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Dienel GA, Schousboe A, McKenna MC, Rothman DL. A tribute to Leif Hertz: The historical context of his pioneering studies of the roles of astrocytes in brain energy metabolism, neurotransmission, cognitive functions, and pharmacology identifies important, unresolved topics for future studies. J Neurochem 2024; 168:461-495. [PMID: 36928655 DOI: 10.1111/jnc.15812] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 03/10/2023] [Accepted: 03/13/2023] [Indexed: 03/18/2023]
Abstract
Leif Hertz, M.D., D.Sc. (honōris causā) (1930-2018), was one of the original and noteworthy participants in the International Conference on Brain Energy Metabolism (ICBEM) series since its inception in 1993. The biennial ICBEM conferences are organized by neuroscientists interested in energetics and metabolism underlying neural functions; they have had a high impact on conceptual and experimental advances in these fields and on promoting collaborative interactions among neuroscientists. Leif made major contributions to ICBEM discussions and understanding of metabolic and signaling characteristics of astrocytes and their roles in brain function. His studies ranged from uptake of K+ from extracellular fluid and its stimulation of astrocytic respiration, identification, and regulation of enzymes specifically or preferentially expressed in astrocytes in the glutamate-glutamine cycle of excitatory neurotransmission, a requirement for astrocytic glycogenolysis for fueling K+ uptake, involvement of glycogen in memory consolidation in the chick, and pharmacology of astrocytes. This tribute to Leif Hertz highlights his major discoveries, the high impact of his work on astrocyte-neuron interactions, and his unparalleled influence on understanding the cellular basis of brain energy metabolism. His work over six decades has helped integrate the roles of astrocytes into neurotransmission where oxidative and glycogenolytic metabolism during neurotransmitter glutamate turnover are key aspects of astrocytic energetics. Leif recognized that brain astrocytic metabolism is greatly underestimated unless the volume fraction of astrocytes is taken into account. Adjustment for pathway rates expressed per gram tissue for volume fraction indicates that astrocytes have much higher oxidative rates than neurons and astrocytic glycogen concentrations and glycogenolytic rates during sensory stimulation in vivo are similar to those in resting and exercising muscle, respectively. These novel insights are typical of Leif's astute contributions to the energy metabolism field, and his publications have identified unresolved topics that provide the neuroscience community with challenges and opportunities for future research.
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Affiliation(s)
- Gerald A Dienel
- Department of Neurology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, 72205, USA
- Department of Cell Biology and Physiology, University of New Mexico, Albuquerque, New Mexico, 87131, USA
| | - Arne Schousboe
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, 2100, Denmark
| | - Mary C McKenna
- Department of Pediatrics and Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland, 21201, USA
| | - Douglas L Rothman
- Department of Radiology, Magnetic Resonance Research Center (MRRC), Yale University, New Haven, Connecticut, 06520, USA
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2
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Barros LF, Ruminot I, Sandoval PY, San Martín A. Enlightening brain energy metabolism. Neurobiol Dis 2023:106211. [PMID: 37352985 DOI: 10.1016/j.nbd.2023.106211] [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: 03/06/2023] [Revised: 05/06/2023] [Accepted: 06/20/2023] [Indexed: 06/25/2023] Open
Abstract
Brain tissue metabolism is distributed across several cell types and subcellular compartments, which activate at different times and with different temporal patterns. The introduction of genetically-encoded fluorescent indicators that are imaged using time-lapse microscopy has opened the possibility of studying brain metabolism at cellular and sub-cellular levels. There are indicators for sugars, monocarboxylates, Krebs cycle intermediates, amino acids, cofactors, and energy nucleotides, which inform about relative levels, concentrations and fluxes. This review offers a brief survey of the metabolic indicators that have been validated in brain cells, with some illustrative examples from the literature. Whereas only a small fraction of the metabolome is currently accessible to fluorescent probes, there are grounds to be optimistic about coming developments and the application of these tools to the study of brain disease.
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Affiliation(s)
- L F Barros
- Centro de Estudios Científicos (CECs), Valdivia, Chile; Facultad de Medicina y Ciencia, Universidad San Sebastián, Valdivia, Chile.
