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McCoy AM, Prevot TD, Sharmin D, Cook JM, Sibille EL, Lodge DJ. GL-II-73, a Positive Allosteric Modulator of α5GABA A Receptors, Reverses Dopamine System Dysfunction Associated with Pilocarpine-Induced Temporal Lobe Epilepsy. Int J Mol Sci 2023; 24:11588. [PMID: 37511346 PMCID: PMC10380722 DOI: 10.3390/ijms241411588] [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: 06/25/2023] [Revised: 07/15/2023] [Accepted: 07/16/2023] [Indexed: 07/30/2023] Open
Abstract
Although seizures are a hallmark feature of temporal lobe epilepsy (TLE), psychiatric comorbidities, including psychosis, are frequently associated with TLE and contribute to decreased quality of life. Currently, there are no defined therapeutic protocols to manage psychosis in TLE patients, as antipsychotic agents may induce epileptic seizures and are associated with severe side effects and pharmacokinetic and pharmacodynamic interactions with antiepileptic drugs. Thus, novel treatment strategies are necessary. Several lines of evidence suggest that hippocampal hyperactivity is central to the pathology of both TLE and psychosis; therefore, restoring hippocampal activity back to normal levels may be a novel therapeutic approach for treating psychosis in TLE. In rodent models, increased activity in the ventral hippocampus (vHipp) results in aberrant dopamine system function, which is thought to underlie symptoms of psychosis. Indeed, we have previously demonstrated that targeting α5-containing γ-aminobutyric acid receptors (α5GABAARs), an inhibitory receptor abundant in the hippocampus, with positive allosteric modulators (PAMs), can restore dopamine system function in rodent models displaying hippocampal hyperactivity. Thus, we posited that α5-PAMs may be beneficial in a model used to study TLE. Here, we demonstrate that pilocarpine-induced TLE is associated with increased VTA dopamine neuron activity, an effect that was completely reversed by intra-vHipp administration of GL-II-73, a selective α5-PAM. Further, pilocarpine did not alter the hippocampal α5GABAAR expression or synaptic localization that may affect the efficacy of α5-PAMs. Taken together, these results suggest augmenting α5GABAAR function as a novel therapeutic modality for the treatment of psychosis in TLE.
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Affiliation(s)
- Alexandra M McCoy
- Department of Pharmacology and Center for Biomedical Neuroscience, UT Health San Antonio, San Antonio, TX 78229, USA
- South Texas Veterans Health Care System, Audie L. Murphy Division, San Antonio, TX 78229, USA
| | - Thomas D Prevot
- Campbell Family Mental Health Research Institute of CAMH, Toronto, ON M5S 2S1, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON M5T 1R8, Canada
| | - Dishary Sharmin
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, USA
| | - James M Cook
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, USA
| | - Etienne L Sibille
- Campbell Family Mental Health Research Institute of CAMH, Toronto, ON M5S 2S1, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON M5T 1R8, Canada
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON M5T 1R8, Canada
| | - Daniel J Lodge
- Department of Pharmacology and Center for Biomedical Neuroscience, UT Health San Antonio, San Antonio, TX 78229, USA
- South Texas Veterans Health Care System, Audie L. Murphy Division, San Antonio, TX 78229, USA
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Avoli M, de Curtis M, Lévesque M, Librizzi L, Uva L, Wang S. GABAA signaling, focal epileptiform synchronization and epileptogenesis. Front Neural Circuits 2022; 16:984802. [PMID: 36275847 PMCID: PMC9581276 DOI: 10.3389/fncir.2022.984802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Accepted: 09/13/2022] [Indexed: 12/04/2022] Open
Abstract
Under physiological conditions, neuronal network synchronization leads to different oscillatory EEG patterns that are associated with specific behavioral and cognitive functions. Excessive synchronization can, however, lead to focal or generalized epileptiform activities. It is indeed well established that in both epileptic patients and animal models, focal epileptiform EEG patterns are characterized by interictal and ictal (seizure) discharges. Over the last three decades, employing in vitro and in vivo recording techniques, several experimental studies have firmly identified a paradoxical role of GABAA signaling in generating interictal discharges, and in initiating—and perhaps sustaining—focal seizures. Here, we will review these experiments and we will extend our appraisal to evidence suggesting that GABAA signaling may also contribute to epileptogenesis, i.e., the development of plastic changes in brain excitability that leads to the chronic epileptic condition. Overall, we anticipate that this information should provide the rationale for developing new specific pharmacological treatments for patients presenting with focal epileptic disorders such as mesial temporal lobe epilepsy (MTLE).
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Affiliation(s)
- Massimo Avoli
- Montreal Neurological Institute-Hospital, Montreal, QC, Canada
- Departments of Neurology and Neurosurgery, Montreal, QC, Canada
- Department of Physiology, McGill University, Montreal, QC, Canada
- *Correspondence: Massimo Avoli,
| | - Marco de Curtis
- Epilepsy Unit, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Istituto Neurologico Carlo Besta, Milan, Italy
| | - Maxime Lévesque
- Montreal Neurological Institute-Hospital, Montreal, QC, Canada
- Departments of Neurology and Neurosurgery, Montreal, QC, Canada
| | - Laura Librizzi
- Epilepsy Unit, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Istituto Neurologico Carlo Besta, Milan, Italy
| | - Laura Uva
- Epilepsy Unit, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Istituto Neurologico Carlo Besta, Milan, Italy
| | - Siyan Wang
- Montreal Neurological Institute-Hospital, Montreal, QC, Canada
- Departments of Neurology and Neurosurgery, Montreal, QC, Canada
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3
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Sun Y, Peng Z, Wei X, Zhang N, Huang CS, Wallner M, Mody I, Houser CR. Virally-induced expression of GABAA receptor δ subunits following their pathological loss reveals their role in regulating GABAA receptor assembly. Prog Neurobiol 2022; 218:102337. [PMID: 35934131 PMCID: PMC10091858 DOI: 10.1016/j.pneurobio.2022.102337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 07/26/2022] [Accepted: 08/03/2022] [Indexed: 10/31/2022]
Abstract
Decreased expression of the δ subunit of the GABAA receptor (GABAAR) has been found in the dentate gyrus in several animal models of epilepsy and other disorders with increased excitability and is associated with altered modulation of tonic inhibition in dentate granule cells (GCs). In contrast, other GABAAR subunits, including α4 and γ2 subunits, are increased, but the relationship between these changes is unclear. The goals of this study were to determine if viral transfection of δ subunits in dentate GCs could increase δ subunit expression, alter expression of potentially-related GABAAR subunits, and restore more normal network excitability in the dentate gyrus in a mouse model of epilepsy. Pilocarpine-induced seizures were elicited in DOCK10-Cre mice that express Cre selectively in dentate GCs, and two weeks later the mice were injected unilaterally with a Cre-dependent δ-GABAAR viral vector. At 4-6 weeks following transfection, δ subunit immunolabeling was substantially increased in dentate GCs on the transfected side compared to the nontransfected side. Importantly, α4 and γ2 subunit labeling was downregulated on the transfected side. Electrophysiological studies revealed enhanced tonic inhibition, decreased network excitability, and increased neurosteroid sensitivity in slices from the δ subunit-transfected side compared to those from the nontransfected side of the same pilocarpine-treated animal, consistent with the formation of δ subunit-containing GABAARs. No differences were observed between sides of eYFP-transfected animals. These findings are consistent with the idea that altering expression of key subunits, such as the δ subunit, regulates GABAAR subunit assemblies, resulting in substantial effects on network excitability.
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Tipton AE, Russek SJ. Regulation of Inhibitory Signaling at the Receptor and Cellular Level; Advances in Our Understanding of GABAergic Neurotransmission and the Mechanisms by Which It Is Disrupted in Epilepsy. Front Synaptic Neurosci 2022; 14:914374. [PMID: 35874848 PMCID: PMC9302637 DOI: 10.3389/fnsyn.2022.914374] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 05/17/2022] [Indexed: 11/13/2022] Open
Abstract
Inhibitory signaling in the brain organizes the neural circuits that orchestrate how living creatures interact with the world around them and how they build representations of objects and ideas. Without tight control at multiple points of cellular engagement, the brain’s inhibitory systems would run down and the ability to extract meaningful information from excitatory events would be lost leaving behind a system vulnerable to seizures and to cognitive decline. In this review, we will cover many of the salient features that have emerged regarding the dynamic regulation of inhibitory signaling seen through the lens of cell biology with an emphasis on the major building blocks, the ligand-gated ion channel receptors that are the first transduction point when the neurotransmitter GABA is released into the synapse. Epilepsy association will be used to indicate importance of key proteins and their pathways to brain function and to introduce novel areas for therapeutic intervention.
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Affiliation(s)
- Allison E. Tipton
- Graduate Program for Neuroscience, Boston University, Boston, MA, United States
- Biomolecular Pharmacology Program, Boston University School of Medicine, Boston, MA, United States
- Boston University MD/PhD Training Program, Boston, MA, United States
| | - Shelley J. Russek
- Biomolecular Pharmacology Program, Boston University School of Medicine, Boston, MA, United States
- Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA, United States
- Center for Systems Neuroscience, Boston University, Boston, MA, United States
- Boston University MD/PhD Training Program, Boston, MA, United States
- *Correspondence: Shelley J. Russek,
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GABA A Receptor-Stabilizing Protein Ubqln1 Affects Hyperexcitability and Epileptogenesis after Traumatic Brain Injury and in a Model of In Vitro Epilepsy in Mice. Int J Mol Sci 2022; 23:ijms23073902. [PMID: 35409261 PMCID: PMC8999075 DOI: 10.3390/ijms23073902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 03/23/2022] [Accepted: 03/30/2022] [Indexed: 11/16/2022] Open
Abstract
Posttraumatic epilepsy (PTE) is a major public health concern and strongly contributes to human epilepsy cases worldwide. However, an effective treatment and prevention remains a matter of intense research. The present study provides new insights into the gamma aminobutyric acid A (GABAA)-stabilizing protein ubiquilin-1 (ubqln1) and its regulation in mouse models of traumatic brain injury (TBI) and in vitro epilepsy. We performed label-free quantification on isolated cortical GABAergic interneurons from GAD67-GFP mice that received unilateral TBI and discovered reduced expression of ubqln1 24 h post-TBI. To investigate the link between this regulation and the development of epileptiform activity, we further studied ubqln1 expression in hippocampal and cortical slices. Epileptiform events were evoked pharmacologically in acute brain slices by administration of picrotoxin (PTX, 50 μM) and kainic acid (KA, 500 nM) and recorded in the hippocampal CA1 subfield using Multi-electrode Arrays (MEA). Interestingly, quantitative Western blots revealed significant decreases in ubqln1 expression 1–7 h after seizure induction that could be restored by application of the non-selective monoamine oxidase inhibitor nialamide (NM, 10 μM). In picrotoxin-dependent dose–response relationships, NM administration alleviated the frequency and peak amplitude of seizure-like events (SLEs). These findings indicate a role of the monoamine transmitter systems and ubqln1 for cortical network activity during posttraumatic epileptogenesis.
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Sperk G, Pirker S, Gasser E, Wieselthaler A, Bukovac A, Kuchukhidze G, Maier H, Drexel M, Baumgartner C, Ortler M, Czech T. Increased expression of GABA A receptor subunits associated with tonic inhibition in patients with temporal lobe epilepsy. Brain Commun 2021; 3:fcab239. [PMID: 34708207 PMCID: PMC8545616 DOI: 10.1093/braincomms/fcab239] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 08/07/2021] [Accepted: 08/26/2021] [Indexed: 11/30/2022] Open
Abstract
Epilepsy animal models indicate pronounced changes in the expression and rearrangement of GABAA receptor subunits in the hippocampus and in para-hippocampal areas, including widespread downregulation of the subunits α5 and δ, and upregulation of α4, subunits that mediate tonic inhibition of GABA. In this case–control study, we investigated changes in the expression of subunits α4, α5 and δ in hippocampal specimens of drug resistant temporal lobe epilepsy patients who underwent epilepsy surgery. Using in situ hybridization, immunohistochemistry and α5-specific receptor autoradiography, we characterized expression of the receptor subunits in specimens from patients with and without Ammon’s horn sclerosis compared to post-mortem controls. Expression of the α5-subunit was abundant throughout all subfields of the hippocampus, including the dentate gyrus, sectors CA1 and CA3, the subiculum and pre- and parasubiculum. Significant but weaker expression was detected for subunits α4 and δ notably in the granule cell/molecular layer of control specimens, but was faint in the other parts of the hippocampus. Expression of all three subunits was similarly altered in sclerotic and non-sclerotic specimens. Respective mRNA levels were increased by about 50–80% in the granule cell layer compared with post-mortem controls. Subunit α5 mRNA levels and immunoreactivities were also increased in the sector CA3 and in the subiculum. Autoradiography for α5-containing receptors using [3H]L-655,708 as ligand showed significantly increased binding in the molecular layer of the dentate gyrus in non-sclerotic specimens. Increased expression of the α5 and δ subunits is in contrast to the previously observed downregulation of these subunits in different epilepsy models, whereas increased expression of α4 in temporal lobe epilepsy patients is consistent with that in the rodent models. Our findings indicate increased tonic inhibition likely representing an endogenous anticonvulsive mechanism in temporal lobe epilepsy.
