101
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Neubrandt M, Oláh VJ, Brunner J, Szabadics J. Feedforward inhibition is randomly wired from individual granule cells onto CA3 pyramidal cells. Hippocampus 2017; 27:1034-1039. [PMID: 28696588 PMCID: PMC5637936 DOI: 10.1002/hipo.22763] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 05/30/2017] [Accepted: 06/27/2017] [Indexed: 01/22/2023]
Abstract
Feedforward inhibition (FFI) between the dentate gyrus (DG) and CA3 sparsifies and shapes memory‐ and spatial navigation‐related activities. However, our understanding of this prototypical FFI circuit lacks essential details, as the wiring of FFI is not yet mapped between individual DG granule cells (GCs) and CA3 pyramidal cells (PCs). Importantly, theoretically opposite network contributions are possible depending on whether the directly excited PCs are differently inhibited than the non‐excited PCs. Therefore, to better understand FFI wiring schemes, we compared the prevalence of disynaptic inhibitory postsynaptic events (diIPSCs) between pairs of individually recorded GC axons or somas and PCs, some of which were connected by monosynaptic excitation, while others were not. If FFI wiring is specific, diIPSCs are expected only in connected PCs; whereas diIPSCs should not be present in these PCs if FFI is laterally wired from individual GCs. However, we found single GC‐elicited diIPSCs with similar probabilities irrespective of the presence of monosynaptic excitation. This observation suggests that the wiring of FFI between individual GCs and PCs is independent of the direct excitation. Therefore, the randomly distributed FFI contributes to the hippocampal signal sparsification by setting the general excitability of the CA3 depending on the overall activity of GCs.
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Affiliation(s)
- Máté Neubrandt
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Viktor János Oláh
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - János Brunner
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - János Szabadics
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
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102
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Okuda K, Kobayashi S, Fukaya M, Watanabe A, Murakami T, Hagiwara M, Sato T, Ueno H, Ogonuki N, Komano-Inoue S, Manabe H, Yamaguchi M, Ogura A, Asahara H, Sakagami H, Mizuguchi M, Manabe T, Tanaka T. CDKL5 controls postsynaptic localization of GluN2B-containing NMDA receptors in the hippocampus and regulates seizure susceptibility. Neurobiol Dis 2017; 106:158-170. [PMID: 28688852 DOI: 10.1016/j.nbd.2017.07.002] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 06/10/2017] [Accepted: 07/02/2017] [Indexed: 12/21/2022] Open
Abstract
Mutations in the Cyclin-dependent kinase-like 5 (CDKL5) gene cause severe neurodevelopmental disorders accompanied by intractable epilepsies, i.e. West syndrome or atypical Rett syndrome. Here we report generation of the Cdkl5 knockout mouse and show that CDKL5 controls postsynaptic localization of GluN2B-containing N-methyl-d-aspartate (NMDA) receptors in the hippocampus and regulates seizure susceptibility. Cdkl5 -/Y mice showed normal sensitivity to kainic acid; however, they displayed significant hyperexcitability to NMDA. In concordance with this result, electrophysiological analysis in the hippocampal CA1 region disclosed an increased ratio of NMDA/α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-mediated excitatory postsynaptic currents (EPSCs) and a significantly larger decay time constant of NMDA receptor-mediated EPSCs (NMDA-EPSCs) as well as a stronger inhibition of the NMDA-EPSCs by the GluN2B-selective antagonist ifenprodil in Cdkl5 -/Y mice. Subcellular fractionation of the hippocampus from Cdkl5 -/Y mice revealed a significant increase of GluN2B and SAP102 in the PSD (postsynaptic density)-1T fraction, without changes in the S1 (post-nuclear) fraction or mRNA transcripts, indicating an intracellular distribution shift of these proteins to the PSD. Immunoelectron microscopic analysis of the hippocampal CA1 region further confirmed postsynaptic overaccumulation of GluN2B and SAP102 in Cdkl5 -/Y mice. Furthermore, ifenprodil abrogated the NMDA-induced hyperexcitability in Cdkl5 -/Y mice, suggesting that upregulation of GluN2B accounts for the enhanced seizure susceptibility. These data indicate that CDKL5 plays an important role in controlling postsynaptic localization of the GluN2B-SAP102 complex in the hippocampus and thereby regulates seizure susceptibility, and that aberrant NMDA receptor-mediated synaptic transmission underlies the pathological mechanisms of the CDKL5 loss-of-function.
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Affiliation(s)
- Kosuke Okuda
- Department of Developmental Medical Sciences, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Shizuka Kobayashi
- Division of Neuronal Network, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
| | - Masahiro Fukaya
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara 252-0374, Japan
| | - Aya Watanabe
- Department of Developmental Medical Sciences, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Takuto Murakami
- Department of Developmental Medical Sciences, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Mai Hagiwara
- Department of Developmental Medical Sciences, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Tempei Sato
- Department of Systems Biomedicine, National Research Institute for Child Health and Development, Tokyo 157-8535, Japan
| | - Hiroe Ueno
- Department of Systems Biomedicine, National Research Institute for Child Health and Development, Tokyo 157-8535, Japan
| | - Narumi Ogonuki
- Bioresource Engineering Division, RIKEN BioResource Center, Tsukuba 305-0074, Japan
| | - Sayaka Komano-Inoue
- Department of Physiology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Hiroyuki Manabe
- Department of Physiology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Masahiro Yamaguchi
- Department of Physiology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Atsuo Ogura
- Bioresource Engineering Division, RIKEN BioResource Center, Tsukuba 305-0074, Japan
| | - Hiroshi Asahara
- Department of Systems Biomedicine, National Research Institute for Child Health and Development, Tokyo 157-8535, Japan; Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla 92037, USA
| | - Hiroyuki Sakagami
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara 252-0374, Japan
| | - Masashi Mizuguchi
- Department of Developmental Medical Sciences, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Toshiya Manabe
- Division of Neuronal Network, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
| | - Teruyuki Tanaka
- Department of Developmental Medical Sciences, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan.
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103
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Short-Term Depression of Sprouted Mossy Fiber Synapses from Adult-Born Granule Cells. J Neurosci 2017; 37:5722-5735. [PMID: 28495975 DOI: 10.1523/jneurosci.0761-17.2017] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Revised: 04/25/2017] [Accepted: 05/03/2017] [Indexed: 11/21/2022] Open
Abstract
Epileptic seizures potently modulate hippocampal adult neurogenesis, and adult-born dentate granule cells contribute to the pathologic retrograde sprouting of mossy fiber axons, both hallmarks of temporal lobe epilepsy. The characteristics of these sprouted synapses, however, have been largely unexplored, and the specific contribution of adult-born granule cells to functional mossy fiber sprouting is unknown, primarily due to technical barriers in isolating sprouted mossy fiber synapses for analysis. Here, we used DcxCreERT2 transgenic mice to permanently pulse-label age-defined cohorts of granule cells born either before or after pilocarpine-induced status epilepticus (SE). Using optogenetics, we demonstrate that adult-born granule cells born before SE form functional recurrent monosynaptic excitatory connections with other granule cells. Surprisingly, however, although healthy mossy fiber synapses in CA3 are well characterized "detonator" synapses that potently drive postsynaptic cell firing through their profound frequency-dependent facilitation, sprouted mossy fiber synapses from adult-born cells exhibited profound frequency-dependent depression, despite possessing some of the morphological hallmarks of mossy fiber terminals. Mature granule cells also contributed to functional mossy fiber sprouting, but exhibited less synaptic depression. Interestingly, granule cells born shortly after SE did not form functional excitatory synapses, despite robust sprouting. Our results suggest that, although sprouted mossy fibers form recurrent excitatory circuits with some of the morphological characteristics of typical mossy fiber terminals, the functional characteristics of sprouted synapses would limit the contribution of adult-born granule cells to hippocampal hyperexcitability in the epileptic hippocampus.SIGNIFICANCE STATEMENT In the hippocampal dentate gyrus, seizures drive retrograde sprouting of granule cell mossy fiber axons. We directly activated sprouted mossy fiber synapses from adult-born granule cells to study their synaptic properties. We reveal that sprouted synapses from adult-born granule cells have a diminished ability to sustain recurrent excitation in the epileptic hippocampus, which raises questions about the role of sprouting and adult neurogenesis in sustaining seizure-like activity.
