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Nguyen TD, Ishibashi M, Sinha AS, Watanabe M, Kato D, Horiuchi H, Wake H, Fukuda A. Astrocytic NKCC1 inhibits seizures by buffering Cl - and antagonizing neuronal NKCC1 at GABAergic synapses. Epilepsia 2023; 64:3389-3403. [PMID: 37779224 DOI: 10.1111/epi.17784] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 09/29/2023] [Accepted: 09/29/2023] [Indexed: 10/03/2023]
Abstract
OBJECTIVE A pathological excitatory action of the major inhibitory neurotransmitter γ-aminobutyric acid (GABA) has been observed in epilepsy. Blocking the Cl- importer NKCC1 with bumetanide is expected to reduce the neuronal intracellular Cl- concentration ([Cl- ]i ) and thereby attenuate the excitatory GABA response. Accordingly, several clinical trials of bumetanide for epilepsy were conducted. Although NKCC1 is expressed in both neurons and glial cells, an involvement of glial NKCC1 in seizures has not yet been reported. Astrocytes maintain high [Cl- ]i with NKCC1, and this gradient promotes Cl- efflux via the astrocytic GABAA receptor (GABAA R). This Cl- efflux buffers the synaptic cleft Cl- concentration to maintain the postsynaptic Cl- gradient during intense firing of GABAergic neurons, thereby sustaining its inhibitory action during seizure. In this study, we investigated the function of astrocytic NKCC1 in modulating the postsynaptic action of GABA in acute seizure models. METHODS We used the astrocyte-specific conditional NKCC1 knockout (AstroNKCC1KO) mice. The seizurelike events (SLEs) in CA1 pyramidal neurons were triggered by tetanic stimulation of stratum radiatum in acute hippocampus slices. The SLE underlying GABAA R-mediated depolarization was evaluated by applying the GABAA R antagonist bicuculline. The pilocarpine-induced seizure in vivo was monitored in adult mice by the Racine scale. The SLE duration and tetanus stimulation intensity threshold and seizure behavior in AstroNKCC1KO mice and wild-type (WT) mice were compared. RESULTS The AstroNKCC1KO mice were prone to seizures with lower threshold and longer duration of SLEs and larger GABAA R-mediated depolarization underlying the SLEs, accompanied by higher Racine-scored seizures. Bumetanide reduced these indicators of seizure in AstroNKCC1KO mice (which still express neuronal NKCC1), but not in the WT, both in vitro and in vivo. SIGNIFICANCE Astrocytic NKCC1 inhibits GABA-mediated excitatory action during seizures, whereas neuronal NKCC1 has the converse effect, suggesting opposing actions of bumetanide on these cells.
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Affiliation(s)
- Trong Dao Nguyen
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Masaru Ishibashi
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Adya Saran Sinha
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Miho Watanabe
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Daisuke Kato
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Hiroshi Horiuchi
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Hiroaki Wake
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Atsuo Fukuda
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, Japan
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Graham RT, Parrish RR, Alberio L, Johnson EL, Owens L, Trevelyan AJ. Optogenetic stimulation reveals a latent tipping point in cortical networks during ictogenesis. Brain 2023; 146:2814-2827. [PMID: 36572952 PMCID: PMC10316782 DOI: 10.1093/brain/awac487] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2022] [Revised: 11/17/2022] [Accepted: 12/06/2022] [Indexed: 12/28/2022] Open
Abstract
Brain-state transitions are readily apparent from changes in brain rhythms,1 but are difficult to predict, suggestive that the underlying cause is latent to passive recording methods. Among the most important transitions, clinically, are the starts of seizures. We here show that an 'active probing' approach may have several important benefits for epileptic management, including by helping predict these transitions. We used mice expressing the optogenetic actuator, channelrhodopsin, in pyramidal cells, allowing this population to be stimulated in isolation. Intermittent stimulation at frequencies as low as 0.033 Hz (period = 30 s) delayed the onset of seizure-like events in an acute brain slice model of ictogenesis, but the effect was lost if stimulation was delivered at even lower frequencies (1/min). Notably, active probing additionally provides advance indication of when seizure-like activity is imminent, revealed by monitoring the postsynaptic response to stimulation. The postsynaptic response, recorded extracellularly, showed an all-or-nothing change in both amplitude and duration, a few hundred seconds before seizure-like activity began-a sufficient length of time to provide a helpful warning of an impending seizure. The change in the postsynaptic response then persisted for the remainder of the recording, indicative of a state change from a pre-epileptic to a pro-epileptic network. This occurred in parallel with a large increase in the stimulation-triggered Ca2+ entry into pyramidal dendrites, and a step increase in the number of evoked postsynaptic action potentials, both consistent with a reduction in the threshold for dendritic action potentials. In 0 Mg2+ bathing media, the reduced threshold was not associated with changes in glutamatergic synaptic function, nor of GABAergic release from either parvalbumin or somatostatin interneurons, but simulations indicate that the step change in the optogenetic response can instead arise from incremental increases in intracellular [Cl-]. The change in the response to stimulation was replicated by artificially raising intracellular [Cl-], using the optogenetic chloride pump, halorhodopsin. By contrast, increases in extracellular [K+] cannot account for the firing patterns in the response to stimulation, although this, and other cellular changes, may contribute to ictal initiation in other circumstances. We describe how these various cellular changes form a synergistic network of positive feedback mechanisms, which may explain the precipitous nature of seizure onset. This model of seizure initiation draws together several major lines of epilepsy research as well as providing an important proof-of-principle regarding the utility of open-loop brain stimulation for clinical management of the condition.
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Affiliation(s)
- Robert T Graham
- Medical School, Newcastle University Biosciences Institute, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - R Ryley Parrish
- Medical School, Newcastle University Biosciences Institute, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Laura Alberio
- Medical School, Newcastle University Biosciences Institute, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Emily L Johnson
- Medical School, Newcastle University Biosciences Institute, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Laura Owens
- Medical School, Newcastle University Biosciences Institute, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Andrew J Trevelyan
- Medical School, Newcastle University Biosciences Institute, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
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Călin A, Waseem T, Raimondo JV, Newey SE, Akerman CJ. A genetically targeted ion sensor reveals distinct seizure-related chloride and pH dynamics in GABAergic interneuron populations. iScience 2023; 26:106363. [PMID: 37034992 PMCID: PMC10074576 DOI: 10.1016/j.isci.2023.106363] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2022] [Revised: 02/03/2023] [Accepted: 03/05/2023] [Indexed: 03/12/2023] Open
Abstract
Intracellular chloride and pH play fundamental roles in determining a neuron's synaptic inhibition and excitability. Yet it has been difficult to measure changes in these ions during periods of heightened network activity, such as occur in epilepsy. Here we develop a version of the fluorescent reporter, ClopHensorN, to enable simultaneous quantification of chloride and pH in genetically defined neurons during epileptiform activity. We compare pyramidal neurons to the major GABAergic interneuron subtypes in the mouse hippocampus, which express parvalbumin (PV), somatostatin (SST), or vasoactive intestinal polypeptide (VIP). Interneuron populations exhibit higher baseline chloride, with PV interneurons exhibiting the highest levels. During an epileptiform discharge, however, all subtypes converge upon a common elevated chloride level. Concurrent with these dynamics, epileptiform activity leads to different degrees of intracellular acidification, which reflect baseline pH. Thus, a new optical tool for dissociating chloride and pH reveals neuron-specific ion dynamics during heightened network activity.
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Affiliation(s)
- Alexandru Călin
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | - Tatiana Waseem
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | - Joseph V. Raimondo
- Division of Cell Biology, Department of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town 7925, South Africa
| | - Sarah E. Newey
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | - Colin J. Akerman
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
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4
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Egawa K, Watanabe M, Shiraishi H, Sato D, Takahashi Y, Nishio S, Fukuda A. Imbalanced expression of cation-chloride cotransporters as a potential therapeutic target in an Angelman syndrome mouse model. Sci Rep 2023; 13:5685. [PMID: 37069177 PMCID: PMC10110603 DOI: 10.1038/s41598-023-32376-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 03/27/2023] [Indexed: 04/19/2023] Open
Abstract
Angelman syndrome is a neurodevelopmental disorder caused by loss of function of the maternally expressed UBE3A gene. Treatments for the main manifestations, including cognitive dysfunction or epilepsy, are still under development. Recently, the Cl- importer Na+-K+-Cl- cotransporter 1 (NKCC1) and the Cl- exporter K+-Cl- cotransporter 2 (KCC2) have garnered attention as therapeutic targets for many neurological disorders. Dysregulation of neuronal intracellular Cl- concentration ([Cl-]i) is generally regarded as one of the mechanisms underlying neuronal dysfunction caused by imbalanced expression of these cation-chloride cotransporters (CCCs). Here, we analyzed the regulation of [Cl-]i and the effects of bumetanide, an NKCC1 inhibitor, in Angelman syndrome models (Ube3am-/p+ mice). We observed increased NKCC1 expression and decreased KCC2 expression in the hippocampi of Ube3am-/p+ mice. The average [Cl-]i of CA1 pyramidal neurons was not significantly different but demonstrated greater variance in Ube3am-/p+ mice. Tonic GABAA receptor-mediated Cl- conductance was reduced, which may have contributed to maintaining the normal average [Cl-]i. Bumetanide administration restores cognitive dysfunction in Ube3am-/p+ mice. Seizure susceptibility was also reduced regardless of the genotype. These results suggest that an imbalanced expression of CCCs is involved in the pathophysiological mechanism of Ube3am-/p+ mice, although the average [Cl-]i is not altered. The blockage of NKCC1 may be a potential therapeutic strategy for patients with Angelman syndrome.
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Affiliation(s)
- Kiyoshi Egawa
- Department of Pediatrics, Hokkaido University Graduate School of Medicine, Kita 15, Nishi 7, Kita-Ku, Sapporo, 060-8638, Japan.
| | - Miho Watanabe
- Department of Neurophysiology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-Ku, Hamamatsu City, Shizuoka, 431-3192, Japan
| | - Hideaki Shiraishi
- Department of Pediatrics, Hokkaido University Graduate School of Medicine, Kita 15, Nishi 7, Kita-Ku, Sapporo, 060-8638, Japan
| | - Daisuke Sato
- Department of Pediatrics, Hokkaido University Graduate School of Medicine, Kita 15, Nishi 7, Kita-Ku, Sapporo, 060-8638, Japan
| | - Yukitoshi Takahashi
- Department of Clinical Research, National Epilepsy Center, NHO, Shizuoka Institute of Epilepsy and Neurological Disorders, Urushiyama 886, Aoi-Ku, Shizuoka, 420-8688, Japan
| | - Saori Nishio
- Department of Rheumatology, Endocrinology, and Nephrology, Hokkaido University Graduate School of Medicine, Kita 15, Nishi 7, Kita-Ku, Sapporo, 060-8638, Japan
| | - Atsuo Fukuda
- Department of Neurophysiology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-Ku, Hamamatsu City, Shizuoka, 431-3192, Japan
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5
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Untiet V, Beinlich FRM, Kusk P, Kang N, Ladrón-de-Guevara A, Song W, Kjaerby C, Andersen M, Hauglund N, Bojarowska Z, Sigurdsson B, Deng S, Hirase H, Petersen NC, Verkhratsky A, Nedergaard M. Astrocytic chloride is brain state dependent and modulates inhibitory neurotransmission in mice. Nat Commun 2023; 14:1871. [PMID: 37015909 PMCID: PMC10073105 DOI: 10.1038/s41467-023-37433-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Accepted: 03/15/2023] [Indexed: 04/06/2023] Open
Abstract
Information transfer within neuronal circuits depends on the balance and recurrent activity of excitatory and inhibitory neurotransmission. Chloride (Cl-) is the major central nervous system (CNS) anion mediating inhibitory neurotransmission. Astrocytes are key homoeostatic glial cells populating the CNS, although the role of these cells in regulating excitatory-inhibitory balance remains unexplored. Here we show that astrocytes act as a dynamic Cl- reservoir regulating Cl- homoeostasis in the CNS. We found that intracellular chloride concentration ([Cl-]i) in astrocytes is high and stable during sleep. In awake mice astrocytic [Cl-]i is lower and exhibits large fluctuation in response to both sensory input and motor activity. Optogenetic manipulation of astrocytic [Cl-]i directly modulates neuronal activity during locomotion or whisker stimulation. Astrocytes thus serve as a dynamic source of extracellular Cl- available for GABAergic transmission in awake mice, which represents a mechanism for modulation of the inhibitory tone during sustained neuronal activity.
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Affiliation(s)
- Verena Untiet
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Copenhagen, 2200, Copenhagen, Denmark.
| | - Felix R M Beinlich
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Peter Kusk
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Ning Kang
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, Department of Neurosurgery, University of Rochester Medical Center, Rochester, NY, 14642, USA
| | - Antonio Ladrón-de-Guevara
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, Department of Neurosurgery, University of Rochester Medical Center, Rochester, NY, 14642, USA
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA
| | - Wei Song
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, Department of Neurosurgery, University of Rochester Medical Center, Rochester, NY, 14642, USA
| | - Celia Kjaerby
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Mie Andersen
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Natalie Hauglund
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Zuzanna Bojarowska
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Björn Sigurdsson
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Saiyue Deng
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, P.R. China
| | - Hajime Hirase
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Nicolas C Petersen
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Alexei Verkhratsky
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Copenhagen, 2200, Copenhagen, Denmark.
- Faculty of Biology, Medicine and Health, The University of Manchester, Oxford Rd, Manchester, M13 9PL, UK.
- Achucarro Centre for Neuroscience, IKERBASQUE, Basque Foundation for Science, Plaza Euskadi 5, 48009, Bilbao, Spain.
| | - Maiken Nedergaard
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Copenhagen, 2200, Copenhagen, Denmark.
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, Department of Neurosurgery, University of Rochester Medical Center, Rochester, NY, 14642, USA.