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Affiliation(s)
- Günther Sperk
- Department of Pharmacology, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - Susanne Pirker
- Neurological Department, Klinik Hietzing, 1130 Vienna, Austria
| | - Elisabeth Gasser
- Department of Pharmacology, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - Anna Wieselthaler
- Department of Pharmacology, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - Anneliese Bukovac
- Department of Pharmacology, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - Giorgi Kuchukhidze
- Department of Neurology, Christian Doppler Klinik, Affiliated Member of the European Reference Network EpiCARE and Centre for Cognitive Neuroscience, Paracelsus Medical University of Salzburg, 5020 Salzburg, Austria.,Neuroscience Institute, Christian Doppler Klinik, 5020 Salzburg, Austria
| | - Hans Maier
- INNPATH GmbH-Institute of Pathology, 6020 Innsbruck, Austria
| | - Meinrad Drexel
- Department of Pharmacology, Medical University of Innsbruck, 6020 Innsbruck, Austria.,Institute of Molecular and Cellular Pharmacology, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | | | - Marin Ortler
- Department of Neurosurgery, Klinik Landstrasse, Vienna Healthcare Network, 1030Vienna, Austria.,Department of Neurosurgery, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - Thomas Czech
- Department of Neurosurgery, Medical University Vienna, 1090 Vienna, Austria
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Characterization of metabolic activity induced by kainic acid in adult rat whole brain at the early stage: A 18FDG-PET study. Brain Res 2021; 1769:147621. [PMID: 34403661 DOI: 10.1016/j.brainres.2021.147621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 07/08/2021] [Accepted: 08/10/2021] [Indexed: 11/23/2022]
Abstract
OBJECTIVE Brain metabolic processes are not fully characterized in the kainic acid (KA)-induced Status Epilepticus (KASE). Thus, we evaluated the usefulness of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) as an experimental strategy to evaluate in vivo, in a non-invasive way, the glucose consumption in several brain regions, in a semi-quantitative study to compare and to correlate with data from electroencephalography and histology studies. METHODS Sixteen male Wistar rats underwent FDG-PET scans at basal state and after KA injection. FDG-PET images were normalized to an MRI-based atlas and segmented to locate regions. Standardized uptake values (SUV) were obtained at several time points. EEGs and cell viability by histological analysis, were also evaluated. RESULTS FDG-PET data showed changes in regions such as: amygdala, hippocampus, accumbens, entorhinal cortex, motor cortex and hypothalamus. Remarkably, hippocampal hypermetabolism was found (mean SUV = 2.66 ± 0.057) 2 h after KA administration, while hypometabolism at 24 h (mean SUV = 1.83 ± 0.056) vs basal values (mean SUV = 2.19 ± 0.057). EEG showed increased spectral power values 2 h post-KA administration. Hippocampal viable-cell counting 24 h after KA was decreased, while Fluoro-Jade B-positive cells were increased, as compared to control rats, coinciding with the hypometabolism detected in the same region by semi-quantitative FDG-PET at 24 h after KASE. CONCLUSIONS PET is suitable to measure metabolic brain changes in the rat model of status epilepticus induced by KA (KASE) at the first 24 h, compared to that of EEG; PET data may also be sensitive to cell viability.
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Pérez-Pérez D, Frías-Soria CL, Rocha L. Drug-resistant epilepsy: From multiple hypotheses to an integral explanation using preclinical resources. Epilepsy Behav 2021; 121:106430. [PMID: 31378558 DOI: 10.1016/j.yebeh.2019.07.031] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 06/12/2019] [Accepted: 07/06/2019] [Indexed: 01/07/2023]
Abstract
Drug-resistant epilepsy affects approximately one-third of the patients with epilepsy. The pharmacoresistant condition in epilepsy is mainly explained by six hypotheses. In addition, several experimental models have been used to understand the mechanisms involved in pharmacoresistant epilepsy and to identify novel therapies to control this condition. However, the global prevalence of this disease persists without changes. Several factors can explain this situation. First of all, the pharmacoresistant epilepsy is explained by different and independent hypotheses. Each hypothesis indicates specific mechanisms to explain the drug-resistant condition in epilepsy. However, there are different findings suggesting common mechanisms between the different hypotheses. Other important situation is that the experimental models designed for the screening of drugs with potential anticonvulsant effect do not consider factors such as age, gender, type of epilepsy, and comorbid disorders. The present review focuses on indicating the limitations for each hypothesis and the relationships among them. The relevance to consider central and peripheral phenomena associated with the drug-resistant condition in different types of epilepsy is also indicated. The necessity to establish a global hypothesis that integrates all the phenomena associated with the pharmacoresistant epilepsy is proposed. This article is part of the Special Issue "NEWroscience 2018".
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Affiliation(s)
- Daniel Pérez-Pérez
- PECEM (MD/PhD), Faculty of Medicine, National Autonomous University of Mexico, Mexico City, Mexico
| | | | - Luisa Rocha
- Pharmacobiology Department, Center of Research and Advanced Studies, Mexico City, Mexico.
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Roynard P, Bilderback A, Dewey CW. Intravenous Ketamine Bolus(es) for the Treatment of Status Epilepticus, Refractory Status Epilepticus, and Cluster Seizures: A Retrospective Study of 15 Dogs. Front Vet Sci 2021; 8:547279. [PMID: 33681317 PMCID: PMC7925624 DOI: 10.3389/fvets.2021.547279] [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: 03/31/2020] [Accepted: 01/07/2021] [Indexed: 12/02/2022] Open
Abstract
Status epilepticus (SE) and cluster seizures (CS) are common occurrences in veterinary neurology and frequent reasons of admission to veterinary hospitals. With prolonged seizure activity, gamma amino-butyric acid (GABA) receptors (GABAa receptors) become inactive, leading to a state of pharmacoresistance to benzodiazepines and other GABAergic medications, which is called refractory status epilepticus (RSE). Prolonged seizure activity is also associated with overexpression of N-methyl-D-aspartic (NMDA) receptors. Rodent models have shown the efficacy of ketamine (KET) in treating RSE, and its use has been reported in one canine case of RSE. Boluses of KET 5 mg/kg IV have become the preferred treatment for RSE in our hospital. A retrospective study was performed to evaluate and report our experience with KET IV bolus to treat prolonged and/or repeated seizure activity in cases of canine CS, SE, and RSE. A total of 15 dogs were retrieved, for 20 hospitalizations and 28 KET IV injections over 3 years. KET IV boluses were used 12 times for RSE (9 generalized seizures, 3 focal seizures) and KET terminated the episode of RSE 12/12 times (100%); however, seizures recurred 4/12 times (33%) within ≤6 h of KET IV bolus. When used for CS apart from episodes of RSE, KET IV bolus was associated with termination of the CS episode only 4/14 times (29%). Only 4/28 (14%) KET IV boluses were associated with adverse effects imputable only to the use of KET. One dog experienced a short, self-limited seizure activity during administration of KET IV, which was most likely related to a pre-mature use of KET IV (i.e., before GABAergic resistance and NMDA receptor overexpression had taken place). This study indicates that KET 5 mg/kg IV bolus may be successful for the treatment of RSE in dogs.
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Affiliation(s)
- Patrick Roynard
- Long Island Veterinary Specialists, Department of Neurology/Neurosurgery, Plainview, NY, United States
| | - Ann Bilderback
- VCA Northwest Veterinary Specialists, Clackamas, OR, United States
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McGinnity CJ, Riaño Barros DA, Hinz R, Myers JF, Yaakub SN, Thyssen C, Heckemann RA, de Tisi J, Duncan JS, Sander JW, Lingford-Hughes A, Koepp MJ, Hammers A. Αlpha 5 subunit-containing GABA A receptors in temporal lobe epilepsy with normal MRI. Brain Commun 2021; 3:fcaa190. [PMID: 33501420 PMCID: PMC7811756 DOI: 10.1093/braincomms/fcaa190] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Revised: 09/06/2020] [Accepted: 09/24/2020] [Indexed: 01/08/2023] Open
Abstract
GABAA receptors containing the α5 subunit mediate tonic inhibition and are widely expressed in the limbic system. In animals, activation of α5-containing receptors impairs hippocampus-dependent memory. Temporal lobe epilepsy is associated with memory impairments related to neuron loss and other changes. The less selective PET ligand [11C]flumazenil has revealed reductions in GABAA receptors. The hypothesis that α5 subunit receptor alterations are present in temporal lobe epilepsy and could contribute to impaired memory is untested. We compared α5 subunit availability between individuals with temporal lobe epilepsy and normal structural MRI ('MRI-negative') and healthy controls, and interrogated the relationship between α5 subunit availability and episodic memory performance, in a cross-sectional study. Twenty-three healthy male controls (median ± interquartile age 49 ± 13 years) and 11 individuals with MRI-negative temporal lobe epilepsy (seven males; 40 ± 8) had a 90-min PET scan after bolus injection of [11C]Ro15-4513, with arterial blood sampling and metabolite correction. All those with epilepsy and six controls completed the Adult Memory and Information Processing Battery on the scanning day. 'Bandpass' exponential spectral analyses were used to calculate volumes of distribution separately for the fast component [V F; dominated by signal from α1 (α2, α3)-containing receptors] and the slow component (V S; dominated by signal from α5-containing receptors). We made voxel-by-voxel comparisons between: the epilepsy and control groups; each individual case versus the controls. We obtained parametric maps of V F and V S measures from a single bolus injection of [11C]Ro15-4513. The epilepsy group had higher V S in anterior medial and lateral aspects of the temporal lobes, the anterior cingulate gyri, the presumed area tempestas (piriform cortex) and the insulae, in addition to increases of ∼24% and ∼26% in the ipsilateral and contralateral hippocampal areas (P < 0.004). This was associated with reduced V F:V S ratios within the same areas (P < 0.009). Comparisons of V S for each individual with epilepsy versus controls did not consistently lateralize the epileptogenic lobe. Memory scores were significantly lower in the epilepsy group than in controls (mean ± standard deviation -0.4 ± 1.0 versus 0.7 ± 0.3; P = 0.02). In individuals with epilepsy, hippocampal V S did not correlate with memory performance on the Adult Memory and Information Processing Battery. They had reduced V F in the hippocampal area, which was significant ipsilaterally (P = 0.03), as expected from [11C]flumazenil studies. We found increased tonic inhibitory neurotransmission in our cohort of MRI-negative temporal lobe epilepsy who also had co-morbid memory impairments. Our findings are consistent with a subunit shift from α1/2/3 to α5 in MRI-negative temporal lobe epilepsy.
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Affiliation(s)
- Colm J McGinnity
- Centre for Neuroscience, Department of Medicine, Imperial College London, London W12 0NN, UK
- MRC Clinical Sciences Centre, Hammersmith Hospital, London W12 0NN, UK
- King's College London & Guy's and St Thomas' PET Centre, School of Biomedical Engineering & Imaging Sciences, King’s College London, London SE1 7EH, UK
| | - Daniela A Riaño Barros
- Centre for Neuroscience, Department of Medicine, Imperial College London, London W12 0NN, UK
- MRC Clinical Sciences Centre, Hammersmith Hospital, London W12 0NN, UK
| | - Rainer Hinz
- Wolfson Molecular Imaging Centre, University of Manchester, Manchester M20 3LJ, UK
| | - James F Myers
- Centre for Neuroscience, Department of Medicine, Imperial College London, London W12 0NN, UK
| | - Siti N Yaakub
- King's College London & Guy's and St Thomas' PET Centre, School of Biomedical Engineering & Imaging Sciences, King’s College London, London SE1 7EH, UK
| | - Charlotte Thyssen
- Medical Image and Signal Processing (MEDISIP), Department of Electronics and Information Systems, Faculty of Engineering and Architecture, Ghent University, 9000 Ghent, Belgium
| | - Rolf A Heckemann
- Department of Medical Radiation Sciences, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, 413 45 Gothenburg, Sweden
| | - Jane de Tisi
- NIHR University College London Hospitals Biomedical Research Centre, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK, and Chalfont Centre for Epilepsy, Chalfont St Peter SL9 0RJ, UK
| | - John S Duncan
- NIHR University College London Hospitals Biomedical Research Centre, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK, and Chalfont Centre for Epilepsy, Chalfont St Peter SL9 0RJ, UK
| | - Josemir W Sander
- NIHR University College London Hospitals Biomedical Research Centre, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK, and Chalfont Centre for Epilepsy, Chalfont St Peter SL9 0RJ, UK
- Stichting Epilepsie Instellingen Nederland (SEIN), Heemstede 2103SW, The Netherlands
| | - Anne Lingford-Hughes
- Neuropsychopharmacology Unit, Centre for Psychiatry, Department of Brain Sciences, Faculty of Medicine, Imperial College London, London W12 0NN, UK
| | - Matthias J Koepp
- NIHR University College London Hospitals Biomedical Research Centre, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK, and Chalfont Centre for Epilepsy, Chalfont St Peter SL9 0RJ, UK
| | - Alexander Hammers
- Centre for Neuroscience, Department of Medicine, Imperial College London, London W12 0NN, UK
- MRC Clinical Sciences Centre, Hammersmith Hospital, London W12 0NN, UK
- King's College London & Guy's and St Thomas' PET Centre, School of Biomedical Engineering & Imaging Sciences, King’s College London, London SE1 7EH, UK
- Neurodis Foundation, CERMEP, Imagerie du Vivant, 69003 Lyon, France
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11
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Sperk G, Kirchmair E, Bakker J, Sieghart W, Drexel M, Kondova I. Immunohistochemical distribution of 10 GABA A receptor subunits in the forebrain of the rhesus monkey Macaca mulatta. J Comp Neurol 2020; 528:2551-2568. [PMID: 32220012 PMCID: PMC7496627 DOI: 10.1002/cne.24910] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 03/11/2020] [Accepted: 03/19/2020] [Indexed: 12/23/2022]
Abstract
GABAA receptors are composed of five subunits arranged around a central chloride channel. Their subunits originate from different genes or gene families. The majority of GABAA receptors in the mammalian brain consist of two α-, two β- and one γ- or δ-subunit. This subunit organization crucially determines the physiological and pharmacological properties of the GABAA receptors. Using immunohistochemistry, we investigated the distribution of 10 GABAA receptor subunits (α1, α2, α3, α4, α5, β1, β2, β3, γ2, and δ) in the fore brain of three female rhesus monkeys (Macaca mulatta). Within the cerebral cortex, subunits α1, α5, β2, β3, and γ2 were found in all layers, α2, α3, and β1 were more concentrated in the inner and outer layers. The caudate/putamen was rich in α1, α2, α5, all three β-subunits, γ2, and δ. Subunits α3 and α5 were more concentrated in the caudate than in the putamen. In contrast, α1, α2, β1, β2, γ2, and δ were highest in the pallidum. Most dorsal thalamic nuclei contained subunits α1, α2, α4, β2, β3, and γ2, whereas α1, α3, β1, and γ2 were most abundant in the reticular nucleus. Within the amygdala, subunits α1, α2, α5, β1, β3, γ2, and δ were concentrated in the cortical nucleus, whereas in the lateral and basolateral amygdala α1, α2, α5, β1, β3, and δ, and in the central amygdala α1, α2, β3, and γ2 were most abundant. Interestingly, subunit α3-IR outlined the intercalated nuclei of the amygdala. In the hippocampus, subunits α1, α2, α5, β2, β3, γ2, and δ were highly expressed in the dentate molecular layer, whereas α1, α2, α3, α5, β1, β2, β3, and γ2 were concentrated in sector CA1 and the subiculum. The distribution of GABAA receptor subunits in the rhesus monkey was highly heterogeneous indicating a high number of differently assembled receptors. In most areas investigated, notably in the striatum/pallidum, amygdaloid nuclei and in the hippocampus it was more diverse than in the rat and mouse indicating a more heterogeneous and less defined receptor assembly in the monkey than in rodent brain.
