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Wise DL, Escobedo-Lozoya Y, Valakh V, Gao EY, Bhonsle A, Lei QL, Cheng X, Greene SB, Van Hooser SD, Nelson SB. Prolonged Activity Deprivation Causes Pre- and Postsynaptic Compensatory Plasticity at Neocortical Excitatory Synapses. eNeuro 2024; 11:ENEURO.0366-23.2024. [PMID: 38777611 PMCID: PMC11163391 DOI: 10.1523/eneuro.0366-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 05/10/2024] [Accepted: 05/15/2024] [Indexed: 05/25/2024] Open
Abstract
Homeostatic plasticity stabilizes firing rates of neurons, but the pressure to restore low activity rates can significantly alter synaptic and cellular properties. Most previous studies of homeostatic readjustment to complete activity silencing in rodent forebrain have examined changes after 2 d of deprivation, but it is known that longer periods of deprivation can produce adverse effects. To better understand the mechanisms underlying these effects and to address how presynaptic as well as postsynaptic compartments change during homeostatic plasticity, we subjected mouse cortical slice cultures to a more severe 5 d deprivation paradigm. We developed and validated a computational framework to measure the number and morphology of presynaptic and postsynaptic compartments from super-resolution light microscopy images of dense cortical tissue. Using these tools, combined with electrophysiological miniature excitatory postsynaptic current measurements, and synaptic imaging at the electron microscopy level, we assessed the functional and morphological results of prolonged deprivation. Excitatory synapses were strengthened both presynaptically and postsynaptically. Surprisingly, we also observed a decrement in the density of excitatory synapses, both as measured from colocalized staining of pre- and postsynaptic proteins in tissue and from the number of dendritic spines. Overall, our results suggest that cortical networks deprived of activity progressively move toward a smaller population of stronger synapses.
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Affiliation(s)
- Derek L Wise
- Department of Biology, Brandeis University, Waltham, Massachusetts 02454 9110
| | | | - Vera Valakh
- Department of Biology, Brandeis University, Waltham, Massachusetts 02454 9110
| | - Emma Y Gao
- Department of Biology, Brandeis University, Waltham, Massachusetts 02454 9110
| | - Aishwarya Bhonsle
- Department of Biology, Brandeis University, Waltham, Massachusetts 02454 9110
| | - Qian L Lei
- Department of Biology, Brandeis University, Waltham, Massachusetts 02454 9110
| | - Xinyu Cheng
- Department of Biology, Brandeis University, Waltham, Massachusetts 02454 9110
| | - Samuel B Greene
- Department of Biology, Brandeis University, Waltham, Massachusetts 02454 9110
| | | | - Sacha B Nelson
- Department of Biology, Brandeis University, Waltham, Massachusetts 02454 9110
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2
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Sun SED, Levenstein D, Li B, Mandelberg N, Chenouard N, Suutari BS, Sanchez S, Tian G, Rinzel J, Buzsáki G, Tsien RW. Synaptic homeostasis transiently leverages Hebbian mechanisms for a multiphasic response to inactivity. Cell Rep 2024; 43:113839. [PMID: 38507409 DOI: 10.1016/j.celrep.2024.113839] [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: 09/13/2022] [Revised: 12/19/2023] [Accepted: 02/05/2024] [Indexed: 03/22/2024] Open
Abstract
Homeostatic regulation of synapses is vital for nervous system function and key to understanding a range of neurological conditions. Synaptic homeostasis is proposed to operate over hours to counteract the destabilizing influence of long-term potentiation (LTP) and long-term depression (LTD). The prevailing view holds that synaptic scaling is a slow first-order process that regulates postsynaptic glutamate receptors and fundamentally differs from LTP or LTD. Surprisingly, we find that the dynamics of scaling induced by neuronal inactivity are not exponential or monotonic, and the mechanism requires calcineurin and CaMKII, molecules dominant in LTD and LTP. Our quantitative model of these enzymes reconstructs the unexpected dynamics of homeostatic scaling and reveals how synapses can efficiently safeguard future capacity for synaptic plasticity. This mechanism of synaptic adaptation supports a broader set of homeostatic changes, including action potential autoregulation, and invites further inquiry into how such a mechanism varies in health and disease.
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Affiliation(s)
- Simón E D Sun
- Center for Neural Science, New York University, New York, NY 10003, USA; Department of Neuroscience and Physiology, Neuroscience Institute, New York University Langone Health, New York, NY 10016, USA; Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
| | - Daniel Levenstein
- Center for Neural Science, New York University, New York, NY 10003, USA; Department of Neuroscience and Physiology, Neuroscience Institute, New York University Langone Health, New York, NY 10016, USA; Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, 3810 University Street, Montreal, QC, Canada
| | - Boxing Li
- Department of Neuroscience and Physiology, Neuroscience Institute, New York University Langone Health, New York, NY 10016, USA; Neuroscience Program, Guangdong Provincial Key Laboratory of Brain Function and Disease, Zhongshan School of Medicine and the Fifth Affiliated Hospital, Sun Yat-sen University, Guangzhou 510810, China
| | - Nataniel Mandelberg
- Department of Neuroscience and Physiology, Neuroscience Institute, New York University Langone Health, New York, NY 10016, USA
| | - Nicolas Chenouard
- Department of Neuroscience and Physiology, Neuroscience Institute, New York University Langone Health, New York, NY 10016, USA; Sorbonne Université, INSERM U1127, UMR CNRS 7225, Institut du Cerveau (ICM), 47 bld de l'hôpital, 75013 Paris, France
| | - Benjamin S Suutari
- Center for Neural Science, New York University, New York, NY 10003, USA; Department of Neuroscience and Physiology, Neuroscience Institute, New York University Langone Health, New York, NY 10016, USA
| | - Sandrine Sanchez
- Department of Neuroscience and Physiology, Neuroscience Institute, New York University Langone Health, New York, NY 10016, USA
| | - Guoling Tian
- Department of Neuroscience and Physiology, Neuroscience Institute, New York University Langone Health, New York, NY 10016, USA
| | - John Rinzel
- Center for Neural Science, New York University, New York, NY 10003, USA
| | - György Buzsáki
- Department of Neuroscience and Physiology, Neuroscience Institute, New York University Langone Health, New York, NY 10016, USA
| | - Richard W Tsien
- Center for Neural Science, New York University, New York, NY 10003, USA; Department of Neuroscience and Physiology, Neuroscience Institute, New York University Langone Health, New York, NY 10016, USA.
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3
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Kim SR, Eom Y, Lee SH. Comprehensive analysis of sex differences in the function and ultrastructure of hippocampal presynaptic terminals. Neurochem Int 2023; 169:105570. [PMID: 37451344 DOI: 10.1016/j.neuint.2023.105570] [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: 01/25/2023] [Revised: 05/08/2023] [Accepted: 07/04/2023] [Indexed: 07/18/2023]
Abstract
Sex differences in the brain, encompassing variations in specific brain structures, size, cognitive function, and synaptic connections, have been identified across numerous species. While previous research has explored sex differences in postsynaptic structures, synaptic plasticity, and hippocampus-dependent functions, the hippocampal presynaptic terminals remain largely uninvestigated. The hippocampus is a critical structure responsible for multiple brain functions. This study examined presynaptic differences in cultured hippocampal neurons derived from male and female mice using a combination of biochemical assays, functional analyses measuring exocytosis and endocytosis of synaptic vesicle proteins, ultrastructural analyses via electron microscopy, and presynaptic Ca2+-specific optical probes. Our findings revealed that female neurons exhibited a higher number of synaptic vesicles at presynaptic terminals compared to male neurons. However, no significant differences were observed in presynaptic protein expression, presynaptic terminal ultrastructure, synaptic vesicle exocytosis and endocytosis, or presynaptic Ca2+ alterations between male and female neurons.
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Affiliation(s)
- Sung Rae Kim
- College of Pharmacy, Chung-Ang University, Seoul 06974, Republic of Korea; Brain Research Core Facilities of Korea Brain Research Institute (KBRI), Daegu 41068, Republic of Korea.
| | - Yunkyung Eom
- College of Pharmacy, Chung-Ang University, Seoul 06974, Republic of Korea.
| | - Sung Hoon Lee
- College of Pharmacy, Chung-Ang University, Seoul 06974, Republic of Korea.
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4
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Sun SY, Li XW, Cao R, Zhao Y, Sheng N, Tang AH. Correlative Assembly of Subsynaptic Nanoscale Organizations During Development. Front Synaptic Neurosci 2022; 14:748184. [PMID: 35685244 PMCID: PMC9171000 DOI: 10.3389/fnsyn.2022.748184] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 03/11/2022] [Indexed: 11/17/2022] Open
Abstract
Nanoscale organization of presynaptic proteins determines the sites of transmitter release, and its alignment with assemblies of postsynaptic receptors through nanocolumns is suggested to optimize the efficiency of synaptic transmission. However, it remains unknown how these nano-organizations are formed during development. In this study, we used super-resolution stochastic optical reconstruction microscopy (STORM) imaging technique to systematically analyze the evolvement of subsynaptic organization of three key synaptic proteins, namely, RIM1/2, GluA1, and PSD-95, during synapse maturation in cultured hippocampal neurons. We found that volumes of synaptic clusters and their subsynaptic heterogeneity increase as synapses get matured. Synapse sizes of presynaptic and postsynaptic compartments correlated well at all stages, while only more mature synapses demonstrated a significant correlation between presynaptic and postsynaptic nano-organizations. After a long incubation with an inhibitor of action potentials or AMPA receptors, both presynaptic and postsynaptic compartments showed increased synaptic cluster volume and subsynaptic heterogeneity; however, the trans-synaptic alignment was intact. Together, our results characterize the evolvement of subsynaptic protein architectures during development and demonstrate that the nanocolumn is organized more likely by an intrinsic mechanism and independent of synaptic activities.