| | - I Ruminot
- Centro de Estudios Científicos (CECs), Valdivia, Chile; Facultad de Ciencias para el Cuidado de La Salud, Universidad San Sebastián, Valdivia, Chile
| | - P Y Sandoval
- Centro de Estudios Científicos (CECs), Valdivia, Chile; Facultad de Ciencias para el Cuidado de La Salud, Universidad San Sebastián, Valdivia, Chile
| | - A San Martín
- Centro de Estudios Científicos (CECs), Valdivia, Chile; Facultad de Ciencias para el Cuidado de La Salud, Universidad San Sebastián, Valdivia, Chile
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3
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Barros LF, Ruminot I, Sotelo-Hitschfeld T, Lerchundi R, Fernández-Moncada I. Metabolic Recruitment in Brain Tissue. Annu Rev Physiol 2023; 85:115-135. [PMID: 36270291 DOI: 10.1146/annurev-physiol-021422-091035] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Information processing imposes urgent metabolic demands on neurons, which have negligible energy stores and restricted access to fuel. Here, we discuss metabolic recruitment, the tissue-level phenomenon whereby active neurons harvest resources from their surroundings. The primary event is the neuronal release of K+ that mirrors workload. Astrocytes sense K+ in exquisite fashion thanks to their unique coexpression of NBCe1 and α2β2 Na+/K+ ATPase, and within seconds switch to Crabtree metabolism, involving GLUT1, aerobic glycolysis, transient suppression of mitochondrial respiration, and lactate export. The lactate surge serves as a secondary recruiter by inhibiting glucose consumption in distant cells. Additional recruiters are glutamate, nitric oxide, and ammonium, which signal over different spatiotemporal domains. The net outcome of these events is that more glucose, lactate, and oxygen are made available. Metabolic recruitment works alongside neurovascular coupling and various averaging strategies to support the inordinate dynamic range of individual neurons.
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Affiliation(s)
- L F Barros
- Centro de Estudios Científicos (CECs), Valdivia, Chile; .,Facultad de Medicina y Ciencia, Universidad San Sebastián, Valdivia, Chile;
| | - I Ruminot
- Centro de Estudios Científicos (CECs), Valdivia, Chile; .,Facultad de Medicina y Ciencia, Universidad San Sebastián, Valdivia, Chile;
| | - T Sotelo-Hitschfeld
- Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, Cologne, Germany
| | - R Lerchundi
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), MIRCen, Fontenay-aux-Roses, France
| | - I Fernández-Moncada
- NeuroCentre Magendie, INSERM U1215, University of Bordeaux, Bordeaux, France
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4
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Serrat R, Oliveira-Pinto A, Marsicano G, Pouvreau S. Imaging mitochondrial calcium dynamics in the central nervous system. J Neurosci Methods 2022; 373:109560. [PMID: 35320763 DOI: 10.1016/j.jneumeth.2022.109560] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 03/04/2022] [Accepted: 03/06/2022] [Indexed: 12/28/2022]
Abstract
Mitochondrial calcium handling is a particularly active research area in the neuroscience field, as it plays key roles in the regulation of several functions of the central nervous system, such as synaptic transmission and plasticity, astrocyte calcium signaling, neuronal activity… In the last few decades, a panel of techniques have been developed to measure mitochondrial calcium dynamics, relying mostly on photonic microscopy, and including synthetic sensors, hybrid sensors and genetically encoded calcium sensors. The goal of this review is to endow the reader with a deep knowledge of the historical and latest tools to monitor mitochondrial calcium events in the brain, as well as a comprehensive overview of the current state of the art in brain mitochondrial calcium signaling. We will discuss the main calcium probes used in the field, their mitochondrial targeting strategies, their key properties and major drawbacks. In addition, we will detail the main roles of mitochondrial calcium handling in neuronal tissues through an extended report of the recent studies using mitochondrial targeted calcium sensors in neuronal and astroglial cells, in vitro and in vivo.
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Affiliation(s)
- Roman Serrat
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1215 NeuroCentre Magendie, France; University of Bordeaux, Bordeaux 33077, France
| | - Alexandre Oliveira-Pinto
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1215 NeuroCentre Magendie, France; University of Bordeaux, Bordeaux 33077, France
| | - Giovanni Marsicano
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1215 NeuroCentre Magendie, France; University of Bordeaux, Bordeaux 33077, France
| | - Sandrine Pouvreau
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1215 NeuroCentre Magendie, France; University of Bordeaux, Bordeaux 33077, France.
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5
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San Martín A, Arce-Molina R, Aburto C, Baeza-Lehnert F, Barros LF, Contreras-Baeza Y, Pinilla A, Ruminot I, Rauseo D, Sandoval PY. Visualizing physiological parameters in cells and tissues using genetically encoded indicators for metabolites. Free Radic Biol Med 2022; 182:34-58. [PMID: 35183660 DOI: 10.1016/j.freeradbiomed.2022.02.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Revised: 02/08/2022] [Accepted: 02/10/2022] [Indexed: 02/07/2023]
Abstract
The study of metabolism is undergoing a renaissance. Since the year 2002, over 50 genetically-encoded fluorescent indicators (GEFIs) have been introduced, capable of monitoring metabolites with high spatial/temporal resolution using fluorescence microscopy. Indicators are fusion proteins that change their fluorescence upon binding a specific metabolite. There are indicators for sugars, monocarboxylates, Krebs cycle intermediates, amino acids, cofactors, and energy nucleotides. They permit monitoring relative levels, concentrations, and fluxes in living systems. At a minimum they report relative levels and, in some cases, absolute concentrations may be obtained by performing ad hoc calibration protocols. Proper data collection, processing, and interpretation are critical to take full advantage of these new tools. This review offers a survey of the metabolic indicators that have been validated in mammalian systems. Minimally invasive, these indicators have been instrumental for the purposes of confirmation, rebuttal and discovery. We envision that this powerful technology will foster metabolic physiology.
