic pruning, and discuss the current state of anti-seizure drugs and how they affect microglia during these processes. Our understanding of the role of microglia post-seizure is still limited and may be pivotal in recognizing new therapeutic targets for seizure intervention.
Collapse
Affiliation(s)
- Tanya R Victor
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794, USA
| | - Stella E Tsirka
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794, USA
| |
Collapse
|
16
|
Lévesque M, Ragsdale D, Avoli M. Evolving Mechanistic Concepts of Epileptiform Synchronization and their Relevance in Curing Focal Epileptic Disorders. Curr Neuropharmacol 2020; 17:830-842. [PMID: 30479217 PMCID: PMC7052840 DOI: 10.2174/1570159x17666181127124803] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2018] [Revised: 10/26/2018] [Accepted: 11/17/2018] [Indexed: 01/01/2023] Open
Abstract
The synchronized activity of neuronal networks under physiological conditions is mirrored by specific oscillatory patterns of the EEG that are associated with different behavioral states and cognitive functions. Excessive synchronization can, however, lead to focal epileptiform activity characterized by interictal and ictal discharges in epileptic patients and animal models. This review focusses on studies that have addressed epileptiform synchronization in temporal lobe regions by employing in vitro and in vivo recording techniques. First, we consider the role of ionotropic and metabotropic excitatory glutamatergic transmission in seizure generation as well as the paradoxical role of GABAA signaling in initiating and perhaps maintaining focal seizure activity. Second, we address non-synaptic mechanisms (which include voltage-gated ionic currents and gap junctions) in the generation of epileptiform synchronization. For each mechanism, we discuss the actions of antiepileptic drugs that are presumably modulating excitatory or inhibitory signaling and voltage-gated currents to prevent seizures in epileptic patients. These findings provide insights into the mechanisms of seizure initiation and maintenance, thus leading to the development of specific pharmacological treatments for focal epileptic disorders.
Collapse
Affiliation(s)
- Maxime Lévesque
- Montreal Neurological Institute, McGill University, Montreal, H3A 2B4 Quebec, Canada
| | - David Ragsdale
- Montreal Neurological Institute, McGill University, Montreal, H3A 2B4 Quebec, Canada
| | - Massimo Avoli
- Montreal Neurological Institute, McGill University, Montreal, H3A 2B4 Quebec, Canada.,Departments of Neurology & Neurosurgery, and of Physiology, McGill University, Montréal, H3A 2B4 Québec, Canada.,Department of Experimental Medicine, Facoltà di Medicina e Odontoiatria, Sapienza University of Rome, 00185 Roma, Italy
| |
Collapse
|
17
|
Ye H, Kaszuba S. Neuromodulation with electromagnetic stimulation for seizure suppression: From electrode to magnetic coil. IBRO Rep 2019; 7:26-33. [PMID: 31360792 PMCID: PMC6639724 DOI: 10.1016/j.ibror.2019.06.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Accepted: 06/25/2019] [Indexed: 12/31/2022] Open
Abstract
Non-invasive brain tissue stimulation with a magnetic coil provides several irreplaceable advantages over that with an implanted electrode, in altering neural activities under pathological situations. We reviewed clinical cases that utilized time-varying magnetic fields for the treatment of epilepsy, and the safety issues related to this practice. Animal models have been developed to foster understanding of the cellular/molecular mechanisms underlying magnetic control of epileptic activity. These mechanisms include (but are not limited to) (1) direct membrane polarization by the magnetic field, (2) depolarization blockade by the deactivation of ion channels, (3) alteration in synaptic transmission, and (4) interruption of ephaptic interaction and cellular synchronization. Clinical translation of this technology could be improved through the advancement of magnetic design, optimization of stimulation protocols, and evaluation of the long-term safety. Cellular and molecular studies focusing on the mechanisms of magnetic stimulation are of great value in facilitating this translation.
Collapse
Key Words
- 4-AP, 4-aminopyridine
- Animal models
- CD50, convulsant dose
- Cellular mechanisms
- DBS, deep brain stimulation
- EEG, electroencephalography
- ELF-MF, extremely low frequency magnetic fields
- EcoG, electrocorticography
- Epilepsy
- GABA, gamma-aminobutyric acid
- HFS, high frequency stimulation
- KA, kainic acid
- LD50, lethal dose
- LTD, long-term depression
- LTP, long-term potential
- MEG, magnetoencephalography
- MRI, magnetic resonance imaging
- Magnetic stimulation
- NMDAR, N-methyl-d-aspartate receptor
- PTZ, pentylenetetrazol
- REM, rapid eye movement
- SMF, static magnetic field
- TES, transcranial electrical stimulation
- TLE, temporal lobe epilepsy
- TMS, transcranial magnetic stimulation
- rTMS, repetitive transcranial magnetic stimulation
- tDCS, transcranial direct-current stimulation
Collapse
Affiliation(s)
- Hui Ye
- Department of Biology, Loyola University Chicago, Chicago, 1032 W. Sheridan Rd., IL, 60660, United States
| | - Stephanie Kaszuba
- Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Rd., North Chicago, IL, 60064, United States
| |
Collapse
|
18
|
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
|
19
|
Cǎlin A, Stancu M, Zagrean AM, Jefferys JGR, Ilie AS, Akerman CJ. Chemogenetic Recruitment of Specific Interneurons Suppresses Seizure Activity. Front Cell Neurosci 2018; 12:293. [PMID: 30233328 PMCID: PMC6134067 DOI: 10.3389/fncel.2018.00293] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 08/16/2018] [Indexed: 12/22/2022] Open
Abstract
Current anti-epileptic medications that boost synaptic inhibition are effective in reducing several types of epileptic seizure activity. Nevertheless, these drugs can generate significant side-effects and even paradoxical responses due to the broad nature of their action. Recently developed chemogenetic techniques provide the opportunity to pharmacologically recruit endogenous inhibitory mechanisms in a selective and circuit-specific manner. Here, we use chemogenetics to assess the potential of suppressing epileptiform activity by enhancing the synaptic output from three major interneuron populations in the rodent hippocampus: parvalbumin (PV), somatostatin (SST), and vasoactive intestinal peptide (VIP) expressing interneurons. To target different neuronal populations, promoter-specific cre-recombinase mice were combined with viral-mediated delivery of chemogenetic constructs. Targeted electrophysiological recordings were then conducted in an in vitro model of chronic, drug-resistant epilepsy. In addition, behavioral video-scoring was performed in an in vivo model of acutely triggered seizure activity. Pre-synaptic and post-synaptic whole cell recordings in brain slices revealed that each of the three interneuron types increase their firing rate and synaptic output following chemogenetic activation. However, the interneuron populations exhibited different effects on epileptiform discharges. Recruiting VIP interneurons did not change the total duration of epileptiform discharges. In contrast, recruiting SST or PV interneurons produced robust suppression of epileptiform synchronization. PV interneurons exhibited the strongest effect per cell, eliciting at least a fivefold greater reduction in epileptiform activity than the other cell types. Consistent with this, we found that in vivo chemogenetic recruitment of PV interneurons suppressed convulsive behaviors by more than 80%. Our findings support the idea that selective chemogenetic enhancement of inhibitory synaptic pathways offers potential as an anti-seizure strategy.
