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Postnikova TY, Diespirov GP, Malkin SL, Chernyshev AS, Vylekzhanina EN, Zaitsev AV. Morphological and Functional Alterations in the CA1 Pyramidal Neurons of the Rat Hippocampus in the Chronic Phase of the Lithium-Pilocarpine Model of Epilepsy. Int J Mol Sci 2024; 25:7568. [PMID: 39062811 PMCID: PMC11276980 DOI: 10.3390/ijms25147568] [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: 06/20/2024] [Revised: 07/03/2024] [Accepted: 07/09/2024] [Indexed: 07/28/2024] Open
Abstract
Epilepsy is known to cause alterations in neural networks. However, many details of these changes remain poorly understood. The objective of this study was to investigate changes in the properties of hippocampal CA1 pyramidal neurons and their synaptic inputs in a rat lithium-pilocarpine model of epilepsy. In the chronic phase of the model, we found a marked loss of pyramidal neurons in the CA1 area. However, the membrane properties of the neurons remained essentially unaltered. The results of the electrophysiological and morphological studies indicate that the direct pathway from the entorhinal cortex to CA1 neurons is reinforced in epileptic animals, whereas the inputs to them from CA3 are either unaltered or even diminished. In particular, the dendritic spine density in the str. lacunosum moleculare, where the direct pathway from the entorhinal cortex terminates, was found to be 2.5 times higher in epileptic rats than in control rats. Furthermore, the summation of responses upon stimulation of the temporoammonic pathway was enhanced by approximately twofold in epileptic rats. This enhancement is believed to be a significant contributing factor to the heightened epileptic activity observed in the entorhinal cortex of epileptic rats using an ex vivo 4-aminopyridine model.
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Affiliation(s)
- Tatyana Y. Postnikova
- Sechenov Institute of Evolutionary Physiology and Biochemistry of RAS, Saint Petersburg 194223, Russia; (T.Y.P.); (G.P.D.); (S.L.M.); (E.N.V.)
| | - Georgy P. Diespirov
- Sechenov Institute of Evolutionary Physiology and Biochemistry of RAS, Saint Petersburg 194223, Russia; (T.Y.P.); (G.P.D.); (S.L.M.); (E.N.V.)
| | - Sergey L. Malkin
- Sechenov Institute of Evolutionary Physiology and Biochemistry of RAS, Saint Petersburg 194223, Russia; (T.Y.P.); (G.P.D.); (S.L.M.); (E.N.V.)
| | | | - Elizaveta N. Vylekzhanina
- Sechenov Institute of Evolutionary Physiology and Biochemistry of RAS, Saint Petersburg 194223, Russia; (T.Y.P.); (G.P.D.); (S.L.M.); (E.N.V.)
| | - Aleksey V. Zaitsev
- Sechenov Institute of Evolutionary Physiology and Biochemistry of RAS, Saint Petersburg 194223, Russia; (T.Y.P.); (G.P.D.); (S.L.M.); (E.N.V.)
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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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Boucher-Routhier M, Thivierge JP. A deep generative adversarial network capturing complex spiral waves in disinhibited circuits of the cerebral cortex. BMC Neurosci 2023; 24:22. [PMID: 36964493 PMCID: PMC10039524 DOI: 10.1186/s12868-023-00792-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 03/17/2023] [Indexed: 03/26/2023] Open
Abstract
BACKGROUND In the cerebral cortex, disinhibited activity is characterized by propagating waves that spread across neural tissue. In this pathological state, a widely reported form of activity are spiral waves that travel in a circular pattern around a fixed spatial locus termed the center of mass. Spiral waves exhibit stereotypical activity and involve broad patterns of co-fluctuations, suggesting that they may be of lower complexity than healthy activity. RESULTS To evaluate this hypothesis, we performed dense multi-electrode recordings of cortical networks where disinhibition was induced by perfusing a pro-epileptiform solution containing 4-Aminopyridine as well as increased potassium and decreased magnesium. Spiral waves were identified based on a spatially delimited center of mass and a broad distribution of instantaneous phases across electrodes. Individual waves were decomposed into "snapshots" that captured instantaneous neural activation across the entire network. The complexity of these snapshots was examined using a measure termed the participation ratio. Contrary to our expectations, an eigenspectrum analysis of these snapshots revealed a broad distribution of eigenvalues and an increase in complexity compared to baseline networks. A deep generative adversarial network was trained to generate novel exemplars of snapshots that closely captured cortical spiral waves. These synthetic waves replicated key features of experimental data including a tight center of mass, a broad eigenvalue distribution, spatially-dependent correlations, and a high complexity. By adjusting the input to the model, new samples were generated that deviated in systematic ways from the experimental data, thus allowing the exploration of a broad range of states from healthy to pathologically disinhibited neural networks. CONCLUSIONS Together, results show that the complexity of population activity serves as a marker along a continuum from healthy to disinhibited brain states. The proposed generative adversarial network opens avenues for replicating the dynamics of cortical seizures and accelerating the design of optimal neurostimulation aimed at suppressing pathological brain activity.
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Affiliation(s)
- Megan Boucher-Routhier
- School of Psychology, University of Ottawa, 156 Jean-Jacques Lussier, Ottawa, ON, K1N 6N5, Canada
| | - Jean-Philippe Thivierge
- School of Psychology, University of Ottawa, 156 Jean-Jacques Lussier, Ottawa, ON, K1N 6N5, Canada.
- University of Ottawa Brain and Mind Research Institute, 451 Smyth Rd., Ottawa, ON, K1H 8M5, Canada.
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CDDO-Me Attenuates Clasmatodendrosis in CA1 Astrocyte by Inhibiting HSP25-AKT Mediated DRP1-S637 Phosphorylation in Chronic Epilepsy Rats. Int J Mol Sci 2022; 23:ijms23094569. [PMID: 35562960 PMCID: PMC9105539 DOI: 10.3390/ijms23094569] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 04/14/2022] [Accepted: 04/18/2022] [Indexed: 01/27/2023] Open
Abstract
Clasmatodendrosis is one of the irreversible astroglial degeneration, which is involved in seizure duration and its progression in the epileptic hippocampus. Although sustained heat shock protein 25 (HSP25) induction leads to this autophagic astroglial death, dysregulation of mitochondrial dynamics (aberrant mitochondrial elongation) is also involved in the pathogenesis in clasmatodendrosis. However, the underlying molecular mechanisms of accumulation of elongated mitochondria in clasmatodendritic astrocytes are elusive. In the present study, we found that clasmatodendritic astrocytes showed up-regulations of HSP25 expression, AKT serine (S) 473 and dynamin-related protein 1 (DRP1) S637 phosphorylations in the hippocampus of chronic epilepsy rats. 2-Cyano-3,12-dioxo-oleana-1,9(11)-dien-28-oic acid methyl ester (CDDO-Me; bardoxolone methyl or RTA 402) abrogated abnormal mitochondrial elongation by reducing HSP25 upregulation, AKT S473- and DRP1 S637 phosphorylations. Furthermore, HSP25 siRNA and 3-chloroacetyl-indole (3CAI, an AKT inhibitor) abolished AKT-DRP1-mediated mitochondrial elongation and attenuated clasmatodendrosis in CA1 astrocytes. These findings indicate that HSP25-AKT-mediated DRP1 S637 hyper-phosphorylation may lead to aberrant mitochondrial elongation, which may result in autophagic astroglial degeneration. Therefore, our findings suggest that the dysregulation of HSP25-AKT-DRP1-mediated mitochondrial dynamics may play an important role in clasmatodendrosis, which would have implications for the development of novel therapies against various neurological diseases related to astroglial degeneration.
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Lado WE, Xu X, Hablitz JJ. Modulation of Epileptiform Activity by Three Subgroups of GABAergic Interneurons in Mouse Somatosensory Cortex. Epilepsy Res 2022; 183:106937. [DOI: 10.1016/j.eplepsyres.2022.106937] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 04/05/2022] [Accepted: 04/24/2022] [Indexed: 11/29/2022]
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Lamotrigine Attenuates Neuronal Excitability, Depresses GABA Synaptic Inhibition, and Modulates Theta Rhythms in Rat Hippocampus. Int J Mol Sci 2021; 22:ijms222413604. [PMID: 34948401 PMCID: PMC8705017 DOI: 10.3390/ijms222413604] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 11/29/2021] [Accepted: 12/05/2021] [Indexed: 12/03/2022] Open
Abstract
Theta oscillations generated in hippocampal (HPC) and cortical neuronal networks are involved in various aspects of brain function, including sensorimotor integration, movement planning, memory formation and attention. Disruptions of theta rhythms are present in individuals with brain disorders, including epilepsy and Alzheimer’s disease. Theta rhythm generation involves a specific interplay between cellular (ion channel) and network (synaptic) mechanisms. HCN channels are theta modulators, and several medications are known to enhance their activity. We investigated how different doses of lamotrigine (LTG), an HCN channel modulator, and antiepileptic and neuroprotective agent, would affect HPC theta rhythms in acute HPC slices (in vitro) and anaesthetized rats (in vivo). Whole-cell patch clamp recordings revealed that LTG decreased GABAA-fast transmission in CA3 cells, in vitro. In addition, LTG directly depressed CA3 and CA1 pyramidal neuron excitability. These effects were partially blocked by ZD 7288, a selective HCN blocker, and are consistent with decreased excitability associated with antiepileptic actions. Lamotrigine depressed HPC theta oscillations in vitro, also consistent with its neuronal depressant effects. In contrast, it exerted an opposite, enhancing effect, on theta recorded in vivo. The contradictory in vivo and in vitro results indicate that LTG increases ascending theta activating medial septum/entorhinal synaptic inputs that over-power the depressant effects seen in HPC neurons. These results provide new insights into LTG actions and indicate an opportunity to develop more precise therapeutics for the treatment of dementias, memory disorders and epilepsy.
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Righes Marafiga J, Vendramin Pasquetti M, Calcagnotto ME. In vitro Oscillation Patterns Throughout the Hippocampal Formation in a Rodent Model of Epilepsy. Neuroscience 2021; 479:1-21. [PMID: 34710537 DOI: 10.1016/j.neuroscience.2021.10.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 10/14/2021] [Accepted: 10/18/2021] [Indexed: 11/29/2022]
Abstract
Specific oscillatory patterns are considered biomarkers of pathological neuronal network in brain diseases, such as epilepsy. However, the dynamics of underlying oscillations during the epileptogenesis throughout the hippocampal formation in the temporal lobe epilepsy is not clear. Here, we characterized in vitro oscillatory patterns within the hippocampal formation of epileptic rats, under 4-aminopyridine (4-AP)-induced hyperexcitability and during the spontaneous network activity, at two periods of epileptogenesis. First, at the beginning of epileptic chronic phase, 30 days post-pilocarpine-induced Status Epilepticus (SE). Second, at the established epilepsy, 60 days post-SE. The 4-AP-bathed slices from epileptic rats had increased susceptibility to ictogenesis in CA1 at 30 days post-SE, and in entorhinal cortex and dentate gyrus at 60 days post-SE. Higher power and phase coherence were detected mainly for gamma and/or high frequency oscillations (HFOs), in a region- and stage-specific manner. Interestingly, under spontaneous network activity, even without 4-AP-induced hyperexcitability, slices from epileptic animals already exhibited higher power of gamma and HFOs in different areas of hippocampal formation at both periods of epileptogenesis, and higher phase coherence in fast ripples at 60 days post-SE. These findings reinforce the critical role of gamma and HFOs in each one of the hippocampal formation areas during ongoing neuropathological processes, tuning the neuronal network to epilepsy.