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Affiliation(s)
- Shi-Yan Sun
- Chinese Academy of Sciences (CAS) Key Laboratory of Brain Function and Disease, Ministry of Education Key Laboratory for Membrane-less Organelles and Cellular Dynamics, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
- Institute of Artificial Intelligence, Hefei Comprehensive National Science Center, Hefei, China
| | - Xiao-Wei Li
- Chinese Academy of Sciences (CAS) Key Laboratory of Brain Function and Disease, Ministry of Education Key Laboratory for Membrane-less Organelles and Cellular Dynamics, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
| | - Ran Cao
- Chinese Academy of Sciences (CAS) Key Laboratory of Brain Function and Disease, Ministry of Education Key Laboratory for Membrane-less Organelles and Cellular Dynamics, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
| | - Yang Zhao
- Chinese Academy of Sciences (CAS) Key Laboratory of Brain Function and Disease, Ministry of Education Key Laboratory for Membrane-less Organelles and Cellular Dynamics, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
- State Key Laboratory of Genetic Resources and Evolution in Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China
| | - Nengyin Sheng
- State Key Laboratory of Genetic Resources and Evolution in Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China
| | - Ai-Hui Tang
- Chinese Academy of Sciences (CAS) Key Laboratory of Brain Function and Disease, Ministry of Education Key Laboratory for Membrane-less Organelles and Cellular Dynamics, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
- Institute of Artificial Intelligence, Hefei Comprehensive National Science Center, Hefei, China
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5
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Heterosynaptic cross-talk of pre- and postsynaptic strengths along segments of dendrites. Cell Rep 2021; 34:108693. [PMID: 33503435 DOI: 10.1016/j.celrep.2021.108693] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 08/13/2020] [Accepted: 01/05/2021] [Indexed: 11/20/2022] Open
Abstract
Dendrites are crucial for integrating incoming synaptic information. Individual dendritic branches are thought to constitute a signal processing unit, yet how neighboring synapses shape the boundaries of functional dendritic units is not well understood. Here, we address the cellular basis underlying the organization of the strengths of neighboring Schaffer collateral-CA1 synapses by optical quantal analysis and spine size measurements. Inducing potentiation at clusters of spines produces NMDA-receptor-dependent heterosynaptic plasticity. The direction of postsynaptic strength change shows distance dependency to the stimulated synapses where proximal synapses predominantly depress, whereas distal synapses potentiate; potentiation and depression are regulated by CaMKII and calcineurin, respectively. In contrast, heterosynaptic presynaptic plasticity is confined to weakening of presynaptic strength of nearby synapses, which requires CaMKII and the retrograde messenger nitric oxide. Our findings highlight the parallel engagement of multiple signaling pathways, each with characteristic spatial dynamics in shaping the local pattern of synaptic strengths.
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6
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Taylor HBC, Tong R, Jeans AF, Emptage NJ. A Novel Optical Quantal Analysis of Miniature Events Reveals Enhanced Frequency Following Amyloid β Exposure. Front Cell Neurosci 2020; 14:564081. [PMID: 33240043 PMCID: PMC7669988 DOI: 10.3389/fncel.2020.564081] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 10/01/2020] [Indexed: 11/17/2022] Open
Abstract
Non-evoked miniature release of neurotransmitters is increasingly recognized as playing an important role in neural function and is implicated in synaptic plasticity, metaplasticity, and homeostasis. Spontaneous miniature release events (minis) are usually measured electrophysiologically by recording the miniature postsynaptic currents (mEPSCs) that they evoke. However, this indirect technique can be confounded by changes within the postsynaptic neuron. Here, using the fluorescent probe SynaptopHluorin 2×, we have developed an optical method for the measurement of minis that enables direct assessment of release events. We use the technique to reveal that the frequency of minis following incubation of hippocampal neurons with Amyloid β oligomers (Aβo) is increased. Electrophysiological mEPSC recordings obtained under the same conditions report a decrease in frequency, with the discrepancy likely due to Aβo-induced changes in quantal size. Optical quantal analysis of minis may therefore have a role in the study of minis in both normal physiology and disease, as it can circumvent potential confounds caused by postsynaptic changes.
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Affiliation(s)
- Henry B. C. Taylor
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford, United Kingdom
| | - Rudi Tong
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford, United Kingdom
- Montreal Neurological Institute and Hospital, Montreal, QC, Canada
| | - Alexander F. Jeans
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford, United Kingdom
| | - Nigel J. Emptage
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford, United Kingdom
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7
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Sanderson TM, Georgiou J, Collingridge GL. Illuminating Relationships Between the Pre- and Post-synapse. Front Neural Circuits 2020; 14:9. [PMID: 32308573 PMCID: PMC7146027 DOI: 10.3389/fncir.2020.00009] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 03/06/2020] [Indexed: 12/11/2022] Open
Abstract
Excitatory synapses in the mammalian cortex are highly diverse, both in terms of their structure and function. However, relationships between synaptic features indicate they are highly coordinated entities. Imaging techniques, that enable physiology at the resolution of individual synapses to be investigated, have allowed the presynaptic activity level of the synapse to be related to postsynaptic function. This approach has revealed that neuronal activity induces the pre- and post-synapse to be functionally correlated and that subsets of synapses are more susceptible to certain forms of synaptic plasticity. As presynaptic function is often examined in isolation from postsynaptic properties, the effect it has on the post-synapse is not fully understood. However, since postsynaptic receptors at excitatory synapses respond to release of glutamate, it follows that they may be differentially regulated depending on the frequency of its release. Therefore, examining postsynaptic properties in the context of presynaptic function may be a useful way to approach a broad range of questions on synaptic physiology. In this review, we focus on how optophysiology tools have been utilized to study relationships between the pre- and the post-synapse. Multiple imaging techniques have revealed correlations in synaptic properties from the submicron to the dendritic level. Optical tools together with advanced imaging techniques are ideally suited to illuminate this area further, due to the spatial resolution and control they allow.
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Affiliation(s)
| | - John Georgiou
- Lunenfeld-Tanenbaum Research Institute, Toronto, ON, Canada
| | - Graham L Collingridge
- Lunenfeld-Tanenbaum Research Institute, Toronto, ON, Canada.,Tanz Centre for Research in Neurodegenerative Diseases, Department of Physiology, University of Toronto, Toronto, ON, Canada.,Glutamate Research Group, School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom
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8
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Letellier M, Levet F, Thoumine O, Goda Y. Differential role of pre- and postsynaptic neurons in the activity-dependent control of synaptic strengths across dendrites. PLoS Biol 2019; 17:e2006223. [PMID: 31166943 PMCID: PMC6576792 DOI: 10.1371/journal.pbio.2006223] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 06/17/2019] [Accepted: 05/17/2019] [Indexed: 01/07/2023] Open
Abstract
Neurons receive a large number of active synaptic inputs from their many presynaptic partners across their dendritic tree. However, little is known about how the strengths of individual synapses are controlled in balance with other synapses to effectively encode information while maintaining network homeostasis. This is in part due to the difficulty in assessing the activity of individual synapses with identified afferent and efferent connections for a synapse population in the brain. Here, to gain insights into the basic cellular rules that drive the activity-dependent spatial distribution of pre- and postsynaptic strengths across incoming axons and dendrites, we combine patch-clamp recordings with live-cell imaging of hippocampal pyramidal neurons in dissociated cultures and organotypic slices. Under basal conditions, both pre- and postsynaptic strengths cluster on single dendritic branches according to the identity of the presynaptic neurons, thus highlighting the ability of single dendritic branches to exhibit input specificity. Stimulating a single presynaptic neuron induces input-specific and dendritic branchwise spatial clustering of presynaptic strengths, which accompanies a widespread multiplicative scaling of postsynaptic strengths in dissociated cultures and heterosynaptic plasticity at distant synapses in organotypic slices. Our study provides evidence for a potential homeostatic mechanism by which the rapid changes in global or distant postsynaptic strengths compensate for input-specific presynaptic plasticity.
