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Alpay B, Cimen B, Akaydin E, Onat F, Bolay H, Sara Y. Extrasynaptic δGABAA receptors mediate resistance to migraine-like phenotype in rats. J Headache Pain 2024; 25:75. [PMID: 38724972 PMCID: PMC11083752 DOI: 10.1186/s10194-024-01777-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2024] [Accepted: 04/22/2024] [Indexed: 05/12/2024] Open
Abstract
BACKGROUND GABA, a key inhibitory neurotransmitter, has synaptic and extrasynaptic receptors on the postsynaptic neuron. Background GABA, which spills over from the synaptic cleft, acts on extrasynaptic delta subunit containing GABAA receptors. The role of extrasynaptic GABAergic input in migraine is unknown. We investigated the susceptibility to valid migraine-provoking substances with clinically relevant behavioral readouts in Genetic Absence Epilepsy of Rats Strasbourg (GAERS), in which the GABAergic tonus was altered. Subsequently, we screened relevant GABAergic mechanisms in Wistar rats by pharmacological means to identify the mechanisms. METHODS Wistar and GAERS rats were administered nitroglycerin (10 mg/kg) or levcromakalim (1 mg/kg). Mechanical allodynia and photophobia were assessed using von Frey monofilaments and a dark-light box. Effects of GAT-1 blocker tiagabine (5 mg/kg), GABAB receptor agonist baclofen (2 mg/kg), synaptic GABAA receptor agonist diazepam (1 mg/kg), extrasynaptic GABAA receptor agonists gaboxadol (4 mg/kg), and muscimol (0.75 mg/kg), T-type calcium channel blocker ethosuximide (100 mg/kg) or synaptic GABAA receptor antagonist flumazenil (15 mg/kg) on levcromakalim-induced migraine phenotype were screened. RESULTS Unlike Wistar rats, GAERS exhibited no reduction in mechanical pain thresholds or light aversion following nitroglycerin or levcromakalim injection. Ethosuximide did not reverse the resistant phenotype in GAERS, excluding the role of T-type calcium channel dysfunction in this phenomenon. Tiagabine prevented levcromakalim-induced mechanical allodynia in Wistar rats, suggesting a key role in enhanced GABA spillover. Baclofen did not alleviate mechanical allodynia. Diazepam failed to mitigate levcromakalim-induced migraine phenotype. Additionally, the resistant phenotype in GAERS was not affected by flumazenil. Extrasynaptic GABAA receptor agonists gaboxadol and muscimol inhibited periorbital allodynia in Wistar rats. CONCLUSION Our study introduced a rat strain resistant to migraine-provoking agents and signified a critical involvement of extrasynaptic δGABAergic receptors. Extrasynaptic δ GABAA receptors, by mediating constant background inhibition on the excitability of neurons, stand as a novel drug target with a therapeutic potential in migraine.
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Affiliation(s)
- Berkay Alpay
- Department of Medical Pharmacology, Faculty of Medicine, Hacettepe University, Sihhiye, Ankara, 06320, Türkiye
- Neuroscience and Neurotechnology Excellence Joint Application and Research Center (NÖROM), Ankara, 06560, Türkiye
| | - Bariscan Cimen
- Department of Medical Pharmacology, Faculty of Medicine, Hacettepe University, Sihhiye, Ankara, 06320, Türkiye
- Neuroscience and Neurotechnology Excellence Joint Application and Research Center (NÖROM), Ankara, 06560, Türkiye
| | - Elif Akaydin
- Department of Medical Pharmacology, Faculty of Medicine, Hacettepe University, Sihhiye, Ankara, 06320, Türkiye
- Neuroscience and Neurotechnology Excellence Joint Application and Research Center (NÖROM), Ankara, 06560, Türkiye
| | - Filiz Onat
- Department of Medical Pharmacology, Faculty of Medicine, Acibadem Mehmet Ali Aydinlar University, Istanbul, 34752, Türkiye
| | - Hayrunnisa Bolay
- Neuroscience and Neurotechnology Excellence Joint Application and Research Center (NÖROM), Ankara, 06560, Türkiye.
- Department of Neurology and Algology, Faculty of Medicine, Gazi University, Besevler, Ankara, 06560, Türkiye.
| | - Yildirim Sara
- Department of Medical Pharmacology, Faculty of Medicine, Hacettepe University, Sihhiye, Ankara, 06320, Türkiye.
- Neuroscience and Neurotechnology Excellence Joint Application and Research Center (NÖROM), Ankara, 06560, Türkiye.