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Affiliation(s)
- Joseane Righes Marafiga
- Neurophysiology and Neurochemistry of Neuronal Excitability and Synaptic Plasticity Laboratory (NNNESP Lab.), Department of Biochemistry, ICBS, Universidade Federal do Rio Grande do Sul, Porto Alegre 90035-003, RS, Brazil; Graduate Program in Biological Science: Biochemistry, Universidade Federal do Rio Grande do Sul, Porto Alegre 90035-003, RS, Brazil
| | - Mayara Vendramin Pasquetti
- Neurophysiology and Neurochemistry of Neuronal Excitability and Synaptic Plasticity Laboratory (NNNESP Lab.), Department of Biochemistry, ICBS, Universidade Federal do Rio Grande do Sul, Porto Alegre 90035-003, RS, Brazil; Graduate Program in Biological Science: Biochemistry, Universidade Federal do Rio Grande do Sul, Porto Alegre 90035-003, RS, Brazil
| | - Maria Elisa Calcagnotto
- Neurophysiology and Neurochemistry of Neuronal Excitability and Synaptic Plasticity Laboratory (NNNESP Lab.), Department of Biochemistry, ICBS, Universidade Federal do Rio Grande do Sul, Porto Alegre 90035-003, RS, Brazil; Graduate Program in Biological Science: Biochemistry, Universidade Federal do Rio Grande do Sul, Porto Alegre 90035-003, RS, Brazil.
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Antiseizure Effects of Fully Characterized Non-Psychoactive Cannabis sativa L. Extracts in the Repeated 6-Hz Corneal Stimulation Test. Pharmaceuticals (Basel) 2021; 14:ph14121259. [PMID: 34959660 PMCID: PMC8703309 DOI: 10.3390/ph14121259] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 11/27/2021] [Accepted: 11/30/2021] [Indexed: 12/13/2022] Open
Abstract
Compounds present in Cannabis sativa L. preparations have recently attracted much attention in the treatment of drug-resistant epilepsy. Here, we screened two olive oil extracts from a non-psychoactive C. sativa variety, fully characterized by high-performance liquid chromatography and gas chromatography. Particularly, hemp oils with different concentrations of terpenes were administered at the same dose of cannabidiol (25 mg/kg/day orally), 1 h before the 6-Hz corneal stimulation test (44 mA). Mice were stimulated once a day for 5 days and evaluated by video-electrocorticographic recordings and behavioral analysis. Neuronal activation was assessed by FosB/ΔFosB immunoreactivity. Both oils significantly reduced the percentage of mice experiencing convulsive seizures in comparison to olive oil-treated mice (p < 0.050; Fisher’s exact test), but only the oil enriched with terpenes (K2) significantly accelerated full recovery from the seizure. These effects occurred in the presence of reduced power of delta rhythm, and, instead, increased power of theta rhythm, along with a lower FosB/ΔFosB expression in the subiculum (p < 0.050; Duncan’s method). The overall findings suggest that both cannabinoids and terpenes in oil extracts should be considered as potential therapeutic agents against epileptic seizures and epilepsy.
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Ghasemi Z, Naderi N, Shojaei A, Raoufy MR, Ahmadirad N, Barkley V, Mirnajafi-Zadeh J. Group I metabotropic glutamate receptors contribute to the antiepileptic effect of electrical stimulation in hippocampal CA1 pyramidal neurons. Epilepsy Res 2021; 178:106821. [PMID: 34839145 DOI: 10.1016/j.eplepsyres.2021.106821] [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: 05/31/2021] [Revised: 11/04/2021] [Accepted: 11/16/2021] [Indexed: 11/17/2022]
Abstract
Low-frequency deep brain stimulation (LFS) inhibits neuronal hyperexcitability during epilepsy. Accordingly, the use of LFS as a treatment method for patients with drug-resistant epilepsy has been proposed. However, the LFS antiepileptic mechanisms are not fully understood. Here, the role of metabotropic glutamate receptors group I (mGluR I) in LFS inhibitory action on epileptiform activity (EA) was investigated. EA was induced by increasing the K+ concentration in artificial cerebrospinal fluid (ACSF) up to 12 mM in hippocampal slices of male Wistar rats. LFS (1 Hz, 900 pulses) was delivered to the bundles of Schaffer collaterals at the beginning of EA. The excitability of CA1 pyramidal neurons was assayed by intracellular whole-cell recording. Applying LFS reduced the firing frequency during EA and substantially moved the membrane potential toward repolarization after a high-K+ ACSF washout. In addition, LFS attenuated the EA-generated neuronal hyperexcitability. A blockade of both mGluR 1 and mGluR 5 prevented the inhibitory action of LFS on EA-generated neuronal hyperexcitability. Activation of mGluR I mimicked the LFS effects and had similar inhibitory action on excitability of CA1 pyramidal neurons following EA. However, mGluR I agonist's antiepileptic action was not as strong as LFS. The observed LFS effects were significantly attenuated in the presence of a PKC inhibitor. Altogether, the LFS' inhibitory action on neuronal hyperexcitability following EA relies, in part, on the activity of mGluR I and a PKC-related signaling pathway.
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Affiliation(s)
- Zahra Ghasemi
- Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran; Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada
| | - Nima Naderi
- Department of Pharmacology and Toxicology, School of Pharmacy, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Amir Shojaei
- Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Mohammad Reza Raoufy
- Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Nooshin Ahmadirad
- Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Victoria Barkley
- Krembil Research Institute, University Health Network, Toronto, Canada
| | - Javad Mirnajafi-Zadeh
- Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran; Institute for Brain Sciences and Cognition, Tarbiat Modares University, Tehran, Iran.
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Lisgaras CP, Mikroulis A, Psarropoulou C. Region-specific Effects of Early-life Status Epilepticus on the Adult Hippocampal CA3 - Medial Entorhinal Cortex Circuitry In vitro: Focus on Interictal Spikes and Concurrent High-frequency Oscillations. Neuroscience 2021; 466:235-247. [PMID: 33961962 DOI: 10.1016/j.neuroscience.2021.04.030] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 04/25/2021] [Accepted: 04/26/2021] [Indexed: 11/29/2022]
Abstract
Convulsive status epilepticus (SE) in immature life is often associated with lasting neurobiological changes. We provoked SE by pentylenetetrazole in postnatal day 20 rat pups and examined communication modalities between the temporal hippocampus and medial entorhinal cortex (mEC) in vitro. After a minimum of 40 days post-SE, we prepared combined temporal hippocampal - medial entorhinal cortex (mEC) slices from conditioned (SE) and naïve (N) adult rats and recorded 4-aminopyridine-induced spontaneous epileptiform interictal-like discharges (IED) simultaneously from CA3 and mEC layer V-VI. We analyzed IED frequency and high frequency oscillations (HFOs) in intact slices and after surgical separation of hippocampus from mEC, by two successive incisions (Schaffer collateral cut, Parasubiculum cut). In all slices, IED frequency was higher in CA3 vs mEC (5N, 4SE) and Raster plots indicated no temporal coincidence between them either in intact or in CA1-cut slices (4N, 4SE). IED frequency was significantly higher in SE mEC, but similar in SE and N CA3, independently of connectivity state. Ripples (R) and Fast Ripples (FR) coincided with IEDs and their power differed between SE and N intact slices (22N, 12SE), both in CA3 and mEC. CA3 FR/R ratios were higher in the absence of mEC (14N, 8SE). Moreover, SE (vs N) slices showed significantly higher FR/R ratios independently of the presence of mEC. Taken together, these findings suggest lasting effects of immature SE in network dynamics governing hippocampal-entorhinal communication which may impact adult cognitive, behavioral, and/or seizure threshold sequalae.
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Affiliation(s)
- Christos Panagiotis Lisgaras
- Laboratory of Animal and Human Physiology, Department of Biological Applications and Technology, Faculty of Health Sciences, University of Ioannina, 45110 Ioannina, Greece.
| | - Apostolos Mikroulis
- Laboratory of Animal and Human Physiology, Department of Biological Applications and Technology, Faculty of Health Sciences, University of Ioannina, 45110 Ioannina, Greece.
| | - Caterina Psarropoulou
- Laboratory of Animal and Human Physiology, Department of Biological Applications and Technology, Faculty of Health Sciences, University of Ioannina, 45110 Ioannina, Greece.
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CDDO-Me Attenuates Astroglial Autophagy via Nrf2-, ERK1/2-SP1- and Src-CK2-PTEN-PI3K/AKT-Mediated Signaling Pathways in the Hippocampus of Chronic Epilepsy Rats. Antioxidants (Basel) 2021; 10:antiox10050655. [PMID: 33922531 PMCID: PMC8145743 DOI: 10.3390/antiox10050655] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 04/19/2021] [Accepted: 04/22/2021] [Indexed: 12/30/2022] Open
Abstract
Clasmatodendrosis is an autophagic astroglial death showing extensive swollen cell bodies with vacuoles and disintegrated/beaded processes. This astroglial degeneration is closely relevant to the synchronous epileptiform discharges. However, the underlying molecular mechanisms and the roles of clasmatodendrosis in spontaneous seizure activity are still unknown. The 2-cyano-3,12-dioxo-oleana-1,9(11)-dien-28-oic acid methyl ester (CDDO-Me; RTA 402) is one of the activators for nuclear factor-erythroid 2-related factor 2 (Nrf2) that is a redox-sensitive transcription factor. In the present study, we explored the effects of CDDO-Me on clasmatodendrosis in chronic epilepsy rats, which could prevent epilepsy-related complications. In the present study, clasmatodendritic astrocytes showed reduced Nrf2 expression and its nuclear accumulation, which were restored by CDDO-Me. CDDO-Me also abrogated heat shock protein 25 (HSP25) upregulation in clasmatodendritic astrocytes by regulating extracellular signal-related kinases 1/2 (ERK1/2)-specificity protein 1 (SP1)- and Src-casein kinase 2 (CK2)-phosphatase and tensin homolog deleted on chromosome 10 (PTEN)-phosphatidylinositol-3-kinase (PI3K)-AKT-glycogen synthase kinase 3β (GSK3β)-bax-interacting factor 1 (Bif-1)-mediated signaling pathways in chronic epilepsy rats. In addition, CDDO-Me ameliorated spontaneous seizure duration, but not seizure frequency and behavioral seizure severity. Therefore, our findings suggest that clasmatodendrosis may affect seizure duration in chronic epilepsy rats, and that CDDO-Me may attenuate autophagic astroglial degeneration by regulating various signaling pathways.
