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Leitch B. Parvalbumin Interneuron Dysfunction in Neurological Disorders: Focus on Epilepsy and Alzheimer's Disease. Int J Mol Sci 2024; 25:5549. [PMID: 38791587 PMCID: PMC11122153 DOI: 10.3390/ijms25105549] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2024] [Revised: 05/11/2024] [Accepted: 05/16/2024] [Indexed: 05/26/2024] Open
Abstract
Parvalbumin expressing (PV+) GABAergic interneurons are fast spiking neurons that provide powerful but relatively short-lived inhibition to principal excitatory cells in the brain. They play a vital role in feedforward and feedback synaptic inhibition, preventing run away excitation in neural networks. Hence, their dysfunction can lead to hyperexcitability and increased susceptibility to seizures. PV+ interneurons are also key players in generating gamma oscillations, which are synchronized neural oscillations associated with various cognitive functions. PV+ interneuron are particularly vulnerable to aging and their degeneration has been associated with cognitive decline and memory impairment in dementia and Alzheimer's disease (AD). Overall, dysfunction of PV+ interneurons disrupts the normal excitatory/inhibitory balance within specific neurocircuits in the brain and thus has been linked to a wide range of neurodevelopmental and neuropsychiatric disorders. This review focuses on the role of dysfunctional PV+ inhibitory interneurons in the generation of epileptic seizures and cognitive impairment and their potential as targets in the design of future therapeutic strategies to treat these disorders. Recent research using cutting-edge optogenetic and chemogenetic technologies has demonstrated that they can be selectively manipulated to control seizures and restore the balance of neural activity in the brains of animal models. This suggests that PV+ interneurons could be important targets in developing future treatments for patients with epilepsy and comorbid disorders, such as AD, where seizures and cognitive decline are directly linked to specific PV+ interneuron deficits.
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Affiliation(s)
- Beulah Leitch
- Department of Anatomy, School of Biomedical Sciences, Brain Health Research Centre, University of Otago, Dunedin 9016, New Zealand
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2
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Patel JC, Sherpa AD, Melani R, Witkovsky P, Wiseman MR, O'Neill B, Aoki C, Tritsch NX, Rice ME. GABA co-released from striatal dopamine axons dampens phasic dopamine release through autoregulatory GABA A receptors. Cell Rep 2024; 43:113834. [PMID: 38431842 PMCID: PMC11089423 DOI: 10.1016/j.celrep.2024.113834] [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: 10/05/2022] [Revised: 11/29/2023] [Accepted: 02/05/2024] [Indexed: 03/05/2024] Open
Abstract
Striatal dopamine axons co-release dopamine and gamma-aminobutyric acid (GABA), using GABA provided by uptake via GABA transporter-1 (GAT1). Functions of GABA co-release are poorly understood. We asked whether co-released GABA autoinhibits dopamine release via axonal GABA type A receptors (GABAARs), complementing established inhibition by dopamine acting at axonal D2 autoreceptors. We show that dopamine axons express α3-GABAAR subunits in mouse striatum. Enhanced dopamine release evoked by single-pulse optical stimulation in striatal slices with GABAAR antagonism confirms that an endogenous GABA tone limits dopamine release. Strikingly, an additional inhibitory component is seen when multiple pulses are used to mimic phasic axonal activity, revealing the role of GABAAR-mediated autoinhibition of dopamine release. This autoregulation is lost in conditional GAT1-knockout mice lacking GABA co-release. Given the faster kinetics of ionotropic GABAARs than G-protein-coupled D2 autoreceptors, our data reveal a mechanism whereby co-released GABA acts as a first responder to dampen phasic-to-tonic dopamine signaling.