Collapse
Affiliation(s)
- Alexandru Cǎlin
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Mihai Stancu
- Division of Physiology and Neuroscience, Department of Functional Sciences, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania
| | - Ana-Maria Zagrean
- Division of Physiology and Neuroscience, Department of Functional Sciences, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania
| | | | - Andrei S. Ilie
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Colin J. Akerman
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| |
Collapse
|
20
|
Chang YY, Gong XW, Gong HQ, Liang PJ, Zhang PM, Lu QC. GABA A Receptor Activity Suppresses the Transition from Inter-ictal to Ictal Epileptiform Discharges in Juvenile Mouse Hippocampus. Neurosci Bull 2018; 34:1007-1016. [PMID: 30128691 DOI: 10.1007/s12264-018-0273-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Accepted: 05/31/2018] [Indexed: 12/12/2022] Open
Abstract
Exploring the transition from inter-ictal to ictal epileptiform discharges (IDs) and how GABAA receptor-mediated action affects the onset of IDs will enrich our understanding of epileptogenesis and epilepsy treatment. We used Mg2+-free artificial cerebrospinal fluid (ACSF) to induce epileptiform discharges in juvenile mouse hippocampal slices and used a micro-electrode array to record the discharges. After the slices were exposed to Mg2+-free ACSF for 10 min-20 min, synchronous recurrent seizure-like events were recorded across the slices, and each event evolved from inter-ictal epileptiform discharges (IIDs) to pre-ictal epileptiform discharges (PIDs), and then to IDs. During the transition from IIDs to PIDs, the duration of discharges increased and the inter-discharge interval decreased. After adding 3 μmol/L of the GABAA receptor agonist muscimol, PIDs and IDs disappeared, and IIDs remained. Further, the application of 10 μmol/L muscimol abolished all the epileptiform discharges. When the GABAA receptor antagonist bicuculline was applied at 10 μmol/L, IIDs and PIDs disappeared, and IDs remained at decreased intervals. These results indicated that there are dynamic changes in the hippocampal network preceding the onset of IDs, and GABAA receptor activity suppresses the transition from IIDs to IDs in juvenile mouse hippocampus.
Collapse
Affiliation(s)
- Yan-Yan Chang
- Department of Neurology, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200127, China
| | - Xin-Wei Gong
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Hai-Qing Gong
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Pei-Ji Liang
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Pu-Ming Zhang
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
| | - Qin-Chi Lu
- Department of Neurology, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200127, China.
| |
Collapse
|
21
|
Ferrat LA, Goodfellow M, Terry JR. Classifying dynamic transitions in high dimensional neural mass models: A random forest approach. PLoS Comput Biol 2018; 14:e1006009. [PMID: 29499044 PMCID: PMC5851637 DOI: 10.1371/journal.pcbi.1006009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Revised: 03/14/2018] [Accepted: 01/30/2018] [Indexed: 02/04/2023] Open
Abstract
Neural mass models (NMMs) are increasingly used to uncover the large-scale mechanisms of brain rhythms in health and disease. The dynamics of these models is dependent upon the choice of parameters, and therefore it is crucial to be able to understand how dynamics change when parameters are varied. Despite being considered low dimensional in comparison to micro-scale, neuronal network models, with regards to understanding the relationship between parameters and dynamics, NMMs are still prohibitively high dimensional for classical approaches such as numerical continuation. Therefore, we need alternative methods to characterise dynamics of NMMs in high dimensional parameter spaces. Here, we introduce a statistical framework that enables the efficient exploration of the relationship between model parameters and selected features of the simulated, emergent model dynamics of NMMs. We combine the classical machine learning approaches of trees and random forests to enable studying the effect that varying multiple parameters has on the dynamics of a model. The method proceeds by using simulations to transform the mathematical model into a database. This database is then used to partition parameter space with respect to dynamic features of interest, using random forests. This allows us to rapidly explore dynamics in high dimensional parameter space, capture the approximate location of qualitative transitions in dynamics and assess the relative importance of all parameters in the model in all dimensions simultaneously. We apply this method to a commonly used NMM in the context of transitions to seizure dynamics. We find that the inhibitory sub-system is most crucial for the generation of seizure dynamics, confirm and expand previous findings regarding the ratio of excitation and inhibition, and demonstrate that previously overlooked parameters can have a significant impact on model dynamics. We advocate the use of this method in future to constrain high dimensional parameter spaces enabling more efficient, person-specific, model calibration.
Collapse
Affiliation(s)
- Lauric A. Ferrat
- College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, UK
- Living Systems Institute, University of Exeter, Exeter, UK
- Centre for Biomedical Modelling and Analysis, University of Exeter, Exeter, UK
- EPSRC Centre for Predictive Modelling in Healthcare, University of Exeter, Exeter, UK
| | - Marc Goodfellow
- College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, UK
- Living Systems Institute, University of Exeter, Exeter, UK
- Centre for Biomedical Modelling and Analysis, University of Exeter, Exeter, UK
- EPSRC Centre for Predictive Modelling in Healthcare, University of Exeter, Exeter, UK
| | - John R. Terry
- College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, UK
- Living Systems Institute, University of Exeter, Exeter, UK
- Centre for Biomedical Modelling and Analysis, University of Exeter, Exeter, UK
- EPSRC Centre for Predictive Modelling in Healthcare, University of Exeter, Exeter, UK
| |
Collapse
|
22
|
Fardet T, Ballandras M, Bottani S, Métens S, Monceau P. Understanding the Generation of Network Bursts by Adaptive Oscillatory Neurons. Front Neurosci 2018; 12:41. [PMID: 29467607 PMCID: PMC5808224 DOI: 10.3389/fnins.2018.00041] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 01/17/2018] [Indexed: 12/26/2022] Open
Abstract
Experimental and numerical studies have revealed that isolated populations of oscillatory neurons can spontaneously synchronize and generate periodic bursts involving the whole network. Such a behavior has notably been observed for cultured neurons in rodent's cortex or hippocampus. We show here that a sufficient condition for this network bursting is the presence of an excitatory population of oscillatory neurons which displays spike-driven adaptation. We provide an analytic model to analyze network bursts generated by coupled adaptive exponential integrate-and-fire neurons. We show that, for strong synaptic coupling, intrinsically tonic spiking neurons evolve to reach a synchronized intermittent bursting state. The presence of inhibitory neurons or plastic synapses can then modulate this dynamics in many ways but is not necessary for its appearance. Thanks to a simple self-consistent equation, our model gives an intuitive and semi-quantitative tool to understand the bursting behavior. Furthermore, it suggests that after-hyperpolarization currents are sufficient to explain bursting termination. Through a thorough mapping between the theoretical parameters and ion-channel properties, we discuss the biological mechanisms that could be involved and the relevance of the explored parameter-space. Such an insight enables us to propose experimentally-testable predictions regarding how blocking fast, medium or slow after-hyperpolarization channels would affect the firing rate and burst duration, as well as the interburst interval.
Collapse
Affiliation(s)
- Tanguy Fardet
- Laboratoire Matière et Systèmes Complexes, UMR 7057, Université Paris Diderot, USPC, Paris, France
| | - Mathieu Ballandras
- Laboratoire Matière et Systèmes Complexes, UMR 7057, Université Paris Diderot, USPC, Paris, France
| | - Samuel Bottani
- Laboratoire Matière et Systèmes Complexes, UMR 7057, Université Paris Diderot, USPC, Paris, France
| | - Stéphane Métens
- Laboratoire Matière et Systèmes Complexes, UMR 7057, Université Paris Diderot, USPC, Paris, France
| | - Pascal Monceau
- Laboratoire Matière et Systèmes Complexes, UMR 7057, Université Paris Diderot, USPC, Paris, France.,Department of Physics, Université d'Evry-Val d'Essonne, Évry, France
| |
Collapse
|
23
|
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.
