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He W, Wang QH, Li JW, Wang YY, Luo XM, Wan L, Wang J, Shi XY, Zhang WH, Fang F, Zou LP. Adrenocorticotropic hormone combined with magnesium sulfate therapy for infantile epileptic spasms syndrome: a real-world study. World J Pediatr 2024; 20:834-847. [PMID: 38070098 PMCID: PMC11402841 DOI: 10.1007/s12519-023-00771-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 10/08/2023] [Indexed: 09/16/2024]
Abstract
BACKGROUND Infantile epileptic spasms syndrome (IESS) is a serious disease in infants, and it usually evolves to other epilepsy types or syndromes, especially refractory or super-refractory focal epilepsies. Although adrenocorticotropic hormone (ACTH) is one of the first-line and effective treatment plans for IESS, it has serious side effects and is not sufficiently effective. METHODS A retrospective study of the clinical outcomes of ACTH combined with magnesium sulfate (MgSO4) therapy for IESS in two hospital centers was conducted. The major outcome of the single and combined treatment was evaluated by changes in seizure frequency and improvements in hypsarrhythmia electroencephalography (EEG). To reduce the confounding bias between the two groups, we used SPSS for the propensity score matching (PSM) analysis. RESULTS We initially recruited 1205 IESS patients from two Chinese hospitals and treated them with ACTH combined with MgSO4 and ACTH alone. Only 1005 patients were enrolled in the treatment (ACTH combined with MgSO4: 744, ACTH: 261), and both treatment plans had a more than 55% response rate. However, compared to patients treated with ACTH alone, those patients treated with ACTH combined with MgSO4 had better performance in terms of the seizure frequency and hypsarrhythmia EEG. After PSM, the two groups also showed significant differences in responder rate [70.8% (95% confidence interval, CI) = 66.7%-74.8%) vs. 53.8% (95% CI = 47.4%-60.2%), P < 0.001], seizure frequency (P < 0.001) and hypsarrhythmia EEG resolution (P < 0.001). Notably, multivariate analysis revealed that the lead time to treatment and the number of antiseizure medications taken before treatment were two factors that may affect the clinical outcome. Patients with less than 3 months of lead time responded to the treatment much better than those with > 3 months (P < 0.05). In addition, the overall incidence of adverse reactions in the ACTH combined with MgSO4 group was much lower than that in the ACTH group (31.4% vs. 63.1%, P < 0.001). During the treatment, only infection (P = 0.045) and hypertension (P = 0.025) were significantly different between the two groups, and no baby died. CONCLUSION Our findings support that ACTH combined with MgSO4 is a more effective short-term treatment protocol for patients with IESS than ACTH alone, especially for those patients with short lead times to treatment. Video Abstract (MP4 533623 KB).
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Affiliation(s)
- Wen He
- Senior Department of Pediatrics, the Seventh Medical Center of Chinese PLA General Hospital, Department of Pediatrics, the First Medical Center of Chinese PLA General Hospital, Beijing 100853, China
| | - Qiu-Hong Wang
- Senior Department of Pediatrics, the Seventh Medical Center of Chinese PLA General Hospital, Department of Pediatrics, the First Medical Center of Chinese PLA General Hospital, Beijing 100853, China
| | - Jiu-Wei Li
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, Beijing, China
| | - Yang-Yang Wang
- Senior Department of Pediatrics, the Seventh Medical Center of Chinese PLA General Hospital, Department of Pediatrics, the First Medical Center of Chinese PLA General Hospital, Beijing 100853, China
| | - Xiao-Mei Luo
- Center of Epilepsy, Beijing Institute for Brain Disorders, Beijing 100069, China
| | - Lin Wan
- Senior Department of Pediatrics, the Seventh Medical Center of Chinese PLA General Hospital, Department of Pediatrics, the First Medical Center of Chinese PLA General Hospital, Beijing 100853, China
| | - Jing Wang
- Senior Department of Pediatrics, the Seventh Medical Center of Chinese PLA General Hospital, Department of Pediatrics, the First Medical Center of Chinese PLA General Hospital, Beijing 100853, China
| | - Xiu-Yu Shi
- Senior Department of Pediatrics, the Seventh Medical Center of Chinese PLA General Hospital, Department of Pediatrics, the First Medical Center of Chinese PLA General Hospital, Beijing 100853, China
| | - Wei-Hua Zhang
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, Beijing, China
| | - Fang Fang
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, Beijing, China.
| | - Li-Ping Zou
- Senior Department of Pediatrics, the Seventh Medical Center of Chinese PLA General Hospital, Department of Pediatrics, the First Medical Center of Chinese PLA General Hospital, Beijing 100853, China.
- Center of Epilepsy, Beijing Institute for Brain Disorders, Beijing 100069, China.
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2
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Morris G, Avoli M, Bernard C, Connor K, de Curtis M, Dulla CG, Jefferys JGR, Psarropoulou C, Staley KJ, Cunningham MO. Can in vitro studies aid in the development and use of antiseizure therapies? A report of the ILAE/AES Joint Translational Task Force. Epilepsia 2023; 64:2571-2585. [PMID: 37642296 DOI: 10.1111/epi.17744] [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: 06/06/2023] [Revised: 08/11/2023] [Accepted: 08/11/2023] [Indexed: 08/31/2023]
Abstract
In vitro preparations (defined here as cultured cells, brain slices, and isolated whole brains) offer a variety of approaches to modeling various aspects of seizures and epilepsy. Such models are particularly amenable to the application of anti-seizure compounds, and consequently are a valuable tool to screen the mechanisms of epileptiform activity, mode of action of known anti-seizure medications (ASMs), and the potential efficacy of putative new anti-seizure compounds. Despite these applications, all disease models are a simplification of reality and are therefore subject to limitations. In this review, we summarize the main types of in vitro models that can be used in epilepsy research, describing key methodologies as well as notable advantages and disadvantages of each. We argue that a well-designed battery of in vitro models can form an effective and potentially high-throughput screening platform to predict the clinical usefulness of ASMs, and that in vitro models are particularly useful for interrogating mechanisms of ASMs. To conclude, we offer several key recommendations that maximize the potential value of in vitro models in ASM screening. This includes the use of multiple in vitro tests that can complement each other, carefully combined with in vivo studies, the use of tissues from chronically epileptic (rather than naïve wild-type) animals, and the integration of human cell/tissue-derived preparations.
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Affiliation(s)
- Gareth Morris
- Division of Neuroscience, Faculty of Biology, Medicine and Health, School of Biological Sciences, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Massimo Avoli
- Montreal Neurological Institute-Hospital and Departments of Neurology & Neurosurgery, McGill University, Montréal, Quebec, Canada
- Department of Physiology, McGill University, Montréal, Quebec, Canada
| | - Christophe Bernard
- Inserm, INS, Institut de Neurosciences des Systèmes, Aix Marseille Univ, Marseille, France
| | - Kate Connor
- Discipline of Physiology, School of Medicine, Trinity College Dublin, Dublin 2, Ireland
| | - Marco de Curtis
- Epilepsy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Chris G Dulla
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - John G R Jefferys
- Department of Physiology, 2nd Medical School, Motol, Charles University, Prague, Czech Republic
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Caterina Psarropoulou
- Laboratory of Animal and Human Physiology, Department of Biological Applications and Technology, Faculty of Health Sciences, University of Ioannina, Ioannina, Greece
| | - Kevin J Staley
- Neurology Department, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Mark O Cunningham
- Discipline of Physiology, School of Medicine, Trinity College Dublin, Dublin 2, Ireland
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3
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A unified physiological framework of transitions between seizures, sustained ictal activity and depolarization block at the single neuron level. J Comput Neurosci 2022; 50:33-49. [PMID: 35031915 PMCID: PMC8818009 DOI: 10.1007/s10827-022-00811-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Revised: 11/10/2021] [Accepted: 01/03/2022] [Indexed: 10/29/2022]
Abstract
The majority of seizures recorded in humans and experimental animal models can be described by a generic phenomenological mathematical model, the Epileptor. In this model, seizure-like events (SLEs) are driven by a slow variable and occur via saddle node (SN) and homoclinic bifurcations at seizure onset and offset, respectively. Here we investigated SLEs at the single cell level using a biophysically relevant neuron model including a slow/fast system of four equations. The two equations for the slow subsystem describe ion concentration variations and the two equations of the fast subsystem delineate the electrophysiological activities of the neuron. Using extracellular K+ as a slow variable, we report that SLEs with SN/homoclinic bifurcations can readily occur at the single cell level when extracellular K+ reaches a critical value. In patients and experimental models, seizures can also evolve into sustained ictal activity (SIA) and depolarization block (DB), activities which are also parts of the dynamic repertoire of the Epileptor. Increasing extracellular concentration of K+ in the model to values found during experimental status epilepticus and DB, we show that SIA and DB can also occur at the single cell level. Thus, seizures, SIA, and DB, which have been first identified as network events, can exist in a unified framework of a biophysical model at the single neuron level and exhibit similar dynamics as observed in the Epileptor.Author Summary: Epilepsy is a neurological disorder characterized by the occurrence of seizures. Seizures have been characterized in patients in experimental models at both macroscopic and microscopic scales using electrophysiological recordings. Experimental works allowed the establishment of a detailed taxonomy of seizures, which can be described by mathematical models. We can distinguish two main types of models. Phenomenological (generic) models have few parameters and variables and permit detailed dynamical studies often capturing a majority of activities observed in experimental conditions. But they also have abstract parameters, making biological interpretation difficult. Biophysical models, on the other hand, use a large number of variables and parameters due to the complexity of the biological systems they represent. Because of the multiplicity of solutions, it is difficult to extract general dynamical rules. In the present work, we integrate both approaches and reduce a detailed biophysical model to sufficiently low-dimensional equations, and thus maintaining the advantages of a generic model. We propose, at the single cell level, a unified framework of different pathological activities that are seizures, depolarization block, and sustained ictal activity.