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Affiliation(s)
- Jyoti C Patel
- Department of Neurosurgery, New York University Grossman School of Medicine, 550 First Avenue, New York, NY 10016, USA.
| | - Ang D Sherpa
- Department of Neurosurgery, New York University Grossman School of Medicine, 550 First Avenue, New York, NY 10016, USA; Center for Neural Science New York University, 4 Washington Place, New York, NY 10003, USA
| | - Riccardo Melani
- NYU Neuroscience Institute, New York University Grossman School of Medicine, 550 First Avenue, New York, NY 10016, USA
| | - Paul Witkovsky
- Department of Neurosurgery, New York University Grossman School of Medicine, 550 First Avenue, New York, NY 10016, USA
| | - Madeline R Wiseman
- Department of Neurosurgery, New York University Grossman School of Medicine, 550 First Avenue, New York, NY 10016, USA
| | - Brian O'Neill
- Department of Neurosurgery, New York University Grossman School of Medicine, 550 First Avenue, New York, NY 10016, USA
| | - Chiye Aoki
- NYU Neuroscience Institute, New York University Grossman School of Medicine, 550 First Avenue, New York, NY 10016, USA; Center for Neural Science New York University, 4 Washington Place, New York, NY 10003, USA
| | - Nicolas X Tritsch
- NYU Neuroscience Institute, New York University Grossman School of Medicine, 550 First Avenue, New York, NY 10016, USA
| | - Margaret E Rice
- Department of Neurosurgery, New York University Grossman School of Medicine, 550 First Avenue, New York, NY 10016, USA; NYU Neuroscience Institute, New York University Grossman School of Medicine, 550 First Avenue, New York, NY 10016, USA.
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3
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Developmental Inhibitory Changes in the Primary Somatosensory Cortex of the Stargazer Mouse Model of Absence Epilepsy. Biomolecules 2023; 13:biom13010186. [PMID: 36671571 PMCID: PMC9856073 DOI: 10.3390/biom13010186] [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: 12/18/2022] [Revised: 01/08/2023] [Accepted: 01/11/2023] [Indexed: 01/19/2023] Open
Abstract
Childhood absence epilepsy seizures arise in the cortico-thalamocortical network due to multiple cellular and molecular mechanisms, which are still under investigation. Understanding the precise mechanisms is imperative given that treatment fails in ~30% of patients while adverse neurological sequelae remain common. Impaired GABAergic neurotransmission is commonly reported in research models investigating these mechanisms. Recently, we reported a region-specific reduction in the whole-tissue and synaptic GABAA receptor (GABAAR) α1 subunit and an increase in whole-tissue GAD65 in the primary somatosensory cortex (SoCx) of the adult epileptic stargazer mouse compared with its non-epileptic (NE) littermate. The current study investigated whether these changes occurred prior to the onset of seizures on postnatal days (PN) 17-18, suggesting a causative role. Synaptic and cytosolic fractions were biochemically isolated from primary SoCx lysates followed by semiquantitative Western blot analyses for GABAAR α1 and GAD65. We found no significant changes in synaptic GABAAR α1 and cytosolic GAD65 in the primary SoCx of the stargazer mice at the critical developmental stages of PN 7-9, 13-15, and 17-18. This indicates that altered levels of GABAAR α1 and GAD65 in adult mice do not directly contribute to the initial onset of absence seizures but are a later consequence of seizure activity.
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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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Leitch B. The Impact of Glutamatergic Synapse Dysfunction in the Corticothalamocortical Network on Absence Seizure Generation. Front Mol Neurosci 2022; 15:836255. [PMID: 35237129 PMCID: PMC8882758 DOI: 10.3389/fnmol.2022.836255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 01/18/2022] [Indexed: 12/02/2022] Open
Abstract
Childhood absence epilepsy (CAE) is the most common pediatric epilepsy affecting 10–18% of all children with epilepsy. It is genetic in origin and the result of dysfunction within the corticothalamocortical (CTC) circuitry. Network dysfunction may arise from multifactorial mechanisms in patients from different genetic backgrounds and thus account for the variability in patient response to currently available anti-epileptic drugs; 30% of children with absence seizures are pharmaco-resistant. This review considers the impact of deficits in AMPA receptor-mediated excitation of feed-forward inhibition (FFI) in the CTC, on absence seizure generation. AMPA receptors are glutamate activated ion channels and are responsible for most of the fast excitatory synaptic transmission throughout the CNS. In the stargazer mouse model of absence epilepsy, the genetic mutation is in stargazin, a transmembrane AMPA receptor trafficking protein (TARP). This leads to a defect in AMPA receptor insertion into synapses in parvalbumin-containing (PV+) inhibitory interneurons in the somatosensory cortex and thalamus. Mutation in the Gria4 gene, which encodes for the AMPA receptor subunit GluA4, the predominant AMPA receptor subunit in cortical and thalamic PV + interneurons, also leads to absence seizures. This review explores the impact of glutamatergic synapse dysfunction in the CTC network on absence seizure generation. It also discusses the cellular and molecular mechanisms involved in the pathogenesis of childhood absence epilepsy.