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Studtmann C, Ladislav M, Safari M, Khondaker R, Chen Y, Vaughan GA, Topolski MA, Tomović E, Balík A, Swanger SA. Ventral posterolateral and ventral posteromedial thalamocortical neurons have distinct physiological properties. J Neurophysiol 2023; 130:1492-1507. [PMID: 37937368 PMCID: PMC11068404 DOI: 10.1152/jn.00525.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Revised: 10/09/2023] [Accepted: 11/01/2023] [Indexed: 11/09/2023] Open
Abstract
Somatosensory information is propagated from the periphery to the cerebral cortex by two parallel pathways through the ventral posterolateral (VPL) and ventral posteromedial (VPM) thalamus. VPL and VPM neurons receive somatosensory signals from the body and head, respectively. VPL and VPM neurons may also receive cell type-specific GABAergic input from the reticular nucleus of the thalamus. Although VPL and VPM neurons have distinct connectivity and physiological roles, differences in their functional properties remain unclear as they are often studied as one ventrobasal thalamus neuron population. Here, we directly compared synaptic and intrinsic properties of VPL and VPM neurons in C57Bl/6J mice of both sexes aged P25-P32. VPL neurons showed greater depolarization-induced spike firing and spike frequency adaptation than VPM neurons. VPL and VPM neurons fired similar numbers of spikes during hyperpolarization rebound bursts, but VPM neurons exhibited shorter burst latency compared with VPL neurons, which correlated with larger sag potential. VPM neurons had larger membrane capacitance and more complex dendritic arbors. Recordings of spontaneous and evoked synaptic transmission suggested that VPL neurons receive stronger excitatory synaptic input, whereas inhibitory synapse strength was stronger in VPM neurons. This work indicates that VPL and VPM thalamocortical neurons have distinct intrinsic and synaptic properties. The observed functional differences could have important implications for their specific physiological and pathophysiological roles within the somatosensory thalamocortical network.NEW & NOTEWORTHY This study revealed that somatosensory thalamocortical neurons in the VPL and VPM have substantial differences in excitatory synaptic input and intrinsic firing properties. The distinct properties suggest that VPL and VPM neurons could process somatosensory information differently and have selective vulnerability to disease. This work improves our understanding of nucleus-specific neuron function in the thalamus and demonstrates the critical importance of studying these parallel somatosensory pathways separately.
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Affiliation(s)
- Carleigh Studtmann
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
- Graduate Program in Translational Biology, Medicine, and Health, Virginia Tech, Blacksburg, Virginia, United States
| | - Marek Ladislav
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
| | - Mona Safari
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
- Graduate Program in Translational Biology, Medicine, and Health, Virginia Tech, Blacksburg, Virginia, United States
| | - Rabeya Khondaker
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
- Graduate Program in Translational Biology, Medicine, and Health, Virginia Tech, Blacksburg, Virginia, United States
| | - Yang Chen
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
- Graduate Program in Translational Biology, Medicine, and Health, Virginia Tech, Blacksburg, Virginia, United States
| | - Grace A Vaughan
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
- Department of Human Nutrition, Foods, and Exercise, Virginia Tech, Blacksburg, Virginia, United States
| | - Mackenzie A Topolski
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
| | - Eni Tomović
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
- Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
| | - Aleš Balík
- Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
| | - Sharon A Swanger
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, Virginia, United States
- Department of Internal Medicine, Virginia Tech Carilion School of Medicine, Roanoke, Virginia, United States
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Altered GABA A Receptor Expression in the Primary Somatosensory Cortex of a Mouse Model of Genetic Absence Epilepsy. Int J Mol Sci 2022; 23:ijms232415685. [PMID: 36555327 PMCID: PMC9778655 DOI: 10.3390/ijms232415685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 11/26/2022] [Accepted: 12/07/2022] [Indexed: 12/14/2022] Open
Abstract
Absence seizures are hyperexcitations within the cortico-thalamocortical (CTC) network, however the underlying causative mechanisms at the cellular and molecular level are still being elucidated and appear to be multifactorial. Dysfunctional feed-forward inhibition (FFI) is implicated as one cause of absence seizures. Previously, we reported altered excitation onto parvalbumin-positive (PV+) interneurons in the CTC network of the stargazer mouse model of absence epilepsy. In addition, downstream changes in GABAergic neurotransmission have also been identified in this model. Our current study assessed whether dysfunctional FFI affects GABAA receptor (GABAAR) subunit expression in the stargazer primary somatosensory cortex (SoCx). Global tissue expression of GABAAR subunits α1, α3, α4, α5, β2, β3, γ2 and δ were assessed using Western blotting (WB), while biochemically isolated subcellular fractions were assessed for the α and δ subunits. We found significant reductions in tissue and synaptic expression of GABAAR α1, 18% and 12.2%, respectively. However, immunogold-cytochemistry electron microscopy (ICC-EM), conducted to assess GABAAR α1 specifically at synapses between PV+ interneurons and their targets, showed no significant difference. These data demonstrate a loss of phasic GABAAR α1, indicating altered GABAergic inhibition which, coupled with dysfunctional FFI, could be one mechanism contributing to the generation or maintenance of absence seizures.
