101
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Amakhin DV, Ergina JL, Chizhov AV, Zaitsev AV. Synaptic Conductances during Interictal Discharges in Pyramidal Neurons of Rat Entorhinal Cortex. Front Cell Neurosci 2016; 10:233. [PMID: 27790093 PMCID: PMC5061778 DOI: 10.3389/fncel.2016.00233] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 09/26/2016] [Indexed: 11/13/2022] Open
Abstract
In epilepsy, the balance of excitation and inhibition underlying the basis of neural network activity shifts, resulting in neuronal network hyperexcitability and recurrent seizure-associated discharges. Mechanisms involved in ictal and interictal events are not fully understood, in particular, because of controversial data regarding the dynamics of excitatory and inhibitory synaptic conductances. In the present study, we estimated AMPAR-, NMDAR-, and GABAA R-mediated conductances during two distinct types of interictal discharge (IID) in pyramidal neurons of rat entorhinal cortex in cortico-hippocampal slices. Repetitively emerging seizure-like events and IIDs were recorded in high extracellular potassium, 4-aminopyridine, and reduced magnesium-containing solution. An original procedure for estimating synaptic conductance during IIDs was based on the differences among the current-voltage characteristics of the synaptic components. The synaptic conductance dynamics obtained revealed that the first type of IID is determined by activity of GABAA R channels with depolarized reversal potential. The second type of IID is determined by the interplay between excitation and inhibition, with early AMPAR and prolonged depolarized GABAA R and NMDAR-mediated components. The study then validated the contribution of these components to IIDs by intracellular pharmacological isolation. These data provide new insights into the mechanisms of seizures generation, development, and cessation.
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Affiliation(s)
- Dmitry V Amakhin
- Laboratory of Molecular Mechanisms of Neural Interactions, Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences Saint Petersburg, Russia
| | - Julia L Ergina
- Laboratory of Molecular Mechanisms of Neural Interactions, Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences Saint Petersburg, Russia
| | - Anton V Chizhov
- Laboratory of Molecular Mechanisms of Neural Interactions, Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of SciencesSaint Petersburg, Russia; Computational Physics Laboratory, Division of Plasma Physics, Atomic Physics and Astrophysics, Ioffe InstituteSaint Petersburg, Russia
| | - Aleksey V Zaitsev
- Laboratory of Molecular Mechanisms of Neural Interactions, Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences Saint Petersburg, Russia
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102
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Activation of GABA A receptors controls mesiotemporal lobe epilepsy despite changes in chloride transporters expression: In vivo and in silico approach. Exp Neurol 2016; 284:11-28. [DOI: 10.1016/j.expneurol.2016.07.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Revised: 07/12/2016] [Accepted: 07/16/2016] [Indexed: 12/16/2022]
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103
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Spampanato J, Sullivan RKP, Perumal MB, Sah P. Development and physiology of GABAergic feedback excitation in parvalbumin expressing interneurons of the mouse basolateral amygdala. Physiol Rep 2016; 4:4/1/e12664. [PMID: 26733246 PMCID: PMC4760394 DOI: 10.14814/phy2.12664] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
We have previously shown that in the basolateral amygdala (BLA), action potentials in one type of parvalbumin (PV)-expressing GABAergic interneuron can evoke a disynaptic feedback excitatory postsynaptic potential (fbEPSP) onto the same presynaptic interneuron. Here, using whole-cell recordings from PV-expressing interneurons in acute brain slices we expand on this finding to show that this response is first detectable at 2-week postnatal, and is most prevalent in animals beyond 3 weeks of age (>P21). This circuit has a very high fidelity, and single action potential evoked fbEPSPs display few failures. Reconstruction of filled neurons, and electron microscopy show that interneurons that receive feedback excitation make symmetrical synapses on both the axon initial segments (AIS), as well as the soma and proximal dendrites of local pyramidal neurons, suggesting fbEPSP interneurons are morphologically distinct from the highly specialized chandelier neurons that selectively target the axon initial segment of pyramidal neurons. Single PV interneurons could trigger very large (~ 1 nA) feedback excitatory postsynaptic currents (fbEPSCs) suggesting that these neurons are heavily reciprocally connected to local glutamatergic principal cells. We conclude that in the BLA, a subpopulation of PV interneurons forms a distinct neural circuit in which a single action potential can recruit multiple pyramidal neurons to discharge near simultaneously and feed back onto the presynaptic interneuron.
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Affiliation(s)
- Jay Spampanato
- The Queensland Brain Institute, The University of Queensland, St. Lucia, Australia
| | - Robert K P Sullivan
- The Queensland Brain Institute, The University of Queensland, St. Lucia, Australia
| | | | - Pankaj Sah
- The Queensland Brain Institute, The University of Queensland, St. Lucia, Australia
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104
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Kelley MR, Deeb TZ, Brandon NJ, Dunlop J, Davies PA, Moss SJ. Compromising KCC2 transporter activity enhances the development of continuous seizure activity. Neuropharmacology 2016; 108:103-10. [PMID: 27108931 PMCID: PMC5337122 DOI: 10.1016/j.neuropharm.2016.04.029] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Revised: 04/05/2016] [Accepted: 04/20/2016] [Indexed: 11/17/2022]
Abstract
Impaired neuronal inhibition has long been associated with the increased probability of seizure occurrence and heightened seizure severity. Fast synaptic inhibition in the brain is primarily mediated by the type A γ-aminobutyric acid receptors (GABAARs), ligand-gated ion channels that can mediate Cl(-) influx resulting in membrane hyperpolarization and the restriction of neuronal firing. In most adult brain neurons, the K(+)/Cl(-) co-transporter-2 (KCC2) establishes hyperpolarizing GABAergic inhibition by maintaining low [Cl(-)]i. In this study, we sought to understand how decreased KCC2 transport function affects seizure event severity. We impaired KCC2 transport in the 0-Mg(2+) ACSF and 4-aminopyridine in vitro models of epileptiform activity in acute mouse brain slices. Experiments with the selective KCC2 inhibitor VU0463271 demonstrated that reduced KCC2 transport increased the duration of SLEs, resulting in non-terminating discharges of clonic-like activity. We also investigated slices obtained from the KCC2-Ser940Ala (S940A) point-mutant mouse, which has a mutation at a known functional phosphorylation site causing behavioral and cellular deficits under hyperexcitable conditions. We recorded from the entorhinal cortex of S940A mouse brain slices in both 0-Mg(2+) ACSF and 4-aminopyridine, and demonstrated that loss of the S940 residue increased the susceptibility of continuous clonic-like discharges, an in vitro form of status epilepticus. Our experiments revealed KCC2 transport activity is a critical factor in seizure event duration and mechanisms of termination. Our results highlight the need for therapeutic strategies that potentiate KCC2 transport function in order to decrease seizure event severity and prevent the development of status epilepticus.
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Affiliation(s)
- Matthew R Kelley
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Tarek Z Deeb
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, MA 02111, USA
| | - Nicholas J Brandon
- AstraZeneca Neuroscience, Innovative Medicines and Early Development Biotech Unit, 141, Portland St, Cambridge, MA, USA
| | - John Dunlop
- AstraZeneca Neuroscience, Innovative Medicines and Early Development Biotech Unit, 141, Portland St, Cambridge, MA, USA
| | - Paul A Davies
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Stephen J Moss
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA; AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, MA 02111, USA; Department of Neuroscience, Physiology and Pharmacology, University College, London, WC1E 6BT, UK.
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105
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Doyon N, Vinay L, Prescott SA, De Koninck Y. Chloride Regulation: A Dynamic Equilibrium Crucial for Synaptic Inhibition. Neuron 2016; 89:1157-1172. [PMID: 26985723 DOI: 10.1016/j.neuron.2016.02.030] [Citation(s) in RCA: 156] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2015] [Revised: 12/24/2015] [Accepted: 02/18/2016] [Indexed: 01/02/2023]
Abstract
Fast synaptic inhibition relies on tight regulation of intracellular Cl(-). Chloride dysregulation is implicated in several neurological and psychiatric disorders. Beyond mere disinhibition, the consequences of Cl(-) dysregulation are multifaceted and best understood in terms of a dynamical system involving complex interactions between multiple processes operating on many spatiotemporal scales. This dynamical perspective helps explain many unintuitive manifestations of Cl(-) dysregulation. Here we discuss how taking into account dynamical regulation of intracellular Cl(-) is important for understanding how synaptic inhibition fails, how to best detect that failure, why Cl(-) regulation is energetically so expensive, and the overall consequences for therapeutics.
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Affiliation(s)
- Nicolas Doyon
- Institut Universitaire en Santé Mentale de Québec, Québec, QC G1J 2G3, Canada; Department of Mathematics and Statistics, Université Laval, Québec, QC G1V 0A6, Canada
| | - Laurent Vinay
- Team P3M, Institut de Neurosciences de la Timone, UMR 7289, CNRS and Aix Marseille Université, F-13385 Marseille, France
| | - Steven A Prescott
- Program in Neurosciences and Mental Health, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Yves De Koninck
- Institut Universitaire en Santé Mentale de Québec, Québec, QC G1J 2G3, Canada; Department of Psychiatry and Neuroscience, Université Laval, Québec, QC, G1V 0A6, Canada.