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Barki M, Xue H. GABRB2, a key player in neuropsychiatric disorders and beyond. Gene 2022; 809:146021. [PMID: 34673206 DOI: 10.1016/j.gene.2021.146021] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2020] [Revised: 08/05/2021] [Accepted: 09/14/2021] [Indexed: 01/11/2023]
Abstract
The GABA receptors represent the main inhibitory system in the central nervous system that ensure synaptogenesis, neurogenesis, and the regulation of neuronal plasticity and learning. GABAA receptors are pentameric in structure and belong to the Cys-loop superfamily. The GABRB2 gene, located on chromosome 5q34, encodes the β2 subunit that combines with the α and γ subunits to form the major subtype of GABAA receptors, which account for 43% of all GABAA receptors in the mammalian brain. Each subunit probably consists of an extracellular N-terminal domain, four membrane-spanning segments, a large intracellular loop between TM3 and TM4, and an extracellular C-terminal domain. Alternative splicing of the RNA transcript of the GABRB2 gene gives rise at least to four long and short isoforms with dissimilar electrophysiological properties. Furthermore, GABRB2 is imprinted and subjected to epigenetic regulation and positive selection. It has been associated with schizophrenia first in Han Chinese, and subsequently validated in other populations. Gabrb2 knockout mice also exhibited schizophrenia-like behavior and neuroinflammation that were ameliorated by the antipsychotic drug risperidone. GABRB2 was also associated with other neuropsychiatric disorders including bipolar disorder, epilepsy, autism spectrum disorder, Alzheimer's disease, frontotemporal dementia, substance dependence, depression, internet gaming disorder, and premenstrual dysphoric disorder. Recently, it has been postulated that GABRB2 might be a potential marker for different cancer types. As GABRB2 has a pivotal role in the central nervous system and is increasingly recognized to contribute to human diseases, further understanding of its structure and function may expedite the generation of new therapeutic approaches.
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Affiliation(s)
- Manel Barki
- Center for Cancer Genomics, School of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Nanjing, Jiangsu, China
| | - Hong Xue
- Center for Cancer Genomics, School of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Nanjing, Jiangsu, China; Division of Life Science and Applied Genomics Center, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.
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7
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Panthi S, Lyons NMA, Leitch B. Impact of Dysfunctional Feed-Forward Inhibition on Glutamate Decarboxylase Isoforms and γ-Aminobutyric Acid Transporters. Int J Mol Sci 2021; 22:ijms22147740. [PMID: 34299369 PMCID: PMC8306481 DOI: 10.3390/ijms22147740] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 07/16/2021] [Indexed: 12/02/2022] Open
Abstract
Absence seizures are associated with generalised synchronous 2.5–4 Hz spike-wave discharges causing brief and sudden alteration of awareness during childhood, which is known as childhood absence epilepsy (CAE). CAE is also associated with impaired learning, psychosocial challenges, and physical danger. Absence seizures arise from disturbances within the cortico-thalamocortical (CTC) network, including dysfunctional feed-forward inhibition (FFI); however, the precise mechanisms remain unclear. In epileptic stargazers, a genetic mouse model of CAE with chronic seizures, levels of γ-aminobutyric acid (GABA), and expression of GABA receptors are altered within the CTC network, implicating altered GABAergic transmission in absence seizures. However, the expression of GABA synthesising enzymes (GAD65 and GAD67) and GABA transporters (GAT-1 and 3) have not yet been characterised within absence seizure models. We found a specific upregulation of GAD65 in the somatosensory cortex but not the thalamus of epileptic stargazer mice. No differences were detected in GAD67 and GAT-3 levels in the thalamus or somatosensory cortex. Then, we assessed if GAD65 upregulation also occurred in Gi-DREADD mice exhibiting acute absence seizures, but we found no change in the expression profiles of GAD65/67 or GAT-3. Thus, the upregulation of GAD65 in stargazers may be a compensatory mechanism in response to long-term dysfunctional FFI and chronic absence seizures.