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Vlachou S. A Brief History and the Significance of the GABA B Receptor. Curr Top Behav Neurosci 2021; 52:1-17. [PMID: 34595739 DOI: 10.1007/7854_2021_264] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the brain. GABA type B (GABAB) receptors (GABABRs) are the only metabotropic G protein-coupled receptors for GABA and can be found distributed not only in the central nervous system, but also in the periphery. This chapter introduces important, fundamental knowledge related to GABABR function and the various potential therapeutic applications of the development of novel GABABR-active compounds, as documented through extensive studies presented in subsequent chapters of this Current Topic in Behavioral Neurosciences volume on the role of the neurobiology of GABABR function. The compounds that have received increased attention in the last few years compared to GABABR agonists and antagonists - the positive allosteric modulators - exhibit better pharmacological profiles and fewer side effects. As we continue to unveil the mystery of GABABRs at the molecular and cellular levels, we further understand the significance of these receptors. Future directions should aim for developing highly selective GABABR compounds for treating neuropsychiatric disorders and their symptomatology.
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Affiliation(s)
- Styliani Vlachou
- Neuropsychopharmacology Division, Behavioural Neuroscience Laboratory, School of Psychology, Faculty of Science and Health, Dublin City University, Dublin, Ireland.
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Ulrich D, Lalanne T, Gassmann M, Bettler B. GABA B receptor subtypes differentially regulate thalamic spindle oscillations. Neuropharmacology 2017; 136:106-116. [PMID: 29106983 DOI: 10.1016/j.neuropharm.2017.10.033] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Revised: 10/23/2017] [Accepted: 10/24/2017] [Indexed: 12/14/2022]
Abstract
Following the discovery of GABAB receptors by Norman Bowery and colleagues, cloning and biochemical efforts revealed that GABAB receptors assemble multi-subunit complexes composed of principal and auxiliary subunits. The principal receptor subunits GABAB1a, GABAB1b and GABAB2 form two heterodimeric GABAB(1a,2) and GABAB(1b,2) receptors that can associate with tetramers of auxiliary KCTD (K+ channel tetramerization domain) subunits. Experiments with subunit knock-out mice revealed that GABAB(1b,2) receptors activate slow inhibitory postsynaptic currents (sIPSCs) while GABAB(1a,2) receptors function as heteroreceptors and inhibit glutamate release. Both GABAB(1a,2) and GABAB(1b,2) receptors can serve as autoreceptors and inhibit GABA release. Auxiliary KCTD subunits regulate the duration of sIPSCs and scaffold effector channels at the receptor. GABAB receptors are well known to contribute to thalamic spindle oscillations. Spindles are generated through alternating burst-firing in reciprocally connected glutamatergic thalamocortical relay (TCR) and GABAergic thalamic reticular nucleus (TRN) neurons. The available data implicate postsynaptic GABAB receptors in TCR cells in the regulation of spindle frequency. We now used electrical or optogenetic activation of thalamic spindles and pharmacological experiments in acute slices of knock-out mice to study the impact of GABAB(1a,2) and GABAB(1b,2) receptors on spindle oscillations. We found that selectively GABAB(1a,2) heteroreceptors at TCR to TRN cell synapses regulate oscillation strength, while GABAB(1b,2) receptors control oscillation frequency. The auxiliary subunit KCTD16 influences both oscillation strength and frequency, supporting that KCTD16 regulates network activity through GABAB(1a,2) and GABAB(1b,2) receptors. This article is part of the "Special Issue Dedicated to Norman G. Bowery".
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Affiliation(s)
- Daniel Ulrich
- Dept. Biomedicine, Institute of Physiology, University of Basel, 4056 Basel, Switzerland
| | - Txomin Lalanne
- Dept. Biomedicine, Institute of Physiology, University of Basel, 4056 Basel, Switzerland
| | - Martin Gassmann
- Dept. Biomedicine, Institute of Physiology, University of Basel, 4056 Basel, Switzerland
| | - Bernhard Bettler
- Dept. Biomedicine, Institute of Physiology, University of Basel, 4056 Basel, Switzerland.
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Glial GABA Transporters as Modulators of Inhibitory Signalling in Epilepsy and Stroke. ADVANCES IN NEUROBIOLOGY 2017; 16:137-167. [PMID: 28828609 DOI: 10.1007/978-3-319-55769-4_7] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Imbalances in GABA-mediated tonic inhibition are involved in several pathophysiological conditions. A classical way of controlling tonic inhibition is through pharmacological intervention with extrasynaptic GABAA receptors that sense ambient GABA and mediate a persistent GABAergic conductance. An increase in tonic inhibition may, however, also be obtained indirectly by inhibiting glial GABA transporters (GATs). These are sodium-coupled membrane transport proteins that normally act to terminate GABA neurotransmitter action by taking up GABA into surrounding astrocytes. The aim of the review is to provide an overview of glial GATs in regulating tonic inhibition, especially in epilepsy and stroke. This entails a comprehensive summary of changes known to occur in GAT expression levels and signalling following epileptic and ischemic insults. Further, we discuss the accumulating pharmacological evidence for targeting GATs in these diseases.