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4
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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]
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Shivacharan RS, Chiang CC, Zhang M, Gonzalez-Reyes LE, Durand DM. Self-propagating, non-synaptic epileptiform activity recruits neurons by endogenous electric fields. Exp Neurol 2019; 317:119-128. [PMID: 30776338 DOI: 10.1016/j.expneurol.2019.02.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 01/18/2019] [Accepted: 02/08/2019] [Indexed: 01/23/2023]
Abstract
It is well documented that synapses play a significant role in the transmission of information between neurons. However, in the absence of synaptic transmission, neural activity has been observed to continue to propagate. Previous studies have shown that propagation of epileptiform activity takes place in the absence of synaptic transmission and gap junctions and is outside the range of ionic diffusion and axonal conduction. Computer simulations indicate that electric field coupling could be responsible for the propagation of neural activity under pathological conditions such as epilepsy. Electric fields can modulate neuronal membrane voltage, but there is no experimental evidence suggesting that electric field coupling can mediate self-regenerating propagation of neural activity. Here we examine the role of electric field coupling by eliminating all forms of neural communications except electric field coupling with a cut through the neural tissue. We show that 4-AP induced activity generates an electric field capable of recruiting neurons on the distal side of the cut. Experiments also show that applied electric fields with amplitudes similar to endogenous values can induce propagating waves. Finally, we show that canceling the electrical field at a given point can block spontaneous propagation. The results from these in vitro electrophysiology experiments suggest that electric field coupling is a critical mechanism for non-synaptic neural propagation and therefore could contribute to the propagation of epileptic activity in the brain.
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Affiliation(s)
- Rajat S Shivacharan
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Chia-Chu Chiang
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Mingming Zhang
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Luis E Gonzalez-Reyes
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Dominique M Durand
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.
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6
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Dulla CG, Janigro D, Jiruska P, Raimondo JV, Ikeda A, Lin CCK, Goodkin HP, Galanopoulou AS, Bernard C, de Curtis M. How do we use in vitro models to understand epileptiform and ictal activity? A report of the TASK1-WG4 group of the ILAE/AES Joint Translational Task Force. Epilepsia Open 2018; 3:460-473. [PMID: 30525115 PMCID: PMC6276782 DOI: 10.1002/epi4.12277] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/27/2018] [Indexed: 02/06/2023] Open
Abstract
In vitro brain tissue preparations allow the convenient and affordable study of brain networks and have allowed us to garner molecular, cellular, and electrophysiologic insights into brain function with a detail not achievable in vivo. Preparations from both rodent and human postsurgical tissue have been utilized to generate in vitro electrical activity similar to electrographic activity seen in patients with epilepsy. A great deal of knowledge about how brain networks generate various forms of epileptiform activity has been gained, but due to the multiple in vitro models and manipulations used, there is a need for a standardization across studies. Here, we describe epileptiform patterns generated using in vitro brain preparations, focusing on issues and best practices pertaining to recording, reporting, and interpretation of the electrophysiologic patterns observed. We also discuss criteria for defining in vitro seizure‐like patterns (i.e., ictal) and interictal discharges. Unifying terminologies and definitions are proposed. We suggest a set of best practices for reporting in vitro studies to favor both efficient across‐lab comparisons and translation to in vivo models and human studies.
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Affiliation(s)
- Chris G Dulla
- Department of Neuroscience Tufts University School of Medicine Boston Massachusetts U.S.A
| | - Damir Janigro
- Flocel Inc. and Case Western Reserve University Cleveland Ohio U.S.A
| | - Premysl Jiruska
- Department of Developmental Epileptology Institute of Physiology of the Czech Academy of Sciences Prague Czechia
| | - Joseph V Raimondo
- Division of Cell Biology and Neuroscience Institute Department of Human Biology Faculty of Health Sciences University of Cape Town Cape Town South Africa
| | - Akio Ikeda
- Department of Epilepsy, Movement Disorders and Physiology Kyoto University Graduate School of Medicine Kyoto Japan
| | - Chou-Ching K Lin
- Department of Neurology National Cheng Kung University Hospital College of Medicine National Cheng Kung University Tainan Taiwan
| | - Howard P Goodkin
- The Departments of Neurology and Pediatrics University of Virginia Charlottesville Virginia U.S.A
| | - Aristea S Galanopoulou
- Laboratory of Developmental Epilepsy Saul R. Korey Department of Neurology Isabelle Rapin Division of Child Neurology Dominick P. Purpura Department of Neuroscience Albert Einstein College of Medicine, and Einstein/Montefiore Epilepsy Center Montefiore Medical Center Bronx New York U.S.A
| | | | - Marco de Curtis
- Epilepsy Unit Fondazione IRCCS Istituto Neurologico Carlo Besta Milano Italy
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7
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Abstract
It is widely accepted that synaptic transmissions and gap junctions are the major governing mechanisms for signal traveling in the neural system. Yet, a group of neural waves, either physiological or pathological, share the same speed of ∼0.1 m/s without synaptic transmission or gap junctions, and this speed is not consistent with axonal conduction or ionic diffusion. The only explanation left is an electrical field effect. We tested the hypothesis that endogenous electric fields are sufficient to explain the propagation with in silico and in vitro experiments. Simulation results show that field effects alone can indeed mediate propagation across layers of neurons with speeds of 0.12 ± 0.09 m/s with pathological kinetics, and 0.11 ± 0.03 m/s with physiologic kinetics, both generating weak field amplitudes of ∼2-6 mV/mm. Further, the model predicted that propagation speed values are inversely proportional to the cell-to-cell distances, but do not significantly change with extracellular resistivity, membrane capacitance, or membrane resistance. In vitro recordings in mice hippocampi produced similar speeds (0.10 ± 0.03 m/s) and field amplitudes (2.5-5 mV/mm), and by applying a blocking field, the propagation speed was greatly reduced. Finally, osmolarity experiments confirmed the model's prediction that cell-to-cell distance inversely affects propagation speed. Together, these results show that despite their weak amplitude, electric fields can be solely responsible for spike propagation at ∼0.1 m/s. This phenomenon could be important to explain the slow propagation of epileptic activity and other normal propagations at similar speeds.