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6
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Pressey JC, de Saint-Rome M, Raveendran VA, Woodin MA. Chloride transporters controlling neuronal excitability. Physiol Rev 2023; 103:1095-1135. [PMID: 36302178 DOI: 10.1152/physrev.00025.2021] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Synaptic inhibition plays a crucial role in regulating neuronal excitability, which is the foundation of nervous system function. This inhibition is largely mediated by the neurotransmitters GABA and glycine that activate Cl--permeable ion channels, which means that the strength of inhibition depends on the Cl- gradient across the membrane. In neurons, the Cl- gradient is primarily mediated by two secondarily active cation-chloride cotransporters (CCCs), NKCC1 and KCC2. CCC-mediated regulation of the neuronal Cl- gradient is critical for healthy brain function, as dysregulation of CCCs has emerged as a key mechanism underlying neurological disorders including epilepsy, neuropathic pain, and autism spectrum disorder. This review begins with an overview of neuronal chloride transporters before explaining the dependent relationship between these CCCs, Cl- regulation, and inhibitory synaptic transmission. We then discuss the evidence for how CCCs can be regulated, including by activity and their protein interactions, which underlie inhibitory synaptic plasticity. For readers who may be interested in conducting experiments on CCCs and neuronal excitability, we have included a section on techniques for estimating and recording intracellular Cl-, including their advantages and limitations. Although the focus of this review is on neurons, we also examine how Cl- is regulated in glial cells, which in turn regulate neuronal excitability through the tight relationship between this nonneuronal cell type and synapses. Finally, we discuss the relatively extensive and growing literature on how CCC-mediated neuronal excitability contributes to neurological disorders.
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Affiliation(s)
- Jessica C Pressey
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Miranda de Saint-Rome
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Vineeth A Raveendran
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Melanie A Woodin
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
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Recruitment of interictal- and ictal-like discharges in posterior piriform cortex by delta-rate (1–4 Hz) focal bursts in anterior piriform cortex in vivo. Epilepsy Res 2022; 187:107032. [DOI: 10.1016/j.eplepsyres.2022.107032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Revised: 09/10/2022] [Accepted: 10/06/2022] [Indexed: 11/23/2022]
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8
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Lodovichi C, Ratto GM, Trevelyan AJ, Arosio D. Genetically encoded sensors for Chloride concentration. J Neurosci Methods 2022; 368:109455. [PMID: 34952088 DOI: 10.1016/j.jneumeth.2021.109455] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 12/11/2021] [Accepted: 12/18/2021] [Indexed: 12/12/2022]
Abstract
Insights into chloride regulation in neurons have come slowly, but they are likely to be critical for our understanding of how the brain works. The reason is that the intracellular Cl- level ([Cl-]i) is the key determinant of synaptic inhibitory function, and this in turn dictates all manner of neuronal network function. The true impact on the network will only be apparent, however, if Cl- is measured at many locations at once (multiple neurons, and also across the subcellular compartments of single neurons), which realistically, can only be achieved using imaging. The development of genetically-encoded anion biosensors (GABs) brings the additional benefit that Cl- imaging may be done in identified cell-classes and hopefully in subcellular compartments. Here, we describe the historical background and motivation behind the development of these sensors and how they have been used so far. There are, however, still major limitations for their use, the most important being the fact that all GABs are sensitive to both pH and Cl-. Disambiguating the two signals has proved a major challenge, but there are potential solutions; notable among these is ClopHensor, which has now been developed for in vivo measurements of both ion species. We also speculate on how these biosensors may yet be improved, and how this could advance our understanding of Cl- regulation and its impact on brain function.
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Affiliation(s)
- Claudia Lodovichi
- Neuroscience Institute-CNR, Depart. Biomedical Sciences, Unipd, Padova, Veneto Institute of Molecular Medicine, Padova Neuroscience Center, Padova, Italy.
| | - Gian Michele Ratto
- National Enterprise for nanoScience and nanoTechnology (NEST), Istituto Nanoscienze, Consiglio Nazionale delle Ricerche (CNR) and Scuola Normale Superiore Pisa, 56127 Pisa, Italy
| | - Andrew J Trevelyan
- Newcastle University Biosciences Institute, Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
| | - Daniele Arosio
- Consiglio Nazionale delle Ricerche (CNR), Istituto di Biofisica, 38123 Trento, Italy.
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9
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Lacaille H, Vacher CM, Penn AA. Preterm Birth Alters the Maturation of the GABAergic System in the Human Prefrontal Cortex. Front Mol Neurosci 2022; 14:827370. [PMID: 35185465 PMCID: PMC8852329 DOI: 10.3389/fnmol.2021.827370] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 12/31/2021] [Indexed: 11/13/2022] Open
Abstract
Developmental changes in GABAergic and glutamatergic systems during frontal lobe development have been hypothesized to play a key role in neurodevelopmental disorders seen in children born very preterm or at/with low birth weight, but the associated cellular changes have not yet been identified. Here we studied the molecular development of the GABAergic system specifically in the dorsolateral prefrontal cortex, a region that has been implicated in neurodevelopmental and psychiatric disorders. The maturation state of the GABAergic system in this region was assessed in human post-mortem brain samples, from term infants ranging in age from 0 to 8 months (n = 17 male, 9 female). Gene expression was measured for 47 GABAergic genes and used to calculate a maturation index. This maturation index was significantly more dynamic in male than female infants. To evaluate the impact of premature birth on the GABAergic system development, samples from 1-month-old term (n = 9 male, 4 female) and 1-month corrected-age very preterm (n = 8 male, 6 female) infants, were compared using the same gene list and methodology. The maturation index for the GABAergic system was significantly lower (−50%, p < 0.05) in male preterm infants, with major alterations in genes linked to GABAergic function in astrocytes, suggesting astrocytic GABAergic developmental changes as a new cellular mechanism underlying preterm brain injury.
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Intricacies of GABA A Receptor Function: The Critical Role of the β3 Subunit in Norm and Pathology. Int J Mol Sci 2021; 22:ijms22031457. [PMID: 33535681 PMCID: PMC7867123 DOI: 10.3390/ijms22031457] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 01/27/2021] [Accepted: 01/28/2021] [Indexed: 12/23/2022] Open
Abstract
Neuronal intracellular chloride ([Cl−]i) is a key determinant in γ-aminobutyric acid type A (GABA)ergic signaling. γ-Aminobutyric acid type A receptors (GABAARs) mediate both inhibitory and excitatory neurotransmission, as the passive fluxes of Cl− and HCO3− via pores can be reversed by changes in the transmembrane concentration gradient of Cl−. The cation–chloride co-transporters (CCCs) are the primary systems for maintaining [Cl−]i homeostasis. However, despite extensive electrophysiological data obtained in vitro that are supported by a wide range of molecular biological studies on the expression patterns and properties of CCCs, the presence of ontogenetic changes in [Cl−]i—along with the consequent shift in GABA reversal potential—remain a subject of debate. Recent studies showed that the β3 subunit possesses properties of the P-type ATPase that participates in the ATP-consuming movement of Cl− via the receptor. Moreover, row studies have demonstrated that the β3 subunit is a key player in GABAAR performance and in the appearance of serious neurological disorders. In this review, we discuss the properties and driving forces of CCCs and Cl−, HCO3−ATPase in the maintenance of [Cl−]i homeostasis after changes in upcoming GABAAR function. Moreover, we discuss the contribution of the β3 subunit in the manifestation of epilepsy, autism, and other syndromes.
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11
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Lombardi A, Jedlicka P, Luhmann HJ, Kilb W. Coincident glutamatergic depolarizations enhance GABAA receptor-dependent Cl- influx in mature and suppress Cl- efflux in immature neurons. PLoS Comput Biol 2021; 17:e1008573. [PMID: 33465082 PMCID: PMC7845986 DOI: 10.1371/journal.pcbi.1008573] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 01/29/2021] [Accepted: 11/30/2020] [Indexed: 11/19/2022] Open
Abstract
The impact of GABAergic transmission on neuronal excitability depends on the Cl--gradient across membranes. However, the Cl--fluxes through GABAA receptors alter the intracellular Cl- concentration ([Cl-]i) and in turn attenuate GABAergic responses, a process termed ionic plasticity. Recently it has been shown that coincident glutamatergic inputs significantly affect ionic plasticity. Yet how the [Cl-]i changes depend on the properties of glutamatergic inputs and their spatiotemporal relation to GABAergic stimuli is unknown. To investigate this issue, we used compartmental biophysical models of Cl- dynamics simulating either a simple ball-and-stick topology or a reconstructed CA3 neuron. These computational experiments demonstrated that glutamatergic co-stimulation enhances GABA receptor-mediated Cl- influx at low and attenuates or reverses the Cl- efflux at high initial [Cl-]i. The size of glutamatergic influence on GABAergic Cl--fluxes depends on the conductance, decay kinetics, and localization of glutamatergic inputs. Surprisingly, the glutamatergic shift in GABAergic Cl--fluxes is invariant to latencies between GABAergic and glutamatergic inputs over a substantial interval. In agreement with experimental data, simulations in a reconstructed CA3 pyramidal neuron with physiological patterns of correlated activity revealed that coincident glutamatergic synaptic inputs contribute significantly to the activity-dependent [Cl-]i changes. Whereas the influence of spatial correlation between distributed glutamatergic and GABAergic inputs was negligible, their temporal correlation played a significant role. In summary, our results demonstrate that glutamatergic co-stimulation had a substantial impact on ionic plasticity of GABAergic responses, enhancing the attenuation of GABAergic inhibition in the mature nervous systems, but suppressing GABAergic [Cl-]i changes in the immature brain. Therefore, glutamatergic shift in GABAergic Cl--fluxes should be considered as a relevant factor of short-term plasticity. Information processing in the brain requires that excitation and inhibition are balanced. The main inhibitory neurotransmitter in the brain is gamma-amino-butyric acid (GABA). GABA actions depend on the Cl--gradient, but activation of ionotropic GABA receptors causes Cl--fluxes and thus reduces GABAergic inhibition. Here, we investigated how a coincident membrane depolarization by excitatory glutamatergic synapses influences GABA-induced Cl--fluxes using a biophysical compartmental model of Cl- dynamics, simulating either simple or realistic neuron topologies. We demonstrate that glutamatergic co-stimulation directly affects GABA-induced Cl--fluxes, with the size of glutamatergic effects depending on the conductance, the decay kinetics, and localization of glutamatergic inputs. We also show that the glutamatergic shift in GABAergic Cl--fluxes is surprisingly stable over a substantial range of latencies between glutamatergic and GABAergic inputs. We conclude from these results that glutamatergic co-stimulation alters GABAergic Cl--fluxes and in turn affects the strength of GABAergic inhibition. These coincidence-dependent ionic changes should be considered as a relevant factor of short-term plasticity in the CNS.
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Affiliation(s)
- Aniello Lombardi
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Mainz, Germany
| | - Peter Jedlicka
- ICAR3R - Interdisciplinary Centre for 3Rs in Animal Research, Faculty of Medicine, Justus-Liebig-University, Giessen, Germany
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University, Frankfurt/Main, Germany
- Frankfurt Institute for Advanced Studies, Frankfurt am Main, Germany
| | - Heiko J. Luhmann
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Mainz, Germany
| | - Werner Kilb
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Mainz, Germany
- * E-mail:
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12
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Wang Z, Feng Z, Yuan Y, Zheng L. Suppressing synchronous firing of epileptiform activity by high-frequency stimulation of afferent fibers in rat hippocampus. CNS Neurosci Ther 2020; 27:352-362. [PMID: 33325622 PMCID: PMC7871785 DOI: 10.1111/cns.13535] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 11/14/2020] [Accepted: 11/14/2020] [Indexed: 12/18/2022] Open
Abstract
Aims Deep brain stimulation (DBS) is a promising technology for treating epilepsy. However, the efficacy and underlying mechanisms of the high‐frequency stimulation (HFS) utilized by DBS to suppress epilepsy remain uncertain. Previous studies have shown that HFS can desynchronize the firing of neurons. In this study, we investigated whether the desynchronization effects of HFS can suppress epileptiform events. Methods HFS trains with seconds of duration (short) and a minute of duration (long) were applied at the afferent fibers (ie, Schaffer collaterals) of the hippocampal CA1 region in anesthetized rats in vivo. The amplitude and the rate of population spikes (PS) appeared in the downstream of stimulation were calculated to evaluate the intensity of synchronized firing of neuronal populations between short and long HFS groups. A test of paired‐pulse depression (PPD) was used to assess the alteration of inhibitory neuronal circuits. Results The sustained stimulation of a 60‐s long HFS suppressed the afterdischarges that were induced by a 5‐s short HFS to impair the local inhibitions. During the sustained HFS, the mean PS amplitude reduced significantly and the burst firing decreased, while the amount of neuronal firing did not change significantly. The paired‐pulse tests showed that with a similar baseline level of small PS2/PS1 ratio indicating a strong PPD, the 5‐s HFS increased the PS2/PS1 ratio to a value that was significantly greater than the corresponding ratio during sustained HFS, indicating that the PPD impaired by a short HFS may be restored by a sustained HFS. Conclusions The sustained HFS can desynchronize the population firing of epileptiform activity and accelerate a recovery of inhibitions to create a balance between the excitation and the inhibition of local neuronal circuits. The study provides new clues for further understanding the mechanism of DBS and for advancing the clinical application of DBS in treating epilepsy.