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Frye RE, Casanova MF, Fatemi SH, Folsom TD, Reutiman TJ, Brown GL, Edelson SM, Slattery JC, Adams JB. Neuropathological Mechanisms of Seizures in Autism Spectrum Disorder. Front Neurosci 2016; 10:192. [PMID: 27242398 PMCID: PMC4861974 DOI: 10.3389/fnins.2016.00192] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 04/18/2016] [Indexed: 01/09/2023] Open
Abstract
This manuscript reviews biological abnormalities shared by autism spectrum disorder (ASD) and epilepsy. Two neuropathological findings are shared by ASD and epilepsy: abnormalities in minicolumn architecture and γ-aminobutyric acid (GABA) neurotransmission. The peripheral neuropil, which is the region that contains the inhibition circuits of the minicolumns, has been found to be decreased in the post-mortem ASD brain. ASD and epilepsy are associated with inhibitory GABA neurotransmission abnormalities including reduced GABAA and GABAB subunit expression. These abnormalities can elevate the excitation-to-inhibition balance, resulting in hyperexcitablity of the cortex and, in turn, increase the risk of seizures. Medical abnormalities associated with both epilepsy and ASD are discussed. These include specific genetic syndromes, specific metabolic disorders including disorders of energy metabolism and GABA and glutamate neurotransmission, mineral and vitamin deficiencies, heavy metal exposures and immune dysfunction. Many of these medical abnormalities can result in an elevation of the excitatory-to-inhibitory balance. Fragile X is linked to dysfunction of the mGluR5 receptor and Fragile X, Angelman and Rett syndromes are linked to a reduction in GABAA receptor expression. Defects in energy metabolism can reduce GABA interneuron function. Both pyridoxine dependent seizures and succinic semialdehyde dehydrogenase deficiency cause GABA deficiencies while urea cycle defects and phenylketonuria cause abnormalities in glutamate neurotransmission. Mineral deficiencies can cause glutamate and GABA neurotransmission abnormalities and heavy metals can cause mitochondrial dysfunction which disrupts GABA metabolism. Thus, both ASD and epilepsy are associated with similar abnormalities that may alter the excitatory-to-inhibitory balance of the cortex. These parallels may explain the high prevalence of epilepsy in ASD and the elevated prevalence of ASD features in individuals with epilepsy.
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Affiliation(s)
- Richard E Frye
- Autism Research Program, Arkansas Children's Research InstituteLittle Rock, AR, USA; Department of Pediatrics, University of Arkansas for Medical SciencesLittle Rock, AR, USA
| | - Manuel F Casanova
- Department of Biomedical Sciences, University of South Carolina School of Medicine Greenville Greenville, SC, USA
| | - S Hossein Fatemi
- Department of Psychiatry, University of Minnesota Medical School Minneapolis, MN, USA
| | - Timothy D Folsom
- Department of Psychiatry, University of Minnesota Medical School Minneapolis, MN, USA
| | - Teri J Reutiman
- Department of Psychiatry, University of Minnesota Medical School Minneapolis, MN, USA
| | | | | | - John C Slattery
- Autism Research Program, Arkansas Children's Research InstituteLittle Rock, AR, USA; Department of Pediatrics, University of Arkansas for Medical SciencesLittle Rock, AR, USA
| | - James B Adams
- School for Engineering of Matter, Transport, and Energy, Arizona State University Tempe, AZ, USA
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Role of GABA(B) receptors in learning and memory and neurological disorders. Neurosci Biobehav Rev 2016; 63:1-28. [PMID: 26814961 DOI: 10.1016/j.neubiorev.2016.01.007] [Citation(s) in RCA: 92] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 12/31/2015] [Accepted: 01/21/2016] [Indexed: 01/13/2023]
Abstract
Although it is evident from the literature that altered GABAB receptor function does affect behavior, these results often do not correspond well. These differences could be due to the task protocol, animal strain, ligand concentration, or timing of administration utilized. Because several clinical populations exhibit learning and memory deficits in addition to altered markers of GABA and the GABAB receptor, it is important to determine whether altered GABAB receptor function is capable of contributing to the deficits. The aim of this review is to examine the effect of altered GABAB receptor function on synaptic plasticity as demonstrated by in vitro data, as well as the effects on performance in learning and memory tasks. Finally, data regarding altered GABA and GABAB receptor markers within clinical populations will be reviewed. Together, the data agree that proper functioning of GABAB receptors is crucial for numerous learning and memory tasks and that targeting this system via pharmaceuticals may benefit several clinical populations.