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104
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Short-Term Facilitation at a Detonator Synapse Requires the Distinct Contribution of Multiple Types of Voltage-Gated Calcium Channels. J Neurosci 2017; 37:4913-4927. [PMID: 28411270 DOI: 10.1523/jneurosci.0159-17.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 03/09/2017] [Accepted: 03/15/2017] [Indexed: 12/29/2022] Open
Abstract
Neuronal calcium elevations are shaped by several key parameters, including the properties, density, and the spatial location of voltage-gated calcium channels (VGCCs). These features allow presynaptic terminals to translate complex firing frequencies and tune the amount of neurotransmitter released. Although synchronous neurotransmitter release relies on both P/Q- and N-type VGCCs at hippocampal mossy fiber-CA3 synapses, the specific contribution of VGCCs to calcium dynamics, neurotransmitter release, and short-term facilitation remains unknown. Here, we used random-access two-photon calcium imaging together with electrophysiology in acute mouse hippocampal slices to dissect the roles of P/Q- and N-type VGCCs. Our results show that N-type VGCCs control glutamate release at a limited number of release sites through highly localized Ca2+ elevations and support short-term facilitation by enhancing multivesicular release. In contrast, Ca2+ entry via P/Q-type VGCCs promotes the recruitment of additional release sites through spatially homogeneous Ca2+ elevations. Altogether, our results highlight the specialized contribution of P/Q- and N-types VGCCs to neurotransmitter release.SIGNIFICANCE STATEMENT In presynaptic terminals, neurotransmitter release is dynamically regulated by the transient opening of different types of voltage-gated calcium channels. Hippocampal giant mossy fiber terminals display extensive short-term facilitation during repetitive activity, with a large several fold postsynaptic response increase. Though, how giant mossy fiber terminals leverage distinct types of voltage-gated calcium channels to mediate short-term facilitation remains unexplored. Here, we find that P/Q- and N-type VGCCs generate different spatial patterns of calcium elevations in giant mossy fiber terminals and support short-term facilitation through specific participation in two mechanisms. Whereas N-type VGCCs contribute only to the synchronization of multivesicular release, P/Q-type VGCCs act through microdomain signaling to recruit additional release sites.
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105
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Rebola N, Carta M, Mulle C. Operation and plasticity of hippocampal CA3 circuits: implications for memory encoding. Nat Rev Neurosci 2017; 18:208-220. [DOI: 10.1038/nrn.2017.10] [Citation(s) in RCA: 96] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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106
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Maingret V, Barthet G, Deforges S, Jiang N, Mulle C, Amédée T. PGE 2 -EP3 signaling pathway impairs hippocampal presynaptic long-term plasticity in a mouse model of Alzheimer's disease. Neurobiol Aging 2017; 50:13-24. [DOI: 10.1016/j.neurobiolaging.2016.10.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 10/03/2016] [Accepted: 10/09/2016] [Indexed: 10/20/2022]
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107
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Physiological Properties and Behavioral Correlates of Hippocampal Granule Cells and Mossy Cells. Neuron 2017; 93:691-704.e5. [PMID: 28132824 DOI: 10.1016/j.neuron.2016.12.011] [Citation(s) in RCA: 190] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 10/31/2016] [Accepted: 12/07/2016] [Indexed: 02/04/2023]
Abstract
The hippocampal dentate gyrus is often viewed as a segregator of upstream information. Physiological support for such function has been hampered by a lack of well-defined characteristics that can identify granule cells and mossy cells. We developed an electrophysiology-based classification of dentate granule cells and mossy cells in mice that we validated by optogenetic tagging of mossy cells. Granule cells exhibited sparse firing, had a single place field, and showed only modest changes when the mouse was tested in different mazes in the same room. In contrast, mossy cells were more active, had multiple place fields and showed stronger remapping of place fields under the same conditions. Although the granule cell-mossy cell synapse was strong and facilitating, mossy cells rarely "inherited" place fields from single granule cells. Our findings suggest that the granule cells and mossy cells could be modulated separately and their joint action may be critical for pattern separation.
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108
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Danielson NB, Turi GF, Ladow M, Chavlis S, Petrantonakis PC, Poirazi P, Losonczy A. In Vivo Imaging of Dentate Gyrus Mossy Cells in Behaving Mice. Neuron 2017; 93:552-559.e4. [PMID: 28132825 DOI: 10.1016/j.neuron.2016.12.019] [Citation(s) in RCA: 108] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2016] [Revised: 10/20/2016] [Accepted: 11/26/2016] [Indexed: 12/01/2022]
Abstract
Mossy cells in the hilus of the dentate gyrus constitute a major excitatory principal cell type in the mammalian hippocampus; however, it remains unknown how these cells behave in vivo. Here, we have used two-photon Ca2+ imaging to monitor the activity of mossy cells in awake, behaving mice. We find that mossy cells are significantly more active than dentate granule cells in vivo, exhibit spatial tuning during head-fixed spatial navigation, and undergo robust remapping of their spatial representations in response to contextual manipulation. Our results provide a functional characterization of mossy cells in the behaving animal and demonstrate their active participation in spatial coding and contextual representation.
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Affiliation(s)
- Nathan B Danielson
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Doctoral Program in Neurobiology and Behavior, Columbia University, New York, NY 10032, USA
| | - Gergely F Turi
- Department of Neuroscience, Columbia University, New York, NY 10032, USA
| | - Max Ladow
- Department of Neuroscience, Columbia University, New York, NY 10032, USA
| | - Spyridon Chavlis
- Institute of Molecular Biology and Biotechnology (IMBB), Foundation for Research and Technology - Hellas (FORTH), 700 13 Heraklion, Crete, Greece; Department of Biology, School of Sciences and Engineering, University of Crete, 741 00 Heraklion, Crete, Greece, Columbia University, New York, NY 10032, USA
| | - Panagiotis C Petrantonakis
- Institute of Molecular Biology and Biotechnology (IMBB), Foundation for Research and Technology - Hellas (FORTH), 700 13 Heraklion, Crete, Greece
| | - Panayiota Poirazi
- Institute of Molecular Biology and Biotechnology (IMBB), Foundation for Research and Technology - Hellas (FORTH), 700 13 Heraklion, Crete, Greece.
| | - Attila Losonczy
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Kavli Institute for Brain Science, Columbia University, New York, NY 10032, USA; Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA.
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109
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Scharkowski F, Frotscher M, Lutz D, Korte M, Michaelsen-Preusse K. Altered Connectivity and Synapse Maturation of the Hippocampal Mossy Fiber Pathway in a Mouse Model of the Fragile X Syndrome. Cereb Cortex 2017; 28:852-867. [DOI: 10.1093/cercor/bhw408] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 12/22/2016] [Indexed: 12/12/2022] Open
Affiliation(s)
- F Scharkowski
- Division of Cellular Neurobiology, Zoological Institute, TU Braunschweig, 38106 Braunschweig, Germany
| | - Michael Frotscher
- ZMNH, Institute for Structural Neurobiology, D-20251 Hamburg, Germany
| | - David Lutz
- ZMNH, Institute for Structural Neurobiology, D-20251 Hamburg, Germany
| | - Martin Korte
- Division of Cellular Neurobiology, Zoological Institute, TU Braunschweig, 38106 Braunschweig, Germany
- Helmholtz Centre for Infection Research, AG NIND, 38124 Braunschweig, Germany
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110
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Severa W, Parekh O, James CD, Aimone JB. A Combinatorial Model for Dentate Gyrus Sparse Coding. Neural Comput 2017; 29:94-117. [DOI: 10.1162/neco_a_00905] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The dentate gyrus forms a critical link between the entorhinal cortex and CA3 by providing a sparse version of the signal. Concurrent with this increase in sparsity, a widely accepted theory suggests the dentate gyrus performs pattern separation—similar inputs yield decorrelated outputs. Although an active region of study and theory, few logically rigorous arguments detail the dentate gyrus’s (DG) coding. We suggest a theoretically tractable, combinatorial model for this action. The model provides formal methods for a highly redundant, arbitrarily sparse, and decorrelated output signal.To explore the value of this model framework, we assess how suitable it is for two notable aspects of DG coding: how it can handle the highly structured grid cell representation in the input entorhinal cortex region and the presence of adult neurogenesis, which has been proposed to produce a heterogeneous code in the DG. We find tailoring the model to grid cell input yields expansion parameters consistent with the literature. In addition, the heterogeneous coding reflects activity gradation observed experimentally. Finally, we connect this approach with more conventional binary threshold neural circuit models via a formal embedding.
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Affiliation(s)
- William Severa
- Center for Computing Research, Sandia National Laboratories, Albuquerque, NM 87185, U.S.A
| | - Ojas Parekh
- Center for Computing Research, Sandia National Laboratories, Albuquerque, NM 87185, U.S.A
| | - Conrad D. James
- Center for Computing Research, Sandia National Laboratories, Albuquerque, NM 87185, U.S.A
| | - James B. Aimone
- Center for Computing Research, Sandia National Laboratories, Albuquerque, NM 87185, U.S.A
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111
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Petralia RS, Wang YX, Mattson MP, Yao PJ. The Diversity of Spine Synapses in Animals. Neuromolecular Med 2016; 18:497-539. [PMID: 27230661 PMCID: PMC5158183 DOI: 10.1007/s12017-016-8405-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 05/11/2016] [Indexed: 12/23/2022]
Abstract
Here we examine the structure of the various types of spine synapses throughout the animal kingdom. Based on available evidence, we suggest that there are two major categories of spine synapses: invaginating and non-invaginating, with distributions that vary among different groups of animals. In the simplest living animals with definitive nerve cells and synapses, the cnidarians and ctenophores, most chemical synapses do not form spine synapses. But some cnidarians have invaginating spine synapses, especially in photoreceptor terminals of motile cnidarians with highly complex visual organs, and also in some mainly sessile cnidarians with rapid prey capture reflexes. This association of invaginating spine synapses with complex sensory inputs is retained in the evolution of higher animals in photoreceptor terminals and some mechanoreceptor synapses. In contrast to invaginating spine synapse, non-invaginating spine synapses have been described only in animals with bilateral symmetry, heads and brains, associated with greater complexity in neural connections. This is apparent already in the simplest bilaterians, the flatworms, which can have well-developed non-invaginating spine synapses in some cases. Non-invaginating spine synapses diversify in higher animal groups. We also discuss the functional advantages of having synapses on spines and more specifically, on invaginating spines. And finally we discuss pathologies associated with spine synapses, concentrating on those systems and diseases where invaginating spine synapses are involved.