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Anticonvulsant effect of pterostilbene and its influence on the anxiety- and depression-like behavior in the pentetrazol-kindled mice: behavioral, biochemical, and molecular studies. Psychopharmacology (Berl) 2021; 238:3167-3181. [PMID: 34333674 PMCID: PMC8605980 DOI: 10.1007/s00213-021-05933-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 07/08/2021] [Indexed: 01/03/2023]
Abstract
RATIONALE Pterostilbene is the 3,5-dimethoxy derivative of resveratrol with numerous beneficial effects including neuroprotective properties. Experimental studies revealed its anticonvulsant action in the acute seizure tests. OBJECTIVES The purpose of the present study was to evaluate the effect of pterostilbene in the pentetrazol (PTZ)-induced kindling model of epilepsy in mice as well as to assess some possible mechanisms of its anticonvulsant action in this model. METHODS Mice were repeatedly treated with pterostilbene (50-200 mg/kg) and its effect on the development of seizure activity in the PTZ kindling was estimated. Influence of pterostilbene on the locomotor activity and anxiety- and depression-like behavior in the PTZ-kindled mice was also assessed. To understand the possible mechanisms of anticonvulsant activity of pterostilbene, γ-aminobutyric acid (GABA) and glutamate concentrations in the prefrontal cortex and hippocampus of the PTZ-kindled mice were measured using LC-MS/MS method. Moreover, mRNA expression of BDNF, TNF-α, IL-1β, IL-6, GABRA1A, and GRIN2B was determined by RT-qPCR technique. RESULTS We found that pterostilbene at a dose of 200 mg/kg considerably reduced seizure activity but did not influence the locomotor activity and depression- and anxiety-like behavior in the PTZ-kindled mice. In the prefrontal cortex and hippocampus, pterostilbene reversed the kindling-induced decrease of GABA concentration. Neither in the prefrontal cortex nor hippocampus pterostilbene affected mRNA expression of IL-1β, IL-6, GABRA1A, and GRIN2B augmented by PTZ kindling. Pterostilbene at a dose of 100 mg/kg significantly decreased BDNF and TNF-α mRNA expression in the hippocampus of the PTZ-kindled mice. CONCLUSIONS Although further studies are necessary to understand the mechanism of anticonvulsant properties of pterostilbene, our findings suggest that it might be considered a candidate for a new antiseizure drug.
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Lévesque M, Avoli M. The subiculum and its role in focal epileptic disorders. Rev Neurosci 2020; 32:249-273. [PMID: 33661586 DOI: 10.1515/revneuro-2020-0091] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 09/29/2020] [Indexed: 01/07/2023]
Abstract
The subicular complex (hereafter referred as subiculum), which is reciprocally connected with the hippocampus and rhinal cortices, exerts a major control on hippocampal outputs. Over the last three decades, several studies have revealed that the subiculum plays a pivotal role in learning and memory but also in pathological conditions such as mesial temporal lobe epilepsy (MTLE). Indeed, subicular networks actively contribute to seizure generation and this structure is relatively spared from the cell loss encountered in this focal epileptic disorder. In this review, we will address: (i) the functional properties of subicular principal cells under normal and pathological conditions; (ii) the subiculum role in sustaining seizures in in vivo models of MTLE and in in vitro models of epileptiform synchronization; (iii) its presumptive role in human MTLE; and (iv) evidence underscoring the relationship between subiculum and antiepileptic drug effects. The studies reviewed here reinforce the view that the subiculum represents a limbic area with relevant, as yet unexplored, roles in focal epilepsy.
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Affiliation(s)
- Maxime Lévesque
- Departments of Neurology and Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, 3801 University Street, Montreal, H3A 2B4Québec, Canada
| | - Massimo Avoli
- Departments of Neurology, Neurosurgery, and Physiology, Montreal Neurological Institute-Hospital, McGill University, 3801 University Street, Montreal, H3A 2B4Québec, Canada
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14
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Maciąg F, Majewski Ł, Boguszewski PM, Gupta RK, Wasilewska I, Wojtaś B, Kuznicki J. Behavioral and electrophysiological changes in female mice overexpressing ORAI1 in neurons. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:1137-1150. [PMID: 30659848 DOI: 10.1016/j.bbamcr.2019.01.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 12/20/2018] [Accepted: 01/10/2019] [Indexed: 11/15/2022]
Abstract
Orai proteins form highly selective Ca2+ release-activated channels (CRACs). They play a critical role in store-operated Ca2+ entry (SOCE; i.e., the influx of external Ca2+ that is induced by the depletion of endoplasmic reticulum Ca2+ stores). Of the three Orai homologs that are present in mammals (Orai1-3), the physiological function of Orai1 is the best described. CRACs are formed by both homomeric assemblies and heteromultimers of Orais. Orai1 and Orai2 can form heteromeric channels that differ in conductivity during SOCE, depending on their Orai1-to-Orai2 ratio. The present study explored the potential consequences of ORAI1 overexpression in neurons where the dominant isoform is Orai2. We established the Tg(ORAI1)Ibd transgenic mouse line that overexpresses ORAI1 in brain neurons. We observed seizure-like symptoms in aged (≥15-month-old) female mice but not in males of the same age. The application of kainic acid and bicuculline to slices that were isolated from 8-month-old (±1 month) female Tg(ORAI1)Ibd mice revealed a significantly lower frequency of interictal bursts compared with samples that were isolated from wildtype mice. No differences were observed in male mice of a similar age. A battery of behavioral tests showed that context recognition decreased only in female transgenic mice. The phenotype that was observed in female mice suggests that ORAI1 overexpression may affect neuronal activity in a sex-dependent manner. This article is part of a Special Issue entitled: ECS Meeting edited by Claus Heizmann, Joachim Krebs and Jacques Haiech.
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Affiliation(s)
- Filip Maciąg
- International Institute of Molecular and Cell Biology in Warsaw, 4 Ks. Trojdena Str., Warsaw 02-109, Poland
| | - Łukasz Majewski
- International Institute of Molecular and Cell Biology in Warsaw, 4 Ks. Trojdena Str., Warsaw 02-109, Poland.
| | - Paweł M Boguszewski
- Laboratory of Animal Models, Neurobiology Centre, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Str., Warsaw 02-093, Poland
| | - Rishikesh Kumar Gupta
- International Institute of Molecular and Cell Biology in Warsaw, 4 Ks. Trojdena Str., Warsaw 02-109, Poland
| | - Iga Wasilewska
- International Institute of Molecular and Cell Biology in Warsaw, 4 Ks. Trojdena Str., Warsaw 02-109, Poland
| | - Bartosz Wojtaś
- Laboratory of Molecular Neurobiology, Neurobiology Centre, Nencki Institute of Experimental Biology of Polish Academy of Sciences, Warsaw, Poland
| | - Jacek Kuznicki
- International Institute of Molecular and Cell Biology in Warsaw, 4 Ks. Trojdena Str., Warsaw 02-109, Poland
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Uncensored EEG: The role of DC potentials in neurobiology of the brain. Prog Neurobiol 2018; 165-167:51-65. [PMID: 29428834 DOI: 10.1016/j.pneurobio.2018.02.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 12/24/2017] [Accepted: 02/03/2018] [Indexed: 12/11/2022]
Abstract
Brain direct current (DC) potentials denote sustained shifts and slow deflections of cerebral potentials superimposed with conventional electroencephalography (EEG) waves and reflect alterations in the excitation level of the cerebral cortex and subcortical structures. Using galvanometers, such sustained displacement of the EEG baseline was recorded in the early days of EEG recordings. To stabilize the EEG baseline and eliminate artefacts, EEG was performed later by voltage amplifiers with high-pass filters that dismiss slow DC potentials. This left slow DC potential recordings as a neglected diagnostic source in the routine clinical setting over the last few decades. Brain DC waves may arise from physiological processes or pathological phenomena. Recordings of DC potentials are fundamental electro-clinical signatures of some neurological and psychological disorders and may serve as diagnostic, prognostic, and treatment monitoring tools. We here review the utility of both physiological and pathological brain DC potentials in different aspects of neurological and psychological disorders. This may enhance our understanding of the role of brain DC potentials and improve our fundamental clinical and research strategies for brain disorders.
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16
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D'Arcangelo G, Triossi T, Buglione A, Melchiorri G, Tancredi V. Modulation of synaptic plasticity by short-term aerobic exercise in adult mice. Behav Brain Res 2017; 332:59-63. [PMID: 28559180 DOI: 10.1016/j.bbr.2017.05.058] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 05/17/2017] [Accepted: 05/24/2017] [Indexed: 11/19/2022]
Abstract
Physiological effects of different types, of continuous and interval aerobic training, have been largely described and studied in the adult man. It was previously indicated that interval training plays an important role in maximizing both peripheral muscle and central cardiorespiratory adaptations, permitting significant functional improvement even in healthy sedentary subjects. Since the outcome of different aerobic training trials on cognitive processes had never been evaluated, we compared, on an experimental mouse model, the effects of four training exercise protocols, named respectively C100, I100, C50 and I50 depending on the volume and on the type of training proposed, continuous or interval method. Therefore, to asses quantitative and qualitative functional changes, we analyzed several physical parameters before and after 6 weeks training in all four groups with respect to the control sedentary animals and we studied synaptic plasticity, by extracellular in vitro recordings, in hippocampal mouse slices, a region involved in learning and memory processes. We found that all four protocols of exercise applied in this study exerted positive effects on both physical and training parameters inducing weight augmentation, strength endurance and aerobic endurance increase, and potentiation of motor coordination. However, the improvement observed failed to induce an enhancement in synaptic plasticity in three out of four exercise protocols and only in the slices from mice trained with the interval 50% volume exercise the long term potentiation (LTP) increased with respect to the sedentary group. These findings suggest that motor activity exerts positive effects on cognitive processes provided that certain principles are respected, such as the training load and the elements of which it is composed, in order to plan the right quantitative and qualitative parameters and the appropriate recovery periods.
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Affiliation(s)
- G D'Arcangelo
- Department of Medical Systems, University of Rome Tor Vergata, Via Montpellier 1, 00133 Rome, Italy.
| | - T Triossi
- Department of Medical Systems, University of Rome Tor Vergata, Via Montpellier 1, 00133 Rome, Italy
| | - A Buglione
- Department of Medical Systems, University of Rome Tor Vergata, Via Montpellier 1, 00133 Rome, Italy
| | - G Melchiorri
- Department of Medical Systems, University of Rome Tor Vergata, Via Montpellier 1, 00133 Rome, Italy
| | - V Tancredi
- Department of Medical Systems, University of Rome Tor Vergata, Via Montpellier 1, 00133 Rome, Italy
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17
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Abstract
Pathological high-frequency oscillations (HFOs) (80-800 Hz) are considered biomarkers of epileptogenic tissue, but the underlying complex neuronal events are not well understood. Here, we identify and discuss several outstanding issues or conundrums in regards to the recording, analysis, and interpretation of HFOs in the epileptic brain to critically highlight what is known and what is not about these enigmatic events. High-frequency oscillations reflect a range of neuronal processes contributing to overlapping frequencies from the lower 80 Hz to the very fast spectral frequency bands. Given their complex neuronal nature, HFOs are extremely sensitive to recording conditions and analytical approaches. We provide a list of recommendations that could help to obtain comparable HFO signals in clinical and basic epilepsy research. Adopting basic standards will facilitate data sharing and interpretation that collectively will aid in understanding the role of HFOs in health and disease for translational purpose.
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18
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Vismer MS, Forcelli PA, Skopin MD, Gale K, Koubeissi MZ. The piriform, perirhinal, and entorhinal cortex in seizure generation. Front Neural Circuits 2015; 9:27. [PMID: 26074779 PMCID: PMC4448038 DOI: 10.3389/fncir.2015.00027] [Citation(s) in RCA: 116] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 05/15/2015] [Indexed: 12/11/2022] Open
Abstract
Understanding neural network behavior is essential to shed light on epileptogenesis and seizure propagation. The interconnectivity and plasticity of mammalian limbic and neocortical brain regions provide the substrate for the hypersynchrony and hyperexcitability associated with seizure activity. Recurrent unprovoked seizures are the hallmark of epilepsy, and limbic epilepsy is the most common type of medically-intractable focal epilepsy in adolescents and adults that necessitates surgical evaluation. In this review, we describe the role and relationships among the piriform (PIRC), perirhinal (PRC), and entorhinal cortex (ERC) in seizure-generation and epilepsy. The inherent function, anatomy, and histological composition of these cortical regions are discussed. In addition, the neurotransmitters, intrinsic and extrinsic connections, and the interaction of these regions are described. Furthermore, we provide evidence based on clinical research and animal models that suggest that these cortical regions may act as key seizure-trigger zones and, even, epileptogenesis.