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Affiliation(s)
- A San Martín
- Centro de Estudios Científicos (CECs), Valdivia, Chile.
| | - R Arce-Molina
- Centro de Estudios Científicos (CECs), Valdivia, Chile
| | - C Aburto
- Centro de Estudios Científicos (CECs), Valdivia, Chile; Universidad Austral de Chile, Valdivia, Chile
| | | | - L F Barros
- Centro de Estudios Científicos (CECs), Valdivia, Chile
| | - Y Contreras-Baeza
- Centro de Estudios Científicos (CECs), Valdivia, Chile; Universidad Austral de Chile, Valdivia, Chile
| | - A Pinilla
- Centro de Estudios Científicos (CECs), Valdivia, Chile; Universidad Austral de Chile, Valdivia, Chile
| | - I Ruminot
- Centro de Estudios Científicos (CECs), Valdivia, Chile
| | - D Rauseo
- Centro de Estudios Científicos (CECs), Valdivia, Chile; Universidad Austral de Chile, Valdivia, Chile
| | - P Y Sandoval
- Centro de Estudios Científicos (CECs), Valdivia, Chile
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6
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Vicencio-Jimenez S, Villalobos M, Maldonado PE, Vergara RC. The Energy Homeostasis Principle: A Naturalistic Approach to Explain the Emergence of Behavior. Front Syst Neurosci 2022; 15:782781. [PMID: 35069133 PMCID: PMC8770284 DOI: 10.3389/fnsys.2021.782781] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Accepted: 12/13/2021] [Indexed: 11/13/2022] Open
Abstract
It is still elusive to explain the emergence of behavior and understanding based on its neural mechanisms. One renowned proposal is the Free Energy Principle (FEP), which uses an information-theoretic framework derived from thermodynamic considerations to describe how behavior and understanding emerge. FEP starts from a whole-organism approach, based on mental states and phenomena, mapping them into the neuronal substrate. An alternative approach, the Energy Homeostasis Principle (EHP), initiates a similar explanatory effort but starts from single-neuron phenomena and builds up to whole-organism behavior and understanding. In this work, we further develop the EHP as a distinct but complementary vision to FEP and try to explain how behavior and understanding would emerge from the local requirements of the neurons. Based on EHP and a strict naturalist approach that sees living beings as physical and deterministic systems, we explain scenarios where learning would emerge without the need for volition or goals. Given these starting points, we state several considerations of how we see the nervous system, particularly the role of the function, purpose, and conception of goal-oriented behavior. We problematize these conceptions, giving an alternative teleology-free framework in which behavior and, ultimately, understanding would still emerge. We reinterpret neural processing by explaining basic learning scenarios up to simple anticipatory behavior. Finally, we end the article with an evolutionary perspective of how this non-goal-oriented behavior appeared. We acknowledge that our proposal, in its current form, is still far from explaining the emergence of understanding. Nonetheless, we set the ground for an alternative neuron-based framework to ultimately explain understanding.
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Affiliation(s)
- Sergio Vicencio-Jimenez
- The Center for Hearing and Balance, Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Mario Villalobos
- Escuela de Psicología y Filosofía, Universidad de Tarapacá, Arica, Chile
| | - Pedro E. Maldonado
- Laboratorio de Neurosistemas, Departamento de Neurociencia & BNI, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Rodrigo C. Vergara
- Departamento de Kinesiología, Facultad de Artes y Educación Física, Universidad Metropolitana de las Ciencias de la Educación, Ñuñoa, Chile
- *Correspondence: Rodrigo C. Vergara
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7
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Energy matters: presynaptic metabolism and the maintenance of synaptic transmission. Nat Rev Neurosci 2021; 23:4-22. [PMID: 34782781 DOI: 10.1038/s41583-021-00535-8] [Citation(s) in RCA: 58] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/13/2021] [Indexed: 12/14/2022]
Abstract
Synaptic activity imposes large energy demands that are met by local adenosine triphosphate (ATP) synthesis through glycolysis and mitochondrial oxidative phosphorylation. ATP drives action potentials, supports synapse assembly and remodelling, and fuels synaptic vesicle filling and recycling, thus sustaining synaptic transmission. Given their polarized morphological features - including long axons and extensive branching in their terminal regions - neurons face exceptional challenges in maintaining presynaptic energy homeostasis, particularly during intensive synaptic activity. Recent studies have started to uncover the mechanisms and signalling pathways involved in activity-dependent and energy-sensitive regulation of presynaptic energetics, or 'synaptoenergetics'. These conceptual advances have established the energetic regulation of synaptic efficacy and plasticity as an exciting research field that is relevant to a range of neurological disorders associated with bioenergetic failure and synaptic dysfunction.