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Affiliation(s)
- Ronald S Petralia
- Advanced Imaging Core, NIDCD/NIH, 35A Center Drive, Room 1E614, Bethesda, MD, 20892-3729, USA.
| | - Ya-Xian Wang
- Advanced Imaging Core, NIDCD/NIH, 35A Center Drive, Room 1E614, Bethesda, MD, 20892-3729, USA
| | - Mark P Mattson
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD, 21224, USA
| | - Pamela J Yao
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD, 21224, USA
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112
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Kelly T, Beck H. Functional properties of granule cells with hilar basal dendrites in the epileptic dentate gyrus. Epilepsia 2016; 58:160-171. [PMID: 27888509 DOI: 10.1111/epi.13605] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/10/2016] [Indexed: 01/24/2023]
Abstract
OBJECTIVE The maturation of adult-born granule cells and their functional integration into the network is thought to play a key role in the proper functioning of the dentate gyrus. In temporal lobe epilepsy, adult-born granule cells in the dentate gyrus develop abnormally and possess a hilar basal dendrite (HBD). Although morphological studies have shown that these HBDs have synapses, little is known about the functional properties of these HBDs or the intrinsic and network properties of the granule cells that possess these aberrant dendrites. METHODS We performed patch-clamp recordings of granule cells within the granule cell layer "normotopic" from sham-control and status epilepticus (SE) animals. Normotopic granule cells from SE animals possessed an HBD (SE+ HBD+ cells) or not (SE+ HBD- cells). Apical and basal dendrites were stimulated using multiphoton uncaging of glutamate. Two-photon Ca2+ imaging was used to measure Ca2+ transients associated with back-propagating action potentials (bAPs). RESULTS Near-synchronous synaptic input integrated linearly in apical dendrites from sham-control animals and was not significantly different in apical dendrites of SE+ HBD- cells. The majority of HBDs integrated input linearly, similar to apical dendrites. However, 2 of 11 HBDs were capable of supralinear integration mediated by a dendritic spike. Furthermore, the bAP-evoked Ca2+ transients were relatively well maintained along HBDs, compared with apical dendrites. This further suggests an enhanced electrogenesis in HBDs. In addition, the output of granule cells from epileptic tissue was enhanced, with both SE+ HBD- and SE+ HBD+ cells displaying increased high-frequency (>100 Hz) burst-firing. Finally, both SE+ HBD- and SE+ HBD+ cells received recurrent excitatory input that was capable of generating APs, especially in the absence of feedback inhibition. SIGNIFICANCE Taken together, these data suggest that the enhanced excitability of HBDs combined with the altered intrinsic and network properties of granule cells collude to promote excitability and synchrony in the epileptic dentate gyrus.
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Affiliation(s)
- Tony Kelly
- Laboratory for Experimental Epileptology and Cognition Research, Department of Epileptology, University of Bonn, Bonn, Germany
| | - Heinz Beck
- Laboratory for Experimental Epileptology and Cognition Research, Department of Epileptology, University of Bonn, Bonn, Germany.,German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
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113
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Lee CT, Kao MH, Hou WH, Wei YT, Chen CL, Lien CC. Causal Evidence for the Role of Specific GABAergic Interneuron Types in Entorhinal Recruitment of Dentate Granule Cells. Sci Rep 2016; 6:36885. [PMID: 27830729 PMCID: PMC5103275 DOI: 10.1038/srep36885] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Accepted: 10/24/2016] [Indexed: 01/16/2023] Open
Abstract
The dentate gyrus (DG) is the primary gate of the hippocampus and controls information flow from the cortex to the hippocampus proper. To maintain normal function, granule cells (GCs), the principal neurons in the DG, receive fine-tuned inhibition from local-circuit GABAergic inhibitory interneurons (INs). Abnormalities of GABAergic circuits in the DG are associated with several brain disorders, including epilepsy, autism, schizophrenia, and Alzheimer disease. Therefore, understanding the network mechanisms of inhibitory control of GCs is of functional and pathophysiological importance. GABAergic inhibitory INs are heterogeneous, but it is unclear how individual subtypes contribute to GC activity. Using cell-type-specific optogenetic perturbation, we investigated whether and how two major IN populations defined by parvalbumin (PV) and somatostatin (SST) expression, regulate GC input transformations. We showed that PV-expressing (PV+) INs, and not SST-expressing (SST+) INs, primarily suppress GC responses to single cortical stimulation. In addition, these two IN classes differentially regulate GC responses to θ and γ frequency inputs from the cortex. Notably, PV+ INs specifically control the onset of the spike series, whereas SST+ INs preferentially regulate the later spikes in the series. Together, PV+ and SST+ GABAergic INs engage differentially in GC input-output transformations in response to various activity patterns.
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Affiliation(s)
- Cheng-Ta Lee
- Institute of Neuroscience, National Yang-Ming University, 155, Section 2, Li-Nong Street, Taipei 112, Taiwan
| | - Min-Hua Kao
- Institute of Neuroscience, National Yang-Ming University, 155, Section 2, Li-Nong Street, Taipei 112, Taiwan
| | - Wen-Hsien Hou
- Institute of Neuroscience, National Yang-Ming University, 155, Section 2, Li-Nong Street, Taipei 112, Taiwan
| | - Yu-Ting Wei
- Institute of Neuroscience, National Yang-Ming University, 155, Section 2, Li-Nong Street, Taipei 112, Taiwan
| | - Chin-Lin Chen
- Institute of Neuroscience, National Yang-Ming University, 155, Section 2, Li-Nong Street, Taipei 112, Taiwan
| | - Cheng-Chang Lien
- Institute of Neuroscience, National Yang-Ming University, 155, Section 2, Li-Nong Street, Taipei 112, Taiwan
- Institute of Brain Science, National Yang-Ming University, 155, Section 2, Li-Nong Street, Taipei 112, Taiwan
- Brain Research Center, National Yang-Ming University, Taipei 112, Taiwan
- Charité Universitätsmedizin Berlin, 10117 Berlin, Germany
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114
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Vyleta NP, Borges-Merjane C, Jonas P. Plasticity-dependent, full detonation at hippocampal mossy fiber-CA3 pyramidal neuron synapses. eLife 2016; 5:e17977. [PMID: 27780032 PMCID: PMC5079747 DOI: 10.7554/elife.17977] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 09/28/2016] [Indexed: 12/30/2022] Open
Abstract
Mossy fiber synapses on CA3 pyramidal cells are 'conditional detonators' that reliably discharge postsynaptic targets. The 'conditional' nature implies that burst activity in dentate gyrus granule cells is required for detonation. Whether single unitary excitatory postsynaptic potentials (EPSPs) trigger spikes in CA3 neurons remains unknown. Mossy fiber synapses exhibit both pronounced short-term facilitation and uniquely large post-tetanic potentiation (PTP). We tested whether PTP could convert mossy fiber synapses from subdetonator into detonator mode, using a recently developed method to selectively and noninvasively stimulate individual presynaptic terminals in rat brain slices. Unitary EPSPs failed to initiate a spike in CA3 neurons under control conditions, but reliably discharged them after induction of presynaptic short-term plasticity. Remarkably, PTP switched mossy fiber synapses into full detonators for tens of seconds. Plasticity-dependent detonation may be critical for efficient coding, storage, and recall of information in the granule cell-CA3 cell network.