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Affiliation(s)
- Mathieu Letellier
- RIKEN Brain Science Institute, Wako, Saitama, Japan
- Interdisciplinary Institute for Neuroscience, University of Bordeaux, Bordeaux, France
- Interdisciplinary Institute for Neuroscience, Centre National de la Recherche Scientifique (CNRS) UMR 5297, Bordeaux, France
- * E-mail: (ML); (YG)
| | - Florian Levet
- Interdisciplinary Institute for Neuroscience, University of Bordeaux, Bordeaux, France
- Interdisciplinary Institute for Neuroscience, Centre National de la Recherche Scientifique (CNRS) UMR 5297, Bordeaux, France
- Bordeaux Imaging Center, University of Bordeaux, Bordeaux, France
- Bordeaux Imaging Center, CNRS UMS 3420, Bordeaux, France
- Bordeaux Imaging Center, INSERM US04, Bordeaux, France
| | - Olivier Thoumine
- Interdisciplinary Institute for Neuroscience, University of Bordeaux, Bordeaux, France
- Interdisciplinary Institute for Neuroscience, Centre National de la Recherche Scientifique (CNRS) UMR 5297, Bordeaux, France
| | - Yukiko Goda
- RIKEN Center for Brain Science, Wako, Saitama, Japan
- * E-mail: (ML); (YG)
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9
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Berberian N, Ross M, Chartier S. Discrimination of Motion Direction in a Robot Using a Phenomenological Model of Synaptic Plasticity. COMPUTATIONAL INTELLIGENCE AND NEUROSCIENCE 2019; 2019:6989128. [PMID: 31191633 PMCID: PMC6525956 DOI: 10.1155/2019/6989128] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Revised: 02/14/2019] [Accepted: 03/19/2019] [Indexed: 11/17/2022]
Abstract
Recognizing and tracking the direction of moving stimuli is crucial to the control of much animal behaviour. In this study, we examine whether a bio-inspired model of synaptic plasticity implemented in a robotic agent may allow the discrimination of motion direction of real-world stimuli. Starting with a well-established model of short-term synaptic plasticity (STP), we develop a microcircuit motif of spiking neurons capable of exhibiting preferential and nonpreferential responses to changes in the direction of an orientation stimulus in motion. While the robotic agent processes sensory inputs, the STP mechanism introduces direction-dependent changes in the synaptic connections of the microcircuit, resulting in a population of units that exhibit a typical cortical response property observed in primary visual cortex (V1), namely, direction selectivity. Visually evoked responses from the model are then compared to those observed in multielectrode recordings from V1 in anesthetized macaque monkeys, while sinusoidal gratings are displayed on a screen. Overall, the model highlights the role of STP as a complementary mechanism in explaining the direction selectivity and applies these insights in a physical robot as a method for validating important response characteristics observed in experimental data from V1, namely, direction selectivity.
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Affiliation(s)
- Nareg Berberian
- Laboratory for Computational Neurodynamics and Cognition, School of Psychology, University of Ottawa, Ottawa, ON, Canada K1N 6N5
| | - Matt Ross
- Laboratory for Computational Neurodynamics and Cognition, School of Psychology, University of Ottawa, Ottawa, ON, Canada K1N 6N5
| | - Sylvain Chartier
- Laboratory for Computational Neurodynamics and Cognition, School of Psychology, University of Ottawa, Ottawa, ON, Canada K1N 6N5
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10
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Goel P, Dufour Bergeron D, Böhme MA, Nunnelly L, Lehmann M, Buser C, Walter AM, Sigrist SJ, Dickman D. Homeostatic scaling of active zone scaffolds maintains global synaptic strength. J Cell Biol 2019; 218:1706-1724. [PMID: 30914419 PMCID: PMC6504899 DOI: 10.1083/jcb.201807165] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 12/14/2018] [Accepted: 03/06/2019] [Indexed: 12/23/2022] Open
Abstract
Synaptic terminals grow and retract throughout life, yet synaptic strength is maintained within stable physiological ranges. To study this process, we investigated Drosophila endophilin (endo) mutants. Although active zone (AZ) number is doubled in endo mutants, a compensatory reduction in their size homeostatically adjusts global neurotransmitter output to maintain synaptic strength. We find an inverse adaptation in rab3 mutants. Additional analyses using confocal, STED, and electron microscopy reveal a stoichiometric tuning of AZ scaffolds and nanoarchitecture. Axonal transport of synaptic cargo via the lysosomal kinesin adapter Arl8 regulates AZ abundance to modulate global synaptic output and sustain the homeostatic potentiation of neurotransmission. Finally, we find that this AZ scaling can interface with two independent homeostats, depression and potentiation, to remodel AZ structure and function, demonstrating a robust balancing of separate homeostatic adaptations. Thus, AZs are pliable substrates with elastic and modular nanostructures that can be dynamically sculpted to stabilize and tune both local and global synaptic strength.
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Affiliation(s)
- Pragya Goel
- Department of Neurobiology, University of Southern California, Los Angeles, CA
| | | | - Mathias A Böhme
- Neurocure Cluster of Excellence, Charité Universitätsmedizin, Berlin, Germany
| | - Luke Nunnelly
- Department of Neurobiology, University of Southern California, Los Angeles, CA
| | - Martin Lehmann
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | | | - Alexander M Walter
- Neurocure Cluster of Excellence, Charité Universitätsmedizin, Berlin, Germany
| | | | - Dion Dickman
- Department of Neurobiology, University of Southern California, Los Angeles, CA
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11
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Padamsey Z, Tong R, Emptage N. Optical Quantal Analysis Using Ca 2+ Indicators: A Robust Method for Assessing Transmitter Release Probability at Excitatory Synapses by Imaging Single Glutamate Release Events. Front Synaptic Neurosci 2019; 11:5. [PMID: 30886576 PMCID: PMC6409341 DOI: 10.3389/fnsyn.2019.00005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 02/14/2019] [Indexed: 11/13/2022] Open
Abstract
Despite evidence that presynaptic efficacy and plasticity influence circuit function and behavior in vivo, studies of presynaptic function remain challenging owing to the difficulty of assessing transmitter release in intact tissue. Electrophysiological analyses of transmitter release are indirect and cannot readily resolve basic presynaptic parameters, most notably transmitter release probability (p r), at single synapses. These issues can be circumvented by optical quantal analysis, which uses the all-or-none optical detection of transmitter release in order to calculate p r. Over the past two decades, we and others have successfully demonstrated that Ca2+ indicators can be strategically implemented to perform optical quantal analysis at single glutamatergic synapses in ex vivo and in vitro preparations. We have found that high affinity Ca2+ indicators can reliably detect spine Ca2+ influx generated by single quanta of glutamate, thereby enabling precise calculation of pr at single synapses. Importantly, we have shown this method to be robust to changes in postsynaptic efficacy, and to be sensitive to activity-dependent presynaptic changes at central synapses following the induction of long-term potentiation (LTP) and long-term depression (LTD). In this report, we describe how to use Ca2+-sensitive dyes to perform optical quantal analysis at single synapses in hippocampal slice preparations. The general technique we describe here can be applied to other glutamatergic synapses and can be used with other reporters of glutamate release, including recently improved genetically encoded Ca2+ and glutamate sensors. With ongoing developments in imaging techniques and genetically encoded probes, optical quantal analysis is a promising strategy for assessing presynaptic function and plasticity in vivo.
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Affiliation(s)
- Zahid Padamsey
- Center for Discovery Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Rudi Tong
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Nigel Emptage
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
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12
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Presynaptic Diversity Revealed by Ca 2+-Permeable AMPA Receptors at the Calyx of Held Synapse. J Neurosci 2019; 39:2981-2994. [PMID: 30679394 DOI: 10.1523/jneurosci.2565-18.2019] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 12/14/2018] [Accepted: 01/03/2019] [Indexed: 02/06/2023] Open
Abstract
GluA2-lacking Ca2+-permeable AMPARs (CP-AMPARs) play integral roles in synaptic plasticity and can mediate excitotoxic cellular signaling at glutamatergic synapses. However, the developmental profile of functional CP-AMPARs at the auditory brainstem remains poorly understood. Through a combination of electrophysiological and live-cell Ca2+ imaging from mice of either sex, we show that the synaptic release of glutamate from the calyx of Held nerve terminal activates CP-AMPARs in the principal cells of the medial nucleus of the trapezoid body in the brainstem. This leads to significant Ca2+ influx through these receptors before the onset of hearing at postnatal day 12 (P12). Using a selective open channel blocker of CP-AMPARs, IEM-1460, we estimate that ∼80% of the AMPAR population are permeable to Ca2+ at immature P4-P5 synapses. However, after the onset of hearing, Ca2+ influx through these receptors was greatly reduced. We estimate that CP-AMPARs comprise approximately 40% and 33% of the AMPAR population at P18-P22 and P30-P34, respectively. By quantifying the rate of EPSC block by IEM-1460, we found an increased heterogeneity in glutamate release probability for adult-like calyces (P30-P34). Using tetraethylammonium (TEA), a presynaptic potassium channel blocker, we show that the apparent reduction of CP-AMPARs in more mature synapses is not a consequence of presynaptic action potential (AP) speeding. Finally, through postsynaptic AP recordings, we show that inhibition of CP-AMPARs reduces spike fidelity in juvenile synapses, but not in more mature synapses. We conclude that the expression of functional CP-AMPARs declines over early postnatal development in the calyx of Held synapse.SIGNIFICANCE STATEMENT The calyx of Held synapse is pivotal to the circuitry that computes sound localization. Postsynaptic Ca2+ influx via AMPARs may be critical for signaling the maturation of this brainstem synapse. The GluA4 subunit may dominate the AMPAR complex at mature synapses because of its fast gating kinetics and large unitary conductance. The expectation is that AMPARs dominated by GluA4 subunits should be highly Ca2+ permeable. However, we find that Ca2+-permeable AMPAR expression declines during postnatal development. Using the rate of EPSC block by IEM-1460, an open channel blocker of Ca2+-permeable AMPARs, we propose a novel method to determine glutamate release probability and uncover an increased heterogeneity in release probability for more mature calyces of Held nerve terminals.