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106
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Reduced Labeling of Parvalbumin Neurons and Perineuronal Nets in the Dorsolateral Prefrontal Cortex of Subjects with Schizophrenia. Neuropsychopharmacology 2016; 41:2206-14. [PMID: 26868058 PMCID: PMC4946056 DOI: 10.1038/npp.2016.24] [Citation(s) in RCA: 162] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Revised: 01/06/2016] [Accepted: 02/08/2016] [Indexed: 12/14/2022]
Abstract
Alterations in cortical parvalbumin (PV)-containing neurons, including a reduced density of detectable neurons and lower PV levels, have frequently been reported in the dorsolateral prefrontal cortex (DLPFC) of schizophrenia subjects. Most PV neurons are surrounded by perineuronal nets (PNNs) and the density of PNNs, as detected by Wisteria floribunda agglutinin (WFA) labeling, has been reported to be lower in schizophrenia. However, the nature of these PNN alterations, and their relationship to disease-related changes in PV neurons, has not been assessed. Using confocal microscopy, we quantified the densities and fluorescence intensities of PV neurons and PNNs labeled with WFA or immunoreactive for the major PNN protein, aggrecan, in the DLPFC from schizophrenia and matched comparison subjects. In schizophrenia, the densities of PV cells and of PNNs were not altered; however, the fluorescence intensities of PV immunoreactivity in cell bodies and of WFA labeling and aggrecan immunoreactivity in individual PNNs around PV cells were lower. These findings indicate that the normal complements of PV cells and PNNs are preserved in schizophrenia, but the levels of PV protein and of individual PNN components, especially the carbohydrate moieties on proteoglycans to which WFA binds, are lower. Given the roles of PV neurons in regulating DLPFC microcircuits and of PNNs in regulating PV cellular physiology, the identified alterations in PV neurons and their PNNs could contribute to DLPFC dysfunction in schizophrenia.
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107
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Driggers CM, Kean KM, Hirschberger LL, Cooley RB, Stipanuk MH, Karplus PA. Structure-Based Insights into the Role of the Cys-Tyr Crosslink and Inhibitor Recognition by Mammalian Cysteine Dioxygenase. J Mol Biol 2016; 428:3999-4012. [PMID: 27477048 DOI: 10.1016/j.jmb.2016.07.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2016] [Revised: 07/15/2016] [Accepted: 07/18/2016] [Indexed: 10/21/2022]
Abstract
In mammals, the non-heme iron enzyme cysteine dioxygenase (CDO) helps regulate Cys levels through converting Cys to Cys sulfinic acid. Its activity is in part modulated by the formation of a Cys93-Tyr157 crosslink that increases its catalytic efficiency over 10-fold. Here, 21 high-resolution mammalian CDO structures are used to gain insight into how the Cys-Tyr crosslink promotes activity and how select competitive inhibitors bind. Crystal structures of crosslink-deficient C93A and Y157F variants reveal similar ~1.0-Å shifts in the side chain of residue 157, and both variant structures have a new chloride ion coordinating the active site iron. Cys binding is also different from wild-type CDO, and no Cys-persulfenate forms in the C93A or Y157F active sites at pH6.2 or 8.0. We conclude that the crosslink enhances activity by positioning the Tyr157 hydroxyl to enable proper Cys binding, proper oxygen binding, and optimal chemistry. In addition, structures are presented for homocysteine (Hcy), D-Cys, thiosulfate, and azide bound as competitive inhibitors. The observed binding modes of Hcy and D-Cys clarify why they are not substrates, and the binding of azide shows that in contrast to what has been proposed, it does not bind in these crystals as a superoxide mimic.
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Affiliation(s)
- Camden M Driggers
- Department of Biochemistry and Biophysics, 2011 Ag & Life Sciences Building, Oregon State University, Corvallis, OR 97331, USA
| | - Kelsey M Kean
- Department of Biochemistry and Biophysics, 2011 Ag & Life Sciences Building, Oregon State University, Corvallis, OR 97331, USA
| | - Lawrence L Hirschberger
- Department of Nutritional Sciences, 227 Savage Hall, Cornell University, Ithaca, NY 14853, USA
| | - Richard B Cooley
- Department of Biochemistry and Biophysics, 2011 Ag & Life Sciences Building, Oregon State University, Corvallis, OR 97331, USA
| | - Martha H Stipanuk
- Department of Nutritional Sciences, 227 Savage Hall, Cornell University, Ithaca, NY 14853, USA.
| | - P Andrew Karplus
- Department of Biochemistry and Biophysics, 2011 Ag & Life Sciences Building, Oregon State University, Corvallis, OR 97331, USA.
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108
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Johansson S, Yelhekar TD, Druzin M. Commentary: Chloride Regulation: A Dynamic Equilibrium Crucial for Synaptic Inhibition. Front Cell Neurosci 2016; 10:182. [PMID: 27487962 PMCID: PMC4949234 DOI: 10.3389/fncel.2016.00182] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 07/06/2016] [Indexed: 11/13/2022] Open
Affiliation(s)
- Staffan Johansson
- Section for Physiology, Department of Integrative Medical Biology, Umeå University Umeå, Sweden
| | - Tushar D Yelhekar
- Section for Physiology, Department of Integrative Medical Biology, Umeå University Umeå, Sweden
| | - Michael Druzin
- Section for Physiology, Department of Integrative Medical Biology, Umeå University Umeå, Sweden
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109
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Abstract
Epilepsy is among the most prevalent chronic neurological diseases and affects an estimated 2.2 million people in the United States alone. About one third of patients are resistant to currently available antiepileptic drugs, which are exclusively targeting neuronal function. Yet, reactive astrocytes have emerged as potential contributors to neuronal hyperexcitability and seizures. Astrocytes react to any kind of CNS insult with a range of cellular adjustments to form a scar and protect uninjured brain regions. This process changes astrocyte physiology and can affect neuronal network function in various ways. Traumatic brain injury and stroke, both conditions that trigger astroglial scar formation, are leading causes of acquired epilepsies and surgical removal of this glial scar in patients with drug-resistant epilepsy can alleviate the seizures. This review will summarize the currently available evidence suggesting that epilepsy is not a disease of neurons alone, but that astrocytes, glial cells in the brain, can be major contributors to the disease, especially when they adopt a reactive state in response to central nervous system insult.
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Affiliation(s)
- Stefanie Robel
- Virginia Tech Carilion Research Institute, Roanoke, VA, USA
- Virginia Tech School of Neuroscience, Blacksburg, VA, USA
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110
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Glykys J, Staley KJ. Developmental Decrease of Neuronal Chloride Concentration Is Independent of Trauma in Thalamocortical Brain Slices. PLoS One 2016; 11:e0158012. [PMID: 27337272 PMCID: PMC4919081 DOI: 10.1371/journal.pone.0158012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 05/19/2016] [Indexed: 01/22/2023] Open
Abstract
The intraneuronal chloride concentration ([Cl-]i) is paramount for determining the polarity of signaling at GABAA synapses in the central nervous system. Sectioning hippocampal brain slices increases [Cl-]i in the superficial layers. It is not known whether cutting trauma also increases [Cl-]i in the neocortex and thalamus, and whether the effects of trauma change during development. We used Cl- imaging to study the [Cl-]i vs. the distance from the cut surface in acute thalamocortical slices from mice at developmental ages ranging from post-natal day 5 (P5) to P20. We demonstrate: 1) [Cl-]i is higher in the most superficial areas in both neocortical and thalamic brain slices at all ages tested and, 2) there is a developmental decrease in [Cl-]i that is independent of acute trauma caused by brain slicing. We conclude that [Cl-]i has a developmental progression during P5-20 in both the neocortex and thalamus. However, in both brain regions and during development the neurons closest to the slicing trauma have an elevated [Cl-]i.
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Affiliation(s)
- Joseph Glykys
- Department of Neurology, Division of Child Neurology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
| | - Kevin J. Staley
- Department of Neurology, Division of Child Neurology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Harvard Medical School, Boston, Massachusetts, United States of America
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111
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Paredes JM, Idilli AI, Mariotti L, Losi G, Arslanbaeva LR, Sato SS, Artoni P, Szczurkowska J, Cancedda L, Ratto GM, Carmignoto G, Arosio D. Synchronous Bioimaging of Intracellular pH and Chloride Based on LSS Fluorescent Protein. ACS Chem Biol 2016; 11:1652-60. [PMID: 27031242 DOI: 10.1021/acschembio.6b00103] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Ion homeostasis regulates critical physiological processes in the living cell. Intracellular chloride concentration not only contributes in setting the membrane potential of quiescent cells but it also plays a role in modulating the dynamic voltage changes during network activity. Dynamic chloride imaging demands new tools, allowing faster acquisition rates and correct accounting of concomitant pH changes. Joining a long-Stokes-shift red-fluorescent protein to a GFP variant with high sensitivity to pH and chloride, we obtained LSSmClopHensor, a genetically encoded fluorescent biosensor optimized for the simultaneous chloride and pH imaging and requiring only two excitation wavelengths (458 and 488 nm). LSSmClopHensor allowed us to monitor the dynamic changes of intracellular pH and chloride concentration during seizure like discharges in neocortical brain slices. Only cells with tightly controlled resting potential revealed a narrow distribution of chloride concentration peaking at about 5 and 8 mM, in neocortical neurons and SK-N-SH cells, respectively. We thus showed that LSSmClopHensor represents a new versatile tool for studying the dynamics of chloride and proton concentration in living systems.
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Affiliation(s)
- Jose M. Paredes
- Institute of Biophysics, CNR, Via
alla Cascata 56/C, 38123 Trento, Italy
- Bruno Kessler Foundation, Via
Sommarive 18, 38123 Trento, Italy
| | - Aurora I. Idilli
- Institute of Biophysics, CNR, Via
alla Cascata 56/C, 38123 Trento, Italy
| | - Letizia Mariotti
- Neuroscience Institute, CNR, Viale
G. Colombo 3, 35121 Padova, Italy
| | - Gabriele Losi
- Neuroscience Institute, CNR, Viale
G. Colombo 3, 35121 Padova, Italy
| | - Lyaysan R. Arslanbaeva
- Institute of Biophysics, CNR, Via
alla Cascata 56/C, 38123 Trento, Italy
- CIBIO, University of Trento, Via delle Regole 101, 38123 Trento, Italy
| | | | | | | | | | - Gian Michele Ratto
- Nanoscience Institute, CNR, Pisa, Italy
- Scuola Normale Superiore, Pisa, Italy
| | | | - Daniele Arosio
- Institute of Biophysics, CNR, Via
alla Cascata 56/C, 38123 Trento, Italy
- CIBIO, University of Trento, Via delle Regole 101, 38123 Trento, Italy
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112
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SLC26A11 (KBAT) in Purkinje Cells Is Critical for Inhibitory Transmission and Contributes to Locomotor Coordination. eNeuro 2016; 3:eN-NWR-0028-16. [PMID: 27390771 PMCID: PMC4908300 DOI: 10.1523/eneuro.0028-16.2016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 05/21/2016] [Accepted: 05/24/2016] [Indexed: 11/24/2022] Open
Abstract
Chloride homeostasis determines the impact of inhibitory synaptic transmission and thereby mediates the excitability of neurons. Even though cerebellar Purkinje cells (PCs) receive a pronounced inhibitory GABAergic input from stellate and basket cells, the role of chloride homeostasis in these neurons is largely unknown. Here we studied at both the cellular and systems physiological level the function of a recently discovered chloride channel, SLC26A11 or kidney brain anion transporter (KBAT), which is prominently expressed in PCs. Using perforated patch clamp recordings of PCs, we found that a lack of KBAT channel in PC-specific KBAT KO mice (L7-KBAT KOs) induces a negative shift in the reversal potential of chloride as reflected in the GABAA-receptor-evoked currents, indicating a decrease in intracellular chloride concentration. Surprisingly, both in vitro and in vivo PCs in L7-KBAT KOs showed a significantly increased action potential firing frequency of simple spikes, which correlated with impaired motor performance on the Erasmus Ladder. Our findings support an important role for SLC26A11 in moderating chloride homeostasis and neuronal activity in the cerebellum.
