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Wu LG, Chan CY. Membrane transformations of fusion and budding. Nat Commun 2024; 15:21. [PMID: 38167896 PMCID: PMC10761761 DOI: 10.1038/s41467-023-44539-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 12/15/2023] [Indexed: 01/05/2024] Open
Abstract
Membrane fusion and budding mediate fundamental processes like intracellular trafficking, exocytosis, and endocytosis. Fusion is thought to open a nanometer-range pore that may subsequently close or dilate irreversibly, whereas budding transforms flat membranes into vesicles. Reviewing recent breakthroughs in real-time visualization of membrane transformations well exceeding this classical view, we synthesize a new model and describe its underlying mechanistic principles and functions. Fusion involves hemi-to-full fusion, pore expansion, constriction and/or closure while fusing vesicles may shrink, enlarge, or receive another vesicle fusion; endocytosis follows exocytosis primarily by closing Ω-shaped profiles pre-formed through the flat-to-Λ-to-Ω-shape transition or formed via fusion. Calcium/SNARE-dependent fusion machinery, cytoskeleton-dependent membrane tension, osmotic pressure, calcium/dynamin-dependent fission machinery, and actin/dynamin-dependent force machinery work together to generate fusion and budding modes differing in pore status, vesicle size, speed and quantity, controls release probability, synchronization and content release rates/amounts, and underlies exo-endocytosis coupling to maintain membrane homeostasis. These transformations, underlying mechanisms, and functions may be conserved for fusion and budding in general.
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Affiliation(s)
- Ling-Gang Wu
- National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA.
| | - Chung Yu Chan
- National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA
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Adult Neural Plasticity in Naked Mole-Rats: Implications of Fossoriality, Longevity and Sociality on the Brain's Capacity for Change. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1319:105-135. [PMID: 34424514 DOI: 10.1007/978-3-030-65943-1_4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Naked mole-rats (Heterocephalus glaber) are small African rodents that have many unique behavioral and physiological adaptations well-suited for testing hypotheses about mammalian neural plasticity. In this chapter, we focus on three features of naked mole-rat biology and how they impact neural plasticity in this species: (1) their fossorial lifestyle, (2) their extreme longevity with a lack of demonstrable senescence, and (3) their unusual social structure. Critically, each of these features requires some degree of biological flexibility. First, their fossorial habitat situates them in an environment with characteristics to which the central nervous system is particularly sensitive (e.g., oxygen content, photoperiod, spatial complexity). Second, their long lifespan requires adaptations to combat senescence and declines in neural functioning. Finally, their extreme reproductive skew and sustained ability for release from reproductive suppression indicates remarkable neural sensitivity to the sociosexual environment that is distinct from chronological age. These three features of naked mole-rat life are not mutually exclusive, but they do each offer unique considerations for the possibilities, constraints, and mechanisms associated with adult neural plasticity.
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Lin CY, Chen J, Chen PH, Chang TC, Wu Y, Eshraghian JK, Moon J, Yoo S, Wang YH, Chen WC, Wang ZY, Huang HC, Li Y, Miao X, Lu WD, Sze SM. Adaptive Synaptic Memory via Lithium Ion Modulation in RRAM Devices. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2020; 16:e2003964. [PMID: 32996256 DOI: 10.1002/smll.202003964] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 08/12/2020] [Indexed: 06/11/2023]
Abstract
Biologically plausible computing systems require fine-grain tuning of analog synaptic characteristics. In this study, lithium-doped silicate resistive random access memory with a titanium nitride (TiN) electrode mimicking biological synapses is demonstrated. Biological plausibility of this RRAM device is thought to occur due to the low ionization energy of lithium ions, which enables controllable forming and filamentary retraction spontaneously or under an applied voltage. The TiN electrode can effectively store lithium ions, a principle widely adopted from battery construction, and allows state-dependent decay to be reliably achieved. As a result, this device offers multi-bit functionality and synaptic plasticity for simulating various strengths in neuronal connections. Both short-term memory and long-term memory are emulated across dynamical timescales. Spike-timing-dependent plasticity and paired-pulse facilitation are also demonstrated. These mechanisms are capable of self-pruning to generate efficient neural networks. Time-dependent resistance decay is observed for different conductance values, which mimics both biological and artificial memory pruning and conforms to the trend of the biological brain that prunes weak synaptic connections. By faithfully emulating learning rules that exist in human's higher cortical areas from STDP to synaptic pruning, the device has the capacity to drive forward the development of highly efficient neuromorphic computing systems.
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Affiliation(s)
- Chih-Yang Lin
- Department of Physics, National Sun Yat-sen University, No.70 Lien-hai Road, Kaohsiung, 80424, Taiwan
| | - Jia Chen
- Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, No.1037 Luoyu Road, Wuhan, 430074, China
| | - Po-Hsun Chen
- Department of Applied Science, R.O.C. Naval Academy, No.669 Junxiao Road, Kaohsiung, 81345, Taiwan
- Center for Nanoscience and Nanotechnology, National Sun Yat-sen University, No.70 Lien-hai Road, Kaohsiung, 80424, Taiwan
| | - Ting-Chang Chang
- Department of Physics, The Center of Crystal Research, National Sun Yat-sen University, No.70 Lien-hai Road, Kaohsiung, 80424, Taiwan
| | - Yuting Wu
- Electrical Engineering and Computer Science, University of Michigan, No.1301 Beal Avenue, Ann Arbor, Michigan, 48109-2122, USA
| | - Jason K Eshraghian
- Electrical Engineering and Computer Science, University of Michigan, No.1301 Beal Avenue, Ann Arbor, Michigan, 48109-2122, USA
| | - John Moon
- Electrical Engineering and Computer Science, University of Michigan, No.1301 Beal Avenue, Ann Arbor, Michigan, 48109-2122, USA
| | - Sangmin Yoo
- Electrical Engineering and Computer Science, University of Michigan, No.1301 Beal Avenue, Ann Arbor, Michigan, 48109-2122, USA
| | - Yu-Hsun Wang
- Department of Electronics Engineering and Institute of Electronics, National Chiao Tung University, No.1001 University Road, Hsinchu, 30010, Taiwan
| | - Wen-Chung Chen
- Department of Materials and Optoelectronic Science, National Sun Yat-sen University, No.70 Lien-hai Road, Kaohsiung, 80424, Taiwan
| | - Zhi-Yang Wang
- Department of Materials and Optoelectronic Science, National Sun Yat-sen University, No.70 Lien-hai Road, Kaohsiung, 80424, Taiwan
| | - Hui-Chun Huang
- Department of Materials and Optoelectronic Science, National Sun Yat-sen University, No.70 Lien-hai Road, Kaohsiung, 80424, Taiwan
| | - Yi Li
- Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, No.1037 Luoyu Road, Wuhan, 430074, China
| | - Xiangshui Miao
- Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, No.1037 Luoyu Road, Wuhan, 430074, China
| | - Wei D Lu
- Electrical Engineering and Computer Science, University of Michigan, No.1301 Beal Avenue, Ann Arbor, Michigan, 48109-2122, USA
| | - Simon M Sze
- Department of Electronics Engineering and Institute of Electronics, National Chiao Tung University, No.1001 University Road, Hsinchu, 30010, Taiwan
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Dhuriya YK, Sharma D. Neuronal Plasticity: Neuronal Organization is Associated with Neurological Disorders. J Mol Neurosci 2020; 70:1684-1701. [PMID: 32504405 DOI: 10.1007/s12031-020-01555-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 04/13/2020] [Indexed: 12/18/2022]
Abstract
Stimuli from stressful events, attention in the classroom, and many other experiences affect the functionality of the brain by changing the structure or reorganizing the connections between neurons and their communication. Modification of the synaptic transmission is a vital mechanism for generating neural activity via internal or external stimuli. Neuronal plasticity is an important driving force in neuroscience research, as it is the basic process underlying learning and memory and is involved in many other functions including brain development and homeostasis, sensorial training, and recovery from brain injury. Indeed, neuronal plasticity has been explored in numerous studies, but it is still not clear how neuronal plasticity affects the physiology and morphology of the brain. Thus, unraveling the molecular mechanisms of neuronal plasticity is essential for understanding the operation of brain functions. In this timeline review, we discuss the molecular mechanisms underlying different forms of synaptic plasticity and their association with neurodegenerative/neurological disorders as a consequence of alterations in neuronal plasticity.
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Affiliation(s)
- Yogesh Kumar Dhuriya
- Developmental Toxicology Laboratory, Systems Toxicology and Health Risk Assessment Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR) Vishvigyan Bhawan, 31, Mahatma Gandhi Marg, Lucknow, 226 001, India
| | - Divakar Sharma
- Department of Biochemistry, National JALMA Institute for Leprosy and Other Mycobacterial Diseases, Tajganj, Agra, India. .,CRF, Mass Spectrometry Laboratory, Kusuma School of Biological Sciences (KSBS), Indian Institute of Technology-Delhi (IIT-D), Delhi, 110016, India.
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Tai Z, Guan P, Wang Z, Li L, Zhang T, Li G, Liu JX. Common responses of fish embryos to metals: an integrated analysis of transcriptomes and methylomes in zebrafish embryos under the stress of copper ions or silver nanoparticles. Metallomics 2019; 11:1452-1464. [DOI: 10.1039/c9mt00125e] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
This study demonstrated the common responses of differentially expressed genes (DEGs) and differentially methylated regions (DMRs) under Cu2+ or AgNPs stresses in zebrafish, and verified the correlation of the gene transcription and the methylation status of some common DMGs.