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Key Words
- GABAA receptor subunits
- RRID:AB_2108828
- ab GAD67, RRID:AB_2278725
- ab NeuN, RRID:AB_2278725
- ab α2, RRID:AB_2827793
- ab α3, RRID:AB_2827797
- ab α4, RRID:AB_2827798
- ab α5, RRID:AB_2827799
- ab β1, RRID:AB_2827800
- ab β2, RRID:AB_2827801
- ab β3, RRID:AB_2827802
- ab γ2, RRID:AB_2827803
- ab δ, RRID:AB_2827804
- amygdala
- antibody α1 (BD24)
- basal ganglia
- benzodiazepine
- goat biotinylated anti-rabbit ab, RRID:AB_2336810
- horse anti-mouse ab, RRID:AB_2336811
- immunohistochemistry
- monkey
- primate
- thalamus
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Affiliation(s)
- Günther Sperk
- Department of PharmacologyMedical University InnsbruckInnsbruckAustria
| | - Elke Kirchmair
- Department of PharmacologyMedical University InnsbruckInnsbruckAustria
| | - Jaco Bakker
- Division of Veterinary Care, Animal Science DepartmentBiomedical Primate Research CentreRijswijkThe Netherlands
| | - Werner Sieghart
- Department of Molecular Neurosciences, Center for Brain ResearchMedical University ViennaViennaAustria
| | - Meinrad Drexel
- Department of PharmacologyMedical University InnsbruckInnsbruckAustria
| | - Ivanela Kondova
- Division of Pathology and Microbiology, Animal Science DepartmentBiomedical Primate Research CentreRijswijkThe Netherlands
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12
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Stefanits H, Milenkovic I, Mahr N, Pataraia E, Baumgartner C, Hainfellner JA, Kovacs GG, Kasprian G, Sieghart W, Yilmazer-Hanke D, Czech T. Alterations in GABAA Receptor Subunit Expression in the Amygdala and Entorhinal Cortex in Human Temporal Lobe Epilepsy. J Neuropathol Exp Neurol 2020; 78:1022-1048. [PMID: 31631219 DOI: 10.1093/jnen/nlz085] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2019] [Revised: 07/06/2019] [Indexed: 12/14/2022] Open
Abstract
The amygdala has long been implicated in the pathophysiology of human temporal lobe epilepsy (TLE). The different nuclei of this complex structure are interconnected and share reciprocal connections with the hippocampus and other brain structures, partly via the entorhinal cortex. Expression of GABAA receptor subunits α1, α2, α3, α5, β2, β2/3, and γ2 was evaluated by immunohistochemistry in amygdala specimens and the entorhinal cortex of 12 TLE patients and 12 autopsy controls. A substantial decrease in the expression of α1, α2, α3, and β2/3 subunits was found in TLE cases, accompanied by an increase of γ2 subunit expression in many nuclei. In the entorhinal cortex, the expression of all GABAA receptor subunits was decreased except for the α1 subunit, which was increased on cellular somata. The overall reduction in α subunit expression may lead to decreased sensitivity to GABA and its ligands and compromise phasic inhibition, whereas upregulation of the γ2 subunit might influence clustering and kinetics of receptors and impair tonic inhibition. The description of these alterations in the human amygdala is important for the understanding of network changes in TLE as well as the development of subunit-specific therapeutic agents for the treatment of this disease.
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Affiliation(s)
- Harald Stefanits
- Department of Neurosurgery, Institute of Neurology, Department of Neurology, Department of Biomedical Imaging and Image Guided Therapy, Center for Brain Research, Department of Molecular Neurosciences, Medical University of Vienna, Vienna, Austria; Second Neurological Department, General Hospital Hietzing, Vienna, Austria; and Clinical Neuroanatomy, Neurology Department, Medical Faculty, Ulm University, Ulm, Germany
| | - Ivan Milenkovic
- Department of Neurosurgery, Institute of Neurology, Department of Neurology, Department of Biomedical Imaging and Image Guided Therapy, Center for Brain Research, Department of Molecular Neurosciences, Medical University of Vienna, Vienna, Austria; Second Neurological Department, General Hospital Hietzing, Vienna, Austria; and Clinical Neuroanatomy, Neurology Department, Medical Faculty, Ulm University, Ulm, Germany
| | - Nina Mahr
- Department of Neurosurgery, Institute of Neurology, Department of Neurology, Department of Biomedical Imaging and Image Guided Therapy, Center for Brain Research, Department of Molecular Neurosciences, Medical University of Vienna, Vienna, Austria; Second Neurological Department, General Hospital Hietzing, Vienna, Austria; and Clinical Neuroanatomy, Neurology Department, Medical Faculty, Ulm University, Ulm, Germany
| | - Ekaterina Pataraia
- Department of Neurosurgery, Institute of Neurology, Department of Neurology, Department of Biomedical Imaging and Image Guided Therapy, Center for Brain Research, Department of Molecular Neurosciences, Medical University of Vienna, Vienna, Austria; Second Neurological Department, General Hospital Hietzing, Vienna, Austria; and Clinical Neuroanatomy, Neurology Department, Medical Faculty, Ulm University, Ulm, Germany
| | - Christoph Baumgartner
- Department of Neurosurgery, Institute of Neurology, Department of Neurology, Department of Biomedical Imaging and Image Guided Therapy, Center for Brain Research, Department of Molecular Neurosciences, Medical University of Vienna, Vienna, Austria; Second Neurological Department, General Hospital Hietzing, Vienna, Austria; and Clinical Neuroanatomy, Neurology Department, Medical Faculty, Ulm University, Ulm, Germany
| | - Johannes A Hainfellner
- Department of Neurosurgery, Institute of Neurology, Department of Neurology, Department of Biomedical Imaging and Image Guided Therapy, Center for Brain Research, Department of Molecular Neurosciences, Medical University of Vienna, Vienna, Austria; Second Neurological Department, General Hospital Hietzing, Vienna, Austria; and Clinical Neuroanatomy, Neurology Department, Medical Faculty, Ulm University, Ulm, Germany
| | - Gabor G Kovacs
- Department of Neurosurgery, Institute of Neurology, Department of Neurology, Department of Biomedical Imaging and Image Guided Therapy, Center for Brain Research, Department of Molecular Neurosciences, Medical University of Vienna, Vienna, Austria; Second Neurological Department, General Hospital Hietzing, Vienna, Austria; and Clinical Neuroanatomy, Neurology Department, Medical Faculty, Ulm University, Ulm, Germany
| | - Gregor Kasprian
- Department of Neurosurgery, Institute of Neurology, Department of Neurology, Department of Biomedical Imaging and Image Guided Therapy, Center for Brain Research, Department of Molecular Neurosciences, Medical University of Vienna, Vienna, Austria; Second Neurological Department, General Hospital Hietzing, Vienna, Austria; and Clinical Neuroanatomy, Neurology Department, Medical Faculty, Ulm University, Ulm, Germany
| | - Werner Sieghart
- Department of Neurosurgery, Institute of Neurology, Department of Neurology, Department of Biomedical Imaging and Image Guided Therapy, Center for Brain Research, Department of Molecular Neurosciences, Medical University of Vienna, Vienna, Austria; Second Neurological Department, General Hospital Hietzing, Vienna, Austria; and Clinical Neuroanatomy, Neurology Department, Medical Faculty, Ulm University, Ulm, Germany
| | - Deniz Yilmazer-Hanke
- Department of Neurosurgery, Institute of Neurology, Department of Neurology, Department of Biomedical Imaging and Image Guided Therapy, Center for Brain Research, Department of Molecular Neurosciences, Medical University of Vienna, Vienna, Austria; Second Neurological Department, General Hospital Hietzing, Vienna, Austria; and Clinical Neuroanatomy, Neurology Department, Medical Faculty, Ulm University, Ulm, Germany
| | - Thomas Czech
- Department of Neurosurgery, Institute of Neurology, Department of Neurology, Department of Biomedical Imaging and Image Guided Therapy, Center for Brain Research, Department of Molecular Neurosciences, Medical University of Vienna, Vienna, Austria; Second Neurological Department, General Hospital Hietzing, Vienna, Austria; and Clinical Neuroanatomy, Neurology Department, Medical Faculty, Ulm University, Ulm, Germany
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13
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Joshi S, Roden WH, Kapur J, Jansen LA. Reduced neurosteroid potentiation of GABA A receptors in epilepsy and depolarized hippocampal neurons. Ann Clin Transl Neurol 2020; 7:527-542. [PMID: 32243088 PMCID: PMC7187710 DOI: 10.1002/acn3.51023] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Revised: 03/03/2020] [Accepted: 03/10/2020] [Indexed: 01/15/2023] Open
Abstract
OBJECTIVE Neurosteroids regulate neuronal excitability by potentiating γ-aminobutyric acid type-A receptors (GABARs). In animal models of temporal lobe epilepsy, the neurosteroid sensitivity of GABARs is diminished and GABAR subunit composition is altered. We tested whether similar changes occur in patients with epilepsy and if depolarization-induced increases in neuronal activity can replicate this effect. METHODS We determined GABAR α4 subunit expression in cortical tissue resected from pediatric epilepsy patients. Modulation of human GABARs by allopregnanolone and Ro15-4513 was measured in Xenopus oocytes using whole-cell patch clamp. To extend the findings obtained using tissue from epilepsy patients, we evaluated GABAR expression and modulation by allopregnanolone and Ro15-4513 in cultured rat hippocampal neurons exposed to high extracellular potassium (HK) to increase neuronal activity. RESULTS Expression of α4 subunits was increased in pediatric cortical epilepsy specimens encompassing multiple pathologies. The potentiation of GABA-evoked currents by the neurosteroid allopregnanolone was decreased in Xenopus oocytes expressing GABARs isolated from epilepsy patients. Furthermore, receptors isolated from epilepsy but not control tissue were sensitive to potentiation by Ro15-4513, indicating higher expression of α4 βx γ2 subunit-containing receptors. Correspondingly, increasing the activity of cultured rat hippocampal neurons reduced allopregnanolone potentiation of miniature inhibitory postsynaptic currents (mIPSCs), increased modulation of tonic GABAR current by Ro15-4513, upregulated the surface expression of α4 and γ2 subunits, and increased the colocalization of α4 and γ2 subunit immunoreactivity. INTERPRETATION These findings suggest that seizure activity-induced upregulation of α4 βx γ2 subunit-containing GABARs could affect the anticonvulsant actions of neurosteroids.
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Affiliation(s)
- Suchitra Joshi
- Department of NeurologyUniversity of VirginiaCharlottesvilleVirginia
| | | | - Jaideep Kapur
- Department of NeurologyUniversity of VirginiaCharlottesvilleVirginia
- Department of NeuroscienceUniversity of VirginiaCharlottesvilleVirginia
- UVA Brain InstituteUniversity of VirginiaCharlottesvilleVirginia
| | - Laura A. Jansen
- Department of NeurologyUniversity of VirginiaCharlottesvilleVirginia
- Seattle Children’s Research InstituteSeattleWashington
- Department of NeurologyWashington University School of MedicineSt. LouisWashington
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14
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Auer T, Schreppel P, Erker T, Schwarzer C. Impaired chloride homeostasis in epilepsy: Molecular basis, impact on treatment, and current treatment approaches. Pharmacol Ther 2020; 205:107422. [DOI: 10.1016/j.pharmthera.2019.107422] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 10/07/2019] [Indexed: 12/14/2022]
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15
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Liu DH, Agbo E, Zhang SH, Zhu JL. Anticonvulsant and Neuroprotective Effects of Paeonol in Epileptic Rats. Neurochem Res 2019; 44:2556-2565. [PMID: 31520267 DOI: 10.1007/s11064-019-02874-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Revised: 09/06/2019] [Accepted: 09/09/2019] [Indexed: 12/14/2022]
Abstract
Paeonol is the main active compound in the root bark extract of the peony tree, and it has antioxidative and anti-inflammatory effects. Recent studies have reported the neuroprotective effects of paeonol including its capacity in improving impaired memory. However, the effect of paeonol on epilepsy is yet to be demystified. We aimed to investigate the therapeutic effect of paeonol in epilepsy and its relationship with oxidative stress damage and neuronal loss in the rat brain to reveal the underlying mechanisms of epileptic seizures. A rat model for chronic epilepsy was established, and the seizure scores of the rats in different groups were recorded. The seizure duration and the seizure onset latency were used to evaluate the anticonvulsant effects of paeonol. Terminal deoxynucleotidyl transferase dUTP nick end-labeling staining, Nissl staining and H/E staining were used to evaluate the effects of paeonol on neuronal loss and apoptosis in epileptic rats. The colorimetric assessment of malondialdehyde (MDA) content, superoxide dismutase (SOD) activity, catalase activity and total antioxidant capacity of paeonol were used in assessing paeonol's effect on oxidative stress in epileptic rats. Evaluation of Caspase-3 mRNA and protein expression levels were determined using western blot and quantitative real-time (RT-q)PCR. In this study, we found that paeonol reduced the seizure scores of epileptic rats and attenuated the duration and onset latency of seizures. Paeonol can also increase the activities of total antioxidant capacity, SOD and catalase activity and reduce MDA content as well. This suggests that paeonol can improve the level of oxidative stress in rats. More significantly, paeonol can improve neuronal loss and apoptosis in epileptic rats. These results indicate that paeonol has anticonvulsant and neuroprotective effects in epileptic rats. This effect may be caused by reducing oxidative stress.
