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Wang Y, Chen Y, Chen L, Herron BJ, Chen XY, Wolpaw JR. Motor learning changes the axon initial segment of the spinal motoneuron. J Physiol 2024; 602:2107-2126. [PMID: 38568869 PMCID: PMC11196014 DOI: 10.1113/jp283875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Accepted: 03/12/2024] [Indexed: 04/05/2024] Open
Abstract
We are studying the mechanisms of H-reflex operant conditioning, a simple form of learning. Modelling studies in the literature and our previous data suggested that changes in the axon initial segment (AIS) might contribute. To explore this, we used blinded quantitative histological and immunohistochemical methods to study in adult rats the impact of H-reflex conditioning on the AIS of the spinal motoneuron that produces the reflex. Successful, but not unsuccessful, H-reflex up-conditioning was associated with greater AIS length and distance from soma; greater length correlated with greater H-reflex increase. Modelling studies in the literature suggest that these increases may increase motoneuron excitability, supporting the hypothesis that they may contribute to H-reflex increase. Up-conditioning did not affect AIS ankyrin G (AnkG) immunoreactivity (IR), p-p38 protein kinase IR, or GABAergic terminals. Successful, but not unsuccessful, H-reflex down-conditioning was associated with more GABAergic terminals on the AIS, weaker AnkG-IR, and stronger p-p38-IR. More GABAergic terminals and weaker AnkG-IR correlated with greater H-reflex decrease. These changes might potentially contribute to the positive shift in motoneuron firing threshold underlying H-reflex decrease; they are consistent with modelling suggesting that sodium channel change may be responsible. H-reflex down-conditioning did not affect AIS dimensions. This evidence that AIS plasticity is associated with and might contribute to H-reflex conditioning adds to evidence that motor learning involves both spinal and brain plasticity, and both neuronal and synaptic plasticity. AIS properties of spinal motoneurons are likely to reflect the combined influence of all the motor skills that share these motoneurons. KEY POINTS: Neuronal action potentials normally begin in the axon initial segment (AIS). AIS plasticity affects neuronal excitability in development and disease. Whether it does so in learning is unknown. Operant conditioning of a spinal reflex, a simple learning model, changes the rat spinal motoneuron AIS. Successful, but not unsuccessful, H-reflex up-conditioning is associated with greater AIS length and distance from soma. Successful, but not unsuccessful, down-conditioning is associated with more AIS GABAergic terminals, less ankyrin G, and more p-p38 protein kinase. The associations between AIS plasticity and successful H-reflex conditioning are consistent with those between AIS plasticity and functional changes in development and disease, and with those predicted by modelling studies in the literature. Motor learning changes neurons and synapses in spinal cord and brain. Because spinal motoneurons are the final common pathway for behaviour, their AIS properties probably reflect the combined impact of all the behaviours that use these motoneurons.
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Affiliation(s)
- Yu Wang
- National Center for Adaptive Neurotechnologies, Albany Stratton VA Medical Center, 113 Holland Ave, Albany, NY 12208
| | - Yi Chen
- National Center for Adaptive Neurotechnologies, Albany Stratton VA Medical Center, 113 Holland Ave, Albany, NY 12208
| | - Lu Chen
- National Center for Adaptive Neurotechnologies, Albany Stratton VA Medical Center, 113 Holland Ave, Albany, NY 12208
| | - Bruce J. Herron
- Wadsworth Center, New York State Department of Health, 150 New Scotland Ave, Albany, NY 12208
- Department of Biomedical Sciences, School of Public Health, State University of New York, Albany, New York
| | - Xiang Yang Chen
- National Center for Adaptive Neurotechnologies, Albany Stratton VA Medical Center, 113 Holland Ave, Albany, NY 12208
- Department of Biomedical Sciences, School of Public Health, State University of New York, Albany, New York
| | - Jonathan R. Wolpaw
