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Montalant A, Kiehn O, Perrier JF. Dopamine and noradrenaline activate spinal astrocyte endfeet via D1-like receptors. Eur J Neurosci 2024; 59:1278-1295. [PMID: 38052454 DOI: 10.1111/ejn.16205] [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: 09/08/2023] [Revised: 11/02/2023] [Accepted: 11/10/2023] [Indexed: 12/07/2023]
Abstract
Astrocytes, the most abundant glial cells in the central nervous system, respond to a wide variety of neurotransmitters binding to metabotropic receptors. Here, we investigated the intracellular calcium responses of spinal cord astrocytes to dopamine and noradrenaline, two catecholamines released by specific descending pathways. In a slice preparation from the spinal cord of neonatal mice, puff application of dopamine resulted in intracellular calcium responses that remained in the endfeet. Noradrenaline induced stronger responses that also started in the endfeet but spread to neighbouring compartments. The intracellular calcium responses were unaffected by blocking neuronal activity or inhibiting various neurotransmitter receptors, suggesting a direct effect of dopamine and noradrenaline on astrocytes. The intracellular calcium responses induced by noradrenaline and dopamine were inhibited by the D1 receptor antagonist SCH 23390. We assessed the functional consequences of these astrocytic responses by examining changes in arteriole diameter. Puff application of dopamine or noradrenaline resulted in vasoconstriction of spinal arterioles. However, blocking D1 receptors or manipulating astrocytic intracellular calcium levels did not abolish the vasoconstrictions, indicating that the observed intracellular calcium responses in astrocyte endfeet were not responsible for the vascular changes. Our findings demonstrate a compartmentalized response of spinal cord astrocytes to catecholamines and expand our understanding of astrocyte-neurotransmitter interactions and their potential roles in the physiology of the central nervous system.
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Affiliation(s)
- Alexia Montalant
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Ole Kiehn
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jean-François Perrier
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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2
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Tran KA, DeOre BJ, Ikejiani D, Means K, Paone LS, De Marchi L, Suprewicz Ł, Koziol K, Bouyer J, Byfield FJ, Jin Y, Georges P, Fischer I, Janmey PA, Galie PA. Matching mechanical heterogeneity of the native spinal cord augments axon infiltration in 3D-printed scaffolds. Biomaterials 2023; 295:122061. [PMID: 36842339 PMCID: PMC10292106 DOI: 10.1016/j.biomaterials.2023.122061] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 02/09/2023] [Accepted: 02/15/2023] [Indexed: 02/18/2023]
Abstract
Scaffolds delivered to injured spinal cords to stimulate axon connectivity often match the anisotropy of native tissue using guidance cues along the rostral-caudal axis, but current approaches do not mimic the heterogeneity of host tissue mechanics. Although white and gray matter have different mechanical properties, it remains unclear whether tissue mechanics also vary along the length of the cord. Mechanical testing performed in this study indicates that bulk spinal cord mechanics do differ along anatomical level and that these differences are caused by variations in the ratio of white and gray matter. These results suggest that scaffolds recreating the heterogeneity of spinal cord tissue mechanics must account for the disparity between gray and white matter. Digital light processing (DLP) provides a means to mimic spinal cord topology, but has previously been limited to printing homogeneous mechanical properties. We describe a means to modify DLP to print scaffolds that mimic spinal cord mechanical heterogeneity caused by variation in the ratio of white and gray matter, which improves axon infiltration compared to controls exhibiting homogeneous mechanical properties. These results demonstrate that scaffolds matching the mechanical heterogeneity of white and gray matter improve the effectiveness of biomaterials transplanted within the injured spinal cord.
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Affiliation(s)
- Kiet A Tran
- Department of Biomedical Engineering, Rowan University, Glassboro, NJ, USA
| | - Brandon J DeOre
- Department of Biomedical Engineering, Rowan University, Glassboro, NJ, USA
| | - David Ikejiani
- Department of Bioengineering, Rice University, Houston, TX, USA
| | - Kristen Means
- Department of Bioengineering, Rice University, Houston, TX, USA
| | - Louis S Paone
- Department of Biomedical Engineering, Rowan University, Glassboro, NJ, USA
| | - Laura De Marchi
- Department of Biomedical Engineering, Rowan University, Glassboro, NJ, USA
| | - Łukasz Suprewicz
- Department of Medical Microbiology and Nanobiomedical Engineering, Medical University of Bialystok, Bialystok, Poland
| | - Katarina Koziol
- Department of Biomedical Engineering, Rowan University, Glassboro, NJ, USA
| | - Julien Bouyer
- Department of Neurobiology and Anatomy, Drexel College of Medicine, Philadelphia, PA, USA
| | - Fitzroy J Byfield
- Department of Physiology, University of Pennsylvania, Philadelphia, PA, USA
| | - Ying Jin
- Department of Neurobiology and Anatomy, Drexel College of Medicine, Philadelphia, PA, USA
| | - Penelope Georges
- Council on Science and Technology, Princeton University, Princeton, NJ, USA
| | - Itzhak Fischer
- Department of Neurobiology and Anatomy, Drexel College of Medicine, Philadelphia, PA, USA
| | - Paul A Janmey
- Department of Physiology, University of Pennsylvania, Philadelphia, PA, USA
| | - Peter A Galie
- Department of Biomedical Engineering, Rowan University, Glassboro, NJ, USA.
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3
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Bertalan G, Becker J, Tzschätzsch H, Morr A, Herthum H, Shahryari M, Greenhalgh RD, Guo J, Schröder L, Alzheimer C, Budday S, Franze K, Braun J, Sack I. Mechanical behavior of the hippocampus and corpus callosum: An attempt to reconcile ex vivo with in vivo and micro with macro properties. J Mech Behav Biomed Mater 2023; 138:105613. [PMID: 36549250 DOI: 10.1016/j.jmbbm.2022.105613] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2022] [Revised: 11/24/2022] [Accepted: 12/06/2022] [Indexed: 12/13/2022]
Abstract
Mechanical properties of brain tissue are very complex and vary with the species, region, method, and dynamic range, and between in vivo and ex vivo measurements. To reconcile this variability, we investigated in vivo and ex vivo stiffness properties of two distinct regions in the human and mouse brain - the hippocampus (HP) and the corpus callosum (CC) - using different methods. Under quasi-static conditions, we examined ex vivo murine HP and CC by atomic force microscopy (AFM). Between 16 and 40Hz, we investigated the in vivo brains of healthy volunteers by magnetic resonance elastography (MRE) in a 3-T clinical scanner. At high-frequency stimulation between 1000 and 1400Hz, we investigated the murine HP and CC ex vivo and in vivo with MRE in a 7-T preclinical system. HP and CC showed pronounced stiffness dispersion, as reflected by a factor of 32-36 increase in shear modulus from AFM to low-frequency human MRE and a 25-fold higher shear wave velocity in murine MRE than in human MRE. At low frequencies, HP was softer than CC, in both ex vivo mouse specimens (p < 0.05) and in vivo human brains (p < 0.01) while, at high frequencies, CC was softer than HP under in vivo (p < 0.01) and ex vivo (p < 0.05) conditions. The standard linear solid model comprising three elements reproduced the observed HP and CC stiffness dispersions, while other two- and three-element models failed. Our results indicate a remarkable consistency of brain stiffness across species, ex vivo and in vivo states, and different measurement techniques when marked viscoelastic dispersion properties combining equilibrium and non-equilibrium mechanical elements are considered.
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Affiliation(s)
- Gergerly Bertalan
- Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Julia Becker
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Heiko Tzschätzsch
- Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Anna Morr
- Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Helge Herthum
- Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Mehrgan Shahryari
- Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Ryan D Greenhalgh
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Jing Guo
- Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Leif Schröder
- Translational Molecular Imaging, Deutsches Krebsforschungszentrum, Heidelberg, Germany
| | - Christian Alzheimer
- Institute of Physiology and Pathophysiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Silvia Budday
- Institute of Applied Mechanics, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Kristian Franze
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom; Institute of Medical Physics, Friedrich-Alexander-Universität, Erlangen-Nürnberg, Erlangen, Germany; Max-Planck-Zentrum für Physik und Medizin, Erlangen, Germany
| | - Jürgen Braun
- Institute of Medical Informatics, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Ingolf Sack
- Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany.
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4
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Khan MN, Cherukuri P, Negro F, Rajput A, Fabrowski P, Bansal V, Lancelin C, Lee TI, Bian Y, Mayer WP, Akay T, Müller D, Bonn S, Farina D, Marquardt T. ERR2 and ERR3 promote the development of gamma motor neuron functional properties required for proprioceptive movement control. PLoS Biol 2022; 20:e3001923. [PMID: 36542664 PMCID: PMC9815657 DOI: 10.1371/journal.pbio.3001923] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 01/05/2023] [Accepted: 11/16/2022] [Indexed: 12/24/2022] Open
Abstract
The ability of terrestrial vertebrates to effectively move on land is integrally linked to the diversification of motor neurons into types that generate muscle force (alpha motor neurons) and types that modulate muscle proprioception, a task that in mammals is chiefly mediated by gamma motor neurons. The diversification of motor neurons into alpha and gamma types and their respective contributions to movement control have been firmly established in the past 7 decades, while recent studies identified gene expression signatures linked to both motor neuron types. However, the mechanisms that promote the specification of gamma motor neurons and/or their unique properties remained unaddressed. Here, we found that upon selective loss of the orphan nuclear receptors ERR2 and ERR3 (also known as ERRβ, ERRγ or NR3B2, NR3B3, respectively) in motor neurons in mice, morphologically distinguishable gamma motor neurons are generated but do not acquire characteristic functional properties necessary for regulating muscle proprioception, thus disrupting gait and precision movements. Complementary gain-of-function experiments in chick suggest that ERR2 and ERR3 could operate via transcriptional activation of neural activity modulators to promote a gamma motor neuron biophysical signature of low firing thresholds and high firing rates. Our work identifies a mechanism specifying gamma motor neuron functional properties essential for the regulation of proprioceptive movement control.
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Affiliation(s)
- Mudassar N. Khan
- Interfaculty Chair for Neurobiological Research, RWTH Aachen University: Medical Faculty (UKA), Clinic for Neurology & Faculty for Mathematics, Computer and Natural Sciences, Institute for Biology 2, Aachen, Germany
- Developmental Neurobiology Laboratory, European Neuroscience Institute (ENI-G), Göttingen, Germany
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
- * E-mail: (MNK); (TM)
| | - Pitchaiah Cherukuri
- Interfaculty Chair for Neurobiological Research, RWTH Aachen University: Medical Faculty (UKA), Clinic for Neurology & Faculty for Mathematics, Computer and Natural Sciences, Institute for Biology 2, Aachen, Germany
- Developmental Neurobiology Laboratory, European Neuroscience Institute (ENI-G), Göttingen, Germany
- SRM University Andhra Pradesh, Mangalagiri-Mandal, Neeru Konda, Amaravati, Andhra Pradesh, India
| | - Francesco Negro
- Department of Clinical and Experimental Sciences, Università degli Studi di Brescia, Brescia, Italy
| | - Ashish Rajput
- University Medical Center Hamburg Eppendorf, Center for Molecular Neurobiology Hamburg (ZMNH), Institute of Medical Systems Biology, Hamburg, Germany
- Maximon AG, Zug, Switzerland
| | - Piotr Fabrowski
- Interfaculty Chair for Neurobiological Research, RWTH Aachen University: Medical Faculty (UKA), Clinic for Neurology & Faculty for Mathematics, Computer and Natural Sciences, Institute for Biology 2, Aachen, Germany
- Developmental Neurobiology Laboratory, European Neuroscience Institute (ENI-G), Göttingen, Germany
| | - Vikas Bansal
- University Medical Center Hamburg Eppendorf, Center for Molecular Neurobiology Hamburg (ZMNH), Institute of Medical Systems Biology, Hamburg, Germany
- Biomedical Data Science and Machine Learning Group, German Center for Neurodegenerative Diseases, Tübingen, Germany
| | - Camille Lancelin
- Developmental Neurobiology Laboratory, European Neuroscience Institute (ENI-G), Göttingen, Germany
| | - Tsung-I Lee
- Developmental Neurobiology Laboratory, European Neuroscience Institute (ENI-G), Göttingen, Germany
| | - Yehan Bian
- Interfaculty Chair for Neurobiological Research, RWTH Aachen University: Medical Faculty (UKA), Clinic for Neurology & Faculty for Mathematics, Computer and Natural Sciences, Institute for Biology 2, Aachen, Germany
- Developmental Neurobiology Laboratory, European Neuroscience Institute (ENI-G), Göttingen, Germany
| | - William P. Mayer
- Atlantic Mobility Action Project, Brain Repair Centre, Department of Medical Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Turgay Akay
- Atlantic Mobility Action Project, Brain Repair Centre, Department of Medical Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Daniel Müller
- Interfaculty Chair for Neurobiological Research, RWTH Aachen University: Medical Faculty (UKA), Clinic for Neurology & Faculty for Mathematics, Computer and Natural Sciences, Institute for Biology 2, Aachen, Germany
- Developmental Neurobiology Laboratory, European Neuroscience Institute (ENI-G), Göttingen, Germany
| | - Stefan Bonn
- University Medical Center Hamburg Eppendorf, Center for Molecular Neurobiology Hamburg (ZMNH), Institute of Medical Systems Biology, Hamburg, Germany
| | - Dario Farina
- Department of Bioengineering, Imperial College London, Royal School of Mines, London, United Kingdom
| | - Till Marquardt
- Interfaculty Chair for Neurobiological Research, RWTH Aachen University: Medical Faculty (UKA), Clinic for Neurology & Faculty for Mathematics, Computer and Natural Sciences, Institute for Biology 2, Aachen, Germany
- Developmental Neurobiology Laboratory, European Neuroscience Institute (ENI-G), Göttingen, Germany
- * E-mail: (MNK); (TM)
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5
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Özyurt MG, Ojeda-Alonso J, Beato M, Nascimento F. In vitro longitudinal lumbar spinal cord preparations to study sensory and recurrent motor microcircuits of juvenile mice. J Neurophysiol 2022; 128:711-726. [PMID: 35946796 PMCID: PMC9485001 DOI: 10.1152/jn.00184.2022] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In vitro spinal cord preparations have been extensively used to study microcircuits involved in the control of movement. By allowing precise control of experimental conditions coupled with state-of-the-art genetics, imaging, and electrophysiological techniques, isolated spinal cords from mice have been an essential tool in detailing the identity, connectivity, and function of spinal networks. The majority of the research has arisen from in vitro spinal cords of neonatal mice, which are still undergoing important postnatal maturation. Studies from adults have been attempted in transverse slices, however, these have been quite challenging due to the poor motoneuron accessibility and viability, as well as the extensive damage to the motoneuron dendritic trees. In this work, we describe two types of coronal spinal cord preparations with either the ventral or the dorsal horn ablated, obtained from mice of different postnatal ages, spanning from preweaned to 1 mo old. These semi-intact preparations allow recordings of sensory-afferent and motor-efferent responses from lumbar motoneurons using whole cell patch-clamp electrophysiology. We provide details of the slicing procedure and discuss the feasibility of whole cell recordings. The in vitro dorsal and ventral horn-ablated spinal cord preparations described here are a useful tool to study spinal motor circuits in young mice that have reached the adult stages of locomotor development.NEW & NOTEWORTHY In the past 20 years, most of the research into the mammalian spinal circuitry has been limited to in vitro preparations from embryonic and neonatal mice. We describe two in vitro longitudinal lumbar spinal cord preparations from juvenile mice that allow the study of motoneuron properties and respective afferent or efferent spinal circuits through whole cell patch clamp. These preparations will be useful to those interested in the study of microcircuits at mature stages of motor development.
