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Canepari M, Ross WN. Spatial and temporal aspects of neuronal calcium and sodium signals measured with low-affinity fluorescent indicators. Pflugers Arch 2024; 476:39-48. [PMID: 37798555 DOI: 10.1007/s00424-023-02865-1] [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: 08/14/2023] [Revised: 09/12/2023] [Accepted: 09/21/2023] [Indexed: 10/07/2023]
Abstract
Low-affinity fluorescent indicators for Ca2+ or Na+ allow measuring the dynamics of intracellular concentration of these ions with little perturbation from physiological conditions because they are weak buffers. When using synthetic indicators, which are small molecules with fast kinetics, it is also possible to extract spatial and temporal information on the sources of ion transients, their localization, and their disposition. This review examines these important aspects from the biophysical point of view, and how they have been recently exploited in neurophysiological studies. We first analyze the environment where Ca2+ and Na+ indicators are inserted, highlighting the interpretation of the two different signals. Then, we address the information that can be obtained by analyzing the rising phase and the falling phase of the Ca2+ and Na+ transients evoked by different stimuli, focusing on the kinetics of ionic currents and on the spatial interpretation of these measurements, especially on events in axons and dendritic spines. Finally, we suggest how Ca2+ or Na+ imaging using low-affinity synthetic fluorescent indicators can be exploited in future fundamental or applied research.
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Affiliation(s)
- Marco Canepari
- LIPhy, CNRS, Univ. Grenoble Alpes, F-38000, Grenoble, France.
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Valbonne, France.
- Institut National de la Santé et Recherche Médicale, Paris, France.
| | - William N Ross
- Department of Physiology, New York Medical College, Valhalla, NY, 10595, USA
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2
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Jarosova R, Kaplan SV, Field TM, Givens RS, Senadheera SN, Johnson MA. In Situ Electrochemical Monitoring of Caged Compound Photochemistry: An Internal Actinometer for Substrate Release. Anal Chem 2021; 93:2776-2784. [PMID: 33492927 DOI: 10.1021/acs.analchem.0c03452] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Caged compounds are molecules that release a protective substrate to free a biologically active substrate upon treatment with light of sufficient energy and duration. A notable limitation of this approach is difficulty in determining the degree of photoactivation in tissues or opaque solutions because light reaching the desired location is obstructed. Here, we have addressed this issue by developing an in situ electrochemical method in which the amount of caged molecule photorelease is determined by fast-scan cyclic voltammetry (FSCV) at carbon-fiber microelectrodes. Using p-hydroxyphenyl glutamate (pHP-Glu) as our model system, we generated a linear calibration curve for oxidation of 4-hydroxyphenylacetic acid (4HPAA), the group from which the glutamate molecule leaves, up to a concentration of 1000 μM. Moreover, we are able to correct for the presence of residual pHP-Glu in solution as well as the light artifact that is produced. A corrected calibration curve was constructed by photoactivation of pHP-Glu in a 3 μL photoreaction vessel and subsequent analysis by high-performance liquid chromatography. This approach has yielded a linear relationship between 4HPAA concentration and oxidation current, allowing the determination of released glutamate independent of the amount of light reaching the chromophore. Moreover, we have successfully validated the newly developed method by in situ measurement in a whole, intact zebrafish brain. This work demonstrates for the first time the in situ electrochemical monitoring of caged compound photochemistry in brain tissue with FSCV, thus facilitating analyses of neuronal function.