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Affiliation(s)
- ZhiPeng Tai
- College of Fisheries
- Key Laboratory of Freshwater Animal Breeding
- Ministry of Agriculture
- Huazhong Agricultural University
- Wuhan
| | - PengPeng Guan
- College of Informatics
- Agricultural Bioinformatics Key Laboratory of Hubei Province
- Hubei Engineering Technology Research Center of Agricultural Big Data
- Huazhong Agricultural University
- Wuhan
| | - ZiYang Wang
- College of Fisheries
- Key Laboratory of Freshwater Animal Breeding
- Ministry of Agriculture
- Huazhong Agricultural University
- Wuhan
| | - LingYa Li
- College of Fisheries
- Key Laboratory of Freshwater Animal Breeding
- Ministry of Agriculture
- Huazhong Agricultural University
- Wuhan
| | - Ting Zhang
- College of Fisheries
- Key Laboratory of Freshwater Animal Breeding
- Ministry of Agriculture
- Huazhong Agricultural University
- Wuhan
| | - GuoLiang Li
- College of Informatics
- Agricultural Bioinformatics Key Laboratory of Hubei Province
- Hubei Engineering Technology Research Center of Agricultural Big Data
- Huazhong Agricultural University
- Wuhan
| | - Jing-Xia Liu
- College of Fisheries
- Key Laboratory of Freshwater Animal Breeding
- Ministry of Agriculture
- Huazhong Agricultural University
- Wuhan
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Inhibitory Signaling to Ion Channels in Hippocampal Neurons Is Differentially Regulated by Alternative Macromolecular Complexes of RGS7. J Neurosci 2018; 38:10002-10015. [PMID: 30315127 DOI: 10.1523/jneurosci.1378-18.2018] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 09/01/2018] [Accepted: 09/26/2018] [Indexed: 12/14/2022] Open
Abstract
The neuromodulatory effects of GABA on pyramidal neurons are mediated by GABAB receptors (GABABRs) that signal via a conserved G-protein-coupled pathway. Two prominent effectors regulated by GABABRs include G-protein inwardly rectifying K+ (GIRK) and P/Q/N type voltage-gated Ca2+ (CaV2) ion channels that control excitability and synaptic output of these neurons, respectively. Regulator of G-protein signaling 7 (RGS7) has been shown to control GABAB effects, yet the specificity of its impacts on effector channels and underlying molecular mechanisms is poorly understood. In this study, we show that hippocampal RGS7 forms two distinct complexes with alternative subunit configuration bound to either membrane protein R7BP (RGS7 binding protein) or orphan receptor GPR158. Quantitative biochemical experiments show that both complexes account for targeting nearly the entire pool of RGS7 to the plasma membrane. We analyzed the effect of genetic elimination in mice of both sexes and overexpression of various components of RGS7 complex by patch-clamp electrophysiology in cultured neurons and brain slices. We report that RGS7 prominently regulates GABABR signaling to CaV2, in addition to its known involvement in modulating GIRK. Strikingly, only complexes containing R7BP, but not GPR158, accelerated the kinetics of both GIRK and CaV2 modulation by GABABRs. In contrast, GPR158 overexpression exerted the opposite effect and inhibited RGS7-assisted temporal modulation of GIRK and CaV2 by GABA. Collectively, our data reveal mechanisms by which distinctly composed macromolecular complexes modulate the activity of key ion channels that mediate the inhibitory effects of GABA on hippocampal CA1 pyramidal neurons.SIGNIFICANCE STATEMENT This study identifies the contributions of distinct macromolecular complexes containing a major G-protein regulator to controlling key ion channel function in hippocampal neurons with implications for understanding molecular mechanisms underlying synaptic plasticity, learning, and memory.
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Zhang L, Duan X, He N, Chen X, Shi J, Li W, Xu L, Li H. Exposure to lethal levels of benzo[a]pyrene or cadmium trigger distinct protein expression patterns in earthworms (Eisenia fetida). THE SCIENCE OF THE TOTAL ENVIRONMENT 2017; 595:733-742. [PMID: 28407590 DOI: 10.1016/j.scitotenv.2017.04.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 03/30/2017] [Accepted: 04/01/2017] [Indexed: 06/07/2023]
Abstract
UNLABELLED Different pollutants induce distinct toxic responses in earthworms (Eisenia fetida). Here, we used proteomics techniques to compare the responses of E. fetida to exposure to the 10% lethal concentration (14d-LC10) of benzo[a]pyrene (BaP) or cadmium (Cd) in natural red soil (China). BaP exposure markedly induced the expression of oxidation-reduction proteins, whereas Cd exposure mainly induced the expression of proteins involved in transcription- and translation-related processes. Furthermore, calmodulin-binding proteins were differentially expressed upon exposure to different pollutants. The calcium (Ca2+)-binding cytoskeletal element myosin was down-regulated upon BaP treatment, whereas the Ca2+-binding cytoskeletal element tropomyosin-1 was up-regulated upon Cd treatment. Some proteins exhibited opposite responses to the two pollutants. For instance, catalase (CAT) and heat shock protein 70 were up-regulated upon BaP treatment and down-regulated upon Cd treatment. A significant (p<0.05, one-way ANOVA with least-significant difference (LSD) test) increase in the level of reactive oxygen species (ROS) and CAT activity further showed that BaP mainly induces oxidative stress. Real-time PCR analysis showed that mRNA expression often did not correlate well with protein expression in earthworms subjected to Cd or BaP treatment. In addition, the expression of the gene encoding the protein metallothionein, which was not detected in the protein analysis, was induced upon Cd treatment, but slightly reduced upon BaP treatment. Therefore, BaP and Cd have distinct effects on the protein profile of E. Fetida with BaP markedly inducing ROS activity, and Cd mainly triggering genotoxicity. CAPSULE SUMMARY Distinct patterns of protein expression are induced in earthworms upon exposure to different pollutants; BaP markedly induces high levels of ROS, while Cd resultes in genotoxicity.
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Affiliation(s)
- Lihao Zhang
- College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, People's Republic of China; Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing 210014, People's Republic of China
| | - Xiaochen Duan
- College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, People's Republic of China; College of Resources, Environment, and Planning, Dezhou University, Dezhou 253023, People's Republic of China
| | - Nannan He
- College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, People's Republic of China
| | - Xu Chen
- College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, People's Republic of China
| | - Jinli Shi
- College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, People's Republic of China
| | - Weiming Li
- Nanjing Scientific Institute of Vegetables and Flowers, Nanjing 210095, People's Republic of China
| | - Li Xu
- College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, People's Republic of China; Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing 210014, People's Republic of China.
| | - Huixin Li
- College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, People's Republic of China.
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Gleizes M, Perrier SP, Fonta C, Nowak LG. Prominent facilitation at beta and gamma frequency range revealed with physiological calcium concentration in adult mouse piriform cortex in vitro. PLoS One 2017; 12:e0183246. [PMID: 28820903 PMCID: PMC5562311 DOI: 10.1371/journal.pone.0183246] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Accepted: 08/01/2017] [Indexed: 12/25/2022] Open
Abstract
Neuronal activity is characterized by a diversity of oscillatory phenomena that are associated with multiple behavioral and cognitive processes, yet the functional consequences of these oscillations are not fully understood. Our aim was to determine whether and how these different oscillatory activities affect short-term synaptic plasticity (STP), using the olfactory system as a model. In response to odorant stimuli, the olfactory bulb displays a slow breathing rhythm as well as beta and gamma oscillations. Since the firing of olfactory bulb projecting neurons is phase-locked with beta and gamma oscillations, structures downstream from the olfactory bulb should be driven preferentially at these frequencies. We examined STP exhibited by olfactory bulb inputs in slices of adult mouse piriform cortex maintained in vitro in an in vivo-like ACSF (calcium concentration: 1.1 mM). We replaced the presynaptic neuronal firing rate by repeated electrical stimulation (frequency between 3.125 and 100 Hz) applied to the lateral olfactory tract. Our results revealed a considerable enhancement of postsynaptic response amplitude for stimulation frequencies in the beta and gamma range. A phenomenological model of STP fitted to the data suggests that the experimental results can be explained by the interplay between three mechanisms: a short-term facilitation mechanism (time constant ≈160 msec), and two short-term depression mechanisms (recovery time constants <20 msec and ≈140 msec). Increasing calcium concentration (2.2 mM) resulted in an increase in the time constant of facilitation and in a strengthening of the slowest depression mechanism. As a result, response enhancement was reduced and its peak shifted toward the low beta and alpha ranges while depression became predominant in the gamma band. Using environmental conditions corresponding to those that prevail in vivo, our study shows that STP in the lateral olfactory tract to layer Ia synapse allows amplification of olfactory bulb inputs at beta and gamma frequencies.
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Affiliation(s)
- Marie Gleizes
- Centre de Recherche Cerveau et Cognition, Université de Toulouse, Toulouse, France
- Unité Mixte de Recherche 5549, Centre National de la Recherche Scientifique, Toulouse, France
| | - Simon P. Perrier
- Centre de Recherche Cerveau et Cognition, Université de Toulouse, Toulouse, France
- Unité Mixte de Recherche 5549, Centre National de la Recherche Scientifique, Toulouse, France
| | - Caroline Fonta
- Centre de Recherche Cerveau et Cognition, Université de Toulouse, Toulouse, France
- Unité Mixte de Recherche 5549, Centre National de la Recherche Scientifique, Toulouse, France
| | - Lionel G. Nowak
- Centre de Recherche Cerveau et Cognition, Université de Toulouse, Toulouse, France
- Unité Mixte de Recherche 5549, Centre National de la Recherche Scientifique, Toulouse, France
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Calcium-Dependent Protein Kinase C Is Not Required for Post-Tetanic Potentiation at the Hippocampal CA3 to CA1 Synapse. J Neurosci 2017; 36:6393-402. [PMID: 27307229 DOI: 10.1523/jneurosci.0708-16.2016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 04/30/2016] [Indexed: 12/11/2022] Open
Abstract
UNLABELLED Post-tetanic potentiation (PTP) is a widespread form of short-term synaptic plasticity in which a period of elevated presynaptic activation leads to synaptic enhancement that lasts tens of seconds to minutes. A leading hypothesis for the mechanism of PTP is that tetanic stimulation elevates presynaptic calcium that in turn activates calcium-dependent protein kinase C (PKC) isoforms to phosphorylate targets and enhance neurotransmitter release. Previous pharmacological studies have implicated this mechanism in PTP at hippocampal synapses, but the results are controversial. Here we combine genetic and pharmacological approaches to determine the role of classic PKC isoforms in PTP. We find that PTP is unchanged in PKC triple knock-out (TKO) mice in which all calcium-dependent PKC isoforms have been eliminated (PKCα, PKCβ, and PKCγ). We confirm previous studies and find that in wild-type mice 10 μm of the PKC inhibitor GF109203 eliminates PTP and the PKC activator PDBu enhances neurotransmitter release and occludes PTP. However, we find that the same concentrations of GF109203 and PDBu have similar effects in TKO animals. We also show that 2 μm GF109203 does not abolish PTP even though it inhibits the PDBu-dependent phosphorylation of PKC substrates. We conclude that at the CA3 to CA1 synapse Ca(2+)-dependent PKC isoforms do not serve as calcium sensors to mediate PTP. SIGNIFICANCE STATEMENT Neurons dynamically regulate neurotransmitter release through many processes known collectively as synaptic plasticity. Post-tetanic potentiation (PTP) is a widespread form of synaptic plasticity that lasts for tens of seconds that may have important computational roles and contribute to short-term memory. According to a leading mechanism, presynaptic calcium activates protein kinase C (PKC) to increase neurotransmitter release. Pharmacological studies have also implicated this mechanism at hippocampal CA3 to CA1 synapses, but there are concerns about the specificity of PKC activators and inhibitors. We therefore used a molecular genetic approach and found that PTP was unaffected when all calcium-dependent PKC isozymes were eliminated. We conclude that PKC isozymes are not the calcium sensors that mediate PTP at the CA3 to CA1 synapse.