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Affiliation(s)
- Dong-Hai Liu
- School of Basic Medicine, Jiamusi University, Jiamusi, 154007, Heilongjiang, People's Republic of China
| | - Elvis Agbo
- Department of Anatomy, School of Basic Medicine, Jiamusi University, Jiamusi, 154007, Heilongjiang, People's Republic of China
| | - Shu-Hong Zhang
- Department of Biology, School of Basic Medicine, Jiamusi University, Jiamusi, 154007, Heilongjiang, People's Republic of China
| | - Jin-Ling Zhu
- Department of Biology, School of Basic Medicine, Jiamusi University, Jiamusi, 154007, Heilongjiang, People's Republic of China.
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16
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Kwon JY, Jeon MT, Jung UJ, Kim DW, Moon GJ, Kim SR. Perspective: Therapeutic Potential of Flavonoids as Alternative Medicines in Epilepsy. Adv Nutr 2019; 10:778-790. [PMID: 31111873 PMCID: PMC6743823 DOI: 10.1093/advances/nmz047] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 03/05/2019] [Accepted: 04/08/2019] [Indexed: 12/18/2022] Open
Abstract
Epilepsy is a chronic neurological disorder that affects many people worldwide. Temporal lobe epilepsy is the most common and most studied type of epilepsy, but the pathological mechanisms underlying this condition are poorly understood. More than 20 antiepileptic drugs (AEDs) have been developed and used for the treatment of epilepsy; however, 30% of patients still experience uncontrolled epilepsy and associated comorbidities, which impair their quality of life. In addition, various side effects have been reported for AEDs, such as drowsiness, unsteadiness, dizziness, blurred or double vision, tremor (shakiness), greater risk of infections, bruising, and bleeding. Thus, critical medical needs remain unmet for patients with uncontrolled epilepsy. Flavonoids belong to a subclass of polyphenols that are widely present in fruits, vegetables, and certain beverages. Recently, many studies have reported that some flavonoids elicit various beneficial effects in patients with epilepsy without causing the side effects associated with conventional medical therapies. Moreover, flavonoids may have a property of regulating microRNA expression associated with inflammation and cell survival. These findings suggest that flavonoids, which are more effective but impose fewer adverse effects than conventional AEDs, could be used in the treatment of epilepsy.
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Affiliation(s)
- Jae Young Kwon
- School of Life Sciences, BK21 plus KNU Creative BioResearch Group, Kyungpook National University, Daegu, Republic of Korea
| | - Min-Tae Jeon
- School of Life Sciences, BK21 plus KNU Creative BioResearch Group, Kyungpook National University, Daegu, Republic of Korea
| | - Un Ju Jung
- Department of Food Science and Nutrition, Pukyong National University, Busan, Republic of Korea
| | - Dong Woon Kim
- Department of Medical Science,Department of Anatomy, Brain Research Institute, Chungnam National University School of Medicine, Daejeon, Republic of Korea
| | - Gyeong Joon Moon
- School of Life Sciences, BK21 plus KNU Creative BioResearch Group, Kyungpook National University, Daegu, Republic of Korea,Address correspondence to GJM (e-mail: )
| | - Sang Ryong Kim
- School of Life Sciences, BK21 plus KNU Creative BioResearch Group, Kyungpook National University, Daegu, Republic of Korea,Brain Science and Engineering Institute, Kyungpook National University, Daegu, Republic of Korea,Address correspondence to SRK (e-mail: )
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17
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Trujeque-Ramos S, Castillo-Rolón D, Galarraga E, Tapia D, Arenas-López G, Mihailescu S, Hernández-López S. Insulin Regulates GABA A Receptor-Mediated Tonic Currents in the Prefrontal Cortex. Front Neurosci 2018; 12:345. [PMID: 29904337 PMCID: PMC5990629 DOI: 10.3389/fnins.2018.00345] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 05/04/2018] [Indexed: 11/14/2022] Open
Abstract
Recent studies, have shown that insulin increases extrasynaptic GABAA receptor-mediated currents in the hippocampus, causing alterations of neuronal excitability. The prefrontal cortex (PFC) is another brain area which is involved in cognition functions and expresses insulin receptors. Here, we used electrophysiological, molecular, and immunocytochemical techniques to examine the effect of insulin on the extrasynaptic GABAA receptor-mediated tonic currents in brain slices. We found that insulin (20–500 nM) increases GABAA-mediated tonic currents. Our results suggest that insulin promotes the trafficking of extrasynaptic GABAA receptors from the cytoplasm to the cell membrane. Western blot analysis and immunocytochemistry showed that PFC extrasynaptic GABAA receptors contain α-5 and δ subunits. Insulin effect on tonic currents decreased the firing rate and neuronal excitability in layer 5–6 PFC cells. These effects of insulin were dependent on the activation of the PI3K enzyme, a key mediator of the insulin response within the brain. Taken together, these results suggest that insulin modulation of the GABAA-mediated tonic currents can modify the activity of neural circuits within the PFC. These actions could help to explain the alterations of cognitive processes associated with changes in insulin signaling.
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Affiliation(s)
- Saraí Trujeque-Ramos
- Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de Mexico, Mexico City, Mexico
| | - Diego Castillo-Rolón
- Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de Mexico, Mexico City, Mexico
| | - Elvira Galarraga
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de Mexico, Mexico City, Mexico
| | - Dagoberto Tapia
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de Mexico, Mexico City, Mexico
| | - Gabina Arenas-López
- Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de Mexico, Mexico City, Mexico
| | - Stefan Mihailescu
- Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de Mexico, Mexico City, Mexico
| | - Salvador Hernández-López
- Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de Mexico, Mexico City, Mexico
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18
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Szyndler J, Maciejak P, Kołosowska K, Chmielewska N, Skórzewska A, Daszczuk P, Płaźnik A. Altered expression of GABA-A receptor subunits in the hippocampus of PTZ-kindled rats. Pharmacol Rep 2018; 70:14-21. [DOI: 10.1016/j.pharep.2017.07.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 06/30/2017] [Accepted: 07/12/2017] [Indexed: 01/06/2023]
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19
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Navidhamidi M, Ghasemi M, Mehranfard N. Epilepsy-associated alterations in hippocampal excitability. Rev Neurosci 2018; 28:307-334. [PMID: 28099137 DOI: 10.1515/revneuro-2016-0059] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Accepted: 11/03/2016] [Indexed: 11/15/2022]
Abstract
The hippocampus exhibits a wide range of epilepsy-related abnormalities and is situated in the mesial temporal lobe, where limbic seizures begin. These abnormalities could affect membrane excitability and lead to overstimulation of neurons. Multiple overlapping processes refer to neural homeostatic responses develop in neurons that work together to restore neuronal firing rates to control levels. Nevertheless, homeostatic mechanisms are unable to restore normal neuronal excitability, and the epileptic hippocampus becomes hyperexcitable or hypoexcitable. Studies show that there is hyperexcitability even before starting recurrent spontaneous seizures, suggesting although hippocampal hyperexcitability may contribute to epileptogenesis, it alone is insufficient to produce epileptic seizures. This supports the concept that the hippocampus is not the only substrate for limbic seizure onset, and a broader hyperexcitable limbic structure may contribute to temporal lobe epilepsy (TLE) seizures. Nevertheless, seizures also occur in conditions where the hippocampus shows a hypoexcitable phenotype. Since TLE seizures most often originate in the hippocampus, it could therefore be assumed that both hippocampal hypoexcitability and hyperexcitability are undesirable states that make the epileptic hippocampal network less stable and may, under certain conditions, trigger seizures.
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20
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Simonsen C, Boddum K, von Schoubye NL, Kloppenburg A, Sønderskov K, Hansen SL, Kristiansen U. Anticonvulsive evaluation of THIP in the murine pentylenetetrazole kindling model: lack of anticonvulsive effect of THIP despite functional δ-subunit-containing GABA A receptors in dentate gyrus granule cells. Pharmacol Res Perspect 2017; 5. [PMID: 28805971 PMCID: PMC5684853 DOI: 10.1002/prp2.322] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Revised: 04/20/2017] [Accepted: 04/21/2017] [Indexed: 12/29/2022] Open
Abstract
THIP (4,5,6,7‐tetrahydroisoxazolo[5,4‐c]pyridin‐3‐ol) is a GABAA receptor agonist with varying potencies and efficacies at γ‐subunit‐containing receptors. More importantly, THIP acts as a selective superagonist at δ‐subunit‐containing receptors (δ‐GABAARs) at clinically relevant concentrations. Evaluation of THIP as a potential anticonvulsant has given contradictory results in different animal models and for this reason, we reevaluated the anticonvulsive properties of THIP in the murine pentylenetetrazole (PTZ) kindling model. As loss of δ‐GABAAR in the dentate gyrus has been associated with several animal models of epilepsy, we first investigated the presence of functional δ‐GABAA receptors. Both immunohistochemistry and Western blot data demonstrated that δ‐GABAAR expression is not only present in the dentate gyrus, but also the expression level was enhanced in the early phase after PTZ kindling. Whole‐cell patch‐clamp studies in acute hippocampal brain slices revealed that THIP was indeed able to induce a tonic inhibition in dentate gyrus granule cells. However, THIP induced a tonic current of similar magnitude in the PTZ‐kindled mice compared to saline‐treated animals despite the observed upregulation of δ‐GABAARs. Even in the demonstrated presence of functional δ‐GABAARs, THIP (0.5–4 mg/kg) showed no anticonvulsive effect in the PTZ kindling model using a comprehensive in vivo evaluation of the anticonvulsive properties.
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Affiliation(s)
- Charlotte Simonsen
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Kim Boddum
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark.,Faculty of Health and Medical Sciences, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Nadia L von Schoubye
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark.,Faculty of Health and Medical Sciences, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Alissa Kloppenburg
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Kasper Sønderskov
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Suzanne L Hansen
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Uffe Kristiansen
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
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21
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Lindemeyer AK, Shen Y, Yazdani F, Shao XM, Spigelman I, Davies DL, Olsen RW, Liang J. α2 Subunit-Containing GABA A Receptor Subtypes Are Upregulated and Contribute to Alcohol-Induced Functional Plasticity in the Rat Hippocampus. Mol Pharmacol 2017; 92:101-112. [PMID: 28536106 DOI: 10.1124/mol.116.107797] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 05/05/2017] [Indexed: 12/20/2022] Open
Abstract
Alcohol (EtOH) intoxication causes changes in the rodent brain γ-aminobutyric acid receptor (GABAAR) subunit composition and function, playing a crucial role in EtOH withdrawal symptoms and dependence. Building evidence indicates that withdrawal from acute EtOH and chronic intermittent EtOH (CIE) results in decreased EtOH-enhanced GABAAR δ subunit-containing extrasynaptic and EtOH-insensitive α1βγ2 subtype synaptic GABAARs but increased synaptic α4βγ2 subtype, and increased EtOH sensitivity of GABAAR miniature postsynaptic currents (mIPSCs) correlated with EtOH dependence. Here we demonstrate that after acute EtOH intoxication and CIE, upregulation of hippocampal α4βγ2 subtypes, as well as increased cell-surface levels of GABAAR α2 and γ1 subunits, along with increased α2β1γ1 GABAAR pentamers in hippocampal slices using cell-surface cross-linking, followed by Western blot and coimmunoprecipitation. One-dose and two-dose acute EtOH treatments produced temporal plastic changes in EtOH-induced anxiolysis or withdrawal anxiety, and the presence or absence of EtOH-sensitive synaptic currents correlated with cell surface peptide levels of both α4 and γ1(new α2) subunits. CIE increased the abundance of novel mIPSC patterns differing in activation/deactivation kinetics, charge transfer, and sensitivity to EtOH. The different mIPSC patterns in CIE could be correlated with upregulated highly EtOH-sensitive α2βγ subtypes and EtOH-sensitive α4βγ2 subtypes. Naïve α4 subunit knockout mice express EtOH-sensitive mIPSCs in hippocampal slices, correlating with upregulated GABAAR α2 (and not α4) subunits. Consistent with α2, β1, and γ1 subunits genetically linked to alcoholism in humans, our findings indicate that these new α2-containing synaptic GABAARs could mediate the maintained anxiolytic response to EtOH in dependent individuals, rat or human, contributing to elevated EtOH consumption.