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8
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Lujan BJ, Singh M, Singh A, Renden RB. Developmental shift to mitochondrial respiration for energetic support of sustained transmission during maturation at the calyx of Held. J Neurophysiol 2021; 126:976-996. [PMID: 34432991 PMCID: PMC8560424 DOI: 10.1152/jn.00333.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 08/11/2021] [Accepted: 08/11/2021] [Indexed: 11/24/2022] Open
Abstract
A considerable amount of energy is expended following presynaptic activity to regenerate electrical polarization and maintain efficient release and recycling of neurotransmitter. Mitochondria are the major suppliers of neuronal energy, generating ATP via oxidative phosphorylation. However, the specific utilization of energy from cytosolic glycolysis rather than mitochondrial respiration at the presynaptic terminal during synaptic activity remains unclear and controversial. We use a synapse specialized for high-frequency transmission in mice, the calyx of Held, to test the sources of energy used to maintain energy during short activity bursts (<1 s) and sustained neurotransmission (30-150 s). We dissect the role of presynaptic glycolysis versus mitochondrial respiration by acutely and selectively blocking these ATP-generating pathways in a synaptic preparation where mitochondria and synaptic vesicles are prolific, under near-physiological conditions. Surprisingly, if either glycolysis or mitochondrial ATP production is intact, transmission during repetitive short bursts of activity is not affected. In slices from young animals before the onset of hearing, where the synapse is not yet fully specialized, both glycolytic and mitochondrial ATP production are required to support sustained, high-frequency neurotransmission. In mature synapses, sustained transmission relies exclusively on mitochondrial ATP production supported by bath lactate, but not glycolysis. At both ages, we observe that action potential propagation begins to fail before defects in synaptic vesicle recycling. Our data describe a specific metabolic profile to support high-frequency information transmission at the mature calyx of Held, shifting during postnatal synaptic maturation from glycolysis to rely on monocarboxylates as a fuel source.NEW & NOTEWORTHY We dissect the role of presynaptic glycolysis versus mitochondrial respiration in supporting high-frequency neurotransmission, by acutely blocking these ATP-generating pathways at a synapse tuned for high-frequency transmission. We find that massive energy expenditure is required to generate failure when only one pathway is inhibited. Action potential propagation is lost before impaired synaptic vesicle recycling. Synaptic transmission is exclusively dependent on oxidative phosphorylation in mature synapses, indicating presynaptic glycolysis may be dispensable for ATP maintenance.
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Affiliation(s)
- Brendan J Lujan
- Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, Nevada
| | - Mahendra Singh
- Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, Nevada
| | - Abhyudai Singh
- Electrical & Computer Engineering, University of Delaware, Newark, Delaware
| | - Robert B Renden
- Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, Nevada
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9
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Köhler S, Schmidt H, Fülle P, Hirrlinger J, Winkler U. A Dual Nanosensor Approach to Determine the Cytosolic Concentration of ATP in Astrocytes. Front Cell Neurosci 2020; 14:565921. [PMID: 33192312 PMCID: PMC7530325 DOI: 10.3389/fncel.2020.565921] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 08/26/2020] [Indexed: 11/17/2022] Open
Abstract
Adenosine triphosphate (ATP) is the central energy carrier of all cells and knowledge on the dynamics of the concentration of ATP ([ATP]) provides important insights into the energetic state of a cell. Several genetically encoded fluorescent nanosensors for ATP were developed, which allow following the cytosolic [ATP] at high spatial and temporal resolution using fluorescence microscopy. However, to calibrate the fluorescent signal to [ATP] has remained challenging. To estimate basal cytosolic [ATP] ([ATP]0) in astrocytes, we here took advantage of two ATP nanosensors of the ATeam-family (ATeam1.03; ATeam1.03YEMK) with different affinities for ATP. Altering [ATP] by external stimuli resulted in characteristic pairs of signal changes of both nanosensors, which depend on [ATP]0. Using this dual nanosensor strategy and epifluorescence microscopy, [ATP]0 was estimated to be around 1.5 mM in primary cultures of cortical astrocytes from mice. Furthermore, in astrocytes in acutely isolated cortical slices from mice expressing both nanosensors after stereotactic injection of AAV-vectors, 2-photon microscopy revealed [ATP]0 of 0.7 mM to 1.3 mM. Finally, the change in [ATP] induced in the cytosol of cultured cortical astrocytes by application of azide, glutamate, and an increased extracellular concentration of K+ were calculated as −0.50 mM, −0.16 mM, and 0.07 mM, respectively. In summary, the dual nanosensor approach adds another option for determining the concentration of [ATP] to the increasing toolbox of fluorescent nanosensors for metabolites. This approach can also be applied to other metabolites when two sensors with different binding properties are available.