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113
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Mohapatra N, Tønnesen J, Vlachos A, Kuner T, Deller T, Nägerl UV, Santamaria F, Jedlicka P. Spines slow down dendritic chloride diffusion and affect short-term ionic plasticity of GABAergic inhibition. Sci Rep 2016; 6:23196. [PMID: 26987404 PMCID: PMC4796789 DOI: 10.1038/srep23196] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Accepted: 02/29/2016] [Indexed: 12/20/2022] Open
Abstract
Cl− plays a crucial role in neuronal function and synaptic inhibition. However, the impact of neuronal morphology on the diffusion and redistribution of intracellular Cl− is not well understood. The role of spines in Cl− diffusion along dendritic trees has not been addressed so far. Because measuring fast and spatially restricted Cl− changes within dendrites is not yet technically possible, we used computational approaches to predict the effects of spines on Cl− dynamics in morphologically complex dendrites. In all morphologies tested, including dendrites imaged by super-resolution STED microscopy in live brain tissue, spines slowed down longitudinal Cl− diffusion along dendrites. This effect was robust and could be observed in both deterministic as well as stochastic simulations. Cl− extrusion altered Cl− diffusion to a much lesser extent than the presence of spines. The spine-dependent slowing of Cl− diffusion affected the amount and spatial spread of changes in the GABA reversal potential thereby altering homosynaptic as well as heterosynaptic short-term ionic plasticity at GABAergic synapses in dendrites. Altogether, our results suggest a fundamental role of dendritic spines in shaping Cl− diffusion, which could be of relevance in the context of pathological conditions where spine densities and neural excitability are perturbed.
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Affiliation(s)
- Namrata Mohapatra
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, Frankfurt/Main, Germany
| | - Jan Tønnesen
- Interdisciplinary Institute for Neuroscience, CNRS UMR 5297, Bordeaux, France.,Interdisciplinary Institute for Neuroscience, University of Bordeaux, France
| | - Andreas Vlachos
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, Frankfurt/Main, Germany
| | - Thomas Kuner
- Institute of Anatomy and Cell Biology, Heidelberg University, Heidelberg, Germany
| | - Thomas Deller
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, Frankfurt/Main, Germany
| | - U Valentin Nägerl
- Interdisciplinary Institute for Neuroscience, CNRS UMR 5297, Bordeaux, France.,Interdisciplinary Institute for Neuroscience, University of Bordeaux, France
| | - Fidel Santamaria
- Biology Department and Neurosciences Institute, The University of Texas at San Antonio, San Antonio, USA
| | - Peter Jedlicka
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, Frankfurt/Main, Germany
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114
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Abstract
γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the cerebral cortex. GABAergic inhibition enables synchronization of activity in cortical networks, and contributes to generation of variety of brain activity patterns. In relation to epilepsy, GABAergic inhibition has been traditionally viewed as the main mechanism counterbalancing glutamatergic excitation and preventing hypersynchronous neuronal discharges. Indeed, deficits in GABAergic functions most commonly result in a hyperexcitable epileptic state, and many of the currently used antiepileptic drugs act through enhancement of GABAergic functions. However, a number of observations show that some epileptiform activity patterns involve synchronization by GABAergic mechanisms. These include two main categories that will be reviewed here: (1) synchronization of epileptiform oscillations based on GABAergic inhibition, and (2) epileptiform events driven by depolarizing and excitatory GABA. The conclusion is reached that GABAergic control of spike timing, either through inhibition or excitation under certain conditions, may work as a powerful synchronizing mechanism during epilepsy.
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Affiliation(s)
- Roustem Khazipov
- INMED-INSERM U901, 13273 Marseille Cedex 09, France Aix-Marseille University, 13273 Marseille Cedex 09, France Laboratory of Neurobiology, Kazan Federal University, 420008 Kazan, Russia
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115
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Unique chloride-sensing properties of WNK4 permit the distal nephron to modulate potassium homeostasis. Kidney Int 2016; 89:127-34. [PMID: 26422504 PMCID: PMC4814375 DOI: 10.1038/ki.2015.289] [Citation(s) in RCA: 188] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Revised: 07/13/2015] [Accepted: 07/31/2015] [Indexed: 11/09/2022]
Abstract
Dietary potassium deficiency activates thiazide-sensitive sodium chloride cotransport along the distal nephron. This may explain, in part, the hypertension and cardiovascular mortality observed in individuals who consume a low-potassium diet. Recent data suggest that plasma potassium affects the distal nephron directly by influencing intracellular chloride, an inhibitor of the with-no-lysine kinase (WNK)-Ste20p-related proline- and alanine-rich kinase (SPAK) pathway. As previous studies used extreme dietary manipulations, we sought to determine whether the relationship between potassium and NaCl cotransporter (NCC) is physiologically relevant and clarify the mechanisms involved. We report that modest changes in both dietary and plasma potassium affect NCC in vivo. Kinase assay studies showed that chloride inhibits WNK4 kinase activity at lower concentrations than it inhibits activity of WNK1 or WNK3. Also, chloride inhibited WNK4 within the range of distal cell chloride concentration. Mutation of a previously identified WNK chloride-binding motif converted WNK4 effects on SPAK from inhibitory to stimulatory in mammalian cells. Disruption of this motif in WNKs 1, 3, and 4 had different effects on NCC, consistent with the three WNKs having different chloride sensitivities. Thus, potassium effects on NCC are graded within the physiological range, which explains how unique chloride-sensing properties of WNK4 enable it to mediate effects of potassium on NCC in vivo.
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116
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Distribution of N-Acetylgalactosamine-Positive Perineuronal Nets in the Macaque Brain: Anatomy and Implications. Neural Plast 2016; 2016:6021428. [PMID: 26881119 PMCID: PMC4735937 DOI: 10.1155/2016/6021428] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 08/17/2015] [Accepted: 08/26/2015] [Indexed: 11/17/2022] Open
Abstract
Perineuronal nets (PNNs) are extracellular molecules that form around neurons near the end of critical periods during development. They surround neuronal cell bodies and proximal dendrites. PNNs inhibit the formation of new connections and may concentrate around rapidly firing inhibitory interneurons. Previous work characterized the important role of perineuronal nets in plasticity in the visual system, amygdala, and spinal cord of rats. In this study, we use immunohistochemistry to survey the distribution of perineuronal nets in representative areas of the primate brain. We also document changes in PNN prevalence in these areas in animals of different ages. We found that PNNs are most prevalent in the cerebellar nuclei, surrounding >90% of the neurons there. They are much less prevalent in cerebral cortex, surrounding less than 10% of neurons in every area that we examined. The incidence of perineuronal nets around parvalbumin-positive neurons (putative fast-spiking interneurons) varies considerably between different areas in the brain. Our survey indicates that the presence of PNNs may not have a simple relationship with neural plasticity and may serve multiple functions in the central nervous system.
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117
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Robel S, Sontheimer H. Glia as drivers of abnormal neuronal activity. Nat Neurosci 2016; 19:28-33. [PMID: 26713746 PMCID: PMC4966160 DOI: 10.1038/nn.4184] [Citation(s) in RCA: 139] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 09/04/2015] [Indexed: 12/13/2022]
Abstract
Reactive astrocytes have been proposed to become incompetent bystanders in epilepsy as a result of cellular changes rendering them unable to perform important housekeeping functions. Indeed, successful surgical treatment of mesiotemporal lobe epilepsy hinges on the removal of the glial scar. New research now extends the role of astrocytes, suggesting that they may drive the disease process by impairing the inhibitory action of neuronal GABA receptors. Here we discuss studies that include hyperexcitability resulting from impaired supply of astrocytic glutamine for neuronal GABA synthesis, and epilepsy resulting from genetically induced astrogliosis or malignant transformation, both of which render the inhibitory neurotransmitter GABA excitatory. In these examples, glial cells alter the expression or function of neuronal proteins involved in excitability. Although epilepsy has traditionally been thought of as a disease caused by changes in neuronal properties exclusively, these new findings challenge us to consider the contribution of glial cells as drivers of epileptogenesis in acquired epilepsies.