- National Center for Adaptive Neurotechnologies, Albany Stratton VA Medical Center, 113 Holland Ave, Albany, NY 12208
- Department of Biomedical Sciences, School of Public Health, State University of New York, Albany, New York
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2
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Shang Z, Huang J, Liu N, Zhang X. Bi-directional Control of Synaptic Input Summation and Spike Generation by GABAergic Inputs at the Axon Initial Segment. Neurosci Bull 2023; 39:1-13. [PMID: 35639277 PMCID: PMC9849666 DOI: 10.1007/s12264-022-00887-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 03/03/2022] [Indexed: 01/22/2023] Open
Abstract
Differing from other subtypes of inhibitory interneuron, chandelier or axo-axonic cells form depolarizing GABAergic synapses exclusively onto the axon initial segment (AIS) of targeted pyramidal cells (PCs). However, the debate whether these AIS-GABAergic inputs produce excitation or inhibition in neuronal processing is not resolved. Using realistic NEURON modeling and electrophysiological recording of cortical layer-5 PCs, we quantitatively demonstrate that the onset-timing of AIS-GABAergic input, relative to dendritic excitatory glutamatergic inputs, determines its bi-directional regulation of the efficacy of synaptic integration and spike generation in a PC. More specifically, AIS-GABAergic inputs promote the boosting effect of voltage-activated Na+ channels on summed synaptic excitation when they precede glutamatergic inputs by >15 ms, while for nearly concurrent excitatory inputs, they primarily produce a shunting inhibition at the AIS. Thus, our findings offer an integrative mechanism by which AIS-targeting interneurons exert sophisticated regulation of the input-output function in targeted PCs.
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Affiliation(s)
- Ziwei Shang
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, Beijing Normal University, Beijing, 100875, China
| | - Junhao Huang
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, Beijing Normal University, Beijing, 100875, China
| | - Nan Liu
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, Beijing Normal University, Beijing, 100875, China
| | - Xiaohui Zhang
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, Beijing Normal University, Beijing, 100875, China.
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3
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Ostos S, Aparicio G, Fernaud-Espinosa I, DeFelipe J, Muñoz A. Quantitative analysis of the GABAergic innervation of the soma and axon initial segment of pyramidal cells in the human and mouse neocortex. Cereb Cortex 2022; 33:3882-3909. [PMID: 36058205 DOI: 10.1093/cercor/bhac314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 07/16/2022] [Accepted: 07/17/2022] [Indexed: 11/13/2022] Open
Abstract
Perisomatic GABAergic innervation in the cerebral cortex is carried out mostly by basket and chandelier cells, which differentially participate in the control of pyramidal cell action potential output and synchronization. These cells establish multiple synapses with the cell body (and proximal dendrites) and the axon initial segment (AIS) of pyramidal neurons, respectively. Using multiple immunofluorescence, confocal microscopy and 3D quantification techniques, we have estimated the number and density of GABAergic boutons on the cell body and AIS of pyramidal neurons located through cortical layers of the human and mouse neocortex. The results revealed, in both species, that there is clear variability across layers regarding the density and number of perisomatic GABAergic boutons. We found a positive linear correlation between the surface area of the soma, or the AIS, and the number of GABAergic terminals in apposition to these 2 neuronal domains. Furthermore, the density of perisomatic GABAergic boutons was higher in the human cortex than in the mouse. These results suggest a selectivity for the GABAergic innervation of the cell body and AIS that might be related to the different functional attributes of the microcircuits in which neurons from different layers are involved in both human and mouse.