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Affiliation(s)
- Zhaoxiang Wang
- Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, China
| | - Zhouyan Feng
- Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, China
| | - Yue Yuan
- Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, China
| | - Lvpiao Zheng
- Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, China
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13
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Kolbaev SN, Mohapatra N, Chen R, Lombardi A, Staiger JF, Luhmann HJ, Jedlicka P, Kilb W. NKCC-1 mediated Cl - uptake in immature CA3 pyramidal neurons is sufficient to compensate phasic GABAergic inputs. Sci Rep 2020; 10:18399. [PMID: 33110147 PMCID: PMC7591924 DOI: 10.1038/s41598-020-75382-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 10/09/2020] [Indexed: 12/12/2022] Open
Abstract
Activation of GABAA receptors causes in immature neurons a functionally relevant decrease in the intracellular Cl- concentration ([Cl-]i), a process termed ionic plasticity. Amount and duration of ionic plasticity depends on kinetic properties of [Cl-]i homeostasis. In order to characterize the capacity of Cl- accumulation and to quantify the effect of persistent GABAergic activity on [Cl-]i, we performed gramicidin-perforated patch-clamp recordings from CA3 pyramidal neurons of immature (postnatal day 4-7) rat hippocampal slices. These experiments revealed that inhibition of NKCC1 decreased [Cl-]i toward passive distribution with a time constant of 381 s. In contrast, active Cl- accumulation occurred with a time constant of 155 s, corresponding to a rate of 15.4 µM/s. Inhibition of phasic GABAergic activity had no significant effect on steady state [Cl-]i. Inhibition of tonic GABAergic currents induced a significant [Cl-]i increase by 1.6 mM, while activation of tonic extrasynaptic GABAA receptors with THIP significantly reduced [Cl-]i.. Simulations of neuronal [Cl-]i homeostasis supported the observation, that basal levels of synaptic GABAergic activation do not affect [Cl-]i. In summary, these results indicate that active Cl--uptake in immature hippocampal neurons is sufficient to maintain stable [Cl-]i at basal levels of phasic and to some extent also to compensate tonic GABAergic activity.
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Affiliation(s)
- Sergey N Kolbaev
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Duesbergweg 6, 55128, Mainz, Germany.,Research Center of Neurology, Volokolamskoyeshosse, 80, Moscow, Russia, 125367
| | - Namrata Mohapatra
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe-University, Theodor-Stern-Kai 7, 60590, Frankfurt, Germany
| | - Rongqing Chen
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Duesbergweg 6, 55128, Mainz, Germany.,Department of Neurobiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, 510515, China
| | - Aniello Lombardi
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Duesbergweg 6, 55128, Mainz, Germany
| | - Jochen F Staiger
- Institute of Neuroanatomy, Universitätsmedizin Göttingen, Georg-August-Universität Göttingen, Kreuzbergring 36, 37075, Göttingen, Germany
| | - Heiko J Luhmann
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Duesbergweg 6, 55128, Mainz, Germany
| | - Peter Jedlicka
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe-University, Theodor-Stern-Kai 7, 60590, Frankfurt, Germany.,ICAR3R-Interdisciplinary Centre for 3Rs in Animal Research, Faculty of Medicine, Justus-Liebig-University, Rudolf-Buchheim-Str. 6, 35392, Giessen, Germany
| | - Werner Kilb
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Duesbergweg 6, 55128, Mainz, Germany.
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14
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Woo J, Jang MW, Lee J, Koh W, Mikoshiba K, Lee CJ. The molecular mechanism of synaptic activity-induced astrocytic volume transient. J Physiol 2020; 598:4555-4572. [PMID: 32706443 DOI: 10.1113/jp279741] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Accepted: 07/20/2020] [Indexed: 12/16/2022] Open
Abstract
KEY POINTS Neuronal activity causes astrocytic volume change via K+ uptake through TREK-1 containing two-pore domain potassium channels. The volume transient is terminated by Cl- efflux through the Ca2+ -activated anion channel BEST1. The source of the Ca2+ required to open BEST1 appears to be the stretch-activated TRPA1 channel. Intense neuronal activity is synaptically coupled with a physical change in astrocytes via volume transients. ABSTRACT The brain volume changes dynamically and transiently upon intense neuronal activity through a tight regulation of ion concentrations and water movement across the plasma membrane of astrocytes. We have recently demonstrated that an intense neuronal activity and subsequent astrocytic AQP4-dependent volume transient are critical for synaptic plasticity and memory. We have also pharmacologically demonstrated a functional coupling between synaptic activity and the astrocytic volume transient. However, the precise molecular mechanisms of how intense neuronal activity and the astrocytic volume transient are coupled remain unclear. Here we utilized an intrinsic optical signal imaging technique combined with fluorescence imaging using ion sensitive dyes and molecular probes and electrophysiology to investigate the detailed molecular mechanisms in genetically modified mice. We report that a brief synaptic activity induced by a train stimulation (20 Hz, 1 s) causes a prolonged astrocytic volume transient (80 s) via K+ uptake through TREK-1 containing two-pore domain potassium (K2P) channels, but not Kir4.1 or NKCC1. This volume change is terminated by Cl- efflux through the Ca2+ -activated anion channel BEST1, but not the volume-regulated anion channel TTYH. The source of the Ca2+ required to open BEST1 appears to be the stretch-activated TRPA1 channel in astrocytes, but not IP3 R2. In summary, our study identifies several important astrocytic ion channels (AQP4, TREK-1, BEST1, TRPA1) as the key molecules leading to the neuronal activity-dependent volume transient in astrocytes. Our findings reveal new molecular and cellular mechanisms for the synaptic coupling of intense neuronal activity with a physical change in astrocytes via volume transients.
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Affiliation(s)
- Junsung Woo
- Center for Glia-Neuron Interaction, Korea Institute of Science and Technology (KIST), Seoul, 02792, Republic of Korea
| | - Minwoo Wendy Jang
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, Republic of Korea.,Center for Cognition and Sociality, Institute for Basic Science (IBS), Daejeon, 34126, Republic of Korea
| | - Jaekwang Lee
- Center for Glia-Neuron Interaction, Korea Institute of Science and Technology (KIST), Seoul, 02792, Republic of Korea
| | - Wuhyun Koh
- Center for Cognition and Sociality, Institute for Basic Science (IBS), Daejeon, 34126, Republic of Korea.,Department of Neuroscience, Division of Bio-Medical Science & Technology, KIST School, Korea University of Science and Technology (UST), Seoul, 02792, Republic of Korea
| | - Katsuhiko Mikoshiba
- Laboratory for Developmental Biology, RIKEN Brain Science Institute, Hirosawa 2-1, Wako, Saitama, 351-0198, Japan
| | - C Justin Lee
- Center for Glia-Neuron Interaction, Korea Institute of Science and Technology (KIST), Seoul, 02792, Republic of Korea.,KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, Republic of Korea.,Center for Cognition and Sociality, Institute for Basic Science (IBS), Daejeon, 34126, Republic of Korea.,Department of Neuroscience, Division of Bio-Medical Science & Technology, KIST School, Korea University of Science and Technology (UST), Seoul, 02792, Republic of Korea
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15
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Akita T, Fukuda A. Intracellular Cl - dysregulation causing and caused by pathogenic neuronal activity. Pflugers Arch 2020; 472:977-987. [PMID: 32300887 DOI: 10.1007/s00424-020-02375-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 03/23/2020] [Accepted: 03/27/2020] [Indexed: 02/06/2023]
Abstract
The intracellular Cl- concentration ([Cl-]i) is tightly regulated in brain neurons for stabilizing brain performance. The [Cl-]i in mature neurons is determined by the balance between the rate of Cl- extrusion mainly mediated by the neuron-specific type 2 K+-Cl- cotransporter (KCC2) and the rate of Cl- entry through various Cl- channels including GABAA receptors during neuronal activity. Disturbance of the balance causes instability of brain circuit performance and may lead to epileptic seizures. In the first part of this review, we discuss how genetic alterations in KCC2 in humans cause infantile migrating focal seizures, based on our previous report and others. Depolarization of the membrane potential increases the driving force for Cl- entry into neurons. Thus, the duration of action potential spike generation and the frequency of excitatory synaptic inputs are the crucial factors for determining the total amount of Cl- entry and the equilibrium [Cl-]i in neurons. Moreover, there is also a significant interdependence between the neuronal activity and the KCC2 expression. In the second part, we discuss plausible mechanisms by which excessive neuronal activity due to excitotoxic brain insults or other epilepsy-associated gene mutations may cause the Cl- imbalance in neurons and lead to epileptic discharges over the brain, using the schematic "unifying foci" model based on literature.
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Affiliation(s)
- Tenpei Akita
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, 431-3192, Japan.
| | - Atsuo Fukuda
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, 431-3192, Japan
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16
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Menzikov SA, Zaichenko DM, Moskovtsev AA, Morozov SG, Kubatiev AA. Ectopic GABA A receptor β3 subunit determines Cl - / HCO 3 - -ATPase and chloride transport in HEK 293FT cells. FEBS J 2020; 288:699-712. [PMID: 32383536 DOI: 10.1111/febs.15359] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 04/09/2020] [Accepted: 05/04/2020] [Indexed: 01/20/2023]
Abstract
Neuronal intracellular chloride concentration ([Cl- ]i ) is a crucial determinant of transmission mediated by the γ-aminobutyric acid type A receptor (GABAA R), which subserves synaptic and extrasynaptic inhibition as well as excitation. The Cl- ion is the main carrier of charge through the GABAA R; however, bicarbonate ions ( HCO 3 - ) flowing in the opposite direction can also contribute to the net current. The direction of Cl- and HCO 3 - fluxes is determined by the underlying electrochemical gradient, which is controlled by Cl- transporters and channels. Accumulating evidence suggests that active mechanisms of chloride transport across the GABAA R pore can underlie the regulation of [Cl- ]i . Measurement of Cl- / HCO 3 - -ATPase activity and Cl- transport in HEK 293FT cells expressing homomeric or heteromeric GABAA R ensembles (α2, β3, or γ2) with fluorescent dye for chloride demonstrated that receptor subtypes containing the β3 subunit show enzymatic activity and participate in GABA-mediated or ATP-dependent Cl- transport. GABA-mediated flow of Cl- ions into and out of the cells occurred for a short time period but then rapidly declined. However, Cl- ion flux was stabilized for a long time period in the presence of HCO 3 - ions. The reconstituted β3 subunit isoform, purified as a fusion protein, confirmed that β3 is critical for ATPase; however, only the triplet variant showed the full receptor function. The high sensitivity of the enzyme to γ-phosphate inhibitors led us to postulate that the β3 subunit is catalytic. Our discovery of a GABAA R type that requires ATP consumption for chloride movement provides new insight into the molecular mechanisms of inhibitory signaling.
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Affiliation(s)
| | | | - Aleksey A Moskovtsev
- Institute of General Pathology and Pathophysiology, Moscow, Russia.,Russian Medical Academy of Postdoctoral Education, Moscow, Russia
| | - Sergey G Morozov
- Institute of General Pathology and Pathophysiology, Moscow, Russia
| | - Aslan A Kubatiev
- Institute of General Pathology and Pathophysiology, Moscow, Russia.,Russian Medical Academy of Postdoctoral Education, Moscow, Russia
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17
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Burman RJ, Selfe JS, Lee JH, van den Berg M, Calin A, Codadu NK, Wright R, Newey SE, Parrish RR, Katz AA, Wilmshurst JM, Akerman CJ, Trevelyan AJ, Raimondo JV. Excitatory GABAergic signalling is associated with benzodiazepine resistance in status epilepticus. Brain 2020; 142:3482-3501. [PMID: 31553050 DOI: 10.1093/brain/awz283] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Revised: 06/10/2019] [Accepted: 07/11/2019] [Indexed: 01/17/2023] Open
Abstract
Status epilepticus is defined as a state of unrelenting seizure activity. Generalized convulsive status epilepticus is associated with a rapidly rising mortality rate, and thus constitutes a medical emergency. Benzodiazepines, which act as positive modulators of chloride (Cl-) permeable GABAA receptors, are indicated as first-line treatment, but this is ineffective in many cases. We found that 48% of children presenting with status epilepticus were unresponsive to benzodiazepine treatment, and critically, that the duration of status epilepticus at the time of treatment is an important predictor of non-responsiveness. We therefore investigated the cellular mechanisms that underlie acquired benzodiazepine resistance, using rodent organotypic and acute brain slices. Removing Mg2+ ions leads to an evolving pattern of epileptiform activity, and eventually to a persistent state of repetitive discharges that strongly resembles clinical EEG recordings of status epilepticus. We found that diazepam loses its antiseizure efficacy and conversely exacerbates epileptiform activity during this stage of status epilepticus-like activity. Interestingly, a low concentration of the barbiturate phenobarbital had a similar exacerbating effect on status epilepticus-like activity, while a high concentration of phenobarbital was effective at reducing or preventing epileptiform discharges. We then show that the persistent status epilepticus-like activity is associated with a reduction in GABAA receptor conductance and Cl- extrusion capability. We explored the effect on intraneuronal Cl- using both gramicidin, perforated-patch clamp recordings and Cl- imaging. This showed that during status epilepticus-like activity, reduced Cl- extrusion capacity was further exacerbated by activity-dependent Cl- loading, resulting in a persistently high intraneuronal Cl-. Consistent with these results, we found that optogenetic stimulation of GABAergic interneurons in the status epilepticus-like state, actually enhanced epileptiform activity in a GABAAR dependent manner. Together our findings describe a novel potential mechanism underlying benzodiazepine-resistant status epilepticus, with relevance to how this life-threatening condition should be managed in the clinic.