Collapse
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
| |
Collapse
|
24
|
Follwaczny P, Schieweck R, Riedemann T, Demleitner A, Straub T, Klemm AH, Bilban M, Sutor B, Popper B, Kiebler MA. Pumilio2-deficient mice show a predisposition for epilepsy. Dis Model Mech 2017; 10:1333-1342. [PMID: 29046322 PMCID: PMC5719250 DOI: 10.1242/dmm.029678] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 09/06/2017] [Indexed: 01/18/2023] Open
Abstract
Epilepsy is a neurological disease that is caused by abnormal hypersynchronous activities of neuronal ensembles leading to recurrent and spontaneous seizures in human patients. Enhanced neuronal excitability and a high level of synchrony between neurons seem to trigger these spontaneous seizures. The molecular mechanisms, however, regarding the development of neuronal hyperexcitability and maintenance of epilepsy are still poorly understood. Here, we show that pumilio RNA-binding family member 2 (Pumilio2; Pum2) plays a role in the regulation of excitability in hippocampal neurons of weaned and 5-month-old male mice. Almost complete deficiency of Pum2 in adult Pum2 gene-trap mice (Pum2 GT) causes misregulation of genes involved in neuronal excitability control. Interestingly, this finding is accompanied by the development of spontaneous epileptic seizures in Pum2 GT mice. Furthermore, we detect an age-dependent increase in Scn1a (Nav1.1) and Scn8a (Nav1.6) mRNA levels together with a decrease in Scn2a (Nav1.2) transcript levels in weaned Pum2 GT that is absent in older mice. Moreover, field recordings of CA1 pyramidal neurons show a tendency towards a reduced paired-pulse inhibition after stimulation of the Schaffer-collateral-commissural pathway in Pum2 GT mice, indicating a predisposition to the development of spontaneous seizures at later stages. With the onset of spontaneous seizures at the age of 5 months, we detect increased protein levels of Nav1.1 and Nav1.2 as well as decreased protein levels of Nav1.6 in those mice. In addition, GABA receptor subunit alpha-2 (Gabra2) mRNA levels are increased in weaned and adult mice. Furthermore, we observe an enhanced GABRA2 protein level in the dendritic field of the CA1 subregion in the Pum2 GT hippocampus. We conclude that altered expression levels of known epileptic risk factors such as Nav1.1, Nav1.2, Nav1.6 and GABRA2 result in enhanced seizure susceptibility and manifestation of epilepsy in the hippocampus. Thus, our results argue for a role of Pum2 in epileptogenesis and the maintenance of epilepsy. Summary: Epileptogenic risk factors are misregulated in Pumilio2-deficient mice, determining a predisposition to develop seizures. This article has an associated First Person interview with the first author of the paper as part of the supplementary information.
Collapse
Affiliation(s)
- Philipp Follwaczny
- Biomedical Center (BMC), Department for Cell Biology, Faculty of Medicine, LMU, Munich, 82152 Planegg-Martinsried, Germany
| | - Rico Schieweck
- Biomedical Center (BMC), Department for Cell Biology, Faculty of Medicine, LMU, Munich, 82152 Planegg-Martinsried, Germany
| | - Therese Riedemann
- Biomedical Center (BMC), Department of Physiological Genomics, Ludwig-Maximilians-University, Munich, 82152 Planegg-Martinsried, Germany
| | - Antonia Demleitner
- Biomedical Center (BMC), Department for Cell Biology, Faculty of Medicine, LMU, Munich, 82152 Planegg-Martinsried, Germany
| | - Tobias Straub
- Biomedical Center (BMC), Core Facility Bioinformatics, Ludwig-Maximilians-University, Munich, 82152 Planegg-Martinsried, Germany
| | - Anna H Klemm
- Biomedical Center (BMC), Core Facility Bioimaging, Ludwig-Maximilians-University, Munich, 82152 Planegg-Martinsried, Germany.,Walter Brendel Centre of Experimental Medicine, Ludwig-Maximilians-University, 81377 Munich, Germany
| | - Martin Bilban
- Department of Laboratory Medicine and Core Facility Genomics, Medical University of Vienna, 1090 Vienna, Austria
| | - Bernd Sutor
- Biomedical Center (BMC), Department of Physiological Genomics, Ludwig-Maximilians-University, Munich, 82152 Planegg-Martinsried, Germany
| | - Bastian Popper
- Biomedical Center (BMC), Department for Cell Biology, Faculty of Medicine, LMU, Munich, 82152 Planegg-Martinsried, Germany .,Biomedical Center (BMC), Core Facility Animal Models, Ludwig-Maximilians-University, Munich, 82152 Planegg-Martinsried, Germany
| | - Michael A Kiebler
- Biomedical Center (BMC), Department for Cell Biology, Faculty of Medicine, LMU, Munich, 82152 Planegg-Martinsried, Germany
| |
Collapse
|
25
|
Interneuronal Network Activity at the Onset of Seizure-Like Events in Entorhinal Cortex Slices. J Neurosci 2017; 37:10398-10407. [PMID: 28947576 DOI: 10.1523/jneurosci.3906-16.2017] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 07/05/2017] [Accepted: 07/08/2017] [Indexed: 12/19/2022] Open
Abstract
The onset of focal seizures in humans and in different animal models of focal epilepsy correlates with reduction of neuronal firing and enhanced interneuronal network activity. Whether this phenomenon contributes to seizure generation is still unclear. We used the in vitro entorhinal cortex slices bathed in 4-aminopirydine (4-AP) as an experimental paradigm model to evaluate the correlation between interneuronal GABAergic network activity and seizure-like events. Epileptiform discharges were recorded in layer V-VI pyramidal neurons and fast-spiking interneurons in slices from male and female mice and in the isolated female guinea pig brain preparation during perfusion with 4-AP. We observed that 90% of seizure-like events recorded in principal cells were preceded by outward currents coupled with extracellular potassium shifts, abolished by pharmacological blockade of GABAA receptors. Potassium elevations associated to GABAA receptor-mediated population events were confirmed in the entorhinal cortex of the in vitro isolated whole guinea pig brain. Fast-rising and sustained extracellular potassium increases associated to interneuronal network activity consistently preceded the initiation of seizure-like events. We conclude that in the 4-AP seizure model, interneuronal network activity occurs before 4-AP-induced seizures and therefore supports a role of interneuron activity in focal seizure generation.SIGNIFICANCE STATEMENT The paper focuses on the mechanisms of ictogenesis, a topic that requires a step beyond the simplistic view that seizures, and epilepsy, are due to an increase of excitatory network activity. Focal temporal lobe seizures in humans and in several experimental epilepsies likely correlate with a prevalent activation of interneurons. The potassium channel blocker 4-aminopyridine reliably induces seizure-like events in temporal lobe structures. Herein, we show that a majority of seizures in the entorhinal cortex starts with interneuronal network activity accompanied by a fast and sustained increase in extracellular potassium. Our new findings reinforce and add a new piece of evidence to the proposal that limbic seizures can be supported by GABAergic hyperactivity.
Collapse
|
26
|
Sato Y, Wong SM, Iimura Y, Ochi A, Doesburg SM, Otsubo H. Spatiotemporal changes in regularity of gamma oscillations contribute to focal ictogenesis. Sci Rep 2017; 7:9362. [PMID: 28839247 PMCID: PMC5570997 DOI: 10.1038/s41598-017-09931-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 08/02/2017] [Indexed: 01/10/2023] Open
Abstract
In focal ictogenesis, gamma oscillations (30–70 Hz) recorded by electroencephalography (EEG) are related to the epileptiform synchronization of interneurons that links the seizure onset zone (SOZ) to the surrounding epileptogenic zone. We hypothesized that the synchronization of interneurons could be detected as changes in the regularity of gamma oscillation rhythmicity. We used multiscale entropy (MSE) analysis, which can quantify the regularity of EEG rhythmicity, to investigate how the regularity of gamma oscillations changes over the course of a seizure event. We analyzed intracranial EEG data from 13 pediatric patients with focal cortical dysplasia. The MSE analysis revealed the following characteristic changes of MSE score (gamma oscillations): (1) during the interictal periods, the lowest MSE score (the most regular gamma oscillations) was always found in the SOZ; (2) during the preictal periods, the SOZ became more similar to the epileptogenic zone as the MSE score increased in the SOZ (gamma oscillations became less regular in the SOZ); and (3) during the ictal periods, a decreasing MSE score (highly regular gamma oscillations) propagated over the epileptogenic zone. These spatiotemporal changes in regularity of gamma oscillations constitute an important demonstration that focal ictogenesis is caused by dynamic changes in interneuron synchronization.