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Affiliation(s)
- Marta S Vismer
- Department of Neurology, The George Washington University Washington, DC, USA
| | | | - Mark D Skopin
- Department of Neurology, The George Washington University Washington, DC, USA
| | - Karen Gale
- Department of Pharmacology, Georgetown University Washington, DC, USA
| | - Mohamad Z Koubeissi
- Department of Neurology, The George Washington University Washington, DC, USA
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19
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Behr C, D'Antuono M, Hamidi S, Herrington R, Lévesque M, Salami P, Shiri Z, Köhling R, Avoli M. Limbic networks and epileptiform synchronization: the view from the experimental side. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2014; 114:63-87. [PMID: 25078499 DOI: 10.1016/b978-0-12-418693-4.00004-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In this review, we summarize findings obtained in acute and chronic epilepsy models and in particular experiments that have revealed how neuronal networks in the limbic system-which is closely involved in the pathophysiogenesis of mesial temporal lobe epilepsy (MTLE)-produce hypersynchronous discharges. MTLE is often associated with a typical pattern of brain damage known as mesial temporal sclerosis, and it is one of the most refractory forms of partial epilepsy in adults. Specifically, we will address the cellular and pharmacological features of abnormal electrographic events that, as in MTLE patients, can occur in in vivo and in vitro animal models; these include interictal and ictal discharges along with high-frequency oscillations. In addition, we will consider how different limbic structures made hyperexcitable by acute pharmacological manipulations interact during epileptiform discharge generation. We will also review the electrographic characteristics of two types of seizure onsets that are most commonly seen in human and experimental MTLE as well as in in vitro models of epileptiform synchronization. Finally, we will address the role played by neurosteroids in reducing epileptiform synchronization and in modulating epileptogenesis.
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Affiliation(s)
- Charles Behr
- Department of Neurology, Neurosurgery and Physiology, Montréal Neurological Institute, Montréal, Québec, Canada
| | - Margherita D'Antuono
- Department of Neurology, Neurosurgery and Physiology, Montréal Neurological Institute, Montréal, Québec, Canada
| | - Shabnam Hamidi
- Department of Neurology, Neurosurgery and Physiology, Montréal Neurological Institute, Montréal, Québec, Canada
| | - Rochelle Herrington
- Department of Neurology, Neurosurgery and Physiology, Montréal Neurological Institute, Montréal, Québec, Canada
| | - Maxime Lévesque
- Department of Neurology, Neurosurgery and Physiology, Montréal Neurological Institute, Montréal, Québec, Canada
| | - Pariya Salami
- Department of Neurology, Neurosurgery and Physiology, Montréal Neurological Institute, Montréal, Québec, Canada
| | - Zahra Shiri
- Department of Neurology, Neurosurgery and Physiology, Montréal Neurological Institute, Montréal, Québec, Canada
| | - Rüdiger Köhling
- Institute of Physiology, University of Rostock, Rostock, Germany
| | - Massimo Avoli
- Department of Neurology, Neurosurgery and Physiology, Montréal Neurological Institute, Montréal, Québec, Canada; Department of Experimental Medicine, Facoltà di Medicina e Odontoiatria, Sapienza Università di Roma, Roma, Italy.
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20
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Biagini G, D'Antuono M, Benini R, de Guzman P, Longo D, Avoli M. Perirhinal cortex and temporal lobe epilepsy. Front Cell Neurosci 2013; 7:130. [PMID: 24009554 PMCID: PMC3756799 DOI: 10.3389/fncel.2013.00130] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 08/01/2013] [Indexed: 12/30/2022] Open
Abstract
The perirhinal cortex—which is interconnected with several limbic structures and is intimately involved in learning and memory—plays major roles in pathological processes such as the kindling phenomenon of epileptogenesis and the spread of limbic seizures. Both features may be relevant to the pathophysiology of mesial temporal lobe epilepsy that represents the most refractory adult form of epilepsy with up to 30% of patients not achieving adequate seizure control. Compared to other limbic structures such as the hippocampus or the entorhinal cortex, the perirhinal area remains understudied and, in particular, detailed information on its dysfunctional characteristics remains scarce; this lack of information may be due to the fact that the perirhinal cortex is not grossly damaged in mesial temporal lobe epilepsy and in models mimicking this epileptic disorder. However, we have recently identified in pilocarpine-treated epileptic rats the presence of selective losses of interneuron subtypes along with increased synaptic excitability. In this review we: (i) highlight the fundamental electrophysiological properties of perirhinal cortex neurons; (ii) briefly stress the mechanisms underlying epileptiform synchronization in perirhinal cortex networks following epileptogenic pharmacological manipulations; and (iii) focus on the changes in neuronal excitability and cytoarchitecture of the perirhinal cortex occurring in the pilocarpine model of mesial temporal lobe epilepsy. Overall, these data indicate that perirhinal cortex networks are hyperexcitable in an animal model of temporal lobe epilepsy, and that this condition is associated with a selective cellular damage that is characterized by an age-dependent sensitivity of interneurons to precipitating injuries, such as status epilepticus.
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Affiliation(s)
- Giuseppe Biagini
- Laboratory of Experimental Epileptology, Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia Modena, Italy
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21
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Avoli M, de Curtis M, Köhling R. Does interictal synchronization influence ictogenesis? Neuropharmacology 2013; 69:37-44. [PMID: 22776544 PMCID: PMC4878915 DOI: 10.1016/j.neuropharm.2012.06.044] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Revised: 04/19/2012] [Accepted: 06/25/2012] [Indexed: 02/07/2023]
Abstract
The EEG recorded from epileptic patients presents with interictal discharges that are not associated with detectable clinical symptoms but are valuable for diagnostic purposes. Experimental studies have shown that interictal discharges and ictal events (i.e., seizures) are characterized intracellularly by similar (but for duration) neuronal depolarizations leading to sustained action potential firing, thus indicating that they may share similar cellular and pharmacological mechanisms. It has also been proposed that interictal discharges may herald the onset of electrographic seizures, but other studies have demonstrated that interictal events interfere with the occurrence of ictal activity. The relationship between interictal and ictal activity thus remains ambiguous. Here we will review this issue in animal models of limbic seizures that are electrographically close to those seen in TLE patients. In particular we will: (i) focus on the electrophysiological and pharmacological characteristics of, at least, two types of interictal discharge; (ii) propose that they play opposite roles in leading to ictogenesis; and (iii) discuss the possibility that mimicking one of these two types of interictal activity by low frequency repetitive stimulation can control ictogenesis. Finally, we will also review evidence indicating that specific types of interictal discharge may play a role in epileptogenesis. This article is part of the Special Issue entitled 'New Targets and Approaches to the Treatment of Epilepsy'.
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Affiliation(s)
- Massimo Avoli
- Montreal Neurological Institute, Department of Neurology & Neurosurgery, McGill University, 3801 University St., Montréal, H3A 2B4 Québec, Canada.
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22
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Ferrea E, Maccione A, Medrihan L, Nieus T, Ghezzi D, Baldelli P, Benfenati F, Berdondini L. Large-scale, high-resolution electrophysiological imaging of field potentials in brain slices with microelectronic multielectrode arrays. Front Neural Circuits 2012; 6:80. [PMID: 23162432 PMCID: PMC3496908 DOI: 10.3389/fncir.2012.00080] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Accepted: 10/17/2012] [Indexed: 11/13/2022] Open
Abstract
Multielectrode arrays (MEAs) are extensively used for electrophysiological studies on brain slices, but the spatial resolution and field of recording of conventional arrays are limited by the low number of electrodes available. Here, we present a large-scale array recording simultaneously from 4096 electrodes used to study propagating spontaneous and evoked network activity in acute murine cortico-hippocampal brain slices at unprecedented spatial and temporal resolution. We demonstrate that multiple chemically induced epileptiform episodes in the mouse cortex and hippocampus can be classified according to their spatio-temporal dynamics. Additionally, the large-scale and high-density features of our recording system enable the topological localization and quantification of the effects of antiepileptic drugs in local neuronal microcircuits, based on the distinct field potential propagation patterns. This novel high-resolution approach paves the way to detailed electrophysiological studies in brain circuits spanning spatial scales from single neurons up to the entire slice network.
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Affiliation(s)
- E Ferrea
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia Genoa, Italy
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23
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Jefferys JGR, Menendez de la Prida L, Wendling F, Bragin A, Avoli M, Timofeev I, Lopes da Silva FH. Mechanisms of physiological and epileptic HFO generation. Prog Neurobiol 2012; 98:250-64. [PMID: 22420980 DOI: 10.1016/j.pneurobio.2012.02.005] [Citation(s) in RCA: 227] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Revised: 02/24/2012] [Accepted: 02/27/2012] [Indexed: 10/28/2022]
Abstract
High frequency oscillations (HFO) have a variety of characteristics: band-limited or broad-band, transient burst-like phenomenon or steady-state. HFOs may be encountered under physiological or under pathological conditions (pHFO). Here we review the underlying mechanisms of oscillations, at the level of cells and networks, investigated in a variety of experimental in vitro and in vivo models. Diverse mechanisms are described, from intrinsic membrane oscillations to network processes involving different types of synaptic interactions, gap junctions and ephaptic coupling. HFOs with similar frequency ranges can differ considerably in their physiological mechanisms. The fact that in most cases the combination of intrinsic neuronal membrane oscillations and synaptic circuits are necessary to sustain network oscillations is emphasized. Evidence for pathological HFOs, particularly fast ripples, in experimental models of epilepsy and in human epileptic patients is scrutinized. The underlying mechanisms of fast ripples are examined both in the light of animal observations, in vivo and in vitro, and in epileptic patients, with emphasis on single cell dynamics. Experimental observations and computational modeling have led to hypotheses for these mechanisms, several of which are considered here, namely the role of out-of-phase firing in neuronal clusters, the importance of strong excitatory AMPA-synaptic currents and recurrent inhibitory connectivity in combination with the fast time scales of IPSPs, ephaptic coupling and the contribution of interneuronal coupling through gap junctions. The statistical behaviour of fast ripple events can provide useful information on the underlying mechanism and can help to further improve classification of the diverse forms of HFOs.
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Affiliation(s)
- John G R Jefferys
- Neuronal Networks Group, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham B15 2TT, UK.
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24
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Huang HL, Lin CC, Jeng KCG, Yao PW, Chuang LT, Kuo SL, Hou CW. Fresh green tea and gallic acid ameliorate oxidative stress in kainic acid-induced status epilepticus. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2012; 60:2328-2336. [PMID: 22324774 DOI: 10.1021/jf203709q] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Green tea is one of the most-consumed beverages due to its taste and antioxidative polyphenols. However, the protective effects of green tea and its constituent, gallic acid (GA), against kainic acid (KA)-induced seizure have not been studied. We investigated the effect of fresh green tea leaf (GTL) and GA on KA-induced neuronal injury in vivo and in vitro. The results showed that GTL and GA reduced the maximal seizure classes, predominant behavioral seizure patterns, and lipid peroxidation in male FVB mice with status epilepticus (SE). GTL extract and GA provided effective protection against KA-stressed PC12 cells in a dose-dependent manner. In the protective mechanism study, GTL and GA decreased Ca(2+) release, ROS, and lipid peroxidation from KA-stressed PC12 cells. Western blot results revealed that mitogen-activated protein kinases (MAPKs), RhoA, and COX-2 expression were increased in PC12 cells under KA stress, and expression of COX-2 and p38 MAPK, but not RhoA, was significantly reduced by GTL and GA. Furthermore, GTL and GA were able to reduce PGE(2) production from KA-stressed PC12 cells. Taken together, the results showed that GTL and GA provided neuroprotective effects against excitotoxins and may have a clinical application in epilepsy.