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Sanderson TM, Bradley CA, Georgiou J, Hong YH, Ng AN, Lee Y, Kim HD, Kim D, Amici M, Son GH, Zhuo M, Kim K, Kaang BK, Kim SJ, Collingridge GL. The Probability of Neurotransmitter Release Governs AMPA Receptor Trafficking via Activity-Dependent Regulation of mGluR1 Surface Expression. Cell Rep 2018; 25:3631-3646.e3. [PMID: 30590038 PMCID: PMC6315206 DOI: 10.1016/j.celrep.2018.12.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 09/28/2018] [Accepted: 12/03/2018] [Indexed: 12/14/2022] Open
Abstract
A major mechanism contributing to synaptic plasticity involves alterations in the number of AMPA receptors (AMPARs) expressed at synapses. Hippocampal CA1 synapses, where this process has been most extensively studied, are highly heterogeneous with respect to their probability of neurotransmitter release, P(r). It is unknown whether there is any relationship between the extent of plasticity-related AMPAR trafficking and the initial P(r) of a synapse. To address this question, we induced metabotropic glutamate receptor (mGluR) dependent long-term depression (mGluR-LTD) and assessed AMPAR trafficking and P(r) at individual synapses, using SEP-GluA2 and FM4-64, respectively. We found that either pharmacological or synaptic activation of mGluR1 reduced synaptic SEP-GluA2 in a manner that depends upon P(r); this process involved an activity-dependent reduction in surface mGluR1 that selectively protects high-P(r) synapses from synaptic weakening. Consequently, the extent of postsynaptic plasticity can be pre-tuned by presynaptic activity.
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Affiliation(s)
- Thomas M Sanderson
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul 151-746, Korea; Neuroscience Research Institute, Seoul National University College of Medicine, 28 Yeongeon-dong, Jongno-gu, Seoul 110-799, Korea; School of Physiology, Pharmacology & Neuroscience, University of Bristol, Dorothy Hodgkin Building, Whitson Street, Bristol BS1 3NY, UK; Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada
| | - Clarrisa A Bradley
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul 151-746, Korea; Neuroscience & Mental Health Program, The Hospital for Sick Children, Toronto, ON, Canada
| | - John Georgiou
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada
| | - Yun Hwa Hong
- Neuroscience Research Institute, Seoul National University College of Medicine, 28 Yeongeon-dong, Jongno-gu, Seoul 110-799, Korea; Department of Physiology, Seoul National University College of Medicine, 28, Yeongeon-dong, Jongno-gu, Seoul 110-799, Korea
| | - Ai Na Ng
- School of Physiology, Pharmacology & Neuroscience, University of Bristol, Dorothy Hodgkin Building, Whitson Street, Bristol BS1 3NY, UK
| | - Yeseul Lee
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul 151-746, Korea; School of Physiology, Pharmacology & Neuroscience, University of Bristol, Dorothy Hodgkin Building, Whitson Street, Bristol BS1 3NY, UK
| | - Hee-Dae Kim
- Department of Brain and Cognitive Sciences, DGIST, and Korea Brain Institute (KBRI), Daegu, 41068, Korea
| | - Doyeon Kim
- Department of Brain and Cognitive Sciences, DGIST, and Korea Brain Institute (KBRI), Daegu, 41068, Korea
| | - Mascia Amici
- School of Physiology, Pharmacology & Neuroscience, University of Bristol, Dorothy Hodgkin Building, Whitson Street, Bristol BS1 3NY, UK
| | - Gi Hoon Son
- Department of Biomedical Sciences, Korea University College of Medicine, Seoul 136-705, Seoul, Korea
| | - Min Zhuo
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul 151-746, Korea; Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada; Department of Biological Sciences, College of Natural Sciences, Seoul National University, Building 504, Room 202, 599 Gwanangno, Gwanak-gu 151-747, Seoul, Korea; Center for Neuron and Disease, Frontier Institutes of Science and Technology, Xi'an Jiaotong University, Xi'an, 710049, China
| | - Kyungjin Kim
- Department of Brain and Cognitive Sciences, DGIST, and Korea Brain Institute (KBRI), Daegu, 41068, Korea
| | - Bong-Kiun Kaang
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul 151-746, Korea; Department of Biological Sciences, College of Natural Sciences, Seoul National University, Building 504, Room 202, 599 Gwanangno, Gwanak-gu 151-747, Seoul, Korea; Center for Neuron and Disease, Frontier Institutes of Science and Technology, Xi'an Jiaotong University, Xi'an, 710049, China
| | - Sang Jeong Kim
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul 151-746, Korea; Neuroscience Research Institute, Seoul National University College of Medicine, 28 Yeongeon-dong, Jongno-gu, Seoul 110-799, Korea; Department of Physiology, Seoul National University College of Medicine, 28, Yeongeon-dong, Jongno-gu, Seoul 110-799, Korea.
| | - Graham L Collingridge
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul 151-746, Korea; School of Physiology, Pharmacology & Neuroscience, University of Bristol, Dorothy Hodgkin Building, Whitson Street, Bristol BS1 3NY, UK; Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada; Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada.
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14
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Jeans AF, van Heusden FC, Al-Mubarak B, Padamsey Z, Emptage NJ. Homeostatic Presynaptic Plasticity Is Specifically Regulated by P/Q-type Ca 2+ Channels at Mammalian Hippocampal Synapses. Cell Rep 2018; 21:341-350. [PMID: 29020622 PMCID: PMC5643522 DOI: 10.1016/j.celrep.2017.09.061] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 08/11/2017] [Accepted: 09/19/2017] [Indexed: 11/17/2022] Open
Abstract
Voltage-dependent Ca2+ channels (VGCC) represent the principal source of Ca2+ ions driving evoked neurotransmitter release at presynaptic boutons. In mammals, presynaptic Ca2+ influx is mediated mainly via P/Q-type and N-type VGCC, which differ in their properties. Changes in their relative contributions tune neurotransmission both during development and in Hebbian plasticity. However, whether this represents a functional motif also present in other forms of activity-dependent regulation is unknown. Here, we study the role of VGCC in homeostatic plasticity (HSP) in mammalian hippocampal neurons using optical techniques. We find that changes in evoked Ca2+ currents specifically through P/Q-type, but not N-type, VGCC mediate bidirectional homeostatic regulation of both neurotransmitter release efficacy and the size of the major synaptic vesicle pools. Selective dependence of HSP on P/Q-type VGCC in mammalian terminals has important implications for phenotypes associated with P/Q-type channelopathies, including migraine and epilepsy. P/Q-type VGCC regulate homeostatic synaptic plasticity (HSP) in mammals Changes in synaptic vesicle pool sizes during HSP are also mediated via P/Q-type VGCC Expression of HSP is independent of N-type VGCC regulation P/Q-type regulation of HSP may explain phenotypes of P/Q-type channelopathies
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Affiliation(s)
- Alexander F Jeans
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK.
| | - Fran C van Heusden
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
| | - Bashayer Al-Mubarak
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK; Department of Genetics, King Faisal Specialist Hospital and Research Center, PO Box 3354, Riyadh 11211, Saudi Arabia
| | - Zahid Padamsey
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
| | - Nigel J Emptage
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK.
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15
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Axonal Type III Nrg1 Controls Glutamate Synapse Formation and GluA2 Trafficking in Hippocampal-Accumbens Connections. eNeuro 2017; 4:eN-NWR-0232-16. [PMID: 28275713 PMCID: PMC5329619 DOI: 10.1523/eneuro.0232-16.2017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Revised: 01/23/2017] [Accepted: 02/06/2017] [Indexed: 11/21/2022] Open
Abstract
Altered neuregulin 1 (Nrg1)/ErbB signaling and glutamatergic hypofunction have been implicated in the pathophysiology of schizophrenia. Here, we employed gene chimeric ventral hippocampus (vHipp)-nucleus accumbens (nAcc) coculture from mouse, electrophysiology, immunocytochemistry, FM1-43 vesicle fusion, and electron microscopy techniques to examine the pre- and postsynaptic mechanisms of genetic deficits in Nrg1/ErbB signaling-induced glutamatergic dysfunctions. Reduced presynaptic type III Nrg1 expression along vHipp axons decreases the number of glutamate synapses and impairs GluA2 trafficking in the postsynaptic nAcc neurons, resulting in decreased frequency and amplitude of miniature EPSCs (mEPSCs). Reduced expression of axonal type III Nrg1 along vHipp projections also decreases functional synaptic vesicle (SV) clustering and vesicular trafficking to presynaptic vHipp axonal terminals. These findings suggest that Nrg1/ErbB signaling modulate glutamatergic transmission via both pre- and postsynaptic mechanisms.
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16
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Dvorkin R, Ziv NE. Relative Contributions of Specific Activity Histories and Spontaneous Processes to Size Remodeling of Glutamatergic Synapses. PLoS Biol 2016; 14:e1002572. [PMID: 27776122 PMCID: PMC5077109 DOI: 10.1371/journal.pbio.1002572] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2016] [Accepted: 09/27/2016] [Indexed: 11/18/2022] Open
Abstract
The idea that synaptic properties are defined by specific pre- and postsynaptic activity histories is one of the oldest and most influential tenets of contemporary neuroscience. Recent studies also indicate, however, that synaptic properties often change spontaneously, even in the absence of specific activity patterns or any activity whatsoever. What, then, are the relative contributions of activity history-dependent and activity history-independent processes to changes synapses undergo? To compare the relative contributions of these processes, we imaged, in spontaneously active networks of cortical neurons, glutamatergic synapses formed between the same axons and neurons or dendrites under the assumption that their similar activity histories should result in similar size changes over timescales of days. The size covariance of such commonly innervated (CI) synapses was then compared to that of synapses formed by different axons (non-CI synapses) that differed in their activity histories. We found that the size covariance of CI synapses was greater than that of non-CI synapses; yet overall size covariance of CI synapses was rather modest. Moreover, momentary and time-averaged sizes of CI synapses correlated rather poorly, in perfect agreement with published electron microscopy-based measurements of mouse cortex synapses. A conservative estimate suggested that ~40% of the observed size remodeling was attributable to specific activity histories, whereas ~10% and ~50% were attributable to cell-wide and spontaneous, synapse-autonomous processes, respectively. These findings demonstrate that histories of naturally occurring activity patterns can direct glutamatergic synapse remodeling but also suggest that the contributions of spontaneous, possibly stochastic, processes are at least as great.