Collapse
Affiliation(s)
- Yosuke Sato
- Division of Neurology, Hospital for Sick Children, Toronto, Ontario, Canada. .,Department of Neurosurgery, Showa University School of Medicine, Tokyo, Japan.
| | - Simeon M Wong
- Department of Diagnostic Imaging, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Yasushi Iimura
- Division of Neurology, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Ayako Ochi
- Division of Neurology, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Sam M Doesburg
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Hiroshi Otsubo
- Division of Neurology, Hospital for Sick Children, Toronto, Ontario, Canada.
| |
Collapse
|
27
|
Lévesque M, Salami P, Shiri Z, Avoli M. Interictal oscillations and focal epileptic disorders. Eur J Neurosci 2017. [DOI: 10.1111/ejn.13628] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Maxime Lévesque
- Department of Neurology & Neurosurgery; Montreal Neurological Institute; McGill University; 3801 University Street Montréal QC Canada H3A 2B4
| | - Pariya Salami
- Department of Neurology & Neurosurgery; Montreal Neurological Institute; McGill University; 3801 University Street Montréal QC Canada H3A 2B4
| | - Zahra Shiri
- Department of Neurology & Neurosurgery; Montreal Neurological Institute; McGill University; 3801 University Street Montréal QC Canada H3A 2B4
| | - Massimo Avoli
- Department of Neurology & Neurosurgery; Montreal Neurological Institute; McGill University; 3801 University Street Montréal QC Canada H3A 2B4
- Dipartimento di Medicina Sperimentale; Sapienza University of Rome; Roma Italy
| |
Collapse
|
28
|
Avoli M, de Curtis M, Gnatkovsky V, Gotman J, Köhling R, Lévesque M, Manseau F, Shiri Z, Williams S. Specific imbalance of excitatory/inhibitory signaling establishes seizure onset pattern in temporal lobe epilepsy. J Neurophysiol 2016; 115:3229-37. [PMID: 27075542 DOI: 10.1152/jn.01128.2015] [Citation(s) in RCA: 102] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 04/06/2016] [Indexed: 11/22/2022] Open
Abstract
Low-voltage fast (LVF) and hypersynchronous (HYP) patterns are the seizure-onset patterns most frequently observed in intracranial EEG recordings from mesial temporal lobe epilepsy (MTLE) patients. Both patterns also occur in models of MTLE in vivo and in vitro, and these studies have highlighted the predominant involvement of distinct neuronal network/neurotransmitter receptor signaling in each of them. First, LVF-onset seizures in epileptic rodents can originate from several limbic structures, frequently spread, and are associated with high-frequency oscillations in the ripple band (80-200 Hz), whereas HYP onset seizures initiate in the hippocampus and tend to remain focal with predominant fast ripples (250-500 Hz). Second, in vitro intracellular recordings from principal cells in limbic areas indicate that pharmacologically induced seizure-like discharges with LVF onset are initiated by a synchronous inhibitory event or by a hyperpolarizing inhibitory postsynaptic potential barrage; in contrast, HYP onset is associated with a progressive impairment of inhibition and concomitant unrestrained enhancement of excitation. Finally, in vitro optogenetic experiments show that, under comparable experimental conditions (i.e., 4-aminopyridine application), the initiation of LVF- or HYP-onset seizures depends on the preponderant involvement of interneuronal or principal cell networks, respectively. Overall, these data may provide insight to delineate better therapeutic targets in the treatment of patients presenting with MTLE and, perhaps, with other epileptic disorders as well.
Collapse
Affiliation(s)
- Massimo Avoli
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery and of Physiology, McGill University, Montréal, Québec, Canada; Facoltà di Medicina e Odontoiatria, Sapienza Università di Roma, Rome, Italy;
| | - Marco de Curtis
- Epilepsy Unit, Fondazione Istituto Neurologico Carlo Besta, Milan, Italy
| | - Vadym Gnatkovsky
- Epilepsy Unit, Fondazione Istituto Neurologico Carlo Besta, Milan, Italy
| | - Jean Gotman
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery and of Physiology, McGill University, Montréal, Québec, Canada
| | - Rüdiger Köhling
- Oscar-Langendorff-Institute of Physiology, Rostock University Medical Center, Rostock, Germany; and
| | - Maxime Lévesque
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery and of Physiology, McGill University, Montréal, Québec, Canada
| | - Frédéric Manseau
- Douglas Mental Health University Institute, McGill University, Montréal, Québec, Canada
| | - Zahra Shiri
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery and of Physiology, McGill University, Montréal, Québec, Canada
| | - Sylvain Williams
- Douglas Mental Health University Institute, McGill University, Montréal, Québec, Canada
| |
Collapse
|
29
|
de Curtis M, Avoli M. GABAergic networks jump-start focal seizures. Epilepsia 2016; 57:679-87. [PMID: 27061793 DOI: 10.1111/epi.13370] [Citation(s) in RCA: 89] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/19/2016] [Indexed: 01/20/2023]
Abstract
Abnormally enhanced glutamatergic excitation is commonly believed to mark the onset of a focal seizure. This notion, however, is not supported by firm evidence, and it will be challenged here. A general reduction of unit firing has been indeed observed in association with low-voltage fast activity at the onset of seizures recorded during presurgical intracranial monitoring in patients with focal, drug-resistant epilepsies. Moreover, focal seizures in animal models start with increased γ-aminobutyric acid (GABA)ergic interneuronal activity that silences principal cells. In vitro studies have shown that synchronous activation of GABAA receptors occurs at seizure onset and causes sizeable elevations in extracellular potassium, thus facilitating neuronal recruitment and seizure progression. A paradoxical involvement of GABAergic networks is required for the initiation of focal seizures characterized by low-voltage fast activity, which represents the most common seizure-onset pattern in focal epilepsies.
Collapse
Affiliation(s)
| | - Massimo Avoli
- Montreal Neurological Institute, McGill University, Montréal, Quebec, Canada.,Faculty of Medicine and Dentistry, La Sapienza University, Rome, Italy
| |
Collapse
|
30
|
Abstract
This review centers on the discoveries made during more than six decades of neuroscience research on the role of gamma-amino-butyric acid (GABA) as neurotransmitter. In doing so, special emphasis is directed to the significant involvement of Canadian scientists in these advances. Starting with the early studies that established GABA as an inhibitory neurotransmitter at central synapses, we summarize the results pointing at the GABA receptor as a drug target as well as more recent evidence showing that GABAA receptor signaling plays a surprisingly active role in neuronal network synchronization, both during development and in the adult brain. Finally, we briefly address the involvement of GABA in neurological conditions that encompass epileptic disorders and mental retardation.
Collapse
|
31
|
Hypersynchronous ictal onset in the perirhinal cortex results from dynamic weakening in inhibition. Neurobiol Dis 2015; 87:1-10. [PMID: 26699817 DOI: 10.1016/j.nbd.2015.12.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 11/23/2015] [Accepted: 12/10/2015] [Indexed: 11/23/2022] Open
Abstract
We obtained field, K(+) selective and "sharp" intracellular recordings from the rat entorhinal (EC) and perirhinal (PC) cortices in an in vitro brain slice preparation to identify the events occurring at interictal-to-ictal transition during 4-aminopyridine application. Field recordings revealed interictal- (duration: 1.1 to 2.2s) and ictal-like (duration: 31 to 103s) activity occurring synchronously in EC and PC; in addition, interictal spiking in PC increased in frequency shortly before the onset of ictal oscillatory activity thus resembling the hypersynchronous seizure onset seen in epileptic patients and in in vivo animal models. Intracellular recordings with K-acetate+QX314-filled pipettes in PC principal cells showed that spikes at ictal onset had post-burst hyperpolarizations (presumably mediated by postsynaptic GABAA receptors), which gradually decreased in amplitude. This trend was associated with a progressive positive shift of the post-burst hyperpolarization reversal potential. Finally, the transient elevations in [K(+)]o (up to 4.4mM from a base line of 3.2mM) - which occurred with the interictal events in PC - progressively increased (up to 7.3mM) with the spike immediately preceding ictal onset. Our findings indicate that hypersynchronous seizure onset in rat PC is caused by dynamic weakening of GABAA receptor signaling presumably resulting from [K(+)]o accumulation.