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Affiliation(s)
- Susanne Köhler
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University Leipzig, Leipzig, Germany
| | - Hartmut Schmidt
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University Leipzig, Leipzig, Germany
| | - Paula Fülle
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University Leipzig, Leipzig, Germany.,Wilhelm-Ostwald-Schule, Gymnasium der Stadt Leipzig, Leipzig, Germany
| | - Johannes Hirrlinger
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University Leipzig, Leipzig, Germany.,Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Göttingen, Germany
| | - Ulrike Winkler
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University Leipzig, Leipzig, Germany
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10
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Natsubori A, Tsunematsu T, Karashima A, Imamura H, Kabe N, Trevisiol A, Hirrlinger J, Kodama T, Sanagi T, Masamoto K, Takata N, Nave KA, Matsui K, Tanaka KF, Honda M. Intracellular ATP levels in mouse cortical excitatory neurons varies with sleep-wake states. Commun Biol 2020; 3:491. [PMID: 32895482 PMCID: PMC7477120 DOI: 10.1038/s42003-020-01215-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 07/31/2020] [Indexed: 02/06/2023] Open
Abstract
Whilst the brain is assumed to exert homeostatic functions to keep the cellular energy status constant under physiological conditions, this has not been experimentally proven. Here, we conducted in vivo optical recordings of intracellular concentration of adenosine 5’-triphosphate (ATP), the major cellular energy metabolite, using a genetically encoded sensor in the mouse brain. We demonstrate that intracellular ATP levels in cortical excitatory neurons fluctuate in a cortex-wide manner depending on the sleep-wake states, correlating with arousal. Interestingly, ATP levels profoundly decreased during rapid eye movement sleep, suggesting a negative energy balance in neurons despite a simultaneous increase in cerebral hemodynamics for energy supply. The reduction in intracellular ATP was also observed in response to local electrical stimulation for neuronal activation, whereas the hemodynamics were simultaneously enhanced. These observations indicate that cerebral energy metabolism may not always meet neuronal energy demands, consequently resulting in physiological fluctuations of intracellular ATP levels in neurons. Akiyo Natsubori et al. use a genetically encoded sensor to measure intracellular ATP levels in mouse cortical excitatory neurons in vivo. They show cortex-wide variations in ATP levels across sleep-wake states, and that cerebral energy metabolism does not always meet neuronal energy demands.
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Affiliation(s)
- Akiyo Natsubori
- Sleep Disorders Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-Ku, Tokyo, 156-8506, Japan.
| | - Tomomi Tsunematsu
- Super-network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Sendai, 980-8578, Japan.,Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Kawaguchi, 332-0012, Japan.,Advanced Interdisciplinary Research Division, Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai, 980-8578, Japan
| | - Akihiro Karashima
- Tohoku Institute of Technology, 35-1, Yagiyama Kasumi-cho, Taihaku-ku, Sendai, 982-8577, Japan
| | - Hiromi Imamura
- Graduate School of Biostudies, Kyoto University, Yoshida-konoe-cho, Sakyo-ku, Kyoto, 606-8501, Japan
| | - Naoya Kabe
- Neural Prosthesis Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo, 156-8506, Japan
| | - Andrea Trevisiol
- Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Gottingen, 37075, Germany
| | - Johannes Hirrlinger
- Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Gottingen, 37075, Germany.,Carl-Ludwig-Institute for Physiology, University of Leipzig, Liebigstrasse 27, 04103, Leipzig, Germany
| | - Tohru Kodama
- Sleep Disorders Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-Ku, Tokyo, 156-8506, Japan
| | - Tomomi Sanagi
- Advanced Interdisciplinary Research Division, Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai, 980-8578, Japan
| | - Kazuto Masamoto
- Department of Mechanical and Intelligent Systems Engineering, University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo, 182-8585, Japan
| | - Norio Takata
- Department of Neuropsychiatry, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Gottingen, 37075, Germany
| | - Ko Matsui
- Super-network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Sendai, 980-8578, Japan
| | - Kenji F Tanaka
- Department of Neuropsychiatry, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan
| | - Makoto Honda
- Sleep Disorders Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-Ku, Tokyo, 156-8506, Japan
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11
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Barros LF, Ruminot I, San Martín A, Lerchundi R, Fernández-Moncada I, Baeza-Lehnert F. Aerobic Glycolysis in the Brain: Warburg and Crabtree Contra Pasteur. Neurochem Res 2020; 46:15-22. [PMID: 31981059 DOI: 10.1007/s11064-020-02964-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 01/10/2020] [Accepted: 01/16/2020] [Indexed: 12/20/2022]
Abstract
Information processing is onerous. Curiously, active brain tissue does not fully oxidize glucose and instead generates a local surplus of lactate, a phenomenon termed aerobic glycolysis. Why engage in inefficient ATP production by glycolysis when energy demand is highest and oxygen is plentiful? Aerobic glycolysis is associated to classic biochemical effects known by the names of Pasteur, Warburg and Crabtree. Here we discuss these three interdependent phenomena in brain cells, in light of high-resolution data of neuronal and astrocytic metabolism in culture, tissue slices and in vivo, acquired with genetically-encoded fluorescent sensors. These sensors are synthetic proteins that can be targeted to specific cell types and subcellular compartments, which change their fluorescence in response to variations in metabolite concentration. A major site of acute aerobic glycolysis is the astrocyte. In this cell, a Crabtree effect triggered by K+ coincides with a Warburg effect mediated by NO, superimposed on a slower longer-lasting Warburg effect caused by glutamate and possibly by NH4+. The compounded outcome is that more fuel (lactate) and more oxygen are made available to neurons, on demand. Meanwhile neurons consume both glucose and lactate, maintaining a strict balance between glycolysis and respiration, commanded by the Na+ pump. We conclude that activity-dependent Warburg and Crabtree effects in brain tissue, and the resulting aerobic glycolysis, do not reflect inefficient energy generation but the marshalling of astrocytes for the purpose of neuronal ATP generation. It remains to be seen whether neurons contribute to aerobic glycolysis under physiological conditions.