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Affiliation(s)
- Mustafa Görkem Özyurt
- 1Department of Neuroscience Physiology and Pharmacology (NPP), grid.83440.3bUniversity College London, London, United Kingdom,2Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom
| | - Julia Ojeda-Alonso
- 1Department of Neuroscience Physiology and Pharmacology (NPP), grid.83440.3bUniversity College London, London, United Kingdom
| | - Marco Beato
- 1Department of Neuroscience Physiology and Pharmacology (NPP), grid.83440.3bUniversity College London, London, United Kingdom
| | - Filipe Nascimento
- 1Department of Neuroscience Physiology and Pharmacology (NPP), grid.83440.3bUniversity College London, London, United Kingdom,2Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom
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6
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Garcia-Ramirez DL, Singh S, McGrath JR, Ha NT, Dougherty KJ. Identification of adult spinal Shox2 neuronal subpopulations based on unbiased computational clustering of electrophysiological properties. Front Neural Circuits 2022; 16:957084. [PMID: 35991345 PMCID: PMC9385948 DOI: 10.3389/fncir.2022.957084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 07/08/2022] [Indexed: 11/13/2022] Open
Abstract
Spinal cord neurons integrate sensory and descending information to produce motor output. The expression of transcription factors has been used to dissect out the neuronal components of circuits underlying behaviors. However, most of the canonical populations of interneurons are heterogeneous and require additional criteria to determine functional subpopulations. Neurons expressing the transcription factor Shox2 can be subclassified based on the co-expression of the transcription factor Chx10 and each subpopulation is proposed to have a distinct connectivity and different role in locomotion. Adult Shox2 neurons have recently been shown to be diverse based on their firing properties. Here, in order to subclassify adult mouse Shox2 neurons, we performed multiple analyses of data collected from whole-cell patch clamp recordings of visually-identified Shox2 neurons from lumbar spinal slices. A smaller set of Chx10 neurons was included in the analyses for validation. We performed k-means and hierarchical unbiased clustering approaches, considering electrophysiological variables. Unlike the categorizations by firing type, the clusters displayed electrophysiological properties that could differentiate between clusters of Shox2 neurons. The presence of clusters consisting exclusively of Shox2 neurons in both clustering techniques suggests that it is possible to distinguish Shox2+Chx10- neurons from Shox2+Chx10+ neurons by electrophysiological properties alone. Computational clusters were further validated by immunohistochemistry with accuracy in a small subset of neurons. Thus, unbiased cluster analysis using electrophysiological properties is a tool that can enhance current interneuronal subclassifications and can complement groupings based on transcription factor and molecular expression.
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Affiliation(s)
| | | | | | | | - Kimberly J. Dougherty
- Department of Neurobiology and Anatomy, Marion Murray Spinal Cord Research Center, Drexel University College of Medicine, Philadelphia, PA, United States
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7
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Ghobreal B, Nadim F, Sahin M. Selective neural stimulation by leveraging electrophysiological differentiation and using pre-pulsing and non-rectangular waveforms. J Comput Neurosci 2022; 50:313-330. [PMID: 35419717 DOI: 10.1007/s10827-022-00818-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 03/10/2022] [Accepted: 03/22/2022] [Indexed: 10/18/2022]
Abstract
Efforts on selective neural stimulation have concentrated on segregating axons based on their size and geometry. Nonetheless, axons of the white matter or peripheral nerves may also differ in their electrophysiological properties. The primary objective of this study was to investigate the possibility of selective activation of axons by leveraging an assumed level of diversity in passive (Cm & Gleak) and active membrane properties (Ktemp & Gnamax). First, the stimulus waveforms with hyperpolarizing (HPP) and depolarizing pre-pulsing (DPP) were tested on selectivity in a local membrane model. The default value of membrane capacitance (Cm) was found to play a critical role in sensitivity of the chronaxie time (Chr) and rheobase (Rhe) to variations of all the four membrane parameters. Decreasing the default value of Cm, and thus the passive time constant of the membrane, amplified the sensitivity to the active parameters, Ktemp and GNamax, on Chr. The HPP waveform could selectively activate neurons even if they were diversified by membrane leakage (Gleak) only, and produced higher selectivity than DPP when parameters are varied in pairs. Selectivity measures were larger when the passive parameters (Cm & Gleak) were varied together, compared to the active parameters. Second, this novel mechanism of selectivity was investigated with non-rectangular waveforms for the stimulating phase (and HPP) in the same local membrane model. Simulation results suggest that Kt2 is the most selective waveform followed by Linear and Gaussian waveforms. Traditional rectangular pulse was among the least selective of all. Finally, a compartmental axon model confirmed the main findings of the local model that Kt2 is the most selective, but rank ordered the other waveforms differently. These results suggest a potentially novel mechanism of stimulation selectivity, leveraging electrophysiological variations in membrane properties, that can lead to various neural prosthetic applications.
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Affiliation(s)
- Bemin Ghobreal
- Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, NJ, 07102, USA
| | - Farzan Nadim
- Department of Biology, New Jersey Institute of Technology, Newark, NJ, 07102, USA
| | - Mesut Sahin
- Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, NJ, 07102, USA.
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8
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Clerc N, Moqrich A. Diverse roles and modulations of I A in spinal cord pain circuits. Cell Rep 2022; 38:110588. [PMID: 35354022 DOI: 10.1016/j.celrep.2022.110588] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 02/25/2022] [Accepted: 03/08/2022] [Indexed: 11/03/2022] Open
Abstract
This review highlights recent findings of different amplitude ranges, roles, and modulations of A-type K+ currents (IA) in excitatory (GAD67-GFP-) and inhibitory (GAD67-GFP+) interneurons in mouse spinal cord pain pathways. Endogenous neuropeptides, such as TAFA4, oxytocin, and dynorphin in particular, have been reported to modulate IA in these pain pathways, but only TAFA4 has been shown to fully reverse the opposing modulations that occur selectively in LIIo GAD67-GFP- and LIIi GAD67-GFP+ interneurons following both neuropathic and inflammatory pain. If, as hypothesized here, Kv4 subunits underlie IA in both GAD67-GFP- and GAD67-GFP+ interneurons, then IA diversity in spinal cord pain pathways may depend on the interneuron-subtype-selective expression of Kv4 auxiliary subunits with functionally different N-terminal variants. Thus, IA emerges as a good candidate for explaining the mechanisms underlying injury-induced mechanical hypersensitivity.
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Affiliation(s)
- Nadine Clerc
- Aix-Marseille-Université, CNRS, Institut de Biologie du Développement de Marseille, UMR 7288, Case 907, 13288 Marseille Cedex 09, France.
| | - Aziz Moqrich
- Aix-Marseille-Université, CNRS, Institut de Biologie du Développement de Marseille, UMR 7288, Case 907, 13288 Marseille Cedex 09, France
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9
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Rimmele TS, Li S, Andersen JV, Westi EW, Rotenberg A, Wang J, Aldana BI, Selkoe DJ, Aoki CJ, Dulla CG, Rosenberg PA. Neuronal Loss of the Glutamate Transporter GLT-1 Promotes Excitotoxic Injury in the Hippocampus. Front Cell Neurosci 2022; 15:788262. [PMID: 35035352 PMCID: PMC8752461 DOI: 10.3389/fncel.2021.788262] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 12/08/2021] [Indexed: 12/26/2022] Open
Abstract
GLT-1, the major glutamate transporter in the mammalian central nervous system, is expressed in presynaptic terminals that use glutamate as a neurotransmitter, in addition to astrocytes. It is widely assumed that glutamate homeostasis is regulated primarily by glutamate transporters expressed in astrocytes, leaving the function of GLT-1 in neurons relatively unexplored. We generated conditional GLT-1 knockout (KO) mouse lines to understand the cell-specific functions of GLT-1. We found that stimulus-evoked field extracellular postsynaptic potentials (fEPSPs) recorded in the CA1 region of the hippocampus were normal in the astrocytic GLT-1 KO but were reduced and often absent in the neuronal GLT-1 KO at 40 weeks. The failure of fEPSP generation in the neuronal GLT-1 KO was also observed in slices from 20 weeks old mice but not consistently from 10 weeks old mice. Using an extracellular FRET-based glutamate sensor, we found no difference in stimulus-evoked glutamate accumulation in the neuronal GLT-1 KO, suggesting a postsynaptic cause of the transmission failure. We hypothesized that excitotoxicity underlies the failure of functional recovery of slices from the neuronal GLT-1 KO. Consistent with this hypothesis, the non-competitive NMDA receptor antagonist MK801, when present in the ACSF during the recovery period following cutting of slices, promoted full restoration of fEPSP generation. The inclusion of an enzymatic glutamate scavenging system in the ACSF conferred partial protection. Excitotoxicity might be due to excess release or accumulation of excitatory amino acids, or to metabolic perturbation resulting in increased vulnerability to NMDA receptor activation. Previous studies have demonstrated a defect in the utilization of glutamate by synaptic mitochondria and aspartate production in the synGLT-1 KO in vivo, and we found evidence for similar metabolic perturbations in the slice preparation. In addition, mitochondrial cristae density was higher in synaptic mitochondria in the CA1 region in 20–25 weeks old synGLT-1 KO mice in the CA1 region, suggesting compensation for loss of axon terminal GLT-1 by increased mitochondrial efficiency. These data suggest that GLT-1 expressed in presynaptic terminals serves an important role in the regulation of vulnerability to excitotoxicity, and this regulation may be related to the metabolic role of GLT-1 expressed in glutamatergic axon terminals.
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Affiliation(s)
- Theresa S Rimmele
- Department of Neurology and the F. M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, United States
| | - Shaomin Li
- Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, United States
| | - Jens Velde Andersen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Emil W Westi
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Alexander Rotenberg
- Department of Neurology and the F. M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, United States.,Program in Neuroscience, Harvard Medical School, Boston, MA, United States
| | - Jianlin Wang
- Department of Neurology and the F. M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, United States
| | - Blanca Irene Aldana
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Dennis J Selkoe
- Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, United States
| | - Chiye J Aoki
- Center for Neural Science, New York University, NY, United States.,Neuroscience Institute NYU Langone Medical Center, NY, United States
| | - Chris G Dulla
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, United States
| | - Paul Allen Rosenberg
- Department of Neurology and the F. M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, United States.,Program in Neuroscience, Harvard Medical School, Boston, MA, United States
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10
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Electrical Properties of Adult Mammalian Motoneurons. ADVANCES IN NEUROBIOLOGY 2022; 28:191-232. [PMID: 36066827 DOI: 10.1007/978-3-031-07167-6_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
Motoneurons are the 'final common path' between the central nervous system (that intends, selects, commands, and organises movement) and muscles (that produce the behaviour). Motoneurons are not passive relays, but rather integrate synaptic activity to appropriately tune output (spike trains) and therefore the production of muscle force. In this chapter, we focus on studies of mammalian motoneurons, describing their heterogeneity whilst providing a brief historical account of motoneuron recording techniques. Next, we describe adult motoneurons in terms of their passive, transition, and active (repetitive firing) properties. We then discuss modulation of these properties by somatic (C-boutons) and dendritic (persistent inward currents) mechanisms. Finally, we briefly describe select studies of human motor unit physiology and relate them to findings from animal preparations discussed earlier in the chapter. This interphyletic approach to the study of motoneuron physiology is crucial to progress understanding of how these diverse neurons translate intention into behaviour.
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Abstract
When animals walk overground, mechanical stimuli activate various receptors located in muscles, joints, and skin. Afferents from these mechanoreceptors project to neuronal networks controlling locomotion in the spinal cord and brain. The dynamic interactions between the control systems at different levels of the neuraxis ensure that locomotion adjusts to its environment and meets task demands. In this article, we describe and discuss the essential contribution of somatosensory feedback to locomotion. We start with a discussion of how biomechanical properties of the body affect somatosensory feedback. We follow with the different types of mechanoreceptors and somatosensory afferents and their activity during locomotion. We then describe central projections to locomotor networks and the modulation of somatosensory feedback during locomotion and its mechanisms. We then discuss experimental approaches and animal models used to investigate the control of locomotion by somatosensory feedback before providing an overview of the different functional roles of somatosensory feedback for locomotion. Lastly, we briefly describe the role of somatosensory feedback in the recovery of locomotion after neurological injury. We highlight the fact that somatosensory feedback is an essential component of a highly integrated system for locomotor control. © 2021 American Physiological Society. Compr Physiol 11:1-71, 2021.