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Affiliation(s)
- Stefanie Robel
- Virginia Tech Carilion Research Institute, Glial Biology in Health, Disease, and Cancer Center, Roanoke, Virginia, USA
| | - Harald Sontheimer
- Virginia Tech Carilion Research Institute, Glial Biology in Health, Disease, and Cancer Center, Roanoke, Virginia, USA
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118
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Kahle KT, Delpire E. Kinase-KCC2 coupling: Cl- rheostasis, disease susceptibility, therapeutic target. J Neurophysiol 2016; 115:8-18. [PMID: 26510764 PMCID: PMC4760510 DOI: 10.1152/jn.00865.2015] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 10/25/2015] [Indexed: 01/06/2023] Open
Abstract
The intracellular concentration of Cl(-) ([Cl(-)]i) in neurons is a highly regulated variable that is established and modulated by the finely tuned activity of the KCC2 cotransporter. Despite the importance of KCC2 for neurophysiology and its role in multiple neuropsychiatric diseases, our knowledge of the transporter's regulatory mechanisms is incomplete. Recent studies suggest that the phosphorylation state of KCC2 at specific residues in its cytoplasmic COOH terminus, such as Ser940 and Thr906/Thr1007, encodes discrete levels of transporter activity that elicit graded changes in neuronal Cl(-) extrusion to modulate the strength of synaptic inhibition via Cl(-)-permeable GABAA receptors. In this review, we propose that the functional and physical coupling of KCC2 to Cl(-)-sensitive kinase(s), such as the WNK1-SPAK kinase complex, constitutes a molecular "rheostat" that regulates [Cl(-)]i and thereby influences the functional plasticity of GABA. The rapid reversibility of (de)phosphorylation facilitates regulatory precision, and multisite phosphorylation allows for the control of KCC2 activity by different inputs via distinct or partially overlapping upstream signaling cascades that may become more or less important depending on the physiological context. While this adaptation mechanism is highly suited to maintaining homeostasis, its adjustable set points may render it vulnerable to perturbation and dysregulation. Finally, we suggest that pharmacological modulation of this kinase-KCC2 rheostat might be a particularly efficacious strategy to enhance Cl(-) extrusion and therapeutically restore GABA inhibition.
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Affiliation(s)
- Kristopher T Kahle
- Departments of Neurosurgery and Pediatrics, Yale School of Medicine, New Haven, Connecticut; Yale Neurogenetics Program, Yale School of Medicine, New Haven, Connecticut; and
| | - Eric Delpire
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee
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119
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Ben-Ari Y. Commentary: GABA depolarizes immature neurons and inhibits network activity in the neonatal neocortex in vivo. Front Cell Neurosci 2015; 9:478. [PMID: 26733806 PMCID: PMC4686958 DOI: 10.3389/fncel.2015.00478] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 11/24/2015] [Indexed: 11/13/2022] Open
Affiliation(s)
- Yehezkel Ben-Ari
- Institut National de la Santé et de la Recherche Médicale, Institut de Neurobiologie de la Méditerranée Neurochlore, Marseille, France
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Glykys J, Staley KJ. Diazepam effect during early neonatal development correlates with neuronal Cl(.). Ann Clin Transl Neurol 2015; 2:1055-70. [PMID: 26734658 PMCID: PMC4693588 DOI: 10.1002/acn3.259] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Accepted: 09/16/2015] [Indexed: 11/09/2022] Open
Abstract
Objective Although benzodiazepines and other GABAA receptors allosteric modulators are used to treat neonatal seizures, their efficacy may derive from actions on subcortical structures. Side effects of benzodiazepines in nonseizing human neonates include myoclonus, seizures, and abnormal movements. Excitatory actions of GABA may underlie both side effects and reduced anticonvulsant activity of benzodiazepines. Neocortical organotypic slice cultures were used to study: (1) spontaneous cortical epileptiform activity during early development; (2) developmental changes in [Cl−]i and (3) whether diazepam's anticonvulsant effect correlated with neuronal [Cl−]i. Methods Epileptiform activity in neocortical organotypic slice cultures was measured by field potential recordings. Cl− changes during development were assessed by multiphoton imaging of neurons transgenically expressing a Cl‐sensitive fluorophore. Clinically relevant concentrations of diazepam were used to test the anticonvulsant effectiveness at ages corresponding to premature neonates through early infancy. Results (1) Neocortical organotypic slices at days in vitro 5 (DIV5) exhibited spontaneous epileptiform activity. (2) Epileptiform event duration decreased with age. (3) There was a progressive decrease in [Cl−]i over the same age range. (4) Diazepam was ineffective in decreasing epileptiform activity at DIV5‐6, but progressively more effective at older ages through DIV15. (5) At DIV5‐6, diazepam worsened epileptiform activity in 50% of the slices. Interpretation The neocortical organotypic slice is a useful model to study spontaneous epileptiform activity. Decreasing [Cl−]i during development correlates with decreasing duration of spontaneous epileptiform activity and increasing anticonvulsant efficacy of diazepam. We provide a potential explanation for the reports of seizures and myoclonus induction by benzodiazepines in newborn human neonates and the limited electrographic efficacy of benzodiazepines for the treatment of neonatal seizures.
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Affiliation(s)
- Joseph Glykys
- Department of Neurology Massachusetts General Hospital Boston Massachusetts; Harvard Medical School Boston Massachusetts
| | - Kevin J Staley
- Department of Neurology Massachusetts General Hospital Boston Massachusetts; Harvard Medical School Boston Massachusetts
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Wietek J, Beltramo R, Scanziani M, Hegemann P, Oertner TG, Wiegert JS. An improved chloride-conducting channelrhodopsin for light-induced inhibition of neuronal activity in vivo. Sci Rep 2015; 5:14807. [PMID: 26443033 PMCID: PMC4595828 DOI: 10.1038/srep14807] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 09/09/2015] [Indexed: 11/09/2022] Open
Abstract
Channelrhodopsins are light-gated cation channels that have been widely used for optogenetic stimulation of electrically excitable cells. Replacement of a glutamic acid in the central gate with a positively charged amino acid residue reverses the ion selectivity and produces chloride-conducting ChRs (ChloCs). Expressed in neurons, published ChloCs produced a strong shunting effect but also a small, yet significant depolarization from the resting potential. Depending on the state of the neuron, the net result of illumination might therefore be inhibitory or excitatory with respect to action potential generation. Here we report two additional amino acid substitutions that significantly shift the reversal potential of improved ChloC (iChloC) to the reversal potential of endogenous GABAA receptors. As a result, light-evoked membrane depolarization was strongly reduced and spike initiation after current injection or synaptic stimulation was reliably inhibited in iChloC-transfected neurons in vitro. In the primary visual cortex of anesthetized mice, activation of iChloC suppressed spiking activity evoked by visual stimulation. Due to its high operational light sensitivity, iChloC makes it possible to inhibit neurons in a large volume of brain tissue from a small, point-like light source.
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Affiliation(s)
- Jonas Wietek
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, D-10115 Berlin, Germany
| | - Riccardo Beltramo
- Center for Neural Circuits and Behavior, University of California San Diego, La Jolla, CA 92093-0634, USA.,Howard Hughes Medical Institute, University of California San Diego, La Jolla, CA 92093-0634, USA
| | - Massimo Scanziani
- Center for Neural Circuits and Behavior, University of California San Diego, La Jolla, CA 92093-0634, USA.,Howard Hughes Medical Institute, University of California San Diego, La Jolla, CA 92093-0634, USA
| | - Peter Hegemann
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, D-10115 Berlin, Germany
| | - Thomas G Oertner
- Institute for Synaptic Physiology, Center for Molecular Neurobiology Hamburg, University Medical Center Hamburg-Eppendorf, D-20251 Hamburg, Germany
| | - J Simon Wiegert
- Institute for Synaptic Physiology, Center for Molecular Neurobiology Hamburg, University Medical Center Hamburg-Eppendorf, D-20251 Hamburg, Germany
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Oohashi T, Edamatsu M, Bekku Y, Carulli D. The hyaluronan and proteoglycan link proteins: Organizers of the brain extracellular matrix and key molecules for neuronal function and plasticity. Exp Neurol 2015; 274:134-44. [PMID: 26387938 DOI: 10.1016/j.expneurol.2015.09.010] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2015] [Revised: 09/11/2015] [Accepted: 09/17/2015] [Indexed: 02/06/2023]
Abstract
The hyaluronan and proteoglycanbinding link protein (Hapln) is a key molecule in the formation and control of hyaluronan-based condensed perineuronal matrix in the adult brain. This review summarizes the recent advances in understanding the role of Haplns in the formation and control of two distinct types of perineuronal matrices, one for "classical" PNN and the other for the specialized extracellular matrix (ECM) at the node of Ranvier in the central nervous system (CNS). We introduce the structural components of each ECM organization including the basic concept of supramolecular structure named "HLT model". We furthermore summarize the developmental and physiological role of perineuronal ECMs from the studies of Haplns and related molecules. Finally, we also discuss the potential mechanism modulating PNNs in the adult CNS. This layer of organized matrices may exert a direct effect via core protein or sugar moiety from the structure or by acting as a binding site for biologically active molecules, which are important for neuronal plasticity and saltatory conduction.
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Affiliation(s)
- Toshitaka Oohashi
- Department of Molecular Biology and Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan.
| | - Midori Edamatsu
- Department of Molecular Biology and Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan
| | - Yoko Bekku
- NYU Neuroscience Institute, New York University Langone Medical Center, 522 First Avenue, New York, NY 10016, USA
| | - Daniela Carulli
- Department of Neuroscience, Neuroscience Institute of Turin (NIT), Neuroscience Institute Cavalieri-Ottolenghi (NICO), University of Turin, Regione Gonzole 10, 10043 Orbassano, Turin, Italy
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123
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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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124
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Titz S, Sammler EM, Hormuzdi SG. Could tuning of the inhibitory tone involve graded changes in neuronal chloride transport? Neuropharmacology 2015; 95:321-31. [PMID: 25843644 DOI: 10.1016/j.neuropharm.2015.03.026] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Revised: 03/17/2015] [Accepted: 03/24/2015] [Indexed: 11/15/2022]
Abstract
Hyperpolarizing synaptic inhibition through GABAA and glycine receptors depends on the presence of the neuronal cation-chloride-cotransporter protein, KCC2. Several transcriptional and post-transcriptional mechanisms have been shown to regulate KCC2 and thereby influence the polarity and efficacy of inhibitory synaptic transmission. It is unclear however whether regulation of KCC2 enables the transporter to attain different levels of activity thus allowing a neuron to modulate the strength of inhibitory synaptic transmission to its changing requirements. We therefore investigated whether phosphorylation can allow KCC2 to achieve distinct levels of [Cl(-)]i in neurons. We generated a variety of KCC2 alanine dephosphorylation mimics and used NH4(+)-induced pHi shifts in cultured hippocampal neurons to quantify the rate of KCC2 transport activity exhibited by these mutants. To explore the relationship between KCC2 transport and GABAA receptor-mediated current amplitudes we performed gramicidine perforated-patch recordings. The correlation between EGABA and NH4(+)-induced pHi shifts enabled an estimate of the range of chloride extrusion possible by kinase/phosphatase regulation of KCC2. Our results demonstrate that KCC2 transport can vary considerably in magnitude depending on the combination of alanine mutations present on the protein. Transport can be enhanced to sufficiently high levels that hyperpolarizing GABAA responses may be obtained even in neurons with an extremely negative resting membrane potential and at high extracellular K(+) concentrations. Our findings highlight the significant potential for regulating the inhibitory tone by KCC2-mediated chloride extrusion and suggest that cellular signaling pathways may act combinatorially to alter KCC2 phosphorylation/dephosphorylation and thereby tune the strength of synaptic inhibition.