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Affiliation(s)
- Richard J Burman
- Division of Cell Biology, Department of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,Department of Paediatric Neurology, Red Cross War Memorial Children's Hospital, Neuroscience Institute, University of Cape Town, Cape Town, South Africa.,Department of Pharmacology, University of Oxford, Oxford, UK
| | - Joshua S Selfe
- Division of Cell Biology, Department of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - John Hamin Lee
- Division of Cell Biology, Department of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Maurits van den Berg
- Division of Cell Biology, Department of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Alexandru Calin
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Neela K Codadu
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne, NE24HH, UK
| | - Rebecca Wright
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Sarah E Newey
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - R Ryley Parrish
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne, NE24HH, UK
| | - Arieh A Katz
- Division of Medical Biochemistry, Department of Integrated Biomedical Sciences and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Jo M Wilmshurst
- Department of Paediatric Neurology, Red Cross War Memorial Children's Hospital, Neuroscience Institute, University of Cape Town, Cape Town, South Africa
| | - Colin J Akerman
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Andrew J Trevelyan
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne, NE24HH, UK
| | - Joseph V Raimondo
- Division of Cell Biology, Department of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
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18
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Fukuda A. Chloride homeodynamics underlying modal shifts in cellular and network oscillations. Neurosci Res 2020; 156:14-23. [PMID: 32105770 DOI: 10.1016/j.neures.2020.02.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2019] [Revised: 11/22/2019] [Accepted: 02/21/2020] [Indexed: 11/16/2022]
Abstract
γ-Aminobutyric acid (GABA) generally induces hyperpolarization and inhibition in the adult brain, but causes depolarization (and can be excitatory) in the immature brain. Depolarizing GABA actions are necessary for neurogenesis, differentiation, migration, and synaptogenesis. Additionally, the conversion of GABA responses from inhibition to excitation can be induced in adults by pathological conditions. Because GABAA receptors are Cl- channels, alternating GABA actions between hyperpolarization (Cl- influx) and depolarization (Cl- efflux) are induced by changes in the Cl- gradient, which is regulated by C- transporters. Thus, the dynamics of neural functions are modulated by active Cl- homeostasis (Cl- homeodynamics), alternating inhibition and excitation, and could underlie the modal shifts in cellular and network oscillations. Such a modal shift in GABA actions is required for normal development. Thus disturbances in this developmental GABA modal shift and/or the induction of excitatory GABA action in adult could underlie the pathogenesis of diverse neurological diseases (so-called network diseases).
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Affiliation(s)
- Atsuo Fukuda
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, Japan; Advanced Research Facilities and Services, Preeminent Medical Photonics Education and Research Center, Hamamatsu University School of Medicine, Hamamatsu, Japan.
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19
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Halbhuber L, Achtner C, Luhmann HJ, Sinning A, Kilb W. Coincident Activation of Glutamate Receptors Enhances GABA A Receptor-Induced Ionic Plasticity of the Intracellular Cl --Concentration in Dissociated Neuronal Cultures. Front Cell Neurosci 2019; 13:497. [PMID: 31787883 PMCID: PMC6856009 DOI: 10.3389/fncel.2019.00497] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 10/21/2019] [Indexed: 01/09/2023] Open
Abstract
Massive activation of γ-amino butyric acid A (GABAA) receptors during pathophysiological activity induces an increase in the intracellular Cl--concentration ([Cl-]i), which is sufficient to render GABAergic responses excitatory. However, to what extent physiological levels of GABAergic activity can influence [Cl-]i is not known. Aim of the present study is to reveal whether moderate activation of GABAA receptors mediates functionally relevant [Cl-]i changes and whether these changes can be augmented by coincident glutamatergic activity. To address these questions, we used whole-cell patch-clamp recordings from cultured cortical neurons [at days in vitro (DIV) 6-22] to determine changes in the GABA reversal potential (EGABA) induced by short bursts of GABAergic and/or synchronized glutamatergic stimulation. These experiments revealed that pressure-application of 10 short muscimol pulses at 10 Hz induced voltage-dependent [Cl-]i changes. Under current-clamp conditions this muscimol burst induced a [Cl-]i increase of 3.1 ± 0.4 mM (n = 27), which was significantly enhanced to 4.6 ± 0.5 mM (n = 27) when glutamate was applied synchronously with the muscimol pulses. The muscimol-induced [Cl-]i increase significantly attenuated the inhibitory effect of GABA, as determined by the GABAergic rheobase shift. The synchronous coapplication of glutamate pulses had no additional effect on the attenuation of GABAergic inhibition, despite the larger [Cl-]i transients under these conditions. In summary, these results indicate that moderate GABAergic activity can induce functionally relevant [Cl-]i transients, which were enhanced by coincident glutamate pulses. This ionic plasticity of [Cl-]i may contribute to short-term plasticity of the GABAergic system.
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Affiliation(s)
- Lisa Halbhuber
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Mainz, Germany
| | - Cécilia Achtner
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Mainz, Germany
| | - Heiko J Luhmann
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Mainz, Germany
| | - Anne Sinning
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Mainz, Germany
| | - Werner Kilb
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Mainz, Germany
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20
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Watanabe M, Zhang J, Mansuri MS, Duan J, Karimy JK, Delpire E, Alper SL, Lifton RP, Fukuda A, Kahle KT. Developmentally regulated KCC2 phosphorylation is essential for dynamic GABA-mediated inhibition and survival. Sci Signal 2019; 12:eaaw9315. [PMID: 31615901 PMCID: PMC7219477 DOI: 10.1126/scisignal.aaw9315] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Despite its importance for γ-aminobutyric acid (GABA) inhibition and involvement in neurodevelopmental disease, the regulatory mechanisms of the K+/Cl- cotransporter KCC2 (encoded by SLC12A5) during maturation of the central nervous system (CNS) are not entirely understood. Here, we applied quantitative phosphoproteomics to systematically map sites of KCC2 phosphorylation during CNS development in the mouse. KCC2 phosphorylation at Thr906 and Thr1007, which inhibits KCC2 activity, underwent dephosphorylation in parallel with the GABA excitatory-inhibitory sequence in vivo. Knockin mice expressing the homozygous phosphomimetic KCC2 mutations T906E/T1007E (Kcc2E/E ), which prevented the normal developmentally regulated dephosphorylation of these sites, exhibited early postnatal death from respiratory arrest and a marked absence of cervical spinal neuron respiratory discharges. Kcc2E/E mice also displayed disrupted lumbar spinal neuron locomotor rhythmogenesis and touch-evoked status epilepticus associated with markedly impaired KCC2-dependent Cl- extrusion. These data identify a previously unknown phosphorylation-dependent KCC2 regulatory mechanism during CNS development that is essential for dynamic GABA-mediated inhibition and survival.
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Affiliation(s)
- Miho Watanabe
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka 431-3192, Japan
| | - Jinwei Zhang
- Institute of Biomedical and Clinical Sciences, Medical School, College of Medicine and Health, University of Exeter, Hatherly Laboratories, Exeter EX4 4PS, UK
| | - M Shahid Mansuri
- Department of Neurosurgery, Yale School of Medicine, New Haven, CT 06510, USA
| | - Jingjing Duan
- Human Aging Research Institute, School of Life Sciences, Nanchang University, Nanchang, Jiangxi 330031, China
| | - Jason K Karimy
- Department of Neurosurgery, Yale School of Medicine, New Haven, CT 06510, USA
| | - Eric Delpire
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Seth L Alper
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215, USA
- The Broad Institute of Harvard and the Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Richard P Lifton
- Laboratory of Human Genetics and Genomics, The Rockefeller University, New York, NY, USA
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06511, USA
| | - Atsuo Fukuda
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka 431-3192, Japan.
- Advanced Research Facilities and Services, Preeminent Medical Photonics Education and Research Center, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka 431-3192, Japan
| | - Kristopher T Kahle
- Departments of Neurosurgery, Pediatrics, and Cellular and Molecular Physiology, Centers for Mendelian Genomics, Yale School of Medicine, New Haven, CT 06510, USA.
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21
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Codadu NK, Graham RT, Burman RJ, Jackson‐Taylor RT, Raimondo JV, Trevelyan AJ, Parrish RR. Divergent paths to seizure-like events. Physiol Rep 2019; 7:e14226. [PMID: 31587522 PMCID: PMC6778598 DOI: 10.14814/phy2.14226] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 07/29/2019] [Accepted: 07/31/2019] [Indexed: 12/19/2022] Open
Abstract
Much debate exists about how the brain transitions into an epileptic seizure. One source of confusion is that there are likely to be critical differences between experimental seizure models. To address this, we have compared the evolving activity patterns in two widely used in vitro models of epileptic discharges. Brain slices from young adult mice were prepared in the same way and bathed either in 0 Mg2+ or 100 µmol/L 4AP artificial cerebrospinal fluid. We have found that while local field potential recordings of epileptiform discharges in the two models appear broadly similar, patch-clamp analysis reveals an important difference in the relative degree of glutamatergic involvement. 4AP affects parvalbumin-expressing interneurons more than other cortical populations, destabilizing their resting state and inducing spontaneous bursting behavior. Consequently, the most prominent pattern of transient discharge ("interictal event") in this model is almost purely GABAergic, although the transition to seizure-like events (SLEs) involves pyramidal recruitment. In contrast, interictal discharges in 0 Mg2+ are only maintained by a very large glutamatergic component that also involves transient discharges of the interneurons. Seizure-like events in 0 Mg2+ have significantly higher power in the high gamma frequency band (60-120Hz) than these events do in 4AP, and are greatly delayed in onset by diazepam, unlike 4AP events. We, therefore, conclude that the 0 Mg2+ and 4AP models display fundamentally different levels of glutamatergic drive, demonstrating how ostensibly similar pathological discharges can arise from different sources. We contend that similar interpretative issues will also be relevant to clinical practice.
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Affiliation(s)
- Neela K. Codadu
- Institute of NeuroscienceMedical SchoolNewcastle UniversityNewcastle upon TyneUnited Kingdom
| | - Robert T. Graham
- Institute of NeuroscienceMedical SchoolNewcastle UniversityNewcastle upon TyneUnited Kingdom
| | - Richard J. Burman
- Division of Cell BiologyDepartment of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular MedicineFaculty of Health SciencesUniversity of Cape TownCape TownSouth Africa
| | | | - Joseph V. Raimondo
- Division of Cell BiologyDepartment of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular MedicineFaculty of Health SciencesUniversity of Cape TownCape TownSouth Africa
| | - Andrew J. Trevelyan
- Institute of NeuroscienceMedical SchoolNewcastle UniversityNewcastle upon TyneUnited Kingdom
| | - R. Ryley Parrish
- Institute of NeuroscienceMedical SchoolNewcastle UniversityNewcastle upon TyneUnited Kingdom
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22
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Diverse Actions of Astrocytes in GABAergic Signaling. Int J Mol Sci 2019; 20:ijms20122964. [PMID: 31216630 PMCID: PMC6628243 DOI: 10.3390/ijms20122964] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Revised: 06/10/2019] [Accepted: 06/14/2019] [Indexed: 01/06/2023] Open
Abstract
An imbalance of excitatory and inhibitory neurotransmission leading to over excitation plays a crucial role in generating seizures, while enhancing GABAergic mechanisms are critical in terminating seizures. In recent years, it has been reported in many studies that astrocytes are deeply involved in synaptic transmission. Astrocytes form a critical component of the “tripartite” synapses by wrapping around the pre- and post-synaptic elements. From this location, astrocytes are known to greatly influence the dynamics of ions and transmitters in the synaptic cleft. Despite recent extensive research on excitatory tripartite synapses, inhibitory tripartite synapses have received less attention, even though they influence inhibitory synaptic transmission by affecting chloride and GABA concentration dynamics. In this review, we will discuss the diverse actions of astrocytic chloride and GABA homeostasis at GABAergic tripartite synapses. We will then consider the pathophysiological impacts of disturbed GABA homeostasis at the tripartite synapse.
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23
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Fabera P, Parizkova M, Uttl L, Vondrakova K, Kubova H, Tsenov G, Mares P. Adenosine A1 Receptor Agonist 2-chloro-N6-cyclopentyladenosine and Hippocampal Excitability During Brain Development in Rats. Front Pharmacol 2019; 10:656. [PMID: 31258477 PMCID: PMC6587156 DOI: 10.3389/fphar.2019.00656] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2018] [Accepted: 05/20/2019] [Indexed: 01/10/2023] Open
Abstract
Objective: The adenosinergic system may influence excitability in the brain. Endogenous and exogenous adenosine has anticonvulsant activity presumably by activating A1 receptors. Adenosine A1 receptor agonist 2-chloro-N6-cyclopentyladenosine (CCPA) may thus bolster anticonvulsant effects, but its action and the number of A1 receptors at different developmental stages are not known. Methods: Hippocampal epileptic afterdischarges (ADs) were elicited in 12-, 15-, 18-, 25-, 45-, and 60-day-old rats. Stimulation and recording electrodes were implanted into the dorsal hippocampus. The A1 receptor agonist 2-chloro-N6-cyclopentyladenosine (CCPA, 0.5 or 1 mg/kg) was administered intraperitoneally 10 min before the first stimulation. Control animals were injected with saline. All rats were stimulated with a 2-s series of 1-ms biphasic pulses delivered at 60 Hz with increasing stepwise intensity (0.05–0.6 mA). Each age and dose group contained 9–14 animals. The AD thresholds and durations were evaluated, and the A1 receptors were detected in the hippocampus in 7-, 10-, 12-, 15-, 18-, 21-, 25-, 32-, and 52-day-old rats. Results: Both CCPA doses significantly increased hippocampal AD thresholds in 12-, 15-, 18-, and 60-day-old rats compared to controls. In contrast, the higher dose significantly decreased AD threshold in the 25-day-old rats. The AD durations were significantly shortened in all age groups except for 25-day-old rats where they were significantly prolonged. A1 receptor expression in the hippocampus was highest in 10-day-old rats and subsequently decreased. Significance: The adenosine A1 receptor agonist CCPA exhibited anticonvulsant activity at all developmental stages studied here except for 25-day-old rats. Age-related differences might be due to the development of presynaptic A1 receptors in the hippocampus.