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Affiliation(s)
- L Felipe Barros
- Centro de Estudios Científicos-CECs, 5110466, Valdivia, Chile.
| | - Iván Ruminot
- Centro de Estudios Científicos-CECs, 5110466, Valdivia, Chile
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12
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Vergara RC, Jaramillo-Riveri S, Luarte A, Moënne-Loccoz C, Fuentes R, Couve A, Maldonado PE. The Energy Homeostasis Principle: Neuronal Energy Regulation Drives Local Network Dynamics Generating Behavior. Front Comput Neurosci 2019; 13:49. [PMID: 31396067 PMCID: PMC6664078 DOI: 10.3389/fncom.2019.00049] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 07/01/2019] [Indexed: 01/12/2023] Open
Abstract
A major goal of neuroscience is understanding how neurons arrange themselves into neural networks that result in behavior. Most theoretical and experimental efforts have focused on a top-down approach which seeks to identify neuronal correlates of behaviors. This has been accomplished by effectively mapping specific behaviors to distinct neural patterns, or by creating computational models that produce a desired behavioral outcome. Nonetheless, these approaches have only implicitly considered the fact that neural tissue, like any other physical system, is subjected to several restrictions and boundaries of operations. Here, we proposed a new, bottom-up conceptual paradigm: The Energy Homeostasis Principle, where the balance between energy income, expenditure, and availability are the key parameters in determining the dynamics of neuronal phenomena found from molecular to behavioral levels. Neurons display high energy consumption relative to other cells, with metabolic consumption of the brain representing 20% of the whole-body oxygen uptake, contrasting with this organ representing only 2% of the body weight. Also, neurons have specialized surrounding tissue providing the necessary energy which, in the case of the brain, is provided by astrocytes. Moreover, and unlike other cell types with high energy demands such as muscle cells, neurons have strict aerobic metabolism. These facts indicate that neurons are highly sensitive to energy limitations, with Gibb's free energy dictating the direction of all cellular metabolic processes. From this activity, the largest energy, by far, is expended by action potentials and post-synaptic potentials; therefore, plasticity can be reinterpreted in terms of their energy context. Consequently, neurons, through their synapses, impose energy demands over post-synaptic neurons in a close loop-manner, modulating the dynamics of local circuits. Subsequently, the energy dynamics end up impacting the homeostatic mechanisms of neuronal networks. Furthermore, local energy management also emerges as a neural population property, where most of the energy expenses are triggered by sensory or other modulatory inputs. Local energy management in neurons may be sufficient to explain the emergence of behavior, enabling the assessment of which properties arise in neural circuits and how. Essentially, the proposal of the Energy Homeostasis Principle is also readily testable for simple neuronal networks.