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Affiliation(s)
- Alain Frigon
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Quebec, Canada
| | - Turgay Akay
- Department of Medical Neuroscience, Atlantic Mobility Action Project, Brain Repair Center, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Boris I Prilutsky
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
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Mitochondrial Function and Anesthetic Sensitivity in the Mouse Spinal Cord. Anesthesiology 2021; 134:901-914. [PMID: 33909880 DOI: 10.1097/aln.0000000000003794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
BACKGROUND Ndufs4 knockout (KO) mice are defective in mitochondrial complex I function and hypersensitive to inhibition of spinal cord-mediated response to noxious stimuli by volatile anesthetics. It was hypothesized that, compared to wild-type, synaptic or intrinsic neuronal function is hypersensitive to isoflurane in spinal cord slices from knockout mice. METHODS Neurons from slices of the vestibular nucleus, central medial thalamus, and spinal cord from wild-type and the global Ndufs4 knockout were patch clamped. Unstimulated synaptic and intrinsic neuronal characteristics were measured in response to isoflurane. Norfluoxetine was used to block TREK channel conductance. Cholinergic cells were labeled with tdTomato. RESULTS All values are reported as means and 95% CIs. Spontaneous synaptic activities were not different between the mutant and control. Isoflurane (0.6%; 0.25 mM; Ndufs4[KO] EC95) increased the holding current in knockout (ΔHolding current, 126 pA [95% CI, 99 to 152 pA]; ΔHolding current P < 0.001; n = 21) but not wild-type (ΔHolding current, 2 7 pA [95% CI, 9 to 47 pA]; ΔHolding current, P = 0.030; n = 25) spinal cord slices. Knockout and wild-type ΔHolding currents were significantly different (P < 0.001). Changes comparable to those in the knockout were seen in the wild type only in 1.8% (0.74 mM) isoflurane (ΔHolding current, 72 pA [95% CI, 43 to 97 pA]; ΔHolding current, P < 0.001; n = 13), the control EC95. Blockade of action potentials indicated that the increased holding current in the knockout was not dependent on synaptic input (ΔHolding current, 154 pA [95% CI, 99 to 232 pA]; ΔHolding current, P = 0.506 compared to knockout without blockade; n = 6). Noncholinergic neurons mediated the increase in holding current sensitivity in Ndufs4 knockout. The increased currents were blocked by norfluoxetine. CONCLUSIONS Isoflurane increased an outwardly rectifying potassium current in ventral horn neurons of the Ndufs4(KO) mouse at a concentration much lower than in controls. Noncholinergic neurons in the spinal cord ventral horn mediated the effect. Presynaptic functions in Ndufs4(KO) slices were not hypersensitive to isoflurane. These data link anesthetic sensitivity, mitochondrial function, and postsynaptic channel activity. EDITOR’S PERSPECTIVE
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Lemon RN, Baker SN, Kraskov A. Classification of Cortical Neurons by Spike Shape and the Identification of Pyramidal Neurons. Cereb Cortex 2021; 31:5131-5138. [PMID: 34117760 PMCID: PMC8491674 DOI: 10.1093/cercor/bhab147] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Many investigators who make extracellular recordings from populations of cortical neurons are now using spike shape parameters, and particularly spike duration, as a means of classifying different neuronal sub-types. Because of the nature of the experimental approach, particularly that involving nonhuman primates, it is very difficult to validate directly which spike characteristics belong to particular types of pyramidal neurons and interneurons, as defined by modern histological approaches. This commentary looks at the way antidromic identification of pyramidal cells projecting to different targets, and in particular, pyramidal tract neurons (PTN), can inform the utility of spike width classification. Spike duration may provide clues to a diversity of function across the pyramidal cell population, and also highlights important differences that exist across species. Our studies suggest that further electrophysiological and optogenetic approaches are needed to validate spike duration as a means of cell classification and to relate this to well-established histological differences in neocortical cell types.
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Affiliation(s)
- Roger N Lemon
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK
| | - Stuart N Baker
- Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Alexander Kraskov
- Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
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Nango H, Kosuge Y. Present State and Future Perspectives of Prostaglandins as a Differentiation Factor in Motor Neurons. Cell Mol Neurobiol 2021; 42:2097-2108. [PMID: 34032949 DOI: 10.1007/s10571-021-01104-4] [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: 01/26/2021] [Accepted: 05/18/2021] [Indexed: 11/28/2022]
Abstract
Spinal motor neurons have the longest axons that innervate the skeletal muscles of the central nervous system. Motor neuron diseases caused by spinal motor neuron cell death are incurable due to the unique and irreplaceable nature of their neural circuits. Understanding the mechanisms of neurogenesis, neuritogenesis, and synaptogenesis in motor neurons will allow investigators to develop new in vitro models and regenerative therapies for motor neuron diseases. In particular, small molecules can directly reprogram and convert into neural stem cells and neurons, and promote neuron-like cell differentiation. Prostaglandins are known to have a role in the differentiation and tissue regeneration of several cell types and organs. However, the involvement of prostaglandins in the differentiation of motor neurons from neural stem cells is poorly understood. The general cell line used in research on motor neuron diseases is the mouse neuroblastoma and spinal motor neuron fusion cell line NSC-34. Recently, our laboratory reported that prostaglandin E2 and prostaglandin D2 enhanced the conversion of NSC-34 cells into motor neuron-like cells with neurite outgrowth. Moreover, we found that prostaglandin E2-differentiated NSC-34 cells had physiological and electrophysiological properties of mature motor neurons. In this review article, we provide contemporary evidence on the effects of prostaglandins, particularly prostaglandin E2 and prostaglandin D2, on differentiation and neural conversion. We also discuss the potential of prostaglandins as candidates for the development of new therapeutic drugs for motor neuron diseases.
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Affiliation(s)
- Hiroshi Nango
- Laboratory of Pharmacology, School of Pharmacy, Nihon University, 7-7-1 Narashinodai, Funabashi-shi, Chiba, 274-8555, Japan
| | - Yasuhiro Kosuge
- Laboratory of Pharmacology, School of Pharmacy, Nihon University, 7-7-1 Narashinodai, Funabashi-shi, Chiba, 274-8555, Japan.
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Fan W, Sdrulla AD. Differential modulation of excitatory and inhibitory populations of superficial dorsal horn neurons in lumbar spinal cord by Aβ-fiber electrical stimulation. Pain 2021; 161:1650-1660. [PMID: 32068665 DOI: 10.1097/j.pain.0000000000001836] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Activation of Aβ-fibers is fundamental to numerous analgesic therapies, yet its effects on dorsal horn neuronal activity remain unclear. We used multiphoton microscopy of the genetically encoded calcium indicator GCaMP6s to characterize the effects of Aβ-fiber electrical stimulation (Aβ-ES) on neural activity. Specifically, we quantified somatic responses evoked by C-fiber intensity stimulation before and after a 10-minute train of dorsal root Aβ-ES in superficial dorsal horn (SDH) neurons, in mouse lumbar spinal cord. Aβ-ES did not alter C-fiber-evoked activity when GCaMP6s was virally expressed in all neurons, in an intact lumbar spinal cord preparation. However, when we restricted the expression of GCaMP6s to excitatory or inhibitory populations, we observed that Aβ-ES modestly potentiated evoked activity of excitatory neurons and depressed that of inhibitory neurons. Aβ-ES had no significant effects in a slice preparation in either SDH population. A larger proportion of SDH neurons was activated by Aβ-ES when delivered at a root rostral or caudal to the segment where the imaging and C-fiber intensity stimulation occurred. Aβ-ES effects on excitatory and inhibitory populations depended on the root used. Our findings suggest that Aβ-ES differentially modulates lumbar spinal cord SDH populations in a cell type- and input-specific manner. Furthermore, they underscore the importance of the Aβ-ES delivery site, suggesting that Aβ stimulation at a segment adjacent to where the pain is may improve analgesic efficacy.
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Affiliation(s)
- Wei Fan
- Department of Anesthesiology and Perioperative Medicine, Oregon Health & Science University, Portland, OR, United States
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Mousa MH, Elbasiouny SM. Estimating the effects of slicing on the electrophysiological properties of spinal motoneurons under normal and disease conditions. J Neurophysiol 2021; 125:1450-1467. [PMID: 33689515 PMCID: PMC8282222 DOI: 10.1152/jn.00543.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 03/07/2021] [Accepted: 03/08/2021] [Indexed: 11/22/2022] Open
Abstract
Although slice recordings from spinal motoneurons (MNs) are being widely used, the effects of slicing on the measured MN electrical properties under normal and disease conditions have not been assessed. Using high-fidelity cell models of neonatal wild-type (WT) and superoxide dismutase-1 (SOD) cells, we examined the effects of slice thickness, soma position within the slice, and slice orientation to estimate the error induced in measured MN electrical properties from spinal slices. Our results show that most MN electrical properties are not adversely affected by slicing, except for cell time constant, cell capacitance, and Ca2+ persistent inward current (PIC), which all exhibited large errors, regardless of the slice condition. Among the examined factors, soma position within the slice appears to be the strongest factor in influencing the magnitude of error in measured MN electrical properties. Transverse slices appear to have the least impact on measured MN electrical properties. Surprisingly, and despite their anatomical enlargement, we found that G85R-SOD MNs experience similar error in their measured electrical properties to those of WT MNs, but their errors are more sensitive to the soma position within the slice than WT MNs. Unless in thick and symmetrical slices, slicing appears to reduce motoneuron type differences. Accordingly, slice studies should attempt to record from MNs at the slice center to avoid large and inconsistent errors in measured cell properties and have valid cell measurements' comparisons. Our results, therefore, offer information that would enhance the rigor of MN electrophysiological data measured from the slice preparation under normal and disease conditions.NEW & NOTEWORTHY Although slice recordings from motoneurons are being widely used, the effects of slicing on the measured motoneuron electrical properties under normal and disease conditions have not been assessed. Using high-fidelity cell models of neonatal WT and SOD cells, we examined the effects of slice thickness, soma position within the slice, and slice orientation. Our results offer information that enhances the rigor of MN electrophysiological data measured from the slice preparation under normal and disease conditions.
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Affiliation(s)
- Mohamed H Mousa
- Department of Biomedical, Industrial and Human Factors Engineering, College of Engineering and Computer Science, Wright State University, Dayton, Ohio
| | - Sherif M Elbasiouny
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine and College of Science and Mathematics, Wright State University, Dayton, Ohio
- Department of Biomedical, Industrial and Human Factors Engineering, College of Engineering and Computer Science, Wright State University, Dayton, Ohio
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Li Y, Su S, Yu J, Peng M, Wan S, Ke C. Electrophysiological Properties of Substantia Gelatinosa Neurons in the Preparation of a Slice of Middle-Aged Rat Spinal Cord. Front Aging Neurosci 2021; 13:640265. [PMID: 33776744 PMCID: PMC7987937 DOI: 10.3389/fnagi.2021.640265] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Accepted: 02/08/2021] [Indexed: 11/29/2022] Open
Abstract
A patch-clamp recording in slices generated from the brain or the spinal cord has facilitated the exploration of neuronal circuits and the molecular mechanisms underlying neurological disorders. However, the rodents that are used to generate the spinal cord slices in previous studies involving a patch-clamp recording have been limited to those in the juvenile or adolescent stage. Here, we applied an N-methyl-D-glucamine HCl (NMDG-HCl) solution that enabled the patch-clamp recordings to be performed on the superficial dorsal horn neurons in the slices derived from middle-aged rats. The success rate of stable recordings from substantia gelatinosa (SG) neurons was 34.6% (90/260). When stimulated with long current pulses, 43.3% (39/90) of the neurons presented a tonic-firing pattern, which was considered to represent γ-aminobutyric acid-ergic (GABAergic) signals. Presumptive glutamatergic neurons presented 38.9% (35/90) delayed and 8.3% (7/90) single-spike patterns. The intrinsic membrane properties of both the neuron types were similar but delayed (glutamatergic) neurons appeared to be more excitable as indicated by the decreased latency and rheobase values of the action potential compared with those of tonic (GABAergic) neurons. Furthermore, the glutamatergic neurons were integrated, which receive more excitatory synaptic transmission. We demonstrated that the NMDG-HCl cutting solution could be used to prepare the spinal cord slices of middle-aged rodents for the patch-clamp recording. In combination with other techniques, this preparation method might permit the further study of the functions of the spinal cord in the pathological processes that occur in aging-associated diseases.
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Affiliation(s)
- Yang Li
- Hubei Key Laboratory of Embryonic Stem Cell Research, Department of Anesthesiology, Institute of Anesthesiology & Pain (IAP), Taihe Hospital, Hubei University of Medicine, Shiyan, China
| | - Shanchu Su
- Hubei Key Laboratory of Embryonic Stem Cell Research, Department of Anesthesiology, Institute of Anesthesiology & Pain (IAP), Taihe Hospital, Hubei University of Medicine, Shiyan, China
| | - Jiaqi Yu
- Hubei Key Laboratory of Embryonic Stem Cell Research, Department of Anesthesiology, Institute of Anesthesiology & Pain (IAP), Taihe Hospital, Hubei University of Medicine, Shiyan, China
| | - Minjing Peng
- Hubei Key Laboratory of Embryonic Stem Cell Research, Department of Anesthesiology, Institute of Anesthesiology & Pain (IAP), Taihe Hospital, Hubei University of Medicine, Shiyan, China
| | - Shengjun Wan
- Hubei Key Laboratory of Embryonic Stem Cell Research, Department of Anesthesiology, Institute of Anesthesiology & Pain (IAP), Taihe Hospital, Hubei University of Medicine, Shiyan, China
| | - Changbin Ke
- Hubei Key Laboratory of Embryonic Stem Cell Research, Department of Anesthesiology, Institute of Anesthesiology & Pain (IAP), Taihe Hospital, Hubei University of Medicine, Shiyan, China
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Huh S, Heckman CJ, Manuel M. Time Course of Alterations in Adult Spinal Motoneuron Properties in the SOD1(G93A) Mouse Model of ALS. eNeuro 2021; 8:ENEURO.0378-20.2021. [PMID: 33632815 PMCID: PMC8009670 DOI: 10.1523/eneuro.0378-20.2021] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 01/25/2021] [Accepted: 01/26/2021] [Indexed: 01/02/2023] Open
Abstract
Although amyotrophic lateral sclerosis (ALS) is an adult-onset neurodegenerative disease, motoneuron electrical properties are already altered during embryonic development. Motoneurons must therefore exhibit a remarkable capacity for homeostatic regulation to maintain a normal motor output for most of the life of the patient. In the present article, we demonstrate how maintaining homeostasis could come at a very high cost. We studied the excitability of spinal motoneurons from young adult SOD1(G93A) mice to end-stage. Initially, homeostasis is highly successful in maintaining their overall excitability. This initial success, however, is achieved by pushing some cells far above the normal range of passive and active conductances. As the disease progresses, both passive and active conductances shrink below normal values in the surviving cells. This shrinkage may thus promote survival, implying the previously large values contribute to degeneration. These results support the hypothesis that motoneuronal homeostasis may be "hypervigilant" in ALS and a source of accumulating stress.