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Affiliation(s)
| | | | - Beulah Leitch
- Correspondence: ; Tel.: +64-3-479-7618; Fax: +64-3-479-7254
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Adotevi N, Su A, Peiris D, Hassan M, Leitch B. Altered Neurotransmitter Expression in the Corticothalamocortical Network of an Absence Epilepsy Model with impaired Feedforward Inhibition. Neuroscience 2021; 467:73-80. [PMID: 34048799 DOI: 10.1016/j.neuroscience.2021.05.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 05/03/2021] [Accepted: 05/17/2021] [Indexed: 11/16/2022]
Abstract
The episodes of brief unconsciousness in patients with childhood absence epilepsy are a result of corticothalamocortical circuitry dysfunction. This dysfunction may arise from multifactorial mechanisms in patients from different genetic backgrounds. In previous studies using the epileptic stargazer mutant mouse, which experience frequent absence seizures, we reported a deficit in AMPAR-mediated feed-forward inhibition of parvalbumin-containing (PV+) interneurons. Currently, in order to determine the downstream effects of this impairment on neurotransmitter expression, we performed HPLC of tissue lysates and post-embedding electron microscopy from the cortical and thalamic regions. We report region-specific alterations in GABA expression, but not of glutamate, and most prominently at PV+ synaptic terminals. These results suggest that impaired feed forward inhibition may occur via reduced activation of these interneurons and concomitant decreased GABAergic signaling. Further investigations into GABAergic control of corticothalamocortical network activity could be key in our understanding of absence seizure pathogenesis.
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Affiliation(s)
- Nadia Adotevi
- Department of Anatomy, Brain Health Research Centre, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Aini Su
- Department of Anatomy, Brain Health Research Centre, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Danushi Peiris
- Department of Anatomy, Brain Health Research Centre, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Muhammad Hassan
- Department of Anatomy, Brain Health Research Centre, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Beulah Leitch
- Department of Anatomy, Brain Health Research Centre, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.
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Deidda G, Crunelli V, Di Giovanni G. 5-HT/GABA interaction in epilepsy. PROGRESS IN BRAIN RESEARCH 2021; 259:265-286. [PMID: 33541679 DOI: 10.1016/bs.pbr.2021.01.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Epilepsy is a neurological condition characterized by synchronous neuronal oscillations (seizures) in the electroencephalogram. Seizures are classified in focal or generalized (depending on the brain territory interested during seizures), and in convulsive and/or not convulsive (depending on the presence or not of involuntary movements). The current pharmacological treatments are mainly based on GABA modulation although different neurotransmitters are also involved in epilepsy, including serotonin. However despite much extensive progress in the understanding of epilepsy mechanisms, still, a percentage of people with epilepsy are pharmaco-resistant calling for the need for new therapeutic targets. Here we review preclinical and human evidence showing that serotonin modulates epilepsy that this likely happens via a major modulation/interaction with GABA.
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Affiliation(s)
- Gabriele Deidda
- Laboratory of Neurophysiology, Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida, Malta.
| | - Vincenzo Crunelli
- Laboratory of Neurophysiology, Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida, Malta; Neuroscience Division, School of Biosciences, Cardiff University, Cardiff, United Kingdom
| | - Giuseppe Di Giovanni
- Laboratory of Neurophysiology, Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida, Malta; Neuroscience Division, School of Biosciences, Cardiff University, Cardiff, United Kingdom
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Ikemoto S, Hamano SI, Yokota S, Koichihara R, Hirata Y, Matsuura R. High-power, frontal-dominant ripples in absence status epilepticus during childhood. Clin Neurophysiol 2020; 131:1204-1209. [DOI: 10.1016/j.clinph.2020.02.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 01/28/2020] [Accepted: 02/12/2020] [Indexed: 11/25/2022]
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The functional microscopic neuroanatomy of the human subthalamic nucleus. Brain Struct Funct 2019; 224:3213-3227. [PMID: 31562531 PMCID: PMC6875153 DOI: 10.1007/s00429-019-01960-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 09/14/2019] [Indexed: 01/19/2023]
Abstract
The subthalamic nucleus (STN) is successfully used as a surgical target for deep brain stimulation in the treatment of movement disorders. Interestingly, the internal structure of the STN is still incompletely understood. The objective of the present study was to investigate three-dimensional (3D) immunoreactivity patterns for 12 individual protein markers for GABA-ergic, serotonergic, dopaminergic as well as glutamatergic signaling. We analyzed the immunoreactivity using optical densities and created a 3D reconstruction of seven postmortem human STNs. Quantitative modeling of the reconstructed 3D immunoreactivity patterns revealed that the applied protein markers show a gradient distribution in the STN. These gradients were predominantly organized along the ventromedial to dorsolateral axis of the STN. The results are of particular interest in view of the theoretical underpinning for surgical targeting, which is based on a tripartite distribution of cognitive, limbic and motor function in the STN.