Collapse
|
32
|
Avoli M, Jefferys JGR. Models of drug-induced epileptiform synchronization in vitro. J Neurosci Methods 2015; 260:26-32. [PMID: 26484784 DOI: 10.1016/j.jneumeth.2015.10.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2015] [Accepted: 10/11/2015] [Indexed: 11/29/2022]
Abstract
Models of epileptiform activity in vitro have many advantages for recording and experimental manipulation. Neural tissues can be maintained in vitro for hours, and in neuronal or organotypic slice cultures for several weeks. A variety of drugs and other agents increase activity in these in vitro conditions, in many cases resulting in epileptiform activity, thus providing a direct model of symptomatic seizures. We review these preparations and the experimental manipulations used to induce epileptiform activity. The most common of drugs used are GABAA receptor antagonists and potassium channel blockers (notably 4-aminopyridine). Muscarinic agents also can induce epileptiform synchronization in vitro, and include potassium channel inhibition amongst their cellular actions. Manipulations of extracellular ions are reviewed in another paper in this special issue, as are ex vivo slices prepared from chronically epileptic animals and from people with epilepsy. More complex slices including extensive networks and/or several connected brain structures can provide insights into the dynamics of long range connections during epileptic activity. Visualization of slices also provides opportunities for identification of living neurons and for optical recording/stimulation and manipulation. Overall, the analysis of the epileptiform activity induced in brain tissue in vitro has played a major role in advancing our understanding of the cellular and network mechanisms of epileptiform synchronization, and it is expected to continue to do so in future.
Collapse
Affiliation(s)
- Massimo Avoli
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery, and of Physiology, McGill University, Montréal, QC, Canada H3A 2B4; Department of Experimental Medicine, Facoltà di Medicina e Odontoiatria, Sapienza University of Rome, Roma 00185, Italy.
| | - John G R Jefferys
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| |
Collapse
|
33
|
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.
Collapse
|
34
|
Kaiser T, Ting JT, Monteiro P, Feng G. Transgenic labeling of parvalbumin-expressing neurons with tdTomato. Neuroscience 2015; 321:236-245. [PMID: 26318335 DOI: 10.1016/j.neuroscience.2015.08.036] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2015] [Revised: 08/08/2015] [Accepted: 08/18/2015] [Indexed: 12/22/2022]
Abstract
Parvalbumin (PVALB)-expressing fast-spiking interneurons subserve important roles in many brain regions by modulating circuit function and dysfunction of these neurons is strongly implicated in neuropsychiatric disorders including schizophrenia and autism. To facilitate the study of PVALB neuron function we need to be able to identify PVALB neurons in vivo. We have generated a bacterial artificial chromosome (BAC) transgenic mouse line expressing the red fluorophore tdTomato under the control of endogenous regulatory elements of the Pvalb gene locus (JAX # 027395). We show that the tdTomato transgene is faithfully expressed relative to endogenous PVALB expression throughout the brain. Furthermore, targeted patch clamp recordings confirm that the labeled populations in neocortex, striatum, and hippocampus are fast-spiking interneurons based on intrinsic properties. This new transgenic mouse line provides a useful tool to study PVALB neuron function in the normal brain as well as in mouse models of psychiatric disease.
Collapse
Affiliation(s)
- T Kaiser
- McGovern Institute for Brain Research at MIT, Cambridge, MA 02139, USA; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - J T Ting
- McGovern Institute for Brain Research at MIT, Cambridge, MA 02139, USA; Human Cell Types Department, Allen Institute for Brain Science, 551 North 34th Street, Seattle, WA 98103, USA
| | - P Monteiro
- McGovern Institute for Brain Research at MIT, Cambridge, MA 02139, USA; Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA; PhD Program in Experimental Biology and Biomedicine (PDBEB), Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
| | - G Feng
- McGovern Institute for Brain Research at MIT, Cambridge, MA 02139, USA; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA.
| |
Collapse
|
35
|
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.
Collapse
|
36
|
de Curtis M, Avoli M. Initiation, Propagation, and Termination of Partial (Focal) Seizures. Cold Spring Harb Perspect Med 2015; 5:a022368. [PMID: 26134843 PMCID: PMC4484951 DOI: 10.1101/cshperspect.a022368] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The neurophysiological patterns that correlate with partial (focal) seizures are well defined in humans by standard electroencephalogram (EEG) and presurgical depth electrode recordings. Seizure patterns with similar features are reproduced in animal models of partial seizures and epilepsy. However, the network determinants that support interictal spikes, as well as the initiation, progression, and termination of seizures, are still elusive. Recent findings show that inhibitory networks are prominently involved at the onset of these seizures, and that extracellular changes in potassium contribute to initiate and sustain seizure progression. The end of a partial seizure correlates with an increase in network synchronization, which possibly involves both excitatory and inhibitory mechanisms.
Collapse
Affiliation(s)
- Marco de Curtis
- Unit of Epileptology and Experimental Neurophysiology and Fondazione Istituto Neurologico Carlo Besta, 20133 Milano, Italy
| | - Massimo Avoli
- Montreal Neurological Institute and Departments of Neurology and Neurosurgery and Physiology, McGill University, Montréal, H3A 2B4 Québec, Canada Department of Experimental Medicine, Facoltà di Medicina e Odontoiatria, Sapienza Università di Roma, 00185 Roma, Italy
| |
Collapse
|
37
|
Synchronous inhibitory potentials precede seizure-like events in acute models of focal limbic seizures. J Neurosci 2015; 35:3048-55. [PMID: 25698742 DOI: 10.1523/jneurosci.3692-14.2015] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Interictal spikes in models of focal seizures and epilepsies are sustained by the synchronous activation of glutamatergic and GABAergic networks. The nature of population spikes associated with seizure initiation (pre-ictal spikes; PSs) is still undetermined. We analyzed the networks involved in the generation of both interictal and PSs in acute models of limbic cortex ictogenesis induced by pharmacological manipulations. Simultaneous extracellular and intracellular recordings from both principal cells and interneurons were performed in the medial entorhinal cortex of the in vitro isolated guinea pig brain during focal interictal and ictal discharges induced in the limbic network by intracortical and brief arterial infusions of either bicuculline methiodide (BMI) or 4-aminopyridine (4AP). Local application of BMI in the entorhinal cortex did not induce seizure-like events (SLEs), but did generate periodic interictal spikes sensitive to the glutamatergic non-NMDA receptor antagonist DNQX. Unlike local applications, arterial perfusion of either BMI or 4AP induced focal limbic SLEs. PSs just ahead of SLE were associated with hyperpolarizing potentials coupled with a complete blockade of firing in principal cells and burst discharges in putative interneurons. Interictal population spikes recorded from principal neurons between two SLEs correlated with a depolarizing potential. We demonstrate in two models of acute limbic SLE that PS events are different from interictal spikes and are sustained by synchronous activation of inhibitory networks. Our findings support a prominent role of synchronous network inhibition in the initiation of a focal seizure.
Collapse
|
38
|
Avoli M. Mechanisms of epileptiform synchronization in cortical neuronal networks. Curr Med Chem 2014; 21:653-62. [PMID: 24251567 DOI: 10.2174/0929867320666131119151136] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 07/01/2013] [Accepted: 07/04/2013] [Indexed: 12/31/2022]
Abstract
Neuronal synchronization supports different physiological states such as cognitive functions and sleep, and it is mirrored by identifiable EEG patterns ranging from gamma to delta oscillations. However, excessive neuronal synchronization is often the hallmark of epileptic activity in both generalized and partial epileptic disorders. Here, I will review the synchronizing mechanisms involved in generating epileptiform activity in the limbic system, which is closely involved in the pathophysiogenesis of temporal lobe epilepsy (TLE). TLE is often associated to a typical pattern of brain damage known as mesial temporal sclerosis, and it is one of the most refractory adult form of partial epilepsy. This epileptic disorder can be reproduced in animals by topical or systemic injection of pilocarpine or kainic acid, or by repetitive electrical stimulation; these procedures induce an initial status epilepticus and cause 1-4 weeks later a chronic condition of recurrent limbic seizures. Remarkably, a similar, seizure-free, latent period can be identified in TLE patients who suffered an initial insult in childhood and develop partial seizures in adolescence or early adulthood. Specifically, I will focus here on the neuronal mechanisms underlying three abnormal types of neuronal synchronization seen in both TLE patients and animal models mimicking this disorder: (i) interictal spikes; (ii) high frequency oscillations (80-500 Hz); and (iii) ictal (i.e., seizure) discharges. In addition, I will discuss the relationship between interictal spikes and ictal activity as well as recent evidence suggesting that specific seizure onsets in the pilocarpine model of TLE are characterized by distinctive patterns of spiking (also termed preictal) and high frequency oscillations.