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Affiliation(s)
- Seoan Huh
- Department of Physiology, Northwestern University, Feinberg School of Medicine, Chicago 60611, IL
| | - Charles J Heckman
- Department of Physiology, Northwestern University, Feinberg School of Medicine, Chicago 60611, IL
- Department of Physical Medicine and Rehabilitation, Northwestern University, Feinberg School of Medicine, Chicago 60611, IL
- Department of Physical Therapy and Human Movement Science, Northwestern University, Feinberg School of Medicine, Chicago 60611, IL
| | - Marin Manuel
- Department of Physiology, Northwestern University, Feinberg School of Medicine, Chicago 60611, IL
- Université de Paris, Saints-Pères Paris Institute for the Neurosciences (SPPIN), Centre National de la Recherche Scientifique, Paris 75006, France
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Abstract
The muscle spindle is an important sense organ for motor control and proprioception. Specialized intrafusal fibers are innervated by both stretch sensitive afferents and γ motor neurons that control the length of the spindle and tune the sensitivity of the muscle spindle afferents to both dynamic movement and static length. γ motor neurons share many similarities with other skeletal motor neurons, making it challenging to identify and specifically record or stimulate them. This short review will discuss recent advances in genetic and molecular biology techniques, electrophysiological recording, optical imaging, computer modelling, and stem cell culture techniques that have the potential to help answer important questions about fusimotor function in motor control and disease.
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Smith CC, Brownstone RM. Spinal motoneuron firing properties mature from rostral to caudal during postnatal development of the mouse. J Physiol 2020; 598:5467-5485. [PMID: 32851667 PMCID: PMC8436765 DOI: 10.1113/jp280274] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 08/24/2020] [Indexed: 12/16/2022] Open
Abstract
Key points Many mammals are born with immature motor systems that develop through a critical period of postnatal development. In rodents, postnatal maturation of movement occurs from rostral to caudal, correlating with maturation of descending supraspinal and local spinal circuits. We asked whether development of fundamental electrophysiological properties of spinal motoneurons follows the same rostro‐caudal sequence. We show that in both regions, repetitive firing parameters increase and excitability decreases with development; however, these characteristics mature earlier in cervical motoneurons. We suggest that in addition to autonomous mechanisms, motoneuron development depends on activity resulting from their circuit milieu.
Abstract Altricial mammals are born with immature nervous systems comprised of circuits that do not yet have the neuronal properties and connectivity required to produce future behaviours. During the critical period of postnatal development, neuronal properties are tuned to participate in functional circuits. In rodents, cervical motoneurons are born prior to lumbar motoneurons, and spinal cord development follows a sequential rostro‐caudal pattern. Here we asked whether birth order is reflected in the postnatal development of electrophysiological properties. We show that motoneurons of both regions have similar properties at birth and follow the same developmental profile, with maximal firing increasing and excitability decreasing into the third postnatal week. However, these maturative processes occur in cervical motoneurons prior to lumbar motoneurons, correlating with the maturation of premotor descending and local spinal systems. These results suggest that motoneuron properties do not mature by cell autonomous mechanisms alone, but also depend on developing premotor circuits. Many mammals are born with immature motor systems that develop through a critical period of postnatal development. In rodents, postnatal maturation of movement occurs from rostral to caudal, correlating with maturation of descending supraspinal and local spinal circuits. We asked whether development of fundamental electrophysiological properties of spinal motoneurons follows the same rostro‐caudal sequence. We show that in both regions, repetitive firing parameters increase and excitability decreases with development; however, these characteristics mature earlier in cervical motoneurons. We suggest that in addition to autonomous mechanisms, motoneuron development depends on activity resulting from their circuit milieu.
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Affiliation(s)
- Calvin C Smith
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK
| | - Robert M Brownstone
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK
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Ceto S, Sekiguchi KJ, Takashima Y, Nimmerjahn A, Tuszynski MH. Neural Stem Cell Grafts Form Extensive Synaptic Networks that Integrate with Host Circuits after Spinal Cord Injury. Cell Stem Cell 2020; 27:430-440.e5. [PMID: 32758426 DOI: 10.1016/j.stem.2020.07.007] [Citation(s) in RCA: 90] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 05/11/2020] [Accepted: 07/08/2020] [Indexed: 02/06/2023]
Abstract
Neural stem/progenitor cell (NSPC) grafts can integrate into sites of spinal cord injury (SCI) and generate neuronal relays across lesions that can provide functional benefit. To determine if and how grafts become synaptically organized and connect with host systems, we performed calcium imaging of NSPC grafts in SCI sites in vivo and in adult spinal cord slices. NSPC grafts organize into localized and spontaneously active synaptic networks. Optogenetic stimulation of host corticospinal tract axons regenerating into grafts elicited distinct and segregated neuronal network responses throughout the graft. Moreover, optogenetic stimulation of graft-derived axons extending from the graft into the denervated spinal cord also triggered local host neuronal network responses. In vivo imaging revealed that behavioral stimulation likewise elicited focal synaptic responses within grafts. Thus neural progenitor grafts can form functional synaptic subnetworks whose activity patterns resemble intact spinal cord.
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Affiliation(s)
- Steven Ceto
- Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093, USA; Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla, CA 92093, USA; Veterans Administration Medical Center, San Diego, La Jolla, CA 92161, USA.
| | - Kohei J Sekiguchi
- Waitt Advanced Biophotonics Center, Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - Yoshio Takashima
- Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093, USA; Veterans Administration Medical Center, San Diego, La Jolla, CA 92161, USA
| | - Axel Nimmerjahn
- Waitt Advanced Biophotonics Center, Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - Mark H Tuszynski
- Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093, USA; Veterans Administration Medical Center, San Diego, La Jolla, CA 92161, USA.
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Nango H, Kosuge Y, Sato M, Shibukawa Y, Aono Y, Saigusa T, Ito Y, Ishige K. Highly Efficient Conversion of Motor Neuron-Like NSC-34 Cells into Functional Motor Neurons by Prostaglandin E 2. Cells 2020; 9:cells9071741. [PMID: 32708195 PMCID: PMC7409148 DOI: 10.3390/cells9071741] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 07/10/2020] [Accepted: 07/20/2020] [Indexed: 12/19/2022] Open
Abstract
Motor neuron diseases are a group of progressive neurological disorders that degenerate motor neurons. The neuroblastoma × spinal cord hybrid cell line NSC-34 is widely used as an experimental model in studies of motor neuron diseases. However, the differentiation efficiency of NSC-34 cells to neurons is not always sufficient. We have found that prostaglandin E2 (PGE2) induces morphological differentiation in NSC-34 cells. The present study investigated the functional properties of PGE2-differentiated NSC-34 cells. Retinoic acid (RA), a widely-used agent inducing cell differentiation, facilitated neuritogenesis, which peaked on day 7, whereas PGE2-induced neuritogenesis took only 2 days to reach the same level. Whole-cell patch-clamp recordings showed that the current threshold of PGE2-treated cell action potentials was lower than that of RA-treated cells. PGE2 and RA increased the protein expression levels of neuronal differentiation markers, microtubule-associated protein 2c and synaptophysin, and to the same extent, motor neuron-specific markers HB9 and Islet-1. On the other hand, protein levels of choline acetyltransferase and basal release of acetylcholine in PGE2-treated cells were higher than in RA-treated cells. These results suggest that PGE2 is a rapid and efficient differentiation-inducing factor for the preparation of functionally mature motor neurons from NSC-34 cells.
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Affiliation(s)
- Hiroshi Nango
- Laboratory of Pharmacology, School of Pharmacy, Nihon University, 7-7-1 Narashinodai, Funabashi-shi, Chiba 274-8555, Japan; (H.N.); (Y.I.)
| | - Yasuhiro Kosuge
- Laboratory of Pharmacology, School of Pharmacy, Nihon University, 7-7-1 Narashinodai, Funabashi-shi, Chiba 274-8555, Japan; (H.N.); (Y.I.)
- Correspondence: (Y.K.); (K.I.); Tel.: +81-47-465-4027 (Y.K.)
| | - Masaki Sato
- Department of Physiology, Tokyo Dental College, 2-9-18 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan; (M.S.); (Y.S.)
- Department of Biology Tokyo Dental College, 2-9-7 Kandasurugadai, Chiyoda-ku, Tokyo 101-0062, Japan
| | - Yoshiyuki Shibukawa
- Department of Physiology, Tokyo Dental College, 2-9-18 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan; (M.S.); (Y.S.)
| | - Yuri Aono
- Department of Pharmacology, School of Dentistry at Matsudo, Nihon University, 2-870-1 Sakaechonishi, Matsudo-shi, Chiba 271-8587, Japan; (Y.A.); (T.S.)
| | - Tadashi Saigusa
- Department of Pharmacology, School of Dentistry at Matsudo, Nihon University, 2-870-1 Sakaechonishi, Matsudo-shi, Chiba 271-8587, Japan; (Y.A.); (T.S.)
| | - Yoshihisa Ito
- Laboratory of Pharmacology, School of Pharmacy, Nihon University, 7-7-1 Narashinodai, Funabashi-shi, Chiba 274-8555, Japan; (H.N.); (Y.I.)
- Pharmacy Education Center, Yokohama University of Pharmacy, 601 Matanocho, Totuka-ku, Yokohama 245-0066, Japan
| | - Kumiko Ishige
- Laboratory of Pharmacology, School of Pharmacy, Nihon University, 7-7-1 Narashinodai, Funabashi-shi, Chiba 274-8555, Japan; (H.N.); (Y.I.)
- Correspondence: (Y.K.); (K.I.); Tel.: +81-47-465-4027 (Y.K.)
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Adams JC, Bell PD, Bodine SC, Brooks HL, Bunnett N, Joe B, Keehan KH, Kleyman TR, Marette A, Morty RE, Ramírez JM, Thomsen MB, Yates BJ, Zucker IH. An American Physiological Society cross-journal Call for Papers on "Deconstructing Organs: Single-Cell Analyses, Decellularized Organs, Organoids, and Organ-on-a-Chip Models". Am J Physiol Lung Cell Mol Physiol 2020; 319:L266-L272. [PMID: 32609556 PMCID: PMC7473938 DOI: 10.1152/ajplung.00311.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Affiliation(s)
- Josephine C Adams
- School of Biochemistry, Faculty of Life Sciences, University of Bristol, Bristol, United Kingdom
| | - P Darwin Bell
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Sue C Bodine
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa
| | - Heddwen L Brooks
- Department of Physiology, University of Arizona College of Medicine, Tucson, Arizona
| | - Nigel Bunnett
- Department of Molecular Pathobiology, New York University, New York, New York
| | - Bina Joe
- Department of Physiology and Pharmacology, University of Toledo College of Medicine and Life Sciences, Toledo, Ohio.,Center for Hypertension and Personalized Medicine, University of Toledo College of Medicine and Life Sciences, Toledo, Ohio
| | | | - Thomas R Kleyman
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania.,Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania.,Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - André Marette
- Department of Medicine, Faculty of Medicine, Cardiology Axis of the Québec Heart and Lung Institute, Hôpital Laval, Quebec City, Quebec, Canada.,Institute of Nutrition and Functional Foods, Laval University, Quebec City, Quebec, Canada
| | - Rory E Morty
- Department of Lung Development and Remodelling, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany.,Department of Internal Medicine (Pulmonology), University of Giessen and Marburg Lung Center, Justus Liebig University Giessen, member of the German Center for Lung Research (DZL), Giessen, Germany
| | - Jan-Marino Ramírez
- Department of Neurological Surgery, University of Washington Medical Center, Seattle, Washington.,Center on Human Development and Disability, University of Washington, Seattle, Washington.,Center for Integrative Brain Research, Seattle Children's Research Institute, University of Washington, Seattle, Washington
| | - Morten B Thomsen
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Bill J Yates
- Department of Otolaryngology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Irving H Zucker
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, Nebraska
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24
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Flint JJ, Menon K, Hansen B, Forder J, Blackband SJ. Visualization of live, mammalian neurons during Kainate-infusion using magnetic resonance microscopy. Neuroimage 2020; 219:116997. [PMID: 32492508 PMCID: PMC7510773 DOI: 10.1016/j.neuroimage.2020.116997] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 05/25/2020] [Accepted: 05/26/2020] [Indexed: 01/30/2023] Open
Abstract
Since its first description and development in the late 20th century, diffusion magnetic resonance imaging (dMRI) has proven useful in describing the microstructural details of biological tissues. Signal generated from the protons of water molecules undergoing Brownian motion produces contrast based on the varied diffusivity of tissue types. Images employing diffusion contrast were first used to describe the diffusion characteristics of tissues, later used to describe the fiber orientations of white matter through tractography, and most recently proposed as a functional contrast method capable of delineating neuronal firing in the active brain. Thanks to the molecular origins of its signal source, diffusion contrast is inherently useful at describing features of the microenvironment; however, limitations in achievable resolution in magnetic resonance imaging (MRI) scans precluded direct visualization of tissue microstructure for decades following MRI's inception as an imaging modality. Even after advancements in MRI hardware had permitted the visualization of mammalian cells, these specialized systems could only accommodate fixed specimens that prohibited the observation and characterization of physiological processes. The goal of the current study was to visualize cellular structure and investigate the subcellular origins of the functional diffusion contrast mechanism (DfMRI) in living, mammalian tissue explants. Using a combination of ultra-high field spectrometers, micro radio frequency (RF) coils, and an MRI-compatible superfusion device, we are able to report the first live, mammalian cells-α-motor neurons-visualized with magnetic resonance microscopy (MRM). We are also able to report changes in the apparent diffusion of the stratum oriens within the hippocampus-a layer comprised primarily of pyramidal cell axons and basal dendrites-and the spinal cord's ventral horn following exposure to kainate.
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Affiliation(s)
- Jeremy J Flint
- Department of Neuroscience, University of Florida, Gainesville, FL, USA; McKnight Brain Institute, University of Florida, Gainesville, FL, USA.
| | - Kannan Menon
- Department of Biomedical Engineering, University of Florida, Gainesville, FL, USA; McKnight Brain Institute, University of Florida, Gainesville, FL, USA
| | - Brian Hansen
- Center of Functionally Integrative Neuroscience, Aarhus University, Denmark
| | - John Forder
- Department of Biomedical Engineering, University of Florida, Gainesville, FL, USA; Department of Radiology, University of Florida, Gainesville, FL, USA; McKnight Brain Institute, University of Florida, Gainesville, FL, USA; National High Magnetic Field Laboratory, Tallahassee, FL, USA
| | - Stephen J Blackband
- Department of Neuroscience, University of Florida, Gainesville, FL, USA; McKnight Brain Institute, University of Florida, Gainesville, FL, USA; Center for Structural Biology, University of Florida, Gainesville, FL, USA; National High Magnetic Field Laboratory, Tallahassee, FL, USA
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25
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Rotterman TM, Alvarez FJ. Microglia Dynamics and Interactions with Motoneurons Axotomized After Nerve Injuries Revealed By Two-Photon Imaging. Sci Rep 2020; 10:8648. [PMID: 32457369 PMCID: PMC7250868 DOI: 10.1038/s41598-020-65363-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 05/01/2020] [Indexed: 01/08/2023] Open
Abstract
The significance of activated microglia around motoneurons axotomized after nerve injuries has been intensely debated. In particular, whether microglia become phagocytic is controversial. To resolve these issues we directly observed microglia behaviors with two-photon microscopy in ex vivo spinal cord slices from CX3CR1-GFP mice complemented with confocal analyses of CD68 protein. Axotomized motoneurons were retrogradely-labeled from muscle before nerve injuries. Microglia behaviors close to axotomized motoneurons greatly differ from those within uninjured motor pools. They develop a phagocytic phenotype as early as 3 days after injury, characterized by frequent phagocytic cups, high phagosome content and CD68 upregulation. Interactions between microglia and motoneurons changed with time after axotomy. Microglia first extend processes that end in phagocytic cups at the motoneuron surface, then they closely attach to the motoneuron while extending filopodia over the cell body. Confocal 3D analyses revealed increased microglia coverage of the motoneuron cell body surface with time after injury and the presence of CD68 granules in microglia surfaces opposed to motoneurons. Some microglia formed macroclusters associated with dying motoneurons. Microglia in these clusters display the highest CD68 expression and associate with cytotoxic T-cells. These observations are discussed in relation to current theories on microglia function around axotomized motoneurons.