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8
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Wong SB, Cheng SJ, Hung WC, Lee WT, Min MY. Rosiglitazone Suppresses In Vitro Seizures in Hippocampal Slice by Inhibiting Presynaptic Glutamate Release in a Model of Temporal Lobe Epilepsy. PLoS One 2015; 10:e0144806. [PMID: 26659605 PMCID: PMC4685987 DOI: 10.1371/journal.pone.0144806] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 11/24/2015] [Indexed: 12/13/2022] Open
Abstract
Peroxisomal proliferator-activated receptor gamma (PPARγ) is a nuclear hormone receptor whose agonist, rosiglitazone has a neuroprotective effect to hippocampal neurons in pilocarpine-induced seizures. Hippocampal slice preparations treated in Mg2+ free medium can induce ictal and interictal-like epileptiform discharges, which is regarded as an in vitro model of N-methyl-D-aspartate (NMDA) receptor-mediated temporal lobe epilepsy (TLE). We applied rosiglitazone in hippocampal slices treated in Mg2+ free medium. The effects of rosiglitazone on hippocampal CA1-Schaffer collateral synaptic transmission were tested. We also examined the neuroprotective effect of rosiglitazone toward NMDA excitotoxicity on cultured hippocampal slices. Application of 10μM rosiglitazone significantly suppressed amplitude and frequency of epileptiform discharges in CA1 neurons. Pretreatment with the PPARγ antagonist GW9662 did not block the effect of rosiglitazone on suppressing discharge frequency, but reverse the effect on suppressing discharge amplitude. Application of rosiglitazone suppressed synaptic transmission in the CA1-Schaffer collateral pathway. By miniature excitatory-potential synaptic current (mEPSC) analysis, rosiglitazone significantly suppressed presynaptic neurotransmitter release. This phenomenon can be reversed by pretreating PPARγ antagonist GW9662. Also, rosiglitazone protected cultured hippocampal slices from NMDA-induced excitotoxicity. The protective effect of 10μM rosiglitazone was partially antagonized by concomitant high dose GW9662 treatment, indicating that this effect is partially mediated by PPARγ receptors. In conclusion, rosiglitazone suppressed NMDA receptor-mediated epileptiform discharges by inhibition of presynaptic neurotransmitter release. Rosiglitazone protected hippocampal slice from NMDA excitotoxicity partially by PPARγ activation. We suggest that rosiglitazone could be a potential agent to treat patients with TLE.
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MESH Headings
- Action Potentials/drug effects
- Anilides/pharmacology
- Animals
- CA1 Region, Hippocampal/drug effects
- CA1 Region, Hippocampal/metabolism
- CA1 Region, Hippocampal/pathology
- Culture Media/chemistry
- Culture Media/pharmacology
- Epilepsy, Temporal Lobe/drug therapy
- Epilepsy, Temporal Lobe/genetics
- Epilepsy, Temporal Lobe/metabolism
- Epilepsy, Temporal Lobe/pathology
- Excitatory Postsynaptic Potentials/drug effects
- Gene Expression Regulation
- Glutamic Acid/metabolism
- Magnesium/pharmacology
- Microtomy
- Models, Biological
- Neurons/drug effects
- Neurons/metabolism
- Neurons/pathology
- Neuroprotective Agents/antagonists & inhibitors
- Neuroprotective Agents/pharmacology
- PPAR gamma/antagonists & inhibitors
- PPAR gamma/genetics
- PPAR gamma/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptors, N-Methyl-D-Aspartate/agonists
- Receptors, N-Methyl-D-Aspartate/genetics
- Receptors, N-Methyl-D-Aspartate/metabolism
- Rosiglitazone
- Seizures/drug therapy
- Seizures/genetics
- Seizures/metabolism
- Seizures/pathology
- Synaptic Transmission/drug effects
- Thiazolidinediones/antagonists & inhibitors
- Thiazolidinediones/pharmacology
- Tissue Culture Techniques
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Affiliation(s)
- Shi-Bing Wong
- Department of Pediatrics, Taipei Tzu Chi General Hospital, Buddhist Tzu Chi Medical Foundation, Taipei, Taiwan
- Institute of Zoology, College of Life Science, National Taiwan University, Taipei, Taiwan
| | - Sin-Jhong Cheng
- Neuroscience Program in Academia Sinica, Taipei, Taiwan
- Institute of Biomedical Sciences; Academia Sinica, Taipei, Taiwan
| | - Wei-Chen Hung
- Department of Pediatrics, Taipei Tzu Chi General Hospital, Buddhist Tzu Chi Medical Foundation, Taipei, Taiwan
| | - Wang-Tso Lee
- Department of Pediatrics, National Taiwan University Hospital, Taipei, Taiwan
- * E-mail: (WTL); (MYM)
| | - Ming-Yuan Min
- Institute of Zoology, College of Life Science, National Taiwan University, Taipei, Taiwan
- * E-mail: (WTL); (MYM)
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9
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In vitro seizure like events and changes in ionic concentration. J Neurosci Methods 2015; 260:33-44. [PMID: 26300181 DOI: 10.1016/j.jneumeth.2015.08.014] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 08/06/2015] [Accepted: 08/12/2015] [Indexed: 11/20/2022]
Abstract
BACKGROUND In vivo, seizure like events are associated with increases in extracellular K(+) concentration, decreases in extracellular Ca(2+) concentration, diphasic changes in extracellular sodium, chloride, and proton concentration, as well as changes of extracellular space size. These changes point to mechanisms underlying the induction, spread and termination of seizure like events. METHODS We investigated the potential role of alterations of the ionic environment on the induction of seizure like events-considering a review of the literature and own experimental work in animal and human slices. RESULTS Increasing extracellular K(+) concentration, lowering extracellular Mg(2+) concentration, or lowering extracellular Ca(2+) concentration can induce seizure like events. In human tissue from epileptic patients, elevation of K(+) concentration induces seizure like events in the dentate gyrus and subiculum. A combination of elevated K(+) concentration and 4-AP or bicuculline can induce seizure like events in neocortical tissue. CONCLUSIONS These protocols provide insight into the mechanisms involved in seizure initiation, spread and termination. Moreover, pharmacological studies as well as studies on mechanisms underlying pharmacoresistance are feasible.
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10
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El Houssaini K, Ivanov AI, Bernard C, Jirsa VK. Seizures, refractory status epilepticus, and depolarization block as endogenous brain activities. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 91:010701. [PMID: 25679555 DOI: 10.1103/physreve.91.010701] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Indexed: 06/04/2023]
Abstract
Epilepsy, refractory status epilepticus, and depolarization block are pathological brain activities whose mechanisms are poorly understood. Using a generic mathematical model of seizure activity, we show that these activities coexist under certain conditions spanning the range of possible brain activities. We perform a detailed bifurcation analysis and predict strategies to escape from some of the pathological states. Experimental results using rodent data provide support of the model, highlighting the concept that these pathological activities belong to the endogenous repertoire of brain activities.
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Affiliation(s)
- Kenza El Houssaini
- Aix Marseille Université, Inserm, INS UMR_S 1106, 13005, Marseille, France
| | - Anton I Ivanov
- Aix Marseille Université, Inserm, INS UMR_S 1106, 13005, Marseille, France
| | - Christophe Bernard
- Aix Marseille Université, Inserm, INS UMR_S 1106, 13005, Marseille, France
| | - Viktor K Jirsa
- Aix Marseille Université, Inserm, INS UMR_S 1106, 13005, Marseille, France
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Metabolic responses differentiate between interictal, ictal and persistent epileptiform activity in intact, immature hippocampus in vitro. Neurobiol Dis 2014; 75:1-14. [PMID: 25533681 DOI: 10.1016/j.nbd.2014.12.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2014] [Revised: 12/06/2014] [Accepted: 12/11/2014] [Indexed: 01/09/2023] Open
Abstract
Interictal spikes, ictal responses, and status epilepticus are characteristic of abnormal neuronal activity in epilepsy. Since these events may involve different energy requirements, we evaluated metabolic function (assessed by simultaneous NADH and FAD+ imaging and tissue O2 recordings) in the immature, intact mouse hippocampus (P5-P7, in vitro) during spontaneous interictal spikes and ictal-like events (ILEs), induced by increased neuronal network excitability with either low Mg2+ media or decreased inhibition with bicuculline. In low Mg2+ medium NADH fluorescence showed a small decrease both during the interictal build-up leading to an ictal event and before ILE occurrences, but a large positive response during and after ILEs (up to 10% net change). Tissue O2 recordings (pO2) showed an oxygen dip (indicating oxygen consumption) coincident with each ILE at P5 and P7, closely matching an NADH fluorescence increase, indicating a large surge in oxidative metabolism. The ILE O2 dip was significantly larger at P7 as compared to P5 suggesting a higher metabolic response at P7. After several ILEs at P7, continuous, low voltage activity (late recurrent discharges: LRDs) occurred. During LRDs, whilst the epileptiform activity was relatively small (low voltage synchronous activity) oxygen levels remained low and NADH fluorescence elevated, indicating persistent oxygen utilization and maintained high metabolic demand. In bicuculline, NADH fluorescence levels decreased prior to the onset of epileptiform activity, followed by a slow positive phase, which persisted during interictal responses. Metabolic responses can thus differentiate between interictal, ictal-like and persistent epileptiform activity resembling status epilepticus, and confirm that spreading depression did not occur. These results demonstrate clear translational value to the understanding of metabolic requirements during epileptic conditions.