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Affiliation(s)
- Romana Jarosova
- Department of Chemistry and R.N. Adams Institute for Bioanalytical Chemistry, University of Kansas, Lawrence, Kansas 66045, United States.,Department of Analytical Chemistry, UNESCO Laboratory of Environmental Electrochemistry, Charles University, Prague 2 12843, Czech Republic
| | - Sam V Kaplan
- Department of Chemistry and R.N. Adams Institute for Bioanalytical Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Thomas M Field
- Department of Chemistry and R.N. Adams Institute for Bioanalytical Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Richard S Givens
- Department of Chemistry and R.N. Adams Institute for Bioanalytical Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Sanjeewa N Senadheera
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Michael A Johnson
- Department of Chemistry and R.N. Adams Institute for Bioanalytical Chemistry, University of Kansas, Lawrence, Kansas 66045, United States.,Graduate Program in Neuroscience, University of Kansas, Lawrence, Kansas 66045, United States
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Brockhaus J, Brüggen B, Missler M. Imaging and Analysis of Presynaptic Calcium Influx in Cultured Neurons Using synGCaMP6f. Front Synaptic Neurosci 2019; 11:12. [PMID: 31057389 PMCID: PMC6477507 DOI: 10.3389/fnsyn.2019.00012] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Accepted: 03/26/2019] [Indexed: 12/12/2022] Open
Abstract
Presynaptic Ca2+ influx through voltage-gated calcium channels (VGCCs) is a key step in synaptic transmission that links action potential (AP)-derived depolarization to vesicle release. However, investigation of presynaptic Ca2+ influx by patch clamp recordings is difficult due to the small size of the majority of synaptic boutons along thin axons that hamper clamp control. Genetically encoded calcium indicators (GECIs) in combination with live cell imaging provide an alternative method to study Ca2+ transients in individual presynaptic terminals. The indicator GCaMP6f was developed for fast speed and high sensitivity in detecting Ca2+ transients even in subcellular compartments. We fused GCaMP6f to synaptophysin (synGCaMP6f) to enrich the calcium indicator in presynaptic boutons of transfected primary hippocampal neurons to study presynaptic Ca2+ changes in response to individual APs or short bursts. Changes in fluorescence intensity were evaluated by normalization to control level or, alternatively, by normalization to maximal fluorescence using the calcium ionophore ionomycin. Measurements revealed robust Ca2+ transients with amplitudes that depend on parameters like the number of APs, stimulation frequency or external calcium concentration. Our findings indicate an appropriate sensitivity of synGCaMP6f for studying total presynaptic Ca2+ transients induced by single APs or short bursts that showed little rundown of the response after repeated bursts. Moreover, these recordings are fast enough to even study short-term plasticity like paired pulse facilitation (PPF) and frequency dependence of Ca2+ transients. In addition, synGCaMP6f could be used to dissect the contribution of different subtypes of VGCCs to presynaptic Ca2+ influx. Our results demonstrate that synGCaMP6f allows the reliable analysis of changes in presynaptic calcium concentration at many individual synaptic boutons in parallel and provides the possibility to study the regulation of this important step in synaptic transmission.
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Affiliation(s)
- Johannes Brockhaus
- Institute of Anatomy and Molecular Neurobiology, Westfälische Wilhelms-University, Münster, Germany
| | - Bianca Brüggen
- Institute of Anatomy and Molecular Neurobiology, Westfälische Wilhelms-University, Münster, Germany
| | - Markus Missler
- Institute of Anatomy and Molecular Neurobiology, Westfälische Wilhelms-University, Münster, Germany
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Filipis L, Ait Ouares K, Moreau P, Tanese D, Zampini V, Latini A, Bleau C, Bleau C, Graham J, Canepari M. A novel multisite confocal system for rapid Ca 2+ imaging from submicron structures in brain slices. JOURNAL OF BIOPHOTONICS 2018; 11. [PMID: 29165917 DOI: 10.1002/jbio.201700197] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2017] [Accepted: 11/13/2017] [Indexed: 05/14/2023]
Abstract
In brain slices, resolving fast Ca2+ fluorescence signals from submicron structures is typically achieved using 2-photon or confocal scanning microscopy, an approach that limits the number of scanned points. The novel multiplexing confocal system presented here overcomes this limitation. This system is based on a fast spinning disk, a multimode diode laser and a novel high-resolution CMOS camera. The spinning disk, running at 20 000 rpm, has custom-designed spiral pattern that maximises light collection, while rejecting out-of-focus fluorescence to resolve signals from small neuronal compartments. Using a 60× objective, the camera permits acquisitions of tens of thousands of pixels at resolutions of ~250 nm per pixel in the kHz range with 14 bits of digital depth. The system can resolve physiological Ca2+ transients from submicron structures at 20 to 40 μm below the slice surface, using the low-affinity Ca2+ indicator Oregon Green BAPTA-5N. In particular, signals at 0.25 to 1.25 kHz were resolved in single trials, or through averages of a few recordings, from dendritic spines and small parent dendrites in cerebellar Purkinje neurons. Thanks to an unprecedented combination of temporal and spatial resolution with relatively simple implementation, it is expected that this system will be widely adopted for multisite monitoring of Ca2+ signals.