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Affiliation(s)
- Sandra Ostos
- Departamento de Neurobiología Funcional y de Sistemas, Instituto Cajal (CSIC), Avenida Doctor Arce 37, 28002, Madrid, Spain.,Laboratorio Cajal de Circuitos Corticales (CTB), Universidad Politécnica de Madrid, Campus de Montegancedo, 28223, Pozuelo de Alarcón, Madrid, Spain
| | - Guillermo Aparicio
- Departamento de Neurobiología Funcional y de Sistemas, Instituto Cajal (CSIC), Avenida Doctor Arce 37, 28002, Madrid, Spain.,Laboratorio Cajal de Circuitos Corticales (CTB), Universidad Politécnica de Madrid, Campus de Montegancedo, 28223, Pozuelo de Alarcón, Madrid, Spain
| | - Isabel Fernaud-Espinosa
- Departamento de Neurobiología Funcional y de Sistemas, Instituto Cajal (CSIC), Avenida Doctor Arce 37, 28002, Madrid, Spain.,Laboratorio Cajal de Circuitos Corticales (CTB), Universidad Politécnica de Madrid, Campus de Montegancedo, 28223, Pozuelo de Alarcón, Madrid, Spain
| | - Javier DeFelipe
- Departamento de Neurobiología Funcional y de Sistemas, Instituto Cajal (CSIC), Avenida Doctor Arce 37, 28002, Madrid, Spain.,Laboratorio Cajal de Circuitos Corticales (CTB), Universidad Politécnica de Madrid, Campus de Montegancedo, 28223, Pozuelo de Alarcón, Madrid, Spain.,CIBERNED, Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas, Avenida Monforte de Lemos, 3-5, 28029 Madrid, Spain
| | - Alberto Muñoz
- Departamento de Neurobiología Funcional y de Sistemas, Instituto Cajal (CSIC), Avenida Doctor Arce 37, 28002, Madrid, Spain.,Laboratorio Cajal de Circuitos Corticales (CTB), Universidad Politécnica de Madrid, Campus de Montegancedo, 28223, Pozuelo de Alarcón, Madrid, Spain.,Departamento de Biología Celular, Universidad Complutense, José Antonio Novais 12, 28040 Madrid, Spain
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4
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Virtanen MA, Uvarov P, Hübner CA, Kaila K. NKCC1, an Elusive Molecular Target in Brain Development: Making Sense of the Existing Data. Cells 2020; 9:cells9122607. [PMID: 33291778 PMCID: PMC7761970 DOI: 10.3390/cells9122607] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 12/01/2020] [Accepted: 12/03/2020] [Indexed: 12/14/2022] Open
Abstract
Ionotropic GABA transmission is mediated by anion (mainly Cl−)-permeable GABAA receptors (GABAARs). In immature neurons, GABA exerts depolarizing and sometimes functionally excitatory actions, based on active uptake of Cl− by the Na-K-2Cl cotransporter NKCC1. While functional evidence firmly shows NKCC1-mediated ion transport in immature and diseased neurons, molecular detection of NKCC1 in the brain has turned out to be extremely difficult. In this review, we describe the highly inconsistent data that are available on the cell type-specific expression patterns of the NKCC1 mRNA and protein in the CNS. We discuss the major technical caveats, including a lack of knock-out-controlled immunohistochemistry in the forebrain, possible effects of alternative splicing on the binding of antibodies and RNA probes, and the wide expression of NKCC1 in different cell types, which make whole-tissue analyses of NKCC1 useless for studying its neuronal expression. We also review novel single-cell RNAseq data showing that most of the NKCC1 in the adult CNS may, in fact, be expressed in non-neuronal cells, especially in glia. As future directions, we suggest single-cell NKCC1 mRNA and protein analyses and the use of genetically tagged endogenous proteins or systematically designed novel antibodies, together with proper knock-out controls, for the visualization of endogenous NKCC1 in distinct brain cell types and their subcellular compartments.
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Affiliation(s)
- Mari A. Virtanen
- Molecular and Integrative Biosciences, University of Helsinki, 00014 Helsinki, Finland; (M.A.V.); (P.U.)
- Neuroscience Center, Helsinki Institute of Life Science, University of Helsinki, 00014 Helsinki, Finland
| | - Pavel Uvarov
- Molecular and Integrative Biosciences, University of Helsinki, 00014 Helsinki, Finland; (M.A.V.); (P.U.)
- Neuroscience Center, Helsinki Institute of Life Science, University of Helsinki, 00014 Helsinki, Finland
| | - Christian A. Hübner
- Institute of Human Genetics, Jena University Hospital, Friedrich Schiller Universität, 07747 Jena, Germany;
| | - Kai Kaila
- Molecular and Integrative Biosciences, University of Helsinki, 00014 Helsinki, Finland; (M.A.V.); (P.U.)