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Fatemi SH, Folsom TD. GABA receptor subunit distribution and FMRP-mGluR5 signaling abnormalities in the cerebellum of subjects with schizophrenia, mood disorders, and autism. Schizophr Res 2015; 167:42-56. [PMID: 25432637 PMCID: PMC5301472 DOI: 10.1016/j.schres.2014.10.010] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 10/06/2014] [Accepted: 10/08/2014] [Indexed: 12/24/2022]
Abstract
Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the brain. GABAergic receptor abnormalities have been documented in several major psychiatric disorders including schizophrenia, mood disorders, and autism. Abnormal expression of mRNA and protein for multiple GABA receptors has also been observed in multiple brain regions leading to alterations in the balance between excitatory/inhibitory signaling in the brain with potential profound consequences for normal cognition and maintenance of mood and perception. Altered expression of GABAA receptor subunits has been documented in fragile X mental retardation 1 (FMR1) knockout mice, suggesting that loss of its protein product, fragile X mental retardation protein (FMRP), impacts GABAA subunit expression. Recent postmortem studies from our laboratory have shown reduced expression of FMRP in the brains of subjects with schizophrenia, bipolar disorder, major depression, and autism. FMRP acts as a translational repressor and, under normal conditions, inhibits metabotropic glutamate receptor 5 (mGluR5)-mediated signaling. In fragile X syndrome (FXS), the absence of FMRP is hypothesized to lead to unregulated mGluR5 signaling, ultimately resulting in the behavioral and intellectual impairments associated with this disorder. Our laboratory has identified changes in mGluR5 expression in autism, schizophrenia, and mood disorders. In the current review article, we discuss our postmortem data on GABA receptors, FMRP, and mGluR5 levels and compare our results with other laboratories. Finally, we discuss the interactions between these molecules and the potential for new therapeutic interventions that target these interconnected signaling systems.
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Affiliation(s)
- S Hossein Fatemi
- Department of Psychiatry, Division of Neuroscience Research, University of Minnesota Medical School, 420 Delaware St SE, MMC 392, Minneapolis, MN 55455, USA; Department of Neuroscience, University of Minnesota Medical School, 321 Church St. SE, Minneapolis, MN 55455, USA.
| | - Timothy D Folsom
- Department of Psychiatry, Division of Neuroscience Research, University of Minnesota Medical School, 420 Delaware St SE, MMC 392, Minneapolis, MN 55455, USA.
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Kovács Z, Dobolyi Á, Juhász G, Kékesi KA. Lipopolysaccharide induced increase in seizure activity in two animal models of absence epilepsy WAG/Rij and GAERS rats and Long Evans rats. Brain Res Bull 2014; 104:7-18. [DOI: 10.1016/j.brainresbull.2014.03.003] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2014] [Revised: 03/20/2014] [Accepted: 03/24/2014] [Indexed: 02/04/2023]
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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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Bazyan AS, van Luijtelaar G. Neurochemical and behavioral features in genetic absence epilepsy and in acutely induced absence seizures. ISRN NEUROLOGY 2013; 2013:875834. [PMID: 23738145 PMCID: PMC3664506 DOI: 10.1155/2013/875834] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Accepted: 02/06/2013] [Indexed: 02/08/2023]
Abstract
The absence epilepsy typical electroencephalographic pattern of sharp spikes and slow waves (SWDs) is considered to be due to an interaction of an initiation site in the cortex and a resonant circuit in the thalamus. The hyperpolarization-activated cyclic nucleotide-gated cationic I h pacemaker channels (HCN) play an important role in the enhanced cortical excitability. The role of thalamic HCN in SWD occurrence is less clear. Absence epilepsy in the WAG/Rij strain is accompanied by deficiency of the activity of dopaminergic system, which weakens the formation of an emotional positive state, causes depression-like symptoms, and counteracts learning and memory processes. It also enhances GABAA receptor activity in the striatum, globus pallidus, and reticular thalamic nucleus, causing a rise of SWD activity in the cortico-thalamo-cortical networks. One of the reasons for the occurrence of absences is that several genes coding of GABAA receptors are mutated. The question arises: what the role of DA receptors is. Two mechanisms that cause an infringement of the function of DA receptors in this genetic absence epilepsy model are proposed.