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Affiliation(s)
- Travis M Rotterman
- Department of Physiology, Emory University, Atlanta, GA, 30322, United States of America.,School of Biological Sciences, Georgia Tech, Atlanta, GA, 30318, United States of America
| | - Francisco J Alvarez
- Department of Physiology, Emory University, Atlanta, GA, 30322, United States of America.
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26
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Sceniak MP, Spitsbergen JB, Sabo SL, Yuan Y, Atchison WD. Acute neurotoxicant exposure induces hyperexcitability in mouse lumbar spinal motor neurons. J Neurophysiol 2020; 123:1448-1459. [PMID: 32159428 DOI: 10.1152/jn.00775.2019] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Spinal motor neurons (MNs) are susceptible to glutamatergic excitotoxicity, an effect associated with lumbar MN degeneration in amyotrophic lateral sclerosis (ALS). MN susceptibility to environmental toxicant exposure, one prospective contributor to sporadic ALS, has not been systematically studied. The goal of this study was to test the ability of a well-known environmental neurotoxicant to induce hyperexcitability in mouse lumbar MNs. Methylmercury (MeHg) causes neurotoxicity through mechanisms involving elevated intracellular Ca2+ concentration ([Ca2+]i), a hallmark of excitotoxicity. We tested whether acute exposure to MeHg induces hyperexcitability in MNs by altering synaptic transmission, using whole cell patch-clamp recordings of lumbar spinal MNs in vitro. Acute MeHg exposure (20 μM) led to an increase in the frequency of both spontaneous excitatory postsynaptic currents (EPSCs) and miniature EPSCs. The frequency of inhibitory postsynaptic currents (IPSCs) was also increased by MeHg. Action potential firing rates, both spontaneous and evoked, were increased by MeHg, despite increases in both EPSCs and IPSCs, indicating a shift toward hyperexcitability. Also consistent with hyperexcitability, fluo 4-AM microfluorimetry indicated that MeHg exposure induced an increase in [Ca2+]i. Spinal cord hyperexcitability is partially mediated by Ca2+-permeable AMPA receptors, as MeHg-dependent increases in EPSCs were blocked by 1-napthyl spermine. Therefore, spinal MNs appear highly susceptible to MeHg exposure, leading to significant increases in spontaneous network excitability and disruption of normal function. Prolonged hyperexcitability could lead to eventual neurodegeneration and loss of motor function as observed in spinal cord after MeHg exposure in vivo and may contribute to MeHg-induced acceleration of ALS symptoms.NEW & NOTEWORTHY Spinal motor neurons (MN) are susceptible to glutamatergic excitotoxicity, an effect associated with lumbar MN degeneration in amyotrophic lateral sclerosis (ALS). This study investigated MN susceptibility to environmental toxicant exposure, one prospective contributor to sporadic ALS. Spinal MNs appear highly susceptible to methylmercury exposure, leading to significant increases in spontaneous network excitability and disruption of normal function. Prolonged hyperexcitability could lead to neurodegeneration and loss of motor function as observed in ALS spinal cord symptoms.
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Affiliation(s)
- Michael P Sceniak
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan.,Department of Biology, Central Michigan University, Mount Pleasant, Michigan
| | - Jake B Spitsbergen
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan
| | - Shasta L Sabo
- Department of Biology, Central Michigan University, Mount Pleasant, Michigan
| | - Yukun Yuan
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan
| | - William D Atchison
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan
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27
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Three-week treadmill training changes the electrophysiological properties of spinal interneurons in the mice. Exp Brain Res 2019; 237:2925-2938. [PMID: 31494682 DOI: 10.1007/s00221-019-05647-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2019] [Accepted: 09/03/2019] [Indexed: 12/20/2022]
Abstract
It was shown in previous studies that endurance training enhanced excitability of rat spinal motoneurons. However, the influence of the training on the spinal interneurons remains unclear. In this study, we investigated the training effects on spinal interneurons in dorsal and ventromedial area in mice (P42-P50). The electrophysiological properties of the interneurons were recorded from spinal cord slices (T13-L6) by whole-cell patch-clamp recording. The interneurons could be classified into three types based on their response to step currents: single spike (type 1), phasic firing (type 2), and tonic firing (type 3) in both control and trained mice. Interneurons collected from control mice possessed rheobase of 11.3 ± 6.0 pA and voltage threshold (Vth) of - 37.3 ± 4.7 mV. Treadmill training reduced the rheobase by 4.8 ± 1.5 pA and Vth by 3.1 ± 1.2 mV (P < 0.05). Furthermore, the training effects were dependent on the distribution and types of the interneurons. Treadmill training hyperpolarized Vth and decreased rheobase in ventromedial interneurons, while the significant change was observed only in the action potation height of the interneurons in dorsal horn. Treadmill training also hyperpolarized Vth and increased input resistance in type 3 interneurons, but none of these changes was shown in type 1 and 2 interneurons. Bath application of 5-HT (10-20 μM) increased the neuronal excitability in both control and trained mice. Serotonin had similar effect on membrane properties of the interneurons collected from both groups. This study suggested that treadmill training increased excitability of spinal interneurons of the mice and thus would make the spinal motor system easier to generate locomotion.
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28
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Petrovic A, Veeraraghavan P, Olivieri D, Nistri A, Jurcic N, Mladinic M. Loss of inhibitory synapses causes locomotor network dysfunction of the rat spinal cord during prolonged maintenance in vitro. Brain Res 2018; 1710:8-21. [PMID: 30578767 DOI: 10.1016/j.brainres.2018.12.029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 12/06/2018] [Accepted: 12/19/2018] [Indexed: 12/17/2022]
Abstract
The isolated spinal cord of the neonatal rat is widely employed to clarify the basic mechanisms of network development or the early phase of degeneration after injury. Nevertheless, this preparation survives in Krebs solution up to 24 h only, making it desirable to explore approaches to extend its survival for longitudinal studies. The present report shows that culturing the spinal cord in oxygenated enriched Basal Medium Eagle (BME) provided excellent preservation of neurons (including motoneurons), glia and primary afferents (including dorsal root ganglia) for up to 72 h. Using DMEM medium was unsuccessful. Novel characteristics of spinal networks emerged with strong spontaneous activity, and deficit in fictive locomotion patterns with stereotypically slow cycles. Staining with markers for synaptic proteins synapsin 1 and synaptophysin showed thoroughly weaker signal after 3 days in vitro. Immunohistochemical staining of markers for glutamatergic and glycinergic neurons indicated significant reduction of the latter. Likewise, there was lower expression of the GABA-synthesizing enzyme GAD65. Thus, malfunction of locomotor networks appeared related to loss of inhibitory synapses. This phenomenon did not occur in analogous opossum preparations of the spinal cord kept in vitro. In conclusion, despite histological data suggesting that cultured spinal cords were undamaged (except for inhibitory biomarkers), electrophysiological data revealed important functional impairment. Thus, the downregulation of inhibitory synapses may account for the progressive hyperexcitability of rat spinal networks despite apparently normal histological appearance. Our observations may help to understand the basis of certain delayed effects of spinal injury like chronic pain and spasticity.
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Affiliation(s)
- Antonela Petrovic
- Neuroscience Department, International School for Advanced Studies (SISSA), Trieste, Italy; Department of Biotechnology, University of Rijeka, Rijeka, Croatia
| | | | - Dario Olivieri
- Neuroscience Department, International School for Advanced Studies (SISSA), Trieste, Italy
| | - Andrea Nistri
- Neuroscience Department, International School for Advanced Studies (SISSA), Trieste, Italy
| | - Nina Jurcic
- Neuroscience Department, International School for Advanced Studies (SISSA), Trieste, Italy
| | - Miranda Mladinic
- Neuroscience Department, International School for Advanced Studies (SISSA), Trieste, Italy; Department of Biotechnology, University of Rijeka, Rijeka, Croatia.
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29
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Manuel M, Zytnicki D. Molecular and electrophysiological properties of mouse motoneuron and motor unit subtypes. CURRENT OPINION IN PHYSIOLOGY 2018; 8:23-29. [PMID: 32551406 DOI: 10.1016/j.cophys.2018.11.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The field of motoneuron and motor unit physiology in mammals has deeply evolved the last decade thanks to the parallel development of mouse genetics and transcriptomic analysis and of in vivo mouse preparations that allow intracellular electrophysiological recordings of motoneurons. We review the efforts made to investigate the electrophysiological properties of the different functional subtypes of mouse motoneurons, to decipher the mosaic of molecular markers specifically expressed in each subtype, and to elucidate which of those factors drive the identity of motoneurons.
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Affiliation(s)
- Marin Manuel
- Center for Neurophysics, Physiology and Pathology, Paris Descartes University, CNRS UMR 8119, Paris, France
| | - Daniel Zytnicki
- Center for Neurophysics, Physiology and Pathology, Paris Descartes University, CNRS UMR 8119, Paris, France
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30
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Murabe N, Mori T, Fukuda S, Isoo N, Ohno T, Mizukami H, Ozawa K, Yoshimura Y, Sakurai M. Higher primate-like direct corticomotoneuronal connections are transiently formed in a juvenile subprimate mammal. Sci Rep 2018; 8:16536. [PMID: 30410053 PMCID: PMC6224497 DOI: 10.1038/s41598-018-34961-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 10/22/2018] [Indexed: 12/30/2022] Open
Abstract
The corticospinal (CS) tract emerged and evolved in mammals, and is essentially involved in voluntary movement. Over its phylogenesis, CS innervation gradually invaded to the ventral spinal cord, eventually making direct connections with spinal motoneurons (MNs) in higher primates. Despite its importance, our knowledge of the origin of the direct CS-MN connections is limited; in fact, there is controversy as to whether these connections occur in subprimate mammals, such as rodents. Here we studied the retrograde transsynaptic connection between cortical neurons and MNs in mice by labeling the cells with recombinant rabies virus. On postnatal day 14 (P14), we found that CS neurons make direct connections with cervical MNs innervating the forearm muscles. Direct connections were also detected electrophysiologically in whole cell recordings from identified MNs retrogradely-labeled from their target muscles and optogenetic CS stimulation. In contrast, few, if any, lumbar MNs innervating hindlimbs showed direct connections on P18. Moreover, the direct CS-MN connections observed on P14 were later eliminated. The transient CS-MN cells were distributed predominantly in the M1 and S1 areas. These findings provide insight into the ontogeny and phylogeny of the CS projection and appear to settle the controversy about direct CS-MN connections in subprimate mammals.
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Affiliation(s)
- Naoyuki Murabe
- Department of Physiology, Teikyo University School of Medicine, Tokyo, 173-8605, Japan
| | - Takuma Mori
- Division of Visual Information Processing, National Institute for Physiological Sciences, National Institutes for Natural Sciences, Okazaki, 444-8585, Japan.,Department of Molecular and Cellular Physiology, Institute of Medicine, Academic Assembly, Shinshu University, Nagano, 390-8621, Japan
| | - Satoshi Fukuda
- Department of Physiology, Teikyo University School of Medicine, Tokyo, 173-8605, Japan
| | - Noriko Isoo
- Department of Physiology, Teikyo University School of Medicine, Tokyo, 173-8605, Japan
| | - Takae Ohno
- Department of Physiology, Teikyo University School of Medicine, Tokyo, 173-8605, Japan
| | - Hiroaki Mizukami
- Division of Genetic Therapeutics, Jichi Medical University, Tochigi, 329-0498, Japan
| | - Keiya Ozawa
- Division of Genetic Therapeutics, Jichi Medical University, Tochigi, 329-0498, Japan.,Research Hospital, Institute of Medical Science, Tokyo University, Tokyo, 108-8639, Japan
| | - Yumiko Yoshimura
- Division of Visual Information Processing, National Institute for Physiological Sciences, National Institutes for Natural Sciences, Okazaki, 444-8585, Japan.,Department of Physiological Sciences, Graduate University for Advanced Studies, Okazaki, 444-8585, Japan
| | - Masaki Sakurai
- Department of Physiology, Teikyo University School of Medicine, Tokyo, 173-8605, Japan.