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Affiliation(s)
- Nicholas P Vyleta
- Institute of Science and Technology Austria, Klosterneuburg, Austria
- Vollum Institute, Oregon Health and Science University, Portland, United States
| | | | - Peter Jonas
- Institute of Science and Technology Austria, Klosterneuburg, Austria
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115
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Villanueva-Castillo C, Tecuatl C, Herrera-López G, Galván EJ. Aging-related impairments of hippocampal mossy fibers synapses on CA3 pyramidal cells. Neurobiol Aging 2016; 49:119-137. [PMID: 27794263 DOI: 10.1016/j.neurobiolaging.2016.09.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Revised: 09/15/2016] [Accepted: 09/17/2016] [Indexed: 11/16/2022]
Abstract
The network interaction between the dentate gyrus and area CA3 of the hippocampus is responsible for pattern separation, a process that underlies the formation of new memories, and which is naturally diminished in the aged brain. At the cellular level, aging is accompanied by a progression of biochemical modifications that ultimately affects its ability to generate and consolidate long-term potentiation. Although the synapse between dentate gyrus via the mossy fibers (MFs) onto CA3 neurons has been subject of extensive studies, the question of how aging affects the MF-CA3 synapse is still unsolved. Extracellular and whole-cell recordings from acute hippocampal slices of aged Wistar rats (34 ± 2 months old) show that aging is accompanied by a reduction in the interneuron-mediated inhibitory mechanisms of area CA3. Several MF-mediated forms of short-term plasticity, MF long-term potentiation and at least one of the critical signaling cascades necessary for potentiation are also compromised in the aged brain. An analysis of the spontaneous glutamatergic and gamma-aminobutyric acid-mediated currents on CA3 cells reveal a dramatic alteration in amplitude and frequency of the nonevoked events. CA3 cells also exhibited increased intrinsic excitability. Together, these results demonstrate that aging is accompanied by a decrease in the GABAergic inhibition, reduced expression of short- and long-term forms of synaptic plasticity, and increased intrinsic excitability.
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Affiliation(s)
| | - Carolina Tecuatl
- Departamento de Farmacobiología, Cinvestav Sede Sur, México City, México
| | | | - Emilio J Galván
- Departamento de Farmacobiología, Cinvestav Sede Sur, México City, México.
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116
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Guzman SJ, Schlogl A, Frotscher M, Jonas P. Synaptic mechanisms of pattern completion in the hippocampal CA3 network. Science 2016; 353:1117-23. [DOI: 10.1126/science.aaf1836] [Citation(s) in RCA: 153] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2016] [Accepted: 07/15/2016] [Indexed: 11/02/2022]
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117
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Abnormal UP/DOWN Membrane Potential Dynamics Coupled with the Neocortical Slow Oscillation in Dentate Granule Cells during the Latent Phase of Temporal Lobe Epilepsy. eNeuro 2016; 3:eN-NWR-0017-16. [PMID: 27257629 PMCID: PMC4886220 DOI: 10.1523/eneuro.0017-16.2016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Revised: 04/26/2016] [Accepted: 04/28/2016] [Indexed: 01/31/2023] Open
Abstract
The dentate gyrus, a major entry point to the hippocampus, gates (or filters) incoming information from the cortex. During sleep or anesthesia, the slow-wave oscillation (SWO) orchestrates hippocampus-neocortex communication, which is important for memory formation. The dentate gate is altered in temporal lobe epilepsy (TLE) early during epileptogenesis, which favors the propagation of pathological activities. Yet, whether the gating of physiological SWO by dentate granule cells (DGCs) is altered in TLE has remained unexplored. We combined intracellular recordings of membrane potential (V m) of DGCs and local field potential recordings of the SWO in parietal cortex in anesthetized rats early during epileptogenesis [post-status epilepticus (SE) rats]. As expected, in control rats, the V m of DGCs weakly and rarely oscillated in the SWO frequency range. In contrast, in post-SE rats, the V m of DGCs displayed strong and long-lasting SWO. In these cells, clear UP and DOWN states, in phase with the neocortical SWO, led to a bimodal V m distribution. In post-SE rats, the firing of DGCs was increased and more temporally modulated by the neocortical SWO. We conclude that UP/DOWN state dynamics dominate the V m of DGCs and firing early during epileptogenesis. This abnormally strong neocortical influence on the dynamics of DGCs may profoundly modify the hippocampus-neocortex dialogue during sleep and associated cognitive functions.
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118
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Dengler CG, Coulter DA. Normal and epilepsy-associated pathologic function of the dentate gyrus. PROGRESS IN BRAIN RESEARCH 2016; 226:155-78. [PMID: 27323942 DOI: 10.1016/bs.pbr.2016.04.005] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The dentate gyrus plays critical roles both in cognitive processing, and in regulation of the induction and propagation of pathological activity. The cellular and circuit mechanisms underlying these diverse functions overlap extensively. At the cellular level, the intrinsic properties of dentate granule cells combine to endow these neurons with a fundamental reluctance to activate, one of their hallmark traits. At the circuit level, the dentate gyrus constitutes one of the more heavily inhibited regions of the brain, with strong, fast feedforward and feedback GABAergic inhibition dominating responses to afferent activation. In pathologic states such as epilepsy, a number of alterations within the dentate gyrus combine to compromise the regulatory properties of this circuit, culminating in a collapse of its normal function. This epilepsy-associated transformation in the fundamental properties of this critical regulatory hippocampal circuit may contribute both to seizure propensity, and cognitive and emotional comorbidities characteristic of this disease state.
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Affiliation(s)
- C G Dengler
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - D A Coulter
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States; The Research Institute of the Children's Hospital of Philadelphia, Philadelphia, PA, United States.
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119
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Kowalski J, Gan J, Jonas P, Pernía‐Andrade AJ. Intrinsic membrane properties determine hippocampal differential firing pattern in vivo in anesthetized rats. Hippocampus 2016; 26:668-82. [PMID: 26605995 PMCID: PMC5019144 DOI: 10.1002/hipo.22550] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/16/2015] [Indexed: 11/09/2022]
Abstract
The hippocampus plays a key role in learning and memory. Previous studies suggested that the main types of principal neurons, dentate gyrus granule cells (GCs), CA3 pyramidal neurons, and CA1 pyramidal neurons, differ in their activity pattern, with sparse firing in GCs and more frequent firing in CA3 and CA1 pyramidal neurons. It has been assumed but never shown that such different activity may be caused by differential synaptic excitation. To test this hypothesis, we performed high-resolution whole-cell patch-clamp recordings in anesthetized rats in vivo. In contrast to previous in vitro data, both CA3 and CA1 pyramidal neurons fired action potentials spontaneously, with a frequency of ∼3-6 Hz, whereas GCs were silent. Furthermore, both CA3 and CA1 cells primarily fired in bursts. To determine the underlying mechanisms, we quantitatively assessed the frequency of spontaneous excitatory synaptic input, the passive membrane properties, and the active membrane characteristics. Surprisingly, GCs showed comparable synaptic excitation to CA3 and CA1 cells and the highest ratio of excitation versus hyperpolarizing inhibition. Thus, differential synaptic excitation is not responsible for differences in firing. Moreover, the three types of hippocampal neurons markedly differed in their passive properties. While GCs showed the most negative membrane potential, CA3 pyramidal neurons had the highest input resistance and the slowest membrane time constant. The three types of neurons also differed in the active membrane characteristics. GCs showed the highest action potential threshold, but displayed the largest gain of the input-output curves. In conclusion, our results reveal that differential firing of the three main types of hippocampal principal neurons in vivo is not primarily caused by differences in the characteristics of the synaptic input, but by the distinct properties of synaptic integration and input-output transformation.
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Affiliation(s)
- Janina Kowalski
- IST Austria (Institute of Science and Technology Austria)KlosterneuburgAustria
- Psychiatric University Clinics (UPK) BaselSwitzerland
| | - Jian Gan
- IST Austria (Institute of Science and Technology Austria)KlosterneuburgAustria
| | - Peter Jonas
- IST Austria (Institute of Science and Technology Austria)KlosterneuburgAustria
| | - Alejandro J. Pernía‐Andrade
- IST Austria (Institute of Science and Technology Austria)KlosterneuburgAustria
- Department of Structural and Computational BiologyUniversity of ViennaAustria
- Institute of Molecular PathologyVienna BiocenterAustria
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120
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Lopez-Rojas J, Kreutz MR. Mature granule cells of the dentate gyrus--Passive bystanders or principal performers in hippocampal function? Neurosci Biobehav Rev 2016; 64:167-74. [PMID: 26949226 DOI: 10.1016/j.neubiorev.2016.02.021] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2015] [Revised: 01/18/2016] [Accepted: 02/27/2016] [Indexed: 10/22/2022]
Abstract
The dentate gyrus is the main entrance of highly processed information to the hippocampus which derives from associative cortices and it is one of the few privileged areas in the brain where adult neurogenesis occurs. This creates the unique situation that neurons of diverse maturation stages are part of one neuronal network at any given point in life. While recently adult-born cells have a low induction threshold for long-term potentiation several studies suggest that following maturation granule cells are poorly excitable and they exhibit reduced Hebbian synaptic plasticity to an extent that it was even suggested that they functionally retire. Here, we review the functional properties of mature granule cells and discuss how plasticity of intrinsic excitability and alterations in excitation-inhibition balance might impact on their role in hippocampal information processing.