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Affiliation(s)
- A Kerstin Lindemeyer
- Department of Molecular and Medical Pharmacology (A.K.L., Y.S., F.Y., R.W.O., J.L.), and Department of Neurobiology (X.M.S.), David Geffen School of Medicine at University of California at Los Angeles, and Division of Oral Biology and Medicine, School of Dentistry (I.S.), University of California and Titus Family Department of Clinical Pharmacy, University of Southern California School of Pharmacy (D.L.D., J.L.), Los Angeles, California
| | - Yi Shen
- Department of Molecular and Medical Pharmacology (A.K.L., Y.S., F.Y., R.W.O., J.L.), and Department of Neurobiology (X.M.S.), David Geffen School of Medicine at University of California at Los Angeles, and Division of Oral Biology and Medicine, School of Dentistry (I.S.), University of California and Titus Family Department of Clinical Pharmacy, University of Southern California School of Pharmacy (D.L.D., J.L.), Los Angeles, California
| | - Ferin Yazdani
- Department of Molecular and Medical Pharmacology (A.K.L., Y.S., F.Y., R.W.O., J.L.), and Department of Neurobiology (X.M.S.), David Geffen School of Medicine at University of California at Los Angeles, and Division of Oral Biology and Medicine, School of Dentistry (I.S.), University of California and Titus Family Department of Clinical Pharmacy, University of Southern California School of Pharmacy (D.L.D., J.L.), Los Angeles, California
| | - Xuesi M Shao
- Department of Molecular and Medical Pharmacology (A.K.L., Y.S., F.Y., R.W.O., J.L.), and Department of Neurobiology (X.M.S.), David Geffen School of Medicine at University of California at Los Angeles, and Division of Oral Biology and Medicine, School of Dentistry (I.S.), University of California and Titus Family Department of Clinical Pharmacy, University of Southern California School of Pharmacy (D.L.D., J.L.), Los Angeles, California
| | - Igor Spigelman
- Department of Molecular and Medical Pharmacology (A.K.L., Y.S., F.Y., R.W.O., J.L.), and Department of Neurobiology (X.M.S.), David Geffen School of Medicine at University of California at Los Angeles, and Division of Oral Biology and Medicine, School of Dentistry (I.S.), University of California and Titus Family Department of Clinical Pharmacy, University of Southern California School of Pharmacy (D.L.D., J.L.), Los Angeles, California
| | - Daryl L Davies
- Department of Molecular and Medical Pharmacology (A.K.L., Y.S., F.Y., R.W.O., J.L.), and Department of Neurobiology (X.M.S.), David Geffen School of Medicine at University of California at Los Angeles, and Division of Oral Biology and Medicine, School of Dentistry (I.S.), University of California and Titus Family Department of Clinical Pharmacy, University of Southern California School of Pharmacy (D.L.D., J.L.), Los Angeles, California
| | - Richard W Olsen
- Department of Molecular and Medical Pharmacology (A.K.L., Y.S., F.Y., R.W.O., J.L.), and Department of Neurobiology (X.M.S.), David Geffen School of Medicine at University of California at Los Angeles, and Division of Oral Biology and Medicine, School of Dentistry (I.S.), University of California and Titus Family Department of Clinical Pharmacy, University of Southern California School of Pharmacy (D.L.D., J.L.), Los Angeles, California
| | - Jing Liang
- Department of Molecular and Medical Pharmacology (A.K.L., Y.S., F.Y., R.W.O., J.L.), and Department of Neurobiology (X.M.S.), David Geffen School of Medicine at University of California at Los Angeles, and Division of Oral Biology and Medicine, School of Dentistry (I.S.), University of California and Titus Family Department of Clinical Pharmacy, University of Southern California School of Pharmacy (D.L.D., J.L.), Los Angeles, California
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Yu YH, Lee K, Sin DS, Park KH, Park DK, Kim DS. Altered functional efficacy of hippocampal interneuron during epileptogenesis following febrile seizures. Brain Res Bull 2017; 131:25-38. [DOI: 10.1016/j.brainresbull.2017.02.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 02/17/2017] [Accepted: 02/23/2017] [Indexed: 12/22/2022]
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Moghbelinejad S, Alizadeh S, Mohammadi G, Khodabandehloo F, Rashvand Z, Najafipour R, Nassiri-Asl M. The effects of quercetin on the gene expression of the GABA A receptor α5 subunit gene in a mouse model of kainic acid-induced seizure. J Physiol Sci 2017; 67:339-343. [PMID: 27743178 PMCID: PMC10717378 DOI: 10.1007/s12576-016-0497-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 10/04/2016] [Indexed: 10/20/2022]
Abstract
The flavonoid quercetin has recently been reported to have neuroprotective effects, and the role of the gamma-aminobutyric acid A alpha 5 subunit (GABAA α5) receptor has been determined in some nervous system disorders. The aim of this study was to identify the molecular mechanism of the effect of quercetin administered at anticonvulsive doses on the expression of the GABAA α5 receptor gene in kainic acid (KA)-induced seizures in mice. The experimental animals were divided into four groups: control, KA, and KA + quercetin at 50 or 100 mg/kg, respectively. The results showed a dose-dependent reduction in the behavioral seizure score with quercetin pre-treatment in the KA mouse model. Two hours after the end of the 7-day treatment regimen, expression of the GABAA α5 receptor gene in the hippocampus was found to be increased in the KA group, but this increase was reduced in the KA + quercetin 50 or 100 mg/kg treatment groups. These results suggest that expression of the GABAA α5 receptor could be a mechanism for reducing seizure severity or may be a marker of seizure severity. Further studies are necessary to clarify quercetin's mechanism of action and the relation of GABAA α5 receptor gene expression to seizure severity.
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Affiliation(s)
- Sahar Moghbelinejad
- Cellular and Molecular Research Center, Qazvin University of Medical Sciences, Qazvin, Iran
| | - Safar Alizadeh
- Cellular and Molecular Research Center, Qazvin University of Medical Sciences, Qazvin, Iran
| | - Ghazaleh Mohammadi
- Department of Molecular Medicine, Qazvin University of Medical Sciences, Qazvin, Iran
| | | | - Zahra Rashvand
- Cellular and Molecular Research Center, Qazvin University of Medical Sciences, Qazvin, Iran
| | - Reza Najafipour
- Cellular and Molecular Research Center, Qazvin University of Medical Sciences, Qazvin, Iran
| | - Marjan Nassiri-Asl
- Cellular and Molecular Research Center, Qazvin University of Medical Sciences, Qazvin, Iran.
- Cellular and Molecular Research Center, Department of Pharmacology, Qazvin University of Medical Sciences, P.O. Box 341197-5981, Qazvin, Iran.
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Moghbelinejad S, Rashvand Z, Khodabandehloo F, Mohammadi G, Nassiri-Asl M. Modulation of the Expression of the GABAA Receptor β1 and β3 Subunits by Pretreatment with Quercetin in the KA Model of Epilepsy in Mice: -The Effect of Quercetin on GABAA Receptor Beta Subunits. J Pharmacopuncture 2016; 19:163-6. [PMID: 27386150 PMCID: PMC4931302 DOI: 10.3831/kpi.2016.19.018] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Objectives: Quercetin is a flavonoid and an important dietary constituent of fruits and vegetables. In recent years, several pharmacological activities of quercetin, such as its neuroprotective activity and, more specifically, its anti-convulsant effects in animal models of epilepsy, have been reported. This study evaluated the role of quercetin pretreatment on gene expression of γ-amino butyric acid type A (GABAA) receptor beta subunits in kainic acid (KA)-induced seizures in mice. Methods: The animals were divided into four groups: one saline group, one group in which seizures were induced by using KA (10 mg/kg) without quercetin pretreatment and two groups pretreated with quercetin (50 and 100 mg/kg) prior to seizures being induced by using KA. Next, the messenger ribonucleic acid (mRNA) levels of the GABAA receptor β subunits in the hippocampus of each animal were assessed at 2 hours and 7 days after KA administration. Quantitative real-time polymerase chain reaction (RT-PCR) assay was used to detect mRNA content in hippocampal tissues. Results: Pretreatments with quercetin at doses of 50 and 100 mg/kg prevented significant increases in the mRNA levels of the β1 and the β3 subunits of the GABAA receptor at 2 hours after KA injection. Pretreatment with quercetin (100 mg/kg) significantly inhibited β1 and β3 gene expression in the hippocampus at 7 days after KA injection. But, this inhibitory effect of quercetin at 50 mg/kg on the mRNA levels of the β3 subunit of the GABAA receptor was not observed at 7 days after KA administration. Conclusion: These results suggest that quercetin (100 mg/kg) modulates the expression of the GABAA receptor β1 and β3 subunits in the KA model of epilepsy, most likely to prevent compensatory responses. This may be related to the narrow therapeutic dose range for the anticonvulsant activities of quercetin.
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Affiliation(s)
- Sahar Moghbelinejad
- Cellular and Molecular Research Center, Qazvin University of Medical Sciences, Qazvin, Iran
| | - Zahra Rashvand
- Cellular and Molecular Research Center, Qazvin University of Medical Sciences, Qazvin, Iran
| | | | - Ghazaleh Mohammadi
- Department of Molecular Medicine, Qazvin University of Medical Sciences, Qazvin, Iran
| | - Marjan Nassiri-Asl
- Cellular and Molecular Research Center, Qazvin University of Medical Sciences, Qazvin, Iran
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Sharma AK, Reams RY, Jordan WH, Miller MA, Thacker HL, Snyder PW. Mesial Temporal Lobe Epilepsy: Pathogenesis, Induced Rodent Models and Lesions. Toxicol Pathol 2016; 35:984-99. [PMID: 18098044 DOI: 10.1080/01926230701748305] [Citation(s) in RCA: 195] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Mesial temporal lobe epilepsy (MTLE), the most common epilepsy in adults, is generally intractable and is suspected to be the result of recurrent excitation or inhibition circuitry. Recurrent excitation and the development of seizures have been associated with aberrant mossy fiber sprouting in the hippocampus. Of the animal models developed to investigate the pathogenesis of MTLE, post-status epilepticus models have received the greatest acceptance because they are characterized by a latency period, the development of spontaneous motor seizures, and a spectrum of lesions like those of MTLE. Among post-status epilepticus models, induction of systemic kainic acid or pilocarpine-induced epilepsy is less labor-intensive than electrical-stimulation models and these models mirror the clinicopathologic features of MTLE more closely than do kindling, tetanus toxin, hyperthermia, post-traumatic, and perinatal hypoxia/ischemia models. Unfortunately, spontaneous motor seizures do not develop in kindling or adult hyperthermia models and are not a consistent finding in tetanus toxin-induced or perinatal hypoxia/ischemia models. This review presents the mechanistic hypotheses for seizure induction, means of model induction, and associated pathology, especially as compared to MTLE patients. Animal models are valuable tools not only to study the pathogenesis of MTLE, but also to evaluate potential antiepileptogenic drugs.
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Affiliation(s)
- Alok K. Sharma
- Department of Comparative Pathobiology, Purdue University, West Lafayette, IN 47907, USA
- Department of Pathology, Covance Laboratories Inc., Madison, WI, 53704, USA
| | - Rachel Y. Reams
- Department of Pathology, Lilly Research Laboratories, Division of Eli Lilly and Co., Greenfield, IN, 46140, USA
| | - William H. Jordan
- Department of Pathology, Lilly Research Laboratories, Division of Eli Lilly and Co., Greenfield, IN, 46140, USA
| | - Margaret A. Miller
- Department of Comparative Pathobiology, Purdue University, West Lafayette, IN 47907, USA
| | - H. Leon Thacker
- Department of Comparative Pathobiology, Purdue University, West Lafayette, IN 47907, USA
| | - Paul W. Snyder
- Department of Comparative Pathobiology, Purdue University, West Lafayette, IN 47907, USA
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Svensson M, Grahm M, Ekstrand J, Höglund P, Johansson M, Tingström A. Effect of electroconvulsive seizures on cognitive flexibility. Hippocampus 2016; 26:899-910. [DOI: 10.1002/hipo.22573] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/01/2016] [Indexed: 12/26/2022]
Affiliation(s)
- Maria Svensson
- Department of Clinical Sciences Lund; Psychiatric Neuromodulation Unit, Lund University; Lund Sweden
| | - Matilda Grahm
- Department of Clinical Sciences Lund; Psychiatric Neuromodulation Unit, Lund University; Lund Sweden
| | - Joakim Ekstrand
- Department of Clinical Sciences Lund; Psychiatric Neuromodulation Unit, Lund University; Lund Sweden
| | - Peter Höglund
- Department of Laboratory Medicine; Division of Clinical Chemistry and Pharmacology, Lund University; Lund Sweden
| | - Mikael Johansson
- Department of Clinical Sciences Lund; Psychiatric Neuromodulation Unit, Lund University; Lund Sweden
- Department of Psychology; Neuropsychology, Lund University; Lund Sweden
| | - Anders Tingström
- Department of Clinical Sciences Lund; Psychiatric Neuromodulation Unit, Lund University; Lund Sweden
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Naserpour Farivar T, Nassiri-Asl M, Johari P, Najafipour R, Hajiali F. The Effects of Kainic Acid-Induced Seizure on Gene Expression of Brain Neurotransmitter Receptors in Mice Using RT 2 PCR Array. Basic Clin Neurosci 2016; 7:291-298. [PMID: 27872690 PMCID: PMC5102558 DOI: 10.15412/j.bcn.03070402] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Introduction: Kainic acid (KA) induces neuropathological changes in specific regions of the mouse hippocampus comparable to changes seen in patients with chronic temporal lobe epilepsy (TLE). According to different studies, the expression of a number of genes are altered in the adult rat hippocampus after status epilepticus (SE) induced by KA. This study aimed to quantitatively evaluate changes in the gene expression of brain neurotransmitter receptors one week after administration of kainic acid in the mouse hippocampus. Methods: We used 12 BALB/c mice in this study and randomly divided them into 2 groups. To both groups, saline (IP) was administered for 7 days, and on the last day, KA (10 mg/kg, IP) was injected 30 minutes after administration of saline. Subsequently, behavioural changes were observed in mice. Then, in one group (1 day group), 2 hours and in another group (7 days group), 7 days after KA administration, the hippocampus tissue of mice was removed and used for gene expression analyses. Total brain RNA was isolated and reversely transcribed. We performed qPCR using RT2 Profiler TMPCR Array Mouse Neurotransmitter Receptors and Regulators (QIAGEN) containing primers for 84 genes. In this regard, we selected 50 related genes for KA model. Results: Our results showed significant changes in the gene expression of GABAA subunits receptors, including α1-α3, α5, α6, β2, β3, γ1, ρ, and rho1-2 on day 7 compared with the day 1. Conclusion: Expression of both inhibitory and excitatory receptors changed after one week. Further studies are needed to find more molecular changes in the gene expression of brain neurotransmitter receptors and regulators over longer periods of time in KA models using RT2 PCR array.
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Affiliation(s)
| | - Marjan Nassiri-Asl
- Cellular and Molecular Research Centre, Qazvin University of Medical Sciences, Qazvin, Iran.; Department of Pharmacology, School of Medicine, Qazvin University of Medical Sciences, Qazvin, Iran
| | - Pouran Johari
- Cellular and Molecular Research Centre, Qazvin University of Medical Sciences, Qazvin, Iran
| | - Reza Najafipour
- Cellular and Molecular Research Centre, Qazvin University of Medical Sciences, Qazvin, Iran
| | - Farid Hajiali
- Department of Pharmacology, School of Medicine, Qazvin University of Medical Sciences, Qazvin, Iran
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28
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Schipper S, Aalbers MW, Rijkers K, Swijsen A, Rigo JM, Hoogland G, Vles JSH. Tonic GABAA Receptors as Potential Target for the Treatment of Temporal Lobe Epilepsy. Mol Neurobiol 2015; 53:5252-65. [PMID: 26409480 PMCID: PMC5012145 DOI: 10.1007/s12035-015-9423-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 09/03/2015] [Indexed: 12/11/2022]
Abstract
Tonic GABAA receptors are a subpopulation of receptors that generate long-lasting inhibition and thereby control network excitability. In recent years, these receptors have been implicated in various neurological and psychiatric disorders, including Parkinson’s disease, schizophrenia, and epilepsy. Their distinct subunit composition and function, compared to phasic GABAA receptors, opens the possibility to specifically modulate network properties. In this review, the role of tonic GABAA receptors in epilepsy and as potential antiepileptic target will be discussed.