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12
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Li S, Luo Z, Lu B, Xia S, Li C, Guan X, Zhang J, Huang K, Xian F. Protective effects of lycopene on kainic acid-induced seizures. Epilepsy Res 2019; 151:1-6. [PMID: 30669043 DOI: 10.1016/j.eplepsyres.2019.01.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 01/10/2019] [Accepted: 01/17/2019] [Indexed: 12/11/2022]
Abstract
Lycopene (LCP) is a carotenoid that protects against many diseases by alleviating oxidative stress. However, the effect of LCP on epileptic seizures has not been examined well in previous studies. In the current work, we employed kainic acid (KA) to induce experimental epileptic seizures in mice, and investigated the function of LCP during this process. We found that the onset and extent of KA-induced seizures were alleviated in LCP-pretreated mice. Nissl staining of hippocampus showed that the granule cell dispersion lesion induced by KA was improved by the LCP treatment. Additionally, we analyzed the oxidative stress levels in mice and found that LCP elevated SOD activity and suppressed MDA level in KA-induced seizures. Moreover, the expression of GABA receptors was influenced by LCP treatment. LCP suppressed the upregulation of gabrb2 and gabrb3 induced by KA, whereas it enhanced the expression of gabrb1. Results suggested that LCP plays a protective function in KA-induced seizures. Hence, it may be a potential functional food alternative for controlling and treating epileptic seizures.
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Affiliation(s)
- Sen Li
- School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China
| | - Zhen Luo
- School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China
| | - Bingyi Lu
- School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China
| | - Shangzhou Xia
- School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China
| | - Chen Li
- School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China
| | - Xiao Guan
- School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China.
| | - Jingchen Zhang
- Certification and Review Center, Shanghai Municipal Food and Drug Administration, Shanghai, 200020, China
| | - Kai Huang
- School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China
| | - Furong Xian
- School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China
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Rosch RE, Hunter PR, Baldeweg T, Friston KJ, Meyer MP. Calcium imaging and dynamic causal modelling reveal brain-wide changes in effective connectivity and synaptic dynamics during epileptic seizures. PLoS Comput Biol 2018; 14:e1006375. [PMID: 30138336 PMCID: PMC6124808 DOI: 10.1371/journal.pcbi.1006375] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 09/05/2018] [Accepted: 07/18/2018] [Indexed: 12/31/2022] Open
Abstract
Pathophysiological explanations of epilepsy typically focus on either the micro/mesoscale (e.g. excitation-inhibition imbalance), or on the macroscale (e.g. network architecture). Linking abnormalities across spatial scales remains difficult, partly because of technical limitations in measuring neuronal signatures concurrently at the scales involved. Here we use light sheet imaging of the larval zebrafish brain during acute epileptic seizure induced with pentylenetetrazole. Spectral changes of spontaneous neuronal activity during the seizure are then modelled using neural mass models, allowing Bayesian inference on changes in effective network connectivity and their underlying synaptic dynamics. This dynamic causal modelling of seizures in the zebrafish brain reveals concurrent changes in synaptic coupling at macro- and mesoscale. Fluctuations of both synaptic connection strength and their temporal dynamics are required to explain observed seizure patterns. These findings highlight distinct changes in local (intrinsic) and long-range (extrinsic) synaptic transmission dynamics as a possible seizure pathomechanism and illustrate how our Bayesian model inversion approach can be used to link existing neural mass models of seizure activity and novel experimental methods.