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Affiliation(s)
- Jeffrey Lopez-Rojas
- Research Group Neuroplasticity, Leibniz Institute for Neurobiology, Brenneckestrasse 6, D-39118 Magdeburg, Germany.
| | - Michael R Kreutz
- Research Group Neuroplasticity, Leibniz Institute for Neurobiology, Brenneckestrasse 6, D-39118 Magdeburg, Germany; Leibniz Group 'Dendritic Organelles and Synaptic Function', University Medical Center Hamburg-Eppendorf, Center for Molecular Neurobiology, ZMNH, 20251 Hamburg, Germany
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121
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Scharfman HE, Myers CE. Corruption of the dentate gyrus by "dominant" granule cells: Implications for dentate gyrus function in health and disease. Neurobiol Learn Mem 2016; 129:69-82. [PMID: 26391451 PMCID: PMC4792754 DOI: 10.1016/j.nlm.2015.09.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 09/02/2015] [Accepted: 09/06/2015] [Indexed: 12/31/2022]
Abstract
The dentate gyrus (DG) and area CA3 of the hippocampus are highly organized lamellar structures which have been implicated in specific cognitive functions such as pattern separation and pattern completion. Here we describe how the anatomical organization and physiology of the DG and CA3 are consistent with structures that perform pattern separation and completion. We then raise a new idea related to the complex circuitry of the DG and CA3 where CA3 pyramidal cell 'backprojections' play a potentially important role in the sparse firing of granule cells (GCs), considered important in pattern separation. We also propose that GC axons, the mossy fibers, already known for their highly specialized structure, have a dynamic function that imparts variance--'mossy fiber variance'--which is important to pattern separation and completion. Computational modeling is used to show that when a subset of GCs become 'dominant,' one consequence is loss of variance in the activity of mossy fiber axons and a reduction in pattern separation and completion in the model. Empirical data are then provided using an example of 'dominant' GCs--subsets of GCs that develop abnormally and have increased excitability. Notably, these abnormal GCs have been identified in animal models of disease where DG-dependent behaviors are impaired. Together these data provide insight into pattern separation and completion, and suggest that behavioral impairment could arise from dominance of a subset of GCs in the DG-CA3 network.
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Affiliation(s)
- Helen E Scharfman
- The Nathan S. Kline Institute for Psychiatric Research, 140 Old Orangeburg Rd., Orangeburg, NY 10962, United States; Departments of Child & Adolescent Psychiatry, Physiology & Neuroscience, and Psychiatry, New York University Langone Medical Center, United States.
| | - Catherine E Myers
- VA New Jersey Health Care System, VA Medical Center, NeuroBehavioral Research Lab (Mail Stop 15a), 385 Tremont Avenue, East Orange, NJ 07018, United States; Department of Pharmacology, Physiology & Neuroscience, Rutgers-New Jersey Medical School, United States
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122
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Toni N, Schinder AF. Maturation and Functional Integration of New Granule Cells into the Adult Hippocampus. Cold Spring Harb Perspect Biol 2015; 8:a018903. [PMID: 26637288 DOI: 10.1101/cshperspect.a018903] [Citation(s) in RCA: 115] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The adult hippocampus generates functional dentate granule cells (GCs) that release glutamate onto target cells in the hilus and cornus ammonis (CA)3 region, and receive glutamatergic and γ-aminobutyric acid (GABA)ergic inputs that tightly control their spiking activity. The slow and sequential development of their excitatory and inhibitory inputs makes them particularly relevant for information processing. Although they are still immature, new neurons are recruited by afferent activity and display increased excitability, enhanced activity-dependent plasticity of their input and output connections, and a high rate of synaptogenesis. Once fully mature, new GCs show all the hallmarks of neurons generated during development. In this review, we focus on how developing neurons remodel the adult dentate gyrus and discuss key aspects that illustrate the potential of neurogenesis as a mechanism for circuit plasticity and function.
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Affiliation(s)
- Nicolas Toni
- Department of Fundamental Neurosciences, University of Lausanne, CH-1005 Lausanne, Switzerland
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123
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Johnston ST, Shtrahman M, Parylak S, Gonçalves JT, Gage FH. Paradox of pattern separation and adult neurogenesis: A dual role for new neurons balancing memory resolution and robustness. Neurobiol Learn Mem 2015; 129:60-8. [PMID: 26549627 DOI: 10.1016/j.nlm.2015.10.013] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 10/22/2015] [Accepted: 10/27/2015] [Indexed: 01/31/2023]
Abstract
Hippocampal adult neurogenesis is thought to subserve pattern separation, the process by which similar patterns of neuronal inputs are transformed into distinct neuronal representations, permitting the discrimination of highly similar stimuli in hippocampus-dependent tasks. However, the mechanism by which immature adult-born dentate granule neurons cells (abDGCs) perform this function remains unknown. Two theories of abDGC function, one by which abDGCs modulate and sparsify activity in the dentate gyrus and one by which abDGCs act as autonomous coding units, are generally suggested to be mutually exclusive. This review suggests that these two mechanisms work in tandem to dynamically regulate memory resolution while avoiding memory interference and maintaining memory robustness.
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Affiliation(s)
- Stephen T Johnston
- Laboratory of Genetics, Salk Institute for Biological Studies, La Jolla, CA 92037, United States
| | - Matthew Shtrahman
- Laboratory of Genetics, Salk Institute for Biological Studies, La Jolla, CA 92037, United States
| | - Sarah Parylak
- Laboratory of Genetics, Salk Institute for Biological Studies, La Jolla, CA 92037, United States
| | - J Tiago Gonçalves
- Laboratory of Genetics, Salk Institute for Biological Studies, La Jolla, CA 92037, United States
| | - Fred H Gage
- Laboratory of Genetics, Salk Institute for Biological Studies, La Jolla, CA 92037, United States.
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124
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Wiera G, Mozrzymas JW. Extracellular proteolysis in structural and functional plasticity of mossy fiber synapses in hippocampus. Front Cell Neurosci 2015; 9:427. [PMID: 26582976 PMCID: PMC4631828 DOI: 10.3389/fncel.2015.00427] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Accepted: 10/09/2015] [Indexed: 02/04/2023] Open
Abstract
Brain is continuously altered in response to experience and environmental changes. One of the underlying mechanisms is synaptic plasticity, which is manifested by modification of synapse structure and function. It is becoming clear that regulated extracellular proteolysis plays a pivotal role in the structural and functional remodeling of synapses during brain development, learning and memory formation. Clearly, plasticity mechanisms may substantially differ between projections. Mossy fiber synapses onto CA3 pyramidal cells display several unique functional features, including pronounced short-term facilitation, a presynaptically expressed long-term potentiation (LTP) that is independent of NMDAR activation, and NMDA-dependent metaplasticity. Moreover, structural plasticity at mossy fiber synapses ranges from the reorganization of projection topology after hippocampus-dependent learning, through intrinsically different dynamic properties of synaptic boutons to pre- and postsynaptic structural changes accompanying LTP induction. Although concomitant functional and structural plasticity in this pathway strongly suggests a role of extracellular proteolysis, its impact only starts to be investigated in this projection. In the present report, we review the role of extracellular proteolysis in various aspects of synaptic plasticity in hippocampal mossy fiber synapses. A growing body of evidence demonstrates that among perisynaptic proteases, tissue plasminogen activator (tPA)/plasmin system, β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) and metalloproteinases play a crucial role in shaping plastic changes in this projection. We discuss recent advances and emerging hypotheses on the roles of proteases in mechanisms underlying mossy fiber target specific synaptic plasticity and memory formation.
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Affiliation(s)
- Grzegorz Wiera
- Department of Animal Molecular Physiology, Institute of Experimental Biology, Wroclaw University Wroclaw, Poland ; Laboratory of Neuroscience, Department of Biophysics, Wroclaw Medical University Wroclaw, Poland
| | - Jerzy W Mozrzymas
- Department of Animal Molecular Physiology, Institute of Experimental Biology, Wroclaw University Wroclaw, Poland ; Laboratory of Neuroscience, Department of Biophysics, Wroclaw Medical University Wroclaw, Poland
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125
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Evans MD, Dumitrescu AS, Kruijssen DLH, Taylor SE, Grubb MS. Rapid Modulation of Axon Initial Segment Length Influences Repetitive Spike Firing. Cell Rep 2015; 13:1233-1245. [PMID: 26526995 PMCID: PMC4646840 DOI: 10.1016/j.celrep.2015.09.066] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Revised: 08/10/2015] [Accepted: 09/22/2015] [Indexed: 12/31/2022] Open
Abstract
Neurons implement a variety of plasticity mechanisms to alter their function over timescales ranging from seconds to days. One powerful means of controlling excitability is to directly modulate the site of spike initiation, the axon initial segment (AIS). However, all plastic structural AIS changes reported thus far have been slow, involving days of neuronal activity perturbation. Here, we show that AIS plasticity can be induced much more rapidly. Just 3 hr of elevated activity significantly shortened the AIS of dentate granule cells in a calcineurin-dependent manner. The functional effects of rapid AIS shortening were offset by dephosphorylation of voltage-gated sodium channels, another calcineurin-dependent mechanism. However, pharmacological separation of these phenomena revealed a significant relationship between AIS length and repetitive firing. The AIS can therefore undergo a rapid form of structural change over timescales that enable interactions with other forms of activity-dependent plasticity in the dynamic control of neuronal excitability. Structural plasticity at the axon initial segment can occur within hours Ankyrin-G and sodium channel distributions shorten after 3 hr of elevated activity Rapid plasticity depends on calcineurin signaling opposed by CDK5 All else being equal, AIS shortening correlates with lowered neuronal excitability
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Affiliation(s)
- Mark D Evans
- MRC Centre for Developmental Neurobiology, King's College London, 4(th) Floor, New Hunt's House, Guy's Campus, London SE1 1UL, UK
| | - Adna S Dumitrescu
- MRC Centre for Developmental Neurobiology, King's College London, 4(th) Floor, New Hunt's House, Guy's Campus, London SE1 1UL, UK
| | - Dennis L H Kruijssen
- MRC Centre for Developmental Neurobiology, King's College London, 4(th) Floor, New Hunt's House, Guy's Campus, London SE1 1UL, UK
| | - Samuel E Taylor
- MRC Centre for Developmental Neurobiology, King's College London, 4(th) Floor, New Hunt's House, Guy's Campus, London SE1 1UL, UK
| | - Matthew S Grubb
- MRC Centre for Developmental Neurobiology, King's College London, 4(th) Floor, New Hunt's House, Guy's Campus, London SE1 1UL, UK.