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Affiliation(s)
- Rodrigo C Vergara
- Neurosystems Laboratory, Faculty of Medicine, Biomedical Neuroscience Institute, Universidad de Chile, Santiago, Chile
| | - Sebastián Jaramillo-Riveri
- School of Biological Sciences, Institute of Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - Alejandro Luarte
- Cellular and Molecular Neurobiology Laboratory, Faculty of Medicine, Biomedical Neuroscience Institute, Universidad de Chile, Santiago, Chile
| | - Cristóbal Moënne-Loccoz
- Motor Control Laboratory, Faculty of Medicine, Biomedical Neuroscience Institute, Universidad de Chile, Santiago, Chile.,Department of Health Sciences, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Rómulo Fuentes
- Motor Control Laboratory, Faculty of Medicine, Biomedical Neuroscience Institute, Universidad de Chile, Santiago, Chile
| | - Andrés Couve
- Cellular and Molecular Neurobiology Laboratory, Faculty of Medicine, Biomedical Neuroscience Institute, Universidad de Chile, Santiago, Chile
| | - Pedro E Maldonado
- Neurosystems Laboratory, Faculty of Medicine, Biomedical Neuroscience Institute, Universidad de Chile, Santiago, Chile
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13
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Baeza-Lehnert F, Saab AS, Gutiérrez R, Larenas V, Díaz E, Horn M, Vargas M, Hösli L, Stobart J, Hirrlinger J, Weber B, Barros LF. Non-Canonical Control of Neuronal Energy Status by the Na + Pump. Cell Metab 2019; 29:668-680.e4. [PMID: 30527744 DOI: 10.1016/j.cmet.2018.11.005] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 08/01/2018] [Accepted: 11/12/2018] [Indexed: 12/31/2022]
Abstract
Neurons have limited intracellular energy stores but experience acute and unpredictable increases in energy demand. To better understand how these cells repeatedly transit from a resting to active state without undergoing metabolic stress, we monitored their early metabolic response to neurotransmission using ion-sensitive probes and FRET sensors in vitro and in vivo. A short theta burst triggered immediate Na+ entry, followed by a delayed stimulation of the Na+/K+ ATPase pump. Unexpectedly, cytosolic ATP and ADP levels were unperturbed across a wide range of physiological workloads, revealing strict flux coupling between the Na+ pump and mitochondria. Metabolic flux measurements revealed a "priming" phase of mitochondrial energization by pyruvate, whereas glucose consumption coincided with delayed Na+ pump stimulation. Experiments revealed that the Na+ pump plays a permissive role for mitochondrial ATP production and glycolysis. We conclude that neuronal energy homeostasis is not mediated by adenine nucleotides or by Ca2+, but by a mechanism commanded by the Na+ pump.
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Affiliation(s)
- Felipe Baeza-Lehnert
- Centro de Estudios Científicos (CECs), Casilla 1469, 5110466 Valdivia, Chile; Universidad Austral de Chile, Valdivia, Chile
| | - Aiman S Saab
- Institute of Pharmacology and Toxicology, University and ETH Zurich, Switzerland; Neuroscience Center Zurich, Zurich, Switzerland
| | - Robin Gutiérrez
- Centro de Estudios Científicos (CECs), Casilla 1469, 5110466 Valdivia, Chile; Universidad Austral de Chile, Valdivia, Chile
| | - Valeria Larenas
- Centro de Estudios Científicos (CECs), Casilla 1469, 5110466 Valdivia, Chile
| | - Esteban Díaz
- Centro de Estudios Científicos (CECs), Casilla 1469, 5110466 Valdivia, Chile; Universidad Austral de Chile, Valdivia, Chile
| | - Melanie Horn
- Centro de Estudios Científicos (CECs), Casilla 1469, 5110466 Valdivia, Chile
| | - Miriam Vargas
- Centro de Estudios Científicos (CECs), Casilla 1469, 5110466 Valdivia, Chile; Universidad Austral de Chile, Valdivia, Chile
| | - Ladina Hösli
- Institute of Pharmacology and Toxicology, University and ETH Zurich, Switzerland; Neuroscience Center Zurich, Zurich, Switzerland
| | - Jillian Stobart
- Institute of Pharmacology and Toxicology, University and ETH Zurich, Switzerland; Neuroscience Center Zurich, Zurich, Switzerland
| | - Johannes Hirrlinger
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, 04103 Leipzig, Germany; Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Hermann-Rein-Str. 3, 37075 Göttingen, Germany
| | - Bruno Weber
- Institute of Pharmacology and Toxicology, University and ETH Zurich, Switzerland; Neuroscience Center Zurich, Zurich, Switzerland
| | - L Felipe Barros
- Centro de Estudios Científicos (CECs), Casilla 1469, 5110466 Valdivia, Chile.