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12
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Propagation of epileptiform activity can be independent of synaptic transmission, gap junctions, or diffusion and is consistent with electrical field transmission. J Neurosci 2014; 34:1409-19. [PMID: 24453330 DOI: 10.1523/jneurosci.3877-13.2014] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The propagation of activity in neural tissue is generally associated with synaptic transmission, but epileptiform activity in the hippocampus can propagate with or without synaptic transmission at a speed of ∼0.1 m/s. This suggests an underlying common nonsynaptic mechanism for propagation. To study this mechanism, we developed a novel unfolded hippocampus preparation, from CD1 mice of either sex, which preserves the transverse and longitudinal connections and recorded activity with a penetrating microelectrode array. Experiments using synaptic transmission and gap junction blockers indicated that longitudinal propagation is independent of chemical or electrical synaptic transmission. Propagation speeds of 0.1 m/s are not compatible with ionic diffusion or pure axonal conduction. The only other means of communication between neurons is through electric fields. Computer simulations revealed that activity can indeed propagate from cell to cell solely through field effects. These results point to an unexpected propagation mechanism for neural activity in the hippocampus involving endogenous field effect transmission.
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13
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Sharopov S, Moser J, Chen R, Kolbaev SN, Bernedo VE, Werhahn KJ, Luhmann HJ, Kilb W. Dopaminergic modulation of low-Mg2+-induced epileptiform activity in the intact hippocampus of the newborn mouse in vitro. J Neurosci Res 2012; 90:2020-33. [DOI: 10.1002/jnr.23084] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Revised: 04/11/2012] [Accepted: 04/13/2012] [Indexed: 11/12/2022]
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14
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Quilichini PP, Le Van Quyen M, Ivanov A, Turner DA, Carabalona A, Gozlan H, Esclapez M, Bernard C. Hub GABA neurons mediate gamma-frequency oscillations at ictal-like event onset in the immature hippocampus. Neuron 2012; 74:57-64. [PMID: 22500630 DOI: 10.1016/j.neuron.2012.01.026] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/18/2012] [Indexed: 10/28/2022]
Abstract
Gamma-frequency oscillations (GFOs, >40 Hz) are a general network signature at seizure onset at all stages of development, with possible deleterious consequences in the immature brain. At early developmental stages, the simultaneous occurrence of GFOs in different brain regions suggests the existence of a long-ranging synchronizing mechanism at seizure onset. Here, we show that hippocamposeptal (HS) neurons, which are GABA long-range projection neurons, are mandatory to drive the firing of hippocampal interneurons in a high-frequency regime at the onset of epileptiform discharges in the intact, immature septohippocampal formation. The synchronized firing of interneurons in turn produces GFOs, which are abolished after the elimination of a small number of HS neurons. Because they provide the necessary fast conduit for pacing large neuronal populations and display intra- and extrahippocampal long-range projections, HS neurons appear to belong to the class of hub cells that play a crucial role in the synchronization of developing networks.
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Affiliation(s)
- Pascale P Quilichini
- Institut de Neurosciences des Systèmes, INSERM UMR1106, Faculté de Médecine La Timone, 27 Boulevard Jean Moulin, 13005 Marseille, France
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15
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Yuen AW, Sander JW. Can magnesium supplementation reduce seizures in people with epilepsy? A hypothesis. Epilepsy Res 2012; 100:152-6. [DOI: 10.1016/j.eplepsyres.2012.02.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2011] [Revised: 01/31/2012] [Accepted: 02/05/2012] [Indexed: 12/15/2022]
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16
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Abstract
Understanding how epileptic seizures are initiated and propagated across large brain networks is difficult, but an even greater mystery is what makes them stop. Failure of spontaneous seizure termination leads to status epilepticus-a state of uninterrupted seizure activity that can cause death or permanent brain damage. Global factors, like changes in neuromodulators and ion concentrations, are likely to play major roles in spontaneous seizure cessation, but individual neurons also have intrinsic active ion currents that may contribute. The recently discovered gene Slack encodes a sodium-activated potassium channel that mediates a major proportion of the outward current in many neurons. Although given little attention, the current flowing through this channel may have properties consistent with a role in seizure termination.
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Affiliation(s)
- Kajsa M Igelström
- Department of Physiology, Otago School of Medical Sciences, University of Otago, Dunedin, New Zealand.
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17
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Intact In Vitro Preparations of the Neonatal Rodent Cortex: Analysis of Cellular Properties and Network Activity. ISOLATED CENTRAL NERVOUS SYSTEM CIRCUITS 2012. [DOI: 10.1007/978-1-62703-020-5_10] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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18
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Progressive NKCC1-dependent neuronal chloride accumulation during neonatal seizures. J Neurosci 2010; 30:11745-61. [PMID: 20810895 DOI: 10.1523/jneurosci.1769-10.2010] [Citation(s) in RCA: 141] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Seizures induce excitatory shifts in the reversal potential for GABA(A)-receptor-mediated responses, which may contribute to the intractability of electro-encephalographic seizures and preclude the efficacy of widely used GABAergic anticonvulsants such as phenobarbital. We now report that, in intact hippocampi prepared from neonatal rats and transgenic mice expressing Clomeleon, recurrent seizures progressively increase the intracellular chloride concentration ([Cl(-)](i)) assayed by Clomeleon imaging and invert the net effect of GABA(A) receptor activation from inhibition to excitation assayed by the frequency of action potentials and intracellular Ca(2+) transients. These changes correlate with increasing frequency of seizure-like events and reduction in phenobarbital efficacy. The Na(+)-K(+)-2Cl(-) (NKCC1) cotransporter blocker bumetanide inhibited seizure-induced neuronal Cl(-) accumulation and the consequent facilitation of recurrent seizures. Our results demonstrate a novel mechanism by which seizure activity leads to [Cl(-)](i) accumulation, thereby increasing the probability of subsequent seizures. This provides a potential mechanism for the early crescendo phase of neonatal seizures.
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Wahab A, Heinemann U, Albus K. Effects of γ-aminobutyric acid (GABA) agonists and a GABA uptake inhibitor on pharmacoresistant seizure like events in organotypic hippocampal slice cultures. Epilepsy Res 2009; 86:113-23. [DOI: 10.1016/j.eplepsyres.2009.05.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2009] [Revised: 05/09/2009] [Accepted: 05/11/2009] [Indexed: 10/20/2022]
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20
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de Curtis M, Gnatkovsky V. Reevaluating the mechanisms of focal ictogenesis: The role of low-voltage fast activity. Epilepsia 2009; 50:2514-25. [PMID: 19674056 DOI: 10.1111/j.1528-1167.2009.02249.x] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The mechanisms that control the transition into a focal seizure are still uncertain. The introduction of presurgical intracranial recordings to localize the epileptogenic zone in patients with drug-resistant focal epilepsies opened a new window to the interpretation of seizure generation (ictogenesis). One of the most frequent focal patterns observed with intracranial electrodes at seizure onset is characterized by low-voltage fast activity in the beta-gamma range that may or may not be preceded by changes of ongoing interictal activities. In the present commentary, the mechanisms of generation of focal seizures are reconsidered, focusing on low-voltage fast activity patterns. Experimental findings on models of temporal lobe seizures support the view that the low-voltage fast activity observed at seizure onset is associated with reinforcement and synchronization of inhibitory networks. A minor role for the initiation of the ictal pattern is played by principal neurons that are progressively recruited with a delay, when inhibition declines and synchronous high-voltage discharges ensue. The transition from inhibition into excitatory recruitment is probably mediated by local increase in potassium concentration associated with synchronized interneuronal firing. These findings challenge the classical theory that proposes an increment of excitation and/or a reduction of inhibition as a cause for the transition to seizure in focal epilepsies. A new definition of ictogenesis mechanisms, as herewith hypothesized, might possibly help to develop new therapeutic strategies for focal epilepsies.
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Affiliation(s)
- Marco de Curtis
- Unit of Experimental Neurophysiology and Epileptology, Fondazione Istituto Neurologico Carlo Besta, Milano, Italy.