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Shaban H, O’Connor R, Ovsepian SV, Dinan TG, Cryan JF, Schellekens H. Electrophysiological approaches to unravel the neurobiological basis of appetite and satiety: use of the multielectrode array as a screening strategy. Drug Discov Today 2017; 22:31-42. [DOI: 10.1016/j.drudis.2016.09.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 08/03/2016] [Accepted: 09/06/2016] [Indexed: 01/10/2023]
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Wan CJ, Liu YH, Zhu LQ, Feng P, Shi Y, Wan Q. Short-Term Synaptic Plasticity Regulation in Solution-Gated Indium-Gallium-Zinc-Oxide Electric-Double-Layer Transistors. ACS APPLIED MATERIALS & INTERFACES 2016; 8:9762-9768. [PMID: 27007748 DOI: 10.1021/acsami.5b12726] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In the biological nervous system, synaptic plasticity regulation is based on the modulation of ionic fluxes, and such regulation was regarded as the fundamental mechanism underlying memory and learning. Inspired by such biological strategies, indium-gallium-zinc-oxide (IGZO) electric-double-layer (EDL) transistors gated by aqueous solutions were proposed for synaptic behavior emulations. Short-term synaptic plasticity, such as paired-pulse facilitation, high-pass filtering, and orientation tuning, was experimentally emulated in these EDL transistors. Most importantly, we found that such short-term synaptic plasticity can be effectively regulated by alcohol (ethyl alcohol) and salt (potassium chloride) additives. Our results suggest that solution gated oxide-based EDL transistors could act as the platforms for short-term synaptic plasticity emulation.
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Affiliation(s)
- Chang Jin Wan
- School of Electronic Science & Engineering and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
- Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences , Ningbo 315201, China
| | - Yang Hui Liu
- Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences , Ningbo 315201, China
| | - Li Qiang Zhu
- Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences , Ningbo 315201, China
| | - Ping Feng
- School of Electronic Science & Engineering and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
| | - Yi Shi
- School of Electronic Science & Engineering and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
| | - Qing Wan
- School of Electronic Science & Engineering and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
- Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences , Ningbo 315201, China
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Baydyuk M, Xu J, Wu LG. The calyx of Held in the auditory system: Structure, function, and development. Hear Res 2016; 338:22-31. [PMID: 27018297 DOI: 10.1016/j.heares.2016.03.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Revised: 03/10/2016] [Accepted: 03/17/2016] [Indexed: 12/19/2022]
Abstract
The calyx of Held synapse plays an important role in the auditory system, relaying information about sound localization via fast and precise synaptic transmission, which is achieved by its specialized structure and giant size. During development, the calyx of Held undergoes anatomical, morphological, and physiological changes necessary for performing its functions. The large dimensions of the calyx of Held nerve terminal are well suited for direct electrophysiological recording of many presynaptic events that are difficult, if not impossible to record at small conventional synapses. This unique accessibility has been used to investigate presynaptic ion channels, transmitter release, and short-term plasticity, providing invaluable information about basic presynaptic mechanisms of transmission at a central synapse. Here, we review anatomical and physiological specializations of the calyx of Held, summarize recent studies that provide new mechanisms important for calyx development and reliable synaptic transmission, and examine fundamental presynaptic mechanisms learned from studies using calyx as a model nerve terminal. This article is part of a Special Issue entitled <Annual Reviews 2016>.
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Affiliation(s)
- Maryna Baydyuk
- National Institute of Neurological Disorders and Stroke, 35 Convent Dr., Bldg 35, Bethesda, MD 20892, USA.
| | - Jianhua Xu
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA; Department of Neurology, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Ling-Gang Wu
- National Institute of Neurological Disorders and Stroke, 35 Convent Dr., Bldg 35, Bethesda, MD 20892, USA
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Lee SR, Adams PJ, Yue DT. Large Ca²⁺-dependent facilitation of Ca(V)2.1 channels revealed by Ca²⁺ photo-uncaging. J Physiol 2016; 593:2753-78. [PMID: 25809476 DOI: 10.1113/jp270091] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Accepted: 03/18/2015] [Indexed: 01/30/2023] Open
Abstract
KEY POINTS CaV 2.1 channels constitute a dominant Ca(2+) entry pathway into brain neurons, triggering downstream Ca(2+) -dependent processes such as neurotransmitter release. CaV 2.1 is itself modulated by Ca(2+) , resulting in activity-dependent enhancement of channel opening termed Ca(2+) -dependent facilitation (CDF). Real-time Ca(2+) imaging and Ca(2+) uncaging here reveal that CDF turns out to be strikingly faster, more Ca(2+) sensitive, and larger than anticipated on previous grounds. Robust resolution of the quantitative profile of CDF enables deduction of a realistic biophysical model for this process. These results suggest that CaV 2.1 CDF would figure most prominently in short-term synaptic plasticity and cerebellar Purkinje cell rhythmicity. ABSTRACT CaV 2.1 (P-type) voltage-gated Ca(2+) channels constitute a major source of neuronal Ca(2+) current, strongly influencing rhythmicity and triggering neurotransmitter release throughout the central nervous system. Fitting with such stature among Ca(2+) entry pathways, CaV 2.1 is itself feedback regulated by intracellular Ca(2+) , acting through calmodulin to facilitate channel opening. The precise neurophysiological role of this calcium-dependent facilitation (CDF) remains uncertain, however, in large measure because the very magnitude, Ca(2+) dependence and kinetics of CDF have resisted quantification by conventional means. Here, we utilize the photo-uncaging of Ca(2+) with CaV 2.1 channels fluxing Li(+) currents, so that voltage-dependent activation of channel gating is no longer conflated with Ca(2+) entry, and CDF is then driven solely by light-induced increases in Ca(2+) . By using this strategy, we now find that CDF can be unexpectedly large, enhancing currents by as much as twofold at physiological voltages. CDF is steeply Ca(2+) dependent, with a Hill coefficient of approximately two, a half-maximal effect reached by nearly 500 nm Ca(2+) , and Ca(2+) on/off kinetics in the order of milliseconds to tens of milliseconds. These properties were established for both native P-type currents in cerebellar Purkinje neurons, as well as their recombinant channel counterparts under heterologous expression. Such features suggest that CDF of CaV 2.1 channels may substantially enhance the regularity of rhythmic firing in cerebellar Purkinje neurons, where regularity is believed crucial for motor coordination. In addition, this degree of extensive CDF would be poised to exert large order-of-magnitude effects on short-term synaptic plasticity via rapid modulation of presynaptic Ca(2+) entry.
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Affiliation(s)
- Shin-Rong Lee
- Calcium Signals Laboratory, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.,Departments of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Paul J Adams
- Department of Biology, Kwantlen Polytechnic University, Surrey, BC, Canada, V3W 2M8
| | - David T Yue
- Calcium Signals Laboratory, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.,Departments of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.,Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.,Center for Cell Dynamics, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
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Extremely Low Frequency Electromagnetic Fields Facilitate Vesicle Endocytosis by Increasing Presynaptic Calcium Channel Expression at a Central Synapse. Sci Rep 2016; 6:21774. [PMID: 26887777 PMCID: PMC4757866 DOI: 10.1038/srep21774] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Accepted: 02/01/2016] [Indexed: 12/24/2022] Open
Abstract
Accumulating evidence suggests significant biological effects caused by extremely low frequency electromagnetic fields (ELF-EMF). Although exo-endocytosis plays crucial physical and biological roles in neuronal communication, studies on how ELF-EMF regulates this process are scarce. By directly measuring calcium currents and membrane capacitance at a large mammalian central nervous synapse, the calyx of Held, we report for the first time that ELF-EMF critically affects synaptic transmission and plasticity. Exposure to ELF-EMF for 8 to 10 days dramatically increases the calcium influx upon stimulation and facilitates all forms of vesicle endocytosis, including slow and rapid endocytosis, endocytosis overshoot and bulk endocytosis, but does not affect the RRP size and exocytosis. Exposure to ELF-EMF also potentiates PTP, a form of short-term plasticity, increasing its peak amplitude without impacting its time course. We further investigated the underlying mechanisms and found that calcium channel expression, including the P/Q, N, and R subtypes, at the presynaptic nerve terminal was enhanced, accounting for the increased calcium influx upon stimulation. Thus, we conclude that exposure to ELF-EMF facilitates vesicle endocytosis and synaptic plasticity in a calcium-dependent manner by increasing calcium channel expression at the nerve terminal.
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15
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Calcium sensor regulation of the CaV2.1 Ca2+ channel contributes to short-term synaptic plasticity in hippocampal neurons. Proc Natl Acad Sci U S A 2016; 113:1062-7. [PMID: 26755594 DOI: 10.1073/pnas.1524636113] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Short-term synaptic plasticity is induced by calcium (Ca(2+)) accumulating in presynaptic nerve terminals during repetitive action potentials. Regulation of voltage-gated CaV2.1 Ca(2+) channels by Ca(2+) sensor proteins induces facilitation of Ca(2+) currents and synaptic facilitation in cultured neurons expressing exogenous CaV2.1 channels. However, it is unknown whether this mechanism contributes to facilitation in native synapses. We introduced the IM-AA mutation into the IQ-like motif (IM) of the Ca(2+) sensor binding site. This mutation does not alter voltage dependence or kinetics of CaV2.1 currents, or frequency or amplitude of spontaneous miniature excitatory postsynaptic currents (mEPSCs); however, synaptic facilitation is completely blocked in excitatory glutamatergic synapses in hippocampal autaptic cultures. In acutely prepared hippocampal slices, frequency and amplitude of mEPSCs and amplitudes of evoked EPSCs are unaltered. In contrast, short-term synaptic facilitation in response to paired stimuli is reduced by ∼ 50%. In the presence of EGTA-AM to prevent global increases in free Ca(2+), the IM-AA mutation completely blocks short-term synaptic facilitation, indicating that synaptic facilitation by brief, local increases in Ca(2+) is dependent upon regulation of CaV2.1 channels by Ca(2+) sensor proteins. In response to trains of action potentials, synaptic facilitation is reduced in IM-AA synapses in initial stimuli, consistent with results of paired-pulse experiments; however, synaptic depression is also delayed, resulting in sustained increases in amplitudes of later EPSCs during trains of 10 stimuli at 10-20 Hz. Evidently, regulation of CaV2.1 channels by CaS proteins is required for normal short-term plasticity and normal encoding of information in native hippocampal synapses.
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16
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Soong TW, Mori MX. Post-transcriptional modifications and "Calmodulation" of voltage-gated calcium channel function: Reflections by two collaborators of David T Yue. Channels (Austin) 2015; 10:14-9. [PMID: 26054929 DOI: 10.1080/19336950.2015.1051271] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
This review article is written to specially pay tribute to David T. Yue who was an outstanding human being and an excellent scientist who exuded passion and creativity. He exemplified an inter-disciplinary scientist who was able to cross scientific boundaries effortlessly in order to provide amazing understanding on how calcium channels work. This article provides a glimpse of some of the research the authors have the privilege to collaborate with David and it attempts to provide the thinking behind some of the research done. In a wider context, we highlight that calcium channel function could be exquisitely modulated by interaction with a tethered calmodulin. Post-transcriptional modifications such as alternative splicing and RNA editing further influence the Ca(2+)-CaM mediated processes such as calcium dependent inhibition and/or facilitation. Besides modifications of electrophysiological and pharmacological properties, protein interactions with the channels could also be influenced in a splice-variant dependent manner.