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Affiliation(s)
- Stefan Titz
- Institute for Physiology und Pathophysiology, University of Heidelberg, Im Neuenheimer Feld 326, 69120 Heidelberg, Germany.
| | - Esther M Sammler
- Division of Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK
| | - Sheriar G Hormuzdi
- Division of Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK.
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125
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Astorga G, Bao J, Marty A, Augustine GJ, Franconville R, Jalil A, Bradley J, Llano I. An excitatory GABA loop operating in vivo. Front Cell Neurosci 2015; 9:275. [PMID: 26236197 PMCID: PMC4503922 DOI: 10.3389/fncel.2015.00275] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 07/05/2015] [Indexed: 11/14/2022] Open
Abstract
While it has been proposed that the conventional inhibitory neurotransmitter GABA can be excitatory in the mammalian brain, much remains to be learned concerning the circumstances and the cellular mechanisms governing potential excitatory GABA action. Using a combination of optogenetics and two-photon calcium imaging in vivo, we find that activation of chloride-permeable GABAA receptors in parallel fibers (PFs) of the cerebellar molecular layer of adult mice causes parallel fiber excitation. Stimulation of PFs at submaximal stimulus intensities leads to GABA release from molecular layer interneurons (MLIs), thus creating a positive feedback loop that enhances excitation near the center of an activated PF bundle. Our results imply that elevated chloride concentration can occur in specific intracellular compartments of mature mammalian neurons and suggest an excitatory role for GABAA receptors in the cerebellar cortex of adult mice.
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Affiliation(s)
- Guadalupe Astorga
- Laboratory of Cerebral Physiology, CNRS and University Paris Descartes Paris, France
| | - Jin Bao
- Laboratory of Cerebral Physiology, CNRS and University Paris Descartes Paris, France
| | - Alain Marty
- Laboratory of Cerebral Physiology, CNRS and University Paris Descartes Paris, France
| | - George J Augustine
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, Singapore ; Institute of Molecular and Cell Biology Singapore, Singapore ; Center for Functional Connectomics, Korea Institute of Science and Technology Seoul, South Korea
| | - Romain Franconville
- Laboratory of Cerebral Physiology, CNRS and University Paris Descartes Paris, France
| | - Abdelali Jalil
- Laboratory of Cerebral Physiology, CNRS and University Paris Descartes Paris, France
| | - Jonathan Bradley
- Laboratory of Cerebral Physiology, CNRS and University Paris Descartes Paris, France
| | - Isabel Llano
- Laboratory of Cerebral Physiology, CNRS and University Paris Descartes Paris, France
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126
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Tora AS, Rovira X, Dione I, Bertrand H, Brabet I, De Koninck Y, Doyon N, Pin J, Acher F, Goudet C. Allosteric modulation of metabotropic glutamate receptors by chloride ions. FASEB J 2015; 29:4174-88. [DOI: 10.1096/fj.14-269746] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 06/15/2015] [Indexed: 11/11/2022]
Affiliation(s)
- Amélie S. Tora
- Institut de Génomique Fonctionnelle, CNRS, UMR 5203, Université de MontpellierMontpellierFrance
- INSERM U1191MontpellierFrance
| | - Xavier Rovira
- Institut de Génomique Fonctionnelle, CNRS, UMR 5203, Université de MontpellierMontpellierFrance
- INSERM U1191MontpellierFrance
| | - Ibrahima Dione
- Centre de Recherche de l'Institut Universitaire en Santé Mentale du Québec and Université LavalQuébecCanada
| | | | - Isabelle Brabet
- Institut de Génomique Fonctionnelle, CNRS, UMR 5203, Université de MontpellierMontpellierFrance
- INSERM U1191MontpellierFrance
| | - Yves De Koninck
- Centre de Recherche de l'Institut Universitaire en Santé Mentale du Québec and Université LavalQuébecCanada
| | - Nicolas Doyon
- Centre de Recherche de l'Institut Universitaire en Santé Mentale du Québec and Université LavalQuébecCanada
| | - Jean‐Philippe Pin
- Institut de Génomique Fonctionnelle, CNRS, UMR 5203, Université de MontpellierMontpellierFrance
- INSERM U1191MontpellierFrance
| | - Francine Acher
- Laboratoire de Chimie et Biochimie Pharmacologiques et ToxicologiquesCNRS, UMR 8601, Université Paris Descartes, Sorbonne Paris CitéParisFrance
| | - Cyril Goudet
- Institut de Génomique Fonctionnelle, CNRS, UMR 5203, Université de MontpellierMontpellierFrance
- INSERM U1191MontpellierFrance
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DiRaddo JO, Miller EJ, Bowman-Dalley C, Wroblewska B, Javidnia M, Grajkowska E, Wolfe BB, Liotta DC, Wroblewski JT. Chloride is an Agonist of Group II and III Metabotropic Glutamate Receptors. Mol Pharmacol 2015; 88:450-9. [DOI: 10.1124/mol.114.096420] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 06/18/2015] [Indexed: 01/07/2023] Open
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Krishnan V, Gleason E. Nitric oxide releases Cl(-) from acidic organelles in retinal amacrine cells. Front Cell Neurosci 2015; 9:213. [PMID: 26106295 PMCID: PMC4459082 DOI: 10.3389/fncel.2015.00213] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 05/19/2015] [Indexed: 02/03/2023] Open
Abstract
Determining the factors regulating cytosolic Cl(-) in neurons is fundamental to our understanding of the function of GABA- and glycinergic synapses. This is because the Cl(-) distribution across the postsynaptic plasma membrane determines the sign and strength of postsynaptic voltage responses. We have previously demonstrated that nitric oxide (NO) releases Cl(-) into the cytosol from an internal compartment in both retinal amacrine cells and hippocampal neurons. Furthermore, we have shown that the increase in cytosolic Cl(-) is dependent upon a decrease in cytosolic pH. Here, our goals were to confirm the compartmental nature of the internal Cl(-) store and to test the hypothesis that Cl(-) is being released from acidic organelles (AO) such as the Golgi, endosomes or lysosomes. To achieve this, we made whole cell voltage clamp recordings from cultured chick retinal amacrine cells and used GABA-gated currents to track changes in cytosolic Cl(-). Our results demonstrate that intact internal proton gradients are required for the NO-dependent release of internal Cl(-). Furthermore, we demonstrate that increasing the pH of AO leads to release of Cl(-) into the cytosol. Intriguingly, the elevation of organellar pH results in a reversal in the effects of NO. These results demonstrate that cytosolic Cl(-) is closely linked to the regulation and maintenance of organellar pH and provide evidence that acidic compartments are the target of NO.
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Affiliation(s)
- Vijai Krishnan
- Department of Biological Sciences, Louisiana State University Baton Rouge, LA, USA
| | - Evanna Gleason
- Department of Biological Sciences, Louisiana State University Baton Rouge, LA, USA
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129
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Han B, Bellemer A, Koelle MR. An evolutionarily conserved switch in response to GABA affects development and behavior of the locomotor circuit of Caenorhabditis elegans. Genetics 2015; 199:1159-72. [PMID: 25644702 PMCID: PMC4391577 DOI: 10.1534/genetics.114.173963] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 01/28/2015] [Indexed: 01/23/2023] Open
Abstract
The neurotransmitter gamma-aminobutyric acid (GABA) is depolarizing in the developing vertebrate brain, but in older animals switches to hyperpolarizing and becomes the major inhibitory neurotransmitter in adults. We discovered a similar developmental switch in GABA response in Caenorhabditis elegans and have genetically analyzed its mechanism and function in a well-defined circuit. Worm GABA neurons innervate body wall muscles to control locomotion. Activation of GABAA receptors with their agonist muscimol in newly hatched first larval (L1) stage animals excites muscle contraction and thus is depolarizing. At the mid-L1 stage, as the GABAergic neurons rewire onto their mature muscle targets, muscimol shifts to relaxing muscles and thus has switched to hyperpolarizing. This muscimol response switch depends on chloride transporters in the muscles analogous to those that control GABA response in mammalian neurons: the chloride accumulator sodium-potassium-chloride-cotransporter-1 (NKCC-1) is required for the early depolarizing muscimol response, while the two chloride extruders potassium-chloride-cotransporter-2 (KCC-2) and anion-bicarbonate-transporter-1 (ABTS-1) are required for the later hyperpolarizing response. Using mutations that disrupt GABA signaling, we found that neural circuit development still proceeds to completion but with an ∼6-hr delay. Using optogenetic activation of GABAergic neurons, we found that endogenous GABAA signaling in early L1 animals, although presumably depolarizing, does not cause an excitatory response. Thus a developmental depolarizing-to-hyperpolarizing shift is an ancient conserved feature of GABA signaling, but existing theories for why this shift occurs appear inadequate to explain its function upon rigorous genetic analysis of a well-defined neural circuit.