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126
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Wakita M, Kotani N, Yamaga T, Akaike N. Nitrous oxide directly inhibits action potential-dependent neurotransmission from single presynaptic boutons adhering to rat hippocampal CA3 neurons. Brain Res Bull 2015; 118:34-45. [PMID: 26343381 DOI: 10.1016/j.brainresbull.2015.09.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Revised: 08/26/2015] [Accepted: 09/01/2015] [Indexed: 11/16/2022]
Abstract
We evaluated the effects of N2O on synaptic transmission using a preparation of mechanically dissociated rat hippocampal CA3 neurons that allowed assays of single bouton responses evoked from native functional nerve endings. We studied the effects of N2O on GABAA, glutamate, AMPA and NMDA receptor-mediated currents (IGABA, IGlu, IAMPA and INMDA) elicited by exogenous application of GABA, glutamate, (S)-AMPA, and NMDA and spontaneous, miniature, and evoked GABAergic inhibitory and glutamatergic excitatory postsynaptic current (sIPSC, mIPSC, eIPSC, sEPSC, mEPSC and eEPSC) in mechanically dissociated CA3 neurons. eIPSC and eEPSC were evoked by focal electrical stimulation of a single bouton. Administration of 70% N2O altered neither IGABA nor the frequency and amplitude of both sIPSCs and mIPSCs. In contrast, N2O decreased the amplitude of eIPSCs, while increasing failure rates (Rf) and paired-pulse ratios (PPR) in a concentration-dependent manner. On the other hand, N2O decreased IGlu, IAMPA and INMDA. Again N2O did not change the frequency and amplitude of either sEPSCs of mEPSCs. N2O also decreased amplitudes of eEPSCs with increased Rf and PPR. The decay phases of all synaptic responses were unchanged. The present results indicated that N2O inhibits the activation of AMPA/KA and NMDA receptors and also that N2O preferentially depress the action potential-dependent GABA and glutamate releases but had little effects on spontaneous and miniature releases.
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Affiliation(s)
- Masahito Wakita
- Research Division for Clinical Pharmacology, Medical Corporation, Jyuryo Group, Kumamoto Kinoh Hospital, 6-8-1 Yamamuro, Kitaku, Kumamoto 860-8518, Japan; Research Division for Life Science, Kumamoto Health Science University, 325 Izumi-machi, Kitaku, Kumamoto 861-5598, Japan
| | - Naoki Kotani
- Research Division of Neurophysiology, Kitamoto Hospital, 3-7-6 Kawarasone, Koshigaya, Saitama 343-0821, Japan
| | - Toshitaka Yamaga
- Research Division for Life Science, Kumamoto Health Science University, 325 Izumi-machi, Kitaku, Kumamoto 861-5598, Japan
| | - Norio Akaike
- Research Division for Clinical Pharmacology, Medical Corporation, Jyuryo Group, Kumamoto Kinoh Hospital, 6-8-1 Yamamuro, Kitaku, Kumamoto 860-8518, Japan; Research Division for Life Science, Kumamoto Health Science University, 325 Izumi-machi, Kitaku, Kumamoto 861-5598, Japan; Research Division of Neurophysiology, Kitamoto Hospital, 3-7-6 Kawarasone, Koshigaya, Saitama 343-0821, Japan.
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127
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Witton J, Padmashri R, Zinyuk L, Popov V, Kraev I, Line S, Jensen T, Tedoldi A, Cummings D, Tybulewicz V, Fisher E, Bannerman D, Randall A, Brown J, Edwards F, Rusakov D, Stewart M, Jones M. Hippocampal circuit dysfunction in the Tc1 mouse model of Down syndrome. Nat Neurosci 2015; 18:1291-1298. [PMID: 26237367 PMCID: PMC4552261 DOI: 10.1038/nn.4072] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 06/29/2015] [Indexed: 12/11/2022]
Abstract
Hippocampal pathology is likely to contribute to cognitive disability in Down syndrome, yet the neural network basis of this pathology and its contributions to different facets of cognitive impairment remain unclear. Here we report dysfunctional connectivity between dentate gyrus and CA3 networks in the transchromosomic Tc1 mouse model of Down syndrome, demonstrating that ultrastructural abnormalities and impaired short-term plasticity at dentate gyrus-CA3 excitatory synapses culminate in impaired coding of new spatial information in CA3 and CA1 and disrupted behavior in vivo. These results highlight the vulnerability of dentate gyrus-CA3 networks to aberrant human chromosome 21 gene expression and delineate hippocampal circuit abnormalities likely to contribute to distinct cognitive phenotypes in Down syndrome.
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Affiliation(s)
- J. Witton
- School of Physiology & Pharmacology, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - R. Padmashri
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK
| | - L.E. Zinyuk
- School of Physiology & Pharmacology, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - V.I. Popov
- Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Reg. 142290, Russia
- The Open University, Department of Life Sciences, Walton Hall, Milton Keynes, MK7 6AA, UK
| | - I. Kraev
- The Open University, Department of Life Sciences, Walton Hall, Milton Keynes, MK7 6AA, UK
| | - S.J. Line
- Department of Experimental Psychology, University of Oxford, Oxford OX1 3UD, UK
| | - T.P. Jensen
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK
| | - A. Tedoldi
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
| | - D.M. Cummings
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
| | - V.L.J. Tybulewicz
- MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
| | - E.M.C. Fisher
- Department of Neurodegenerative Disease, UCL Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK
| | - D.M. Bannerman
- Department of Experimental Psychology, University of Oxford, Oxford OX1 3UD, UK
| | - A.D. Randall
- School of Physiology & Pharmacology, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - J.T. Brown
- School of Physiology & Pharmacology, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - F.A. Edwards
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
| | - D.A. Rusakov
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK
- Laboratory of Brain Microcircuits, Institute of Biology and Biomedicine, University of Nizhny Novgorod, Nizhny Novgorod 603950, Russia
| | - M.G. Stewart
- The Open University, Department of Life Sciences, Walton Hall, Milton Keynes, MK7 6AA, UK
| | - M.W. Jones
- School of Physiology & Pharmacology, University of Bristol, University Walk, Bristol BS8 1TD, UK
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128
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Involvement of Adult Hippocampal Neurogenesis in Learning and Forgetting. Neural Plast 2015; 2015:717958. [PMID: 26380120 PMCID: PMC4561984 DOI: 10.1155/2015/717958] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2014] [Revised: 03/12/2015] [Accepted: 03/31/2015] [Indexed: 12/20/2022] Open
Abstract
Adult hippocampal neurogenesis is a process involving the continuous generation of newborn neurons in the hippocampus of adult animals. Mounting evidence has suggested that hippocampal neurogenesis contributes to some forms of hippocampus-dependent learning and memory; however, the detailed mechanism concerning how this small number of newborn neurons could affect learning and memory remains unclear. In this review, we discuss the relationship between adult-born neurons and learning and memory, with a highlight on recently discovered potential roles of neurogenesis in pattern separation and forgetting.
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129
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Rolls ET. Pattern separation, completion, and categorisation in the hippocampus and neocortex. Neurobiol Learn Mem 2015; 129:4-28. [PMID: 26190832 DOI: 10.1016/j.nlm.2015.07.008] [Citation(s) in RCA: 117] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Revised: 07/02/2015] [Accepted: 07/11/2015] [Indexed: 12/22/2022]
Abstract
The mechanisms for pattern completion and pattern separation are described in the context of a theory of hippocampal function in which the hippocampal CA3 system operates as a single attractor or autoassociation network to enable rapid, one-trial, associations between any spatial location (place in rodents, or spatial view in primates) and an object or reward, and to provide for completion of the whole memory during recall from any part. The factors important in the pattern completion in CA3 and also a large number of independent memories stored in CA3 include: a sparse distributed representation, representations that are independent due to the randomizing effect of the mossy fibres, heterosynaptic long-term depression as well as long-term potentiation in the recurrent collateral synapses, and diluted connectivity to minimize the number of multiple synapses between any pair of CA3 neurons which otherwise distort the basins of attraction. Recall of information from CA3 is implemented by the entorhinal cortex perforant path synapses to CA3 cells, which in acting as a pattern associator allow some pattern generalization. Pattern separation is performed in the dentate granule cells using competitive learning to convert grid-like entorhinal cortex firing to place-like fields, and in the dentate to CA3 connections that have diluted connectivity. Recall to the neocortex is achieved by a reverse hierarchical series of pattern association networks implemented by the hippocampo-cortical backprojections, each one of which performs some pattern generalization, to retrieve a complete pattern of cortical firing in higher-order cortical areas. New results on competitive networks show which factors contribute to their ability to perform pattern separation, pattern clustering, and pattern categorisation, and how these apply in different hippocampal and neocortical systems.