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Affiliation(s)
- Roman Dvorkin
- Technion Faculty of Medicine, Network Biology Research Laboratories, Lorry Lokey Center for Life Sciences and Engineering, Technion, Haifa, Israel
| | - Noam E Ziv
- Technion Faculty of Medicine, Network Biology Research Laboratories, Lorry Lokey Center for Life Sciences and Engineering, Technion, Haifa, Israel.,Rappaport Family Institute for Research in the Medical Sciences, Haifa, Israel
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17
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Wefelmeyer W, Puhl CJ, Burrone J. Homeostatic Plasticity of Subcellular Neuronal Structures: From Inputs to Outputs. Trends Neurosci 2016; 39:656-667. [PMID: 27637565 PMCID: PMC5236059 DOI: 10.1016/j.tins.2016.08.004] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 08/18/2016] [Accepted: 08/19/2016] [Indexed: 01/02/2023]
Abstract
Neurons in the brain are highly plastic, allowing an organism to learn and adapt to its environment. However, this ongoing plasticity is also inherently unstable, potentially leading to aberrant levels of circuit activity. Homeostatic forms of plasticity are thought to provide a means of controlling neuronal activity by avoiding extremes and allowing network stability. Recent work has shown that many of these homeostatic modifications change the structure of subcellular neuronal compartments, ranging from changes to synaptic inputs at both excitatory and inhibitory compartments to modulation of neuronal output through changes at the axon initial segment (AIS) and presynaptic terminals. Here we review these different forms of structural plasticity in neurons and the effects they may have on network function.
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Affiliation(s)
- Winnie Wefelmeyer
- Centre for Developmental Neurobiology, King's College London, New Hunt's House, Guy's Hospital Campus, London, SE1 1UL, UK.
| | - Christopher J Puhl
- Centre for Developmental Neurobiology, King's College London, New Hunt's House, Guy's Hospital Campus, London, SE1 1UL, UK
| | - Juan Burrone
- Centre for Developmental Neurobiology, King's College London, New Hunt's House, Guy's Hospital Campus, London, SE1 1UL, UK.
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18
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Hackett TA, Clause AR, Takahata T, Hackett NJ, Polley DB. Differential maturation of vesicular glutamate and GABA transporter expression in the mouse auditory forebrain during the first weeks of hearing. Brain Struct Funct 2015; 221:2619-73. [PMID: 26159773 DOI: 10.1007/s00429-015-1062-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 05/07/2015] [Indexed: 02/04/2023]
Abstract
Vesicular transporter proteins are an essential component of the presynaptic machinery that regulates neurotransmitter storage and release. They also provide a key point of control for homeostatic signaling pathways that maintain balanced excitation and inhibition following changes in activity levels, including the onset of sensory experience. To advance understanding of their roles in the developing auditory forebrain, we tracked the expression of the vesicular transporters of glutamate (VGluT1, VGluT2) and GABA (VGAT) in primary auditory cortex (A1) and medial geniculate body (MGB) of developing mice (P7, P11, P14, P21, adult) before and after ear canal opening (~P11-P13). RNA sequencing, in situ hybridization, and immunohistochemistry were combined to track changes in transporter expression and document regional patterns of transcript and protein localization. Overall, vesicular transporter expression changed the most between P7 and P21. The expression patterns and maturational trajectories of each marker varied by brain region, cortical layer, and MGB subdivision. VGluT1 expression was highest in A1, moderate in MGB, and increased with age in both regions. VGluT2 mRNA levels were low in A1 at all ages, but high in MGB, where adult levels were reached by P14. VGluT2 immunoreactivity was prominent in both regions. VGluT1 (+) and VGluT2 (+) transcripts were co-expressed in MGB and A1 somata, but co-localization of immunoreactive puncta was not detected. In A1, VGAT mRNA levels were relatively stable from P7 to adult, while immunoreactivity increased steadily. VGAT (+) transcripts were rare in MGB neurons, whereas VGAT immunoreactivity was robust at all ages. Morphological changes in immunoreactive puncta were found in two regions after ear canal opening. In the ventral MGB, a decrease in VGluT2 puncta density was accompanied by an increase in puncta size. In A1, perisomatic VGAT and VGluT1 terminals became prominent around the neuronal somata. Overall, the observed changes in gene and protein expression, regional architecture, and morphology relate to-and to some extent may enable-the emergence of mature sound-evoked activity patterns. In that regard, the findings of this study expand our understanding of the presynaptic mechanisms that regulate critical period formation associated with experience-dependent refinement of sound processing in auditory forebrain circuits.
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Affiliation(s)
- Troy A Hackett
- Department of Hearing and Speech Sciences, Vanderbilt University School of Medicine, 465 21st Avenue South, MRB-3 Suite 7110, Nashville, TN, 37232, USA.
| | - Amanda R Clause
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, Department of Otology and Laryngology, Harvard Medical School, Boston, MA, USA
| | - Toru Takahata
- Department of Hearing and Speech Sciences, Vanderbilt University School of Medicine, 465 21st Avenue South, MRB-3 Suite 7110, Nashville, TN, 37232, USA
| | | | - Daniel B Polley
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, Department of Otology and Laryngology, Harvard Medical School, Boston, MA, USA
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19
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Shinoda Y, Ahmed S, Ramachandran B, Bharat V, Brockelt D, Altas B, Dean C. BDNF enhances spontaneous and activity-dependent neurotransmitter release at excitatory terminals but not at inhibitory terminals in hippocampal neurons. Front Synaptic Neurosci 2014; 6:27. [PMID: 25426063 PMCID: PMC4226143 DOI: 10.3389/fnsyn.2014.00027] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2014] [Accepted: 10/21/2014] [Indexed: 11/30/2022] Open
Abstract
Brain-derived neurotrophic factor (BDNF) is widely reported to enhance synaptic vesicle (SV) exocytosis and neurotransmitter release. But it is still unclear whether BDNF enhances SV recycling at excitatory terminals only, or at both excitatory and inhibitory terminals. In the present study, in a direct comparison using cultured rat hippocampal neurons, we demonstrate that BDNF enhances both spontaneous and activity-dependent neurotransmitter release from excitatory terminals, but not from inhibitory terminals. BDNF treatment for 5 min or 48 h increased both spontaneous and activity-induced anti-synaptotagmin1 (SYT1) antibody uptake at excitatory terminals marked with vGluT1. Conversely, BDNF treatment did not enhance spontaneous or activity-induced uptake of anti-SYT1 antibodies in inhibitory terminals marked with vGAT. Time-lapse imaging of FM1-43 dye destaining in excitatory and inhibitory terminals visualized by post-hoc immunostaining of vGluT1 and vGAT also showed the same result: The rate of spontaneous and activity-induced destaining was increased by BDNF at excitatory synapses, but not at inhibitory synapses. These data demonstrate that BDNF enhances SV exocytosis in excitatory but not inhibitory terminals. Moreover, BDNF enhanced evoked SV exocytosis, even if vesicles were loaded under spontaneous vesicle recycling conditions. Thus, BDNF enhances both spontaneous and activity-dependent neurotransmitter release on both short and long time-scales, by the same mechanism.
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Affiliation(s)
- Yo Shinoda
- Trans-synaptic Signaling Group, European Neuroscience Institute Goettingen, Germany ; Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science Chiba, Japan
| | - Saheeb Ahmed
- Trans-synaptic Signaling Group, European Neuroscience Institute Goettingen, Germany
| | - Binu Ramachandran
- Trans-synaptic Signaling Group, European Neuroscience Institute Goettingen, Germany
| | - Vinita Bharat
- Trans-synaptic Signaling Group, European Neuroscience Institute Goettingen, Germany
| | - David Brockelt
- Trans-synaptic Signaling Group, European Neuroscience Institute Goettingen, Germany
| | - Bekir Altas
- Trans-synaptic Signaling Group, European Neuroscience Institute Goettingen, Germany
| | - Camin Dean
- Trans-synaptic Signaling Group, European Neuroscience Institute Goettingen, Germany
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20
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Xu W, Tan L, Yu JT. The Role of PICALM in Alzheimer's Disease. Mol Neurobiol 2014; 52:399-413. [PMID: 25186232 DOI: 10.1007/s12035-014-8878-3] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 08/25/2014] [Indexed: 01/18/2023]
Abstract
Alzheimer's disease (AD) is a highly heritable disease (with heritability up to 76%) with a complex genetic profile of susceptibility, among which large genome-wide association studies (GWASs) pointed to the phosphatidylinositol-binding clathrin assembly protein (PICALM) gene as a susceptibility locus for late-onset Alzheimer's disease (LOAD) incidence. Here, we summarize the known functions of PICALM and discuss its genetic polymorphisms and their potential physiological effects associated with LOAD. Compelling data indicated that PICALM affects AD risk primarily by modulating production, transportation, and clearance of β-amyloid (Aβ) peptide, but other Aβ-independent pathways are discussed, including tauopathy, synaptic dysfunction, disorganized lipid metabolism, immune disorder, and disrupted iron homeostasis. Finally, given the potential involvement of PICALM in facilitating AD occurrence in multiple ways, it might be possible that targeting PICALM might provide promising and novel avenues for AD therapy.