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21
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Shahar E, Derchansky M, Carlen P. The role of altered tissue osmolality on the characteristics and propagation of seizure activity in the intact isolated mouse hippocampus. Clin Neurophysiol 2009; 120:673-8. [DOI: 10.1016/j.clinph.2009.01.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2008] [Revised: 12/28/2008] [Accepted: 01/19/2009] [Indexed: 10/21/2022]
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22
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Dzhala VI, Brumback AC, Staley KJ. Bumetanide enhances phenobarbital efficacy in a neonatal seizure model. Ann Neurol 2008; 63:222-35. [DOI: 10.1002/ana.21229] [Citation(s) in RCA: 215] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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23
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Davies ML, Kirov SA, Andrew RD. Whole isolated neocortical and hippocampal preparations and their use in imaging studies. J Neurosci Methods 2007; 166:203-16. [PMID: 17765319 PMCID: PMC2100436 DOI: 10.1016/j.jneumeth.2007.07.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2007] [Revised: 07/10/2007] [Accepted: 07/11/2007] [Indexed: 11/19/2022]
Abstract
This study shows that two whole isolated preparations from the young mouse, the neocortical 'slab' and the hippocampal formation, are useful for imaging studies requiring both global monitoring using light transmittance (LT) imaging and high resolution cellular monitoring using 2-photon laser scanning microscopy (2PLSM). These preparations share advantages with brain slices such as maintaining intrinsic neuronal properties and avoiding cardiac or respiratory movement. Important additional advantages include the maintenance of all local input and output pathways, the absence of surfaces injured by slicing and the preservation of three-dimensional tissue structure. Using evoked extracellular field recording, we demonstrate long-term (hours) viability of both whole preparations. We then show that propagating cortical events such as anoxic depolarization (AD) and spreading depression (SD) can be imaged in both preparations, yielding results comparable to those in brain slices but retaining the tissue's three-dimensional structure. Using transgenic mice expressing green fluorescent protein (GFP) in pyramidal and granule cell neurons, 2PLSM confirms that these preparations are free of the surface damage observed in sliced brain tissue. Moreover the neurons undergo swelling with accompanying dendritic beading following AD induced by simulated ischemia, similar to cortical damage described in vivo.
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Affiliation(s)
- Melissa L. Davies
- Department of Anatomy & Cell Biology and The Centre for Neuroscience Studies Queen’s University, Kingston, ON
| | - Sergei A. Kirov
- Department of Neurosurgery Medical College of Georgia, Augusta, GA
| | - R. David Andrew
- Department of Anatomy & Cell Biology and The Centre for Neuroscience Studies Queen’s University, Kingston, ON
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24
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Ben-Ari Y, Gaiarsa JL, Tyzio R, Khazipov R. GABA: a pioneer transmitter that excites immature neurons and generates primitive oscillations. Physiol Rev 2007; 87:1215-84. [PMID: 17928584 DOI: 10.1152/physrev.00017.2006] [Citation(s) in RCA: 892] [Impact Index Per Article: 52.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Developing networks follow common rules to shift from silent cells to coactive networks that operate via thousands of synapses. This review deals with some of these rules and in particular those concerning the crucial role of the neurotransmitter gamma-aminobuytric acid (GABA), which operates primarily via chloride-permeable GABA(A) receptor channels. In all developing animal species and brain structures investigated, neurons have a higher intracellular chloride concentration at an early stage leading to an efflux of chloride and excitatory actions of GABA in immature neurons. This triggers sodium spikes, activates voltage-gated calcium channels, and acts in synergy with NMDA channels by removing the voltage-dependent magnesium block. GABA signaling is also established before glutamatergic transmission, suggesting that GABA is the principal excitatory transmitter during early development. In fact, even before synapse formation, GABA signaling can modulate the cell cycle and migration. The consequence of these rules is that developing networks generate primitive patterns of network activity, notably the giant depolarizing potentials (GDPs), largely through the excitatory actions of GABA and its synergistic interactions with glutamate signaling. These early types of network activity are likely required for neurons to fire together and thus to "wire together" so that functional units within cortical networks are formed. In addition, depolarizing GABA has a strong impact on synaptic plasticity and pathological insults, notably seizures of the immature brain. In conclusion, it is suggested that an evolutionary preserved role for excitatory GABA in immature cells provides an important mechanism in the formation of synapses and activity in neuronal networks.
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Affiliation(s)
- Yehezkel Ben-Ari
- Insititut de Neurobiologie de la Méditerranée, Institut National de la Santé et de la Recherche Médicale U. 29, Marseille, France.
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25
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Derchansky M, Jahromi SS, Mamani M, Shin DS, Sik A, Carlen PL. Transition to seizures in the isolated immature mouse hippocampus: a switch from dominant phasic inhibition to dominant phasic excitation. J Physiol 2007; 586:477-94. [PMID: 17991696 DOI: 10.1113/jphysiol.2007.143065] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The neural dynamics and mechanisms responsible for the transition from the interictal to the ictal state (seizures) are unresolved questions in epilepsy. It has been suggested that a shift from inhibitory to excitatory GABAergic drive can promote seizure generation. In this study, we utilized an experimental model of temporal lobe epilepsy which produces recurrent seizure-like events in the isolated immature mouse hippocampus (P8-16), perfused with low magnesium ACSF, to investigate the cellular dynamics of seizure transition. Whole-cell and perforated patch recordings from CA1 pyramidal cells and from fast- and non-fast-spiking interneurons in the CA1 stratum oriens hippocampal region showed a change in intracellular signal integration during the transition period, starting with dominant phasic inhibitory synaptic input, followed by dominant phasic excitation prior to a seizure. Efflux of bicarbonate ions through the GABA A receptor did not fully account for this excitation and GABAergic excitation via reversed IPSPs was also excluded as the prime mechanism generating the dominant excitation, since somatic and dendritic GABA A responses to externally applied muscimol remained hyperpolarizing throughout the transition period. In addition, abolishing EPSPs in a single neuron by intracellularly injected QX222, revealed that inhibitory synaptic drive was maintained throughout the entire transition period. We suggest that rather than a major shift from inhibitory to excitatory GABAergic drive prior to seizure onset, there is a change in the interaction between afferent synaptic inhibition, and afferent and intrinsic excitatory processes in pyramidal neurons and interneurons, with maintained inhibition and increasing, entrained 'overpowering' excitation during the transition to seizure.
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Affiliation(s)
- M Derchansky
- Division of Cellular and Molecular Biology, Toronto Western Hospital, 399 Bathurst St, 12-413, Toronto, Ontario, Canada M5T2S8
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26
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Kilb W, Dierkes PW, Syková E, Vargová L, Luhmann HJ. Hypoosmolar conditions reduce extracellular volume fraction and enhance epileptiform activity in the CA3 region of the immature rat hippocampus. J Neurosci Res 2006; 84:119-29. [PMID: 16634058 DOI: 10.1002/jnr.20871] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The osmolarity of the extracellular space (ECS) compartment is an important factor determining the excitability of neuronal tissue. In the adult hippocampus an important role of osmolarity and ECS diffusion parameters on the susceptibility to epileptic events is well established, but the influence of hypo- and hyperosmolar conditions on the immature hippocampus remains elusive. To investigate the influence of osmolarity on epileptiform activity, extracellular field potentials were recorded in the CA3 region of hippocampal slices of immature (postnatal days 4-7) Wistar rats. The ECS diffusion parameters were determined by the real-time tetramethylammonium (TMA+) iontophoretic method with ion-selective microelectrodes in immature hippocampal slices and showed a lack of diffusion anisotropy; a tortuosity of about 1.39; and a volume fraction, alpha, of 0.41 +/- 0.01 (n = 10 slices). A reduction in osmolarity of -90 mOsm induced a decrease in alpha to 0.17 +/- 0.02 (n = 4 slices). The frequency of epileptiform activity elicited in 10-50 microM 4-AP-containing low-Mg2+ solution was increased under -90 mOsm and -40 mOsm hypoosmolar conditions by 39.9% +/- 8.1% (n = 16) and 24.1% +/- 4.8% (n = 10), respectively, whereas hyperosmolar solutions decreased the frequency. A -90-mOsm reduction in the osmolarity of low-Mg2+ solution induced epileptiform activity in nine of 19 slices. In summary, these results demonstrate that hypoosmolar conditions increased excitability and susceptibility to epileptiform activity in immature hippocampal slices, suggesting a functional role of the larger alpha in suppression of seizures.