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Affiliation(s)
- Bingjie Han
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520
| | - Andrew Bellemer
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520
| | - Michael R Koelle
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520
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Rungta R, Choi H, Tyson J, Malik A, Dissing-Olesen L, Lin P, Cain S, Cullis P, Snutch T, MacVicar B. The Cellular Mechanisms of Neuronal Swelling Underlying Cytotoxic Edema. Cell 2015; 161:610-621. [DOI: 10.1016/j.cell.2015.03.029] [Citation(s) in RCA: 150] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Revised: 02/03/2015] [Accepted: 03/12/2015] [Indexed: 01/08/2023]
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131
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Synaptic GABA release prevents GABA transporter type-1 reversal during excessive network activity. Nat Commun 2015; 6:6597. [PMID: 25798861 PMCID: PMC4374149 DOI: 10.1038/ncomms7597] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Accepted: 02/10/2015] [Indexed: 12/15/2022] Open
Abstract
GABA transporters control extracellular GABA, which regulates the key aspects of neuronal and network behaviour. A prevailing view is that modest neuronal depolarization results in GABA transporter type-1 (GAT-1) reversal causing non-vesicular GABA release into the extracellular space during intense network activity. This has important implications for GABA uptake-targeting therapies. Here we combined a realistic kinetic model of GAT-1 with experimental measurements of tonic GABAA receptor currents in ex vivo hippocampal slices to examine GAT-1 operation under varying network conditions. Our simulations predict that synaptic GABA release during network activity robustly prevents GAT-1 reversal. We test this in the 0 Mg2+ model of epileptiform discharges using slices from healthy and chronically epileptic rats and find that epileptiform activity is associated with increased synaptic GABA release and is not accompanied by GAT-1 reversal. We conclude that sustained efflux of GABA through GAT-1 is unlikely to occur during physiological or pathological network activity. Membrane depolarization during increased neuronal activity as seen during epilepsy has been suggested to easily reverse neuronal GABA transporters. Here the authors use modelling and experimental data and challenge this view by showing that synaptic GABA release during excessive neuronal firing averts reversal of GABA uptake.
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Silayeva L, Deeb TZ, Hines RM, Kelley MR, Munoz MB, Lee HHC, Brandon NJ, Dunlop J, Maguire J, Davies PA, Moss SJ. KCC2 activity is critical in limiting the onset and severity of status epilepticus. Proc Natl Acad Sci U S A 2015; 112:3523-8. [PMID: 25733865 PMCID: PMC4371976 DOI: 10.1073/pnas.1415126112] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The K(+)/Cl(-) cotransporter (KCC2) allows adult neurons to maintain low intracellular Cl(-) levels, which are a prerequisite for efficient synaptic inhibition upon activation of γ-aminobutyric acid receptors. Deficits in KCC2 activity are implicated in epileptogenesis, but how increased neuronal activity leads to transporter inactivation is ill defined. In vitro, the activity of KCC2 is potentiated via phosphorylation of serine 940 (S940). Here we have examined the role this putative regulatory process plays in determining KCC2 activity during status epilepticus (SE) using knockin mice in which S940 is mutated to an alanine (S940A). In wild-type mice, SE induced by kainate resulted in dephosphorylation of S940 and KCC2 internalization. S940A homozygotes were viable and exhibited comparable basal levels of KCC2 expression and activity relative to WT mice. However, exposure of S940A mice to kainate induced lethality within 30 min of kainate injection and subsequent entrance into SE. We assessed the effect of the S940A mutation in cultured hippocampal neurons to explore the mechanisms underlying this phenotype. Under basal conditions, the mutation had no effect on neuronal Cl(-) extrusion. However, a selective deficit in KCC2 activity was seen in S940A neurons upon transient exposure to glutamate. Significantly, whereas the effects of glutamate on KCC2 function could be ameliorated in WT neurons with agents that enhance S940 phosphorylation, this positive modulation was lost in S940A neurons. Collectively our results suggest that phosphorylation of S940 plays a critical role in potentiating KCC2 activity to limit the development of SE.
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Affiliation(s)
- Liliya Silayeva
- AstraZeneca-Tufts Laboratory for Basic and Translational Neuroscience, Boston, MA 02111; Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111
| | - Tarek Z Deeb
- AstraZeneca-Tufts Laboratory for Basic and Translational Neuroscience, Boston, MA 02111; Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111
| | - Rochelle M Hines
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111
| | - Matt R Kelley
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111
| | - Michaelanne B Munoz
- AstraZeneca-Tufts Laboratory for Basic and Translational Neuroscience, Boston, MA 02111
| | - Henry H C Lee
- Department of Neurology, FM Kirby Neurobiology Center, Children's Hospital Boston-Harvard Medical School, Boston, MA 02115
| | - Nicholas J Brandon
- AstraZeneca-Tufts Laboratory for Basic and Translational Neuroscience, Boston, MA 02111; AstraZeneca Neuroscience Innovative Medicines, Cambridge, MA 02421; and
| | - John Dunlop
- AstraZeneca-Tufts Laboratory for Basic and Translational Neuroscience, Boston, MA 02111; AstraZeneca Neuroscience Innovative Medicines, Cambridge, MA 02421; and
| | - Jaime Maguire
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111
| | - Paul A Davies
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111
| | - Stephen J Moss
- AstraZeneca-Tufts Laboratory for Basic and Translational Neuroscience, Boston, MA 02111; Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111; AstraZeneca Neuroscience Innovative Medicines, Cambridge, MA 02421; and Department of Neuroscience, Physiology and Pharmacology, University College, London, WC1E 6BT, United Kingdom
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133
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Abstract
GABA(A) receptor-mediated synaptic transmission is responsible for inhibitory control of neural function in the brain. Recent progress has shown that GABA(A) receptors also provide a wide range of additional functions beyond simple inhibition. This diversity of functions is mediated by a large variety of different interneuron classes acting on a diverse population of receptor subtypes. Here, I will focus on an additional source of GABAergic signaling diversity, caused by the highly variable ion signaling mechanism of GABA(A) receptors. In concert with the other two sources of GABAergic heterogeneity, this variability in signaling allows for a wide array of GABAergic effects that are crucial for the development of the brain and its function.
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Affiliation(s)
- Kaspar Vogt
- International Institute for Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Tsukuba, Ibaraki, Japan.
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134
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Intracellular Cl- as a signaling ion that potently regulates Na+/HCO3- transporters. Proc Natl Acad Sci U S A 2015; 112:E329-37. [PMID: 25561556 DOI: 10.1073/pnas.1415673112] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cl(-) is a major anion in mammalian cells involved in transport processes that determines the intracellular activity of many ions and plasma membrane potential. Surprisingly, a role of intracellular Cl(-) (Cl(-) in) as a signaling ion has not been previously evaluated. Here we report that Cl(-) in functions as a regulator of cellular Na(+) and HCO3 (-) concentrations and transepithelial transport through modulating the activity of several electrogenic Na(+)-HCO3 (-) transporters. We describe the molecular mechanism(s) of this regulation by physiological Cl(-) in concentrations highlighting the role of GXXXP motifs in Cl(-) sensing. Regulation of the ubiquitous Na(+)-HCO3(-) co-transport (NBC)e1-B is mediated by two GXXXP-containing sites; regulation of NBCe2-C is dependent on a single GXXXP motif; and regulation of NBCe1-A depends on a cryptic GXXXP motif. In the basal state NBCe1-B is inhibited by high Cl(-) in interacting at a low affinity GXXXP-containing site. IP3 receptor binding protein released with IP3 (IRBIT) activation of NBCe1-B unmasks a second high affinity Cl(-) in interacting GXXXP-dependent site. By contrast, NBCe2-C, which does not interact with IRBIT, has a single high affinity N-terminal GXXP-containing Cl(-) in interacting site. NBCe1-A is unaffected by Cl(-) in between 5 and 140 mM. However, deletion of NBCe1-A residues 29-41 unmasks a cryptic GXXXP-containing site homologous with the NBCe1-B low affinity site that is involved in inhibition of NBCe1-A by Cl(-) in. These findings reveal a cellular Cl(-) in sensing mechanism that plays an important role in the regulation of Na(+) and HCO3 (-) transport, with critical implications for the role of Cl(-) in cellular ion homeostasis and epithelial fluid and electrolyte secretion.
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135
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Dzhala V, Staley KJ. Acute and chronic efficacy of bumetanide in an in vitro model of posttraumatic epileptogenesis. CNS Neurosci Ther 2014; 21:173-80. [PMID: 25495911 DOI: 10.1111/cns.12369] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 11/04/2014] [Accepted: 11/05/2014] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Seizures triggered by acute injuries to the developing brain respond poorly to first-line medications that target the inhibitory chloride-permeable GABAA receptor. Neuronal injury is associated with profound increases in cytoplasmic chloride ([Cl(-)]i) resulting in depolarizing GABA signaling, higher seizure propensity and limited efficacy of GABAergic anticonvulsants. The Na(+)-K(+)-2Cl(-) (NKCC1) cotransporter blocker bumetanide reduces [Cl(-)]i and causes more negative GABA equilibrium potential in injured neurons. We therefore tested both the acute and chronic efficacy of bumetanide on early posttraumatic ictal-like epileptiform discharges and epileptogenesis. METHODS Acute hippocampal slices were used as a model of severe traumatic brain injury and posttraumatic epileptogenesis. Hippocampal slices were then incubated for 3 weeks. After a 1-week latent period, slice cultures developed chronic spontaneous ictal-like discharges. The anticonvulsant and anti-epileptogenic efficacy of bumetanide, phenobarbital, and the combination of these drugs was studied. RESULTS Bumetanide reduced the frequency and power of early posttraumatic ictal-like discharges in vitro and enhanced the anticonvulsant efficacy of phenobarbital. Continuous 2-3 weeks administration of bumetanide as well as phenobarbital in combination with bumetanide failed to prevent posttraumatic ictal-like discharges and epileptogenesis. CONCLUSIONS Our data demonstrate a persistent contribution of NKCC1 cotransport in posttraumatic ictal-like activity, presumably as a consequence of chronic alterations in neuronal chloride homeostasis and GABA-mediated inhibition. New strategies for more effective reduction in posttraumatic and seizure-induced [Cl(-)]i accumulation could provide the basis for effective treatments for posttraumatic epileptogenesis and the resultant seizures.