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Affiliation(s)
- Hsiao-Ling Huang
- Department of Healthcare Management, Yuanpei University, Hsinchu, Taiwan
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25
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Hou CW. Pu-Erh tea and GABA attenuates oxidative stress in kainic acid-induced status epilepticus. J Biomed Sci 2011; 18:75. [PMID: 22014163 PMCID: PMC3217899 DOI: 10.1186/1423-0127-18-75] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Accepted: 10/20/2011] [Indexed: 12/19/2022] Open
Abstract
Background Pu-Erh tea is one of the most-consumed beverages due to its taste and the anti-anxiety-producing effect of the gamma-aminobutyric acid (GABA) if contains. However the protective effects of Pu-Erh tea and its constituent, GABA to kainic acid (KA)-induced seizure have not been fully investigated. Methods We analyzed the effect of Pu-Erh tea leaf (PETL) and GABA on KA-induced neuronal injury in vivo and in vitro. Results PETL and GABA reduced the maximal seizure classes, predominant behavioral seizure patterns, and lipid peroxidation in male FVB mice with status epilepticus. PETL extracts and GABA were effective in protecting KA-treated PC12 cells in a dose-dependent manner and they decreased Ca2+ release, ROS production and lipid peroxidation from KA-stressed PC12 cells. Western blot results revealed that mitogen-activated protein kinases (MAPKs), RhoA and cyclo-oxygenase-2 (COX-2) expression were increased in PC12 cells under KA stress, and PETL and GABA significantly reduced COX-2 and p38 MAPK expression, but not that of RhoA. Furthermore, PETL and GABA reduced PGE2 production from KA-induced PC12 cells. Conclusions Taken together, PETL and GABA have neuroprotective effects against excitotoxins that may have clinical applications in epilepsy.
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Affiliation(s)
- Chien-Wei Hou
- Department of Biotechnology, Yuanpei University, Hsinchu, Taiwan.
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26
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Avoli M, de Curtis M. GABAergic synchronization in the limbic system and its role in the generation of epileptiform activity. Prog Neurobiol 2011; 95:104-32. [PMID: 21802488 PMCID: PMC4878907 DOI: 10.1016/j.pneurobio.2011.07.003] [Citation(s) in RCA: 190] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 07/14/2011] [Accepted: 07/15/2011] [Indexed: 11/30/2022]
Abstract
GABA is the main inhibitory neurotransmitter in the adult forebrain, where it activates ionotropic type A and metabotropic type B receptors. Early studies have shown that GABA(A) receptor-mediated inhibition controls neuronal excitability and thus the occurrence of seizures. However, more complex, and at times unexpected, mechanisms of GABAergic signaling have been identified during epileptiform discharges over the last few years. Here, we will review experimental data that point at the paradoxical role played by GABA(A) receptor-mediated mechanisms in synchronizing neuronal networks, and in particular those of limbic structures such as the hippocampus, the entorhinal and perirhinal cortices, or the amygdala. After having summarized the fundamental characteristics of GABA(A) receptor-mediated mechanisms, we will analyze their role in the generation of network oscillations and their contribution to epileptiform synchronization. Whether and how GABA(A) receptors influence the interaction between limbic networks leading to ictogenesis will be also reviewed. Finally, we will consider the role of altered inhibition in the human epileptic brain along with the ability of GABA(A) receptor-mediated conductances to generate synchronous depolarizing events that may lead to ictogenesis in human epileptic disorders as well.
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Affiliation(s)
- Massimo Avoli
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery, and of Physiology, McGill University, Montreal H3A 2B4 Quebec, Canada.
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27
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Lévesque M, Bortel A, Gotman J, Avoli M. High-frequency (80-500 Hz) oscillations and epileptogenesis in temporal lobe epilepsy. Neurobiol Dis 2011; 42:231-41. [PMID: 21238589 PMCID: PMC4873283 DOI: 10.1016/j.nbd.2011.01.007] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Revised: 11/17/2010] [Accepted: 01/02/2011] [Indexed: 11/25/2022] Open
Abstract
High-frequency oscillations (HFOs), termed ripples (80-200 Hz) and fast ripples (250-600 Hz), are recorded in the EEG of epileptic patients and in animal epilepsy models; HFOs are thought to reflect pathological activity and seizure onset zones. Here, we analyzed the temporal and spatial evolution of interictal spikes with and without HFOs in the rat pilocarpine model of temporal lobe epilepsy. Depth electrode recordings from dentate gyrus (DG), CA3 region, subiculum and entorhinal cortex (EC), were obtained from rats between the 4th and 15th day after a status epilepticus (SE) induced by i.p. injection of pilocarpine. The first seizure occurred 6.1 ± 2.5 days after SE (n = 7 rats). Five of 7 animals exhibited interictal spikes that co-occurred with fast ripples accounting for 4.9 ± 4.6% of all analyzed interictal spikes (n = 12,886) while all rats showed interictal spikes co-occurring with ripples, accounting for 14.3 ± 3.4% of all events. Increased rates of interictal spikes without HFOs in the EC predicted upcoming seizures on the following day, while rates of interictal spikes with fast ripples in CA3 reflected periods of high seizure occurrence. Finally, interictal spikes co-occurring with ripples did not show any specific relation to seizure occurrence. Our findings identify different temporal and spatial developmental patterns for the rates of interictal spikes with or without HFOs in relation with seizure occurrence. These distinct categories of interictal spikes point at dynamic processes that should bring neuronal networks close to seizure generation.
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Affiliation(s)
- Maxime Lévesque
- Montreal Neurological Institute and Department of Neurology & Neurosurgery, McGill University, 3801 University Street, Montreal, Qc, Canada H3A 2B4
| | - Aleksandra Bortel
- Montreal Neurological Institute and Department of Neurology & Neurosurgery, McGill University, 3801 University Street, Montreal, Qc, Canada H3A 2B4
| | - Jean Gotman
- Montreal Neurological Institute and Department of Neurology & Neurosurgery, McGill University, 3801 University Street, Montreal, Qc, Canada H3A 2B4
| | - Massimo Avoli
- Montreal Neurological Institute and Department of Neurology & Neurosurgery, McGill University, 3801 University Street, Montreal, Qc, Canada H3A 2B4
- Dipartimento di Medicina Sperimentale, Sapienza Università di Roma, Viale del Castro Laurenziano 9, 00185 Roma, Italy
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Hsieh PF, Hou CW, Yao PW, Wu SP, Peng YF, Shen ML, Lin CH, Chao YY, Chang MH, Jeng KC. Sesamin ameliorates oxidative stress and mortality in kainic acid-induced status epilepticus by inhibition of MAPK and COX-2 activation. J Neuroinflammation 2011; 8:57. [PMID: 21609430 PMCID: PMC3129306 DOI: 10.1186/1742-2094-8-57] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Accepted: 05/24/2011] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND Kainic acid (KA)-induced status epilepticus (SE) was involved with release of free radicals. Sesamin is a well-known antioxidant from sesame seeds and it scavenges free radicals in several brain injury models. However the neuroprotective mechanism of sesamin to KA-induced seizure has not been studied. METHODS Rodents (male FVB mice and Sprague-Dawley rats) were fed with sesamin extract (90% of sesamin and 10% sesamolin), 15 mg/kg or 30 mg/kg, for 3 days before KA subcutaneous injection. The effect of sesamin on KA-induced cell injury was also investigated on several cellular pathways including neuronal plasticity (RhoA), neurodegeneration (Caspase-3), and inflammation (COX-2) in PC12 cells and microglial BV-2 cells. RESULTS Treatment with sesamin extract (30 mg/kg) significantly increased plasma α-tocopherol level 50% and 55.8% from rats without and with KA treatment, respectively. It also decreased malondialdehyde (MDA) from 145% to 117% (p=0.017) and preserved superoxide dismutase from 55% of the vehicle control mice to 81% of sesamin-treated mice, respectively to the normal levels (p=0.013). The treatment significantly decreased the mortality from 22% to 0% in rats. Sesamin was effective to protect PC12 cells and BV-2 cells from KA-injury in a dose-dependent manner. It decreased the release of Ca2+, reactive oxygen species, and MDA from PC12 cells. Western blot analysis revealed that sesamin significantly reduced ERK1/2, p38 mitogen-activated protein kinases, Caspase-3, and COX-2 expression in both cells and RhoA expression in BV-2 cells. Furthermore, Sesamin was able to reduce PGE2 production from both cells under KA-stimulation. CONCLUSIONS Taken together, it suggests that sesamin could protect KA-induced brain injury through anti-inflammatory and partially antioxidative mechanisms.
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Affiliation(s)
- Peiyuan F Hsieh
- Division of Neurology, Department of Medical Research, Taichung Veterans General Hospital, Taichung, Taiwan.
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Convulsive status epilepticus duration as determinant for epileptogenesis and interictal discharge generation in the rat limbic system. Neurobiol Dis 2010; 40:478-89. [PMID: 20682341 DOI: 10.1016/j.nbd.2010.07.015] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Revised: 07/22/2010] [Accepted: 07/26/2010] [Indexed: 11/24/2022] Open
Abstract
We analyzed with EEG-video monitoring the epileptic activity recorded during the latent and chronic periods in rats undergoing 30 or 120 min pilocarpine-induced convulsive status epilepticus (SE). Interictal discharges frequency in the entorhinal cortex (EC) of animals exposed to 120 min SE was significantly higher in the chronic than in the latent period. Following seizure appearance, interictal spikes diminished in duration in the CA3 of the 120 min SE group, and occurred at higher rates in the amygdala in all animals. Rats exposed to 120 min SE generated shorter seizures but presented twice as many non-convulsive seizures per day as the 30 min group. Finally, seizures most frequently initiated in CA3 in the 120 min SE group but had similar onset in CA3 and EC in the 30 min group. These findings indicate that convulsive SE duration influences the development of interictal and ictal activity, and that interictal discharges undergo structure-specific changes after seizure appearance.
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30
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Abstract
Interictal spiking is seen in the EEG of epileptic patients between seizures. To date, the roles played by interictal events in seizure occurrence and in epileptogenesis remain elusive. While interictal spikes may herald the onset of electrographic seizures, experimental data indicate that hippocampus-driven interictal events prevent seizure precipitation. Even less clear than the role of interictal events in seizure occurrence is whether and how interictal spikes contribute to epileptogenesis. Thus, while plastic changes within limbic neuronal networks may result from ongoing interictal activity, experimental evidence supports the view that epileptogenesis is accompanied by a decrease in hippocampus-driven interictal activity.