Collapse
Affiliation(s)
- M Avoli
- Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, PQ, Canada, H3A 2B4.
| |
Collapse
|
39
|
Mikkelsen K, Imparato A, Torcini A. Sisyphus effect in pulse-coupled excitatory neural networks with spike-timing-dependent plasticity. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:062701. [PMID: 25019808 DOI: 10.1103/physreve.89.062701] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Indexed: 06/03/2023]
Abstract
The collective dynamics of excitatory pulse-coupled neural networks with spike-timing-dependent plasticity (STDP) is studied. Depending on the model parameters stationary states characterized by high or low synchronization can be observed. In particular, at the transition between these two regimes, persistent irregular low frequency oscillations between strongly and weakly synchronized states are observable, which can be identified as infraslow oscillations with frequencies ≃0.02-0.03 Hz. Their emergence can be explained in terms of the Sisyphus effect, a mechanism caused by a continuous feedback between the evolution of the coherent population activity and of the average synaptic weight. Due to this effect, the synaptic weights have oscillating equilibrium values, which prevents the neuronal population from relaxing into a stationary macroscopic state.
Collapse
Affiliation(s)
- Kaare Mikkelsen
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, Building 1520, DK-8000 Aarhus C, Denmark
| | - Alberto Imparato
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, Building 1520, DK-8000 Aarhus C, Denmark
| | - Alessandro Torcini
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, Building 1520, DK-8000 Aarhus C, Denmark and CNR-Consiglio Nazionale delle Ricerche-Istituto dei Sistemi Complessi, via Madonna del Piano 10, I-50019 Sesto Fiorentino, Italy and INFN Sez. Firenze, via Sansone 1, I-50019 Sesto Fiorentino, Italy
| |
Collapse
|
40
|
Extracellular calcium controls the expression of two different forms of ripple-like hippocampal oscillations. J Neurosci 2014; 34:2989-3004. [PMID: 24553939 DOI: 10.1523/jneurosci.2826-13.2014] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Hippocampal high-frequency oscillations (HFOs) are prominent in physiological and pathological conditions. During physiological ripples (100-200 Hz), few pyramidal cells fire together coordinated by rhythmic inhibitory potentials. In the epileptic hippocampus, fast ripples (>200 Hz) reflect population spikes (PSs) from clusters of bursting cells, but HFOs in the ripple and the fast ripple range are vastly intermixed. What is the meaning of this frequency range? What determines the expression of different HFOs? Here, we used different concentrations of Ca(2+) in a physiological range (1-3 mM) to record local field potentials and single cells in hippocampal slices from normal rats. Surprisingly, we found that this sole manipulation results in the emergence of two forms of HFOs reminiscent of ripples and fast ripples recorded in vivo from normal and epileptic rats, respectively. We scrutinized the cellular correlates and mechanisms underlying the emergence of these two forms of HFOs by combining multisite, single-cell and paired-cell recordings in slices prepared from a rat reporter line that facilitates identification of GABAergic cells. We found a major effect of extracellular Ca(2+) in modulating intrinsic excitability and disynaptic inhibition, two critical factors shaping network dynamics. Moreover, locally modulating the extracellular Ca(2+) concentration in an in vivo environment had a similar effect on disynaptic inhibition, pyramidal cell excitability, and ripple dynamics. Therefore, the HFO frequency band reflects a range of firing dynamics of hippocampal networks.
Collapse
|
41
|
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.
Collapse
|
42
|
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(+).
Collapse
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.
| |
Collapse
|
43
|
Rotstein HG. Abrupt and gradual transitions between low and hyperexcited firing frequencies in neuronal models with fast synaptic excitation: a comparative study. CHAOS (WOODBURY, N.Y.) 2013; 23:046104. [PMID: 24387583 DOI: 10.1063/1.4824320] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Hyperexcitability of neuronal networks is one of the hallmarks of epileptic brain seizure generation, and results from a net imbalance between excitation and inhibition that promotes excessive abnormal firing frequencies. The transition between low and high firing frequencies as the levels of recurrent AMPA excitation change can occur either gradually or abruptly. We used modeling, numerical simulations, and dynamical systems tools to investigate the biophysical and dynamic mechanisms that underlie these two identified modes of transition in recurrently connected neurons via AMPA excitation. We compare our results and demonstrate that these two modes of transition are qualitatively different and can be linked to different intrinsic properties of the participating neurons.
Collapse
Affiliation(s)
- Horacio G Rotstein
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, New Jersey 07102, USA
| |
Collapse
|
44
|
Suls A, Jaehn J, Kecskés A, Weber Y, Weckhuysen S, Craiu D, Siekierska A, Djémié T, Afrikanova T, Gormley P, von Spiczak S, Kluger G, Iliescu C, Talvik T, Talvik I, Meral C, Caglayan H, Giraldez B, Serratosa J, Lemke J, Hoffman-Zacharska D, Szczepanik E, Barisic N, Komarek V, Hjalgrim H, Møller R, Linnankivi T, Dimova P, Striano P, Zara F, Marini C, Guerrini R, Depienne C, Baulac S, Kuhlenbäumer G, Crawford A, Lehesjoki AE, de Witte P, Palotie A, Lerche H, Esguerra C, De Jonghe P, Helbig I. De novo loss-of-function mutations in CHD2 cause a fever-sensitive myoclonic epileptic encephalopathy sharing features with Dravet syndrome. Am J Hum Genet 2013; 93:967-75. [PMID: 24207121 PMCID: PMC3824114 DOI: 10.1016/j.ajhg.2013.09.017] [Citation(s) in RCA: 148] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Revised: 05/28/2013] [Accepted: 09/30/2013] [Indexed: 11/18/2022] Open
Abstract
Dravet syndrome is a severe epilepsy syndrome characterized by infantile onset of therapy-resistant, fever-sensitive seizures followed by cognitive decline. Mutations in SCN1A explain about 75% of cases with Dravet syndrome; 90% of these mutations arise de novo. We studied a cohort of nine Dravet-syndrome-affected individuals without an SCN1A mutation (these included some atypical cases with onset at up to 2 years of age) by using whole-exome sequencing in proband-parent trios. In two individuals, we identified a de novo loss-of-function mutation in CHD2 (encoding chromodomain helicase DNA binding protein 2). A third CHD2 mutation was identified in an epileptic proband of a second (stage 2) cohort. All three individuals with a CHD2 mutation had intellectual disability and fever-sensitive generalized seizures, as well as prominent myoclonic seizures starting in the second year of life or later. To explore the functional relevance of CHD2 haploinsufficiency in an in vivo model system, we knocked down chd2 in zebrafish by using targeted morpholino antisense oligomers. chd2-knockdown larvae exhibited altered locomotor activity, and the epileptic nature of this seizure-like behavior was confirmed by field-potential recordings that revealed epileptiform discharges similar to seizures in affected persons. Both altered locomotor activity and epileptiform discharges were absent in appropriate control larvae. Our study provides evidence that de novo loss-of-function mutations in CHD2 are a cause of epileptic encephalopathy with generalized seizures.