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Affiliation(s)
- Edmund T Rolls
- Oxford Centre for Computational Neuroscience, Oxford, England, United Kingdom; University of Warwick, Department of Computer Science, Coventry CV4 7AL, England, United Kingdom.
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130
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Hyun JH, Eom K, Lee KH, Bae JY, Bae YC, Kim MH, Kim S, Ho WK, Lee SH. Kv1.2 mediates heterosynaptic modulation of direct cortical synaptic inputs in CA3 pyramidal cells. J Physiol 2015; 593:3617-43. [PMID: 26047212 DOI: 10.1113/jp270372] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2015] [Accepted: 05/26/2015] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS We investigated the cellular mechanisms underlying mossy fibre-induced heterosynaptic long-term potentiation of perforant path (PP) inputs to CA3 pyramidal cells. Here we show that this heterosynaptic potentiation is mediated by downregulation of Kv1.2 channels. The downregulation of Kv1.2 preferentially enhanced PP-evoked EPSPs which occur at distal apical dendrites. Such enhancement of PP-EPSPs required activation of dendritic Na(+) channels, and its threshold was lowered by downregulation of Kv1.2. Our results may provide new insights into the long-standing question of how mossy fibre inputs constrain the CA3 network to sparsely represent direct cortical inputs. ABSTRACT A short high frequency stimulation of mossy fibres (MFs) induces long-term potentiation (LTP) of direct cortical or perforant path (PP) synaptic inputs in hippocampal CA3 pyramidal cells (CA3-PCs). However, the cellular mechanism underlying this heterosynaptic modulation remains elusive. Previously, we reported that repetitive somatic firing at 10 Hz downregulates Kv1.2 in the CA3-PCs. Here, we show that MF inputs induce similar somatic firing and downregulation of Kv1.2 in the CA3-PCs. The effect of Kv1.2 downregulation was specific to PP synaptic inputs that arrive at distal apical dendrites. We found that the somatodendritic expression of Kv1.2 is polarized to distal apical dendrites. Compartmental simulations based on this finding suggested that passive normalization of synaptic inputs and polarized distributions of dendritic ionic channels may facilitate the activation of dendritic Na(+) channels preferentially at distal apical dendrites. Indeed, partial block of dendritic Na(+) channels using 10 nm tetrodotoxin brought back the enhanced PP-evoked excitatory postsynaptic potentials (PP-EPSPs) to the baseline level. These results indicate that activity-dependent downregulation of Kv1.2 in CA3-PCs mediates MF-induced heterosynaptic LTP of PP-EPSPs by facilitating activation of Na(+) channels at distal apical dendrites.
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Affiliation(s)
- Jung Ho Hyun
- Cell Physiology Laboratory, Department of Physiology and bioMembrane Plasticity Research Centre, Seoul National University College of Medicine and Neuroscience Research Institute, Seoul National University Medical Research Centre, 103 Daehak-ro, Jongno-gu, Seoul, 110-799, Republic of Korea
| | - Kisang Eom
- Cell Physiology Laboratory, Department of Physiology and bioMembrane Plasticity Research Centre, Seoul National University College of Medicine and Neuroscience Research Institute, Seoul National University Medical Research Centre, 103 Daehak-ro, Jongno-gu, Seoul, 110-799, Republic of Korea
| | - Kyu-Hee Lee
- Cell Physiology Laboratory, Department of Physiology and bioMembrane Plasticity Research Centre, Seoul National University College of Medicine and Neuroscience Research Institute, Seoul National University Medical Research Centre, 103 Daehak-ro, Jongno-gu, Seoul, 110-799, Republic of Korea
| | - Jin Young Bae
- Department of Oral Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, 700-412, Republic of Korea
| | - Yong Chul Bae
- Department of Oral Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, 700-412, Republic of Korea
| | - Myoung-Hwan Kim
- Cell Physiology Laboratory, Department of Physiology and bioMembrane Plasticity Research Centre, Seoul National University College of Medicine and Neuroscience Research Institute, Seoul National University Medical Research Centre, 103 Daehak-ro, Jongno-gu, Seoul, 110-799, Republic of Korea
| | - Sooyun Kim
- Cell Physiology Laboratory, Department of Physiology and bioMembrane Plasticity Research Centre, Seoul National University College of Medicine and Neuroscience Research Institute, Seoul National University Medical Research Centre, 103 Daehak-ro, Jongno-gu, Seoul, 110-799, Republic of Korea
| | - Won-Kyung Ho
- Cell Physiology Laboratory, Department of Physiology and bioMembrane Plasticity Research Centre, Seoul National University College of Medicine and Neuroscience Research Institute, Seoul National University Medical Research Centre, 103 Daehak-ro, Jongno-gu, Seoul, 110-799, Republic of Korea
| | - Suk-Ho Lee
- Cell Physiology Laboratory, Department of Physiology and bioMembrane Plasticity Research Centre, Seoul National University College of Medicine and Neuroscience Research Institute, Seoul National University Medical Research Centre, 103 Daehak-ro, Jongno-gu, Seoul, 110-799, Republic of Korea
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131
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Pardi MB, Ogando MB, Schinder AF, Marin-Burgin A. Differential inhibition onto developing and mature granule cells generates high-frequency filters with variable gain. eLife 2015; 4:e08764. [PMID: 26163657 PMCID: PMC4521582 DOI: 10.7554/elife.08764] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2015] [Accepted: 07/10/2015] [Indexed: 11/13/2022] Open
Abstract
Adult hippocampal neurogenesis provides the dentate gyrus with heterogeneous populations of granule cells (GC) originated at different times. The contribution of these cells to information encoding is under current investigation. Here, we show that incoming spike trains activate different populations of GC determined by the stimulation frequency and GC age. Immature GC respond to a wider range of stimulus frequencies, whereas mature GC are less responsive at high frequencies. This difference is dictated by feedforward inhibition, which restricts mature GC activation. Yet, the stronger inhibition of mature GC results in a higher temporal fidelity compared to that of immature GC. Thus, hippocampal inputs activate two populations of neurons with variable frequency filters: immature cells, with wide-range responses, that are reliable transmitters of the incoming frequency, and mature neurons, with narrow frequency response, that are precise at informing the beginning of the stimulus, but with a sparse activity.
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Affiliation(s)
- María Belén Pardi
- Instituto de Investigación en Biomedicina de Buenos Aires-CONICET-Partner Institute of the Max Planck Society, Buenos Aires, Argentina
| | - Mora Belén Ogando
- Instituto de Investigación en Biomedicina de Buenos Aires-CONICET-Partner Institute of the Max Planck Society, Buenos Aires, Argentina
| | - Alejandro F Schinder
- Laboratory of Neuronal Plasticity, Leloir Institute-CONICET, Buenos Aires, Argentina
| | - Antonia Marin-Burgin
- Instituto de Investigación en Biomedicina de Buenos Aires-CONICET-Partner Institute of the Max Planck Society, Buenos Aires, Argentina
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132
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Nakahara S, Miyake S, Tajinda K, Ito H. Mossy fiber mis-pathfinding and semaphorin reduction in the hippocampus of α-CaMKII hKO mice. Neurosci Lett 2015; 598:47-51. [DOI: 10.1016/j.neulet.2015.05.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 04/24/2015] [Accepted: 05/08/2015] [Indexed: 11/25/2022]
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133
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Krook-Magnuson E, Armstrong C, Bui A, Lew S, Oijala M, Soltesz I. In vivo evaluation of the dentate gate theory in epilepsy. J Physiol 2015; 593:2379-88. [PMID: 25752305 PMCID: PMC4457198 DOI: 10.1113/jp270056] [Citation(s) in RCA: 154] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 02/25/2015] [Indexed: 01/21/2023] Open
Abstract
The dentate gyrus is a region subject to intense study in epilepsy because of its posited role as a 'gate', acting to inhibit overexcitation in the hippocampal circuitry through its unique synaptic, cellular and network properties that result in relatively low excitability. Numerous changes predicted to produce dentate hyperexcitability are seen in epileptic patients and animal models. However, recent findings question whether changes are causative or reactive, as well as the pathophysiological relevance of the dentate in epilepsy. Critically, direct in vivo modulation of dentate 'gate' function during spontaneous seizure activity has not been explored. Therefore, using a mouse model of temporal lobe epilepsy with hippocampal sclerosis, a closed-loop system and selective optogenetic manipulation of granule cells during seizures, we directly tested the dentate 'gate' hypothesis in vivo. Consistent with the dentate gate theory, optogenetic gate restoration through granule cell hyperpolarization efficiently stopped spontaneous seizures. By contrast, optogenetic activation of granule cells exacerbated spontaneous seizures. Furthermore, activating granule cells in non-epileptic animals evoked acute seizures of increasing severity. These data indicate that the dentate gyrus is a critical node in the temporal lobe seizure network, and provide the first in vivo support for the dentate 'gate' hypothesis.