- Neuroscience Center, Helsinki Institute of Life Science, University of Helsinki, 00014 Helsinki, Finland
- Correspondence: ; Tel.: +358-407256759
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Maturation Dynamics of the Axon Initial Segment (AIS) of Newborn Dentate Granule Cells in Young Adult C57BL/6J Mice. J Neurosci 2019; 39:1605-1620. [PMID: 30651327 DOI: 10.1523/jneurosci.2253-18.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Revised: 12/27/2018] [Accepted: 01/04/2019] [Indexed: 01/07/2023] Open
Abstract
Newborn dentate granule cells (DGCs) are generated in the hippocampal dentate gyrus (DG) of rodents through a process called adult hippocampal neurogenesis, which is subjected to tight intrinsic and extrinsic regulation. The use of retroviruses encoding fluorescent proteins has allowed the characterization of the maturation dynamics of newborn DGCs, including their morphological development and the establishment and maturation of their afferent and efferent synaptic connections. However, the study of a crucial cellular compartment of these cells, namely, the axon initial segment (AIS), has remained unexplored to date. The AIS is not only the site of action potential initiation, but it also has a unique molecular identity that makes it one of the master regulators of neural plasticity and excitability. Here we examined the dynamics of AIS formation in newborn DGCs of young female adult C57BL/6J mice in vivo Our data reveal notable changes in AIS length and thickness throughout cell maturation under physiological conditions and show that the most remarkable structural changes coincide with periods of intense morphological and functional remodeling. Moreover, we demonstrate that AIS development can be modulated extrinsically by both neuroprotective (environmental enrichment) and detrimental (lipopolysaccharide from Escherichia coli) stimuli.SIGNIFICANCE STATEMENT The hippocampal dentate gyrus (DG) of rodents generates newborn dentate granule cells (DGCs) throughout life. This process, named adult hippocampal neurogenesis, confers a unique degree of plasticity to the hippocampal circuit, and it is crucial for learning and memory. Here we studied, for the first time, the formation of a key cellular compartment of newborn DGCs, namely, the axon initial segment (AIS) in vivo Our data reveal remarkable AIS structural remodeling throughout the maturation of these cells under physiological conditions. Moreover, AIS development can be modulated extrinsically by both neuroprotective (environmental enrichment) and detrimental (lipopolysaccharide from Escherichia coli) stimuli.
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Magloire V, Mercier MS, Kullmann DM, Pavlov I. GABAergic Interneurons in Seizures: Investigating Causality With Optogenetics. Neuroscientist 2018; 25:344-358. [PMID: 30317911 PMCID: PMC6745605 DOI: 10.1177/1073858418805002] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Seizures are complex pathological network events characterized by excessive and
hypersynchronized activity of neurons, including a highly diverse population of
GABAergic interneurons. Although the primary function of inhibitory interneurons
under normal conditions is to restrain excitation in the brain, this system
appears to fail intermittently, allowing runaway excitation. Recent developments
in optogenetics, combined with genetic tools and advanced electrophysiological
and imaging techniques, allow us for the first time to assess the causal roles
of identified cell-types in network dynamics. While these methods have greatly
increased our understanding of cortical microcircuits in epilepsy, the roles
played by individual GABAergic cell-types in controlling ictogenesis remain
incompletely resolved. Indeed, the ability of interneurons to suppress epileptic
discharges varies across different subtypes, and an accumulating body of
evidence paradoxically implicates some interneuron subtypes in the initiation
and maintenance of epileptiform activity. Here, we bring together findings from
this growing field and discuss what can be inferred regarding the causal role of
different GABAergic cell-types in seizures.