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31
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Kelley KW, Ben Haim L, Schirmer L, Tyzack GE, Tolman M, Miller JG, Tsai HH, Chang SM, Molofsky AV, Yang Y, Patani R, Lakatos A, Ullian EM, Rowitch DH. Kir4.1-Dependent Astrocyte-Fast Motor Neuron Interactions Are Required for Peak Strength. Neuron 2018; 98:306-319.e7. [PMID: 29606582 PMCID: PMC5919779 DOI: 10.1016/j.neuron.2018.03.010] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 11/08/2017] [Accepted: 03/05/2018] [Indexed: 12/11/2022]
Abstract
Diversified neurons are essential for sensorimotor function, but whether astrocytes become specialized to optimize circuit performance remains unclear. Large fast α-motor neurons (FαMNs) of spinal cord innervate fast-twitch muscles that generate peak strength. We report that ventral horn astrocytes express the inward-rectifying K+ channel Kir4.1 (a.k.a. Kcnj10) around MNs in a VGLUT1-dependent manner. Loss of astrocyte-encoded Kir4.1 selectively altered FαMN size and function and led to reduced peak strength. Overexpression of Kir4.1 in astrocytes was sufficient to increase MN size through activation of the PI3K/mTOR/pS6 pathway. Kir4.1 was downregulated cell autonomously in astrocytes derived from amyotrophic lateral sclerosis (ALS) patients with SOD1 mutation. However, astrocyte Kir4.1 was dispensable for FαMN survival even in the mutant SOD1 background. These findings show that astrocyte Kir4.1 is essential for maintenance of peak strength and suggest that Kir4.1 downregulation might uncouple symptoms of muscle weakness from MN cell death in diseases like ALS. Kir4.1 is upregulated in astrocytes around high-activity alpha motor neurons (MNs) Astrocyte Kir4.1 KO caused decreased peak strength without alpha MN loss ALS patient-derived astrocytes show cell-autonomous Kir4.1 downregulation Astrocyte Kir4.1 regulates MN size through PI3K/mTOR/pS6 activation
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Affiliation(s)
- Kevin W Kelley
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA; Departments of Pediatrics and Neurosurgery, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Lucile Ben Haim
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA; Departments of Pediatrics and Neurosurgery, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Lucas Schirmer
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA; Departments of Pediatrics and Neurosurgery, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Giulia E Tyzack
- Department of Molecular Neuroscience, Institute of Neurology, University College London, London WC1N 3BG, UK; The Francis Crick Institute, London NW1 1AT, UK
| | - Michaela Tolman
- Sackler School of Biomedical Sciences, Tufts University, Boston, MA 02111, USA
| | - John G Miller
- Department of Psychiatry, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Hui-Hsin Tsai
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA; Departments of Pediatrics and Neurosurgery, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Sandra M Chang
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA; Departments of Pediatrics and Neurosurgery, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Anna V Molofsky
- Department of Psychiatry, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Yongjie Yang
- Sackler School of Biomedical Sciences, Tufts University, Boston, MA 02111, USA
| | - Rickie Patani
- Department of Molecular Neuroscience, Institute of Neurology, University College London, London WC1N 3BG, UK; The Francis Crick Institute, London NW1 1AT, UK
| | - Andras Lakatos
- John van Geest Centre for Brain Repair and Department of Clinical Neurosciences, University of Cambridge, Cambridge CB20QQ, UK
| | - Erik M Ullian
- Department of Ophthalmology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - David H Rowitch
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA; Departments of Pediatrics and Neurosurgery, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Paediatrics and Wellcome Trust-MRC Cambridge Stem Cell Institute, University of Cambridge, Cambridge CB20QQ, UK.
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32
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Lamotte d'Incamps B, Bhumbra GS, Foster JD, Beato M, Ascher P. Segregation of glutamatergic and cholinergic transmission at the mixed motoneuron Renshaw cell synapse. Sci Rep 2017. [PMID: 28642492 PMCID: PMC5481398 DOI: 10.1038/s41598-017-04266-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In neonatal mice motoneurons excite Renshaw cells by releasing both acetylcholine (ACh) and glutamate. These two neurotransmitters activate two types of nicotinic receptors (nAChRs) (the homomeric α7 receptors and the heteromeric α*ß* receptors) as well as the two types of glutamate receptors (GluRs) (AMPARs and NMDARs). Using paired recordings, we confirm that a single motoneuron can release both transmitters on a single post-synaptic Renshaw cell. We then show that co-transmission is preserved in adult animals. Kinetic analysis of miniature EPSCs revealed quantal release of mixed events associating AMPARs and NMDARs, as well as α7 and α*ß* nAChRs, but no evidence was found for mEPSCs associating nAChRs with GluRs. Bayesian Quantal Analysis (BQA) of evoked EPSCs showed that the number of functional contacts on a single Renshaw cell is more than halved when the nicotinic receptors are blocked, confirming that the two neurotransmitters systems are segregated. Our observations can be explained if ACh and glutamate are released from common vesicles onto spatially segregated post-synaptic receptors clusters, but a pre-synaptic segregation of cholinergic and glutamatergic release sites is also possible.
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Affiliation(s)
- Boris Lamotte d'Incamps
- Center for Neurophysics, Physiology and Pathologies, CNRS UMR 8119, Université Paris Descartes, Paris, France.
| | - Gardave S Bhumbra
- Department of Neuroscience, Physiology and Pharmacology, UCL, Gower Street, London, United Kingdom
| | - Joshua D Foster
- Department of Neuroscience, Physiology and Pharmacology, UCL, Gower Street, London, United Kingdom
| | - Marco Beato
- Department of Neuroscience, Physiology and Pharmacology, UCL, Gower Street, London, United Kingdom
| | - Philippe Ascher
- Physiologie cérébrale, CNRS UMR 8118, Université Paris Descartes, Paris, France
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33
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Bowerman M, Salsac C, Bernard V, Soulard C, Dionne A, Coque E, Benlefki S, Hince P, Dion PA, Butler-Browne G, Camu W, Bouchard JP, Delpire E, Rouleau GA, Raoul C, Scamps F. KCC3 loss-of-function contributes to Andermann syndrome by inducing activity-dependent neuromuscular junction defects. Neurobiol Dis 2017. [PMID: 28647557 DOI: 10.1016/j.nbd.2017.06.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Loss-of-function mutations in the potassium-chloride cotransporter KCC3 lead to Andermann syndrome, a severe sensorimotor neuropathy characterized by areflexia, amyotrophy and locomotor abnormalities. The molecular events responsible for axonal loss remain poorly understood. Here, we establish that global or neuron-specific KCC3 loss-of-function in mice leads to early neuromuscular junction (NMJ) abnormalities and muscular atrophy that are consistent with the pre-synaptic neurotransmission defects observed in patients. KCC3 depletion does not modify chloride handling, but promotes an abnormal electrical activity among primary motoneurons and mislocalization of Na+/K+-ATPase α1 in spinal cord motoneurons. Moreover, the activity-targeting drug carbamazepine restores Na+/K+-ATPase α1 localization and reduces NMJ denervation in Slc12a6-/- mice. We here propose that abnormal motoneuron electrical activity contributes to the peripheral neuropathy observed in Andermann syndrome.
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Affiliation(s)
- Melissa Bowerman
- The Institute for Neurosciences of Montpellier, Inserm UMR1051, Saint Eloi Hospital, Montpellier, France; Université Montpellier 1 & 2, Montpellier, France; University of Oxford, Department of Physiology, Anatomy and Genetics, Oxford, UK
| | - Céline Salsac
- The Institute for Neurosciences of Montpellier, Inserm UMR1051, Saint Eloi Hospital, Montpellier, France
| | - Véronique Bernard
- Université Pierre et Marie Curie UM CR 18, Paris, France; CNRS UMR8246, Paris, France; Inserm U1130, Paris, France
| | - Claire Soulard
- The Institute for Neurosciences of Montpellier, Inserm UMR1051, Saint Eloi Hospital, Montpellier, France; Université Montpellier 1 & 2, Montpellier, France
| | - Annie Dionne
- Université Laval, Québec, Canada; CHU de Québec, Hôpital de l'Enfant-Jésus, Département des sciences neurologiques, Québec, Québec, Canada
| | - Emmanuelle Coque
- The Institute for Neurosciences of Montpellier, Inserm UMR1051, Saint Eloi Hospital, Montpellier, France; Université Montpellier 1 & 2, Montpellier, France
| | - Salim Benlefki
- The Institute for Neurosciences of Montpellier, Inserm UMR1051, Saint Eloi Hospital, Montpellier, France; Université Montpellier 1 & 2, Montpellier, France
| | - Pascale Hince
- Montreal Neurological Institute and Hospital, Department of Neurology and Neurosurgery, McGill University, Montreal, Québec, Canada; Department of Pathology and Cellular Biology, Université de Montréal, Montréal, Québec, Canada
| | - Patrick A Dion
- Montreal Neurological Institute and Hospital, Department of Neurology and Neurosurgery, McGill University, Montreal, Québec, Canada; Department of Pathology and Cellular Biology, Université de Montréal, Montréal, Québec, Canada
| | - Gillian Butler-Browne
- UM76, Institut de Myologie, Université Pierre et Marie Curie, Paris, France; U974, Inserm, Paris, France; UMR7215, CNRS, GH Pitié Salpêtrière, Paris, France
| | - William Camu
- The Institute for Neurosciences of Montpellier, Inserm UMR1051, Saint Eloi Hospital, Montpellier, France; Department of Neurology, ALS Reference Center, Gui-de-Chauliac Hospital, Montpellier, France
| | - Jean-Pierre Bouchard
- Université Laval, Québec, Canada; CHU de Québec, Hôpital de l'Enfant-Jésus, Département des sciences neurologiques, Québec, Québec, Canada
| | - Eric Delpire
- Vanderbilt University Medical Center, Vanderbilt, USA
| | - Guy A Rouleau
- Montreal Neurological Institute and Hospital, Department of Neurology and Neurosurgery, McGill University, Montreal, Québec, Canada
| | - Cédric Raoul
- The Institute for Neurosciences of Montpellier, Inserm UMR1051, Saint Eloi Hospital, Montpellier, France; Université Montpellier 1 & 2, Montpellier, France
| | - Frédérique Scamps
- The Institute for Neurosciences of Montpellier, Inserm UMR1051, Saint Eloi Hospital, Montpellier, France; Université Montpellier 1 & 2, Montpellier, France.
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Abstract
The adult decerebrate mouse model (a mouse with the cerebrum removed) enables the study of sensory-motor integration and motor output from the spinal cord for several hours without compromising these functions with anesthesia. For example, the decerebrate mouse is ideal for examining locomotor behavior using intracellular recording approaches, which would not be possible using current anesthetized preparations. This protocol describes the steps required to achieve a low-blood-loss decerebration in the mouse and approaches for recording signals from spinal cord neurons with a focus on motoneurons. The protocol also describes an example application for the protocol: the evocation of spontaneous and actively driven stepping, including optimization of these behaviors in decerebrate mice. The time taken to prepare the animal and perform a decerebration takes ∼2 h, and the mice are viable for up to 3-8 h, which is ample time to perform most short-term procedures. These protocols can be modified for those interested in cardiovascular or respiratory function in addition to motor function and can be performed by trainees with some previous experience in animal surgery.
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Garré JM, Yang G, Bukauskas FF, Bennett MVL. An Acute Mouse Spinal Cord Slice Preparation for Studying Glial Activation ex vivo. Bio Protoc 2017; 7:e2102. [PMID: 28503634 DOI: 10.21769/bioprotoc.2102] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
Pathological conditions such as amyotrophic lateral sclerosis, spinal cord injury and chronic pain are characterized by activation of astrocytes and microglia in spinal cord and have been modeled in rodents. In vivo imaging at cellular level in these animal models is limited due to the spinal cord's highly myelinated funiculi. The preparation of acute slices may offer an alternative and valuable strategy to collect structural and functional information in vitro from dorsal, lateral and ventral regions of spinal cord. Here, we describe a procedure for preparing acute slices from mouse spinal cord (Garré et al., 2016). This preparation should allow further understanding of how glial cells in spinal cord respond acutely to various inflammatory challenges.
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Affiliation(s)
- Juan Mauricio Garré
- Department of Anesthesiology, Perioperative Care and Pain Medicine, New York University School of Medicine, New York, USA
| | - Guang Yang
- Department of Anesthesiology, Perioperative Care and Pain Medicine, New York University School of Medicine, New York, USA
| | - Feliksas F Bukauskas
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, USA.,Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Michael V L Bennett
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, USA
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Mazzone GL, Veeraraghavan P, Gonzalez-Inchauspe C, Nistri A, Uchitel OD. ASIC channel inhibition enhances excitotoxic neuronal death in an in vitro model of spinal cord injury. Neuroscience 2016; 343:398-410. [PMID: 28003157 DOI: 10.1016/j.neuroscience.2016.12.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 11/23/2016] [Accepted: 12/04/2016] [Indexed: 01/06/2023]
Abstract
In the spinal cord high extracellular glutamate evokes excitotoxic damage with neuronal loss and severe locomotor impairment. During the cell dysfunction process, extracellular pH becomes acid and may activate acid-sensing ion channels (ASICs) which could be important contributors to neurodegenerative pathologies. Our previous studies have shown that transient application of the glutamate analog kainate (KA) evokes delayed excitotoxic death of spinal neurons, while white matter is mainly spared. The present goal was to enquire if ASIC channels modulated KA damage in relation to locomotor network function and cell death. Mouse spinal cord slices were treated with KA (0.01 or 0.1mM) for 1h, and then washed out for 24h prior to analysis. RT-PCR results showed that KA (at 0.01mM concentration that is near-threshold for damage) increased mRNA expression of ASIC1a, ASIC1b, ASIC2 and ASIC3, an effect reversed by the ASIC inhibitor 4',6-diamidino-2-phenylindole (DAPI). A KA neurotoxic dose (0.1mM) reduced ASIC1a and ASIC2 expression. Cell viability assays demonstrated KA-induced large damage in spinal slices from mice with ASIC1a gene ablation. Likewise, immunohistochemistry indicated significant neuronal loss when KA was followed by the ASIC inhibitors DAPI or amiloride. Electrophysiological recording from ventral roots of isolated spinal cords showed that alternating oscillatory cycles were slowed down by 0.01mMKA, and intensely inhibited by subsequently applied DAPI or amiloride. Our data suggest that early rise in ASIC expression and function counteracted deleterious effects on spinal networks by raising the excitotoxicity threshold, a result with potential implications for improving neuroprotection.
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Affiliation(s)
- Graciela L Mazzone
- Laboratorios de Investigación aplicada en Neurociencias (LIAN) - Fundación para la Lucha conntra las Enfermedades Neurológicas de la Infancia (FLENI), CONICET, Buenos Aires, Argentina.
| | | | - Carlota Gonzalez-Inchauspe
- Instituto de Fisiología, Biología molecular y Neurociencias, CONICET, Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina
| | - Andrea Nistri
- Neuroscience Department, International School for Advanced Studies (SISSA), Trieste, Italy; Spinal Person Injury Neurorehabilitation Applied Laboratory (SPINAL), Istituto di Medicina Fisica e Riabilitazione, Udine, Italy
| | - Osvaldo D Uchitel
- Instituto de Fisiología, Biología molecular y Neurociencias, CONICET, Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina
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37
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Leroy F, Lamotte d'Incamps B. The Preparation of Oblique Spinal Cord Slices for Ventral Root Stimulation. J Vis Exp 2016. [PMID: 27768090 DOI: 10.3791/54525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Electrophysiological recordings from spinal cord slices have proven to be a valuable technique to investigate a wide range of questions, from cellular to network properties. We show how to prepare viable oblique slices of the spinal cord of young mice (P2 - P11). In this preparation, the motoneurons retain their axons coming out from the ventral roots of the spinal cord. Stimulation of these axons elicits back-propagating action potentials invading the motoneuron somas and exciting the motoneuron collaterals within the spinal cord. Recording of antidromic action potentials is an immediate, definitive and elegant way to characterize motoneuron identity, which surpasses other identification methods. Furthermore, stimulating the motoneuron collaterals is a simple and reliable way to excite the collateral targets of the motoneurons within the spinal cord, such as other motoneurons or Renshaw cells. In this protocol, we present antidromic recordings from the motoneuron somas as well as Renshaw cell excitation, resulting from ventral root stimulation.