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Affiliation(s)
- S Schipper
- Department of Neurology, Maastricht University Medical Center, Maastricht, The Netherlands.
- Faculty of Health Medicine and Life Sciences, School of Mental Health and Neuroscience, Maastricht University Medical Center, Maastricht, The Netherlands.
| | - M W Aalbers
- Faculty of Health Medicine and Life Sciences, School of Mental Health and Neuroscience, Maastricht University Medical Center, Maastricht, The Netherlands
| | - K Rijkers
- Faculty of Health Medicine and Life Sciences, School of Mental Health and Neuroscience, Maastricht University Medical Center, Maastricht, The Netherlands
- Department of Neurosurgery and Orthopedic Surgery, Atrium Hospital Heerlen, Heerlen, The Netherlands
| | - A Swijsen
- BIOMED Research Institute, Hasselt University/Transnational University Limburg, Martelarenlaan 42, 3500, Hasselt, Belgium
| | - J M Rigo
- BIOMED Research Institute, Hasselt University/Transnational University Limburg, Martelarenlaan 42, 3500, Hasselt, Belgium
| | - G Hoogland
- Faculty of Health Medicine and Life Sciences, School of Mental Health and Neuroscience, Maastricht University Medical Center, Maastricht, The Netherlands
- Department of Neurosurgery, Maastricht University Medical Center, Maastricht, The Netherlands
| | - J S H Vles
- Department of Neurology, Maastricht University Medical Center, Maastricht, The Netherlands
- Faculty of Health Medicine and Life Sciences, School of Mental Health and Neuroscience, Maastricht University Medical Center, Maastricht, The Netherlands
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Jagirdar R, Drexel M, Kirchmair E, Tasan RO, Sperk G. Rapid changes in expression of class I and IV histone deacetylases during epileptogenesis in mouse models of temporal lobe epilepsy. Exp Neurol 2015; 273:92-104. [PMID: 26238735 DOI: 10.1016/j.expneurol.2015.07.026] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 06/19/2015] [Accepted: 07/28/2015] [Indexed: 11/20/2022]
Abstract
A prominent role of epigenetic mechanisms in manifestation of epilepsy has been proposed. Thus altered histone H3 and H4 acetylation has been demonstrated in experimental models of temporal lobe epilepsy (TLE). We now investigated changes in the expression of the class I and class IV histone deacetylases (HDAC) in two complementary mouse TLE models. Unilateral intrahippocampal injection of kainic acid (KA) induced a status epilepticus lasting 6 to 24h, development of spontaneous limbic seizures (2 to 3 days after KA injection) and chronic epilepsy, as revealed by telemetric recordings of the EEGs. Mice were killed at different intervals after KA injection and expression of HDAC mRNAs was investigated by in situ hybridization. We observed marked decreases in the expression of HDACs 1, 2 and 11 (by up to 75%) in the granule cell and pyramidal cell layers of the hippocampus during the acute status epilepticus (2 to 6h after KA injection). This was followed by increased expression of all class I HDAC mRNAs in all principal cell layers of the hippocampus after 12 to 48 h. In the chronic phase, 14 and 28 days after KA, only modest increases in the expression of HDAC1 mRNA were observed in granule and pyramidal cells. Immunohistochemistry using an antibody detecting HDAC2 revealed results consistent with the mRNA data and indicates also expression in glial cells on the injection side. Similar changes as seen in the KA model were observed after a pilocarpine-induced status epilepticus except that decreases in HDACs 2, 3 and 8 were also seen at the chronic 28 day interval. The prominent decreases in HDAC expression during status epilepticus are consistent with the previously demonstrated increased expression of numerous proteins and with the augmented acetylation of histone H4. It is suggested that respective putative gene products could facilitate proconvulsive as well as anticonvulsive mechanisms. The increased expression of all class I HDACs during the "silent phase", on the other hand, may be related to decreased histone acetylation, which could cause a decrease in expression of certain proteins, a mechanism that could also promote epileptogenesis. Thus, addressing HDAC expression may have a therapeutic potential in interfering with a status epilepticus and with the manifestation of TLE.
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Affiliation(s)
- Rohan Jagirdar
- Department of Pharmacology, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Meinrad Drexel
- Department of Pharmacology, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Elke Kirchmair
- Department of Pharmacology, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Ramon O Tasan
- Department of Pharmacology, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Günther Sperk
- Department of Pharmacology, Medical University Innsbruck, 6020 Innsbruck, Austria.
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Puia G, Ravazzini F, Castelnovo LF, Magnaghi V. PKCε and allopregnanolone: functional cross-talk at the GABAA receptor level. Front Cell Neurosci 2015; 9:83. [PMID: 25852476 PMCID: PMC4365694 DOI: 10.3389/fncel.2015.00083] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 02/23/2015] [Indexed: 11/13/2022] Open
Abstract
Changes in GABAergic inhibition occur during physiological processes, during response to drugs and in various pathologies. These changes can be achieved through direct allosteric modifications at the γ-amino butyric acid (GABA) type A (GABAA) receptor protein level, or by altering the synthesis, trafficking and stability of the receptor. Neurosteroids (NSs) and protein kinase C (PKC) are potent modulators of GABAA receptors and their effects are presumably intermingled, even though evidence for this hypothesis is only partially explored. However, several PKC isoforms are able to phosphorylate the GABAA receptor, producing different functional effects. We focused on the ε isoform, that has been correlated to the sensitivity of the GABAA receptor to allosteric modulators and whose expression may be regulated in peripheral sensory neurons by NSs. The cross-talk between PKC-ε and NSs, leading to changes in GABAA receptor functionality, is considered and discussed in this perspective.
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Affiliation(s)
- Giulia Puia
- Department of Life Science, University of Modena and Reggio Emilia Modena, Italy
| | - Federica Ravazzini
- Department of Life Science, University of Modena and Reggio Emilia Modena, Italy
| | - Luca Franco Castelnovo
- Department of Pharmacological and Biomolecular Sciences, University of Milan Milan, Italy
| | - Valerio Magnaghi
- Department of Pharmacological and Biomolecular Sciences, University of Milan Milan, Italy
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Drexel M, Puhakka N, Kirchmair E, Hörtnagl H, Pitkänen A, Sperk G. Expression of GABA receptor subunits in the hippocampus and thalamus after experimental traumatic brain injury. Neuropharmacology 2014; 88:122-33. [PMID: 25229716 PMCID: PMC4239297 DOI: 10.1016/j.neuropharm.2014.08.023] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 08/26/2014] [Accepted: 08/28/2014] [Indexed: 12/12/2022]
Abstract
Traumatic brain injury is a major cause of death and disability worldwide and often associated with post-traumatic epilepsy. We recently demonstrated that TBI induces acquired GABAA receptors channelopathy that associates with hyperexcitability in granule cell layer (GCL). We now assessed the expression of GABAA and GABAB receptor subunit mRNAs between 6 h and 6 months post-TBI in the hippocampus and thalamus. The expression of major GABAA receptor subunit mRNAs (α1, α2, α5, β2, β3, γ2 and δ) was, often bilaterally, down-regulated in the GCL and in the CA3 pyramidal cells. Instead, expression of α4 (GCL, CA3, CA1), α5 (CA1) and γ2 (GCL, CA3, CA1) mRNA was up-regulated after 10 d and/or 4 months. Many of these changes were reversible. In the thalamus, we found decreases in α1, α4, β2, γ2 and δ mRNAs in the laterodorsal thalamus and in the area combining the posterior thalamic nuclear group, ventroposterolateral and ventroposteromedial complex at 6 h to 4 months post-TBI. Unlike in the hippocampus, thalamic subunit down-regulations were irreversible and limited to the ipsilateral side. However, contralaterally there was up-regulation of the subunits δ and α4 6 h and 4 months after TBI, respectively. PCR array analysis suggested a mild long-lasting GABAA receptor channelopathy in the GCL and thalamus after TBI. Whereas TBI induces transient changes in the expression of GABAA receptor subunits in the hippocampus (presumably representing compensatory mechanisms), alterations of GABAA receptor subunit mRNAs in the thalamus are long-lasting and related to degeneration of receptor-containing neurons in thalamo-cortical relay nuclei. This article is part of the Special Issue entitled ‘GABAergic Signaling in Health and Disease’. GABAA receptor subunits are permanently lost in thalamic nuclei on the side of TBI. They are only transiently decreased in hippocampal subfields bilaterally. Subunit α4 is up-regulated in the thalamus and hippocampus contralateral to TBI. Efficacy of neurosteroids in preventing secondary epilepsy after TBI is suggested.
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Affiliation(s)
- Meinrad Drexel
- Department of Pharmacology, Innsbruck Medical University, 6020 Innsbruck, Austria.
| | - Noora Puhakka
- Department of Neurobiology, A. I. Virtanen Institute for Molecular Science, University of Eastern Finland, PO Box 1627, FI-70211 Kuopio, Finland
| | - Elke Kirchmair
- Department of Pharmacology, Innsbruck Medical University, 6020 Innsbruck, Austria
| | - Heide Hörtnagl
- Department of Pharmacology, Innsbruck Medical University, 6020 Innsbruck, Austria
| | - Asla Pitkänen
- Department of Neurobiology, A. I. Virtanen Institute for Molecular Science, University of Eastern Finland, PO Box 1627, FI-70211 Kuopio, Finland; Department of Neurology, Kuopio University Hospital, PO Box 1777, FI-70211 Kuopio, Finland
| | - Günther Sperk
- Department of Pharmacology, Innsbruck Medical University, 6020 Innsbruck, Austria
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Grabenstatter HL, Cogswell M, Cruz Del Angel Y, Carlsen J, Gonzalez MI, Raol YH, Russek SJ, Brooks-Kayal AR. Effect of spontaneous seizures on GABAA receptor α4 subunit expression in an animal model of temporal lobe epilepsy. Epilepsia 2014; 55:1826-33. [PMID: 25223733 DOI: 10.1111/epi.12771] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/31/2014] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Temporal lobe epilepsy (TLE) is frequently medically intractable and often progressive. Compromised inhibitory neurotransmission due to altered γ-aminobutyric acid (GABA)A receptor α4 subunit (GABAA Rα4) expression has been emphasized as a potential contributor to the initial development of epilepsy following a brain insult (primary epileptogenesis), but the regulation of GABAA Rα4 during chronic epilepsy, specifically, how expression is altered following spontaneous seizures, is less well understood. METHODS Continuous video-electroencephalography (EEG) recordings from rats with pilocarpine-induced TLE were used to capture epileptic animals within 3 h of a spontaneous seizure (SS), or >24 h after the last SS, to determine whether recent occurrence of a seizure was associated with altered levels of GABAA Rα4 expression. We further evaluated whether this GABAA Rα4 plasticity is regulated by signaling mechanisms active in primary epileptogenesis, specifically, increases in brain-derived neurotrophic factor (BDNF) and early growth response factor 3 (Egr3). RESULTS Elevated levels of GABAA Rα4 messenger RNA (mRNA) and protein were observed following spontaneous seizures, and were associated with higher levels of BDNF and Egr3 mRNA. SIGNIFICANCE These data suggest that spontaneous, recurrent seizures that define chronic epilepsy may influence changes in GABAA Rα4 expression, and that signaling pathways known to regulate GABAA Rα4 expression after status epilepticus may also be activated after spontaneous seizures in chronically epileptic animals.
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Affiliation(s)
- Heidi L Grabenstatter
- Department of Pediatrics, Section of Neurology, Translational Epilepsy Research Program, University of Colorado, AMC, Aurora, Colorado, U.S.A
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Altered expression of δGABAA receptors in health and disease. Neuropharmacology 2014; 88:24-35. [PMID: 25128850 DOI: 10.1016/j.neuropharm.2014.08.003] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2014] [Revised: 07/28/2014] [Accepted: 08/03/2014] [Indexed: 01/08/2023]
Abstract
γ-Aminobutyric acid type A receptors that contain the δ subunit (δGABAA receptors) are expressed in multiple types of neurons throughout the central nervous system, where they generate a tonic conductance that shapes neuronal excitability and synaptic plasticity. These receptors regulate a variety of important behavioral functions, including memory, nociception and anxiety, and may also modulate neurogenesis. Given their functional significance, δGABAA receptors are considered to be novel therapeutic targets for the treatment of memory dysfunction, pain, insomnia and mood disorders. These receptors are highly responsive to sedative-hypnotic drugs, general anesthetics and neuroactive steroids. A further remarkable feature of δGABAA receptors is that their expression levels are highly dynamic and fluctuate substantially during development and in response to physiological changes including stress and the reproductive cycle. Furthermore, the expression of these receptors varies in pathological conditions such as alcoholism, fragile X syndrome, epilepsy, depression, schizophrenia, mood disorders and traumatic brain injury. Such fluctuations in receptor expression have significant consequences for behavior and may alter responsiveness to therapeutic drugs. This review considers the alterations in the expression of δGABAA receptors associated with various states of health and disease and the implications of these changes.