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Affiliation(s)
- Wei Xu
- Department of Neurology, Qingdao Municipal Hospital, School of Medicine, Qingdao University, Qingdao, China
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21
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Vitureira N, Goda Y. Cell biology in neuroscience: the interplay between Hebbian and homeostatic synaptic plasticity. ACTA ACUST UNITED AC 2013; 203:175-86. [PMID: 24165934 PMCID: PMC3812972 DOI: 10.1083/jcb.201306030] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Synaptic plasticity, a change in the efficacy of synaptic signaling, is a key property of synaptic communication that is vital to many brain functions. Hebbian forms of long-lasting synaptic plasticity-long-term potentiation (LTP) and long-term depression (LTD)-have been well studied and are considered to be the cellular basis for particular types of memory. Recently, homeostatic synaptic plasticity, a compensatory form of synaptic strength change, has attracted attention as a cellular mechanism that counteracts changes brought about by LTP and LTD to help stabilize neuronal network activity. New findings on the cellular mechanisms and molecular players of the two forms of plasticity are uncovering the interplay between them in individual neurons.
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Affiliation(s)
- Nathalia Vitureira
- Departmento de Fisiología, Facultad de Medicina, Universidad de la República, Montevideo 11100, Uruguay
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22
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Tokuoka H, Hatanaka T, Metzger D, Ichinose H. Nurr1 expression is regulated by voltage-dependent calcium channels and calcineurin in cultured hippocampal neurons. Neurosci Lett 2013; 559:50-5. [PMID: 24291696 DOI: 10.1016/j.neulet.2013.11.033] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Accepted: 11/19/2013] [Indexed: 12/01/2022]
Abstract
Nurr1 is an orphan nuclear transcription factor expressed in the brain. While Nurr1 is assumed to be an immediate early gene, it is not fully understood how Nurr1 expression is regulated in an activity-dependent manner in the central nervous system. Here, we investigated the molecular mechanisms underlying the regulation of Nurr1 expression in cultured hippocampal and cortical neurons. We found that upregulation of neural activity by high KCl and bicuculline enhances Nurr1 levels, while blockade of its activity by tetrodotoxin reduces Nurr1 levels. The induction of Nurr1 expression was mediated by voltage-dependent calcium channels (VDCCs), as shown by cadmium and VDCC-specific inhibitors. Furthermore, calcineurin, but not calcium/calmodulin-dependent protein kinase (CaMK) was critical for the induction. Thus, Nurr1 expression is regulated by VDCC and calcineurin in a cell-autonomous, neural activity-dependent manner.
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Affiliation(s)
- Hirofumi Tokuoka
- Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan
| | - Takayuki Hatanaka
- Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan
| | - Daniel Metzger
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch F-67400, France; CNRS UMR7104, Illkirch, France; INSERM U964, Illkirch, France; Université de Strasbourg, Strasbourg, France
| | - Hiroshi Ichinose
- Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan.
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23
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Abstract
Synapses undergo substantial activity-dependent and independent remodeling over time scales of minutes, hours, and days. Presumably, changes in presynaptic properties should be matched by corresponding changes in postsynaptic properties and vice versa. Wherever measured, presynaptic and postsynaptic molecular properties tend to correlate, yet these correlations are often quite imperfect, raising questions as the origins of such mismatches: Are these the outcome of "single snapshot" analyses of asynchronous remodeling processes? Alternatively, do these indicate that synapses genuinely vary in the "stoichiometries" of their presynaptic and postsynaptic molecular contents? If so, are these "stoichiometries" preserved over time? To address these questions, we followed the matching dynamics of the presynaptic active-zone molecule Munc13-1 and the postsynaptic molecule PSD-95 in networks of cultured cortical mouse neurons. We find that presynaptic and postsynaptic remodeling were generally well correlated, but the degree of this correlation was highly variable, with little and even negative correlation observed at some synapses. No evidence was found that remodeling in one compartment consistently preceded remodeling in the other. Interestingly, even though the Munc13-1 and PSD-95 contents of individual synapses changed considerably over 15-22 h, Munc13-1/PSD-95 ratios, which varied over a fourfold range, were well conserved over these durations. These findings indicate that the "stoichiometries" of presynaptic and postsynaptic molecules can genuinely differ among synapses and that synapses can maintain their specific stoichiometries even in face of extensive presynaptic and postsynaptic remodeling.
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Horellou S, Pascual O, Triller A, Marty S. Adaptive and non-adaptive changes in activity-deprived presynaptic terminals. Eur J Neurosci 2013; 39:61-71. [PMID: 24164653 DOI: 10.1111/ejn.12399] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Accepted: 09/26/2013] [Indexed: 11/29/2022]
Abstract
How the number of docked vesicles is regulated is still unclear. Following chronic activity blockade the number of docked vesicles increases, providing a model through which to address this issue. We tested the hypotheses that the number of docked vesicles is regulated with the size of the terminal, and by the level of Rab3-interacting molecule 1/2 (RIM1/2). We immobilized mouse hippocampal slice cultures by high-pressure freezing after 3 days of tetrodotoxin treatment and analysed them by electron microscopy. The number of docked vesicles, the size of the active zones and the amount of GluA2 were increased after activity blockade. However, there was no modification of either the total number of synaptic vesicles or the area of presynaptic profiles. Surprisingly, immunocytochemistry showed no change in the mean level of RIM1/2 per terminal but its distribution was modified. Additionally, there was no modification of the mean frequency or amplitude of miniature excitatory postsynaptic currents, but the distribution of amplitudes was modified. These results indicate a specific homeostatic regulation of the synaptic junction. The number of docked vesicles does not seem to be regulated by the amount of RIM1/2. The modification of the distribution, but not the amount, of RIM1/2 may explain the contradiction between the morphological and electrophysiological findings.
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Affiliation(s)
- Süzel Horellou
- Institute of Biology of the Ecole Normale Supérieure, 46 rue d'Ulm, 75005, Paris, France; INSERM U1024, Paris, France; CNRS UMR8197, Paris, France
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25
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Nimmervoll B, Flucher BE, Obermair GJ. Dominance of P/Q-type calcium channels in depolarization-induced presynaptic FM dye release in cultured hippocampal neurons. Neuroscience 2013; 253:330-40. [PMID: 24012836 PMCID: PMC3824072 DOI: 10.1016/j.neuroscience.2013.08.052] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Revised: 08/09/2013] [Accepted: 08/27/2013] [Indexed: 11/26/2022]
Abstract
We analyzed depolarization-induced synaptic FM dye release in hippocampal neurons. We pharmacologically isolated the contribution of voltage-gated Ca2+ channels. 85% of synapses utilize N- and P/Q-type channels, 15% only P/Q-type channels. In both groups of synapses release kinetics are determined by P/Q-type channels. We propose a more direct coupling of P/Q-type channels to synaptic release.
Neurotransmitter release probability is related by high power to the local concentration of calcium in presynaptic terminals, which in turn is controlled by voltage-gated calcium channels. P/Q- and N-type channels trigger synaptic transmission in the majority of neurons of the central nervous system. However, whether and under which conditions both channel types act cooperatively or independently is still insufficiently understood. Previous studies suggested either a dominance of N- or P/Q-type channels, or a synergistic action of both channels, depending on the experimental paradigms. Thus, to provide insight into the properties of neurotransmitter release in cultured mouse hippocampal neurons, we used quantitative analysis of FM dye release from presynaptic boutons induced by high potassium membrane depolarization. Increasing extracellular potassium concentrations revealed a sigmoid dependence of FM dye release to the stimulation strength. Individual and combined application of the P/Q- and N-type channel-specific blockers ω-agatoxin-IVA and ω-conotoxin-GVIA, respectively, allowed us to specifically isolate the contribution of both channel types to release triggered with 40 mM KCl. Analysis of the release kinetics and the fractional release amplitude demonstrate that, whereas in only 15% of the synapses release depended exclusively on P/Q-type channels, the majority of synapses (85%) contained both N- and P/Q-type channels. Nevertheless, the kinetics of FM dye release in synapses containing both channel types was determined by the P/Q-type channels. Together, our data suggest a more direct coupling of P/Q-type channels to synaptic release compared to N-type channels, which may explain the high prevalence of neurological P/Q-type channelopathies.