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Affiliation(s)
- Massimo Avoli
- Montreal Neurological Institute and Department of Neurology & Neurosurgery, McGill University, Montréal, Canada
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31
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Panuccio G, D'Antuono M, de Guzman P, De Lannoy L, Biagini G, Avoli M. In vitro ictogenesis and parahippocampal networks in a rodent model of temporal lobe epilepsy. Neurobiol Dis 2010; 39:372-80. [PMID: 20452424 DOI: 10.1016/j.nbd.2010.05.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2010] [Revised: 04/14/2010] [Accepted: 05/01/2010] [Indexed: 12/29/2022] Open
Abstract
Temporal lobe epilepsy (TLE) is a chronic epileptic disorder involving the hippocampal formation. Details on the interactions between the hippocampus proper and parahippocampal networks during ictogenesis remain, however, unclear. In addition, recent findings have shown that epileptic limbic networks maintained in vitro are paradoxically less responsive than non-epileptic control (NEC) tissue to application of the convulsant drug 4-aminopyridine (4AP). Field potential recordings allowed us to establish here the effects of 4AP in brain slices obtained from NEC and pilocarpine-treated epileptic rats; these slices included the hippocampus and parahippocampal areas such as entorhinal and perirhinal cortices and the amygdala. First, we found that both types of tissue generate epileptiform discharges with similar electrographic characteristics. Further investigation showed that generation of robust ictal-like discharges in the epileptic rat tissue is (i) favored by decreased hippocampal output (ii) reinforced by EC-subiculum interactions and (iii) predominantly driven by amygdala networks. We propose that a functional switch to alternative synaptic routes may promote network hyperexcitability in the epileptic limbic system.
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Affiliation(s)
- G Panuccio
- Montreal Neurological Institute and Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada
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32
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Differential expressions of aquaporin subtypes in astroglia in the hippocampus of chronic epileptic rats. Neuroscience 2009; 163:781-9. [PMID: 19619613 DOI: 10.1016/j.neuroscience.2009.07.028] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2009] [Revised: 07/11/2009] [Accepted: 07/13/2009] [Indexed: 11/23/2022]
Abstract
In order to elucidate the roles of aquaporins (AQPs) in astroglial responses, we investigated AQP expressions in the experimental epileptic hippocampus. In control animals, AQP1 protein expression was restricted to the ventricular-facing surface of the choroid plexus. AQP4 was expressed in astrocyte foot processes near blood vessels and in ependymal and pial surfaces in contact with cerebrospinal fluid. AQP9 protein has been detected in cells lining the cerebral ventricles, and in astrocytes. Six to eight weeks after status epilepticus (SE), AQP1 expression was mainly, but not all, detected in vacuolized astrocytes, which were localized in the stratum radiatum of the CA1 region. AQP4 was negligible in vacuolized CA1 astrocytes, although AQP4 immunoreactivity in non-vacuolized astrocytes was increased as compared to control level. AQP9 expression was shown to be mainly induced in non-vacuolized CA1 astrocytes. Therefore, our findings suggest that AQP subunits may play differential roles in various astroglial responses (including astroglial swelling and astroglial loss) in the chronic epileptic hippocampus.
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Kim DS, Kim JE, Kwak SE, Choi KC, Kim DW, Kwon OS, Choi SY, Kang TC. Spatiotemporal characteristics of astroglial death in the rat hippocampo-entorhinal complex following pilocarpine-induced status epilepticus. J Comp Neurol 2009; 511:581-98. [PMID: 18853423 DOI: 10.1002/cne.21851] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Recently we reported that astroglial loss and subsequent gliogenesis in the dentate gyrus play a role in epileptogenesis following pilocarpine-induced status epilepticus (SE). In the present study we investigated whether astroglial damages in the hippocampo-entorhinal complex following SE are relevant to pathological or electrophysiological properties of temporal lobe epilepsy. Astroglial loss/damage was observed in the entorhinal cortex and the CA1 region at 4 weeks and 8 weeks after SE, respectively. These astroglial responses in the hippocampo-entorhinal cortex were accompanied by hyperexcitability of the CA1 region (impairment of paired-pulse inhibition and increase in excitability ratio). Unlike the dentate gyrus and the entorhinal cortex, CA1 astroglial damage was protected by conventional anti-epileptic drugs. alpha-Aminoadipic acid (a specific astroglial toxin) infusion into the entorhinal cortex induced astroglial damage and changed the electrophysiological properties in the CA1 region. Astroglial regeneration in the dentate gyrus and the stratum oriens of the CA1 region was found to originate from gliogenesis, while that in the entorhinal cortex and stratum radiatum of the CA1 region originated from in situ proliferation. These findings suggest that regional specific astroglial death/regeneration patterns may play an important role in the pathogenesis of temporal lobe epilepsy.
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Affiliation(s)
- Duk-Soo Kim
- Department of Anatomy and Neurobiology, College of Medicine, Hallym University, Chunchon 200-702, South Korea
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34
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Sankar T, Bernasconi N, Kim H, Bernasconi A. Temporal lobe epilepsy: differential pattern of damage in temporopolar cortex and white matter. Hum Brain Mapp 2008; 29:931-44. [PMID: 17636561 PMCID: PMC6870675 DOI: 10.1002/hbm.20437] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Our purpose was to quantify structural changes of the temporopolar cortex (TPC) and its white matter (TPWM) in temporal lobe epilepsy (TLE) using MRI volumetry and texture analysis. We studied 23 patients with hippocampal atrophy, and 20 healthy controls. Gradient magnitude and entropy were calculated to model signal intensity blurring on T1-MRI. Two observers assessed signal changes and atrophy visually. Compared to controls, TLE patients had a decrease in TPC and TPWM volume ipsilateral to the seizure focus. The gradient magnitude and entropy were decreased ipsilateral to the focus only in TPWM, indicating blurring of this compartment. Eighty-seven percent of TLE patients had at least one volumetric or textural abnormality. Although sensitivity of visual and quantitative assessment of TPC atrophy was comparable (43 and 39%), specificity was higher for volumetry (54% vs. 95%). Compared to visual analysis of signal changes in TPWM on T1-MRI, texture metrics had higher sensitivity (65% vs. 17%) and specificity (100% vs. 69%). The proportion of patients with blurring of TPWM as determined by texture analysis was higher than that seen on visual inspection of T2 images (78% vs. 43%). We found no clear association between volumetric or textural changes of TPC and TPWM and outcome after surgery. Structural changes of the anatomically distinct TPC and TPWM are found ipsilateral to the seizure focus in the majority of TLE patients with hippocampal sclerosis. MRI post-processing allows dissociating different pathological tissue characteristics and shows that atrophy involves gray and white matter, whereas blurring is confined to white matter.
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Affiliation(s)
- Tejas Sankar
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
- Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Neda Bernasconi
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
- Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Hosung Kim
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
- Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Andrea Bernasconi
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
- Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
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Proepileptic influence of a focal vascular lesion affecting entorhinal cortex-CA3 connections after status epilepticus. J Neuropathol Exp Neurol 2008; 67:687-701. [PMID: 18596544 DOI: 10.1097/nen.0b013e318181b8ae] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
In limbic seizures, neuronal excitation is conveyed from the entorhinal cortex directly to CA1 and subicular regions. This phenomenon is associated with a reduced ability of CA3 to respond to entorhinal cortex inputs. Here, we describe a lesion that destroys the perforant path in CA3 after status epilepticus (SE) induced by pilocarpine injection in 8-week-old rats. Using magnetic resonance imaging, immunohistochemical, and ultrastructural analyses, we determined that this lesion develops after 30 minutes of SE and is characterized by microhemorrhages and ischemia. After a longer period of SE, the lesion invariably involves the upper blade of the dentate gyrus. Adult rats treated with subcutaneous diazepam (20 mg kg for 3 days) did not develop the dentate gyrus lesion and had less frequent spontaneous recurrent seizures (p < 0.01). Young (3-week-old) rats rarely (20%) developed the CA3 lesion, and their spontaneous seizures were delayed (p < 0.01). To investigate the role of the damaged CA3 in seizure activity, we reinduced SE in adult and young epileptic rats. Using FosB/DeltaFosB markers, we found induction of FosB/DeltaFosB immunopositivity in CA3 neurons of young but not in adult rats. These experiments indicate that SE can produce a focal lesion in the perforant path that may affect the roles of the hippocampus in epileptic rats.
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36
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Zahn RK, Tolner EA, Derst C, Gruber C, Veh RW, Heinemann U. Reduced ictogenic potential of 4-aminopyridine in the perirhinal and entorhinal cortex of kainate-treated chronic epileptic rats. Neurobiol Dis 2008; 29:186-200. [DOI: 10.1016/j.nbd.2007.08.013] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2007] [Revised: 07/26/2007] [Accepted: 08/22/2007] [Indexed: 01/02/2023] Open
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de Guzman P, Inaba Y, Baldelli E, de Curtis M, Biagini G, Avoli M. Network hyperexcitability within the deep layers of the pilocarpine-treated rat entorhinal cortex. J Physiol 2008; 586:1867-83. [PMID: 18238812 DOI: 10.1113/jphysiol.2007.146159] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
In this study we report that in the presence of normal buffer, epileptiform discharges occur spontaneously (duration = 2.60 +/- 0.49 s) or can be induced by electrical stimuli (duration = 2.50 +/- 0.62 s) in the entorhinal cortex (EC) of brain slices obtained from pilocarpine-treated rats but not in those from age-matched, nonepileptic control (NEC) animals. These network-driven epileptiform events consist of field oscillatory sequences at frequencies greater than 200 Hz that most often initiate in the lateral EC and propagate to the medial EC with 4-63 ms delays. The NMDA receptor antagonist CPP depresses the rate of occurrence (P < 0.01) of these spontaneous epileptiform discharges but fails in blocking them. Paradoxically, stimulus-induced epileptiform responses are enhanced in duration during CPP application. However, concomitant application of NMDA and non-NMDA glutamatergic antagonists abolishes spontaneous and stimulus-induced epileptiform events. Intracellular recordings from lateral EC layer V cells indicate a lower frequency of spontaneous hyperpolarizing postsynaptic potentials in pilocarpine-treated tissue than in NEC (P < 0.002) both under control conditions and with glutamatergic receptor blockade; the reversal potential of pharmacologically isolated GABA(A) receptor-mediated inhibitory postsynaptic potentials has similar values in the two types of tissue. Finally, immunohistochemical analysis shows that parvalbumin-positive interneurons are selectively reduced in number in EC deep layers. Collectively, these results indicate that reduced inhibition within the pilocarpine-treated EC layer V may promote network epileptic hyperexcitability.
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Affiliation(s)
- Philip de Guzman
- Montreal Neurological Institute and Department of Neurology & Neurosurgery, McGill University, Montreal, QC H3A 2B4, Canada
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38
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Sudbury JR, Avoli M. Epileptiform synchronization in the rat insular and perirhinal cortices in vitro. Eur J Neurosci 2007; 26:3571-82. [PMID: 18052975 DOI: 10.1111/j.1460-9568.2007.05962.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The hippocampus plays a primary role in temporal lobe epilepsy, a common form of partial epilepsy in adults. Recent studies, however, indicate that extrahippocampal areas such as the perirhinal and insular cortices represent important participants in this epileptic disorder. By employing field potential recordings in the in vitro 4-aminopyridine model of temporal lobe epilepsy, we have investigated here the contribution of glutamatergic and GABAergic signaling to epileptiform activity in these structures. First, we provide evidence of epileptiform synchronicity between the perirhinal and insular cortices, and resolve some pharmacological and network mechanisms involved in sustaining the interictal- and ictal-like discharges recorded there. Second, we report that in the absence of ionotropic glutamatergic transmission, GABAergic networks produce synchronous potentials that spread between the perirhinal and insular cortices. Finally, we have established that such activity is modulated by activating micro-opioid receptors. Our findings support clinical and experimental evidence concerning the involvement of the perirhinal and insular cortex networks in temporal lobe epilepsy, and provide observations that may impact research focussing on the role of the insular cortex in nociception.