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Affiliation(s)
- Tuck Wah Soong
- a Department of Physiology ; Yong Loo Lin School of Medicine; National University of Singapore ; Singapore.,b NUS Graduate School for Integrative Science and Engineering, and Neurobiology/Aging Program ; Singapore.,c National Neuroscience Institute ; Singapore
| | - Masayuki X Mori
- d Kyoto University Department of Synthetic Chemistry and Biological Chemistry ; Graduate School of Engineering, Kyoto University ; Kyoto , Japan
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17
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Kim J, Kita H. Posttetanic enhancement of striato-pallidal synaptic transmission. J Neurophysiol 2015; 114:447-54. [PMID: 25995348 DOI: 10.1152/jn.00241.2015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 05/17/2015] [Indexed: 11/22/2022] Open
Abstract
The striato (Str)-globus pallidus external segment (GPe) projection plays major roles in the control of neuronal activity in the basal ganglia under both normal and pathological conditions. The present study used rat brain slice preparations to characterize the enhancement of Str-GPe synapses observed after repetitive conditioning stimuli (CS) of Str with the whole cell patch-clamp recording technique. The results show that 1) the Str-GPe synapses have a posttetanic enhancement (PTE) mechanism, which is considered to be a combination of an augmentation and a posttetanic potentiation; 2) the degree of PTE observed in GPe neurons had a wide range and was positively correlated with a wide range of paired-pulse ratios assessed before application of CS; 3) a wide range of CS, from frequencies as low as 2 Hz with as few as 5 pulses to as high as 100 Hz with 100 pulses, could induce PTE; 4) the decay time constant of PTE was dependent on the strength of CS and was prolonged greatly, up to 120 s, when strong CS were applied; and 5) the level of postsynaptic Cl(-) became a limiting factor for the degree of PTE when strong CS were applied. These results imply that Str-GPe synapses transmit inhibitions in a nonlinear activity-weighted manner, which may be suited for scaling timing and force of repeated or sequential body movements. Other possible factors controlling the induction of PTE and functional implications are also discussed.
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Affiliation(s)
- Juhyon Kim
- Department of Anatomy and Neurobiology, College of Medicine, The University of Tennessee Health Science Center, Memphis, Tennessee
| | - Hitoshi Kita
- Department of Anatomy and Neurobiology, College of Medicine, The University of Tennessee Health Science Center, Memphis, Tennessee
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Porto FHDG, Fox AM, Tusch ES, Sorond F, Mohammed AH, Daffner KR. In vivo evidence for neuroplasticity in older adults. Brain Res Bull 2015; 114:56-61. [PMID: 25857946 PMCID: PMC4666311 DOI: 10.1016/j.brainresbull.2015.03.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Revised: 03/27/2015] [Accepted: 03/28/2015] [Indexed: 12/11/2022]
Abstract
Neuroplasticity can be conceptualized as an intrinsic property of the brain that enables modification of function and structure in response to environmental demands. Neuroplastic strengthening of synapses is believed to serve as a critical mechanism underlying learning, memory, and other cognitive functions. Ex vivo work investigating neuroplasticity has been done on hippocampal slices using high frequency stimulation. However, in vivo neuroplasticity in humans has been difficult to demonstrate. Recently, a long-term potentiation-like phenomenon, a form of neuroplastic change, was identified in young adults by differences in visual evoked potentials (VEPs) that were measured before and after tetanic visual stimulation (TVS). The current study investigated whether neuroplastic changes in the visual pathway can persist in older adults. Seventeen healthy subjects, 65 years and older, were recruited from the community. Subjects had a mean age of 77.4 years, mean education of 17 years, mean MMSE of 29.1, and demonstrated normal performance on neuropsychological tests. 1Hz checkerboard stimulation, presented randomly to the right or left visual hemi-field, was followed by 2min of 9Hz stimulation (TVS) to one hemi-field. After 2min of rest, 1Hz stimulation was repeated. Temporospatial principal component analysis was used to identify the N1b component of the VEPs, at lateral occipital locations, in response to 1Hz stimulation pre- and post-TVS. Results showed that the amplitude of factors representing the early and late N1b component was substantially larger after tetanic stimulation. These findings indicate that high frequency visual stimulation can enhance the N1b in cognitively high functioning old adults, suggesting that neuroplastic changes in visual pathways can continue into late life. Future studies are needed to determine the extent to which this marker of neuroplasticity is sustained over a longer period of time, and is influenced by age, cognitive status, and neurodegenerative disease.
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Affiliation(s)
- Fábio Henrique de Gobbi Porto
- Laboratory of Healthy Cognitive Aging, Division of Cognitive and Behavioral Neurology and Center for Brain/Mind Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
| | - Anne Murphy Fox
- Laboratory of Healthy Cognitive Aging, Division of Cognitive and Behavioral Neurology and Center for Brain/Mind Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
| | - Erich S Tusch
- Laboratory of Healthy Cognitive Aging, Division of Cognitive and Behavioral Neurology and Center for Brain/Mind Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
| | - Farzaneh Sorond
- Division of Stroke and Cerebrovascular Disease, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
| | - Abdul H Mohammed
- Department of Psychology, Linnaeus University, Växjö, Sweden; Center for Alzheimer Research, Department of NVS, Karolinska Institutet, Huddinge, Sweden.
| | - Kirk R Daffner
- Laboratory of Healthy Cognitive Aging, Division of Cognitive and Behavioral Neurology and Center for Brain/Mind Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
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19
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Synaptic plasticity in the auditory system: a review. Cell Tissue Res 2015; 361:177-213. [PMID: 25896885 DOI: 10.1007/s00441-015-2176-x] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 03/18/2015] [Indexed: 01/19/2023]
Abstract
Synaptic transmission via chemical synapses is dynamic, i.e., the strength of postsynaptic responses may change considerably in response to repeated synaptic activation. Synaptic strength is increased during facilitation, augmentation and potentiation, whereas a decrease in synaptic strength is characteristic for depression and attenuation. This review attempts to discuss the literature on short-term and long-term synaptic plasticity in the auditory brainstem of mammals and birds. One hallmark of the auditory system, particularly the inner ear and lower brainstem stations, is information transfer through neurons that fire action potentials at very high frequency, thereby activating synapses >500 times per second. Some auditory synapses display morphological specializations of the presynaptic terminals, e.g., calyceal extensions, whereas other auditory synapses do not. The review focuses on short-term depression and short-term facilitation, i.e., plastic changes with durations in the millisecond range. Other types of short-term synaptic plasticity, e.g., posttetanic potentiation and depolarization-induced suppression of excitation, will be discussed much more briefly. The same holds true for subtypes of long-term plasticity, like prolonged depolarizations and spike-time-dependent plasticity. We also address forms of plasticity in the auditory brainstem that do not comprise synaptic plasticity in a strict sense, namely short-term suppression, paired tone facilitation, short-term adaptation, synaptic adaptation and neural adaptation. Finally, we perform a meta-analysis of 61 studies in which short-term depression (STD) in the auditory system is opposed to short-term depression at non-auditory synapses in order to compare high-frequency neurons with those that fire action potentials at a lower rate. This meta-analysis reveals considerably less STD in most auditory synapses than in non-auditory ones, enabling reliable, failure-free synaptic transmission even at frequencies >100 Hz. Surprisingly, the calyx of Held, arguably the best-investigated synapse in the central nervous system, depresses most robustly. It will be exciting to reveal the molecular mechanisms that set high-fidelity synapses apart from other synapses that function much less reliably.
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A three-pool model dissecting readily releasable pool replenishment at the calyx of held. Sci Rep 2015; 5:9517. [PMID: 25825223 PMCID: PMC4379469 DOI: 10.1038/srep09517] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 03/06/2015] [Indexed: 12/20/2022] Open
Abstract
Although vesicle replenishment is critical in maintaining exo-endocytosis recycling, the underlying mechanisms are not well understood. Previous studies have shown that both rapid and slow endocytosis recycle into a very large recycling pool instead of within the readily releasable pool (RRP), and the time course of RRP replenishment is slowed down by more intense stimulation. This finding contradicts the calcium/calmodulin-dependence of RRP replenishment. Here we address this issue and report a three-pool model for RRP replenishment at a central synapse. Both rapid and slow endocytosis provide vesicles to a large reserve pool (RP) ~42.3 times the RRP size. When moving from the RP to the RRP, vesicles entered an intermediate pool (IP) ~2.7 times the RRP size with slow RP-IP kinetics and fast IP-RRP kinetics, which was responsible for the well-established slow and rapid components of RRP replenishment. Depletion of the IP caused the slower RRP replenishment observed after intense stimulation. These results establish, for the first time, a realistic cycling model with all parameters measured, revealing the contribution of each cycling step in synaptic transmission. The results call for modification of the current view of the vesicle recycling steps and their roles.
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Toda T, Ishida K, Kiyama H, Yamashita T, Lee S. Down-regulation of KCC2 expression and phosphorylation in motoneurons, and increases the number of in primary afferent projections to motoneurons in mice with post-stroke spasticity. PLoS One 2014; 9:e114328. [PMID: 25546454 PMCID: PMC4278744 DOI: 10.1371/journal.pone.0114328] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 11/06/2014] [Indexed: 12/31/2022] Open
Abstract
Spasticity obstructs motor function recovery post-stroke, and has been reported to occur in spinal cord injury and electrophysiological studies. The purpose of the present study was to assess spinal cord circuit spasticity in post-stroke mice. At 3, 7, 21, and 42 d after photothrombotic ischemic cortical injury in C57BL/6J mice, we observed decreased rate-dependent depression (RDD) of the Hoffmann reflex (H reflex) in the affected forelimb of mice compared with the limbs of sham mice and the non-affected forelimb. This finding suggests a hyper-excitable stretch reflex in the affected forelimb. We then performed immunohistochemical and western blot analyses to examine the expression of the potassium-chloride cotransporter 2 (KCC2) and phosphorylation of the KCC2 serine residue, 940 (S940), since this is the main chloride extruder that affects neuronal excitability. We also performed immunohistochemical analyses on the number of vesicular glutamate transporter 1 (vGluT1)-positive boutons to count the number of Ia afferent fibers that connect to motoneurons. Western bolts revealed that, compared with sham mice, experimental mice had significantly reduced KCC2 expression at 7 d post-stroke, and dephosphorylated S940 at 3 and 7 d post-stroke in motoneuron plasma membranes. We also observed a lower density of KCC2-positive areas in the plasma membrane of motoneurons at 3 and 7 d post-stroke. However, western blot and immunohistochemical analyses revealed that there were no differences between groups 21 and 42 d post-stroke, respectively. In addition, at 7 and 42 d post-stroke, experimental mice exhibited a significant increase in vGluT1 boutons compared with sham mice. Our findings suggest that both the down-regulation of KCC2 and increases in Ia afferent fibers are involved in post-stroke spasticity.