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Affiliation(s)
- Werner Kilb
- Institute of Physiology and Pathophysiology, Johannes Gutenberg-University, Mainz, Germany.
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27
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Le Van Quyen M, Khalilov I, Ben-Ari Y. The dark side of high-frequency oscillations in the developing brain. Trends Neurosci 2006; 29:419-427. [PMID: 16793147 DOI: 10.1016/j.tins.2006.06.001] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2006] [Revised: 04/19/2006] [Accepted: 06/02/2006] [Indexed: 11/28/2022]
Abstract
Adult brain networks generate a wide range of oscillations. Some of these are behaviourally relevant, whereas others occur during seizures and other pathological conditions. This raises the question of how physiological oscillations differ from pathogenic ones. In this review, this issue is discussed from a developmental standpoint. Indeed, both epileptic and physiological high-frequency oscillations (HFOs) appear progressively during maturation, and it is therefore possible to determine how this program corresponds to maturation of the neuronal populations that generate these oscillations. We review here important differences in the development of neuronal populations that might contribute to their different oscillatory properties. In particular, at an early stage, the density of glutamatergic synapses is too low for physiological HFOs but an additional drive can be provided by excitatory GABA, triggering epileptic HFOs and the cascades involved in long-lasting epileptogenic transformations. This review is part of the INMED/TINS special issue "Nature and nurture in brain development and neurological disorders", based on presentations at the annual INMED/TINS symposium (http://inmednet.com/).
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Affiliation(s)
- Michel Le Van Quyen
- LENA-CNRS UPR640, Université Pierre et Marie Curie, Hôpital de la Salpêtrière, 47 Bd de l'Hôpital, 75651 Paris Cedex 13, France
| | - Ilgam Khalilov
- INMED-INSERM U29, 163 Route de Luminy, 13273 Marseille Cedex 09, France
| | - Yehezkel Ben-Ari
- INMED-INSERM U29, 163 Route de Luminy, 13273 Marseille Cedex 09, France.
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28
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Derchansky M, Rokni D, Rick JT, Wennberg R, Bardakjian BL, Zhang L, Yarom Y, Carlen PL. Bidirectional multisite seizure propagation in the intact isolated hippocampus: the multifocality of the seizure "focus". Neurobiol Dis 2006; 23:312-28. [PMID: 16815026 DOI: 10.1016/j.nbd.2006.03.014] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Revised: 03/09/2006] [Accepted: 03/17/2006] [Indexed: 11/29/2022] Open
Abstract
Localizing the seizure focus is difficult and frequently, multiple sites are found. This reflects our poor understanding of the fundamental mechanisms of seizure generation and propagation. We used multisite electrophysiological recordings in two seizure models and voltage-sensitive dye imaging, to spatiotemporally characterize the initiation and propagation of seizures in an intact epileptogenic brain region, the isolated hippocampus. In low-magnesium perfusate, seizures always originated in the temporal region, and propagated along the septotemporal axis to the septal region. After the seizure spread across the hippocampus, the bursts within a seizure became bidirectional, with different propagation patterns at different frequencies. When the intact hippocampus was separated along the septotemporal axis, independent bidirectional activity was observed in the two halves, and region-specific cuts to the tissue reveal that the CA3 region is critical for seizure generation and propagation. In a second seizure model, using focal tetanic stimulation of the septal and temporal CA3 region, seizures always originated at the stimulated site with bidirectionality later developing at different frequencies, as noted in the low magnesium model, behavior compatible with coupled neuronal network oscillators. These data provide novel insights into the dynamic multifocality of seizure onset and propagation, revealing that the current concept of a single seizure "focus" is complex.
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Affiliation(s)
- M Derchansky
- Division of Cellular and Molecular Biology, Toronto Western Research Institute, Canada
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29
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Fujiwara-Tsukamoto Y, Isomura Y, Takada M. Comparable GABAergic Mechanisms of Hippocampal Seizurelike Activity in Posttetanic and Low-Mg2+ Conditions. J Neurophysiol 2006; 95:2013-9. [PMID: 16339009 DOI: 10.1152/jn.00238.2005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
It is known that GABA is a major inhibitory neurotransmitter in mature mammalian brains, but the effect of this substance is sometimes converted into depolarizing or even excitatory when the postsynaptic Cl– concentration becomes high. Recently we have shown that seizurelike afterdischarge induced by tetanic stimulation in normal extracellular fluid (posttetanic afterdischarge) is mediated through GABAergic excitation in mature hippocampal CA1 pyramidal cells. In this study, we examined the possible contribution of similar depolarizing/excitatory GABAergic input to the CA1 pyramidal cells to the seizurelike afterdischarge induced in a low extracellular Mg2+ condition, another experimental model of epileptic seizure activity (low-Mg2+ afterdischarge). Perfusion of the GABAA antagonist bicuculline abolished the low-Mg2+ afterdischarge, but not the interictal-like activity, in most cases. Each oscillatory response during the low-Mg2+ afterdischarge was dependent on Cl– conductance and contained an F–-insensitive depolarizing component in the pyramidal cells, thus indicating that the afterdischarge response may be mediated through both GABAergic and nonGABAergic transmissions. In addition, local GABA application to the recorded cells revealed that GABA responses were indeed depolarizing during the low-Mg2+ afterdischarge. Furthermore, the GABAergic interneurons located in the strata pyramidale and oriens fired in oscillatory cycles more actively than those in other layers of the CA1 region. These results suggest that the depolarizing GABAergic input may facilitate oscillatory synchronization among the hippocampal CA1 pyramidal cells during the low-Mg2+ afterdischarge in a manner similar to the expression of the posttetanic afterdischarge.
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Affiliation(s)
- Yoko Fujiwara-Tsukamoto
- Dept. of System Neuroscience, Tokyo Metropolitan Inst. for Neuroscience, 2-6 Musashidai, Fuchu, Tokyo 183-8526, Japan.
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30
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Moser J, Kilb W, Werhahn KJ, Luhmann HJ. Early developmental alterations of low-Mg2+ -induced epileptiform activity in the intact corticohippocampal formation of the newborn mouse in vitro. Brain Res 2006; 1077:170-7. [PMID: 16510134 DOI: 10.1016/j.brainres.2006.01.024] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2005] [Revised: 01/02/2006] [Accepted: 01/06/2006] [Indexed: 10/25/2022]
Abstract
The generation, propagation and pharmacological properties of low-Mg2+ -induced epileptiform activity were examined in the intact corticohippocampal formation (CHF) of the newborn (P0-4) mouse in vitro. Multi-site field potential recordings in dentate gyrus (DG), CA3, CA1, entorhinal cortex (EC) and temporal cortex (TC) revealed in 0.2 mM Mg2+ -containing ACSF a stable pattern of spontaneous epileptiform activity consisting of recurrent ictal-like events (ILEs) and interictal events (IEs). Although this activity could be consistently observed as early as P0, ILEs were smaller in amplitude, less frequent and showed a slower onset in P0-2 as compared to P3-4 animals. In all age groups, epileptiform events were largest in CA3 and smallest in EC and TC. A specific pacemaker region could not be identified since ILEs appeared simultaneously at all recording sites. Reducing the extracellular Mg2+ concentration to 0.1 mM or nominally zero caused an increase in ILE frequency. Pharmacological studies in the P3-4 age group with 0.2 mM Mg2+ revealed a complete blockade of the ILEs by an NMDA receptor antagonist and a pronounced suppression of epileptiform activity by an AMPA/kainate antagonist. Application of a GABA-A receptor antagonist induced repetitive bursts of interictal discharges, which persisted for at least 1.5 h after washout of the antagonist. Our data demonstrate that the intact CHF in vitro preparation of the newborn mouse offers a most valuable model to study epileptiform activity in the immature limbic system.