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Huusko N, Pitkänen A. Parvalbumin immunoreactivity and expression of GABAA receptor subunits in the thalamus after experimental TBI. Neuroscience 2014; 267:30-45. [DOI: 10.1016/j.neuroscience.2014.02.026] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 01/28/2014] [Accepted: 02/19/2014] [Indexed: 01/17/2023]
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Lee V, Maguire J. The impact of tonic GABAA receptor-mediated inhibition on neuronal excitability varies across brain region and cell type. Front Neural Circuits 2014; 8:3. [PMID: 24550784 PMCID: PMC3909947 DOI: 10.3389/fncir.2014.00003] [Citation(s) in RCA: 142] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Accepted: 01/08/2014] [Indexed: 01/19/2023] Open
Abstract
The diversity of GABAA receptor (GABAAR) subunits and the numerous configurations during subunit assembly give rise to a variety of receptors with different functional properties. This heterogeneity results in variations in GABAergic conductances across numerous brain regions and cell types. Phasic inhibition is mediated by synaptically-localized receptors with a low affinity for GABA and results in a transient, rapidly desensitizing GABAergic conductance; whereas, tonic inhibition is mediated by extrasynaptic receptors with a high affinity for GABA and results in a persistent GABAergic conductance. The specific functions of tonic versus phasic GABAergic inhibition in different cell types and the impact on specific neural circuits are only beginning to be unraveled. Here we review the diversity in the magnitude of tonic GABAergic inhibition in various brain regions and cell types, and highlight the impact on neuronal excitability in different neuronal circuits. Further, we discuss the relevance of tonic inhibition in various physiological and pathological contexts as well as the potential of targeting these receptor subtypes for treatment of diseases, such as epilepsy.
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Affiliation(s)
- Vallent Lee
- Medical Scientist Training Program and Graduate Program in Neuroscience, Sackler School of Graduate Biomedical Sciences, Tufts University Boston, MA, USA
| | - Jamie Maguire
- Department of Neuroscience, Tufts University School of Medicine Boston, MA, USA
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Galanopoulou AS, Moshé SL. Does epilepsy cause a reversion to immature function? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 813:195-209. [PMID: 25012378 DOI: 10.1007/978-94-017-8914-1_16] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Seizures have variable effects on brain. Numerous studies have examined the consequences of seizures, in light of the way that these may alter the susceptibility of the brain to seizures, promote epileptogenesis, or functionally alter brain leading to seizure-related comorbidities. In many -but not all- situations, seizures shift brain function towards a more immature state, promoting the birth of newborn neurons, altering the dendritic structure and neuronal connectivity, or changing neurotransmitter signaling towards more immature patterns. These effects depend upon many factors, including the seizure type, age of seizure occurrence, sex, and brain region studied. Here we discuss some of these findings proposing that these seizure-induced immature features do not simply represent rejuvenation of the brain but rather a de-synchronization of the homeostatic mechanisms that were in place to maintain normal physiology, which may contribute to epileptogenesis or the cognitive comorbidities.
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Affiliation(s)
- Aristea S Galanopoulou
- Saul R. Korey Department of Neurology, Dominick P. Purpura Department of Neuroscience, The Laboratory of Developmental Epilepsy, Comprehensive Einstein/Montefiore Epilepsy Center, Albert Einstein College of Medicine, 1410 Pelham Parkway South, Kennedy Center Rm 306, Bronx, NY, 10461, USA,
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Are alterations in transmitter receptor and ion channel expression responsible for epilepsies? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 813:211-29. [PMID: 25012379 DOI: 10.1007/978-94-017-8914-1_17] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Neuronal voltage-gated ion channels and ligand-gated synaptic receptors play a critical role in maintaining the delicate balance between neuronal excitation and inhibition within neuronal networks in the brain. Changes in expression of voltage-gated ion channels, in particular sodium, hyperpolarization-activated cyclic nucleotide-gated (HCN) and calcium channels, and ligand-gated synaptic receptors, in particular GABA and glutamate receptors, have been reported in many types of both genetic and acquired epilepsies, in animal models and in humans. In this chapter we review these and discuss the potential pathogenic role they may play in the epilepsies.
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Altered localization of the δ subunit of the GABAA receptor in the thalamus of α4 subunit knockout mice. Neurochem Res 2013; 39:1104-17. [PMID: 24352815 DOI: 10.1007/s11064-013-1202-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Revised: 11/05/2013] [Accepted: 11/13/2013] [Indexed: 10/25/2022]
Abstract
The α4 subunit of the GABAA receptor (GABAAR) is highly expressed in the thalamus where receptors containing the α4 and δ subunits are major mediators of tonic inhibition. The α4 subunit also exhibits considerable plasticity in a number of physiological and pathological conditions, raising questions about the expression of remaining GABAAR subunits when the α4 subunit is absent. Immunohistochemical studies of an α4 subunit knockout (KO) mouse revealed a substantial decrease in δ subunit expression in the ventrobasal nucleus of the thalamus as well as other forebrain regions where the α4 subunit is normally expressed. In contrast, several subunits associated primarily with phasic inhibition, including the α1 and γ2 subunits, were moderately increased. Intracellular localization of the δ subunit was also altered. While δ subunit labeling was decreased within the neuropil, some labeling remained in the cell bodies of many neurons in the ventrobasal nucleus. Confocal microscopy demonstrated co-localization of this labeling with an endoplasmic reticulum marker, and electron microscopy demonstrated increased immunogold labeling near the endoplasmic reticulum in the α4 KO mouse. These results emphasize the strong partnership of the δ and α4 subunit in the thalamus and suggest that the α4 subunit of the GABAAR plays a critical role in trafficking of the δ subunit to the neuronal surface. The findings also suggest that previously observed reductions in tonic inhibition in the α4 subunit KO mouse are likely to be related to alterations in δ subunit expression, in addition to loss of the α4 subunit.
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Li ZX, Yu HM, Jiang KW. Tonic GABA inhibition in hippocampal dentate granule cells: its regulation and function in temporal lobe epilepsies. Acta Physiol (Oxf) 2013; 209:199-211. [PMID: 23865761 DOI: 10.1111/apha.12148] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Revised: 05/06/2013] [Accepted: 07/12/2013] [Indexed: 01/06/2023]
Abstract
Both human and experimental evidence strongly supports the view of brain region- and cell-specific changes in tonic GABA inhibition in temporal lobe epilepsies (TLE). This 'tonic' form of signalling is not time-locked to presynaptic action potentials, which depends upon detection of ambient GABA by extrasynaptic GABAA receptors (GABAA Rs). Extrasynaptic GABAA Rs have distinct physiological and pharmacological features, including high GABA-binding affinity and low desensitization and a variety of the specific subunit combinations (α4δ-,α6δ-,α5γ-,ε-containing receptors). These features closely contribute to the function of tonic GABA current, which is preserved properly or increased in dentate gyrus in models of TLE, even in the face of a loss of synaptic inhibition and inhibitory interneurones. Markedly reduced tonic GABA inhibition may facilitate an episode of epilepsy, while persistent elevated tonic inhibition may contribute to the onset of spontaneous recurrent seizures. In dentate granule cells, tonic GABA inhibition is positively modulated by endogenous neurosteroids and other factors, which undergo changes related to hormonal status after TLE. Tonic inhibition regulates neuronal excitability through its effects on membrane potential by both offsetting the threshold and reducing the frequency of action potentials and input resistance. Therefore, extrasynaptic GABAA Rs are expected to be the most important pharmacological targets in TLE. It is likely that both elevate the ambient GABA concentration and potentiate the tonic currents, contributing to the antiepileptic effects.
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Affiliation(s)
- Z.-X. Li
- Department of Neurology; The Children's Hospital Zhejiang University School of Medicine; Hangzhou; China
| | - H.-M. Yu
- Department of Neonatology; The Children's Hospital Zhejiang University School of Medicine; Hangzhou; China
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Drexel M, Kirchmair E, Sperk G. Changes in the expression of GABAA receptor subunit mRNAs in parahippocampal areas after kainic acid induced seizures. Front Neural Circuits 2013; 7:142. [PMID: 24065890 PMCID: PMC3776158 DOI: 10.3389/fncir.2013.00142] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Accepted: 08/24/2013] [Indexed: 11/30/2022] Open
Abstract
The parahippocampal areas including the subiculum, pre- and parasubiculum, and notably the entorhinal cortex (EC) are intimately involved in the generation of limbic seizures in temporal lobe epilepsy. We investigated changes in the expression of 10 major GABAA receptor subunit mRNAs in subfields of the ventral hippocampus, ventral subiculum, EC, and perirhinal cortex (PRC) at different intervals (1, 8, 30, and 90 days) after kainic acid (KA)-induced status epilepticus priming epileptogenesis in the rat. The most pronounced and ubiquitous changes were a transient (24 h after KA only) down-regulation of γ2 mRNA and lasting decreases in subunit α5, β3, and δ mRNAs that were prominent in all hippocampal and parahippocampal areas. In the subiculum similarly as in sectors CA1 and CA3, levels of subunit α1, α2, α4, and γ2 mRNAs decreased transiently (1 day after KA-induced status epilepticus). They were followed by increased expression of subunit α1 and α3 mRNAs in the dentate gyrus (DG) and sectors CA1 and CA3, and subunit α1 also in the EC layer II (30 and 90 days after KA). We also observed sustained overexpression of subunits α4 and γ2 in the subiculum and in the Ammon’s horn. Subunit γ2 mRNA was also increased in sector CA1 at the late intervals after KA. Taken together, our results suggest distinct regulation of mRNA expression for individual GABAA receptor subunits. Especially striking was the wide-spread down-regulation of the often peri- or extrasynaptically located subunits α5 and δ. These subunits are often associated with tonic inhibition. Their decrease could be related to decreased tonic inhibition or may merely reflect compensatory changes. In contrast, expression of subunit α4 that may also mediate tonic inhibition when associated with the δ-subunit was significantly upregulated in the DG and in the proximal subiculum at late intervals. Thus, concomitant up-regulation of subunit γ2, α1 and α4 mRNAs (and loss in δ-subunits) ultimately indicates significant rearrangement of GABAA receptor composition after KA-induced seizures.
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Affiliation(s)
- Meinrad Drexel
- Department of Pharmacology, Innsbruck Medical University Innsbruck, Austria
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Milenkovic I, Vasiljevic M, Maurer D, Höger H, Klausberger T, Sieghart W. The parvalbumin-positive interneurons in the mouse dentate gyrus express GABAA receptor subunits α1, β2, and δ along their extrasynaptic cell membrane. Neuroscience 2013; 254:80-96. [PMID: 24055402 DOI: 10.1016/j.neuroscience.2013.09.019] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2013] [Revised: 08/27/2013] [Accepted: 09/09/2013] [Indexed: 11/17/2022]
Abstract
Neuronal circuitries in the hippocampus are involved in navigation and memory and are controlled by major networks of GABAergic interneurons. Parvalbumin (PV)-expressing interneurons in the dentate gyrus (DG) are identified as fast-spiking cells, playing a crucial role in network oscillation and synchrony. The inhibitory modulation of these interneurons is thought to be mediated mainly through GABAA receptors, the major inhibitory neurotransmitter receptors in the brain. Here we show that all PV-positive interneurons in the granular/subgranular layer (GL/SGL) of the mouse DG express high levels of the GABAA receptor δ subunit. PV-containing interneurons in the hilus and the molecular layer, however, express the δ subunit to a lower extent. Only 8% of the somatostatin-containing interneurons express the δ subunit, whereas calbindin- or calretinin-containing interneurons in the DG seem not to express the GABAA receptor δ subunit at all. Hence, these cells receive a GABAergic control different from that of PV-containing interneurons in the GL/SGL. Experiments investigating a possible co-expression of GABAA receptor α1, α2, α3, α4, α5, β1, β2, β3, or γ2 subunits with PV and δ subunits indicated that α1 and β2 subunits are co-expressed with δ subunits along the extrasynaptic membranes of PV-interneurons. These results suggest a robust tonic GABAergic control of PV-containing interneurons in the GL/SGL of the DG via δ subunit-containing receptors. Our data are important for better understanding of the neuronal circuitries in the DG and the role of specific cell types under pathological conditions.
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Affiliation(s)
- I Milenkovic
- Center for Brain Research, Department of Biochemistry and Molecular Biology of the Nervous System, Medical University of Vienna, Spitalgasse 4, 1090 Vienna, Austria; Institute of Neurology, Medical University of Vienna, Währinger Gürtel 18-20, 1097 Vienna, Austria.
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Sun C, Sun J, Erisir A, Kapur J. Loss of cholecystokinin-containing terminals in temporal lobe epilepsy. Neurobiol Dis 2013; 62:44-55. [PMID: 24051276 DOI: 10.1016/j.nbd.2013.08.018] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 08/22/2013] [Accepted: 08/27/2013] [Indexed: 11/30/2022] Open
Abstract
Altered GABA-mediated inhibition is proposed to play a role in the pathogenesis of epilepsy. Previous studies have demonstrated a loss of somatostatin-containing GABAergic interneurons innervating granule cells in epileptic animals. However, the reorganization of synapses between interneurons and granule cells has not been investigated. We studied synapse organization in an animal model of temporal lobe epilepsy (TLE) using continuous hippocampal stimulation. The distribution of axon terminals and inhibitory synapses on granule cell dendrites was studied using a combination of immunohistochemistry and pre-embedding electron microscopy techniques. A whole-cell patch-clamp technique was applied to study the functional changes in GABAergic input from different interneurons. In epileptic animals, the density of cholecystokinin (CCK)-immunoreactive (IR) fibers and α2 subunit containing GABAA receptors in the inner molecular layer of the dentate gyrus was reduced. Quantitative immuno-electron microscopy study revealed that the ratio of CCK-containing symmetric synapses to the total symmetric synapses was reduced. The frequency of GABAergic synaptic currents (sIPSC) was decreased and their amplitude was increased. The inhibitory effect of the activation of cannabinoid 1 (CB1) receptors was also reduced in epileptic animals. Isolation of CCK- and parvalbumin (PV)-containing GABAergic inputs by N- and P/Q-type calcium channel blockers respectively suggested that GABA release from CCK-containing interneurons was selectively reduced in epileptic rats. This study found that there was a loss of CCK-containing GABAergic synapses to granule cells both morphologically and functionally. These studies add to our understanding of the mechanisms that contribute to altering GABAergic inhibition of granule cells in TLE.