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Affiliation(s)
- Richard E. Rosch
- Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom
- Developmental Neurosciences Programme, UCL Great Ormond Street Institute of Child Health, University College London, London, United Kingdom
| | - Paul R. Hunter
- Department of Developmental Neurobiology & MRC Center for Neurodevelopmental Disorders, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
| | - Torsten Baldeweg
- Developmental Neurosciences Programme, UCL Great Ormond Street Institute of Child Health, University College London, London, United Kingdom
| | - Karl J. Friston
- Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom
| | - Martin P. Meyer
- Department of Developmental Neurobiology & MRC Center for Neurodevelopmental Disorders, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
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14
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Postnatal expression of thalamic GABAA receptor subunits in the stargazer mouse model of absence epilepsy. Neuroreport 2018; 28:1255-1260. [PMID: 29099440 DOI: 10.1097/wnr.0000000000000909] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Absence seizures are known to originate from disruptions within the corticothalamocortical network; however, the precise underlying cellular and molecular mechanisms that induce hypersynchronicity and hyperexcitability are debated and likely to be complex and multifactorial. Recent studies implicate impaired thalamic GABAergic inhibition as a common feature in multiple animal models of absence epilepsy, including the well-established stargazer mouse model. Recently, we demonstrated region-specific increases in the whole tissue and synaptic levels of GABAA receptor (GABAAR) subunits α1 and β2, within the ventral posterior region of the thalamus in adult epileptic stargazer mice compared with nonepileptic control littermates. The objective of this study was to investigate whether such changes in GABAAR subunits α1 and β2 can be observed before the initiation of seizures, which occur around postnatal (PN) days 16-18 in stargazers. Semiquantitative western blotting was used to analyze the relative tissue level expression of GABAAR α1 and β2 subunits in the thalamus of juvenile stargazer mice compared with their nonepileptic control littermates at three different time points before the initiation of seizures. We show that there is a statistically significant increase in the expression of α1 and β2 subunits in the thalamus of stargazer mice, at the PN7-9 stage, compared with the control littermates, but not at PN10-12 and PN13-15 stages. These results suggest that an aberrant expression of GABAAR subunits α1 and β2 in the stargazers does not occur immediately before seizure onset and therefore is unlikely to directly contribute to the initiation of absence seizures.
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15
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Hu B, Guo Y, Shi F, Zou X, Dong J, Pan L, Yu M, Zhou C, Cheng Z, Tang W, Sun H, Chen L. The generation mechanism of spike-and-slow wave discharges appearing on thalamic relay nuclei. Sci Rep 2018; 8:4953. [PMID: 29563579 PMCID: PMC5862852 DOI: 10.1038/s41598-018-23280-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 03/08/2018] [Indexed: 12/19/2022] Open
Abstract
In this paper, we use a model modified from classic corticothalamic network(CT) to explore the mechanism of absence seizures appearing on specific relay nuclei (SRN) of the thalamus. It is found that typical seizure states appear on SRN through tuning several critical connection strengths in the model. In view of previous experimental and theoretical works which were mainly on epilepsy seizure phenomena appearing on excitatory pyramidal neurons (EPN) of the cortex, this is a novel model to consider the seizure observed on thalamus. In particular, the onset mechanism is different from previous theoretical studies. Inspired by some previous clinical and experimental studies, we employ the external stimuli voltage on EPN and SRN in the network, and observe that the seizure can be well inhibited by tuning the stimulus intensity appropriately. We further explore the effect of the signal transmission delays on seizures, and found that the polyspike phenomenon appears only when the delay is sufficiently large. The experimental data also confirmed our model. Since there is a complex network in the brain and all organizations are interacting closely with each other, the results obtained in this paper provide not only biological insights into the regulatory mechanisms but also a reference for the prevention and treatment of epilepsy in future.
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Affiliation(s)
- Bing Hu
- Institute of Applied Mathematics, Department of Mathematics and Statistics, College of Science, Huazhong Agricultural University, Wuhan, 430070, China.