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Affiliation(s)
- Vincent Magloire
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, UCL, London, UK
| | - Marion S Mercier
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, UCL, London, UK
| | - Dimitri M Kullmann
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, UCL, London, UK
| | - Ivan Pavlov
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, UCL, London, UK
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7
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Shao LR, Wang G, Stafstrom CE. The Glycolytic Metabolite, Fructose-1,6-bisphosphate, Blocks Epileptiform Bursts by Attenuating Voltage-Activated Calcium Currents in Hippocampal Slices. Front Cell Neurosci 2018; 12:168. [PMID: 29962940 PMCID: PMC6013557 DOI: 10.3389/fncel.2018.00168] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 05/30/2018] [Indexed: 01/24/2023] Open
Abstract
Manipulation of metabolic pathways (e.g., ketogenic diet (KD), glycolytic inhibition) alters neural excitability and represents a novel strategy for treatment of drug-refractory seizures. We have previously shown that inhibition of glycolysis suppresses epileptiform activity in hippocampal slices. In the present study, we aimed to examine the role of a “branching” metabolic pathway stemming off glycolysis (i.e., the pentose-phosphate pathway, PPP) in regulating seizure activity, by using a potent PPP stimulator and glycolytic intermediate, fructose-1,6-bisphosphate (F1,6BP). Employing electrophysiological approaches, we investigated the action of F1,6BP on epileptiform population bursts, intrinsic neuronal firing, glutamatergic and GABAergic synaptic transmission and voltage-activated calcium currents (ICa) in the CA3 area of hippocampal slices. Bath application of F1,6BP (2.5–5 mM) blocked epileptiform population bursts induced in Mg2+-free medium containing 4-aminopyridine, in ~2/3 of the slices. The blockade occurred relatively rapidly (~4 min), suggesting an extracellular mechanism. However, F1,6BP did not block spontaneous intrinsic firing of the CA3 neurons (when synaptic transmission was eliminated with DNQX, AP-5 and SR95531), nor did it significantly reduce AMPA or NMDA receptor-mediated excitatory postsynaptic currents (EPSCAMPA and EPSCNMDA). In contrast, F1,6BP caused moderate reduction (~50%) in GABAA receptor-mediated current, suggesting it affects excitatory and inhibitory synapses differently. Finally and unexpectedly, F1,6BP consistently attenuated ICa by ~40% without altering channel activation or inactivation kinetics, which may explain its anticonvulsant action, at least in this in vitro seizure model. Consistent with these results, epileptiform population bursts in CA3 were readily blocked by the nonspecific Ca2+ channel blocker, CdCl2 (20 μM), suggesting that these bursts are calcium dependent. Altogether, these data demonstrate that the glycolytic metabolite, F1,6BP, blocks epileptiform activity via a previously unrecognized extracellular effect on ICa, which provides new insight into the metabolic control of neural excitability.
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Affiliation(s)
- Li-Rong Shao
- Division of Pediatric Neurology, Department of Neurology, School of Medicine, Johns Hopkins University, Baltimore, MD, United States
| | - Guangxin Wang
- Department of Medicine, Qilu Children's Hospital, Shandong University, Jinan, China
| | - Carl E Stafstrom
- Division of Pediatric Neurology, Department of Neurology, School of Medicine, Johns Hopkins University, Baltimore, MD, United States
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8
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Selten M, van Bokhoven H, Nadif Kasri N. Inhibitory control of the excitatory/inhibitory balance in psychiatric disorders. F1000Res 2018; 7:23. [PMID: 29375819 PMCID: PMC5760969 DOI: 10.12688/f1000research.12155.1] [Citation(s) in RCA: 122] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/21/2017] [Indexed: 12/21/2022] Open
Abstract
Neuronal networks consist of different types of neurons that all play their own role in order to maintain proper network function. The two main types of neurons segregate in excitatory and inhibitory neurons, which together regulate the flow of information through the network. It has been proposed that changes in the relative strength in these two opposing forces underlie the symptoms observed in psychiatric disorders, including autism and schizophrenia. Here, we review the role of alterations to the function of the inhibitory system as a cause of psychiatric disorders. First, we explore both patient and post-mortem evidence of inhibitory deficiency. We then discuss the function of different interneuron subtypes in the network and focus on the central role of a specific class of inhibitory neurons, parvalbumin-positive interneurons. Finally, we discuss genes known to be affected in different disorders and the effects that mutations in these genes have on the inhibitory system in cortex and hippocampus. We conclude that alterations to the inhibitory system are consistently identified in animal models of psychiatric disorders and, more specifically, that mutations affecting the function of parvalbumin-positive interneurons seem to play a central role in the symptoms observed in these disorders.