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Affiliation(s)
- Petr Fabera
- Department of Developmental Epileptology, Institute of Physiology, Czech Academy of Sciences, Prague, Czechia.,Department of Neurology, Second Faculty of Medicine, Motol University Hospital, Charles University, Prague, Czechia
| | - Martina Parizkova
- Department of Developmental Epileptology, Institute of Physiology, Czech Academy of Sciences, Prague, Czechia.,Department of Neurology, Second Faculty of Medicine, Motol University Hospital, Charles University, Prague, Czechia
| | - Libor Uttl
- Department of Developmental Epileptology, Institute of Physiology, Czech Academy of Sciences, Prague, Czechia.,National Institute of Mental Health, Klecany, Czechia
| | - Katerina Vondrakova
- Department of Developmental Epileptology, Institute of Physiology, Czech Academy of Sciences, Prague, Czechia.,National Institute of Mental Health, Klecany, Czechia
| | - Hana Kubova
- Department of Developmental Epileptology, Institute of Physiology, Czech Academy of Sciences, Prague, Czechia
| | - Grygoriy Tsenov
- Department of Developmental Epileptology, Institute of Physiology, Czech Academy of Sciences, Prague, Czechia.,Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Pavel Mares
- Department of Developmental Epileptology, Institute of Physiology, Czech Academy of Sciences, Prague, Czechia
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24
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Rodríguez-Triviño CY, Torres Castro I, Dueñas Z. Hypochloremia in Patients with Severe Traumatic Brain Injury: A Possible Risk Factor for Increased Mortality. World Neurosurg 2019; 124:e783-e788. [PMID: 30682506 DOI: 10.1016/j.wneu.2019.01.025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 01/01/2019] [Accepted: 01/02/2019] [Indexed: 11/27/2022]
Abstract
OBJECTIVE To determine association between electrolyte disturbances and mortality in patients with severe traumatic brain injury. METHODS Medical records of patients with severe traumatic brain injury and Glasgow Coma Scale score <8 and electrolyte alterations were reviewed in a retrospective cohort study. Electrolyte levels were analyzed to establish an association between patients who died and patients who survived. Bivariate analysis was performed using χ2 test with a statistical reliability of 95% for categorical variables. Analysis for electrolyte changes to determine association with mortality was performed using χ2 test with multiple comparisons. Logistic regression was performed between the electrolyte alterations and their association with mortality. The reliability of statistical tests was 95%. RESULTS There was a significant relationship between hypochloremia and increased risk of mortality in 23.1% of deceased patients (P = 0.03). Furthermore, there was a significant correlation with age (P < 0.01) and with the Acute Physiology and Chronic Health Evaluation APACHE II (P < 0.01). CONCLUSIONS Hypochloremia could be an important prognostic factor to determine mortality risk and to improve treatment in patients with severe traumatic brain injury.
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Affiliation(s)
- Claudia Yaneth Rodríguez-Triviño
- Departamento de Ciencias Fisiológicas, Grupo Navarra Medicina, Facultad de Ciencias de la Salud, Fundación Universitaria Navarra-UNINAVARRA, Neiva, Huila, Colombia; Departamento de Ciencias Fisiológicas, Grupo de Neurobiología y Comportamiento, Facultad de Medicina, Universidad Nacional de Colombia, Sede Bogotá, Bogotá D.C., Colombia.
| | - Isidro Torres Castro
- Departamento de Ciencias Fisiológicas, Grupo Navarra Medicina, Facultad de Ciencias de la Salud, Fundación Universitaria Navarra-UNINAVARRA, Neiva, Huila, Colombia
| | - Zulma Dueñas
- Departamento de Ciencias Fisiológicas, Grupo de Neurobiología y Comportamiento, Facultad de Medicina, Universidad Nacional de Colombia, Sede Bogotá, Bogotá D.C., Colombia
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25
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Interactions between Membrane Resistance, GABA-A Receptor Properties, Bicarbonate Dynamics and Cl --Transport Shape Activity-Dependent Changes of Intracellular Cl - Concentration. Int J Mol Sci 2019; 20:ijms20061416. [PMID: 30897846 PMCID: PMC6471822 DOI: 10.3390/ijms20061416] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 03/15/2019] [Accepted: 03/18/2019] [Indexed: 11/17/2022] Open
Abstract
The effects of ionotropic γ-aminobutyric acid receptor (GABA-A, GABAA) activation depends critically on the Cl−-gradient across neuronal membranes. Previous studies demonstrated that the intracellular Cl−-concentration ([Cl−]i) is not stable but shows a considerable amount of activity-dependent plasticity. To characterize how membrane properties and different molecules that are directly or indirectly involved in GABAergic synaptic transmission affect GABA-induced [Cl−]i changes, we performed compartmental modeling in the NEURON environment. These simulations demonstrate that GABA-induced [Cl−]i changes decrease at higher membrane resistance, revealing a sigmoidal dependency between both parameters. Increase in GABAergic conductivity enhances [Cl−]i with a logarithmic dependency, while increasing the decay time of GABAA receptors leads to a nearly linear enhancement of the [Cl−]i changes. Implementing physiological levels of HCO3−-conductivity to GABAA receptors enhances the [Cl−]i changes over a wide range of [Cl−]i, but this effect depends on the stability of the HCO3− gradient and the intracellular pH. Finally, these simulations show that pure diffusional Cl−-elimination from dendrites is slow and that a high activity of Cl−-transport is required to improve the spatiotemporal restriction of GABA-induced [Cl−]i changes. In summary, these simulations revealed a complex interplay between several key factors that influence GABA-induced [Cl]i changes. The results suggest that some of these factors, including high resting [Cl−]i, high input resistance, slow decay time of GABAA receptors and dynamic HCO3− gradient, are specifically adapted in early postnatal neurons to facilitate limited activity-dependent [Cl−]i decreases.
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26
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Menzikov SA, Morozov SG. Involvement of brain GABA AR-coupled Cl -/HCO 3--ATPase in phenol-induced the head-twitching and tremor responses in rats. Neurotoxicology 2018; 71:122-131. [PMID: 30590068 DOI: 10.1016/j.neuro.2018.12.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 12/19/2018] [Accepted: 12/21/2018] [Indexed: 11/26/2022]
Abstract
Phenol-induced neurotoxicity manifests as twitching/tremor and convulsions, but its molecular mechanisms underlying the behavioral responses remain unclear. We assessed the role of the brain Cl-/HCO3--ATPase in behavioral responses in rats following an in vivo intraperitoneal injection of phenol (20-160 mg/kg). Low concentrations of phenol (20-80 mg/kg) increased the ATPase activity as well as the head twitching responses in rat, whereas higher phenol concentrations (>60 mg/kg) increased the tremor but reduced the ATPase activity. At phenol concentrations >120 mg/kg, no ATPase activity was detected. Phenobarbital (10 mg/kg) and picrotoxin (1 mg/kg) as well as o-vanadate (2 mg/kg), significantly prevented (˜55-70%) the phenol-induced change in the behavioral responses and completely restored the enzyme activity. In vitro experiments confirmed that phenol stimulated the Cl-/HCO3--ATPase activity at low concentrations, but had no stimulating effect on other transport ATPases. Low doses of phenol increased the formation of phosphoprotein and the rate of ATP-consuming Cl- transport by the reconstituted enzyme. The present findings provide evidence that phenol-induced neurotoxicity involves the Cl-/HCO3--ATPase in the behavioral responses in mammals and indicate the potential benefit of this enzyme as a target for the treatment of head twitching and other types of tremor diseases.
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Affiliation(s)
- Sergey A Menzikov
- Institute of General Pathology and Pathological Physiology, 8, Baltiyskaya st., Moscow, 125315, Russia.
| | - Sergey G Morozov
- Institute of General Pathology and Pathological Physiology, 8, Baltiyskaya st., Moscow, 125315, Russia
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27
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Wang Y, Wang Y, Chen Z. Double-edged GABAergic synaptic transmission in seizures: The importance of chloride plasticity. Brain Res 2018; 1701:126-136. [PMID: 30201259 DOI: 10.1016/j.brainres.2018.09.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 09/04/2018] [Accepted: 09/06/2018] [Indexed: 12/18/2022]
Abstract
GABAergic synaptic inhibition, which is a critical regulator of neuronal excitability, is closely involved in epilepsy. Interestingly, fast GABAergic transmission mediated by Cl- permeable GABAA receptors can bi-directionally exert both seizure-suppressing and seizure-promoting actions. Accumulating evidence suggests that chloride plasticity, the driving force of GABAA receptor-mediated synaptic transmission, contributes to the double-edged role of GABAergic synapses in seizures. Large amounts of Cl- influx can overwhelm Cl- extrusion during seizures not only in healthy tissue in a short-term "activity-dependent" manner, but also in chronic epilepsy in a long-term, irreversible "pathology-dependent" manner related to the dysfunction of two chloride transporters: the chloride importer NKCC1 and the chloride exporter KCC2. In this review, we address the importance of chloride plasticity for the "activity-dependent" and "pathology-dependent" mechanisms underlying epileptic events and provide possible directions for further research, which may be clinically important for the design of GABAergic synapse-targeted precise therapeutic interventions for epilepsy.
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Affiliation(s)
- Ying Wang
- Institute of Pharmacology & Toxicology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Yi Wang
- Institute of Pharmacology & Toxicology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Zhong Chen
- Institute of Pharmacology & Toxicology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China; Epilepsy Center, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China.
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28
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Lombardi A, Jedlicka P, Luhmann HJ, Kilb W. Giant Depolarizing Potentials Trigger Transient Changes in the Intracellular Cl - Concentration in CA3 Pyramidal Neurons of the Immature Mouse Hippocampus. Front Cell Neurosci 2018; 12:420. [PMID: 30515078 PMCID: PMC6255825 DOI: 10.3389/fncel.2018.00420] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 10/26/2018] [Indexed: 11/30/2022] Open
Abstract
Giant depolarizing potentials (GDPs) represent a typical spontaneous activity pattern in the immature hippocampus. GDPs are mediated by GABAergic and glutamatergic synaptic inputs and their initiation requires an excitatory GABAergic action, which is typical for immature neurons due to their elevated intracellular Cl- concentration ([Cl-]i). Because GABAA receptors are ligand-gated Cl- channels, activation of these receptors can potentially influence [Cl-]i. However, whether the GABAergic activity during GDPs influences [Cl-]i is unclear. To address this question we performed whole-cell and gramicidin-perforated patch-clamp recordings from visually identified CA3 pyramidal neurons in immature hippocampal slices of mice at postnatal days 4–7. These experiments revealed that the [Cl-]i of CA3 neurons displays a considerable heterogeneity, ranging from 13 to 70 mM (average 38.1 ± 3.2 mM, n = 36). In accordance with this diverse [Cl-]i, GDPs induced either Cl--effluxes or Cl--influxes. In high [Cl-]i neurons with a negative Cl--driving force (DFCl) the [Cl-]i decreased after a GDP by 12.4 ± 3.4 mM (n = 10), while in low [Cl-]i neurons with a positive DFCl [Cl-]i increased by 4.4 ± 0.9 mM (n = 6). Inhibition of GDP activity by application of the AMPA receptor antagonist CNQX led to a [Cl-]i decrease to 24.7 ± 2.9 mM (n = 8). We conclude from these results, that Cl--fluxes via GABAA receptors during GDPs induced substantial [Cl-]i changes and that this activity-dependent ionic plasticity in neuronal [Cl-]i contributes to the functional consequences of GABAergic responses, emphasizing the concept that [Cl-]i is a state- and compartment-dependent parameter of individual cells.
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Affiliation(s)
- Aniello Lombardi
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Peter Jedlicka
- Interdisciplinary Centre for 3Rs in Animal Research, Faculty of Medicine, Justus Liebig University Giessen, Giessen, Germany.,Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, Frankfurt, Germany
| | - Heiko J Luhmann
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Werner Kilb
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University Mainz, Mainz, Germany
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29
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Menzikov S. Dual character of GABA action on Cl --transport by the reconstituted Cl -/[Formula: see text]-ATPase from rat brain. J Recept Signal Transduct Res 2018; 38:307-310. [PMID: 30259773 DOI: 10.1080/10799893.2018.1494741] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
The Cl-/[Formula: see text]-ATPase from the plasma membranes of animal brains is an ATP-consuming Cl--transporting ATPase P-type that is structurally coupled to GABAA receptors. The aim of work was to study the GABA effect on Cl- transport across liposomal membranes by the reconstituted ATPase under various conditions (i.e. in the absence and in the presence of ATP in the incubation medium). We reconstituted the affinity-purified enzyme in the liposomes with a fluorescent dye for Cl-. The Cl--transport in proteoliposomes was evaluated from variations in fluorescence. Native-PAGE of the purified enzyme preparation, as well as western blot analysis with an antibody against the GABAAR β3 subunit, showed one band with a molecular mass of 300 kDa. The addition of GABA (100 μM) quickly resulted (1-3 s) in an increase in the Cl- influx into proteoliposomes. The application of ATP (3 mM) resulted in a gradual increase in the Cl- inflow into the proteoliposomes at 0.5-4 min. Vanadate (10 μM) did not change the GABA-induced Cl- inflow into the liposomes, but completely inhibited the ATP-dependent Cl- input. Under conditions where Cl- was previously loaded into proteoliposomes by ATP-dependent Cl- input, the addition of GABA to the incubation medium caused a short-lasting Cl- efflux from the proteoliposomes. However, an additional long-time incubation of these proteoliposomes resulted in the restoration of Cl- accumulation. Pentobarbital, propofol, or diazepam elevate and picrotoxin or furosemide eliminate the effect of GABA on the Cl--transport processes. These findings indicate a dual nature of GABA action on the Cl-/[Formula: see text]-ATPase.
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Affiliation(s)
- Sergey Menzikov
- a Institute of General Pathology and Pathological Physiology , Moscow , Russia
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30
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Menzikov S. Biochemical properties of the sensitivity to GABA Aergic ligands, Cl -/HCO 3--ATPase isolated from fish (Cyprinus carpio) olfactory mucosa and brain. FISH PHYSIOLOGY AND BIOCHEMISTRY 2018; 44:583-597. [PMID: 29218440 DOI: 10.1007/s10695-017-0455-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 11/30/2017] [Indexed: 06/07/2023]
Abstract
This paper presents a comparative study of the roles of Cl- and HCO3- in the functioning of the GABAAR-associated Cl-/HCO3--ATPase of the plasma membranes of the olfactory sensory neurons (OSNs) and mature brain neurons (MBNs) of fish. The ATPase activity of OSNs and its dephosphorylation were increased twofold by Cl-(15-30 mmol l-1), whereas the enzyme from MBNs was not significantly affected by Cl-. By contrast, HCO3-(15-30 mmol l-1) significantly activated the MBN enzyme and its dephosphorylation, but had no effect on the OSN ATPase. The maximum ATPase activity and protein dephosphorylation was observed in the presence of both Cl-(15 mmol l-1)/HCO3-(27 mmol l-1) and these activities were inhibited in the presence of picrotoxin (100 μmol l-1), bumetanide (150 μmol l-1), and DIDS (1000 μmol l-1). SDS-PAGE revealed that ATPases purified from the neuronal membrane have a subunit with molecular mass of ~ 56 kDa that binds [3H]muscimol and [3H]flunitrazepam. Direct phosphorylation of the enzymes in the presence of ATP-γ-32P and Mg2+, as well as Cl-/HCO3- sensitive dephosphorylation, is also associated with this 56 kDa peptide. Both preparations also showed one subunit with molecular mass 56 kDa that was immunoreactive with GABAAR β3 subunit. The use of a fluorescent dye for Cl- demonstrated that HCO3-(27 mmol l-1) causes a twofold increase in Cl- influx into proteoliposomes containing reconstituted ATPases from MBNs, but HCO3- had no effect on the reconstituted enzyme from OSNs. These data are the first to demonstrate a differential effect of Cl- and HCO3- in the regulation of the Cl-/HCO3--ATPases functioning in neurons with different specializations.