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Affiliation(s)
- Luiza Filipis
- Laboratory for Interdisciplinary Physics, UMR 5588 CNRS and Université Grenoble Alpes, Saint Martin d'Hères Cedex, France
- Laboratories of Excellence, Ion Channel Science and Therapeutics, France
| | - Karima Ait Ouares
- Laboratory for Interdisciplinary Physics, UMR 5588 CNRS and Université Grenoble Alpes, Saint Martin d'Hères Cedex, France
- Laboratories of Excellence, Ion Channel Science and Therapeutics, France
| | - Philippe Moreau
- Laboratory for Interdisciplinary Physics, UMR 5588 CNRS and Université Grenoble Alpes, Saint Martin d'Hères Cedex, France
| | - Dimitrii Tanese
- Wavefront-Engineering Microscopy Group, Neurophotonics Laboratory, UMR8250 CNRS and Paris Descartes University, Paris, France
| | - Valeria Zampini
- Wavefront-Engineering Microscopy Group, Neurophotonics Laboratory, UMR8250 CNRS and Paris Descartes University, Paris, France
| | | | | | | | | | - Marco Canepari
- Laboratory for Interdisciplinary Physics, UMR 5588 CNRS and Université Grenoble Alpes, Saint Martin d'Hères Cedex, France
- Laboratories of Excellence, Ion Channel Science and Therapeutics, France
- Institut National de la Santé et Recherche Médicale (INSERM), France
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5
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Molecular Tattoo: Subcellular Confinement of Drug Effects. ACTA ACUST UNITED AC 2015; 22:548-558. [DOI: 10.1016/j.chembiol.2015.03.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 03/11/2015] [Accepted: 03/13/2015] [Indexed: 01/23/2023]
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Davies R, Graham J, Canepari M. Light sources and cameras for standard in vitro membrane potential and high-speed ion imaging. J Microsc 2013; 251:5-13. [PMID: 23692638 DOI: 10.1111/jmi.12047] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Accepted: 04/04/2013] [Indexed: 11/29/2022]
Abstract
Membrane potential and fast ion imaging are now standard optical techniques routinely used to record dynamic physiological signals in several preparations in vitro. Although detailed resolution of optical signals can be improved by confocal or two-photon microscopy, high spatial and temporal resolution can be obtained using conventional microscopy and affordable light sources and cameras. Thus, standard wide-field imaging methods are still the most common in research laboratories and can often produce measurements with a signal-to-noise ratio that is superior to other optical approaches. This paper seeks to review the most important instrumentation used in these experiments, with particular reference to recent technological advances. We analyse in detail the optical constraints dictating the type of signals that are obtained with voltage and ion imaging and we discuss how to use this information to choose the optimal apparatus. Then, we discuss the available light sources with specific attention to light emitting diodes and solid state lasers. We then address the current state-of-the-art of available charge coupled device, electron multiplying charge coupled device and complementary metal oxide semiconductor cameras and we analyse the characteristics that need to be taken into account for the choice of optimal detector. Finally, we conclude by discussing prospective future developments that are likely to further improve the quality of the signals expanding the capability of the techniques and opening the gate to novel applications.