Collapse
Affiliation(s)
- Arvid Suls
- Neurogenetics group, Department of Molecular Genetics, VIB, 2610 Antwerp, Belgium
- Laboratory of Neurogenetics, Institute Born-Bunge, University of Antwerp, 2610 Antwerp, Belgium
| | - Johanna A. Jaehn
- University Medical Center Schleswig-Holstein, Christian-Albrechts University, 24105 Kiel, Germany
| | - Angela Kecskés
- Laboratory for Molecular Biodiscovery, Department of Pharmaceutical and Pharmacological Sciences, University of Leuven, 3000 Leuven, Belgium
| | - Yvonne Weber
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, 72076 Tübingen, Germany
| | - Sarah Weckhuysen
- Neurogenetics group, Department of Molecular Genetics, VIB, 2610 Antwerp, Belgium
- Laboratory of Neurogenetics, Institute Born-Bunge, University of Antwerp, 2610 Antwerp, Belgium
| | - Dana C. Craiu
- Pediatric Neurology Clinic II, Departments of Neurology, Pediatric Neurology, Psychiatry, and Neurosurgery, “Carol Davila” University of Medicine, Sector 4, 050474 Bucharest, Romania
- Pediatric Neurology Clinic, “Professor Doctor Alexandru Obregia” Clinical Hospital, Sector 4, 041914 Bucharest, Romania
| | - Aleksandra Siekierska
- Laboratory for Molecular Biodiscovery, Department of Pharmaceutical and Pharmacological Sciences, University of Leuven, 3000 Leuven, Belgium
| | - Tania Djémié
- Neurogenetics group, Department of Molecular Genetics, VIB, 2610 Antwerp, Belgium
- Laboratory of Neurogenetics, Institute Born-Bunge, University of Antwerp, 2610 Antwerp, Belgium
| | - Tatiana Afrikanova
- Laboratory for Molecular Biodiscovery, Department of Pharmaceutical and Pharmacological Sciences, University of Leuven, 3000 Leuven, Belgium
| | - Padhraig Gormley
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridgeshire CB10 1SA, UK
| | - Sarah von Spiczak
- University Medical Center Schleswig-Holstein, Christian-Albrechts University, 24105 Kiel, Germany
| | - Gerhard Kluger
- Neuropädiatrie und Neurologische Rehabilitation, Epilepsiezentrum für Kinder und Jugendliche, Tagesklinik für Neuropädiatrie, Schön Klinik Vogtareuth, 83569 Vogtareuth, Germany
| | - Catrinel M. Iliescu
- Pediatric Neurology Clinic II, Departments of Neurology, Pediatric Neurology, Psychiatry, and Neurosurgery, “Carol Davila” University of Medicine, Sector 4, 050474 Bucharest, Romania
- Pediatric Neurology Clinic, “Professor Doctor Alexandru Obregia” Clinical Hospital, Sector 4, 041914 Bucharest, Romania
| | - Tiina Talvik
- Department of Pediatrics, University of Tartu, 51014 Tartu, Estonia
- Department of Neurology and Neurorehabilitation, Children’s Clinic, Tartu University Hospital, 50406 Tartu, Estonia
| | - Inga Talvik
- Department of Pediatrics, University of Tartu, 51014 Tartu, Estonia
- Department of Neurology and Neurorehabilitation, Children’s Clinic, Tartu University Hospital, 50406 Tartu, Estonia
| | - Cihan Meral
- Department of Pediatric Neurology, GATA Haydarpasa Teaching Hospital, 34668 Istanbul, Turkey
| | - Hande S. Caglayan
- Department of Molecular Biology and Genetics, Bogazici University, 34342 Istanbul, Turkey
| | - Beatriz G. Giraldez
- Epilepsy Unit, Hospital Universitario Fundación Jiménez Diaz and Centro De Investigación Biomédica En Red De Enfermedades Raras, 28040 Madrid, Spain
| | - José Serratosa
- Epilepsy Unit, Hospital Universitario Fundación Jiménez Diaz and Centro De Investigación Biomédica En Red De Enfermedades Raras, 28040 Madrid, Spain
| | - Johannes R. Lemke
- Division of Human Genetics, University Children’s Hospital Inselspital, 3010 Bern, Switzerland
| | | | - Elzbieta Szczepanik
- Clinic of Neurology of Child and Adolescents, Institute of Mother and Child, 01211 Warsaw, Poland
| | - Nina Barisic
- Department of Paediatrics, University of Zagreb School of Medicine, University Hospital Centre Zagreb, 10000 Zagreb, Croatia
| | - Vladimir Komarek
- Child Neurology Department, University Hospital Motol, 150 06 Praha, Czech Republic
| | - Helle Hjalgrim
- Danish Epilepsy Centre, 4293 Dianalund, Denmark
- Institute for Regional Health research, University of Southern Denmark, 5230 Odense, Denmark
| | | | - Tarja Linnankivi
- Pediatric Neurology, Children’s Hospital, University of Helsinki and Helsinki University Central Hospital, 00029 Helsinki, Finland
| | - Petia Dimova
- Clinic of Child Neurology, St. Naum University Hospital of Neurology and Psychiatry, 1113 Sofia, Bulgaria
| | - Pasquale Striano
- Pediatric Neurology and Muscular Diseases Unit, Departments of Neurosciences, Rehabilitation, Ophtalmology, Genetics, and Maternal and Child Health, University of Genova and Gaslini Institute, 16147 Genova, Italy
| | - Federico Zara
- Laboratory of Neurogenetics, Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Gaslini Institute, 16147 Genova, Italy
| | - Carla Marini
- Pediatric Neurology Unit and Laboratories, Meyer Children’s Hospital, University of Florence, 50132 Florence, Italy
| | - Renzo Guerrini
- Pediatric Neurology Unit and Laboratories, Meyer Children’s Hospital, University of Florence, 50132 Florence, Italy
| | - Christel Depienne
- Institut National de la Santé et de la Recherche Médicale U975, Centre de Recherche de l’Institut du Cerveau et de la Moelle Epinière, Hôpital Pitié-Salpêtrière, 75013 Paris, France
- Centre National de la Recherche Scientifique 7225, Centre de Recherche de l’Institut du Cerveau et de la Moelle Epinière, Hôpital Pitié-Salpêtrière, 75013 Paris, France
- Département de Génétique et de Cytogénétique, Unité Fonctionnelle de Neurogénétique Moléculaire et Cellulaire, Hôpital Pitié-Salpêtrière, Assistance Publique – Hôpitaux de Paris, 75013 Paris, France
| | - Stéphanie Baulac
- Institut National de la Santé et de la Recherche Médicale U975, Centre de Recherche de l’Institut du Cerveau et de la Moelle Epinière, Hôpital Pitié-Salpêtrière, 75013 Paris, France
- Centre National de la Recherche Scientifique 7225, Centre de Recherche de l’Institut du Cerveau et de la Moelle Epinière, Hôpital Pitié-Salpêtrière, 75013 Paris, France
- Université Pierre et Marie Curie (Paris VI), UMR_S 975, 75013 Paris, France
| | - Gregor Kuhlenbäumer
- Department of Neurology, Institute of Experimental Medicine, Christian-Albrechts University of Kiel, 24105 Kiel, Germany
| | - Alexander D. Crawford
- Laboratory for Molecular Biodiscovery, Department of Pharmaceutical and Pharmacological Sciences, University of Leuven, 3000 Leuven, Belgium
- Luxembourg Center for Systems Biomedicine, University of Luxembourg, L-4362 Esch-sur-Alzette, Luxembourg
| | - Anna-Elina Lehesjoki
- Folkhälsan Institute of Genetics, 00290 Helsinki, Finland
- Research Programs Unit, Molecular Neurology, University of Helsinki, 00290 Helsinki, Finland
- Neuroscience Center, University of Helsinki, 00290 Helsinki, Finland
| | - Peter A.M. de Witte
- Laboratory for Molecular Biodiscovery, Department of Pharmaceutical and Pharmacological Sciences, University of Leuven, 3000 Leuven, Belgium
| | - Aarno Palotie
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridgeshire CB10 1SA, UK
- Institute for Molecular Medicine Finland, University of Helsinki, 00290 Helsinki, Finland
- Program in Medical and Population Genetics and Genetic Analysis Platform, The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Holger Lerche
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, 72076 Tübingen, Germany
| | - Camila V. Esguerra
- Laboratory for Molecular Biodiscovery, Department of Pharmaceutical and Pharmacological Sciences, University of Leuven, 3000 Leuven, Belgium
| | - Peter De Jonghe
- Neurogenetics group, Department of Molecular Genetics, VIB, 2610 Antwerp, Belgium
- Laboratory of Neurogenetics, Institute Born-Bunge, University of Antwerp, 2610 Antwerp, Belgium
| | - Ingo Helbig
- University Medical Center Schleswig-Holstein, Christian-Albrechts University, 24105 Kiel, Germany