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Affiliation(s)
- Jessica R Sudbury
- Montreal Neurological Institute and Department of Neurology & Neurosurgery, McGill University, Montreal, H3A 2B4 QC, Canada
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39
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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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40
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Kopniczky Z, Dochnal R, Mácsai M, Pál A, Kiss G, Mihály A, Szabó G. Alterations of behavior and spatial learning after unilateral entorhinal ablation of rats. Life Sci 2006; 78:2683-8. [PMID: 16313927 DOI: 10.1016/j.lfs.2005.10.014] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2005] [Accepted: 10/21/2005] [Indexed: 11/26/2022]
Abstract
The entorhinal cortex (EC) is the key input and output structure of the hippocampus. It plays a crucial role in sensory processing, memory and learning, as well as in mechanisms of epileptic seizures. Our previous studies on the 4-aminopyridin induced epilepsy model of rats showed that ablation of unilateral EC prompted weakening of limbic seizure manifestation, thus the possibility of therapeutical benefit of this kind of surgery can be risen. Open field, elevated plus-maze and Morris water-maze test were performed to analyze changes of the basal activity level, exploratory behavior, and spatial memory capacity, respectively, of adult Wistar rats having undergone left EC excision. Compared with the sham-operated control group, rats with lesions of the EC showed enhanced locomotor activity in the open-field test. The elevated plus-maze test revealed higher frequency of entries and more time spent in the open arms. Morris water-maze test suggested impairment of the spatial learning capacity following left lateral EC lesion. Therefore, our data showed that EC lesions induced hyperactivity, increased exploratory behavior, and impaired spatial learning. Entorhinal cortex ablation, as a potential method for controlling epileptic seizures has multiple effects on animals' behavior and spatial learning. To determine the cost-benefit ratio of a potential surgical intervention needs further experimental and human investigations.
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Affiliation(s)
- Zsolt Kopniczky
- Department of Neurosurgery, Faculty of Medicine, University of Szeged, SZEGED 6725, Semmelweis u. 6., Hungary.
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41
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Biagini G, D'Arcangelo G, Baldelli E, D'Antuono M, Tancredi V, Avoli M. Impaired activation of CA3 pyramidal neurons in the epileptic hippocampus. Neuromolecular Med 2006; 7:325-42. [PMID: 16391389 DOI: 10.1385/nmm:7:4:325] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2005] [Revised: 09/06/2005] [Accepted: 09/28/2005] [Indexed: 11/11/2022]
Abstract
We employed in vitro and ex vivo imaging tools to characterize the function of limbic neuron networks in pilocarpine-treated and age-matched, nonepileptic control (NEC) rats. Pilocarpine-treated animals represent an established model of mesial temporal lobe epilepsy. Intrinsic optical signal (IOS) analysis of hippocampal-entorhinal cortex (EC) slices obtained from epileptic rats 3 wk after pilocarpine-induced status epilepticus (SE) revealed hyperexcitability in many limbic areas, but not in CA3 and medial EC layer III. By visualizing immunopositivity for FosB/DeltaFosB-related proteins which accumulate in the nuclei of neurons activated by seizures we found that: (1) 24 h after SE, FosB/DeltaFosB immunoreactivity was absent in medial EC layer III, but abundant in dentate gyrus, hippocampus proper (including CA3) and subiculum; (2) FosB/DeltaFosB levels progressively diminished 3 and 7 d after SE, whereas remaining elevated (p < 0.01) in subiculum; (3) FosB/DeltaFosB levels sharply increased 2 wk after SE (and remained elevated up to 3 wk) in dentate gyrus and in most of the other areas but not in CA3. A conspicuous neuronal damage was noticed in medial EC layer III, whereas hippocampus was more preserved. IOS analysis of the stimulus-induced responses in slices 3 wk after SE demonstrated that IOSs in CA3 were lower (p < 0.05) than in NEC slices following dentate gyrus stimulation, but not when stimuli were delivered in CA3. These findings indicate that CA3 networks are hypoactive in comparison with other epileptic limbic areas. We propose that this feature may affect the ability of hippocampal outputs to control epileptiform synchronization in EC.
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Affiliation(s)
- Giuseppe Biagini
- Dipartimento di Scienze Biomediche, Università di Modena e Reggio Emilia, 41100 Modena, Italy
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42
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de Guzman P, Inaba Y, Biagini G, Baldelli E, Mollinari C, Merlo D, Avoli M. Subiculum network excitability is increased in a rodent model of temporal lobe epilepsy. Hippocampus 2006; 16:843-60. [PMID: 16897722 DOI: 10.1002/hipo.20215] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In this study, we used in vitro electrophysiology along with immunohistochemistry and molecular techniques to study the subiculum--a limbic structure that gates the information flow from and to the hippocampus--in pilocarpine-treated epileptic rats. Comparative data were obtained from age-matched nonepileptic controls (NEC). Subicular neurons in hippocampal-entorhinal cortex (EC) slices of epileptic rats were: (i) hyperexcitable when activated by CA1 or EC inputs; and (ii) generated spontaneous postsynaptic potentials at higher frequencies than NEC cells. Analysis of pharmacologically isolated, GABA(A) receptor-mediated inhibitory postsynaptic potentials revealed more positive reversal potentials in epileptic tissue (-67.8 +/- 6.3 mV, n = 16 vs. -74.8 +/- 3.6 mV in NEC, n = 13; P < 0.001) combined with a reduction in peak conductance (17.6 +/- 11.3 nS vs. 41.1 +/- 26.7 nS in NEC; P < 0.003). These electrophysiological data correlated in the epileptic subiculum with (i) reduced levels of mRNA expression and immunoreactivity of the neuron-specific potassium-chloride cotransporter 2; (ii) decreased number of parvalbumin-positive cells; and (iii) increased synaptophysin (a putative marker of sprouting) immunoreactivity. These findings identify an increase in network excitability within the subiculum of pilocarpine-treated, epileptic rats and point at a reduction in inhibition as an underlying mechanism.
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Affiliation(s)
- Philip de Guzman
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
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Kopniczky Z, Dobó E, Borbély S, Világi I, Détári L, Krisztin-Péva B, Bagosi A, Molnár E, Mihály A. Lateral entorhinal cortex lesions rearrange afferents, glutamate receptors, increase seizure latency and suppress seizure-induced c-fos expression in the hippocampus of adult rat. J Neurochem 2005; 95:111-24. [PMID: 16181416 DOI: 10.1111/j.1471-4159.2005.03347.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The entorhinal cortex (EC) provides the predominant excitatory drive to the hippocampal CA1 and subicular neurones in chronic epilepsy. Here we analysed the effects of one-sided lateral EC (LEC) and temporoammonic (alvear) path lesion on the development and properties of 4-aminopyridine-induced seizures. Electroencephalography (EEG) analysis of freely moving rats identified that the lesion increased the latency of the hippocampal seizure significantly and decreased the number of brief convulsions. Seizure-induced neuronal c-fos expression was reduced in every hippocampal area following LEC lesion. Immunocytochemical analysis 40 days after the ablation of the LEC identified sprouting of cholinergic and calretinin-containing axons into the dentate molecular layer. Region and subunit specific changes in the expression of ionotropic glutamate receptors (iGluRs) were identified. Although the total amount of AMPA receptor subunits remained unchanged, GluR1(flop) displayed a significant decrease in the CA1 region. An increase in NR1 and NR2B N-methyl-d-aspartate (NMDA) receptor subunits and KA-2 kainate receptor subunit was identified in the deafferented layers of the hippocampus. These results further emphasize the importance of the lateral entorhinal area in the spread and regulation of hippocampal seizures and highlight the potential role of the rewiring of afferents and rearrangement of iGluRs in the dentate gyrus in hippocampal convulsive activity.
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Affiliation(s)
- Zsolt Kopniczky
- Department of Neurosurgery, Faculty of Medicine, University of Szeged, Szeged, Hungary
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Wozny C, Gabriel S, Jandova K, Schulze K, Heinemann U, Behr J. Entorhinal cortex entrains epileptiform activity in CA1 in pilocarpine-treated rats. Neurobiol Dis 2005; 19:451-60. [PMID: 16023587 DOI: 10.1016/j.nbd.2005.01.016] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2003] [Revised: 06/16/2004] [Accepted: 01/12/2005] [Indexed: 10/25/2022] Open
Abstract
Layer III neurons of the medial entorhinal cortex (mEC) project to CA1 via the temporoammonic pathway and exert a powerful feed-forward inhibition of CA1 pyramidal neurons. The present study evaluates the hypothesis that disrupted inhibition of CA1 pyramidal neurons causes an eased propagation of entorhinal seizures to the hippocampus via the temporoammonic pathway. Using a method to induce a confined epileptic focus in brain slices, we investigated the spread of epileptiform activity from the disinhibited mEC to CA1 in control and pilocarpine-treated rats that had displayed status epilepticus and spontaneous recurrent seizures. In pilocarpine-treated rats, the mEC showed a moderate layer III cell loss and an enhanced susceptibility to epileptiform discharges compared to control animals. Entorhinal discharges propagated to CA1 in pilocarpine-treated rats but not in controls. Disconnecting CA3 from CA1 did not affect the spread of epileptiform activity to CA1 excluding its propagation via the trisynaptic hippocampal loop. Mimicking the invasion of epileptiform discharges by repetitive stimulation of the temporoammonic pathway caused a facilitation of field potentials in CA1 that were contaminated by population spikes and afterdischarges in pilocarpine-treated but not control rats. Single cell recordings of CA1 pyramidal neurons revealed a dramatic loss of feed-forward inhibition and the occurrence of strong postsynaptic excitatory potentials in pilocarpine-treated rats. Excitatory responses in CA1 were characterized by multiple NMDA receptor-mediated afterdischarges and a strong paired-pulse facilitation in response to activation of the temporoammonic pathway. Our results suggest that, irrespective of the enhanced seizure-susceptibility of the mEC in epileptic rats, the loss of feed-forward inhibition and the enhanced NMDA receptor-mediated excitability CA1 pyramidal cells ease the spread of epileptiform activity from the mEC to CA1 via the temporoammonic pathway bypassing the classical trisynaptic hippocampal loop.
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Affiliation(s)
- C Wozny
- Neuroscience Research Center of the Charité, Humboldt University Berlin, Schumannstr. 20/21, 10117 Berlin, Germany
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Weissinger F, Buchheim K, Siegmund H, Meierkord H. Seizure spread through the life cycle: optical imaging in combined brain slices from immature, adult, and senile rats in vitro. Neurobiol Dis 2005; 19:84-95. [PMID: 15837564 DOI: 10.1016/j.nbd.2004.11.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2004] [Revised: 11/15/2004] [Accepted: 11/18/2004] [Indexed: 11/19/2022] Open
Abstract
The semiology of epileptic seizures changes during the lifetime. Hence, it can be assumed that age-related changes in brain plasticity influence the patterns of seizure onset, spread and propagation velocity. We employed the 4-aminopyridine model of epilepsy to study seizure-like events in vitro. Combined entorhinal cortex-hippocampus brain slices from juvenile (10-13 days), adult (2-3 months), and senile (24-27 months) rats were examined using electrophysiological recordings and imaging of intrinsic optical signals. In the juvenile group, seizure onset was multifocal in all slice regions including the hippocampus. Onset in adult animals was confined to the entorhinal cortex and to neocortical regions. In slices from senile animals, there was a preponderance of seizure onsets in the neocortex. Spread patterns were highly variable in the juvenile group and became gradually more monomorph with increasing age. Propagation velocities were highest in the adult group, with maximum values of 1.51 +/- 0.68 mm/s. In the juvenile group, they amounted to 0.97 +/- 0.39 mm/s, and to 1.18 +/- 0.42 mm/s in senile slices. The results of this study indicate that age-related changes in brain plasticity profoundly affect spread patterns, which may contribute to the clinically observed changes in seizure semiology during early childhood, adulthood and senescence.