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Affiliation(s)
- A. S. Bazyan
- Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Science, Russian Federation, 5A Butlerov Street, Moscow 117485, Russia
| | - G. van Luijtelaar
- Biological Psychology, Donders Centre for Cognition, Donders Institute for Brain, Cognition and Behavior, Radboud University Nijmegen, P.O. Box 9104, 6500 HE Nijmegen, The Netherlands
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Blatt GJ, Fatemi SH. Alterations in GABAergic biomarkers in the autism brain: research findings and clinical implications. Anat Rec (Hoboken) 2011; 294:1646-52. [PMID: 21901839 DOI: 10.1002/ar.21252] [Citation(s) in RCA: 132] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Accepted: 07/27/2010] [Indexed: 11/08/2022]
Abstract
Autism is a pervasive developmental disorder characterized by repetitive stereotyped behavior, social-emotional deficits, and delayed or absent language abilities. There are known neuropathologies in the autism brain affecting limbic, cerebellar, and cortical structures but the neurochemical profile of affected individuals, revealed in postmortem tissue studies, is only recently emerging. One major component that appears highly impacted in autism is the GABAergic system. It is now apparent that there are widespread significant effects in many distributed regions in the autism brain revealed by histochemical, autoradiographic, and biochemical studies. The key synthesizing enzymes for GABA, glutamic acid decarboxylase type 65 and 67 (GAD65 and GAD67), are decreased in the cerebellum and closer examination of mRNA levels revealed that it is largely due to decreases in Purkinje cells and a subpopulation of larger dentate neurons as measured by in situ hybridization studies. Other cell types had either normal GAD levels (Golgi cells, smaller dentate interneurons, and stellate cells) or increased levels (basket cells). GABA receptor density, number, and protein expression are all decreased in the cerebellum and in select cortical areas. GABA(A) and GABA(B) subunit protein expression was significantly reduced in cerebellum, BA 9 and BA 40. Benzodiazepine binding sites were significantly reduced in the hippocampus and anterior cingulate cortex (BA 24). Taken together, data from these studies suggest that there is a marked dysregulation of the inhibitory GABA system in the autism brain affecting particular biomarkers localized to specific cell types and lamina likely influencing circuitry and behavior.
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Affiliation(s)
- Gene J Blatt
- Department of Anatomy and Neurobiology, Laboratory for Autism Neuroscience Research, Boston University School of Medicine, Massachusetts, USA.
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Bortolato M, Frau R, Orrù M, Fà M, Dessì C, Puligheddu M, Barberini L, Pillolla G, Polizzi L, Santoni F, Mereu G, Marrosu F. GABAB receptor activation exacerbates spontaneous spike-and-wave discharges in DBA/2J mice. Seizure 2010; 19:226-31. [DOI: 10.1016/j.seizure.2010.02.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2009] [Revised: 02/13/2010] [Accepted: 02/19/2010] [Indexed: 10/19/2022] Open
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Froestl W. Chemistry and Pharmacology of GABAB Receptor Ligands. GABABRECEPTOR PHARMACOLOGY - A TRIBUTE TO NORMAN BOWERY 2010; 58:19-62. [DOI: 10.1016/s1054-3589(10)58002-5] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Fatemi SH, Folsom TD, Reutiman TJ, Thuras PD. Expression of GABA(B) receptors is altered in brains of subjects with autism. CEREBELLUM (LONDON, ENGLAND) 2009; 8:64-9. [PMID: 19002745 PMCID: PMC2732344 DOI: 10.1007/s12311-008-0075-3] [Citation(s) in RCA: 160] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Autism is a neurodevelopmental disorder that is often comorbid with seizures. Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in brain. GABA(B) receptors play an important role in maintaining excitatory-inhibitory balance in brain and alterations may lead to seizures. We compared levels of GABA(B) receptor subunits GABA(B) receptor 1 (GABBR1) and GABA(B) receptor 2 (GABBR2) in cerebellum, Brodmann's area 9 (BA9), and BA40 of subjects with autism and matched controls. Levels of GABBR1 were significantly decreased in BA9, BA40, and cerebellum, while GABBR2 was significantly reduced in the cerebellum. The presence of seizure disorder did not have a significant impact on the observed reductions in GABA(B) receptor subunit expression. Decreases in GABA(B) receptor subunits may help explain the presence of seizures that are often comorbid with autism, as well as cognitive difficulties prevalent in autism.
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Affiliation(s)
- S Hossein Fatemi
- Department of Psychiatry, Division of Neuroscience Research, University of Minnesota Medical School, Minneapolis, MN 55455, USA.