| |
Collapse
|
45
|
Deconstructing the neural and ionic involvement of seizure-like events in the striatal network. Neurobiol Dis 2013; 52:128-36. [DOI: 10.1016/j.nbd.2012.11.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 11/28/2012] [Indexed: 02/07/2023] Open
|
46
|
Uva L, Trombin F, Carriero G, Avoli M, de Curtis M. Seizure-like discharges induced by 4-aminopyridine in the olfactory system of the in vitro isolated guinea pig brain. Epilepsia 2013; 54:605-15. [PMID: 23505998 DOI: 10.1111/epi.12133] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/23/2013] [Indexed: 11/26/2022]
Abstract
PURPOSE The study of the interactions leading to network- or region-specific propagation of seizures is crucial to understand ictogenesis. We have recently found that systemic (arterial) application of the potassium channel blocker, 4-aminopyridine (4AP), induces different and independent seizure activities in olfactory and in limbic structures. Here, we have characterized the network and cellular features that support 4AP-induced seizure-like events in the olfactory cortex. METHODS Simultaneous extracellular recordings were performed from the piriform cortex, the entorhinal cortex, the olfactory tubercle, and the amygdala of the in vitro isolated guinea pig brain preparation. Intracellular, sharp electrode recordings were obtained from neurons of different layers of the region of ictal onset, the piriform cortex. Seizure-like discharges were induced by both arterial perfusion and local intracortical injections of 4AP. KEY FINDINGS Arterial application of 4AP induces independent seizure activities in limbic and olfactory cortices. Both local applications of 4AP and cortico-cortical disconnections demonstrated that region-specific seizure-like events initiated in the primary olfactory cortex and propagate to anatomically related areas. Seizures induced by arterial administration of 4-AP are preceded by runs of fast activity at circa 30-40 Hz and are independently generated in the hemispheres. Simultaneous extracellular and intracellular recordings in the piriform cortex revealed that the onset of seizure correlates with (1) a gradual amplitude increase of fast activity runs, (2) a large intracellular depolarization with action potential firing of superficial layer neurons, and (3) no firing in a subpopulation of deep layers neurons. During the ictal event, neuronal firing was abolished for 10-30 s in all neurons and gradually restored and synchronized before seizure termination. SIGNIFICANCE Our data show that olfactory neuronal networks sustain the generation of seizure-like activities that are independent from those observed in adjacent and connected limbic cortex regions. The data support the concept that functionally and anatomically hard-wired networks generate region-specific seizure patterns that could be substrates for system epilepsy.
Collapse
Affiliation(s)
- Laura Uva
- Unit of Experimental Epileptology and Neurophysiology, Fondazione Istituto Neurologico Carlo Besta, Milan, Italy
| | | | | | | | | |
Collapse
|
47
|
SERLETIS DEMITRE, CARLEN PETERL, VALIANTE TAUFIKA, BARDAKJIAN BERJL. PHASE SYNCHRONIZATION OF NEURONAL NOISE IN MOUSE HIPPOCAMPAL EPILEPTIFORM DYNAMICS. Int J Neural Syst 2012; 23:1250033. [DOI: 10.1142/s0129065712500335] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Organized brain activity is the result of dynamical, segregated neuronal signals that may be used to investigate synchronization effects using sophisticated neuroengineering techniques. Phase synchrony analysis, in particular, has emerged as a promising methodology to study transient and frequency-specific coupling effects across multi-site signals. In this study, we investigated phase synchronization in intracellular recordings of interictal and ictal epileptiform events recorded from pairs of cells in the whole (intact) mouse hippocampus. In particular, we focused our analysis on the background noise-like activity (NLA), previously reported to exhibit complex neurodynamical properties. Our results show evidence for increased linear and nonlinear phase coupling in NLA across three frequency bands [theta (4–10 Hz), beta (12–30 Hz) and gamma (30–80 Hz)] in the ictal compared to interictal state dynamics. We also present qualitative and statistical evidence for increased phase synchronization in the theta, beta and gamma frequency bands from paired recordings of ictal NLA. Overall, our results validate the use of background NLA in the neurodynamical study of epileptiform transitions and suggest that what is considered "neuronal noise" is amenable to synchronization effects in the spatiotemporal domain.
Collapse
Affiliation(s)
- DEMITRE SERLETIS
- Neurological Institute, Epilepsy Center, Cleveland Clinic, Ohio 44195, USA
| | - PETER L. CARLEN
- Division of Neurology, Toronto Western Hospital, Ontario M5T 2S8, Canada
- Department of Physiology, University of Toronto, Ontario M5S 1A8, Canada
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Ontario M5S 3G9, Canada
| | - TAUFIK A. VALIANTE
- Division of Neurosurgery, Toronto Western Hospital, Ontario M5T 2S8, Canada
| | - BERJ L. BARDAKJIAN
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Ontario M5S 3G9, Canada
| |
Collapse
|
48
|
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.
Collapse
Affiliation(s)
- Jokubas Žiburkus
- Department of Biology and Biochemistry, University of Houston, Houston, TX, USA.
| | | | | |
Collapse
|
49
|
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: 121] [Impact Index Per Article: 10.1] [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.
Collapse
Affiliation(s)
- Mario Cammarota
- Institute of Neuroscience, National Research Council and Department of Biomedical Sciences, University of Padova, Padova, Italy
| | | | | | | | | |
Collapse
|
50
|
Transition to seizure: ictal discharge is preceded by exhausted presynaptic GABA release in the hippocampal CA3 region. J Neurosci 2012; 32:2499-512. [PMID: 22396423 DOI: 10.1523/jneurosci.4247-11.2012] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
How the brain transitions into a seizure is poorly understood. Recurrent seizure-like events (SLEs) in low-Mg2+/ high-K+ perfusate were measured in the CA3 region of the intact mouse hippocampus. The SLE was divided into a "preictal phase," which abruptly turns into a higher frequency "ictal" phase. Blockade of GABA(A) receptors shortened the preictal phase, abolished interictal bursts, and attenuated the slow preictal depolarization, with no effect on the ictal duration, whereas SLEs were blocked by glutamate receptor blockade. In CA3 pyramidal cells and stratum oriens non-fast-spiking and fast-spiking interneurons, recurrent GABAergic IPSCs predominated interictally and during the early preictal phase, synchronous with extracellularly measured recurrent field potentials (FPs). These IPSCs then decreased to zero or reversed polarity by the onset of the higher-frequency ictus. However, postsynaptic muscimol-evoked GABA(A) responses remained intact. Simultaneously, EPSCs synchronous with the FPs markedly increased to a maximum at the ictal onset. The reversal potential of the compound postsynaptic currents (combined simultaneous EPSCs and IPSCs) became markedly depolarized during the preictal phase, whereas the muscimol-evoked GABA(A) reversal potential remained unchanged. During the late preictal phase, interneuronal excitability was high, but IPSCs, evoked by local stimulation, or osmotically by hypertonic sucrose application, were diminished, disappearing at the ictal onset. We conclude that the interictal and early preictal states are dominated by GABAergic activity, with the onset of the ictus heralded by exhaustion of presynaptic release of GABA, and unopposed increased glutamatergic responses.
Collapse
|