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Affiliation(s)
- Félix Leroy
- Centre National de la Recherche Scientifique (UMR 8119), Centre de Neurophysique, Physiologie et Pathologie, Université Paris Descartes;
| | - Boris Lamotte d'Incamps
- Centre National de la Recherche Scientifique (UMR 8119), Centre de Neurophysique, Physiologie et Pathologie, Université Paris Descartes
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38
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Koser DE, Moeendarbary E, Hanne J, Kuerten S, Franze K. CNS cell distribution and axon orientation determine local spinal cord mechanical properties. Biophys J 2016; 108:2137-47. [PMID: 25954872 PMCID: PMC4423070 DOI: 10.1016/j.bpj.2015.03.039] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 02/03/2015] [Accepted: 03/10/2015] [Indexed: 11/10/2022] Open
Abstract
Mechanical signaling plays an important role in cell physiology and pathology. Many cell types, including neurons and glial cells, respond to the mechanical properties of their environment. Yet, for spinal cord tissue, data on tissue stiffness are sparse. To investigate the regional and direction-dependent mechanical properties of spinal cord tissue at a spatial resolution relevant to individual cells, we conducted atomic force microscopy (AFM) indentation and tensile measurements on acutely isolated mouse spinal cord tissue sectioned along the three major anatomical planes, and correlated local mechanical properties with the underlying cellular structures. Stiffness maps revealed that gray matter is significantly stiffer than white matter irrespective of directionality (transverse, coronal, and sagittal planes) and force direction (compression or tension) (Kg= ∼130 Pa vs. Kw= ∼70 Pa); both matters stiffened with increasing strain. When all data were pooled for each plane, gray matter behaved like an isotropic material under compression; however, subregions of the gray matter were rather heterogeneous and anisotropic. For example, in sagittal sections the dorsal horn was significantly stiffer than the ventral horn. In contrast, white matter behaved transversely isotropic, with the elastic stiffness along the craniocaudal (i.e., longitudinal) axis being lower than perpendicular to it. The stiffness distributions we found under compression strongly correlated with the orientation of axons, the areas of cell nuclei, and cellular in plane proximity. Based on these morphological parameters, we developed a phenomenological model to estimate local mechanical properties of central nervous system (CNS) tissue. Our study may thus ultimately help predicting local tissue stiffness, and hence cell behavior in response to mechanical signaling under physiological and pathological conditions, purely based on histological data.
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Affiliation(s)
- David E Koser
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom; Department of Anatomy I, University of Cologne, Cologne, Germany
| | - Emad Moeendarbary
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Janina Hanne
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Stefanie Kuerten
- Department of Anatomy I, University of Cologne, Cologne, Germany; Department of Anatomy and Cell Biology, University of Wuerzburg, Wuerzburg, Germany
| | - Kristian Franze
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom.
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39
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Maeda H, Fukuda S, Kameda H, Murabe N, Isoo N, Mizukami H, Ozawa K, Sakurai M. Corticospinal axons make direct synaptic connections with spinal motoneurons innervating forearm muscles early during postnatal development in the rat. J Physiol 2015; 594:189-205. [PMID: 26503304 DOI: 10.1113/jp270885] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2015] [Accepted: 10/21/2015] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Direct connections between corticospinal (CS) axons and motoneurons (MNs) appear to be present only in higher primates, where they are essential for discrete movement of the digits. Their presence in adult rodents was once claimed but is now questioned. We report that MNs innervating forearm muscles in infant rats receive monosynaptic input from CS axons, but MNs innervating proximal muscles do not, which is a pattern similar to that in primates. Our experiments were carefully designed to show monosynaptic connections. This entailed selective electrical and optogenetic stimulation of CS axons and recording from MNs identified by retrograde labelling from innervated muscles. Morphological evidence was also obtained for rigorous identification of CS axons and MNs. These connections would be transient and would regress later during development. These results shed light on the development and evolution of direct CS-MN connections, which serve as the basis for dexterity in humans. Recent evidence suggests there is no direct connection between corticospinal (CS) axons and spinal motoneurons (MNs) in adult rodents. We previously showed that CS synapses are present throughout the spinal cord for a time, but are eliminated from the ventral horn during development in rodents. This raises the possibility that CS axons transiently make direct connections with MNs located in the ventral horn of the spinal cord. This was tested in the present study. Using cervical cord slices prepared from rats on postnatal days (P) 7-9, CS axons were stimulated and whole cell recordings were made from MNs retrogradely labelled with fluorescent cholera toxin B subunit (CTB) injected into selected groups of muscles. To selectively activate CS axons, electrical stimulation was carefully limited to the CS tract. In addition we employed optogenetic stimulation after injecting an adeno-associated virus vector encoding channelrhodopsin-2 (ChR2) into the sensorimotor cortex on P0. We were then able to record monosynaptic excitatory postsynaptic currents from MNs innervating forearm muscles, but not from those innervating proximal muscles. We also showed close contacts between CTB-labelled MNs and CS axons labelled through introduction of fluorescent protein-conjugated synaptophysin or the ChR2 expression system. We confirmed that some of these contacts colocalized with postsynaptic density protein 95 in their partner dendrites. It is intriguing from both phylogenetic and ontogenetic viewpoints that direct and putatively transient CS-MN connections were found only on MNs innervating the forearm muscles in infant rats, as this is analogous to the connection pattern seen in adult primates.
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Affiliation(s)
- Hitoshi Maeda
- Department of Physiology, Teikyo University School of Medicine, Tokyo, 173-8605, Japan
| | - Satoshi Fukuda
- Department of Physiology, Teikyo University School of Medicine, Tokyo, 173-8605, Japan
| | - Hiroshi Kameda
- Department of Physiology, Teikyo University School of Medicine, Tokyo, 173-8605, Japan
| | - Naoyuki Murabe
- Department of Physiology, Teikyo University School of Medicine, Tokyo, 173-8605, Japan
| | - Noriko Isoo
- Department of Physiology, Teikyo University School of Medicine, Tokyo, 173-8605, Japan
| | - Hiroaki Mizukami
- Division of Genetic Therapeutics, Jichi Medical University, Tochigi, 329-0498, Japan
| | - Keiya Ozawa
- Division of Genetic Therapeutics, Jichi Medical University, Tochigi, 329-0498, Japan.,Research Hospital, Institute of Medical Science, Tokyo University, Tokyo, 108-8639, Japan
| | - Masaki Sakurai
- Department of Physiology, Teikyo University School of Medicine, Tokyo, 173-8605, Japan
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40
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Mayo JN, Bearden SE. Driving the Hypoxia-Inducible Pathway in Human Pericytes Promotes Vascular Density in an Exosome-Dependent Manner. Microcirculation 2015; 22:711-23. [PMID: 26243428 PMCID: PMC4715585 DOI: 10.1111/micc.12227] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Accepted: 07/29/2015] [Indexed: 12/13/2022]
Abstract
OBJECTIVES The mechanisms involved in activating pericytes, cells that ensheath capillaries, to engage in the formation of new capillaries, angiogenesis, remain unknown. In this study, the hypothesis was tested that pericytes could be stimulated to promote angiogenesis by driving the HIF pathway. METHODS Pericytes were stimulated with CoCl2 to activate the HIF pathway. Stimulated pericytes were cocultured with endothelial cells in a wound healing assay and in a 3D collagen matrix assay of angiogenesis. A culture system of spinal cord tissue was used to assess microvascular outcomes after treatment with stimulated pericytes. Pharmaceutical inhibition of exosome production was also performed. RESULTS Treatment with stimulated pericytes resulted in faster wound healing (1.92 ± 0.18 fold increase, p < 0.05), greater endothelial cord formation (2.9 ± 0.14 fold increase, p < 0.05) in cell culture assays, and greater vascular density (1.78 ± 0.23 fold increase, p < 0.05) in spinal cord tissue. Exosome secretion and the physical presence of stimulated pericytes were necessary in the promotion of angiogenic outcomes. CONCLUSIONS These results elucidate a mechanism that may be exploited to enhance features of angiogenesis in the CNS.
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Affiliation(s)
- Jamie N. Mayo
- Department of Biological Sciences, Idaho State University, 921 S. 8th Ave Stop 8007, Pocatello, ID, 83209
| | - Shawn E. Bearden
- Department of Biological Sciences, Idaho State University, 921 S. 8th Ave Stop 8007, Pocatello, ID, 83209
- ISU Biomedical Research Institute, Idaho State University, 921 S. 8th Ave Stop 8046, Pocatello, ID, 83209
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41
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Milan L, Courtand G, Cardoit L, Masmejean F, Barrière G, Cazalets JR, Garret M, Bertrand SS. Age-Related Changes in Pre- and Postsynaptic Partners of the Cholinergic C-Boutons in Wild-Type and SOD1G93A Lumbar Motoneurons. PLoS One 2015; 10:e0135525. [PMID: 26305672 PMCID: PMC4549056 DOI: 10.1371/journal.pone.0135525] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Accepted: 07/22/2015] [Indexed: 11/19/2022] Open
Abstract
Large cholinergic synaptic terminals known as C-boutons densely innervate the soma and proximal dendrites of motoneurons that are prone to neurodegeneration in amyotrophic lateral sclerosis (ALS). Studies using the Cu/Zn-superoxide dismutase (SOD1) mouse model of ALS have generated conflicting data regarding C-bouton alterations exhibited during ALS pathogenesis. In the present work, a longitudinal study combining immunohistochemistry, biochemical approaches and extra- and intra-cellular electrophysiological recordings revealed that the whole spinal cholinergic system is modified in the SOD1 mouse model of ALS compared to wild type (WT) mice as early as the second postnatal week. In WT motoneurons, both C-bouton terminals and associated M2 postsynaptic receptors presented a complex age-related dynamic that appeared completely disrupted in SOD1 motoneurons. Indeed, parallel to C-bouton morphological alterations, analysis of confocal images revealed a clustering process of M2 receptors during WT motoneuron development and maturation that was absent in SOD1 motoneurons. Our data demonstrated for the first time that the lamina X cholinergic interneurons, the neuronal source of C-boutons, are over-abundant in high lumbar segments in SOD1 mice and are subject to neurodegeneration in the SOD1 animal model. Finally, we showed that early C-bouton system alterations have no physiological impact on the cholinergic neuromodulation of newborn motoneurons. Altogether, these data suggest a complete reconfiguration of the spinal cholinergic system in SOD1 spinal networks that could be part of the compensatory mechanisms established during spinal development.
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Affiliation(s)
- Léa Milan
- INCIA, Université de Bordeaux, CNRS UMR5287, Bordeaux, France
| | - Gilles Courtand
- INCIA, Université de Bordeaux, CNRS UMR5287, Bordeaux, France
| | - Laura Cardoit
- INCIA, Université de Bordeaux, CNRS UMR5287, Bordeaux, France
| | | | | | | | - Maurice Garret
- INCIA, Université de Bordeaux, CNRS UMR5287, Bordeaux, France
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42
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Vincen-Brown MA, Whitesitt KC, Quick FG, Pilarski JQ. Studying respiratory rhythm generation in a developing bird: Hatching a new experimental model using the classic in vitro brainstem-spinal cord preparation. Respir Physiol Neurobiol 2015; 224:62-70. [PMID: 26310580 DOI: 10.1016/j.resp.2015.08.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 08/18/2015] [Accepted: 08/19/2015] [Indexed: 01/17/2023]
Abstract
It has been more than thirty years since the in vitro brainstem-spinal cord preparation was first presented as a method to study automatic breathing behaviors in the neonatal rat. This straightforward preparation has led to an incredible burst of information about the location and coordination of several spontaneously active microcircuits that form the ventrolateral respiratory network of the brainstem. Despite these advances, our knowledge of the mechanisms that regulate central breathing behaviors is still incomplete. Investigations into the nature of spontaneous breathing rhythmicity have almost exclusively focused on mammals, and there is a need for comparative experimental models to evaluate several unresolved issues from a different perspective. With this in mind, we sought to develop a new avian in vitro model with the long term goal to better understand questions associated with the ontogeny of respiratory rhythm generation, neuroplasticity, and whether multiple, independent oscillators drive the major phases of breathing. The fact that birds develop in ovo provides unparalleled access to central neuronal networks throughout the prenatal period - from embryo to hatchling - that are free from confounding interactions with mother. Previous studies using in vitro avian models have been strictly limited to the early embryonic period. Consequently, the details and even the presence of brainstem derived breathing-related rhythmogenesis in birds have never been described. In the present study, we used the altricial zebra finch (Taeniopygia guttata) and show robust spontaneous motor outflow through cranial motor nerve IX, which is first detectable on embryonic day four and continues through prenatal and early postnatal development without interruption. We also show that brainstem oscillations change dramatically over the course of prenatal development, sometimes within hours, which suggests rapid maturational modifications in growth and connectivity. We propose that this experimental preparation will be useful for a variety of studies aimed at testing the biophysical and synaptic properties of neurons that participate in the unique spatiotemporal patterns of avian breathing behaviors, especially in the context of early development.
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Affiliation(s)
| | - Kaitlyn C Whitesitt
- Department of Biological Sciences, Idaho State University, Pocatello, ID, 83 209, USA
| | - Forrest G Quick
- Department of Biological Sciences, Idaho State University, Pocatello, ID, 83 209, USA
| | - Jason Q Pilarski
- Department of Biological Sciences, Idaho State University, Pocatello, ID, 83 209, USA; Department of Dental Sciences, Idaho State University, Pocatello, ID, 83 209 USA.