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Affiliation(s)
- B Nimmervoll
- Division of Physiology, Medical University Innsbruck, Fritz-Pregl-Str. 3, 6020 Innsbruck, Austria
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Gerkin RC, Nauen DW, Xu F, Bi GQ. Homeostatic regulation of spontaneous and evoked synaptic transmission in two steps. Mol Brain 2013; 6:38. [PMID: 23965342 PMCID: PMC3765453 DOI: 10.1186/1756-6606-6-38] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Accepted: 08/19/2013] [Indexed: 11/23/2022] Open
Abstract
Background During development both Hebbian and homeostatic mechanisms regulate synaptic efficacy, usually working in opposite directions in response to neuronal activity. Homeostatic plasticity has often been investigated by assaying changes in spontaneous synaptic transmission resulting from chronic circuit inactivation. However, effects of inactivation on evoked transmission have been less frequently reported. Importantly, contributions from the effects of circuit inactivation and reactivation on synaptic efficacy have not been individuated. Results Here we show for developing hippocampal neurons in primary culture that chronic inactivation with TTX results in increased mean amplitude of miniature synaptic currents (mEPSCs), but not evoked synaptic currents (eEPSCs). However, changes in quantal properties of transmission, partially reflected in mEPSCs, accurately predicted higher-order statistical properties of eEPSCs. The classical prediction of homeostasis – increased strength of evoked transmission – was realized after explicit circuit reactivation, in the form of cells’ pairwise connection probability. In contrast, distributions of eEPSC amplitudes for control and inactivated-then-reactivated groups matched throughout. Conclusions Homeostatic up-regulation of evoked synaptic transmission in developing hippocampal neurons in primary culture requires both the inactivation and reactivation stages, leading to a net increase in functional circuit connectivity.
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Affiliation(s)
- Richard C Gerkin
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA 15213, USA.
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Liu H, Chapman ER, Dean C. "Self" versus "non-self" connectivity dictates properties of synaptic transmission and plasticity. PLoS One 2013; 8:e62414. [PMID: 23658626 PMCID: PMC3639172 DOI: 10.1371/journal.pone.0062414] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2012] [Accepted: 03/21/2013] [Indexed: 11/29/2022] Open
Abstract
Autapses are connections between a neuron and itself. These connections are morphologically similar to “normal” synapses between two different neurons, and thus were long thought to have similar properties of synaptic transmission. However, this has not been directly tested. Here, using a micro-island culture assay in which we can define the number of interconnected cells, we directly compared synaptic transmission in excitatory autapses and in two-neuron micronetworks consisting of two excitatory neurons, in which a neuron is connected to one other neuron and to itself. We discovered that autaptic synapses are optimized for maximal transmission, and exhibited enhanced EPSC amplitude, charge, and RRP size compared to interneuronal synapses. However, autapses are deficient in several aspects of synaptic plasticity. Short-term potentiation only became apparent when a neuron was connected to another neuron. This acquisition of plasticity only required reciprocal innervation with one other neuron; micronetworks consisting of just two interconnected neurons exhibited enhanced short-term plasticity in terms of paired pulse ratio (PPR) and release probability (Pr), compared to autapses. Interestingly, when a neuron was connected to another neuron, not only interneuronal synapses, but also the autaptic synapses on itself exhibited a trend toward enhanced short-term plasticity in terms of PPR and Pr. Thus neurons can distinguish whether they are connected via “self” or “non-self” synapses and have the ability to adjust their plasticity parameters when connected to other neurons.
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Affiliation(s)
- Huisheng Liu
- Department of Neuroscience and Howard Hughes Medical Institute, University of Wisconsin, Madison, Wisconsin, United States of America
- * E-mail: (HL) (HL); (CD) (CD)
| | - Edwin R. Chapman
- Department of Neuroscience and Howard Hughes Medical Institute, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Camin Dean
- Department of Neuroscience and Howard Hughes Medical Institute, University of Wisconsin, Madison, Wisconsin, United States of America
- The European Neuroscience Institute Göttingen (ENI-G), Göttingen, Germany
- * E-mail: (HL) (HL); (CD) (CD)
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Peng X, Parsons TD, Balice-Gordon RJ. Determinants of synaptic strength vary across an axon arbor. J Neurophysiol 2012; 107:2430-41. [PMID: 22279193 PMCID: PMC3362249 DOI: 10.1152/jn.00615.2011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Accepted: 01/23/2012] [Indexed: 12/20/2022] Open
Abstract
We used synaptophysin-pHluorin expressed in hippocampal neurons to address how functional properties of terminals, namely, evoked release, total vesicle pool size, and release fraction, vary spatially across individual axon arbors. Consistent with previous reports, over short arbor distances (≈ 100 μm), evoked release was spatially heterogeneous when terminals contacted different postsynaptic dendrites or neurons. Regardless of the postsynaptic configuration, the evoked release and total vesicle pool size spatially covaried, suggesting that the fraction of synaptic vesicles available for release (release fraction) was similar over short distances. Evoked release and total vesicle pool size were highly correlated with the amount of NMDA receptors and PSD-95 in postsynaptic specialization. However, when individual axons were followed over longer distances (several hundred micrometers), a significant increase in evoked release was observed distally that was associated with an increased release fraction in distal terminals. The increase in distal release fraction can be accounted for by changes in individual vesicle release probability as well as readily releasable pool size. Our results suggest that for a single axon arbor, presynaptic strength indicated by evoked release over short distances is correlated with heterogeneity in total vesicle pool size, whereas over longer distances presynaptic strength is correlated with the spatial modulation of release fraction. Thus the mechanisms that determine synaptic strength differ depending on spatial scale.
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Affiliation(s)
- Xiaoyu Peng
- Department of Biology Graduate Group, University of Pennsylvania School of Arts and Sciences, Philadelphia, PA, USA
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30
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Independent vesicle pools underlie different modes of release during neuronal development. J Neurosci 2012; 32:1867-74. [PMID: 22302825 DOI: 10.1523/jneurosci.5181-11.2012] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Mature presynaptic terminals release neurotransmitter both in response to activity and spontaneously. We found that axons of rat hippocampal neurons initially show very high levels of exclusively spontaneous release, which progressively switches over to the mature phenotype during synapse formation. These two modes of vesicle cycling derive from distinct pools throughout development and the initiation of activity-dependent release was independent of postsynaptic contacts, suggesting it is an autonomous presynaptic event.
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Ostroff LE, Cain CK, Jindal N, Dar N, Ledoux JE. Stability of presynaptic vesicle pools and changes in synapse morphology in the amygdala following fear learning in adult rats. J Comp Neurol 2012; 520:295-314. [PMID: 21674493 DOI: 10.1002/cne.22691] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Changes in synaptic strength in the lateral amygdala (LA) that occur with fear learning are believed to mediate memory storage, and both presynaptic and postsynaptic mechanisms have been proposed to contribute. In a previous study we used serial section transmission electron microscopy (ssTEM) to observe differences in dendritic spine morphology in the adult rat LA after fear conditioning, conditioned inhibition (safety conditioning), or naïve control handling (Ostroff et al. [2010] Proc Natl Acad Sci U S A 107:9418-9423). We have now reconstructed axons from the same dataset and compared their morphology and relationship to the postsynaptic spines between the three training groups. Relative to the naïve control and conditioned inhibition groups, the ratio of postsynaptic density (PSD) area to docked vesicles at synapses was greater in the fear-conditioned group, while the size of the synaptic vesicle pools was unchanged. There was significant coherence in synapse size between neighboring boutons on the same axon in the naïve control and conditioned inhibition groups, but not in the fear-conditioned group. Within multiple-synapse boutons, both synapse size and the PSD-to-docked vesicle ratio were variable between individual synapses. Our results confirm that synaptic connectivity increases in the LA with fear conditioning. In addition, we provide evidence that boutons along the same axon and even synapses on the same bouton are independent in their structure and learning-related morphological plasticity.
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Affiliation(s)
- Linnaea E Ostroff
- Center for Neural Science, New York University, New York, New York, USA.
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32
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Differential control of presynaptic efficacy by postsynaptic N-cadherin and β-catenin. Nat Neurosci 2011; 15:81-9. [PMID: 22138644 PMCID: PMC3245860 DOI: 10.1038/nn.2995] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Accepted: 11/02/2011] [Indexed: 01/02/2023]
Abstract
N-cadherin is a homophilic adhesion protein that remains expressed at mature excitatory synapses beyond its developmental role in synapse formation. We investigated the trans-synaptic activity of N-cadherin in regulating synapse function in rodent cultured hippocampal neurons using optical methods and electrophysiology. Interfering with N-cadherin in postsynaptic neurons reduced basal release probability (p(r)) at inputs to the neuron, and this trans-synaptic impairment of release accompanied impaired vesicle endocytosis. Moreover, loss of the GluA2 AMPA-type glutamate receptor subunit, which decreased p(r) by itself, occluded the interference with postsynaptic N-cadherin. The loss of postsynaptic N-cadherin activity, however, did not affect the compensatory upregulation of p(r) induced by chronic activity silencing, whereas postsynaptic β-catenin deletion blocked this presynaptic homeostatic adaptation. Our findings suggest that postsynaptic N-cadherin helps link basal pre- and postsynaptic strengths to control the p(r) offset, whereas the p(r) gain adjustment requires a distinct trans-synaptic pathway involving β-catenin.
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Vitureira N, Letellier M, Goda Y. Homeostatic synaptic plasticity: from single synapses to neural circuits. Curr Opin Neurobiol 2011; 22:516-21. [PMID: 21983330 DOI: 10.1016/j.conb.2011.09.006] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Accepted: 09/21/2011] [Indexed: 10/16/2022]
Abstract
Homeostatic synaptic plasticity remains an enigmatic form of synaptic plasticity. Increasing interest on the topic has fuelled a surge of recent studies that have identified key molecular players and the signaling pathways involved. However, the new findings also highlight our lack of knowledge concerning some of the basic properties of homeostatic synaptic plasticity. In this review we address how homeostatic mechanisms balance synaptic strengths between the presynaptic and the postsynaptic terminals and across synapses that share the same postsynaptic neuron.