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Affiliation(s)
- Takuya Toda
- Department of Physical and Occupational Therapy, Graduate School of Medicine, Nagoya University, Nagoya, Japan
| | - Kazuto Ishida
- Department of Physical and Occupational Therapy, Graduate School of Medicine, Nagoya University, Nagoya, Japan
| | - Hiroshi Kiyama
- Department of Functional Anatomy and Neuroscience, Graduate School of Medicine, Nagoya University, Nagoya, Japan
| | - Toshihide Yamashita
- Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Sachiko Lee
- Department of Physical and Occupational Therapy, Graduate School of Medicine, Nagoya University, Nagoya, Japan
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22
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Deng PY, Klyachko VA. The diverse functions of short-term plasticity components in synaptic computations. Commun Integr Biol 2014. [DOI: 10.4161/cib.15870] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Yang YM, Wang W, Fedchyshyn MJ, Zhou Z, Ding J, Wang LY. Enhancing the fidelity of neurotransmission by activity-dependent facilitation of presynaptic potassium currents. Nat Commun 2014; 5:4564. [PMID: 25078759 PMCID: PMC4503407 DOI: 10.1038/ncomms5564] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2014] [Accepted: 07/01/2014] [Indexed: 12/02/2022] Open
Abstract
Neurons convey information in bursts of spikes across chemical synapses where the fidelity of information transfer critically depends on synaptic input-output relationship. With a limited number of synaptic vesicles (SVs) in the readily-releasable pool (RRP), how nerve terminals sustain transmitter release during intense activity remains poorly understood. Here we report that presynaptic K+ currents evoked by spikes facilitate in a Ca2+-independent but frequency- and voltage-dependent manner. Experimental evidence and computer simulations demonstrate this facilitation originates from dynamic transition of intermediate gating states of voltage-gated K+ channels (Kvs), and specifically attenuates spike amplitude and inter-spike potential during high-frequency firing. Single or paired recordings from a mammalian central synapse further reveal that facilitation of Kvs constrains presynaptic Ca2+ influx, thereby efficiently allocating SVs in the RRP to drive postsynaptic spiking at high rates. We conclude that presynaptic Kv facilitation imparts neurons with a powerful control of transmitter release to dynamically support high-fidelity neurotransmission.
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Affiliation(s)
- Yi-Mei Yang
- 1] Program in Neurosciences and Mental Health, SickKids Research Institute, Toronto, Ontario, Canada M5G 1X8 [2] Department of Physiology, University of Toronto, Toronto, Ontario, Canada M5S 1A8 [3]
| | - Wei Wang
- 1] Key Laboratory of Molecular Biophysics of the Ministry of Education, Huazhong University of Science and Technology, Wuhan 430074, China [2] Department of Medical Engineering, the 180th Hospital of PLA, Quanzhou 362000, China [3]
| | - Michael J Fedchyshyn
- 1] Program in Neurosciences and Mental Health, SickKids Research Institute, Toronto, Ontario, Canada M5G 1X8 [2] Department of Physiology, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Zhuan Zhou
- Institute of Molecular Medicine &PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Jiuping Ding
- Key Laboratory of Molecular Biophysics of the Ministry of Education, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Lu-Yang Wang
- 1] Program in Neurosciences and Mental Health, SickKids Research Institute, Toronto, Ontario, Canada M5G 1X8 [2] Department of Physiology, University of Toronto, Toronto, Ontario, Canada M5S 1A8
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Acute and long-term effects of noise exposure on the neuronal spontaneous activity in cochlear nucleus and inferior colliculus brain slices. BIOMED RESEARCH INTERNATIONAL 2014; 2014:909260. [PMID: 25110707 PMCID: PMC4119618 DOI: 10.1155/2014/909260] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 06/20/2014] [Accepted: 06/20/2014] [Indexed: 11/17/2022]
Abstract
Noise exposure leads to an immediate hearing loss and is followed by a long-lasting permanent threshold shift, accompanied by changes of cellular properties within the central auditory pathway. Electrophysiological recordings have demonstrated an upregulation of spontaneous neuronal activity. It is still discussed if the observed effects are related to changes of peripheral input or evoked within the central auditory system. The present study should describe the intrinsic temporal patterns of single-unit activity upon noise-induced hearing loss of the dorsal and ventral cochlear nucleus (DCN and VCN) and the inferior colliculus (IC) in adult mouse brain slices. Recordings showed a slight, but significant, elevation in spontaneous firing rates in DCN and VCN immediately after noise trauma, whereas no differences were found in IC. One week postexposure, neuronal responses remained unchanged compared to controls. At 14 days after noise trauma, intrinsic long-term hyperactivity in brain slices of the DCN and the IC was detected for the first time. Therefore, increase in spontaneous activity seems to develop within the period of two weeks, but not before day 7. The results give insight into the complex temporal neurophysiological alterations after noise trauma, leading to a better understanding of central mechanisms in noise-induced hearing loss.
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Kudryashova IV. Molecular mechanisms of short-term plasticity as a basis of frequency coding: The role of proteolytic systems. NEUROCHEM J+ 2014. [DOI: 10.1134/s1819712414010097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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26
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Soluble pathological tau in the entorhinal cortex leads to presynaptic deficits in an early Alzheimer's disease model. Acta Neuropathol 2014; 127:257-70. [PMID: 24271788 DOI: 10.1007/s00401-013-1215-5] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Revised: 10/28/2013] [Accepted: 11/09/2013] [Indexed: 10/26/2022]
Abstract
Neurofibrillary tangles (NFTs), a hallmark of Alzheimer's disease, are intracellular silver and thioflavin S-staining aggregates that emerge from earlier accumulation of phospho-tau in the soma. Whether soluble misfolded but nonfibrillar tau disrupts neuronal function is unclear. Here we investigate if soluble pathological tau, specifically directed to the entorhinal cortex (EC), can cause behavioral or synaptic deficits. We studied rTgTauEC transgenic mice, in which P301L mutant human tau overexpressed primarily in the EC leads to the development of tau pathology, but only rare NFT at 16 months of age. We show that the early tau lesions are associated with nearly normal performance in contextual fear conditioning, a hippocampal-related behavior task, but more robust changes in neuronal system activation as marked by Arc induction and clear electrophysiological defects in perforant pathway synaptic plasticity. Electrophysiological changes were likely due to a presynaptic deficit and changes in probability of neurotransmitter release. The data presented here support the hypothesis that misfolded and hyperphosphorylated tau can impair neuronal function within the entorhinal-hippocampal network, even prior to frank NFT formation and overt neurodegeneration.
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27
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Bernardi RE, Uhrig S, Spanagel R, Hansson AC. Transcriptional regulation of L-type calcium channel subtypes Cav1.2 and Cav1.3 by nicotine and their potential role in nicotine sensitization. Nicotine Tob Res 2014; 16:774-85. [PMID: 24470632 DOI: 10.1093/ntr/ntt274] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
INTRODUCTION L-type calcium channel (LTCC) activity in the brain is mediated by 2 subtypes, Ca(v)1.2 and Ca(v)1.3. The individual contributions of these LTCC subtypes to the long-term pharmacological and behavioral effects of nicotine are unknown. METHODS Using quantitative in situ hybridization, we examined expression levels of Ca(v)1.2 and Ca(v)1.3 in forebrain regions of mice treated with nicotine (0.175 mg/kg) or saline for 1 or 14 days and sacrificed 24 hr or 7 days following the last injection. Additionally, we treated mice with nicotine for 14 days and then administered the nonspecific LTCC antagonist nifedipine twice daily during a 7-day abstinence period prior to testing for nicotine sensitization to determine the effect of LTCC blockade on sensitization. RESULTS Ca(v)1.2 mRNA was unaffected 24 hr following a single nicotine exposure, whereas Ca(v)1.3 mRNA was upregulated in several brain regions. Following 14 days of nicotine treatment and 24 hr of abstinence, Ca(v)1.2 mRNA was downregulated throughout the areas examined, whereas Ca(v)1.3 mRNA had mostly returned to control values. Following 7 days of abstinence, a strong upregulation of Ca(v)1.2 transcripts was observed, whereas Ca(v)1.3 mRNA was largely unaffected. In our sensitization study, nifedipine administered during nicotine abstinence impaired subsequent nicotine sensitization. CONCLUSIONS Our data suggest a differential involvement of Ca(v)1.2 and Ca(v)1.3 in nicotine-related processes. Ca(v)1.3 seems to be involved primarily during early exposure to nicotine. Ca(v)1.2 appears to play a role in the long-term molecular and behavioral changes that occur following chronic nicotine and abstinence. Nifedipine may counteract those nicotine-induced alterations in LTCC activity to impair nicotine sensitization.
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Affiliation(s)
- Rick E Bernardi
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim /University of Heidelberg, Mannheim, Germany
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Lee S, Toda T, Kiyama H, Yamashita T. Weakened rate-dependent depression of Hoffmann's reflex and increased motoneuron hyperactivity after motor cortical infarction in mice. Cell Death Dis 2014; 5:e1007. [PMID: 24434515 PMCID: PMC4040693 DOI: 10.1038/cddis.2013.544] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Revised: 12/04/2013] [Accepted: 12/09/2013] [Indexed: 12/02/2022]
Abstract
Abnormal reflexes associated with spasticity are considered a major determinant of motor impairments occurring after stroke; however, the mechanisms underlying post-stroke spasticity remain unclear. This may be because of the lack of suitable rodent models for studying spasticity after cortical injuries. Thus, the purpose of the present study was to establish an appropriate post-stroke spasticity mouse model. We induced photothrombotic injury in the rostral and caudal forelimb motor areas of mice and used the rate-dependent depression (RDD) of Hoffmann's reflex (H-reflex) as an indicator of spastic symptoms. To detect motoneuron excitability, we examined c-fos mRNA levels and c-Fos immunoreactivity in affected motoneurons using quantitative real-time reverse transcription PCR and immunohistochemical analysis, respectively. To confirm the validity of our model, we confirmed the effect of the anti-spasticity drug baclofen on H-reflex RDDs 1 week post stroke. We found that 3 days after stroke, the RDD was significantly weakened in the affected muscles of stroke mice compared with sham-operated mice, and this was observed for 8 weeks. The c-fos mRNA levels in affected motoneurons were significantly increased in stroke mice compared with sham-operated mice. Immunohistochemical analysis revealed a significant increase in the number of c-Fos-positive motoneurons in stroke mice compared with sham-operated mice at 1, 2, 4, and 8 weeks after stroke; however, the number of c-Fos-positive motoneurons on both sides of the brain gradually decreased over time. Baclofen treatment resulted in recovery of the weakened RDD at 1 week post stroke. Our findings suggest that this is a viable animal model of post-stroke spasticity.