- Key Laboratory of Systems Biology, CAS center for Excellence in Molecular Cell Science, Innovation Center for Cell Signaling Network, Institute of Biochemistry and Cell Biology, Shanghai Institute of Biological Sciences, Chinese Academy of Sciences, Shanghai, 200031, China.
| | - Yu Guo
- Institute of Applied Mathematics, Department of Mathematics and Statistics, College of Science, Huazhong Agricultural University, Wuhan, 430070, China
| | - Feng Shi
- Institute of Applied Mathematics, Department of Mathematics and Statistics, College of Science, Huazhong Agricultural University, Wuhan, 430070, China
| | - Xiaoqiang Zou
- Institute of Applied Mathematics, Department of Mathematics and Statistics, College of Science, Huazhong Agricultural University, Wuhan, 430070, China
| | - Jing Dong
- Institute of Applied Mathematics, Department of Mathematics and Statistics, College of Science, Huazhong Agricultural University, Wuhan, 430070, China
| | - Long Pan
- Institute of Applied Mathematics, Department of Mathematics and Statistics, College of Science, Huazhong Agricultural University, Wuhan, 430070, China
| | - Min Yu
- Institute of Applied Mathematics, Department of Mathematics and Statistics, College of Science, Huazhong Agricultural University, Wuhan, 430070, China
| | - Chaowei Zhou
- Institute of Applied Mathematics, Department of Mathematics and Statistics, College of Science, Huazhong Agricultural University, Wuhan, 430070, China
| | - Zhang Cheng
- Institute of Applied Mathematics, Department of Mathematics and Statistics, College of Science, Huazhong Agricultural University, Wuhan, 430070, China
| | - Wanyue Tang
- Institute of Applied Mathematics, Department of Mathematics and Statistics, College of Science, Huazhong Agricultural University, Wuhan, 430070, China
| | - Haochen Sun
- Institute of Applied Mathematics, Department of Mathematics and Statistics, College of Science, Huazhong Agricultural University, Wuhan, 430070, China
| | - Luonan Chen
- Key Laboratory of Systems Biology, CAS center for Excellence in Molecular Cell Science, Innovation Center for Cell Signaling Network, Institute of Biochemistry and Cell Biology, Shanghai Institute of Biological Sciences, Chinese Academy of Sciences, Shanghai, 200031, China.
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16
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Barad Z, Grattan DR, Leitch B. NMDA Receptor Expression in the Thalamus of the Stargazer Model of Absence Epilepsy. Sci Rep 2017; 7:42926. [PMID: 28220891 PMCID: PMC5318904 DOI: 10.1038/srep42926] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Accepted: 01/16/2017] [Indexed: 11/09/2022] Open
Abstract
In the stargazer mouse model of absence epilepsy, altered corticothalamic excitation of reticular thalamic nucleus (RTN) neurons has been suggested to contribute to abnormal synchronicity in the corticothalamic-thalamocortical circuit, leading to spike-wave discharges, the hallmark of absence seizures. AMPA receptor expression and function are decreased in stargazer RTN, due to a mutation of AMPAR auxiliary subunit stargazin. It is unresolved and debated, however, if decreased excitation of RTN is compatible with epileptogenesis. We tested the hypothesis that relative NMDAR expression may be increased in RTN and/or thalamic synapses in stargazers using Western blot on dissected thalamic nuclei and biochemically isolated synapses, as well as immunogold cytochemistry in RTN. Expression of main NMDAR subunits was variable in stargazer RTN and relay thalamus; however, mean expression values were not statistically significantly different compared to controls. Furthermore, no systematic changes in synaptic NMDAR levels could be detected in stargazer thalamus. In contrast, AMPAR subunits were markedly decreased in both nucleus-specific and synaptic preparations. Thus, defective AMPAR trafficking in stargazer thalamus does not appear to lead to a ubiquitous compensatory increase in total and synaptic NMDAR expression, suggesting that elevated NMDAR function is not mediated by changes in protein expression in stargazer mice.