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Affiliation(s)
- Martijn Selten
- Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, New Hunt's House, Guy's Campus, King's College London, London, SE1 1UL, UK.,MRC Centre for Neurodevelopmental Disorders, New Hunt's House, Guy's Campus, King's College London, London, SE1 1UL, UK.,Department of Human Genetics & Department of Cognitive Neuroscience, Radboudumc, Geert Grooteplein 10, Box 9101, 6500 HB Nijmegen, Netherlands.,Donders Institute for Brain, Cognition, and Behaviour, Centre for Neuroscience, 6525 AJ Nijmegen, Netherlands
| | - Hans van Bokhoven
- Department of Human Genetics & Department of Cognitive Neuroscience, Radboudumc, Geert Grooteplein 10, Box 9101, 6500 HB Nijmegen, Netherlands.,Donders Institute for Brain, Cognition, and Behaviour, Centre for Neuroscience, 6525 AJ Nijmegen, Netherlands
| | - Nael Nadif Kasri
- Department of Human Genetics & Department of Cognitive Neuroscience, Radboudumc, Geert Grooteplein 10, Box 9101, 6500 HB Nijmegen, Netherlands.,Donders Institute for Brain, Cognition, and Behaviour, Centre for Neuroscience, 6525 AJ Nijmegen, Netherlands
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9
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Abstract
Cortical networks are composed of glutamatergic excitatory projection neurons and local GABAergic inhibitory interneurons that gate signal flow and sculpt network dynamics. Although they represent a minority of the total neocortical neuronal population, GABAergic interneurons are highly heterogeneous, forming functional classes based on their morphological, electrophysiological, and molecular features, as well as connectivity and in vivo patterns of activity. Here we review our current understanding of neocortical interneuron diversity and the properties that distinguish cell types. We then discuss how the involvement of multiple cell types, each with a specific set of cellular properties, plays a crucial role in diversifying and increasing the computational power of a relatively small number of simple circuit motifs forming cortical networks. We illustrate how recent advances in the field have shed light onto the mechanisms by which GABAergic inhibition contributes to network operations.
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10
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Rinetti-Vargas G, Phamluong K, Ron D, Bender KJ. Periadolescent Maturation of GABAergic Hyperpolarization at the Axon Initial Segment. Cell Rep 2017; 20:21-29. [PMID: 28683314 PMCID: PMC6483373 DOI: 10.1016/j.celrep.2017.06.030] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 05/15/2017] [Accepted: 06/11/2017] [Indexed: 10/25/2022] Open
Abstract
Neuronal chloride levels are developmentally regulated. Early in life, high intracellular concentrations support chloride efflux and depolarization at GABAergic synapses. In mouse, intracellular chloride decreases over the first postnatal week in the somatodendritic compartment, eventually supporting mature, hyperpolarizing GABAergic inhibition. In contrast to this dendritic switch, it is less clear how GABAergic signaling at the axon initial segment (AIS) functions in mature pyramidal cells, as reports of both depolarization and hyperpolarization have been reported in the AIS past the first postnatal week. Here, we show that GABAergic signaling at the AIS of prefrontal pyramidal cells, indeed, switches polarity from depolarizing to hyperpolarizing but does so over a protracted periadolescent period. This is the most delayed maturation in chloride reversal in any structure studied to date and suggests that chandelier cells, which mediate axo-axonic inhibition, play a unique role in the periadolescent maturation of prefrontal circuits.
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Affiliation(s)
- Gina Rinetti-Vargas
- Center for Integrative Neuroscience, University of California, San Francisco, San Francisco, CA 94143, USA; UCSF Weill Institute for Neuroscience, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Neurology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Khanhky Phamluong
- UCSF Weill Institute for Neuroscience, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Neurology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Dorit Ron
- UCSF Weill Institute for Neuroscience, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Neurology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Kevin J Bender
- Center for Integrative Neuroscience, University of California, San Francisco, San Francisco, CA 94143, USA; UCSF Weill Institute for Neuroscience, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Neurology, University of California, San Francisco, San Francisco, CA 94143, USA.