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Affiliation(s)
- Sergey Menzikov
- Department Russian Academy of Science, Institute of General Pathology and Pathophysiology, 8, Baltiyskaya st., Moscow, Russia, 125315.
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31
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M De la Fuente I, Malaina I, Pérez-Samartín A, Boyano MD, Pérez-Yarza G, Bringas C, Villarroel Á, Fedetz M, Arellano R, Cortes JM, Martínez L. Dynamic properties of calcium-activated chloride currents in Xenopus laevis oocytes. Sci Rep 2017; 7:41791. [PMID: 28198817 PMCID: PMC5304176 DOI: 10.1038/srep41791] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 12/30/2016] [Indexed: 11/18/2022] Open
Abstract
Chloride is the most abundant permeable anion in the cell, and numerous studies in the last two decades highlight the great importance and broad physiological role of chloride currents mediated anion transport. They participate in a multiplicity of key processes, as for instance, the regulation of electrical excitability, apoptosis, cell cycle, epithelial secretion and neuronal excitability. In addition, dysfunction of Cl− channels is involved in a variety of human diseases such as epilepsy, osteoporosis and different cancer types. Historically, chloride channels have been of less interest than the cation channels. In fact, there seems to be practically no quantitative studies of the dynamics of chloride currents. Here, for the first time, we have quantitatively studied experimental calcium-activated chloride fluxes belonging to Xenopus laevis oocytes, and the main results show that the experimental Cl− currents present an informational structure characterized by highly organized data sequences, long-term memory properties and inherent “crossover” dynamics in which persistent correlations arise at short time intervals, while anti-persistent behaviors become dominant in long time intervals. Our work sheds some light on the understanding of the informational properties of ion currents, a key element to elucidate the physiological functional coupling with the integrative dynamics of metabolic processes.
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Affiliation(s)
- Ildefonso M De la Fuente
- Department of Nutrition, CEBAS-CSIC Institute, Espinardo University Campus, Murcia, Spain.,Department of Mathematics, Faculty of Science and Technology, University of the Basque Country, UPV/EHU, Leioa, Spain
| | - Iker Malaina
- Department of Mathematics, Faculty of Science and Technology, University of the Basque Country, UPV/EHU, Leioa, Spain
| | - Alberto Pérez-Samartín
- Department of Neurosciences, Faculty of Medicine and Dentistry, University of the Basque Country, UPV/EHU, Leioa, Spain
| | - María Dolores Boyano
- Department of Cell Biology and Histology, Faculty of Medicine and Dentistry, University of the Basque Country, UPV/EHU, Leioa, Spain
| | - Gorka Pérez-Yarza
- Department of Cell Biology and Histology, Faculty of Medicine and Dentistry, University of the Basque Country, UPV/EHU, Leioa, Spain
| | - Carlos Bringas
- Department of Cell Biology and Histology, Faculty of Medicine and Dentistry, University of the Basque Country, UPV/EHU, Leioa, Spain
| | - Álvaro Villarroel
- Biophysics Unit, CSIC, University of the Basque Country, UPV/EHU, Leioa, Spain
| | - María Fedetz
- Department of Biochemistry and Pharmacology, Institute of Parasitology and Biomedicine "López-Neyra", CSIC, Granada, Spain
| | - Rogelio Arellano
- Laboratory of Cellular Neurophysiology, Neurobiology Institute, UNAM, Querétaro, México
| | - Jesus M Cortes
- Department of Cell Biology and Histology, Faculty of Medicine and Dentistry, University of the Basque Country, UPV/EHU, Leioa, Spain.,BioCruces Health Research Institute, Cruces University Hospital, Barakaldo, Spain.,IKERBASQUE: The Basque Foundation for Science, Bilbao, Spain
| | - Luis Martínez
- Department of Mathematics, Faculty of Science and Technology, University of the Basque Country, UPV/EHU, Leioa, Spain
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Raimondo JV, Richards BA, Woodin MA. Neuronal chloride and excitability - the big impact of small changes. Curr Opin Neurobiol 2016; 43:35-42. [PMID: 27992777 DOI: 10.1016/j.conb.2016.11.012] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 10/19/2016] [Accepted: 11/09/2016] [Indexed: 12/18/2022]
Abstract
Synaptic inhibition is a critical regulator of neuronal excitability, and in the mature brain the majority of synaptic inhibition is mediated by Cl--permeable GABAA receptors. Unlike other physiologically relevant ions, Cl- is dynamically regulated, and alterations in the Cl- gradient can have significant impact on neuronal excitability. Due to changes in the neuronal Cl- concentration, GABAergic transmission can bidirectionally regulate the induction of excitatory synaptic plasticity and gate the closing of the critical period for monocular deprivation in visual cortex. GABAergic circuitry can also provide a powerful restraining mechanism for the spread of excitation, however Cl- extrusion mechanisms can become overwhelmed and GABA can paradoxically contribute to pathological excitation such as the propagation of seizure activity.
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Affiliation(s)
- Joseph V Raimondo
- Division of Physiology, Department of Human Biology and Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Anzio Road Observatory, 7925 Cape Town, South Africa
| | - Blake A Richards
- Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada; Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario M5S 3G5, Canada
| | - Melanie A Woodin
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario M5S 3G5, Canada.
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Buchin A, Chizhov A, Huberfeld G, Miles R, Gutkin BS. Reduced Efficacy of the KCC2 Cotransporter Promotes Epileptic Oscillations in a Subiculum Network Model. J Neurosci 2016; 36:11619-11633. [PMID: 27852771 PMCID: PMC6231544 DOI: 10.1523/jneurosci.4228-15.2016] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 08/04/2016] [Accepted: 08/07/2016] [Indexed: 12/17/2022] Open
Abstract
Pharmacoresistant epilepsy is a chronic neurological condition in which a basal brain hyperexcitability results in paroxysmal hypersynchronous neuronal discharges. Human temporal lobe epilepsy has been associated with dysfunction or loss of the potassium-chloride cotransporter KCC2 in a subset of pyramidal cells in the subiculum, a key structure generating epileptic activities. KCC2 regulates intraneuronal chloride and extracellular potassium levels by extruding both ions. Absence of effective KCC2 may alter the dynamics of chloride and potassium levels during repeated activation of GABAergic synapses due to interneuron activity. In turn, such GABAergic stress may itself affect Cl- regulation. Such changes in ionic homeostasis may switch GABAergic signaling from inhibitory to excitatory in affected pyramidal cells and also increase neuronal excitability. Possibly these changes contribute to periodic bursting in pyramidal cells, an essential component in the onset of ictal epileptic events. We tested this hypothesis with a computational model of a subicular network with realistic connectivity. The pyramidal cell model explicitly incorporated the cotransporter KCC2 and its effects on the internal/external chloride and potassium levels. Our network model suggested the loss of KCC2 in a critical number of pyramidal cells increased external potassium and intracellular chloride concentrations leading to seizure-like field potential oscillations. These oscillations included transient discharges leading to ictal-like field events with frequency spectra as in vitro Restoration of KCC2 function suppressed seizure activity and thus may present a useful therapeutic option. These simulations therefore suggest that reduced KCC2 cotransporter activity alone may underlie the generation of ictal discharges. SIGNIFICANCE STATEMENT Ion regulation in the brain is a major determinant of neural excitability. Intracellular chloride in neurons, a partial determinant of the resting potential and the inhibitory reversal potentials, is regulated together with extracellular potassium via kation chloride cotransporters. During temporal lobe epilepsy, the homeostatic regulation of intracellular chloride is impaired in pyramidal cells, yet how this dysregulation may lead to seizures has not been explored. Using a realistic neural network model describing ion mechanisms, we show that chloride homeostasis pathology provokes seizure activity analogous to recordings from epileptogenic brain tissue. We show that there is a critical percentage of pathological cells required for seizure initiation. Our model predicts that restoration of the chloride homeostasis in pyramidal cells could be a viable antiepileptic strategy.
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Affiliation(s)
- Anatoly Buchin
- École normale supérieure, Paris Sciences et Lettres University, Laboratoire de Neurosciences Cognitives, Institute national de la santé et de la recherche médicale U960, Group for Neural Theory, 75005 Paris, France,
- Peter the Great St. Petersburg Polytechnic University, St. Petersburg 195251, Russia
- National Research University Higher School of Economics, Center for Cognition and Decision Making, Moscow 109316, Russia
| | - Anton Chizhov
- Ioffe Institute, Computational Physics Laboratory, St. Petersburg 194021, Russia
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg 194223, Russia
| | - Gilles Huberfeld
- Université Pierre et Marie Curie, Pitié-Salpêtrière Hôpital, Assistance Publique-Hôpitaux de Paris, Neurophysiology Department, 75013 Paris, France
- Institute national de la santé et de la recherche médicale U1129 "Infantile Epilepsies and Brain Plasticity," Paris Descartes University, Pôle de recherche et d'enseignement supérieur Sorbonne Paris Cité, 75015 Paris, France, and
| | - Richard Miles
- Institut du Cerveau et de la Moelle Epinière, Cortex et Epilepsie Group, 75013 Paris, France
| | - Boris S Gutkin
- École normale supérieure, Paris Sciences et Lettres University, Laboratoire de Neurosciences Cognitives, Institute national de la santé et de la recherche médicale U960, Group for Neural Theory, 75005 Paris, France
- National Research University Higher School of Economics, Center for Cognition and Decision Making, Moscow 109316, Russia
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Knoflach F, Hernandez MC, Bertrand D. GABAA receptor-mediated neurotransmission: Not so simple after all. Biochem Pharmacol 2016; 115:10-7. [DOI: 10.1016/j.bcp.2016.03.014] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 03/17/2016] [Indexed: 12/28/2022]
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Zhang W, Schmelzeisen S, Parthier D, Frings S, Möhrlen F. Anoctamin Calcium-Activated Chloride Channels May Modulate Inhibitory Transmission in the Cerebellar Cortex. PLoS One 2015; 10:e0142160. [PMID: 26558388 PMCID: PMC4641602 DOI: 10.1371/journal.pone.0142160] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 10/19/2015] [Indexed: 01/18/2023] Open
Abstract
Calcium-activated chloride channels of the anoctamin (alias TMEM16) protein family fulfill critical functions in epithelial fluid transport, smooth muscle contraction and sensory signal processing. Little is known, however, about their contribution to information processing in the central nervous system. Here we examined the recent finding that a calcium-dependent chloride conductance impacts on GABAergic synaptic inhibition in Purkinje cells of the cerebellum. We asked whether anoctamin channels may underlie this chloride conductance. We identified two anoctamin channel proteins, ANO1 and ANO2, in the cerebellar cortex. ANO1 was expressed in inhibitory interneurons of the molecular layer and the granule cell layer. Both channels were expressed in Purkinje cells but, while ANO1 appeared to be retained in the cell body, ANO2 was targeted to the dendritic tree. Functional studies confirmed that ANO2 was involved in a calcium-dependent mode of ionic plasticity that reduces the efficacy of GABAergic synapses. ANO2 channels attenuated GABAergic transmission by increasing the postsynaptic chloride concentration, hence reducing the driving force for chloride influx. Our data suggest that ANO2 channels are involved in a Ca2+-dependent regulation of synaptic weight in GABAergic inhibition. Thus, in balance with the chloride extrusion mechanism via the co-transporter KCC2, ANO2 appears to regulate ionic plasticity in the cerebellum.
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Affiliation(s)
- Weiping Zhang
- Department of Animal Molecular Physiology, Centre of Organismal Studies, Im Neuenheimer Feld 504, Heidelberg University, Heidelberg, Germany
| | - Steffen Schmelzeisen
- Department of Animal Molecular Physiology, Centre of Organismal Studies, Im Neuenheimer Feld 504, Heidelberg University, Heidelberg, Germany
| | - Daniel Parthier
- Department of Animal Molecular Physiology, Centre of Organismal Studies, Im Neuenheimer Feld 504, Heidelberg University, Heidelberg, Germany
| | - Stephan Frings
- Department of Animal Molecular Physiology, Centre of Organismal Studies, Im Neuenheimer Feld 504, Heidelberg University, Heidelberg, Germany
| | - Frank Möhrlen
- Department of Animal Molecular Physiology, Centre of Organismal Studies, Im Neuenheimer Feld 504, Heidelberg University, Heidelberg, Germany
- * E-mail:
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Raimondo JV, Burman RJ, Katz AA, Akerman CJ. Ion dynamics during seizures. Front Cell Neurosci 2015; 9:419. [PMID: 26539081 PMCID: PMC4612498 DOI: 10.3389/fncel.2015.00419] [Citation(s) in RCA: 101] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Accepted: 10/04/2015] [Indexed: 12/14/2022] Open
Abstract
Changes in membrane voltage brought about by ion fluxes through voltage and transmitter-gated channels represent the basis of neural activity. As such, electrochemical gradients across the membrane determine the direction and driving force for the flow of ions and are therefore crucial in setting the properties of synaptic transmission and signal propagation. Ion concentration gradients are established by a variety of mechanisms, including specialized transporter proteins. However, transmembrane gradients can be affected by ionic fluxes through channels during periods of elevated neural activity, which in turn are predicted to influence the properties of on-going synaptic transmission. Such activity-induced changes to ion concentration gradients are a feature of both physiological and pathological neural processes. An epileptic seizure is an example of severely perturbed neural activity, which is accompanied by pronounced changes in intracellular and extracellular ion concentrations. Appreciating the factors that contribute to these ion dynamics is critical if we are to understand how a seizure event evolves and is sustained and terminated by neural tissue. Indeed, this issue is of significant clinical importance as status epilepticus—a type of seizure that does not stop of its own accord—is a life-threatening medical emergency. In this review we explore how the transmembrane concentration gradient of the six major ions (K+, Na+, Cl−, Ca2+, H+and HCO3−) is altered during an epileptic seizure. We will first examine each ion individually, before describing how multiple interacting mechanisms between ions might contribute to concentration changes and whether these act to prolong or terminate epileptic activity. In doing so, we will consider how the availability of experimental techniques has both advanced and restricted our ability to study these phenomena.