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Affiliation(s)
- Jochen Moser
- Institute of Physiology and Pathophysiology, Johannes-Gutenberg University, Duesbergweg 6, D-55128 Mainz, Germany
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31
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Khalilov I, Le Van Quyen M, Gozlan H, Ben-Ari Y. Epileptogenic Actions of GABA and Fast Oscillations in the Developing Hippocampus. Neuron 2005; 48:787-96. [PMID: 16337916 DOI: 10.1016/j.neuron.2005.09.026] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2005] [Revised: 07/28/2005] [Accepted: 09/22/2005] [Indexed: 11/28/2022]
Abstract
GABA excites immature neurons and inhibits adult ones, but whether this contributes to seizures in the developing brain is not known. We now report that in the developing, but not the adult, hippocampus, seizures beget seizures only if GABAergic synapses are functional. In the immature hippocampus, seizures generated with functional GABAergic synapses include fast oscillations that are required to transform a naive network to an epileptic one: blocking GABA receptors prevents the long-lasting sequels of seizures. In contrast, in adult neurons, full blockade of GABA(A) receptors generates epileptogenic high-frequency seizures. Therefore, purely glutamatergic seizures are not epileptogenic in the developing hippocampus. We suggest that the density of glutamatergic synapses is not sufficient for epileptogenesis in immature neurons; excitatory GABAergic synapses are required for that purpose. We suggest that the synergistic actions of GABA and NMDA receptors trigger the cascades involved in epileptogenesis in the developing hippocampus.
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Affiliation(s)
- Ilgam Khalilov
- INMED-INSERM, U 29 Marseille, 163, route de Luminy, 13273 Marseille Cedex 09, France
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32
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Isaev D, Isaeva E, Khazipov R, Holmes GL. Anticonvulsant action of GABA in the high potassium-low magnesium model of ictogenesis in the neonatal rat hippocampus in vivo and in vitro. J Neurophysiol 2005; 94:2987-92. [PMID: 16000527 DOI: 10.1152/jn.00138.2005] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous developmental studies in vitro suggested that the inhibitory neurotransmitter GABA exerts depolarizing and excitatory actions on the immature neurons and that depolarizing GABA is causally linked to ictal activity during the first weeks of postnatal life. However, remarkably little is known on the role of GABA in the generation of neonatal seizures in vivo. Here, using extracellular recordings from CA3 hippocampus, we studied the effects of GABA(A)-acting drugs on electrographic seizures induced by local intrahippocampal injection of the epileptogenic agents (high K(+)/low Mg(2+)) in the nonanesthetized rats in vivo and in the hippocampal slices in vitro during the second postnatal week (postnatal days P8-12). We found that in vivo, the induction of ictal-like events was facilitated by co-infusion of high-K(+)/low Mg(2+) together with the GABA(A) antagonist bicuculline or gabazine. Moreover, the infusion of bicuculline alone caused ictal-like activity in approximately 30% of cases. Co-infusion of the GABA(A) receptor agonist isoguvacine or the GABA(A)-positive allosteric modulator diazepam completely prevented high-K(+)/low Mg(2+)-induced seizures. In in vitro studies using hippocampal slices, we also found that high-K(+)/low Mg(2+) produced ictal activity that was exacerbated by bicuculline and gabazine and reduced by isoguvacine. Thus in the model of high-K(+)/low Mg(2+)-induced seizures both in in vivo and in vitro conditions, GABA, acting via GABA(A) receptors, has an anticonvulsant effect during the critical developmental period of enhanced excitability.
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Affiliation(s)
- Dmytro Isaev
- Section of Neurology, Dartmouth Medical School, Dartmouth-Hitchcock Medical School, Lebanon, NH 03756, USA
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33
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Abdelmalik PA, Burnham WM, Carlen PL. Increased seizure susceptibility of the hippocampus compared with the neocortex of the immature mouse brain in vitro. Epilepsia 2005; 46:356-66. [PMID: 15730532 DOI: 10.1111/j.0013-9580.2005.34204.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE The temporal lobe seems particularly susceptible to seizure activity. Mesial temporal lobe structures, including the hippocampus, have the lowest seizure thresholds in the brain. Conversely, thresholds in the frontal neocortex are significantly higher. The development of intact, isolated preparations of hippocampus and neocortex in vitro allows for study into mechanisms governing seizure threshold. METHODS Epileptiform discharges in isolated mouse neocortical blocks were compared with the contralateral intact hippocampus, isolated from the same brain, by using the low-Mg2+, 4 aminopyridine (4-AP), and low-Ca2+ in vitro seizure models. The pharmacology of low Mg(2+)-induced ictal-like events (ILEs) generated in the hippocampus and neocortex was then compared by using glutamatergic antagonists DL-2-amino-5-phosphonovaleric acid (APV) and 6-cyano-7-nitro-quinoxaline-2,3-dione (CNQX), and the Ca2+ channel antagonist, nifedipine. RESULTS Neocortical blocks generated both recurrent, spontaneous ILEs and interictal-like events under low-Mg2+ artificial CSF (aCSF) perfusion, distinct from those generated in the hippocampus. ILEs from the hippocampus displayed lower thresholds and longer durations as compared with isolated neocortical blocks. Similar results were obtained during 4-AP perfusion. Perfusion with low-Ca2+ ACSF did not produce stereotypical ILEs in the neocortical block, producing instead recurrent, slow depolarizations. Both ILEs and recurrent, slow depolarizations were produced in the hippocampus. Application of APV and nifedipine exacerbated low Mg(2+)-induced ILEs in the hippocampus but not the neocortex, indicating a distinct pharmacology for partial seizures of different brain regions. CONCLUSIONS The developing mouse hippocampus demonstrates increased ictogenesis compared with the developing neocortex in vitro, consistent with clinical observations and in vivo experimental models.
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Affiliation(s)
- Peter A Abdelmalik
- Department of Pharmacology, University of Toronto, Toronto, Ontario, Canada
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Derchansky M, Shahar E, Wennberg RA, Samoilova M, Jahromi SS, Abdelmalik PA, Zhang L, Carlen PL. Model of frequent, recurrent, and spontaneous seizures in the intact mouse hippocampus. Hippocampus 2005; 14:935-47. [PMID: 15390177 DOI: 10.1002/hipo.20007] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
This study presents a model of chronic, recurrent, spontaneous seizures in the intact isolated hippocampal preparation from mice aged P8-P25. Field activity from the CA1 pyramidal cell layer was recorded and recurrent, spontaneous seizure-like events (SLEs) were observed in the presence of low Mg2+ (0.25 mM) artificial cerebrospinal fluid (ACSF). Hippocampi also showed interictal epileptiform discharges (IEDs) of 0.9-4.2 Hz occurring between seizures. No age-specific differences were found in SLE occurrence (2 SLEs per 10 min, on average), duration, and corresponding frequencies. After long exposure to low Mg2+ ACSF (>3 h), SLEs were completely reversible within minutes with the application of normal (2 mM Mg2+) ACSF. The AMPA antagonist, CNQX, blocked all epileptiform activity, whereas the NMDA antagonist, APV, did not. The gamma-aminobutyric acid (GABA)A antagonist, bicuculline, attenuated and fragmented SLEs, implicating interneurons in SLE generation. The L-type Ca2+ blocker, nifedipine, enhanced epileptiform activity. Analysis of dual site recordings along the septotemporal hippocampus demonstrated that epileptiform activity began first in the temporal pole of the hippocampus, as illustrated by disconnection experiments. Once an SLE had been established, however, the septal hippocampus was sometimes seen to lead the epileptiform activity. The whole hippocampus with intact local circuitry, treated with low Mg2+, provides a realistic model of recurrent spontaneous seizures, which may be used, in normal and genetically modified mice, to study the dynamics of seizures and seizure evolution, as well as the mechanisms of action of anti-epileptic drugs and other therapeutic modalities.