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11
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Wang Y, Zhang P, Wyskiel DR. Chandelier Cells in Functional and Dysfunctional Neural Circuits. Front Neural Circuits 2016; 10:33. [PMID: 27199673 PMCID: PMC4854894 DOI: 10.3389/fncir.2016.00033] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Accepted: 04/08/2016] [Indexed: 01/08/2023] Open
Abstract
Chandelier cells (ChCs; also called axo-axonic cells) are a specialized GABAergic interneuron subtype that selectively innervates pyramidal neurons at the axon initial segment (AIS), the site of action potential generation. ChC connectivity allows for powerful yet precise modulation of large populations of pyramidal cells, suggesting ChCs have a critical role in brain functions. Dysfunctions in ChC connectivity are associated with brain disorders such as epilepsy and schizophrenia; however, whether this is causative, contributory or compensatory is not known. A likely stumbling block toward mechanistic discoveries and uncovering potential therapeutic targets is the apparent lack of rudimentary understanding of ChCs. For example, whether cortical ChCs are inhibitory or excitatory remains unresolved, and thus whether altered ChC activity results in altered inhibition or excitation is not clear. Recent studies have shed some light onto this excitation-inhibition controversy. In addition, new findings have identified preferential cell-type connectivities established by cortical ChCs, greatly expanding our understanding of the role of ChCs in the cortical microcircuit. Here we aim to bring more attention to ChC connectivity to better understand its role in neural circuits, address whether ChCs are inhibitory or excitatory in light of recent findings and discuss ChC dysfunctions in brain disorders.
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Affiliation(s)
- Yiqing Wang
- Department of Pharmacology, University of VirginiaCharlottesville, VA, USA; Department of Chemistry, University of VirginiaCharlottesville, VA, USA
| | - Peng Zhang
- Department of Pharmacology, University of Virginia Charlottesville, VA, USA
| | - Daniel R Wyskiel
- Department of Pharmacology, University of Virginia Charlottesville, VA, USA
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12
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13
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Jaiswal MK, Keros S, Zhao M, Inan M, Schwartz TH, Anderson SA, Homanics GE, Goldstein PA. Reduction in focal ictal activity following transplantation of MGE interneurons requires expression of the GABAA receptor α4 subunit. Front Cell Neurosci 2015; 9:127. [PMID: 25914623 PMCID: PMC4391265 DOI: 10.3389/fncel.2015.00127] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 03/18/2015] [Indexed: 12/14/2022] Open
Abstract
Despite numerous advances, treatment-resistant seizures remain an important problem. Loss of neuronal inhibition is present in a variety of epilepsy models and is suggested as a mechanism for increased excitability, leading to the proposal that grafting inhibitory interneurons into seizure foci might relieve refractory seizures. Indeed, transplanted medial ganglionic eminence interneuron progenitors (MGE-IPs) mature into GABAergic interneurons that increase GABA release onto cortical pyramidal neurons, and this inhibition is associated with reduced seizure activity. An obvious conclusion is that inhibitory coupling between the new interneurons and pyramidal cells underlies this effect. We hypothesized that the primary mechanism for the seizure-limiting effects following MGE-IP transplantation is the tonic conductance that results from activation of extrasynaptic GABAA receptors (GABAA-Rs) expressed on cortical pyramidal cells. Using in vitro and in vivo recording techniques, we demonstrate that GABAA-R α4 subunit deletion abolishes tonic currents (Itonic) in cortical pyramidal cells and leads to a failure of MGE-IP transplantation to attenuate cortical seizure propagation. These observations should influence how the field proceeds with respect to the further development of therapeutic neuronal transplants (and possibly pharmacological treatments).
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Affiliation(s)
- Manoj K Jaiswal
- C.V. Starr Laboratory for Molecular Neuropharmacology, Department of Anesthesiology, Weill Cornell Medical College New York, NY, USA
| | - Sotirios Keros
- Department of Pediatrics, Weill Cornell Medical College New York, NY, USA
| | - Mingrui Zhao
- Department of Neurological Surgery, Weill Cornell Medical College New York, NY, USA ; Brain and Mind Research Institute, Weill Cornell Medical College New York, NY, USA
| | - Melis Inan
- Brain and Mind Research Institute, Weill Cornell Medical College New York, NY, USA
| | - Theodore H Schwartz
- Department of Neurological Surgery, Weill Cornell Medical College New York, NY, USA ; Brain and Mind Research Institute, Weill Cornell Medical College New York, NY, USA
| | - Stewart A Anderson
- Department of Psychiatry, Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine Philadelphia, PA, USA
| | - Gregg E Homanics
- Department of Anesthesiology, University of Pittsburgh Pittsburgh, PA, USA
| | - Peter A Goldstein
- C.V. Starr Laboratory for Molecular Neuropharmacology, Department of Anesthesiology, Weill Cornell Medical College New York, NY, USA
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