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Affiliation(s)
- R Davies
- CAIRN Research Ltd, Faversham, UK
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7
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Nevian T, Helmchen F. Calcium indicator loading of neurons using single-cell electroporation. Pflugers Arch 2007; 454:675-88. [PMID: 17334778 DOI: 10.1007/s00424-007-0234-2] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2005] [Revised: 01/15/2007] [Accepted: 02/12/2007] [Indexed: 12/26/2022]
Abstract
Studies of subcellular Ca(2+) signaling rely on methods for labeling cells with fluorescent Ca(2+) indicator dyes. In this study, we demonstrate the use of single-cell electroporation for Ca(2+) indicator loading of individual neurons and small neuronal networks in rat neocortex in vitro and in vivo. Brief voltage pulses were delivered through glass pipettes positioned close to target cells. This approach resulted in reliable and rapid (within seconds) loading of somata and subsequent complete labeling of dendritic and axonal arborizations. By using simultaneous whole-cell recordings in brain slices, we directly addressed the effect of electroporation on neurons. Cell viability was high (about 85%) with recovery from the membrane permeabilization occurring within a minute. Electrical properties of recovered cells were indistinguishable before and after electroporation. In addition, Ca(2+) transients with normal appearance could be evoked in dendrites, spines, and axonal boutons of electroporated cells. Using negative-stains of somata, targeted single-cell electroporation was equally applicable in vivo. We conclude that electroporation is a simple approach that permits Ca(2+) indicator loading of multiple cells with low background staining within a short amount of time, which makes it especially well suited for functional imaging of subcellular Ca(2+) dynamics in small neuronal networks.
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Affiliation(s)
- Thomas Nevian
- Abteilung Zellphysiologie, Max-Planck-Institut für medizinische Forschung, Jahnstrasse 29, 69120 Heidelberg, Germany.
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8
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Hsu SF, Ahern GP, Jackson MB. Ultra-violet light-induced changes in membrane properties in secretory cells. J Neurosci Methods 1999; 90:67-79. [PMID: 10517275 DOI: 10.1016/s0165-0270(99)00071-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Illumination with ultra-violet is used widely in physiological experiments for the photolysis of caged compounds. In the peptidergic cells of the pituitary gland, as well as cultured PC12 cells, ultra-violet light was found to produce changes in a number of membrane properties. Light of sufficient intensity to produce rapid photolysis of commonly used caged compounds induced changes in K+ and Ca2+ current, as well as changes in membrane capacitance. All responses to light showed a rapid timecourse, activating in a few ms and decaying within 10-50 ms after illumination ended. Experiments with radical scavengers and with inhibitors of cytochrome p450 and phospholipase A2 failed to block the light responses. These rapid responses to light emphasize that experiments employing ultra-violet light in the photorelease of physiological and pharmacological agents require special care for control of light artifacts.
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Affiliation(s)
- S F Hsu
- Department of Physiology, University of Wisconsin Medical School, Madison 53706, USA
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9
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Kötter R, Staiger JF, Zilles K, Luhmann HJ. Analysing functional connectivity in brain slices by a combination of infrared video microscopy, flash photolysis of caged compounds and scanning methods. Neuroscience 1998; 86:265-77. [PMID: 9692760 DOI: 10.1016/s0306-4522(98)00010-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We evaluate a novel set-up for scanning functional connectivity in brain slices from the somatosensory cortex of the rat. Upright infrared video microscopy for targeted placement of electrodes is combined with rapid photolysis of bath-applied caged neurotransmitter induced by a xenon flash lamp. Flash photolysis of caged glutamate and electrical stimulation produce comparable field potential responses and demonstrate that the viability of the submerged slices exceeds several hours. Glutamate release leads to field potential responses whose two phases are differentially affected by selective blockade of N-methyl-D-aspartate- and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate-type glutamate receptors with DL-2-amino-5-phosphonovaleric acid and 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulphonamide, respectively. Rapid computer-controlled scanning of hundreds of distinct stimulation sites with simultaneous recordings at a fixed reference site allows construction of functional input maps from peak amplitudes and delays to peak of field potential responses. Selective laminar expansion of the functional input maps after bicuculline application demonstrates that the combination of this conveniently assembled set-up with pharmacological and physical manipulations can provide insights into the determinants of functional connectivity in brain slices.