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43
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Chen YB, Huang FS, Fen B, Yin JB, Wang W, Li YQ. Inhibitory effects of endomorphin-2 on excitatory synaptic transmission and the neuronal excitability of sacral parasympathetic preganglionic neurons in young rats. Front Cell Neurosci 2015; 9:206. [PMID: 26074773 PMCID: PMC4446531 DOI: 10.3389/fncel.2015.00206] [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: 04/02/2015] [Accepted: 05/12/2015] [Indexed: 01/23/2023] Open
Abstract
The function of the urinary bladder is partly controlled by parasympathetic preganglionic neurons (PPNs) of the sacral parasympathetic nucleus (SPN). Our recent work demonstrated that endomorphin-2 (EM-2)-immunoreactive (IR) terminals form synapses with μ-opioid receptor (MOR)-expressing PPNs in the rat SPN. Here, we examined the effects of EM-2 on excitatory synaptic transmission and the neuronal excitability of the PPNs in young rats (24–30 days old) using a whole-cell patch-clamp approach. PPNs were identified by retrograde labeling with the fluorescent tracer tetramethylrhodamine-dextran (TMR). EM-2 (3 μM) markedly decreased both the amplitude and the frequency of the spontaneous and miniature excitatory postsynaptic currents (sEPSCs and mEPSCs) of PPNs. EM-2 not only decreased the resting membrane potentials (RMPs) in 61.1% of the examined PPNs with half-maximal response at the concentration of 0.282 μM, but also increased the rheobase current and reduced the repetitive action potential firing of PPNs. Analysis of the current–voltage relationship revealed that the EM-2-induced current was reversed at −95 ± 2.5 mV and was suppressed by perfusion of the potassium channel blockers 4-aminopyridine (4-AP) or BaCl2 or by the addition of guanosine 5′-[β-thio]diphosphate trilithium salt (GDP-β-S) to the pipette solution, suggesting the involvement of the G-protein-coupled inwardly rectifying potassium (GIRK) channel. The above EM-2-invoked inhibitory effects were abolished by the MOR selective antagonist D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP), indicating that the effects of EM-2 on PPNs were mediated by MOR via pre- and/or post-synaptic mechanisms. EM-2 activated pre- and post-synaptic MORs, inhibiting excitatory neurotransmitter release from the presynaptic terminals and decreasing the excitability of PPNs due to hyperpolarization of their membrane potentials, respectively. These inhibitory effects of EM-2 on PPNs at the spinal cord level may explain the mechanism of action of morphine treatment and morphine-induced bladder dysfunction in the clinic.
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Affiliation(s)
- Ying-Biao Chen
- Department of Anatomy, Histology and Embryology, Fujian Medical University Fuzhou, China
| | - Fen-Sheng Huang
- Department of Anatomy, Histology and Embryology and K. K. Leung Brain Research Centre, The Fourth Military Medical University Xi'an, China ; Division of Medical Biophysics, Institute of Neuroscience and Physiology, Göteborg University Göteborg, Sweden
| | - Ban Fen
- Department of Anatomy, Histology and Embryology and K. K. Leung Brain Research Centre, The Fourth Military Medical University Xi'an, China
| | - Jun-Bin Yin
- Department of Anatomy, Histology and Embryology and K. K. Leung Brain Research Centre, The Fourth Military Medical University Xi'an, China
| | - Wei Wang
- Department of Anatomy, Histology and Embryology, Fujian Medical University Fuzhou, China
| | - Yun-Qing Li
- Department of Anatomy, Histology and Embryology, Fujian Medical University Fuzhou, China ; Department of Anatomy, Histology and Embryology and K. K. Leung Brain Research Centre, The Fourth Military Medical University Xi'an, China ; Collaborative Innovation Center for Brain Science, Fudan University Shanghai, China
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44
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Perry S, Gezelius H, Larhammar M, Hilscher MM, Lamotte d'Incamps B, Leao KE, Kullander K. Firing properties of Renshaw cells defined by Chrna2 are modulated by hyperpolarizing and small conductance ion currents Ih and ISK. Eur J Neurosci 2015; 41:889-900. [PMID: 25712471 DOI: 10.1111/ejn.12852] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 12/19/2014] [Accepted: 01/16/2015] [Indexed: 11/28/2022]
Abstract
Renshaw cells in the spinal cord ventral horn regulate motoneuron output through recurrent inhibition. Renshaw cells can be identified in vitro using anatomical and cellular criteria; however, their functional role in locomotion remains poorly defined because of the difficulty of functionally isolating Renshaw cells from surrounding motor circuits. Here we aimed to investigate whether the cholinergic nicotinic receptor alpha2 (Chrna2) can be used to identify Renshaw cells (RCs(α2)) in the mouse spinal cord. Immunohistochemistry and electrophysiological characterization of passive and active RCs(α2) properties confirmed that neurons genetically marked by the Chrna2-Cre mouse line together with a fluorescent reporter mouse line are Renshaw cells. Whole-cell patch-clamp recordings revealed that RCs(α2) constitute an electrophysiologically stereotyped population with a resting membrane potential of -50.5 ± 0.4 mV and an input resistance of 233.1 ± 11 MΩ. We identified a ZD7288-sensitive hyperpolarization-activated cation current (Ih) in all RCs(α2), contributing to membrane repolarization but not to the resting membrane potential in neonatal mice. Additionally, we found RCs(α2) to express small calcium-activated potassium currents (I(SK)) that, when blocked by apamin, resulted in a complete attenuation of the afterhyperpolarisation potential, increasing cellular firing frequency. We conclude that RCs(α2) can be genetically targeted through their selective Chrna2 expression and that they display currents known to modulate rebound excitation and firing frequency. The genetic identification of Renshaw cells and their electrophysiological profile is required for genetic and pharmacological manipulation as well as computational simulations with the aim to understand their functional role.
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Affiliation(s)
- Sharn Perry
- Department of Neuroscience, Uppsala University, Box 593, 751 24, Uppsala, Sweden
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Gautier HO, Thompson AJ, Achouri S, Koser DE, Holtzmann K, Moeendarbary E, Franze K. Atomic force microscopy-based force measurements on animal cells and tissues. Methods Cell Biol 2015; 125:211-35. [DOI: 10.1016/bs.mcb.2014.10.005] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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46
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Astrocyte-encoded positional cues maintain sensorimotor circuit integrity. Nature 2014; 509:189-94. [PMID: 24776795 PMCID: PMC4057936 DOI: 10.1038/nature13161] [Citation(s) in RCA: 219] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Accepted: 02/18/2014] [Indexed: 01/03/2023]
Abstract
Astrocytes, the most abundant cells in the central nervous system, promote synapse formation and help refine neural connectivity. Although they are allocated to spatially distinct regional domains during development, it is unknown whether region-restricted astrocytes are functionally heterogeneous. Here we show that postnatal spinal cord astrocytes express several region-specific genes, and that ventral astrocyte-encoded Semaphorin3a (Sema3a) is required for proper motor neuron and sensory neuron circuit organization. Loss of astrocyte-encoded Sema3a led to dysregulated α–motor neuron axon initial segment orientation, markedly abnormal synaptic inputs, and selective death of α–but not of adjacent γ–motor neurons. Additionally, a subset of TrkA+ sensory afferents projected to ectopic ventral positions. These findings demonstrate that stable maintenance of a positional cue by developing astrocytes influences multiple aspects of sensorimotor circuit formation. More generally, they suggest that regional astrocyte heterogeneity may help to coordinate postnatal neural circuit refinement.
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47
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Müller D, Cherukuri P, Henningfeld K, Poh CH, Wittler L, Grote P, Schlüter O, Schmidt J, Laborda J, Bauer SR, Brownstone RM, Marquardt T. Dlk1 promotes a fast motor neuron biophysical signature required for peak force execution. Science 2014; 343:1264-6. [PMID: 24626931 DOI: 10.1126/science.1246448] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Motor neurons, which relay neural commands to drive skeletal muscle movements, encompass types ranging from "slow" to "fast," whose biophysical properties govern the timing, gradation, and amplitude of muscle force. Here we identify the noncanonical Notch ligand Delta-like homolog 1 (Dlk1) as a determinant of motor neuron functional diversification. Dlk1, expressed by ~30% of motor neurons, is necessary and sufficient to promote a fast biophysical signature in the mouse and chick. Dlk1 suppresses Notch signaling and activates expression of the K(+) channel subunit Kcng4 to modulate delayed-rectifier currents. Dlk1 inactivation comprehensively shifts motor neurons toward slow biophysical and transcriptome signatures, while abolishing peak force outputs. Our findings provide insights into the development of motor neuron functional diversity and its contribution to the execution of movements.
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Affiliation(s)
- Daniel Müller
- Developmental Neurobiology Laboratory, European Neuroscience Institute (ENI-G), Grisebachstraße 5, 37077 Göttingen, Germany
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48
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Fuchs A, Kutterer S, Mühling T, Duda J, Schütz B, Liss B, Keller BU, Roeper J. Selective mitochondrial Ca2+ uptake deficit in disease endstage vulnerable motoneurons of the SOD1G93A mouse model of amyotrophic lateral sclerosis. J Physiol 2013; 591:2723-45. [PMID: 23401612 PMCID: PMC3678052 DOI: 10.1113/jphysiol.2012.247981] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Accepted: 02/04/2013] [Indexed: 12/13/2022] Open
Abstract
Amyotrophic lateral sclerosis is a progressive neurodegenerative disease that targets some somatic motoneuron populations, while others, e.g. those of the oculomotor system, are spared. The pathophysiological basis of this pattern of differential vulnerability, which is preserved in a transgenic mouse model of amyotrophic lateral sclerosis (SOD1(G93A)), and the mechanism of neurodegeneration in general are unknown. Hyperexcitability and calcium dysregulation have been proposed by others on the basis of data from juvenile mice that are, however, asymptomatic. No studies have been done with symptomatic mice following disease progression to the disease endstage. Here, we developed a new brainstem slice preparation for whole-cell patch-clamp recordings and single cell fura-2 calcium imaging to study motoneurons in adult wild-type and SOD1(G93A) mice up to disease endstage. We analysed disease-stage-dependent electrophysiological properties and intracellular Ca(2+) handling of vulnerable hypoglossal motoneurons in comparison to resistant oculomotor neurons. Thereby, we identified a transient hyperexcitability in presymptomatic but not in endstage vulnerable motoneurons. Additionally, we revealed a remodelling of intracellular Ca(2+) clearance within vulnerable but not resistant motoneurons at disease endstage characterised by a reduction of uniporter-dependent mitochondrial Ca(2+) uptake and enhanced Ca(2+) extrusion across the plasma membrane. Our study challenged the notion that hyperexcitability is a direct cause of neurodegeneration in SOD1(G93A) mice, but molecularly identified a Ca(2+) clearance deficit in motoneurons and an adaptive Ca(2+) handling strategy that might be targeted by future therapeutic strategies.
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Affiliation(s)
- Andrea Fuchs
- Mammalian Locomotor Laboratory, Department of Neuroscience, Karolinska Institutet, Retzius Väg 8, 17177 Stockholm, Sweden.
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Manuel M, Marin M, Heckman CJ. Simultaneous intracellular recording of a lumbar motoneuron and the force produced by its motor unit in the adult mouse in vivo. J Vis Exp 2012:e4312. [PMID: 23242236 DOI: 10.3791/4312] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The spinal motoneuron has long been a good model system for studying neural function because it is a neuron of the central nervous system with the unique properties of (1) having readily identifiable targets (the muscle fibers) and therefore having a very well-known function (to control muscle contraction); (2) being the convergent target of many spinal and descending networks, hence the name of "final common pathway"; and (3) having a large soma which makes it possible to penetrate them with sharp intracellular electrodes. Furthermore, when studied in vivo, it is possible to record simultaneously the electrical activity of the motoneurons and the force developed by their muscle targets. Performing intracellular recordings of motoneurons in vivo therefore put the experimentalist in the unique position of being able to study, at the same time, all the compartments of the "motor unit" (the name given to the motoneuron, its axon, and the muscle fibers it innervates(1)): the inputs impinging on the motoneuron, the electrophysiological properties of the motoneuron, and the impact of these properties on the physiological function of the motoneurons, i.e. the force produced by its motor unit. However, this approach is very challenging because the preparation cannot be paralyzed and thus the mechanical stability for the intracellular recording is reduced. Thus, this kind of experiments has only been achieved in cats and in rats. However, the study of spinal motor systems could make a formidable leap if it was possible to perform similar experiments in normal and genetically modified mice. For technical reasons, the study of the spinal networks in mice has mostly been limited to neonatal in vitro preparations, where the motoneurons and the spinal networks are immature, the motoneurons are separated from their targets, and when studied in slices, the motoneurons are separated from most of their inputs. Until recently, only a few groups had managed to perform intracellular recordings of motoneurons in vivo(2-4 ), including our team who published a new preparation which allowed us to obtain very stable recordings of motoneurons in vivo in adult mice(5,6). However, these recordings were obtained in paralyzed animals, i.e. without the possibility to record the force output of these motoneurons. Here we present an extension of this original preparation in which we were able to obtain simultaneous recordings of the electrophysiological properties of the motoneurons and of the force developed by their motor unit. This is an important achievement, as it allows us to identify the different types of motoneurons based on their force profile, and thereby revealing their function. Coupled with genetic models disturbing spinal segmental circuitry(7-9), or reproducting human disease(10,11), we expect this technique to be an essential tool for the study of spinal motor system.
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Affiliation(s)
- Marin Manuel
- Department of Physiology, Northwestern University Feinberg School of Medicine.
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Abbinanti MD, Zhong G, Harris-Warrick RM. Postnatal emergence of serotonin-induced plateau potentials in commissural interneurons of the mouse spinal cord. J Neurophysiol 2012; 108:2191-202. [PMID: 22832564 PMCID: PMC3545016 DOI: 10.1152/jn.00336.2012] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Accepted: 07/18/2012] [Indexed: 02/07/2023] Open
Abstract
Most studies of the mouse hindlimb locomotor network have used neonatal (P0-5) mice. In this study, we examine the postnatal development of intrinsic properties and serotonergic modulation of intersegmental commissural interneurons (CINs) from the neonatal period (P0-3) to the time the animals bear weight (P8-10) and begin to show adult walking (P14-16). CINs show an increase in excitability with age, associated with a decrease in action potential halfwidth and appearance of a fast component to the afterhyperpolarization at P14-16. Serotonin (5-HT) depolarizes and increases the excitability of most CINs at all ages. The major developmental difference is that serotonin can induce plateau potential capability in P14-16 CINs, but not at younger ages. These plateau potentials are abolished by nifedipine, suggesting that they are mediated by an L-type calcium current, I(Ca(L)). Voltage-clamp analysis demonstrates that 5-HT increases a nifedipine-sensitive voltage-activated calcium current, I(Ca(V)), in P14-16 CINs but does not increase I(Ca(V)) in P8-10 CINs. These results, together with earlier work on 5-HT effects on neonatal CINs, suggest that 5-HT increases the excitability of CINs at all ages studied, but by opposite effects on calcium currents, decreasing N- and P/Q-type calcium currents and, indirectly, calcium-activated potassium current, at P0-3 but increasing I(Ca(L)) at P14-16.
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