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Affiliation(s)
- Joseph V Raimondo
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town Cape Town, South Africa ; UCT/MRC Receptor Biology Unit, Department of Integrative Biomedical Sciences and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town Cape Town, South Africa
| | - Richard J Burman
- UCT/MRC Receptor Biology Unit, Department of Integrative Biomedical Sciences and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town Cape Town, South Africa
| | - Arieh A Katz
- UCT/MRC Receptor Biology Unit, Department of Integrative Biomedical Sciences and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town Cape Town, South Africa
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Saitsu H, Akita T, Tohyama J, Goldberg-Stern H, Kobayashi Y, Cohen R, Kato M, Ohba C, Miyatake S, Tsurusaki Y, Nakashima M, Miyake N, Fukuda A, Matsumoto N. De novo KCNB1 mutations in infantile epilepsy inhibit repetitive neuronal firing. Sci Rep 2015; 5:15199. [PMID: 26477325 PMCID: PMC4609934 DOI: 10.1038/srep15199] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 09/21/2015] [Indexed: 11/09/2022] Open
Abstract
The voltage-gated Kv2.1 potassium channel encoded by KCNB1 produces the major delayed rectifier potassium current in pyramidal neurons. Recently, de novo heterozygous missense KCNB1 mutations have been identified in three patients with epileptic encephalopathy and a patient with neurodevelopmental disorder. However, the frequency of KCNB1 mutations in infantile epileptic patients and their effects on neuronal activity are yet unknown. We searched whole exome sequencing data of a total of 437 patients with infantile epilepsy, and found novel de novo heterozygous missense KCNB1 mutations in two patients showing psychomotor developmental delay and severe infantile generalized seizures with high-amplitude spike-and-wave electroencephalogram discharges. The mutation located in the channel voltage sensor (p.R306C) disrupted sensitivity and cooperativity of the sensor, while the mutation in the channel pore domain (p.G401R) selectively abolished endogenous Kv2 currents in transfected pyramidal neurons, indicating a dominant-negative effect. Both mutants inhibited repetitive neuronal firing through preventing production of deep interspike voltages. Thus KCNB1 mutations can be a rare genetic cause of infantile epilepsy, and insufficient firing of pyramidal neurons would disturb both development and stability of neuronal circuits, leading to the disease phenotypes.
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Affiliation(s)
- Hirotomo Saitsu
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Tenpei Akita
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Jun Tohyama
- Department of Pediatrics, Epilepsy Center, Nishi-Niigata Chuo National Hospital, Niigata, Japan
| | | | - Yu Kobayashi
- Department of Pediatrics, Epilepsy Center, Nishi-Niigata Chuo National Hospital, Niigata, Japan
| | - Roni Cohen
- Epilepsy Center, Schneider's Children Medical Center, Petah Tiqwa, Israel
| | - Mitsuhiro Kato
- Department of Pediatrics, Yamagata University Faculty of Medicine, Yamagata, Japan
| | - Chihiro Ohba
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Satoko Miyatake
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Yoshinori Tsurusaki
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Mitsuko Nakashima
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Noriko Miyake
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Atsuo Fukuda
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Naomichi Matsumoto
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
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Javdani F, Holló K, Hegedűs K, Kis G, Hegyi Z, Dócs K, Kasugai Y, Fukazawa Y, Shigemoto R, Antal M. Differential expression patterns of K(+) /Cl(-) cotransporter 2 in neurons within the superficial spinal dorsal horn of rats. J Comp Neurol 2015; 523:1967-83. [PMID: 25764511 DOI: 10.1002/cne.23774] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 03/03/2015] [Accepted: 03/03/2015] [Indexed: 01/21/2023]
Abstract
γ-Aminobutyric acid (GABA)- and glycine-mediated hyperpolarizing inhibition is associated with a chloride influx that depends on the inwardly directed chloride electrochemical gradient. In neurons, the extrusion of chloride from the cytosol primarily depends on the expression of an isoform of potassium-chloride cotransporters (KCC2s). KCC2 is crucial in the regulation of the inhibitory tone of neural circuits, including pain processing neural assemblies. Thus we investigated the cellular distribution of KCC2 in neurons underlying pain processing in the superficial spinal dorsal horn of rats by using high-resolution immunocytochemical methods. We demonstrated that perikarya and dendrites widely expressed KCC2, but axon terminals proved to be negative for KCC2. In single ultrathin sections, silver deposits labeling KCC2 molecules showed different densities on the surface of dendritic profiles, some of which were negative for KCC2. In freeze fracture replicas and tissue sections double stained for the β3-subunit of GABAA receptors and KCC2, GABAA receptors were revealed on dendritic segments with high and also with low KCC2 densities. By measuring the distances between spots immunoreactive for gephyrin (a scaffolding protein of GABAA and glycine receptors) and KCC2 on the surface of neurokinin 1 (NK1) receptor-immunoreactive dendrites, we found that gephyrin-immunoreactive spots were located at various distances from KCC2 cotransporters; 5.7 % of them were recovered in the middle of 4-10-µm-long dendritic segments that were free of KCC2 immunostaining. The variable local densities of KCC2 may result in variable postsynaptic potentials evoked by the activation of GABAA and glycine receptors along the dendrites of spinal neurons.
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Affiliation(s)
- Fariba Javdani
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen 4012, Hungary
| | - Krisztina Holló
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen 4012, Hungary
| | - Krisztina Hegedűs
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen 4012, Hungary
| | - Gréta Kis
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen 4012, Hungary
| | - Zoltán Hegyi
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen 4012, Hungary
| | - Klaudia Dócs
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen 4012, Hungary
| | - Yu Kasugai
- Department of Pharmacology, Innsbruck Medical University, Innsbruck 6020, Austria
| | - Yugo Fukazawa
- Division of Cell Biology and Neuroscience, Faculty of Medical Sciences, University of Fukui, Yoshida, 910-1193, Japan
| | - Ryuichi Shigemoto
- Institute of Science and Technology Austria, Klosterneuburg, 3400, Austria
| | - Miklós Antal
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen 4012, Hungary
- MTA-DE Neuroscience Research Group, Debrecen, 4012, Hungary
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Abstract
Altered inhibitory function is an important facet of epileptic pathology. A key concept is that GABAergic activity can become excitatory if intraneuronal chloride rises. However, it has proved difficult to separate the role of raised chloride from other contributory factors in complex network phenomena, such as epileptic pathology. Therefore, we asked what patterns of activity are associated with chloride dysregulation by making novel use of Halorhodopsin to load clusters of mouse pyramidal cells artificially with Cl(-). Brief (1-10 s) activation of Halorhodopsin caused substantial positive shifts in the GABAergic reversal potential that were proportional to the charge transfer during the illumination and in adult neocortical pyramidal neurons decayed with a time constant of τ = 8.0 ± 2.8s. At the network level, these positive shifts in EGABA produced a transient rise in network excitability, with many distinctive features of epileptic foci, including high-frequency oscillations with evidence of out-of-phase firing (Ibarz et al., 2010). We show how such firing patterns can arise from quite small shifts in the mean intracellular Cl(-) level, within heterogeneous neuronal populations. Notably, however, chloride loading by itself did not trigger full ictal events, even with additional electrical stimulation to the underlying white matter. In contrast, when performed in combination with low, subepileptic levels of 4-aminopyridine, Halorhodopsin activation rapidly induced full ictal activity. These results suggest that chloride loading has at most an adjunctive role in ictogenesis. Our simulations also show how chloride loading can affect the jitter of action potential timing associated with imminent recruitment to an ictal event (Netoff and Schiff, 2002).
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Signaling between periglomerular cells reveals a bimodal role for GABA in modulating glomerular microcircuitry in the olfactory bulb. Proc Natl Acad Sci U S A 2015; 112:9478-83. [PMID: 26170298 DOI: 10.1073/pnas.1424406112] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In the mouse olfactory bulb glomerulus, the GABAergic periglomerular (PG) cells provide a major inhibitory drive within the microcircuit. Here we examine GABAergic synapses between these interneurons. At these synapses, GABA is depolarizing and exerts a bimodal control on excitability. In quiescent cells, activation of GABAA receptors can induce the cells to fire, thereby providing a means for amplification of GABA release in the glomerular microcircuit via GABA-induced GABA release. In contrast, GABA is inhibitory in neurons that are induced to fire tonically. PG-PG interactions are modulated by nicotinic acetylcholine receptors (nAChRs), and our data suggest that changes in intracellular calcium concentrations triggered by nAChR activation can be amplified by GABA release. Our results suggest that bidirectional control of inhibition in PG neurons can allow for modulatory inputs, like the cholinergic inputs from the basal forebrain, to determine threshold set points for filtering out weak olfactory inputs in the glomerular layer of the olfactory bulb via the activation of nAChRs.
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Excitatory effects of parvalbumin-expressing interneurons maintain hippocampal epileptiform activity via synchronous afterdischarges. J Neurosci 2015; 34:15208-22. [PMID: 25392490 DOI: 10.1523/jneurosci.1747-14.2014] [Citation(s) in RCA: 126] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Epileptic seizures are characterized by periods of hypersynchronous, hyperexcitability within brain networks. Most seizures involve two stages: an initial tonic phase, followed by a longer clonic phase that is characterized by rhythmic bouts of synchronized network activity called afterdischarges (ADs). Here we investigate the cellular and network mechanisms underlying hippocampal ADs in an effort to understand how they maintain seizure activity. Using in vitro hippocampal slice models from rats and mice, we performed electrophysiological recordings from CA3 pyramidal neurons to monitor network activity and changes in GABAergic signaling during epileptiform activity. First, we show that the highest synchrony occurs during clonic ADs, consistent with the idea that specific circuit dynamics underlie this phase of the epileptiform activity. We then show that ADs require intact GABAergic synaptic transmission, which becomes excitatory as a result of a transient collapse in the chloride (Cl(-)) reversal potential. The depolarizing effects of GABA are strongest at the soma of pyramidal neurons, which implicates somatic-targeting interneurons in AD activity. To test this, we used optogenetic techniques to selectively control the activity of somatic-targeting parvalbumin-expressing (PV(+)) interneurons. Channelrhodopsin-2-mediated activation of PV(+) interneurons during the clonic phase generated excitatory GABAergic responses in pyramidal neurons, which were sufficient to elicit and entrain synchronous AD activity across the network. Finally, archaerhodopsin-mediated selective silencing of PV(+) interneurons reduced the occurrence of ADs during the clonic phase. Therefore, we propose that activity-dependent Cl(-) accumulation subverts the actions of PV(+) interneurons to perpetuate rather than terminate pathological network hyperexcitability during the clonic phase of seizures.
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Arosio D, Ratto GM. Twenty years of fluorescence imaging of intracellular chloride. Front Cell Neurosci 2014; 8:258. [PMID: 25221475 PMCID: PMC4148895 DOI: 10.3389/fncel.2014.00258] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Accepted: 08/12/2014] [Indexed: 11/23/2022] Open
Abstract
Chloride homeostasis has a pivotal role in controlling neuronal excitability in the adult brain and during development. The intracellular concentration of chloride is regulated by the dynamic equilibrium between passive fluxes through membrane conductances and the active transport mediated by importers and exporters. In cortical neurons, chloride fluxes are coupled to network activity by the opening of the ionotropic GABAA receptors that provides a direct link between the activity of interneurons and chloride fluxes. These molecular mechanisms are not evenly distributed and regulated over the neuron surface and this fact can lead to a compartmentalized control of the intracellular concentration of chloride. The inhibitory drive provided by the activity of the GABAA receptors depends on the direction and strength of the associated currents, which are ultimately dictated by the gradient of chloride, the main charge carrier flowing through the GABAA channel. Thus, the intracellular distribution of chloride determines the local strength of ionotropic inhibition and influences the interaction between converging excitation and inhibition. The importance of chloride regulation is also underlined by its involvement in several brain pathologies, including epilepsy and disorders of the autistic spectra. The full comprehension of the physiological meaning of GABAergic activity on neurons requires the measurement of the spatiotemporal dynamics of chloride fluxes across the membrane. Nowadays, there are several available tools for the task, and both synthetic and genetically encoded indicators have been successfully used for chloride imaging. Here, we will review the available sensors analyzing their properties and outlining desirable future developments.
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Affiliation(s)
- Daniele Arosio
- Institute of Biophysics, National Research Council and Bruno Kessler Foundation Trento, Italy ; Centre for Integrative Biology, University of Trento Trento, Italy
| | - Gian Michele Ratto
- Nanoscience Institute, National Research Council of Italy Pisa, Italy ; NEST, Scuola Normale Superiore Pisa, Italy
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Raimondo JV, Joyce B, Kay L, Schlagheck T, Newey SE, Srinivas S, Akerman CJ. A genetically-encoded chloride and pH sensor for dissociating ion dynamics in the nervous system. Front Cell Neurosci 2013; 7:202. [PMID: 24312004 PMCID: PMC3826072 DOI: 10.3389/fncel.2013.00202] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Accepted: 10/17/2013] [Indexed: 01/08/2023] Open
Abstract
Within the nervous system, intracellular Cl− and pH regulate fundamental processes including cell proliferation, metabolism, synaptic transmission, and network excitability. Cl− and pH are often co-regulated, and network activity results in the movement of both Cl− and H+. Tools to accurately measure these ions are crucial for understanding their role under physiological and pathological conditions. Although genetically-encoded Cl− and pH sensors have been described previously, these either lack ion specificity or are unsuitable for neuronal use. Here we present ClopHensorN—a new genetically-encoded ratiometric Cl− and pH sensor that is optimized for the nervous system. We demonstrate the ability of ClopHensorN to dissociate and simultaneously quantify Cl− and H+ concentrations under a variety of conditions. In addition, we establish the sensor's utility by characterizing activity-dependent ion dynamics in hippocampal neurons.