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14
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Trevisiol A, Saab AS, Winkler U, Marx G, Imamura H, Möbius W, Kusch K, Nave KA, Hirrlinger J. Monitoring ATP dynamics in electrically active white matter tracts. eLife 2017; 6. [PMID: 28414271 PMCID: PMC5415357 DOI: 10.7554/elife.24241] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 04/16/2017] [Indexed: 11/24/2022] Open
Abstract
In several neurodegenerative diseases and myelin disorders, the degeneration profiles of myelinated axons are compatible with underlying energy deficits. However, it is presently impossible to measure selectively axonal ATP levels in the electrically active nervous system. We combined transgenic expression of an ATP-sensor in neurons of mice with confocal FRET imaging and electrophysiological recordings of acutely isolated optic nerves. This allowed us to monitor dynamic changes and activity-dependent axonal ATP homeostasis at the cellular level and in real time. We find that changes in ATP levels correlate well with compound action potentials. However, this correlation is disrupted when metabolism of lactate is inhibited, suggesting that axonal glycolysis products are not sufficient to maintain mitochondrial energy metabolism of electrically active axons. The combined monitoring of cellular ATP and electrical activity is a novel tool to study neuronal and glial energy metabolism in normal physiology and in models of neurodegenerative disorders. DOI:http://dx.doi.org/10.7554/eLife.24241.001 The brain contains an intricate network of nerve cells that receive, process, send and store information. This information travels as electrical impulses along a long, thin part of each nerve cell known as the nerve fiber or axon. The act of sending these electrical signals requires a lot of energy, and energy in cells is most often stored within molecules of adenosine triphosphate (called ATP for short). Importantly, a better understanding of how the production and consumption of ATP in nerve cells relates to electrical activity would help scientists to better understand how a shortage of energy in the brain contributes to diseases like multiple sclerosis. However, to date, it has been challenging to study the dynamics of ATP in nerve cells that are active. Now, Trevisiol et al. describe a new system that allows changes in ATP levels to be seen within active nerve cells. First, mice were genetically engineered to produce a molecule that works like an ATP sensor only in their nerve cells. This made it possible to visualize the amount of ATP inside the axons in real-time using a microscope. Measuring ATP levels and recording the electrical signals moving along an axon at the same time allowed Trevisiol et al. to see how ATP content and electrical activity correlate and regulate each other. The experiments reveal that strong electrical activity reduces the ATP content of the axon. Trevisiol et al. also discovered that nerve cells are unable to generate enough energy on their own to sustain their electrical activity. These results provide evidence that other cells in the brain – most likely non-nerve cells called oligodendrocytes – play an active role in delivering energy-rich substances to the axons of nerve cells. In the future, the same tools and approaches could be used to monitor ATP levels and electrical activity in mice that model neurological disorders. Such experiments could tell scientists more about how disturbing energy production in nerve cells affects these diseases. DOI:http://dx.doi.org/10.7554/eLife.24241.002
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Affiliation(s)
- Andrea Trevisiol
- Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Göttingen, Germany
| | - Aiman S Saab
- Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Göttingen, Germany.,Institute of Pharmacology & Toxicology, University of Zurich, Zurich, Switzerland.,Neuroscience Center Zurich, University of Zurich, Zurich, Switzerland
| | - Ulrike Winkler
- Carl-Ludwig-Institute for Physiology, University of Leipzig, Leipzig, Germany
| | - Grit Marx
- Carl-Ludwig-Institute for Physiology, University of Leipzig, Leipzig, Germany
| | - Hiromi Imamura
- Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Wiebke Möbius
- Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Göttingen, Germany.,Center Nanoscale Microscopy and Molecular Physiology of the Brain, Göttingen, Germany
| | - Kathrin Kusch
- Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Göttingen, Germany
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Göttingen, Germany
| | - Johannes Hirrlinger
- Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Göttingen, Germany.,Carl-Ludwig-Institute for Physiology, University of Leipzig, Leipzig, Germany
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15
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Winkler U, Seim P, Enzbrenner Y, Köhler S, Sicker M, Hirrlinger J. Activity-dependent modulation of intracellular ATP in cultured cortical astrocytes. J Neurosci Res 2017; 95:2172-2181. [PMID: 28151554 DOI: 10.1002/jnr.24020] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 12/15/2016] [Accepted: 12/21/2016] [Indexed: 01/21/2023]
Abstract
Brain function is absolutely dependent on an appropriate supply of energy. A shortfall in supply-as occurs, for instance, following stroke-can lead rapidly to irreversible damage to this vital organ. While the consequences of pathophysiological energy depletion have been well documented, much less is known about the physiological energy dynamics of brain cells, although changes in the intracellular concentration of adenosine triphosphate (ATP), the major energy carrier of cells, have been postulated to contribute to cellular signaling. To address this issue more closely, we have investigated intracellular ATP in cultured primary cortical astrocytes by time-lapse microscopy using a genetically encoded fluorescent sensor for ATP. The cytosolic ATP sensor signal decreased after application of the neurotransmitter glutamate in a manner dependent on both glutamate concentration and glutamate transporter activity, but independent of glutamate receptors. The application of dopamine did not affect ATP levels within astrocytes. These results confirm that intracellular ATP levels in astrocytes do indeed respond to changes in physiological activity and pave the way for further studies addressing factors that affect regulation of ATP. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Ulrike Winkler
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Pauline Seim
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Yvonne Enzbrenner
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Susanne Köhler
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Marit Sicker
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Johannes Hirrlinger
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany.,Department of Neurogenetics, Max Planck Institute for Experimental Medicine, Göttingen, Germany
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16
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Rae C, Sonnewald U. Astrocytes, Metabolism, Signaling and Brain Drains: Introduction to the Special Issue in Honor of Gerald Dienel. Neurochem Res 2016; 40:2383-5. [PMID: 26613618 DOI: 10.1007/s11064-015-1781-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Caroline Rae
- Neuroscience Research Australian & The University of New South Wales, Randwick, NSW, Australia.
| | - Ursula Sonnewald
- Norwegian University of Science and Technology (NTNU), Trondheim, Norway
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