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Affiliation(s)
- Volodymyr Dzhala
- Neurology Department, Massachusetts General Hospital, Boston, MA, USA
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136
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Khazipov R, Valeeva G, Khalilov I. Depolarizing GABA and developmental epilepsies. CNS Neurosci Ther 2014; 21:83-91. [PMID: 25438879 DOI: 10.1111/cns.12353] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Revised: 10/14/2014] [Accepted: 10/20/2014] [Indexed: 12/22/2022] Open
Abstract
Early in development, GABA, which is the main inhibitory neurotransmitter in adult brain, depolarizes immature neurons and exerts dual--excitatory and shunting/inhibitory--effects in the developing neuronal networks. The present review discusses some general questions, including the properties of excitation at depolarizing GABAergic synapse and shunting inhibition by depolarizing GABA; technical issues in exploration of depolarizing GABA using various techniques and preparations, including the developmental aspects of traumatic injury and what is known (or rather unknown) on the actions of GABA in vivo; complex roles of depolarizing GABA in developmental epilepsies, including a contribution of depolarizing GABA to enhanced excitability in the immature networks, caused by repetitive seizures accumulation of intracellular chloride concentration that increases excitatory GABA power and its synchronizing proconvulsive effects, and correction of chloride homeostasis as a potential strategy to treat neonatal seizures.
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Affiliation(s)
- Roustem Khazipov
- INMED-INSERM U901, Marseille, France; Aix-Marseille University, Marseille, France; Laboratory of Neurobiology, Kazan Federal University, Kazan, Russia
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137
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Kaila K, Price TJ, Payne JA, Puskarjov M, Voipio J. Cation-chloride cotransporters in neuronal development, plasticity and disease. Nat Rev Neurosci 2014; 15:637-54. [PMID: 25234263 DOI: 10.1038/nrn3819] [Citation(s) in RCA: 500] [Impact Index Per Article: 50.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Electrical activity in neurons requires a seamless functional coupling between plasmalemmal ion channels and ion transporters. Although ion channels have been studied intensively for several decades, research on ion transporters is in its infancy. In recent years, it has become evident that one family of ion transporters, cation-chloride cotransporters (CCCs), and in particular K(+)-Cl(-) cotransporter 2 (KCC2), have seminal roles in shaping GABAergic signalling and neuronal connectivity. Studying the functions of these transporters may lead to major paradigm shifts in our understanding of the mechanisms underlying brain development and plasticity in health and disease.
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Affiliation(s)
- Kai Kaila
- 1] Department of Biosciences, University of Helsinki, 00014 Helsinki, Finland. [2] Neuroscience Center, University of Helsinki, 00014 Helsinki, Finland
| | - Theodore J Price
- University of Texas at Dallas, School of Behavior and Brain Sciences, Dallas, Texas 75093, USA
| | - John A Payne
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, California 95616, USA
| | - Martin Puskarjov
- 1] Department of Biosciences, University of Helsinki, 00014 Helsinki, Finland. [2] Neuroscience Center, University of Helsinki, 00014 Helsinki, Finland
| | - Juha Voipio
- Department of Biosciences, University of Helsinki, 00014 Helsinki, Finland
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138
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Murphey DK, Herman AM, Arenkiel BR. Dissecting inhibitory brain circuits with genetically-targeted technologies. Front Neural Circuits 2014; 8:124. [PMID: 25368555 PMCID: PMC4201106 DOI: 10.3389/fncir.2014.00124] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 09/22/2014] [Indexed: 12/14/2022] Open
Abstract
The evolution of genetically targeted tools has begun to allow us to dissect anatomically and functionally heterogeneous interneurons, and to probe circuit function from synapses to behavior. Over the last decade, these tools have been used widely to visualize neurons in a cell type-specific manner, and engage them to activate and inactivate with exquisite precision. In this process, we have expanded our understanding of interneuron diversity, their functional connectivity, and how selective inhibitory circuits contribute to behavior. Here we discuss the relative assets of genetically encoded fluorescent proteins (FPs), viral tracing methods, optogenetics, chemical genetics, and biosensors in the study of inhibitory interneurons and their respective circuits.
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Affiliation(s)
- Dona K Murphey
- Department of Neurology, Baylor College of Medicine Houston, TX, USA
| | - Alexander M Herman
- Program in Developmental Biology, Baylor College of Medicine Houston, TX, USA
| | - Benjamin R Arenkiel
- Program in Developmental Biology, Baylor College of Medicine Houston, TX, USA ; Department of Molecular and Human Genetics, Baylor College of Medicine Houston, TX, USA ; Department of Neuroscience, Baylor College of Medicine Houston, TX, USA ; Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital Houston, TX, USA
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139
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Delpire E, Staley KJ. Novel determinants of the neuronal Cl(-) concentration. J Physiol 2014; 592:4099-114. [PMID: 25107928 PMCID: PMC4215762 DOI: 10.1113/jphysiol.2014.275529] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Accepted: 08/01/2014] [Indexed: 12/11/2022] Open
Abstract
It is now a well-accepted view that cation-driven Cl(-) transporters in neurons are involved in determining the intracellular Cl(-) concentration. In the present review, we propose that additional factors, which are often overlooked, contribute substantially to the Cl(-) gradient across neuronal membranes. After briefly discussing the data supporting and opposing the role of cation-chloride cotransporters in regulating Cl(-), we examine the participation of the following factors in the formation of the transmembrane Cl(-) gradient: (i) fixed 'Donnan' charges inside and outside the cell; (ii) the properties of water (free vs. bound); and (iii) water transport through the cotransporters. We demonstrate a steep relationship between intracellular Cl(-) and the concentration of fixed negative charges on macromolecules. We show that in the absence of water transport through the K(+)-Cl(-) cotransporter, a large osmotic gradient builds at concentrations below or above a set value of 'Donnan' charges, and show that at any value of these fixed charges, the reversal potential for Cl(-) equates that of K(+). When the movement of water across the membrane is a source of free energy, it is sufficient to modify the movement of Cl(-) through the cotransporter. In this scenario, the reversal potential for Cl(-) does not closely follow that of K(+). Furthermore, our simulations demonstrate that small differences in the availability of freely diffusible water between inside and outside the cell greatly affect the Cl(-) reversal potential, particularly when osmolar transmembrane gradients are minimized, for example by idiogenic osmoles. We also establish that the presence of extracellular charges has little effect on the chloride reversal potential, but greatly affects the effective inhibitory conductance for Cl(-). In conclusion, our theoretical analysis of the presence of fixed anionic charges and water bound on macromolecules inside and outside the cell greatly impacts both Cl(-) gradient and Cl(-) conductance across neuronal membranes.
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Affiliation(s)
- Eric Delpire
- Department of Anaesthesiology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Kevin J Staley
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
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140
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Glykys J, Dzhala V, Egawa K, Balena T, Saponjian Y, Kuchibhotla KV, Bacskai BJ, Kahle KT, Zeuthen T, Staley KJ. Response to comments on "Local impermeant anions establish the neuronal chloride concentration". Science 2014; 345:1130. [PMID: 25190789 DOI: 10.1126/science.1253146] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
We appreciate the interest in our paper and the opportunity to clarify theoretical and technical aspects describing the influence of Donnan equilibria on neuronal chloride ion (Cl(-)) distributions.
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Affiliation(s)
- J Glykys
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - V Dzhala
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - K Egawa
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - T Balena
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Y Saponjian
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - K V Kuchibhotla
- New York University School of Medicine, Skirball Institute for Biomolecular Medicine, New York, NY, USA
| | - B J Bacskai
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - K T Kahle
- Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - T Zeuthen
- Department of Cellular and Molecular Medicine, University of Copenhagen, Denmark
| | - K J Staley
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
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141
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Voipio J, Boron WF, Jones SW, Hopfer U, Payne JA, Kaila K. Comment on "Local impermeant anions establish the neuronal chloride concentration". Science 2014; 345:1130. [DOI: 10.1126/science.1252978] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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142
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Luhmann HJ, Kirischuk S, Kilb W. Comment on "Local impermeant anions establish the neuronal chloride concentration". Science 2014; 345:1130. [DOI: 10.1126/science.1255337] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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143
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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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144
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The GABA excitatory/inhibitory developmental sequence: a personal journey. Neuroscience 2014; 279:187-219. [PMID: 25168736 DOI: 10.1016/j.neuroscience.2014.08.001] [Citation(s) in RCA: 194] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Revised: 07/17/2014] [Accepted: 08/01/2014] [Indexed: 12/11/2022]
Abstract
The developing brain is talkative but its language is not that of the adult. Most if not all voltage and transmitter-gated ionic currents follow a developmental sequence and network-driven patterns differ in immature and adult brains. This is best illustrated in studies engaged almost three decades ago in which we observed elevated intracellular chloride (Cl(-))i levels and excitatory GABA early during development and a perinatal excitatory/inhibitory shift. This sequence is observed in a wide range of brain structures and animal species suggesting that it has been conserved throughout evolution. It is mediated primarily by a developmentally regulated expression of the NKCC1 and KCC2 chloride importer and exporter respectively. The GABAergic depolarization acts in synergy with N-methyl-d-aspartate (NMDA) receptor-mediated and voltage-gated calcium currents to enhance intracellular calcium exerting trophic effects on neuritic growth, migration and synapse formation. These sequences can be deviated in utero by genetic or environmental insults leading to a persistence of immature features in the adult brain. This "neuroarcheology" concept paves the way to novel therapeutic perspectives based on the use of drugs that block immature but not adult currents. This is illustrated notably with the return to immature high levels of chloride and excitatory actions of GABA observed in many pathological conditions. This is due to the fact that in the immature brain a down regulation of KCC2 and an up regulation of NKCC1 are seen. Here, I present a personal history of how an unexpected observation led to novel concepts in developmental neurobiology and putative treatments of autism and other developmental disorders. Being a personal account, this review is neither exhaustive nor provides an update of this topic with all the studies that have contributed to this evolution. We all rely on previous inventors to allow science to advance. Here, I present a personal summary of this topic primarily to illustrate why we often fail to comprehend the implications of our own observations. They remind us - and policy deciders - why Science cannot be programed, requiring time, and risky investigations that raise interesting questions before being translated from bench to bed. Discoveries are always on sideways, never on highways.