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Affiliation(s)
- S Lee
- Department of Rehabilitation Sciences, Graduate School of Medicine, Nagoya University, 1-1-20 Daiko-minami Higashi-ku, Nagoya-shi, Aichi, Japan
| | - T Toda
- Department of Rehabilitation Sciences, Graduate School of Medicine, Nagoya University, 1-1-20 Daiko-minami Higashi-ku, Nagoya-shi, Aichi, Japan
| | - H Kiyama
- Department of Functional Anatomy and Neuroscience, Graduate School of Medicine, Nagoya University, 65 Tsurumai-tyou Shouwa-ku, Nagoya-shi, Aichi, Japan
| | - T Yamashita
- Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita-shi, Osaka, Japan
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Atlas D. The Voltage-Gated Calcium Channel Functions as the Molecular Switch of Synaptic Transmission. Annu Rev Biochem 2013; 82:607-35. [DOI: 10.1146/annurev-biochem-080411-121438] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Daphne Atlas
- Department of Biological Chemistry, Institute of Life Sciences, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel;
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30
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Egawa R, Hososhima S, Hou X, Katow H, Ishizuka T, Nakamura H, Yawo H. Optogenetic probing and manipulation of the calyx-type presynaptic terminal in the embryonic chick ciliary ganglion. PLoS One 2013; 8:e59179. [PMID: 23555628 PMCID: PMC3605445 DOI: 10.1371/journal.pone.0059179] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Accepted: 02/12/2013] [Indexed: 11/23/2022] Open
Abstract
The calyx-type synapse of chick ciliary ganglion (CG) has been intensively studied for decades as a model system for the synaptic development, morphology and physiology. Despite recent advances in optogenetics probing and/or manipulation of the elementary steps of the transmitter release such as membrane depolarization and Ca2+ elevation, the current gene-manipulating methods are not suitable for targeting specifically the calyx-type presynaptic terminals. Here, we evaluated a method for manipulating the molecular and functional organization of the presynaptic terminals of this model synapse. We transfected progenitors of the Edinger-Westphal (EW) nucleus neurons with an EGFP expression vector by in ovo electroporation at embryonic day 2 (E2) and examined the CG at E8–14. We found that dozens of the calyx-type presynaptic terminals and axons were selectively labeled with EGFP fluorescence. When a Brainbow construct containing the membrane-tethered fluorescent proteins m-CFP, m-YFP and m-RFP, was introduced together with a Cre expression construct, the color coding of each presynaptic axon facilitated discrimination among inter-tangled projections, particularly during the developmental re-organization period of synaptic connections. With the simultaneous expression of one of the chimeric variants of channelrhodopsins, channelrhodopsin-fast receiver (ChRFR), and R-GECO1, a red-shifted fluorescent Ca2+-sensor, the Ca2+ elevation was optically measured under direct photostimulation of the presynaptic terminal. Although this optically evoked Ca2+ elevation was mostly dependent on the action potential, a significant component remained even in the absence of extracellular Ca2+. It is suggested that the photo-activation of ChRFR facilitated the release of Ca2+ from intracellular Ca2+ stores directly or indirectly. The above system, by facilitating the molecular study of the calyx-type presynaptic terminal, would provide an experimental platform for unveiling the molecular mechanisms underlying the morphology, physiology and development of synapses.
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Affiliation(s)
- Ryo Egawa
- Department of Developmental Biology and Neuroscience, Tohoku University Graduate School of Life Sciences, Sendai, Japan
- Japan Science and Technology Agency (JST), Core Research of Evolutional Science & Technology (CREST), Tokyo, Japan
- Tohoku University Institute for International Advanced Research and Education, Sendai, Japan
| | - Shoko Hososhima
- Department of Developmental Biology and Neuroscience, Tohoku University Graduate School of Life Sciences, Sendai, Japan
- Japan Science and Technology Agency (JST), Core Research of Evolutional Science & Technology (CREST), Tokyo, Japan
| | - Xubin Hou
- Department of Developmental Biology and Neuroscience, Tohoku University Graduate School of Life Sciences, Sendai, Japan
- Department of Molecular Neurobiology, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan
| | - Hidetaka Katow
- Department of Developmental Biology and Neuroscience, Tohoku University Graduate School of Life Sciences, Sendai, Japan
- Japan Science and Technology Agency (JST), Core Research of Evolutional Science & Technology (CREST), Tokyo, Japan
| | - Toru Ishizuka
- Department of Developmental Biology and Neuroscience, Tohoku University Graduate School of Life Sciences, Sendai, Japan
- Japan Science and Technology Agency (JST), Core Research of Evolutional Science & Technology (CREST), Tokyo, Japan
| | - Harukazu Nakamura
- Department of Developmental Biology and Neuroscience, Tohoku University Graduate School of Life Sciences, Sendai, Japan
- Department of Molecular Neurobiology, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan
| | - Hiromu Yawo
- Department of Developmental Biology and Neuroscience, Tohoku University Graduate School of Life Sciences, Sendai, Japan
- Japan Science and Technology Agency (JST), Core Research of Evolutional Science & Technology (CREST), Tokyo, Japan
- Center for Neuroscience, Tohoku University Graduate School of Medicine, Sendai, Japan
- * E-mail:
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31
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Kim J, Kita H. Short-term plasticity shapes activity pattern-dependent striato-pallidal synaptic transmission. J Neurophysiol 2012. [PMID: 23197459 DOI: 10.1152/jn.00459.2012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The cortico-striato (Str)-globus pallidus external segment (GPe) projection plays major roles in the control of neuronal activity in the basal ganglia under both normal and pathological conditions. The present study used rat brain-slice preparations to address our hypothesis that the gain of this disynaptic projection is dynamically controlled by activations of short-term plasticity mechanisms of Str-GPe synapses. The Str-GPe projection neurons fire with very different frequency and firing patterns in vivo depending on the condition of the animal. The results show that the Str-GPe synapses have very strong short-term enhancement mechanisms and that repetitive burst activation of the Str-GPe synapses, which mimic oscillatory burst firing of Str neurons, can sustain enhanced states of synaptic transmission for tens of seconds. The results reveal that the short-term enhancement of Str-GPe synapses contributes to the generation of pauses in the firing of GPe neurons and that signal transfer function in the Str-GPe projection is highly dependent on the firing pattern of Str neurons.
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Affiliation(s)
- Juhyon Kim
- Department of Anatomy and Neurobiology, College of Medicine, The University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
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32
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Kvarta MD, Harris-Warrick RM, Johnson BR. Neuromodulator-evoked synaptic metaplasticity within a central pattern generator network. J Neurophysiol 2012; 108:2846-56. [PMID: 22933725 PMCID: PMC3545119 DOI: 10.1152/jn.00586.2012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Accepted: 08/27/2012] [Indexed: 12/18/2022] Open
Abstract
Synapses show short-term activity-dependent dynamics that alter the strength of neuronal interactions. This synaptic plasticity can be tuned by neuromodulation as a form of metaplasticity. We examined neuromodulator-induced metaplasticity at a graded chemical synapse in a model central pattern generator (CPG), the pyloric network of the spiny lobster stomatogastric ganglion. Dopamine, serotonin, and octopamine each produce a unique motor pattern from the pyloric network, partially through their modulation of synaptic strength in the network. We characterized synaptic depression and its amine modulation at the graded synapse from the pyloric dilator neuron to the lateral pyloric neuron (PD→LP synapse), driving the PD neuron with both long square pulses and trains of realistic waveforms over a range of presynaptic voltages. We found that the three amines can differentially affect the amplitude of graded synaptic transmission independently of the synaptic dynamics. Low concentrations of dopamine had weak and variable effects on the strength of the graded inhibitory postsynaptic potentials (gIPSPs) but reliably accelerated the onset of synaptic depression and recovery from depression independently of gIPSP amplitude. Octopamine enhanced gIPSP amplitude but decreased the amount of synaptic depression; it slowed the onset of depression and accelerated its recovery during square pulse stimulation. Serotonin reduced gIPSP amplitude but increased the amount of synaptic depression and accelerated the onset of depression. These results suggest that amine-induced metaplasticity at graded chemical synapses can alter the parameters of synaptic dynamics in multiple and independent ways.
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Affiliation(s)
- Mark D Kvarta
- Department of Neurobiology and Behavior, S. G. Mudd Hall, Cornell University, Ithaca, New York 14853, USA
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33
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Macleod GT. Calcium imaging at the Drosophila larval neuromuscular junction. Cold Spring Harb Protoc 2012; 2012:758-66. [PMID: 22753609 DOI: 10.1101/pdb.top070078] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Calcium imaging uses optical imaging techniques to measure the concentration of free calcium [Ca(2+)] in live cells. It is a highly informative technique in neurobiology because Ca(2+) is involved in many neuronal signaling pathways and serves as the trigger for neurotransmitter release. The technique relies on loading Ca(2+) indicators into cells, measuring the quantity and/or wavelength of the photons emitted by the Ca(2+) indicator, and interpreting these data in terms of [Ca(2+)]. There are several possible methods for loading synthetic Ca(2+) indicators into subcellular compartments, for example, topical application of membrane-permeant Ca(2+) indicators, forward-filling of dextran conjugates, and direct injection. These techniques are applicable to calcium imaging at the Drosophila larval neuromuscular junction (NMJ), and are also readily adaptable to Drosophila embryo and adult preparations.
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34
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Oh M, Zhao S, Matveev V, Nadim F. Neuromodulatory changes in short-term synaptic dynamics may be mediated by two distinct mechanisms of presynaptic calcium entry. J Comput Neurosci 2012; 33:573-85. [PMID: 22710936 DOI: 10.1007/s10827-012-0402-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Revised: 05/09/2012] [Accepted: 05/23/2012] [Indexed: 10/28/2022]
Abstract
Although synaptic output is known to be modulated by changes in presynaptic calcium channels, additional pathways for calcium entry into the presynaptic terminal, such as non-selective channels, could contribute to modulation of short term synaptic dynamics. We address this issue using computational modeling. The neuropeptide proctolin modulates the inhibitory synapse from the lateral pyloric (LP) to the pyloric dilator (PD) neuron, two slow-wave bursting neurons in the pyloric network of the crab Cancer borealis. Proctolin enhances the strength of this synapse and also changes its dynamics. Whereas in control saline the synapse shows depression independent of the amplitude of the presynaptic LP signal, in proctolin, with high-amplitude presynaptic LP stimulation the synapse remains depressing while low-amplitude stimulation causes facilitation. We use simple calcium-dependent release models to explore two alternative mechanisms underlying these modulatory effects. In the first model, proctolin directly targets calcium channels by changing their activation kinetics which results in gradual accumulation of calcium with low-amplitude presynaptic stimulation, leading to facilitation. The second model uses the fact that proctolin is known to activate a non-specific cation current I ( MI ). In this model, we assume that the MI channels have some permeability to calcium, modeled to be a result of slow conformation change after binding calcium. This generates a gradual increase in calcium influx into the presynaptic terminals through the modulatory channel similar to that described in the first model. Each of these models can explain the modulation of the synapse by proctolin but with different consequences for network activity.
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Affiliation(s)
- Myongkeun Oh
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, NJ 07102, USA.