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Affiliation(s)
- M Derchansky
- Division of Cellular and Molecular Biology, Toronto Western Research Institute, Ontario, Toronto, Canada
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Whalley BJ, Postlethwaite M, Constanti A. Further characterization of muscarinic agonist-induced epileptiform bursting activity in immature rat piriform cortex, in vitro. Neuroscience 2005; 134:549-66. [PMID: 15961237 DOI: 10.1016/j.neuroscience.2005.04.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2005] [Revised: 04/05/2005] [Accepted: 04/07/2005] [Indexed: 11/16/2022]
Abstract
The characteristics of muscarinic acetylcholine receptor agonist-induced epileptiform bursting seen in immature rat piriform cortex slices in vitro were further investigated using intracellular recording, with particular focus on its postnatal age-dependence (P+14-P+30), pharmacology, site(s) of origin and the likely contribution of the muscarinic acetylcholine receptor agonist-induced post-stimulus slow afterdepolarization and gap junction functionality toward its generation. The muscarinic agonist, oxotremorine-M (10 microM), induced rhythmic bursting only in immature piriform cortex slices; however, paroxysmal depolarizing shift amplitude, burst duration and burst incidence were inversely related to postnatal age. No significant age-dependent changes in neuronal membrane properties or postsynaptic muscarinic responsiveness accounted for this decline. Burst incidence was higher when recorded in anterior and posterior regions of the immature piriform cortex. In adult and immature neurones, oxotremorine-M effects were abolished by M1-, but not M2-muscarinic acetylcholine receptor-selective antagonists. Rostrocaudal lesions, between piriform cortex layers I and II, or layer III and endopiriform nucleus in adult or immature slices did not influence oxotremorine-M effects; however, the slow afterdepolarization in adult (but not immature) lesioned slices was abolished. Gap junction blockers (carbenoxolone or octanol) disrupted muscarinic bursting and diminished the slow afterdepolarization in immature slices, suggesting that gap junction connectivity was important for bursting. Our data show that neural networks within layers II-III function as primary oscillatory circuits for burst initiation in immature rat piriform cortex during persistent muscarinic receptor activation. Furthermore, we propose that muscarinic slow afterdepolarization induction and gap junction communication could contribute towards the increased epileptiform susceptibility of this brain area.
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Affiliation(s)
- B J Whalley
- Department of Pharmacology, The School of Pharmacy, 29/39 Brunswick Square, London WC1N 1AX, UK.
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Etherington LAV, Frenguelli BG. Endogenous adenosine modulates epileptiform activity in rat hippocampus in a receptor subtype-dependent manner. Eur J Neurosci 2004; 19:2539-50. [PMID: 15128407 DOI: 10.1111/j.0953-816x.2004.03355.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The purine nucleoside adenosine is released during seizure activity and exerts an anticonvulsant influence through inhibition of glutamate release and hyperpolarization of neurons via adenosine A(1) receptors. However, activation of adenosine A(2A) and A(3) receptors may counteract the inhibitory effects of A(1) receptors. We have therefore examined the extent to which endogenous adenosine released during seizure activity activates the different adenosine receptor subtypes and the implications for seizure activity in the rat hippocampus in vitro. Brief trains of high-frequency stimulation in nominally Mg(2+)-free artificial cerebrospinal fluid evoked epileptiform activity and resulted in a transient depression of the simultaneously recorded CA1 field excitatory postsynaptic potential. In the presence of 8-cyclopentyl-1,3-dimethylxanthine (CPT), an adenosine A(1) receptor antagonist, the occurrence of spontaneous seizure activity was greatly increased as was the duration and intensity of evoked seizures, whilst the postictal depression of basal synaptic transmission was greatly attenuated. Application of ZM 241385, an adenosine A(2A) receptor antagonist, shortened the duration of epileptiform activity, whereas administration of MRS 1191, an adenosine A(3) receptor antagonist, both decreased the duration and intensity of seizures. Combined application of the A(2A) and A(3) receptor antagonists also resulted in a reduction in seizure duration and intensity. However, no evidence was found for a role for protein kinase C in the regulation of seizure activity by endogenous adenosine. Our data confirm the dominant anticonvulsant role that endogenous and tonic adenosine play via the A(1) receptor, and suggest that the additional adenosine receptor subtypes may compromise this anticonvulsant property through promotion of seizure activity.
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Affiliation(s)
- Lori-An V Etherington
- Neurosciences Institute, Division of Pathology and Neuroscience, University of Dundee, Ninewells Hospital, Dundee DD1 9SY, Scotland, UK
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Quilichini PP, Diabira D, Chiron C, Milh M, Ben-Ari Y, Gozlan H. Effects of antiepileptic drugs on refractory seizures in the intact immature corticohippocampal formation in vitro. Epilepsia 2003; 44:1365-74. [PMID: 14636342 DOI: 10.1046/j.1528-1157.2003.19503.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE We developed a new in vitro preparation of immature rats, in which intact corticohippocampal formations (CHFs) depleted in magnesium ions become progressively epileptic. The better to characterize this model, we examined the effects of 14 antiepileptic drugs (AEDs) currently used in clinical practice. METHODS Recurrent ictal-like seizures (ILEs, four per hour) were generated in intact CHFs of P7-8 rats, and extracellular recordings were performed in the hippocampus and neocortex. AEDs were applied at clinically relevant concentrations (at least two), during 30 min after the third ILE. Their ability to prevent or to delay the next ILE was examined. RESULTS Valproic acid and benzodiazepines (clobazam and midazolam) but also phenobarbital and levetiracetam prevent the occurrence of seizures. In contrast, usual concentrations of carbamazepine (CBZ), phenytoin, vigabatrin, tiagabine, gabapentin, lamotrigine (LTG), topiramate, felbamate, and ethosuximide did not suppress ILEs. In addition, LTG and CBZ aggravate seizures in one third of the cases. CONCLUSIONS This intact in vitro preparation in immature animals appears to be quite resistant to most AEDs. Blockade of seizures was achieved with drugs acting mainly at the gamma-aminobutyric acid (GABA)A-receptor site but not with those that increase the amount of GABA. Drugs with a broad spectrum of activity are efficient but not those preferentially used in partial seizures or absences. We suggest that this preparation may correspond to a model of epilepsy with generalized convulsive seizures and could be helpful to develop new AEDs for refractory infantile epilepsies.
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Mangan PS, Kapur J. Factors underlying bursting behavior in a network of cultured hippocampal neurons exposed to zero magnesium. J Neurophysiol 2003; 91:946-57. [PMID: 14534286 PMCID: PMC2892720 DOI: 10.1152/jn.00547.2003] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Factors contributing to reduced magnesium-induced neuronal action potential bursting were investigated in primary hippocampal cell culture at high and low culture density. In nominally zero external magnesium medium, pyramidal neurons from high-density cultures produced recurrent spontaneous action potential bursts superimposed on prolonged depolarizations. These bursts were partially attenuated by the NMDA receptor antagonist d-APV. Pharmacological analysis of miniature excitatory postsynaptic currents (EPSCs) revealed 2 components: one sensitive to d-APV and another to the AMPA receptor antagonist DNQX. The components were kinetically distinct. Participation of NMDA receptors in reduced magnesium-induced synaptic events was supported by the localization of the NR1 subunit of the NMDA receptor with the presynaptic vesicular protein synaptophysin. Presynaptically, zero magnesium induced a significant increase in EPSC frequency likely attributable to increased neuronal hyperexcitability induced by reduced membrane surface charge screening. Mean quantal content was significantly increased in zero magnesium. Cells from low-density cultures did not exhibit action potential bursting in zero magnesium but did show increased EPSC frequency. Low-density neurons had less synaptophysin immunofluorescence and fewer active synapses as determined by FM1-43 analysis. These results demonstrate that multiple factors are involved in network bursting. Increased probability of transmitter release presynaptically, enhanced NMDA receptor-mediated excitability postsynaptically, and extent of neuronal interconnectivity contribute to initiation and maintenance of elevated network excitability.
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Affiliation(s)
- Patrick S Mangan
- Department of Neurology, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908, USA.
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Abstract
Layer 1 in the developing cerebral cortex is populated by two basic neuronal cell types, Cajal-Retzius (CR) cells and non-CR cells. We generated transgenic mice in which green fluorescent protein (GFP) was driven by the promoter of metabotropic glutamate receptor subtype 2 and expressed specifically in CR cells during cortical development. On the basis of the precise identification of CR cells with GFP fluorescence, we pursued developmental changes and synaptic mechanisms of both CR and non-CR cells during the postnatal period. Immunostaining in combination with GFP fluorescence imaging showed that GFP and reelin, a protein involved in corticogenesis, completely overlap in CR cells at postnatal day 0. At the subsequent postnatal stage, reelin-positive neurons are segregated and categorized into GFP-positive/GABA-negative CR cells and GFP-negative/GABA-positive non-CR cells. Individual and simultaneous whole-cell recordings of CR and non-CR cells in developing cerebral slices revealed that spontaneous and electrically evoked postsynaptic currents (sPSCs and ePSCs) measured in CR and non-CR cells are differentially mediated by GABA(A) receptors versus GABA(A), AMPA, and NMDA receptors, respectively. Furthermore, CR and non-CR cells show synchronized repetitive barrages of sPSCs that reflect a network-driven activity in the developing cerebral cortex. These findings imply that the layer 1 neurons dynamically change and play a distinct and integral role in the postnatal developing neocortex.
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