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Affiliation(s)
- R Kötter
- C. & O. Vogt-Institut für Hirnforschung, Heinrich-Heine-Universität, Düsseldorf, Germany
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Partridge LD, Zeilhofer HU, Swandulla D. Combined whole-cell and single-channel current measurement with quantitative Ca2+ injection or Fura-2 measurement of Ca2+. Methods Enzymol 1998; 293:371-83. [PMID: 9711619 DOI: 10.1016/s0076-6879(98)93024-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- L D Partridge
- Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque 87131, USA
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11
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Abstract
Glial cells respond to various electrical, mechanical, and chemical stimuli, including neurotransmitters, neuromodulators, and hormones, with an increase in intracellular Ca2+ concentration ([Ca2+]i). The increases exhibit a variety of temporal and spatial patterns. These [Ca2+]i responses result from the coordinated activity of a number of molecular cascades responsible for Ca2+ movement into or out of the cytoplasm either by way of the extracellular space or intracellular stores. Transplasmalemmal Ca2+ movements may be controlled by several types of voltage- and ligand-gated Ca(2+)-permeable channels as well as Ca2+ pumps and a Na+/Ca2+ exchanger. In addition, glial cells express various metabotropic receptors coupled to intracellular Ca2+ stores through the intracellular messenger inositol 1,4,5-triphosphate. The interplay of different molecular cascades enables the development of agonist-specific patterns of Ca2+ responses. Such agonist specificity may provide a means for intracellular and intercellular information coding. Calcium signals can traverse gap junctions between glial cells without decrement. These waves can serve as a substrate for integration of glial activity. By controlling gap junction conductance, Ca2+ waves may define the limits of functional glial networks. Neuronal activity can trigger [Ca2+]i signals in apposed glial cells, and moreover, there is some evidence that glial [Ca2+]i waves can affect neurons. Glial Ca2+ signaling can be regarded as a form of glial excitability.
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Affiliation(s)
- A Verkhratsky
- Department of Cellular Neurosciences, Max-Delbrück Center for Molecular Medicine, Berlin-Buch, Germany
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Affiliation(s)
- D Schild
- Physiologisches Institut, Universität Göttingen, Germany.
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13
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Wang SS, Augustine GJ. Confocal imaging and local photolysis of caged compounds: dual probes of synaptic function. Neuron 1995; 15:755-60. [PMID: 7576625 DOI: 10.1016/0896-6273(95)90167-1] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Chemical signals generated at synapses are highly limited in both spatial range and time course, so that experiments studying such signals must measure and manipulate them in both these dimensions. We describe an optical system that combines confocal laser scanning microscopy, to measure such signals, with focal photolysis of caged compounds. This system can elevate neurotransmitter and second messenger levels in femtoliter volumes of single dendrites within a millisecond. The method is readily combined with whole-cell patch-clamp measurements of electrical signals in brain slices. In cerebellar Purkinje cells, photolysis of caged IP3 causes spatially restricted intracellular release of Ca2+, and photolysis of a caged Ca2+ compound locally opens Ca(2+)-dependent K+ channels. Furthermore, localized photolysis of the caged neurotransmitter GABA transiently activates GABA receptors. The use of focal uncaging can yield new information about the spatial range of signaling actions at synapses.
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Affiliation(s)
- S S Wang
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710, USA
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