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Kauffman MA, Levy EM, Consalvo D, Mordoh J, Kochen S. GABABR1 (G1465A) gene variation and temporal lobe epilepsy controversy: New evidence. Seizure 2008; 17:567-71. [DOI: 10.1016/j.seizure.2007.12.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2007] [Revised: 07/23/2007] [Accepted: 12/19/2007] [Indexed: 11/16/2022] Open
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Abstract
This review considers how recent advances in the physiology of ion channels and other potential molecular targets, in conjunction with new information on the genetics of idiopathic epilepsies, can be applied to the search for improved antiepileptic drugs (AEDs). Marketed AEDs predominantly target voltage-gated cation channels (the alpha subunits of voltage-gated Na+ channels and also T-type voltage-gated Ca2+ channels) or influence GABA-mediated inhibition. Recently, alpha2-delta voltage-gated Ca2+ channel subunits and the SV2A synaptic vesicle protein have been recognized as likely targets. Genetic studies of familial idiopathic epilepsies have identified numerous genes associated with diverse epilepsy syndromes, including genes encoding Na+ channels and GABA(A) receptors, which are known AED targets. A strategy based on genes associated with epilepsy in animal models and humans suggests other potential AED targets, including various voltage-gated Ca2+ channel subunits and auxiliary proteins, A- or M-type voltage-gated K+ channels, and ionotropic glutamate receptors. Recent progress in ion channel research brought about by molecular cloning of the channel subunit proteins and studies in epilepsy models suggest additional targets, including G-protein-coupled receptors, such as GABA(B) and metabotropic glutamate receptors; hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channel subunits, responsible for hyperpolarization-activated current Ih; connexins, which make up gap junctions; and neurotransmitter transporters, particularly plasma membrane and vesicular transporters for GABA and glutamate. New information from the structural characterization of ion channels, along with better understanding of ion channel function, may allow for more selective targeting. For example, Na+ channels underlying persistent Na+ currents or GABA(A) receptor isoforms responsible for tonic (extrasynaptic) currents represent attractive targets. The growing understanding of the pathophysiology of epilepsy and the structural and functional characterization of the molecular targets provide many opportunities to create improved epilepsy therapies.
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Affiliation(s)
- Brian S Meldrum
- Centre for Neuroscience, Division of Biomedical and Health Sciences, School of Medicine, Kings College, London, United Kingdom
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Stewart LS, Bercovici E, Shukla R, Serbanescu I, Persad V, Mistry N, Cortez MA, Snead OC. Daily rhythms of seizure activity and behavior in a model of atypical absence epilepsy. Epilepsy Behav 2006; 9:564-72. [PMID: 17030024 DOI: 10.1016/j.yebeh.2006.08.019] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2006] [Revised: 08/28/2006] [Accepted: 08/29/2006] [Indexed: 10/24/2022]
Abstract
We studied daily rhythms of chronic seizure activity and behavior in adult rats and mice treated with the cholesterol biosynthesis inhibitor AY-9944 (AY) during early postnatal development. Chronic atypical absence seizures were verified in the AY-treated animals by the presence of spontaneous 5- to 6-Hz slow spike-wave discharges (SSWDs) in the neocortex. General behavioral activity, as measured by total movements (TM), movement time (MT), ambulatory movement time (AMT), time spent in center of arena (CT), jumps (JFP), and rotational behavior (TURNS), were continuously recorded under a 12-hour light:12-hour dark photocycle. The average SSWD duration in AY-treated rats varied daily, with two peaks occurring at approximately dark phase and light phase onset. Mice treated with AY exhibited significant increases in all behavioral measures during the light and dark phases, with the exception of light-phase CT, which did not differ from that of controls. Consequently, the daily rhythm of total behavioral activity (TM) exhibited a significantly higher mean oscillation (mesor) and amplitude without evidence of phase shift compared with the TM rhythm of controls. The occurrence of SSWD activity in the AY model appears to be subject to regulation by biological timing mechanisms and, furthermore, associated with motor hyperactivity that does not alter the timing of behavioral rhythmicity.
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Affiliation(s)
- Lee S Stewart
- Brain and Behavior Research Program, The Hospital for Sick Children, Toronto, Ont., Canada
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21
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Engle MP, Gassman M, Sykes KT, Bettler B, Hammond DL. Spinal nerve ligation does not alter the expression or function of GABA(B) receptors in spinal cord and dorsal root ganglia of the rat. Neuroscience 2006; 138:1277-87. [PMID: 16427742 PMCID: PMC1471878 DOI: 10.1016/j.neuroscience.2005.11.064] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2005] [Revised: 11/02/2005] [Accepted: 11/30/2005] [Indexed: 11/16/2022]
Abstract
Loss of GABA-mediated inhibition in the spinal cord is thought to mediate allodynia and spontaneous pain after nerve injury. Despite extensive investigation of GABA itself, relatively little is known about how nerve injury alters the receptors at which GABA acts. This study examined levels of GABA(B) receptor protein in the spinal cord dorsal horn, and in the L4 and L5 (lumbar designations) dorsal root ganglia one to 18 weeks after L5 spinal nerve ligation. Mechanical allodynia was maximal by 1 week and persisted at blunted levels for at least 18 weeks after injury. Spontaneous pain behaviors were evident for 6 weeks. Western blotting of dorsal horn detected two isoforms of the GABA(B(1)) subunit and a single GABA(B(2)) subunit. High levels of GABA(B(1a)) and low levels of GABA(B(1b)) protein were present in the dorsal root ganglia. However, GABA(B(2)) protein was not detected in the dorsal root ganglia, consistent with the proposed existence of an atypical receptor composed of GABA(B(1)) homodimers. The levels of GABA(B(1a)), GABA(B(1b)), and GABA(B(2)) protein in the ipsilateral dorsal horn were unchanged at any time after injury. Immunohistochemical staining also did not detect a change in GABA(B(1)) or GABA(B(2)) subunits in dorsal horn segments having a robust loss of isolectin B4 staining. The levels of GABA(B(1a)) protein were also unchanged in the L4 or L5 dorsal root ganglia at any time after spinal nerve ligation. Levels of GABA(B(2)) remained undetectable. Finally, baclofen-stimulated binding of guanosine-5'-(gamma-O-thio)triphosphate in dorsal horn did not differ between sham and ligated rats. Collectively, these results argue that a loss of GABA(B) receptor-mediated inhibition, particularly of central terminals of primary afferents, is unlikely to mediate the development or maintenance of allodynia or spontaneous pain behaviors after spinal nerve injury.