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35
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Xue L, Zhang Z, McNeil BD, Luo F, Wu XS, Sheng J, Shin W, Wu LG. Voltage-dependent calcium channels at the plasma membrane, but not vesicular channels, couple exocytosis to endocytosis. Cell Rep 2012; 1:632-8. [PMID: 22813738 DOI: 10.1016/j.celrep.2012.04.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 02/21/2012] [Accepted: 04/11/2012] [Indexed: 01/01/2023] Open
Abstract
Although calcium influx triggers endocytosis at many synapses and non-neuronal secretory cells, the identity of the calcium channel is unclear. The plasma membrane voltage-dependent calcium channel (VDCC) is a candidate, and it was recently proposed that exocytosis transiently inserts vesicular calcium channels at the plasma membrane, thus triggering endocytosis and coupling it to exocytosis, a mechanism suggested to be conserved from sea urchin to human. Here, we report that the vesicular membrane, when inserted into the plasma membrane upon exocytosis, does not generate a calcium current or calcium increase at a mammalian nerve terminal. Instead, VDCCs at the plasma membrane, including the P/Q-type, provide the calcium influx to trigger rapid and slow endocytosis and, thus, couple endocytosis to exocytosis. These findings call for reconsideration of the vesicular calcium channel hypothesis. They are likely to apply to many synapses and non-neuronal cells in which VDCCs control exocytosis, and exocytosis is coupled to endocytosis.
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Affiliation(s)
- Lei Xue
- National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
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36
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Cyclic ADP ribose-dependent Ca2+ release by group I metabotropic glutamate receptors in acutely dissociated rat hippocampal neurons. PLoS One 2011; 6:e26625. [PMID: 22028929 PMCID: PMC3197673 DOI: 10.1371/journal.pone.0026625] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Accepted: 09/29/2011] [Indexed: 11/19/2022] Open
Abstract
Group I metabotropic glutamate receptors (group I mGluRs; mGluR1 and mGluR5) exert diverse effects on neuronal and synaptic functions, many of which are regulated by intracellular Ca2+. In this study, we characterized the cellular mechanisms underlying Ca2+ mobilization induced by (RS)-3,5-dihydroxyphenylglycine (DHPG; a specific group I mGluR agonist) in the somata of acutely dissociated rat hippocampal neurons using microfluorometry. We found that DHPG activates mGluR5 to mobilize intracellular Ca2+ from ryanodine-sensitive stores via cyclic adenosine diphosphate ribose (cADPR), while the PLC/IP3 signaling pathway was not involved in Ca2+ mobilization. The application of glutamate, which depolarized the membrane potential by 28.5±4.9 mV (n = 4), led to transient Ca2+ mobilization by mGluR5 and Ca2+ influx through L-type Ca2+ channels. We found no evidence that mGluR5-mediated Ca2+ release and Ca2+ influx through L-type Ca2+ channels interact to generate supralinear Ca2+ transients. Our study provides novel insights into the mechanisms of intracellular Ca2+ mobilization by mGluR5 in the somata of hippocampal neurons.
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37
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Few AP, Nanou E, Scheuer T, Catterall WA. Molecular determinants of CaV2.1 channel regulation by calcium-binding protein-1. J Biol Chem 2011; 286:41917-41923. [PMID: 21965686 DOI: 10.1074/jbc.m111.292417] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Presynaptic Ca(V)2.1 channels, which conduct P/Q-type Ca(2+) currents, initiate synaptic transmission at most synapses in the central nervous system. Regulation of Ca(V)2.1 channels by CaM contributes significantly to short term facilitation and rapid depression of synaptic transmission. Short term synaptic plasticity is diverse in form and function at different synapses, yet CaM is ubiquitously expressed. Differential regulation of Ca(V)2.1 channels by CaM-like Ca(2+) sensor (CaS) proteins differentially affects short term synaptic facilitation and rapid synaptic depression in transfected sympathetic neuron synapses. Here, we define the molecular determinants for differential regulation of Ca(V)2.1 channels by the CaS protein calcium-binding protein-1 (CaBP1) by analysis of chimeras in which the unique structural domains of CaBP1 are inserted into CaM. Our results show that the N-terminal domain, including its myristoylation site, and the second EF-hand, which is inactive in Ca(2+) binding, are the key molecular determinants of differential regulation of Ca(V)2.1 channels by CaBP1. These findings give insight into the molecular code by which CaS proteins differentially regulate Ca(V)2.1 channel function and provide diversity of form and function of short term synaptic plasticity.
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Affiliation(s)
- Alexandra P Few
- Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington 98195-7280
| | - Evanthia Nanou
- Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington 98195-7280
| | - Todd Scheuer
- Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington 98195-7280
| | - William A Catterall
- Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington 98195-7280.
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38
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Deng PY, Klyachko VA. The diverse functions of short-term plasticity components in synaptic computations. Commun Integr Biol 2011; 4:543-8. [PMID: 22046457 DOI: 10.4161/cib.4.5.15870] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2011] [Accepted: 04/17/2011] [Indexed: 01/18/2023] Open
Abstract
Short-term plasticity (STP) comprises several rapid synaptic processes that operate on millisecond-to-minute timescales and modulate synaptic efficacy in an activity-dependent manner. Facilitation and augmentation are two major STP components in central synapses that work to enhance synaptic strength, while various forms of short-term depression work to decrease it. These multiple components of STP interact to perform a variety of synaptic computations. Using a modeling approach in excitatory hippocampal synapses, we recently described the contributions of individual STP components to synaptic operations. In this mini-review, we summarize the recent findings that revealed a wide palette of functions that STP components play in neural operations and discuss their roles in information processing, working memory and decision making.
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Affiliation(s)
- Pan-Yue Deng
- Department of Biomedical Engineering, Cell Biology and Physiology; Center for Investigation of Membrane Excitability Disorders; Washington University School of Medicine; St. Louis, MO USA
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39
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Short-term facilitation modulates size and timing of the synaptic response at the inner hair cell ribbon synapse. J Neurosci 2011; 31:7974-81. [PMID: 21632919 DOI: 10.1523/jneurosci.0604-11.2011] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Inner hair cells (IHCs) in the mammalian cochlea are able to continuously release neurotransmitter in the presence of constant stimuli. Nonetheless, strong synaptic depression is observed over the first few milliseconds of stimulation. This process most likely underlies adaptation in the auditory nerve. In the present study we demonstrate that under certain conditions of stimulation, facilitation can occur at the IHC ribbon synapse. Using simultaneous whole-cell, voltage-clamp recordings from IHCs and afferent fiber endings in excised postnatal rat cochleae, we stimulated IHCs with 2 ms long test depolarizations from a holding potential of -89 mV. Synaptic currents in afferent fibers occurred with high failure rates of ∼ 50%. However, when a pre-depolarization to values of -55 to -49 mV was implemented before the test pulse, success rates of the synaptic response increased to 100%, the strength of the synaptic response increased ∼ 2.8-fold, and synaptic latency was reduced by ∼ 50%. When calcium influx was minimized during pre-depolarization, none of these effects were found, suggesting that calcium influx during pre-depolarizations is required for synaptic conditioning. Similarly, in response to paired-pulse protocols, short term facilitation occurred. The response to the second stimulus increased up to ∼ 5-fold, and its latency was reduced by up to 35% compared to the response to the first stimulus. We propose that at the IHC resting membrane potential, the ribbon synapse operates in a constantly facilitated mode caused by Ca(2+) influx, optimizing the size and timing of the postsynaptic response in auditory nerve fibers.
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40
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Rudolph S, Overstreet-Wadiche L, Wadiche JI. Desynchronization of multivesicular release enhances Purkinje cell output. Neuron 2011; 70:991-1004. [PMID: 21658590 DOI: 10.1016/j.neuron.2011.03.029] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/30/2011] [Indexed: 10/18/2022]
Abstract
The release of neurotransmitter-filled vesicles after action potentials occurs with discrete time courses: submillisecond phasic release that can be desynchronized by activity followed by "delayed release" that persists for tens of milliseconds. Delayed release has a well-established role in synaptic integration, but it is not clear whether desynchronization of phasic release has physiological consequences. At the climbing fiber to Purkinje cell synapse, the synchronous fusion of multiple vesicles is critical for generating complex spikes. Here we show that stimulation at physiological frequencies drives the temporal dispersion of vesicles undergoing multivesicular release, resulting in a slowing of the EPSC on the millisecond timescale. Remarkably, these changes in EPSC kinetics robustly alter the Purkinje cell complex spike in a manner that promotes axonal propagation of individual spikelets. Thus, desynchronization of multivesicular release enhances the precise and efficient information transfer by complex spikes.
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Affiliation(s)
- Stephanie Rudolph
- Department of Biology, University of Freiburg, 79104 Freiburg, Germany
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41
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The number of components of enhancement contributing to short-term synaptic plasticity at the neuromuscular synapse during patterned nerve Stimulation progressively decreases as basal release probability is increased from low to normal levels by changing extracellular Ca2+. J Neurosci 2011; 31:7060-72. [PMID: 21562268 DOI: 10.1523/jneurosci.0392-11.2011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Presynaptic short-term plasticity (STP) dynamically modulates synaptic strength in a reversible manner on a timescale of milliseconds to minutes. For low basal vesicular release probability (prob0), four components of enhancement, F1 and F2 facilitation, augmentation (A), and potentiation (P), increase synaptic strength during repetitive nerve activity. For release rates that exceed the rate of replenishment of the readily releasable pool (RRP) of synaptic vesicles, depression of synaptic strength, observed as a rundown of postsynaptic potential amplitudes, can also develop. To understand the relationship between enhancement and depression at the frog (Rana pipiens) neuromuscular synapse, data obtained over a wide range of prob0 using patterned stimulation are analyzed with a hybrid model to reveal the components of STP. We find that F1, F2, A, P, and depletion of the RRP all contribute to STP during repetitive nerve activity at low prob0. As prob0 is increased by raising Ca(o)(2+) (extracellular Ca2+), specific components of enhancement no longer contribute, with first P, then A, and then F2 becoming undetectable, even though F1 continues to enhance release. For levels of prob0 that lead to appreciable depression, only F1 and depletion of the RRP contribute to STP during rundown, and for low stimulation rates, F2 can also contribute. These observations place prob0-dependent limitations on which components of enhancement contribute to STP and suggest some fundamental mechanistic differences among the components. The presented model can serve as a tool to readily characterize the components of STP over wide ranges of prob0.
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42
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Luk CC, Naruo H, Prince D, Hassan A, Doran SA, Goldberg JI, Syed NI. A novel form of presynaptic CaMKII-dependent short-term potentiation between Lymnaea neurons. Eur J Neurosci 2011; 34:569-77. [PMID: 21749498 DOI: 10.1111/j.1460-9568.2011.07784.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Short-term plasticity is thought to form the basis for working memory, the cellular mechanisms of which are the least understood in the nervous system. In this study, using in vitro reconstructed synapses between the identified Lymnaea neuron visceral dorsal 4 (VD4) and left pedal dorsal 1 (LPeD1), we demonstrate a novel form of short-term potentiation (STP) which is 'use'- but not time-dependent, unlike most previously defined forms of short-term synaptic plasticity. Using a triple-cell configuration we demonstrate for the first time that a single presynaptic neuron can reliably potentiate both inhibitory and excitatory synapses. We further demonstrate that, unlike previously described forms of STP, the synaptic potentiation between Lymnaea neurons does not involve postsynaptic receptor sensitization or presynaptic residual calcium. Finally, we provide evidence that STP at the VD4-LPeD1 synapse requires presynaptic calcium/calmodulin dependent kinase II (CaMKII). Taken together, our study identifies a novel form of STP which may provide the basis for both short- and long-term potentiation, in the absence of any protein synthesis-dependent steps, and involve CaMKII activity exclusively in the presynaptic cell.