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Affiliation(s)
- Chengsan Sun
- Department of Neurology, University of Virginia, Health Sciences Center, PO Box 800394, Charlottesville, VA 22908, USA; Department of Psychology, University of Virginia, PO Box 400400, Charlottesville, VA 22904, USA
| | - Jianli Sun
- Department of Neurology, University of Virginia, Health Sciences Center, PO Box 800394, Charlottesville, VA 22908, USA
| | - Alev Erisir
- Department of Psychology, University of Virginia, PO Box 400400, Charlottesville, VA 22904, USA
| | - Jaideep Kapur
- Department of Neurology, University of Virginia, Health Sciences Center, PO Box 800394, Charlottesville, VA 22908, USA; Department of Neuroscience, PO Box 801392, Charlottesville, VA 22908, USA.
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González MI. The possible role of GABAA receptors and gephyrin in epileptogenesis. Front Cell Neurosci 2013; 7:113. [PMID: 23885234 PMCID: PMC3717475 DOI: 10.3389/fncel.2013.00113] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Accepted: 06/26/2013] [Indexed: 12/29/2022] Open
Abstract
The term epileptogenesis refers to a dynamic alteration in neuronal excitability that promotes the appearance of spontaneous seizures. Temporal lobe epilepsy, the most common type of acquired epilepsy, often develops after an insult to the brain such as trauma, febrile seizures, encephalitis, or status epilepticus. During the pre-epileptic state (also referred as latent or silent period) there is a plethora of molecular, biochemical, and structural changes that lead to the generation of recurrent spontaneous seizures (or epilepsy). The specific contribution of these alterations to epilepsy development is unclear, but a loss of inhibition has been associated with the increased excitability detected in the latent period. A rapid increase in neuronal hyperexcitability could be due, at least in part, to a decline in the number of physiologically active GABAA receptors (GABAAR). Altered expression of scaffolding proteins involved in the trafficking and anchoring of GABAAR could directly impact the stability of GABAergic synapses and promote a deficiency in inhibitory neurotransmission. Uncovering the molecular mechanisms operating during epileptogenesis and its possible impact on the regulation of GABAAR and scaffolding proteins may offer new targets to prevent the development of epilepsy.
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Affiliation(s)
- Marco I González
- Division of Neurology and Translational Epilepsy Research Program, Department of Pediatrics, University of Colorado School of Medicine Aurora, CO, USA
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Cifelli P, Palma E, Roseti C, Verlengia G, Simonato M. Changes in the sensitivity of GABAA current rundown to drug treatments in a model of temporal lobe epilepsy. Front Cell Neurosci 2013; 7:108. [PMID: 23874269 PMCID: PMC3708152 DOI: 10.3389/fncel.2013.00108] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Accepted: 06/21/2013] [Indexed: 01/26/2023] Open
Abstract
The pharmacological treatment of mesial temporal lobe epilepsy (mTLE), the most common epileptic syndrome in adults, is still unsatisfactory, as one-third of the patients are or become refractory to antiepileptic agents. Refractoriness may depend upon drug-induced alterations, but the disease per se may also undergo a progressive evolution that affects the sensitivity to drugs. mTLE has been shown to be associated with a dysfunction of the inhibitory signaling mediated by GABAA receptors. In particular, the repetitive activation of GABAA receptors produces a use-dependent decrease (rundown) of the evoked currents (IGABA), which is markedly enhanced in the hippocampus and cortex of drug-resistant mTLE patients. This phenomenon has been also observed in the pilocarpine model, where the increased IGABA rundown is observed in the hippocampus at the time of the first spontaneous seizure, then extends to the cortex and remains constant in the chronic phase of the disease. Here, we examined the sensitivity of IGABA to pharmacological modulation. We focused on the antiepileptic agent levetiracetam (LEV) and on the neurotrophin brain-derived neurotrophic factor (BDNF), which were previously reported to attenuate mTLE-induced increased rundown in the chronic human tissue. In the pilocarpine model, BDNF displayed a paramount effect, decreasing rundown in the hippocampus at the time of the first seizure, as well as in the hippocampus and cortex in the chronic period. In contrast, LEV did not affect rundown in the hippocampus, but attenuated it in the cortex. Interestingly, this effect of LEV was also observed on the still unaltered rundown observed in the cortex at the time of the first spontaneous seizure. These data suggest that the sensitivity of GABAA receptors to pharmacological interventions undergoes changes during the natural history of mTLE, implicating that the site of seizure initiation and the timing of treatment may highly affect the therapeutic outcome.
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Affiliation(s)
- Pierangelo Cifelli
- Section of Pharmacology, Department of Medical Sciences, University of Ferrara Ferrara, Italy ; National Institute of Neuroscience Ferrara, Italy ; Ri.MED Foundation Palermo, Italy
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Pandit S, Jeong JA, Jo JY, Cho HS, Kim DW, Kim JM, Ryu PD, Lee SY, Kim HW, Jeon BH, Park JB. Dual mechanisms diminishing tonic GABAA inhibition of dentate gyrus granule cells in Noda epileptic rats. J Neurophysiol 2013; 110:95-102. [PMID: 23576696 DOI: 10.1152/jn.00727.2012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The Noda epileptic rat (NER), a Wistar colony mutant, spontaneously has tonic-clonic convulsions with paroxysmal discharges. In the present study, we measured phasic and tonic γ-aminobutyric acid A (GABAA) current (I tonic) in NER hippocampal dentate gyrus granule cells and compared the results with those of normal parent strain Wistar rats (WIS). I tonic, revealed by a bicuculline-induced outward shift in holding current, was significantly smaller in NER than in WIS (P < 0.01). The frequency of inhibitory postsynaptic currents (IPSCs) was also significantly lower in NER than in WIS (P < 0.05), without significant differences in the IPSC amplitude or decay time between WIS and NER. I tonic attenuation in NER was further confirmed in the presence of GABA transporter blockers, NO-711 and nipecotic acid, with no difference in neuronal GABA transporter expression between WIS and NER. I tonic responses to extrasynaptic GABAA receptor agonists (THIP and DS-2) were significantly reduced in NER compared with WIS (P < 0.05). Allopregnanolone caused less I tonic increase in NER than in WIS, while it prolonged the IPSC decay time to a similar rate in the two groups. Expression of the GABAA receptor δ-subunit was decreased in the dentate gyrus of NER relative to that of WIS. Taken together, our results showed that a combination of attenuated presynaptic GABA release and extrasynaptic GABAA receptor expression reduced I tonic amplitude and its sensitivity to neurosteroids, which likely diminishes the gating function of dentate gyrus granule cells and renders NER more susceptible to seizure propagation.
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Affiliation(s)
- Sudip Pandit
- Department of Physiology, School of Medicine and Brain Research Institute, Chungnam National University, Daejeon, South Korea
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González MI, Cruz Del Angel Y, Brooks-Kayal A. Down-regulation of gephyrin and GABAA receptor subunits during epileptogenesis in the CA1 region of hippocampus. Epilepsia 2013; 54:616-24. [PMID: 23294024 DOI: 10.1111/epi.12063] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/29/2012] [Indexed: 12/22/2022]
Abstract
PURPOSE Epileptogenesis is the process by which a brain becomes hyperexcitable and capable of generating recurrent spontaneous seizures. In humans, it has been hypothesized that following a brain insult there are a number of molecular and cellular changes that underlie the development of spontaneous seizures. Studies in animal models have shown that an injured brain may develop epileptiform activity before appearance of epileptic seizures and that the pathophysiology accompanying spontaneous seizures is associated with a dysfunction of γ-aminobutyric acid (GABA)ergic neurotransmission. Here, we analyzed the effects of status epilepticus on the expression of GABAA receptors (GABAA Rs) and scaffolding proteins involved in the regulation of GABAA R trafficking and anchoring. METHODS Western blot analysis was used to determine the levels of proteins involved in GABAA R trafficking and anchoring in adult rats subjected to pilocarpine-induced status epilepticus (SE) and controls. Cell surface biotinylation using a cell membrane-impermeable reagent was used to assay for changes in the expression of receptors at the plasma membrane. Finally, immunoprecipitation experiments were used to evaluate the composition of GABAA Rs. We examined for a correlation between total GABAA R subunit expression, plasma membrane expression, and receptor composition. KEY FINDINGS Analysis of tissue samples from the CA1 region of hippocampus show that SE promotes a loss of GABAA R subunits and of the scaffolding proteins associated with them. We also found a decrease in the levels of receptors located at the plasma membrane and alterations in GABAA R composition. SIGNIFICANCE The changes in protein expression of GABAA Rs and scaffolding proteins detected in these studies provide a potential mechanism to explain the deficits in GABAergic neurotransmission observed during the epileptogenic period. Our current observations represent an additional step toward the elucidation of the molecular mechanisms underlying GABAA R dysfunction during epileptogenesis.
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Affiliation(s)
- Marco I González
- Division of Neurology and Translational Epilepsy Research Program, Department of Pediatrics, University of Colorado School of Medicine, Aurora, Colorado, USA.
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Ferando I, Mody I. GABAAreceptor modulation by neurosteroids in models of temporal lobe epilepsies. Epilepsia 2012; 53 Suppl 9:89-101. [DOI: 10.1111/epi.12038] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Swijsen A, Avila A, Brône B, Janssen D, Hoogland G, Rigo JM. Experimental early-life febrile seizures induce changes in GABA(A) R-mediated neurotransmission in the dentate gyrus. Epilepsia 2012; 53:1968-77. [PMID: 23030508 DOI: 10.1111/j.1528-1167.2012.03694.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
PURPOSE Febrile seizures (FS), the most frequent seizure type during childhood, have been linked to temporal lobe epilepsy (TLE) in adulthood. Yet, underlying mechanisms are still largely unknown. Altered γ-aminobutyric acid (GABA)ergic neurotransmission in the dentate gyrus (DG) circuit has been hypothesized to be involved. This study aims at analyzing whether experimental FS change inhibitory synaptic input and postsynaptic GABA(A) R function in dentate granule cells. METHODS We applied an immature rat model of hyperthermia (HT)-induced FS. GABA(A) R-mediated neurotransmission was studied using whole-cell patch-clamp recordings from dentate granule neurons in hippocampal slices within 6-9 days post-HT. KEY FINDINGS Frequencies of spontaneous inhibitory postsynaptic currents (sIPSCs) were reduced in HT rats that had experienced seizures, whereas sIPSC amplitudes were enhanced. Whole-cell GABA responses revealed a doubled GABA(A) R sensitivity in dentate granule cells from HT animals, compared to that of normothermic (NT) controls. Analysis of sIPSCs and whole-cell GABA responses showed similar kinetics in postsynaptic GABA(A) Rs of HT and NT rats. quantitative real-time polymerase chain reaction (qPCR) experiments indicated changes in DG GABA(A) R subunit expression, which was most pronounced for the α3 subunit. SIGNIFICANCE The data support the hypothesis that FS persistently alter neuronal excitability.
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Affiliation(s)
- Ann Swijsen
- BIOMED Research Institute, Hasselt University/Transnational University Limburg, Diepenbeek, Belgium
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Swijsen A, Brône B, Rigo JM, Hoogland G. Long-lasting enhancement of GABA(A) receptor expression in newborn dentate granule cells after early-life febrile seizures. Dev Neurobiol 2012; 72:1516-27. [PMID: 22378685 DOI: 10.1002/dneu.22016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Revised: 02/06/2012] [Accepted: 02/23/2012] [Indexed: 02/05/2023]
Abstract
Febrile seizures (FS) are the most common type of seizures in childhood and are suggested to play a role in the development of temporal lobe epilepsy (TLE). Animal studies demonstrated that experimental FS induce a long-lasting change in hippocampal excitability, resulting in enhanced seizure susceptibility. Hippocampal neurogenesis and altered ion channel expression have both been proposed as mechanisms underlying this decreased seizure threshold. The present study aimed to analyze whether dentate gyrus (DG) cells that were born after FS and matured for 8 weeks display an altered repertoire of ligand-gated ion channels. To this end, we applied an established model, in which FS are elicited in 10-day-old rat pups by hyperthermia (HT). Normothermia littermates served as controls. From postnatal day 11 (P11) to P16, rats were injected with bromodeoxyuridine (BrdU) to label dividing cells immediately following FS. At P66, we evaluated BrdU-labeled DG cells for coexpression with γ-aminobutyric acid-type A receptors (GABA(A)Rs) and N-methyl-D-aspartate receptors (NMDARs). In control animals, 40% of BrdU-labeled cells coexpressed GABA(A)R β2/3, whereas in rats that had experienced FS, 60% of BrdU-labeled cells also expressed GABA(A)R β2/3. The number of BrdU-NMDAR NR2A/B coexpressing cells was in both groups about 80% of BrdU-labeled cells. The results demonstrate that developmental seizures cause a long-term increase in GABA(A)R β2/3 expression in newborn DG cells. This may affect hippocampal physiology.
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Affiliation(s)
- Ann Swijsen
- Research Group Cell Physiology, BIOMED Research Institute, Hasselt University, Diepenbeek, Belgium
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Pavlov I, Walker MC. Tonic GABA(A) receptor-mediated signalling in temporal lobe epilepsy. Neuropharmacology 2012; 69:55-61. [PMID: 22538087 DOI: 10.1016/j.neuropharm.2012.04.003] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Revised: 03/27/2012] [Accepted: 04/02/2012] [Indexed: 11/25/2022]
Abstract
The tonic activation of extrasynaptic GABAA receptors by extracellular GABA provides a powerful means of regulating neuronal excitability. A consistent finding from studies that have used various models of temporal lobe epilepsy is that tonic GABAA receptor-mediated conductances are largely preserved in epileptic brain (in contrast to synaptic inhibition which is often reduced). Tonic inhibition is therefore an attractive target for antiepileptic drugs. However, the network consequences of a commonly used approach to augment tonic GABAA receptor-mediated conductances by global manipulation of extracellular GABA are difficult to predict without understanding how epileptogenesis alters the pharmacology and GABA sensitivity of tonic inhibition, and how manipulation of tonic conductances modulates the output of individual neurons. Here we review the current literature on epilepsy-associated changes in tonic GABAA receptor-mediated signalling, and speculate about possible effects they have at the network level. This article is part of the Special Issue entitled 'New Targets and Approaches to the Treatment of Epilepsy'.
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Affiliation(s)
- Ivan Pavlov
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London WC1N3BG, UK.
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