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Affiliation(s)
- Z Barad
- Department of Anatomy, Otago School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,Brain Health Research Centre, University of Otago, Dunedin, New Zealand
| | - D R Grattan
- Department of Anatomy, Otago School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,Centre for Neuroendocrinology, Dunedin, New Zealand
| | - B Leitch
- Department of Anatomy, Otago School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,Brain Health Research Centre, University of Otago, Dunedin, New Zealand
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17
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Lee K, Goodman L, Fourie C, Schenk S, Leitch B, Montgomery JM. AMPA Receptors as Therapeutic Targets for Neurological Disorders. ION CHANNELS AS THERAPEUTIC TARGETS, PART A 2016; 103:203-61. [DOI: 10.1016/bs.apcsb.2015.10.004] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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18
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Synaptic changes in GABAA receptor expression in the thalamus of the stargazer mouse model of absence epilepsy. Neuroscience 2015; 306:28-38. [PMID: 26297893 DOI: 10.1016/j.neuroscience.2015.08.021] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Revised: 08/12/2015] [Accepted: 08/12/2015] [Indexed: 01/04/2023]
Abstract
Absence seizures are known to result from disturbances within the cortico-thalamocortical network, which remains partially synchronous under normal conditions but switches to a state of hypersynchronicity and hyperexcitability during absence seizures. There is evidence to suggest that impaired GABAergic inhibitory function within the thalamus could contribute to the generation of hypersynchronous oscillations in some animal models of absence epilepsy. Recently, we demonstrated region-specific alterations in the tissue expression level of GABAA receptors (GABA(A)Rs) α1 and β2 subunits within the thalamus of the stargazer mouse model of absence epilepsy. In the present study we investigated whether changes in these subunits also occur at synapses in the ventral posterior (VP) complex where they are components of phasic GABA(A)R receptors. Postembedding immunogold cytochemistry and electron microscopy were used to analyze the relative synaptic expression of α1 and β2 subunits in the VP thalamic region in epileptic stargazer mice compared to their non-epileptic littermates. We show that there is a significant increase in expression of α1 and β2 subunits (53.6% and 45.8%, respectively) at synapses in the VP region of stargazers, indicative of an increase in phasic GABA(A)Rs at thalamocortical (TC) relay neurons. Furthermore, we investigated whether tissue expression of GABA(A)R subunits α4 and δ, which constitute part of tonic GABA(A)Rs in the VP region, is altered in the stargazer mouse. Semi-quantitative Western blotting showed a significant increase in GABA(A)R α4 and δ subunits in the VP region of stargazer thalamus, which would indicate an increase in tonic GABA(A)R expression. Our findings show that there are changes in the levels of both phasic and tonic GABA(A)Rs in the VP thalamus; altered GABAergic inhibition within the VP could be one of many mechanisms contributing to the generation of absence seizures in this model.
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Maheshwari A, Noebels JL. Monogenic models of absence epilepsy: windows into the complex balance between inhibition and excitation in thalamocortical microcircuits. PROGRESS IN BRAIN RESEARCH 2014; 213:223-52. [PMID: 25194492 DOI: 10.1016/b978-0-444-63326-2.00012-0] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Absence epilepsy is a common disorder that arises in childhood and can be refractory to medical treatment. Single genetic mutations in mice, at times found in patients with absence epilepsy, provide the unique opportunity to bridge the gap between dysfunction at the genetic level and pathological oscillations within the thalamocortical circuit. Interestingly, unlike other forms of epilepsy, only genes related to ion channels have so far been linked to absence phenotypes. Here, we delineate a paradigm which attempts to unify the various monogenic models based on decades of research. While reviewing the particular impact of these individual mutations, we posit a framework involving fast feedforward disinhibition as one common mechanism that can lead to increased tonic inhibition in the cortex and/or thalamus. Enhanced tonic inhibition hyperpolarizes principal cells, deinactivates T-type calcium channels, and leads to reciprocal burst firing within the thalamocortical loop. We also review data from pharmacologic and polygenic models in light of this paradigm. Ultimately, many questions remain unanswered regarding the pathogenesis of absence epilepsy.
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Affiliation(s)
- Atul Maheshwari
- Department of Neurology, Developmental Neurogenetics Laboratory, Baylor College of Medicine Houston, TX, USA.
| | - Jeffrey L Noebels
- Department of Neurology, Developmental Neurogenetics Laboratory, Baylor College of Medicine Houston, TX, USA; Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
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