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Affiliation(s)
| | - Martin Gassman
- Pharmazentrum University of Basel, Basel CH-4056 Switzerland
| | | | | | - Donna L. Hammond
- Departments of Anesthesia and
- Pharmacology The University of Iowa, Iowa City, IA 52242, USA
- Address Correspondence to: Donna L. Hammond, Ph.D. Department of Anesthesia 200 Hawkins Drive 6 JCP The University of Iowa Iowa City, IA 52242 319-384-7127 (voice) 319-356-2940 (fax)
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22
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Enna SJ, Bowery NG. GABA(B) receptor alterations as indicators of physiological and pharmacological function. Biochem Pharmacol 2005; 68:1541-8. [PMID: 15451397 DOI: 10.1016/j.bcp.2004.06.037] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2004] [Accepted: 06/21/2004] [Indexed: 11/15/2022]
Abstract
Given the widespread distribution of GABA(B) receptors throughout the central nervous system, and within certain peripheral organs, it is likely their selective pharmacological manipulation could be of benefit in the treatment of a variety of disorders. Studies aimed at defining the clinical potential of GABA(B) receptor agonists and antagonists have included gene deletion experiments, examination of changes in receptor binding, subunit expression and function in diseased tissue, as well as after the chronic administration of drugs. The results indicate that a functional GABA(B) receptor requires the combination of GABA(B(1)) and GABA(B(2)) subunits, that receptor function does not always correlate with subunit expression and receptor binding, and that GABA(B) receptor modifications may be associated with the clinical response to antidepressants, mood stabilizers, and GABA(B) receptor agonists and antagonists. Moreover, changes in GABA(B) binding or expression suggest this receptor may be involved in mediating symptoms associated with chronic pain, epilepsy and schizophrenia. This, together with results from other types of studies, indicates the potential therapeutic value of developing drugs capable of selectively activating, inhibiting, or modulating GABA(B) receptor function.
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Affiliation(s)
- S J Enna
- Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical School, 3901 Rainbow Boulevard, Mail Stop 1018, Kansas City, Kansas 66160-0227, USA.
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Suffczynski P, Kalitzin S, Lopes Da Silva FH. Dynamics of non-convulsive epileptic phenomena modeled by a bistable neuronal network. Neuroscience 2004; 126:467-84. [PMID: 15207365 DOI: 10.1016/j.neuroscience.2004.03.014] [Citation(s) in RCA: 197] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/07/2004] [Indexed: 11/20/2022]
Abstract
It is currently believed that the mechanisms underlying spindle oscillations are related to those that generate spike and wave (SW) discharges. The mechanisms of transition between these two types of activity, however, are not well understood. In order to provide more insight into the dynamics of the neuronal networks leading to seizure generation in a rat experimental model of absence epilepsy we developed a computational model of thalamo-cortical circuits based on relevant (patho)physiological data. The model is constructed at the macroscopic level since this approach allows to investigate dynamical properties of the system and the role played by different mechanisms in the process of seizure generation, both at short and long time scales. The main results are the following: (i) SW discharges represent dynamical bifurcations that occur in a bistable neuronal network; (ii) the durations of paroxysmal and normal epochs have exponential distributions, indicating that transitions between these two stable states occur randomly over time with constant probabilities; (iii) the probabilistic nature of the onset of paroxysmal activity implies that it is not possible to predict its occurrence; (iv) the bistable nature of the dynamical system allows that an ictal state may be aborted by a single counter-stimulus.
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Affiliation(s)
- P Suffczynski
- Stichting Epilepsie Instellingen Nederland, Achterweg 5, 2103 SW Heemstede, The Netherlands.
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