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145
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Intracellular activities related to in vitro hippocampal sharp waves are altered in CA3 pyramidal neurons of aged mice. Neuroscience 2014; 277:474-85. [PMID: 25088916 DOI: 10.1016/j.neuroscience.2014.07.048] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Revised: 07/09/2014] [Accepted: 07/09/2014] [Indexed: 01/11/2023]
Abstract
Pyramidal neurons in the hippocampal CA3 area interconnect intensively via recurrent axonal collaterals, and such CA3-to-CA3 recurrent circuitry plays important roles in the generation of hippocampal network activities. In particular, the CA3 circuitry is able to generate spontaneous sharp waves (SPWs) when examined in vitro. These in vitro SPWs are thought to result from the network activity of GABAergic inhibitory interneurons as SPW-correlating intracellular activities are featured with strong IPSPs in pyramidal neurons and EPSPs or spikes in GABAergic interneurons. In view of accumulating evidence indicating a decrease in subgroups of hippocampal GABAergic interneurons in aged animals, we test the hypothesis that the intracellular activities related to in vitro SPWs are altered in CA3 pyramidal neurons of aged mice. Hippocampal slices were prepared from adult and aged C57 black mice (ages 3-6 and 24-28months respectively). Population and single-cell activities were examined via extracellular and whole-cell patch-clamp recordings. CA3 SPW frequencies were not significantly different between the slices of adult and aged mice but SPW-correlating intracellular activities featured weaker IPSC components in aged CA3 pyramidal neurons compared to adult neurons. It was unlikely that this latter phenomenon was due to general impairments of GABAergic synapses in the aged CA3 circuitry as evoked IPSC responses and pharmacologically isolated IPSCs were observed in aged CA3 pyramidal neurons. In addition, aged CA3 pyramidal neurons displayed more positive resting potentials and had a higher propensity of burst firing than adult neurons. We postulate that alterations of GABAergic network activity may explain the reduced IPCS contributions to in vitro SPWs in aged CA3 pyramidal neurons. Overall, our present observations are supportive of the notion that excitability of hippocampal CA3 circuitry is increased in aged mice.
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146
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Xie R, Manis PB. GABAergic and glycinergic inhibitory synaptic transmission in the ventral cochlear nucleus studied in VGAT channelrhodopsin-2 mice. Front Neural Circuits 2014; 8:84. [PMID: 25104925 PMCID: PMC4109614 DOI: 10.3389/fncir.2014.00084] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Accepted: 07/03/2014] [Indexed: 11/27/2022] Open
Abstract
Both glycine and GABA mediate inhibitory synaptic transmission in the ventral cochlear nucleus (VCN). In mice, the time course of glycinergic inhibition is slow in bushy cells and fast in multipolar (stellate) cells, and is proposed to contribute to the processing of temporal cues in both cell types. Much less is known about GABAergic synaptic transmission in this circuit. Electrical stimulation of the auditory nerve or the tuberculoventral pathway evokes little GABAergic synaptic current in brain slice preparations, and spontaneous GABAergic miniature synaptic currents occur infrequently. To investigate synaptic currents carried by GABA receptors in bushy and multipolar cells, we used transgenic mice in which channelrhodopsin-2 and EYFP is driven by the vesicular GABA transporter (VGAT-ChR2-EYFP) and is expressed in both GABAergic and glycinergic neurons. Light stimulation evoked action potentials in EYFP-expressing presynaptic cells, and evoked inhibitory postsynaptic potentials (IPSPs) in non-expressing bushy and planar multipolar cells. Less than 10% of the IPSP amplitude in bushy cells arose from GABAergic synapses, whereas 40% of the IPSP in multipolar neurons was GABAergic. In voltage clamp, glycinergic IPSCs were significantly slower in bushy neurons than in multipolar neurons, whereas there was little difference in the kinetics of the GABAergic IPSCs between two cell types. During prolonged stimulation, the ratio of steady state vs. peak IPSC amplitude was significantly lower for glycinergic IPSCs. Surprisingly, the reversal potentials of GABAergic IPSCs were negative to those of glycinergic IPSCs in both bushy and multipolar neurons. In the absence of receptor blockers, repetitive light stimulation was only able to effectively evoke IPSCs up to 20 Hz in both bushy and multipolar neurons. We conclude that local GABAergic release within the VCN can differentially influence bushy and multipolar cells.
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Affiliation(s)
- Ruili Xie
- Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill Chapel Hill, NC, USA
| | - Paul B Manis
- Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill Chapel Hill, NC, USA ; Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill Chapel Hill, NC, USA
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147
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Gonzalez-Burgos G, Miyamae T, Pafundo DE, Yoshino H, Rotaru DC, Hoftman G, Datta D, Zhang Y, Hammond M, Sampson AR, Fish KN, Ermentrout GB, Lewis DA. Functional Maturation of GABA Synapses During Postnatal Development of the Monkey Dorsolateral Prefrontal Cortex. Cereb Cortex 2014; 25:4076-93. [PMID: 24904071 DOI: 10.1093/cercor/bhu122] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Development of inhibition onto pyramidal cells may be crucial for the emergence of cortical network activity, including gamma oscillations. In primate dorsolateral prefrontal cortex (DLPFC), inhibitory synaptogenesis starts in utero and inhibitory synapse density reaches adult levels before birth. However, in DLPFC, the expression levels of γ-aminobutyric acid (GABA) synapse-related gene products changes markedly during development until young adult age, suggesting a highly protracted maturation of GABA synapse function. Therefore, we examined the development of GABA synapses by recording GABAAR-mediated inhibitory postsynaptic currents (GABAAR-IPSCs) from pyramidal cells in the DLPFC of neonatal, prepubertal, peripubertal, and adult macaque monkeys. We found that the decay of GABAAR-IPSCs, possibly including those from parvalbumin-positive GABA neurons, shortened by prepubertal age, while their amplitude increased until the peripubertal period. Interestingly, both GABAAR-mediated quantal response size, estimated by miniature GABAAR-IPSCs, and the density of GABAAR synaptic appositions, measured with immunofluorescence microscopy, were stable with age. Simulations in a computational model network with constant GABA synapse density showed that the developmental changes in GABAAR-IPSC properties had a significant impact on oscillatory activity and predicted that, whereas DLPFC circuits can generate gamma frequency oscillations by prepubertal age, mature levels of gamma band power are attained at late stages of development.
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Affiliation(s)
- Guillermo Gonzalez-Burgos
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Takeaki Miyamae
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Diego E Pafundo
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA Current address: Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, USA
| | - Hiroki Yoshino
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA Current address: Department of Psychiatry, Nara Medical University, Japan
| | - Diana C Rotaru
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA Current address: Department of Integrative Neurophysiology, Vrije Universiteit, Amsterdam, Netherlands
| | - Gil Hoftman
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Dibyadeep Datta
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Yun Zhang
- Department of Statistics, University of Pittsburgh, Pittsburgh, PA, USA
| | - Mahjub Hammond
- Department of Mathematics, University of Pittsburgh, Pittsburgh, PA, USA
| | - Allan R Sampson
- Department of Statistics, University of Pittsburgh, Pittsburgh, PA, USA
| | - Kenneth N Fish
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - G Bard Ermentrout
- Department of Mathematics, University of Pittsburgh, Pittsburgh, PA, USA
| | - David A Lewis
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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148
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Cho CH. Star players sidelined in chloride homeostasis in neurons. Front Cell Neurosci 2014; 8:114. [PMID: 24795569 PMCID: PMC4006059 DOI: 10.3389/fncel.2014.00114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Accepted: 04/07/2014] [Indexed: 11/24/2022] Open
Affiliation(s)
- Chang-Hoon Cho
- Graduate School of Life Science, Institute of Biotechnology, Korea University Seoul, Korea
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149
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Lindsly C, Gonzalez-Islas C, Wenner P. Activity blockade and GABAA receptor blockade produce synaptic scaling through chloride accumulation in embryonic spinal motoneurons and interneurons. PLoS One 2014; 9:e94559. [PMID: 24733046 PMCID: PMC3986094 DOI: 10.1371/journal.pone.0094559] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Accepted: 03/18/2014] [Indexed: 12/03/2022] Open
Abstract
Synaptic scaling represents a process whereby the distribution of a cell's synaptic strengths are altered by a multiplicative scaling factor. Scaling is thought to be a compensatory response that homeostatically controls spiking activity levels in the cell or network. Previously, we observed GABAergic synaptic scaling in embryonic spinal motoneurons following in vivo blockade of either spiking activity or GABAA receptors (GABAARs). We had determined that activity blockade triggered upward GABAergic scaling through chloride accumulation, thus increasing the driving force for these currents. To determine whether chloride accumulation also underlies GABAergic scaling following GABAAR blockade we have developed a new technique. We expressed a genetically encoded chloride-indicator, Clomeleon, in the embryonic chick spinal cord, which provides a non-invasive fast measure of intracellular chloride. Using this technique we now show that chloride accumulation underlies GABAergic scaling following blockade of either spiking activity or the GABAAR. The finding that GABAAR blockade and activity blockade trigger scaling via a common mechanism supports our hypothesis that activity blockade reduces GABAAR activation, which triggers synaptic scaling. In addition, Clomeleon imaging demonstrated the time course and widespread nature of GABAergic scaling through chloride accumulation, as it was also observed in spinal interneurons. This suggests that homeostatic scaling via chloride accumulation is a common feature in many neuronal classes within the embryonic spinal cord and opens the possibility that this process may occur throughout the nervous system at early stages of development.
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Affiliation(s)
- Casie Lindsly
- Physiology Department, Emory University, School of Medicine, Atlanta, Georgia, United States of America
| | - Carlos Gonzalez-Islas
- Physiology Department, Emory University, School of Medicine, Atlanta, Georgia, United States of America
| | - Peter Wenner
- Physiology Department, Emory University, School of Medicine, Atlanta, Georgia, United States of America
- * E-mail:
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150
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Adler EM. Of pumps, protons, chloride gradients, and microvesicles at the immunological synapse. ACTA ACUST UNITED AC 2014; 143:417-8. [PMID: 24688015 PMCID: PMC3971656 DOI: 10.1085/jgp.201411196] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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