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Affiliation(s)
- Nathalia Vitureira
- MRC Laboratory for Molecular Cell Biology and Cell Biology Unit, University College London, Gower Street, London WC1E 6BT, UK
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Neuronal activity drives matching of pre- and postsynaptic function during synapse maturation. Nat Neurosci 2011; 14:688-90. [DOI: 10.1038/nn.2826] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Accepted: 04/01/2011] [Indexed: 11/08/2022]
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CALM, A Clathrin Assembly Protein, Influences Cell Surface GluR2 Abundance. Neuromolecular Med 2011; 13:88-90. [DOI: 10.1007/s12017-010-8142-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2010] [Accepted: 11/23/2010] [Indexed: 11/25/2022]
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Quantal analysis reveals a functional correlation between presynaptic and postsynaptic efficacy in excitatory connections from rat neocortex. J Neurosci 2010; 30:1441-51. [PMID: 20107071 DOI: 10.1523/jneurosci.3244-09.2010] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
At many central synapses, the presynaptic bouton and postsynaptic density are structurally correlated. However, it is unknown whether this correlation extends to the functional properties of the synapses. To investigate this, we made recordings from synaptically coupled pairs of pyramidal neurons in rat visual cortex. The mean peak amplitude of EPSPs recorded from pairs of L2/3 neurons ranged between 40 microV and 2.9 mV. EPSP rise times were consistent with the majority of the synapses being located on basal dendrites; this was confirmed by full anatomical reconstructions of a subset of connected pairs. Over a third of the connections could be described using a quantal model that assumed simple binomial statistics. Release probability (P(r)) and quantal size (Q), as measured at the somatic recording site, showed considerable heterogeneity between connections. However, across the population of connections, values of P(r) and Q for individual connections were positively correlated with one another. This correlation also held for inputs to layer 5 pyramidal neurons from both layer 2/3 and neighboring layer 5 pyramidal neurons, suggesting that during development of cortical connections presynaptic and postsynaptic strengths are dependently scaled. For 2/3 to 2/3 connections, mean EPSP amplitude was correlated with both Q and P(r) values but uncorrelated with N, the number of functional release sites mediating the connection. The efficacy of a cortical connection is thus set by coordinated presynaptic and postsynaptic strength.
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Time course of neuronal and synaptic plasticity in dorsal cochlear nucleus of guinea pig following chronic kanamycin-induced deafness. Brain Res 2010; 1328:118-29. [DOI: 10.1016/j.brainres.2010.01.055] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2009] [Revised: 01/16/2010] [Accepted: 01/20/2010] [Indexed: 01/26/2023]
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Stress at learning facilitates memory formation by regulating AMPA receptor trafficking through a glucocorticoid action. Neuropsychopharmacology 2010; 35:674-85. [PMID: 19890264 PMCID: PMC3055605 DOI: 10.1038/npp.2009.172] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Stress and glucocorticoids (GCs) can facilitate memory formation. However, the molecular mechanisms mediating their effects are largely unknown. Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor (AMPAR) trafficking has been implicated in the changes in synaptic strength at central glutamatergic synapses associated with memory formation. In cell cultures, corticosterone has been shown to condition the synaptic trafficking of the AMPAR GluA2 subunit. In this study, we investigated the involvement of GluA2 trafficking in the facilitation of learning by stress. Using the water maze spatial task involving different stress levels, mice trained under more stressful conditions (water at 22 degrees C) showed better learning and memory, and higher post-training corticosterone levels, than mice trained under lower stress (water at 30 degrees C). Strikingly, this facilitated learning by stress was accompanied by enhanced synaptic expression of GluA2 AMPARs that was not observed in mice trained under less stressful conditions. Interfering with GC actions by injecting the GC synthesis inhibitor, metyrapone, blocked both the memory facilitation and the enhanced GluA2 trafficking induced by stressful learning. Intracerebroventricular infusion of the peptide, pep2m, that blocks GluA2 synaptic trafficking by interfering with the interaction between N-ethylmaleimide-sensitive factor and GluA2, impaired immediate performance at learning as well as long-term memory retrieval, supporting a causal role for GluA2 trafficking in stress-induced facilitation of spatial learning and memory. Evidence for the involvement of the neural cell adhesion molecule N-cadherin in interaction with GluA2 is also provided. These findings underscore a new mechanism whereby stress can improve memory function.
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Abstract
Although drugs used to treat several neurological diseases are presumed to target synapses that secrete dopamine (DA), relatively little is known about synaptic vesicle (SV) release mechanisms at single DA synapses. We found that the relative probability of release (Pr) varied between individual DA synapses. Furthermore, DA terminals generally exhibited lower Pr than glutamatergic hippocampal (Hpc) terminals, suggesting that DA release is less reliable than the release of glutamate. Our mathematical model of fluorescence loss shows that Pr is regulated by two independent and heterogeneous elements. First, the size of the recycling SV pool regulates Pr. Second, Pr is also independently regulated by additional factors, which are reflected in the time constant of FM 1-43 destaining, tau. We found that the observed difference in Pr between Hpc and DA neurons results because the recycling SV pool is smaller in DA neurons than in Hpc neurons. However, tau does not vary between these two neuron populations. We also identified a population of functional nonsynaptic boutons in DA axons, which are not associated with a postsynaptic element and which are not functionally different from boutons that formed conventional synapses. Our work provides a new approach to the study of SV exocytosis in DA neurons and shows that synaptic terminals of DA neurons are functionally heterogeneous and differ from excitatory terminals in terms of Pr.
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Autapses and networks of hippocampal neurons exhibit distinct synaptic transmission phenotypes in the absence of synaptotagmin I. J Neurosci 2009; 29:7395-403. [PMID: 19515907 DOI: 10.1523/jneurosci.1341-09.2009] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Synaptotagmin-I (syt-I) is required for rapid neurotransmitter release in mouse hippocampal neurons. However, contradictory results have been reported regarding evoked and spontaneous secretion from syt-I knock-out (KO) neurons. Here, we compared synaptic transmission in two different hippocampal neuron preparations: autaptic cultures in which a single isolated cell innervates itself, and dissociated mass cultures in which individual cells are innervated by neighboring cells. In autaptic cultures, the total extent of evoked release, size of readily releasable pool of synaptic vesicles, and release probability were unchanged in syt-I KO neurons. In contrast, in cultures containing multiple interconnected neurons, total evoked release, the number of docked vesicles, and release probability, were significantly reduced in syt-I KO neurons. Using a micronetwork system in which we varied the number of cells on an island, we found that the frequency of spontaneous synaptic vesicle fusion events (minis) was unchanged in syt-I KO neurons when two or fewer cells were present on an island. However, in micronetworks composed of three or more neurons, mini frequency was increased threefold to fivefold in syt-I KO neurons compared with wild type. Moreover, interneuronal synapses exhibited higher rates of spontaneous release than autaptic synapses. This higher rate was attributable to an increase in release probability because excitatory hippocampal neurons in micronetworks formed a set number of synapses per cell regardless of the number of connected neurons. Thus, aspects of synaptic transmission differ between autaptic and dissociated cultures, and the synaptic transmission phenotype, resulting from loss of syt-I, is dictated by the connectivity of neurons.
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Tuning of synapse number, structure and function in the cochlea. Nat Neurosci 2009; 12:444-53. [DOI: 10.1038/nn.2293] [Citation(s) in RCA: 252] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2008] [Accepted: 02/12/2009] [Indexed: 11/08/2022]
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Counting the number of releasable synaptic vesicles in a presynaptic terminal. Proc Natl Acad Sci U S A 2009; 106:2945-50. [PMID: 19202060 DOI: 10.1073/pnas.0811017106] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Synaptic transmission depends on the continued availability of neurotransmitter-filled synaptic vesicles (SVs) for triggered release from presynaptic boutons. Surprisingly, small boutons in the brain, that already contain comparatively few SVs, are thought to retain the majority of these SVs in a "reserve" pool that is not mobilized under physiological conditions. Why such a scarce synaptic resource is normally inaccessible has been a matter of debate. Here, we readdress this issue by developing an electrophysiological approach for counting SVs released from boutons formed by a single, isolated neuron on itself ("autapses"). We show that, after treatment with Bafilomycin A1 to prevent reloading of discharged SVs with glutamate, each SV is counted only once on first-time release. Hence, by integrating all autaptic currents as they run down over time, we can estimate the total number of SVs released by a single neuron. This total can be normalized to the number of boutons on the neuron, giving the mean number of SVs released per bouton. We estimate that up to approximately 130 vesicles can be released per bouton over approximately 10 min of stimulation at 0.2 Hz. This number of vesicles represents a substantial proportion of the total number of SVs (100-200) that have been counted in these boutons by using electron microscopy. Thus, mild electrical stimulation, when maintained for sufficient time, causes the eventual release of many of the SVs in a bouton, including those in the putative reserve pool. This result suggests that SVs are functionally homogeneous in that the majority can contribute to basal synaptic transmission.
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Abstract
Homeostatic synaptic scaling is a form of synaptic plasticity that adjusts the strength of all of a neuron's excitatory synapses up or down to stabilize firing. Current evidence suggests that neurons detect changes in their own firing rates through a set of calcium-dependent sensors that then regulate receptor trafficking to increase or decrease the accumulation of glutamate receptors at synaptic sites. Additional mechanisms may allow local or network-wide changes in activity to be sensed through parallel pathways, generating a nested set of homeostatic mechanisms that operate over different temporal and spatial scales.
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