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Affiliation(s)
- Florian Weissinger
- Department of Neurology, Charité--Universitary Medicine Berlin, Humboldt-University Berlin, Schumannstr. 20/21, D-10117 Berlin, Germany.
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Benini R, Avoli M. Rat subicular networks gate hippocampal output activity in an in vitro model of limbic seizures. J Physiol 2005; 566:885-900. [PMID: 15932889 PMCID: PMC1464785 DOI: 10.1113/jphysiol.2005.088708] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Evidence obtained from human epileptic tissue maintained in vitro indicates that the subiculum may play a crucial role in initiating epileptiform discharges in patients with mesial temporal lobe epilepsy. Hence, we used rat hippocampus-entorhinal cortex (EC) slices to identify the role of subiculum in epileptiform synchronization during bath application of 4-aminopyridine (4AP, 50 microM). In these slices, fast CA3-driven interictal-like events were restricted to the hippocampal CA3/CA1 areas and failed to propagate to the EC where slow interictal-like and ictal-like epileptiform discharges were recorded. However, antagonizing GABA(A) receptors with picrotoxin (50 microM) made CA3-driven interictal activity spread to EC. Sequential field potential analysis along the CA3-CA1-subiculum axis revealed that the amplitude of CA3-driven interictal discharges recorded in the presence of 4AP only diminished within the subiculum. Furthermore, CA1 electrical stimulation under control conditions elicited little or no subicular activation and never any response in EC; in contrast, robust subicular discharges that spread to EC could be evoked after picrotoxin. Intracellular recordings indicated that potentiation by picrotoxin was associated with blockade of hyperpolarizing IPSPs in subicular cells. Finally, when surgically isolated from adjacent structures, the subiculum generated low-amplitude synchronous discharges that corresponded to an intracellular hyperpolarization-depolarization sequence, were resistant to glutamatergic antagonists, and represented the activity of synchronized interneuronal networks. Bath application of picrotoxin abolished these 4AP-induced events and in their place robust network bursting occurred. In conclusion, our study demonstrates that the subiculum plays a powerful gating role on hippocampal output activity. This function depends on GABA(A) receptor-mediated inhibition and controls hippocampal-parahippocampal interactions that are known to modulate limbic seizures.
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Affiliation(s)
- Ruba Benini
- Montreal Neurological Institute and Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada
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Vreugdenhil M, Hoogland G, van Veelen CWM, Wadman WJ. Persistent sodium current in subicular neurons isolated from patients with temporal lobe epilepsy. Eur J Neurosci 2004; 19:2769-78. [PMID: 15147310 DOI: 10.1111/j.1460-9568.2004.03400.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The persistent sodium current is a common target of anti-epileptic drugs and contributes to burst firing. Intrinsically burst firing subicular neurons are involved in the generation and spread of epileptic activity. We measured whole-cell sodium currents in pyramidal neurons isolated from the subiculum resected in drug-resistant epileptic patients and in rats. In half of the cells from both patients and rats, the sodium current inactivated within 500 ms at -30 mV. Others displayed a tetrodotoxin-sensitive slowly or non-inactivating sodium current of up to 53% of the total sodium current amplitude. Compared with the transient sodium current in the same cells, this persistent sodium current activated with normal kinetics but its voltage-dependent activation occurred 7 mV more hyperpolarized. Depolarizing voltage steps that lasted 10 s completely inactivated the persistent sodium current. Its voltage dependence did not differ from that of the transient sodium current but its slope was less steep. The voltage dependence and kinetics of the persistent sodium current in cells from patients were not different from that in subicular cells from rats. The current density and the relative amplitude contribution were 3-4 times greater in neurons from drug-resistant epilepsy patients. The abundant presence of persistent sodium current in half of the subicular neurons could lead to a larger number of neurons with intrinsic burst firing. The extraordinarily large amplitude of the persistent sodium current in this subset of subicular neurons might explain why these patients are susceptible to seizures and hard to treat pharmacologically.
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Affiliation(s)
- Martin Vreugdenhil
- Swammerdam Institute for Life Sciences, University of Amsterdam, Kruislaan 320, 1098 SM, Amsterdam, The Netherlands.
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Niittykoski M, Nissinen J, Penttonen M, Pitkänen A. Electrophysiologic changes in the lateral and basal amygdaloid nuclei in temporal lobe epilepsy: an in vitro study in epileptic rats. Neuroscience 2004; 124:269-81. [PMID: 14980378 DOI: 10.1016/j.neuroscience.2003.11.027] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/21/2003] [Indexed: 10/26/2022]
Abstract
The functional consequences of neuronal loss during epileptogenesis in the lateral and basal amygdaloid nuclei are poorly understood. The present study tested the hypothesis that electrical responsiveness varies in different amygdaloid nuclei in the chronically epileptic amygdala. Further, we examined the amygdaloid region most prone to seizure initiation. Epileptogenesis was triggered in 20 rats by inducing status epilepticus (SE) with electrical stimulation of the lateral nucleus of the amygdala. Electrode-implanted non-stimulated rats served as controls. The occurrence and duration of spontaneous seizures were monitored with video-electroencephalography (EEG) at 8-9 weeks after SE. Thereafter, animals were killed and extracellular recordings were made from slices of both amygdalas. In the lateral nucleus of epileptic animals, the frequency of spontaneous responses was reduced compared with controls (P < 0.05). The amplitudes of evoked field responses were reduced (P < 0.01), whereas paired pulse (PP) facilitation was enhanced (P < or = 0.05). In the basal nucleus of the epileptic animals, PP facilitation was enhanced (P < 0.05) and sensitivity to 4-aminopyridine (4-AP)-induced epileptiform activity was increased compared with controls (P < 0.05). In the epileptic animals, the basal nucleus was also more sensitive than the lateral nucleus to 4-AP-induced epileptiform activity (P < 0.05). Correlation analysis indicated that longer SE duration was associated with longer half widths (P = 0.001) and smaller slopes (P < 0.05) of evoked responses as well as with attenuated PP facilitation (P<0.01). Moreover, a higher frequency of spontaneous seizures was associated with longer half widths (P < 0.05) and smaller slopes (P < 0.05) of evoked responses as well as with enhanced PP facilitation (P < 0.05). These data suggest that there is a reduced release of glutamate and reduced inhibition in the lateral and basal amygdaloid nuclei in epileptic animals. Further, the basal nucleus is more prone to epileptic activity than the lateral nucleus. Finally, the severity of SE and spontaneous seizures in vivo is associated with electrophysiologic alterations in vitro.
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Affiliation(s)
- M Niittykoski
- Epilepsy Research Laboratory, Department of Neurobiology, A.I. Virtanen Institute for Molecular Sciences, University of Kuopio, P.O. Box 1627, FIN-70211 Kuopio, Finland
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de Guzman P, D'Antuono M, Avoli M. Initiation of electrographic seizures by neuronal networks in entorhinal and perirhinal cortices in vitro. Neuroscience 2004; 123:875-86. [PMID: 14751281 DOI: 10.1016/j.neuroscience.2003.11.013] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The hippocampus is often considered to play a major role in the pathophysiology of mesial temporal lobe epilepsy. However, emerging clinical and experimental evidence suggests that parahippocampal areas may contribute to a greater extent to limbic seizure initiation, and perhaps epileptogenesis. To date, little is known about the participation of entorhinal and perirhinal networks to epileptiform synchronization. Here, we addressed this issue by using simultaneous field potential recordings in horizontal rat brain slices containing interconnected limbic structures that included the hippocampus proper. Epileptiform discharges were disclosed by bath applying the convulsant drug 4-aminopyridine (50 microM) or by superfusing Mg(2+)-free medium. In the presence of 4-aminopyridine, slow interictal- (duration=2.34+/-0.29 s; interval of occurrence=25.75+/-2.11 s, n=16) and ictal-like (duration=31.25+/-3.34 s; interval of occurrence=196.96+/-21.56 s, n=17) discharges were recorded in entorhinal and perirhinal cortices after abating the propagation of CA3-driven interictal activity to these areas following extended hippocampal knife cuts. Simultaneous recordings obtained from the medial and lateral entorhinal cortex, and from the perirhinal cortex revealed that interictal and ictal discharges could initiate from any of these areas and propagate to the neighboring structure with delays of 8-66 ms. However, slow interictal- and ictal-like events more often originated in the medial entorhinal cortex and perirhinal cortex, respectively. Cutting the connections between entorhinal and perirhinal cortices (n=10), or functional inactivation of cortical areas by local application of a glutamatergic receptor antagonist (n=11) made independent epileptiform activity occur in all areas. These procedures also shortened ictal discharge duration in the entorhinal cortices, but not in the perirhinal area. Similar results could be obtained by applying Mg(2+)-free medium (n=7). These findings indicate that parahippocampal networks provide independent epileptiform synchronization sufficient to sustain limbic seizures as well as that the perirhinal cortex plays a preferential role in in vitro ictogenesis.
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Affiliation(s)
- P de Guzman
- Montreal Neurological Institute and Departments of Neurology and Neurosurgery and of Physiology, McGill University, Montreal, QC, H3A 2B4, Canada
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Avoli M, Benini R, de Guzman P, Omar A. GABA(B) receptor activation and limbic network ictogenesis. Neuropharmacology 2004; 46:43-51. [PMID: 14654096 DOI: 10.1016/s0028-3908(03)00307-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Rat brain slices containing interconnected hippocampus and entorhinal cortex (EC) responded to 4-aminopyridine (50 microM) application by generating: (i) CA3-driven interictal discharges that propagated to the EC; and (ii) N-methyl-D-aspartic (NMDA) acid receptor-dependent ictal events originating in EC (cf. J. Neurosci. 17 (1997) 9308 for experiments made in brain slices). Ictal discharges disappeared within 1-2 h, but were re-established by cutting the Schaffer collaterals, which abolished CA3-driven interictal discharge propagation to EC. In intact slices, GABA(B) receptor activation by baclofen (5-40 microM): (i) depressed CA3-driven interictal activity; and (ii) disclosed non-NMDA glutamatergic receptor-dependent ictal discharges originating in CA3 and propagating to EC. These effects were reversed by the GABA(B) receptor antagonist CGP 35348 (0.5 mM). Application of increasing baclofen doses to slices in which hippocampus and EC networks were surgically isolated decreased epileptiform events with an IC50 that was lower in EC (0.6 microM; n = 12) than in CA3 (2.5 microM; n = 12). Hence, under control conditions, EC ictogenesis depends on NMDA receptor function and is controlled by CA3-driven output activity; in contrast, following GABA(B) receptor activation EC excitability is depressed to a greater extent than CA3, which leads to non-NMDA glutamatergic receptor-mediated ictogenesis in CA3. We propose that GABA(B) receptor modulation may represent an important mechanism for setting the site of initiation, the modalities of propagation and the glutamatergic receptor properties of ictogenesis in the limbic system and, perhaps, in mesial temporal lobe epilepsy patients.
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Affiliation(s)
- Massimo Avoli
- Departments of Neurology and Neurosurgery, and of Physiology, Montreal Neurological Institute, McGill University, Montreal, QC, Canada H3A 2B4.
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