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Affiliation(s)
- Joseph V Raimondo
- Department of Pharmacology, University of Oxford Oxford, UK ; UCT/MRC Receptor Biology Unit, Division of Medical Biochemistry, Faculty of Health Sciences, Institute of Infectious Disease and Molecular Medicine, University of Cape Town Cape Town, South Africa
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Smith SS. The influence of stress at puberty on mood and learning: role of the α4βδ GABAA receptor. Neuroscience 2013; 249:192-213. [PMID: 23079628 PMCID: PMC3586385 DOI: 10.1016/j.neuroscience.2012.09.065] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Revised: 09/21/2012] [Accepted: 09/25/2012] [Indexed: 11/22/2022]
Abstract
It is well-known that the onset of puberty is associated with changes in mood as well as cognition. Stress can have an impact on these outcomes, which in many cases, can be more influential in females, suggesting that gender differences exist. The adolescent period is a vulnerable time for the onset of certain psychopathologies, including anxiety disorders, depression and eating disorders, which are also more prevalent in females. One factor which may contribute to stress-triggered anxiety at puberty is the GABAA receptor (GABAR), which is known to play a pivotal role in anxiety. Expression of α4βδ GABARs increases on the dendrites of CA1 pyramidal cells at the onset of puberty in the hippocampus, part of the limbic circuitry which governs emotion. This receptor is a sensitive target for the stress steroid 3α-OH-5[α]β-pregnan-20-one or [allo]pregnanolone, which paradoxically reduces inhibition and increases anxiety during the pubertal period (post-natal day ∼35-44) of female mice in contrast to its usual effect to enhance inhibition and reduce anxiety. Spatial learning and synaptic plasticity are also adversely impacted at puberty, likely a result of increased expression of α4βδ GABARs on the dendritic spines of CA1 hippocampal pyramidal cells, which are essential for consolidation of memory. This review will focus on the role of these receptors in mediating behavioral changes at puberty. Stress-mediated changes in mood and cognition in early adolescence may have relevance for the expression of psychopathologies in adulthood.
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Affiliation(s)
- S S Smith
- Department of Physiology and Pharmacology, SUNY Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA.
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Shen H, Mohammad A, Ramroop J, Smith SS. A stress steroid triggers anxiety via increased expression of α4βδ GABAA receptors in methamphetamine dependence. Neuroscience 2013; 254:452-75. [PMID: 23994152 DOI: 10.1016/j.neuroscience.2013.08.033] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Revised: 08/13/2013] [Accepted: 08/20/2013] [Indexed: 10/26/2022]
Abstract
Methamphetamine (METH) is an addictive stimulant drug. In addition to drug craving and lethargy, METH withdrawal is associated with stress-triggered anxiety. However, the cellular basis for this stress-triggered anxiety is not understood. The present results suggest that during METH withdrawal (24h) following chronic exposure (3mg/kg, i.p. for 3-5weeks) of adult, male mice, the effect of one neurosteroid released by stress, 3α,5α-THP (3α-OH-5α-pregnan-20-one), and its 3α,5β isomer reverse to trigger anxiety assessed by the acoustic startle response (ASR), in contrast to their usual anti-anxiety effects. This novel effect of 3α,5β-THP was due to increased (three-fold) hippocampal expression of α4βδ GABAA receptors (GABARs) during METH withdrawal (24h-4weeks) because anxiogenic effects of 3α,5β-THP were not seen in α4-/- mice. 3α,5β-THP reduces current at these receptors when it is hyperpolarizing, as observed during METH withdrawal. As a result, 3α,5β-THP (30nM) increased neuronal excitability, assessed with current clamp and cell-attached recordings in CA1hippocampus, one CNS site which regulates anxiety. α4βδ GABARs were first increased 1h after METH exposure and recovered 6weeks after METH withdrawal. Similar increases in α4βδ GABARs and anxiogenic effects of 3α,5β-THP were noted in rats during METH withdrawal (24h). In contrast, the ASR was increased by chronic METH treatment in the absence of 3α,5β-THP administration due to its stimulant effect. Although α4βδ GABARs were increased by chronic METH treatment, the GABAergic current recorded from hippocampal neurons at this time was a depolarizing, shunting inhibition, which was potentiated by 3α,5β-THP. This steroid reduced neuronal excitability and anxiety during chronic METH treatment, consistent with its typical effect. Flumazenil (10mg/kg, i.p., 3×) reduced α4βδ expression and prevented the anxiogenic effect of 3α,5β-THP after METH withdrawal. Our findings suggest a novel mechanism underlying stress-triggered anxiety after METH withdrawal mediated by α4βδ GABARs.
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Affiliation(s)
- H Shen
- Department of Physiology and Pharmacology, SUNY Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, United States
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Egawa K, Yamada J, Furukawa T, Yanagawa Y, Fukuda A. Cl⁻ homeodynamics in gap junction-coupled astrocytic networks on activation of GABAergic synapses. J Physiol 2013; 591:3901-17. [PMID: 23732644 PMCID: PMC3764636 DOI: 10.1113/jphysiol.2013.257162] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The electrophysiological properties and functional role of GABAergic signal transmission from neurons to the gap junction-coupled astrocytic network are still unclear. GABA-induced astrocytic Cl− flux has been hypothesized to affect the driving force for GABAergic transmission by modulating [Cl−]o. Thus, revealing the properties of GABA-mediated astrocytic responses will deepen our understanding of GABAergic signal transmission. Here, we analysed the Cl− dynamics of neurons and astrocytes in CA1 hippocampal GABAergic tripartite synapses, using Cl− imaging during GABA application, and whole cell recordings from interneuron–astrocyte pairs in the stratum lacunosum-moleculare. Astrocytic [Cl−]i was adjusted to physiological conditions (40 mm). Although GABA application evoked bidirectional Cl− flux via GABAA receptors and mouse GABA transporter 4 (mGAT4) in CA1 astrocytes, a train of interneuron firing induced only GABAA receptor-mediated inward currents in an adjacent astrocyte. A GAT1 inhibitor increased the interneuron firing-induced currents and induced bicuculline-insensitive, mGAT4 inhibitor-sensitive currents, suggesting that synaptic spillover of GABA predominantly induced the astrocytic Cl− efflux because GABAA receptors are localized near the synaptic clefts. This GABA-induced Cl− efflux was accompanied by Cl− siphoning via the gap junctions of the astrocytic network because gap junction inhibitors significantly reduced the interneuron firing-induced currents. Thus, Cl− efflux from astrocytes is homeostatically maintained within astrocytic networks. A gap junction inhibitor enhanced the activity-dependent depolarizing shifts of reversal potential of neuronal IPSCs evoked by repetitive stimulation to GABAergic synapses. These results suggest that Cl− conductance within the astrocytic network may contribute to maintaining GABAergic synaptic transmission by regulating [Cl−]o.
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Affiliation(s)
- Kiyoshi Egawa
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan
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Higgins A, Yuan S, Wang Y, Burrell BD. Differential modulation of nociceptive versus non-nociceptive synapses by endocannabinoids. Mol Pain 2013; 9:26. [PMID: 23725095 PMCID: PMC3693973 DOI: 10.1186/1744-8069-9-26] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Accepted: 05/28/2013] [Indexed: 01/22/2023] Open
Abstract
Background Although a number of clinical and preclinical studies have demonstrated analgesic effects of cannabinoid treatments, there are also instances when cannabinoids have had no effect or even exacerbated pain. The observed pro-nociceptive effects appear to be due to cannabinoid-induced disinhibition of afferent synaptic input to nociceptive circuits. To better understand how cannabinoid-mediated plasticity can have both pro- and anti-nociceptive effects, we examined the possibility that cannabinoids differentially modulate nociceptive vs. non-nociceptive synapses onto a shared postsynaptic target. These experiments were carried out in the central nervous system (CNS) of the medicinal leech, in which it is possible to intracellularly record from presynaptic nociceptive (N-cell) or pressure-sensitive (P-cell) neurons and their shared postsynaptic targets. Results The endocannabinoid 2-arachidonoyl glycerol (2AG) elicited significant long-lasting depression in nociceptive (N-cell) synapses. However, non-nociceptive (P-cell) synapses were potentiated following 2AG treatment. 2AG-induced potentiation of non-nociceptive synapses was blocked by the TRPV antagonist SB366791, suggesting involvement of the same TRPV-like receptor that has already been shown to mediate endocannabinoid-dependent depression in nociceptive inputs. Treatment with the GABA receptor antagonist bicuculline also blocked 2AG-induced potentiation, consistent with the idea that increased synaptic signaling was the result of endocannabinoid-mediated disinhibition. Interestingly, while bicuculline by itself increased non-nociceptive synaptic transmission, nociceptive synapses were depressed by this GABA receptor antagonist indicating that nociceptive synapses were actually excited by GABAergic input. Consistent with these observations, GABA application depolarized the nociceptive afferent and hyperpolarized the non-nociceptive afferent. Conclusions These findings show that endocannabinoids can differentially modulate nociceptive vs. non-nociceptive synapses and that GABAergic regulation of these synapses plays an important role in determining whether endocannabinoids have a potentiating or depressing effect.
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Affiliation(s)
- Alexandra Higgins
- Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD 57069, USA
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Menzikov SA, Karpova MN, Kalinina MV. Effect of HCO3(-) ions on the ATP-dependent GABA(A) receptor-coupled Cl(-) channel in rat brain plasma membranes. Bull Exp Biol Med 2012; 152:38-42. [PMID: 22803035 DOI: 10.1007/s10517-011-1448-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
Abstract
We studied the effect of Cl(-) (10-75 mM) and HCO(3)(-) ions (10-25 mM) on the ATP-dependent GABA(A) receptor-coupled Cl(-) channel (Cl(-)-ATPase) in rat brain plasma membranes. The total enzyme activity was detected in the presence of both anions at a Cl(-)/ HCO(3)(-) ratio of 5:1 (Cl(-), HCO(3)(-)-ATPase). Specific inhibitors of P-type transport ATPases (N-ethylmaleimide, o-vanadate, and oligomycin) suppressed Cl(-), HCO(3)(-)-ATPase, while the Cl(-)- and HCO(3)(-)-ATPase activities were low sensitive to these ligands. Bicuculline abolished the activating effect of Cl(-) and HCO(3)(-) ions on the enzyme. HCO(3)(-) ions had no effect on the ATP-dependent Cl(-) transport into proteoliposomes (with the involvement of reconstituted ATPase). In experiment with Cl(-)-preloaded liposomes, addition of HCO(3)(-) ions to the incubation medium caused the reversion of Cl(-) transport (ion efflux from liposomes). Our results suggest that HCO(3)(-) ions play an important role in the modification of properties of the ATP-dependent GABA(A) receptor-coupled Cl(-) channel and GABA(A) receptor-induced Cl(-)/ HCO(3)(-) exchange. These ions are probably involved in GABA(A) receptor-induced Cl(-)/ HCO(3)(-) exchange in neuronal membranes.
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Affiliation(s)
- S A Menzikov
- State Research Institute of General Pathology and Pathological Physiology, Russian Academy of Medical Sciences, Moscow, Russia.
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Ransom CB, Tao W, Wu Y, Spain WJ, Richerson GB. Rapid regulation of tonic GABA currents in cultured rat hippocampal neurons. J Neurophysiol 2012; 109:803-12. [PMID: 23114210 DOI: 10.1152/jn.00460.2012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Subacute and chronic changes in tonic GABAergic inhibition occur in human and experimental epilepsy. Less is known about how tonic inhibition is modulated over shorter time frames (seconds). We measured endogenous tonic GABA currents from cultured rat hippocampal neurons to evaluate how they are affected by 1) transient increases in extracellular GABA concentration ([GABA]), 2) transient postsynaptic depolarization, and 3) depolarization of presynaptic cells. Transient increases in [GABA] (1 μM) reduced tonic currents; this reduction resulted from GABA-induced shifts in the reversal potential for GABA currents (E(GABA)). Transient depolarization of postsynaptic neurons reversed the effects of exogenous GABA and potentiated tonic currents. The voltage-dependent potentiation of tonic GABA currents was independent of E(GABA) shifts and represented postdepolarization potentiation (PDP), an intrinsic GABA(A) receptor property (Ransom CB, Wu Y, Richerson GB. J Neurosci 30: 7672-7684, 2010). Inhibition of vesicular GABA release with concanamycin A (ConA) did not affect tonic currents. In ConA-treated cells, transient application of 12 mM K(+) to depolarize presynaptic neurons and glia produced a persistent increase in tonic current amplitude. The K(+)-induced increase in tonic current was reversibly inhibited by SKF89976a (40 μM), indicating that this was caused by nonvesicular GABA release from GABA transporter type 1 (GAT1). Nonvesicular GABA release due to GAT1 reversal also occurred in acute hippocampal brain slices. Our results indicate that tonic GABA currents are rapidly regulated by GABA-induced changes in intracellular Cl(-) concentration, PDP of extrasynaptic GABA(A) receptors, and nonvesicular GABA release. These mechanisms may influence tonic inhibition during seizures when neurons are robustly depolarized and extracellular GABA and K(+) concentrations are elevated.
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Affiliation(s)
- Christopher B Ransom
- Epilepsy Center of Excellence, Veterans Affairs Puget Sound Health Care System, Seattle, WA, USA.
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