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Affiliation(s)
- Collin C Luk
- Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Alberta, Canada
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43
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The possible impact of noise-induced Ca 2+ -dependent activity in the central auditory pathway: A manganese-enhanced MRI study. Neuroimage 2011; 57:190-197. [DOI: 10.1016/j.neuroimage.2011.04.022] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Revised: 04/05/2011] [Accepted: 04/08/2011] [Indexed: 11/19/2022] Open
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44
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Short-term forms of presynaptic plasticity. Curr Opin Neurobiol 2011; 21:269-74. [PMID: 21353526 DOI: 10.1016/j.conb.2011.02.003] [Citation(s) in RCA: 257] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2011] [Accepted: 02/01/2011] [Indexed: 01/27/2023]
Abstract
Synapses exhibit several forms of short-term plasticity that play a multitude of computational roles. Short-term depression suppresses neurotransmitter release for hundreds of milliseconds to tens of seconds; facilitation and post-tetanic potentiation lead to synaptic enhancement lasting hundreds of milliseconds to minutes. Recent advances have provided insight into the mechanisms underlying these forms of plasticity. Vesicle depletion, as well as inactivation of both release sites and calcium channels, contribute to synaptic depression. Mechanisms of short-term enhancement include calcium channel facilitation, local depletion of calcium buffers, increases in the probability of release downstream of calcium influx, altered vesicle pool properties, and increases in quantal size. Moreover, there is a growing appreciation of the heterogeneity of vesicles and release sites and how they can contribute to use-dependent plasticity.
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45
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Seabrooke S, Stewart BA. Synaptic transmission and plasticity are modulated by nonmuscle myosin II at the neuromuscular junction of Drosophila. J Neurophysiol 2011; 105:1966-76. [PMID: 21325687 DOI: 10.1152/jn.00718.2010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The synaptic vesicle population in a nerve terminal is traditionally divided into subpopulations according to physiological criteria; the readily releasable pool (RRP), the recycling pool, and the reserve pool. It is recognized that the RRP subserves synaptic transmission evoked by low-frequency neural activity and that the recycling and reserve populations are called on to supply vesicles as neural activity increases. Here we investigated the contribution of nonmuscle myosin II (NMMII) to synaptic transmission with emphasis on the role a motor protein could play in the supply of vesicles. We used Drosophila genetics to manipulate NMMII and assessed synaptic transmission at the larval neuromuscular junction. We observed a positive correlation between synaptic strength at low-frequency stimulation and NMMII expression: reducing NMMII reduced the evoked response, while increasing NMMII increased the evoked response. Further, we found that NMMII contributed to the spontaneous release of vesicles differentially from evoked release, suggesting differential contribution to these two release mechanisms. By measuring synaptic responses under conditions of differing external calcium concentration in saline, we found that NMMII is important for normal synaptic transmission under high-frequency stimulation. This research identifies diverse functions for NMMII in synaptic transmission and suggests that this motor protein is an active contributor to the physiology of synaptic vesicle recruitment.
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Affiliation(s)
- Sara Seabrooke
- Department of Biology, University of Toronto, Mississauga, Ontario, Canada
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Helmich RC, Siebner HR, Giffin N, Bestmann S, Rothwell JC, Bloem BR. The dynamic regulation of cortical excitability is altered in episodic ataxia type 2. ACTA ACUST UNITED AC 2011; 133:3519-29. [PMID: 21126994 DOI: 10.1093/brain/awq315] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Episodic ataxia type 2 and familial hemiplegic migraine are two rare hereditary disorders that are linked to dysfunctional ion channels and are characterized clinically by paroxysmal neurological symptoms. Impaired regulation of cerebral excitability is thought to play a role in the occurrence of these paroxysms, but the underlying mechanisms are poorly understood. Normal ion channels are crucial for coordinating neuronal firing in response to facilitatory input. Thus, we hypothesized that channel dysfunction in episodic ataxia type 2 and familial hemiplegic migraine may impair the ability to adjust cerebral excitability after facilitatory events. We tested this hypothesis in patients with episodic ataxia type 2 (n = 6), patients with familial hemiplegic migraine (n = 7) and healthy controls (n = 13). All subjects received a high-frequency burst (10 pulses at 20 Hz) of transcranial magnetic stimulation to transiently increase the excitability of the motor cortex. Acute burst-induced excitability changes were probed at 50, 250, 500 and 1000 ms after the end of the burst. This was done using single-pulse transcranial magnetic stimulation to assess corticospinal excitability, and paired-pulse transcranial magnetic stimulation at an interstimulus interval of 2 and 10 ms to assess intracortical inhibition and facilitation, respectively. The time course of burst-induced excitability changes differed between groups. Healthy controls showed a short-lived increase in excitability that was only present 50 ms after the burst. In contrast, patients with episodic ataxia type 2 showed an abnormally prolonged increase in corticospinal excitability that was still present 250 ms after the transcranial magnetic stimulation burst. Furthermore, while controls showed a decrease in intracortical facilitation during the 1 s period following the transcranial magnetic stimulation burst, patients with episodic ataxia type 2 had increased intracortical facilitation 1000 ms after the burst. Intracortical inhibition was unaltered between groups. Patients with familial hemiplegic migraine were not significantly different from either controls or patients with episodic ataxia type 2. Together, these findings indicate that patients with episodic ataxia type 2 have an excessive increase in motor cortex excitability following a strong facilitatory input. We argue that this deficient control of cortical excitability may set the stage for the emergence of paroxysmal neural dysfunction in this disorder.
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Affiliation(s)
- Rick C Helmich
- Radboud University Nijmegen Medical Center, Department of Neurology, Nijmegen, The Netherlands.
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A novel form of presynaptic plasticity based on the fast reactivation of release sites switched off during low-frequency depression. J Neurosci 2011; 30:16679-91. [PMID: 21148007 DOI: 10.1523/jneurosci.3644-09.2010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Repetitive firing of neurons at a low frequency often leads to a decrease in synaptic strength. The mechanism of this low-frequency depression (LFD) is poorly understood. Here, LFD was studied at Aplysia cholinergic synapses. The absence of a significant change in the paired-pulse ratio during LFD, together with the facts that neither the time course nor the extent of LFD were affected by the initial release probability, suggests that LFD is not related to a depletion of the ready-to-fuse synaptic vesicles (SVs) or to a decrease in the release probability, but results from the silencing of a subpopulation of release sites. A subset of SVs or release sites, which acquired a high release probability status during LFD, permits synapses to rapidly and temporarily recover the initial synaptic strength when the stimulation is stopped. However, the recovery of the full capacity of the synapse to sustain repetitive stimulations is slow and involves spontaneous reactivation of the silent release sites. Application of tetanic stimulations accelerates this recovery by immediately switching on the silent sites. This high-frequency-dependent phenomenon underlies a new form of synaptic plasticity that allows resetting of presynaptic efficiency independently of the recent history of the synapse. Microinjection of a mutated Aplysia synapsin that cannot be phosphorylated by cAMP-dependent protein kinase (PKA), or a PKA inhibitor both prevented high-frequency-dependent awakening of release sites. Changes in the firing pattern of neurons appear to be able to regulate the on-off status of release sites via a molecular cascade involving PKA-dependent phosphorylation of synapsin.
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Molecular neurobiology of lead (Pb(2+)): effects on synaptic function. Mol Neurobiol 2010; 42:151-60. [PMID: 21042954 DOI: 10.1007/s12035-010-8146-0] [Citation(s) in RCA: 143] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Accepted: 10/13/2010] [Indexed: 12/16/2022]
Abstract
Lead (Pb(2+)) is a ubiquitous environmental neurotoxicant that continues to threaten public health on a global scale. Epidemiological studies have demonstrated detrimental effects of Pb(2+) on childhood IQ at very low levels of exposure. Recently, a mechanistic understanding of how Pb(2+) affects brain development has begun to emerge. The cognitive effects of Pb(2+) exposure are believed to be mediated through its selective inhibition of the N-methyl-D: -aspartate receptor (NMDAR). Studies in animal models of developmental Pb(2+) exposure exhibit altered NMDAR subunit ontogeny and disruption of NMDAR-dependent intracellular signaling. Additional studies have reported that Pb(2+) exposure inhibits presynaptic calcium (Ca(2+)) channels and affects presynaptic neurotransmission, but a mechanistic link between presynaptic and postsynaptic effects has been missing. Recent work has suggested that the presynaptic and postsynaptic effects of Pb(2+) exposure are both due to inhibition of the NMDAR by Pb(2+), and that the presynaptic effects of Pb(2+) may be mediated by disruption of NMDAR activity-dependent signaling of brain-derived neurotrophic factor (BDNF). These findings provide the basis for the first working model to describe the effects of Pb(2+) exposure on synaptic function. Here, we review the neurotoxic effects of Pb(2+) exposure and discuss the known effects of Pb(2+) exposure in light of these recent findings.
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Xue L, Wu LG. Post-tetanic potentiation is caused by two signalling mechanisms affecting quantal size and quantal content. J Physiol 2010; 588:4987-94. [PMID: 21041528 DOI: 10.1113/jphysiol.2010.196964] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
A high-frequency action potential train induces post-tetanic potentiation (PTP) of transmission at many synapses by increasing the intra-terminal calcium concentration, which may increase the quantal content by activation of protein kinase C (PKC). A recent study found that an increase of the mEPSC size, caused by compound vesicle fusion, parallels PTP, suggesting that the quantal size increase also contributes to the PTP generation. However, the strength of this suggestion is somewhat undermined by recent studies suggesting that vesicles responsible for spontaneous and evoked EPSCs may originate from different pools. Furthermore, it is unclear whether the quantal size increase is also mediated by PKC. The present work addressed these issues at a large calyx of Held synapse. We found that PTP was caused by both a PKC-dependent increase of the quantal content and a PKC-independent increase of the quantal size. In addition, we found that mEPSCs and EPSCs were subjected to similar up- and down-regulation, which verifies the basic assumption of quantal analysis--the same mechanism controls the quantal size of spontaneous and evoked release. This verification supports the use of quantal analysis at central synapses. However, unlike the traditional quantal analysis that attributes the quantal size change to a postsynaptic mechanism, the present work, together with one of our previous studies, suggests that the quantal size increase is caused by a presynaptic mechanism, the compound fusion among vesicles that forms large compound vesicles.
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Affiliation(s)
- Lei Xue
- National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Bldg 35, Bethesda, MD 20892, USA
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Kovyazina IV, Tsentsevitsky AN, Nikolsky EE, Bukharaeva EA. Kinetics of acetylcholine quanta release at the neuromuscular junction during high-frequency nerve stimulation. Eur J Neurosci 2010; 32:1480-9. [DOI: 10.1111/j.1460-9568.2010.07430.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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