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Affiliation(s)
| | - Caren Armstrong
- Department of Anatomy and Neurobiology, University of CaliforniaIrvine, USA
| | - Anh Bui
- Department of Anatomy and Neurobiology, University of CaliforniaIrvine, USA
| | - Sean Lew
- Department of Anatomy and Neurobiology, University of CaliforniaIrvine, USA
| | - Mikko Oijala
- Department of Anatomy and Neurobiology, University of CaliforniaIrvine, USA
| | - Ivan Soltesz
- Department of Anatomy and Neurobiology, University of CaliforniaIrvine, USA
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134
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Wang X, Zhang D, Lu XY. Dentate gyrus-CA3 glutamate release/NMDA transmission mediates behavioral despair and antidepressant-like responses to leptin. Mol Psychiatry 2015; 20:509-19. [PMID: 25092243 PMCID: PMC4362753 DOI: 10.1038/mp.2014.75] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Revised: 04/21/2014] [Accepted: 05/19/2014] [Indexed: 02/07/2023]
Abstract
Compelling evidence supports the important role of the glutamatergic system in the pathophysiology of major depression and also as a target for rapid-acting antidepressants. However, the functional role of glutamate release/transmission in behavioral processes related to depression and antidepressant efficacy remains to be elucidated. In this study, glutamate release and behavioral responses to tail suspension, a procedure commonly used for inducing behavioral despair, were simultaneously monitored in real time. The onset of tail suspension stress evoked a rapid increase in glutamate release in hippocampal field CA3, which declined gradually after its offset. Blockade of N-methyl-D-aspartic acid (NMDA) receptors by intra-CA3 infusion of MK-801, a non-competitive NMDA receptor antagonist, reversed behavioral despair. A subpopulation of granule neurons that innervated the CA3 region expressed leptin receptors and these cells were not activated by stress. Leptin treatment dampened tail suspension-evoked glutamate release in CA3. On the other hand, intra-CA3 infusion of NMDA blocked the antidepressant-like effect of leptin in reversing behavioral despair in both the tail suspension and forced swim tests, which involved activation of Akt signaling in DG. Taken together, these results suggest that the DG-CA3 glutamatergic pathway is critical for mediating behavioral despair and antidepressant-like responses to leptin.
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Affiliation(s)
- Xuezhen Wang
- Department of Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA,Institute for Metabolic and Neuropsychiatric Disorders, Binzhou Medical University, China
| | - Di Zhang
- Department of Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Xin-Yun Lu
- Department of Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA, Correspondence: Xin-Yun Lu, M.D., Ph.D. Department of Pharmacology University of Texas Health Science Center at San Antonio 7703 Floyd Curl Drive San Antonio, TX 78229, USA Phone: 210-567-0803 Fax: 210-567-4303
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135
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LaSarge CL, Santos VR, Danzer SC. PTEN deletion from adult-generated dentate granule cells disrupts granule cell mossy fiber axon structure. Neurobiol Dis 2015; 75:142-50. [PMID: 25600212 PMCID: PMC4351143 DOI: 10.1016/j.nbd.2014.12.029] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Revised: 12/17/2014] [Accepted: 12/26/2014] [Indexed: 01/30/2023] Open
Abstract
Dysregulation of the mTOR-signaling pathway is implicated in the development of temporal lobe epilepsy. In mice, deletion of PTEN from hippocampal dentate granule cells leads to mTOR hyperactivation and promotes the rapid onset of spontaneous seizures. The mechanism by which these abnormal cells initiate epileptogenesis, however, is unclear. PTEN-knockout granule cells develop abnormally, exhibiting morphological features indicative of increased excitatory input. If these cells are directly responsible for seizure genesis, it follows that they should also possess increased output. To test this prediction, dentate granule cell axon morphology was quantified in control and PTEN-knockout mice. Unexpectedly, PTEN deletion increased giant mossy fiber bouton spacing along the axon length, suggesting reduced innervation of CA3. Increased width of the mossy fiber axon pathway in stratum lucidum, however, which likely reflects an unusual increase in mossy fiber axon collateralization in this region, offsets the reduction in boutons per axon length. These morphological changes predict a net increase in granule cell innervation of CA3. Increased diameter of axons from PTEN-knockout cells would further enhance granule cell communication with CA3. Altogether, these findings suggest that amplified information flow through the hippocampal circuit contributes to seizure occurrence in the PTEN-knockout mouse model of temporal lobe epilepsy.
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Affiliation(s)
- Candi L LaSarge
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Victor R Santos
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA; Department of Physiology, Ribeirão Preto Medical School, Ribeirão Preto, SP, Brazil
| | - Steve C Danzer
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA; Department of Anesthesia, University of Cincinnati, Cincinnati, OH 45267, USA; Department of Pediatrics, University of Cincinnati, Cincinnati, OH 45267, USA.
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136
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Cutsuridis V, Poirazi P. A computational study on how theta modulated inhibition can account for the long temporal windows in the entorhinal-hippocampal loop. Neurobiol Learn Mem 2015; 120:69-83. [PMID: 25721691 DOI: 10.1016/j.nlm.2015.02.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Revised: 01/28/2015] [Accepted: 02/03/2015] [Indexed: 01/14/2023]
Abstract
A recent experimental study (Mizuseki, Sirota, Pastalkova, & Buzsaki, 2009) has shown that the temporal delays between population activities in successive entorhinal and hippocampal anatomical stages are longer (about 70-80ms) than expected from axon conduction velocities and passive synaptic integration of feed-forward excitatory inputs. We investigate via computer simulations the mechanisms that give rise to such long temporal delays in the hippocampus structures. A model of the dentate gyrus (DG), CA3 and CA1 microcircuits is presented that uses biophysical representations of the major cell types including granule cells, CA3 and CA1 pyramidal cells (PCs) and six types of interneurons: basket cells (BCs), axo-axonic cells (AACs), bistratified cells (BSCs), oriens lacunosum-moleculare cells (OLMs), mossy cells (MCs) and hilar perforant path associated cells (HC). Inputs to the network came from the entorhinal cortex (EC) (layers 2 and 3) and the medial septum (MS). The model simulates accurately the timing of firing of different hippocampal cells with respect to the theta rhythm. The model shows that the experimentally reported long temporal delays in the DG, CA3 and CA1 hippocampal regions are due to theta modulated somatic and axonic inhibition. The model further predicts that the phase at which the CA1 PCs fire with respect to the theta rhythm is determined primarily by their increased dendritic excitability caused by the decrease of the axial resistance and the A-type K(+) conductance along their dendritic trunk. The model predicted latencies by which the DG, CA3 and CA1 principal cells fire are inline with the experimental evidence. Finally, the model proposes functional roles for the different inhibitory interneurons in the retrieval of the memory pattern by the DG, CA3 and CA1 networks. The model makes a number of predictions, which can be tested experimentally, thus leading to a better understanding of the biophysical computations in the hippocampus.
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Affiliation(s)
- Vassilis Cutsuridis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas (FORTH), Vassilika Vouton 71110, Heraklion, Crete, Greece.
| | - Panayiota Poirazi
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas (FORTH), Vassilika Vouton 71110, Heraklion, Crete, Greece
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137
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Franco LM, Beltrán JQ, Tapia JA, Ortiz F, Manjarrez E, Gutiérrez R. Differential frequency-dependent antidromic resonance of the Schaffer collaterals and mossy fibers. Brain Struct Funct 2015; 221:1793-807. [PMID: 25665800 DOI: 10.1007/s00429-015-1003-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Accepted: 02/04/2015] [Indexed: 10/24/2022]
Abstract
To better understand information transfer along the hippocampal pathways and its plasticity, here we studied the antidromic responses of the dentate gyrus (DG) and CA3 to activation of the mossy fibers and Schaffer collaterals, respectively, in hippocampal slices from naïve and epileptic rats. We applied trains of 600 electrical stimuli at functionally meaningful frequencies (θ, β/γ and γ). The responses of the DG to θ frequency trains underwent rapid potentiation that lasted about 400 stimuli, after which they progressively returned to control value. At β/γ and γ frequencies, however, the initial potentiation was followed by a strong frequency-dependent depression within the first 50 stimuli. In kindled animals, the initial potentiation was stronger than in control preparations and the resonant phase at θ frequency lasted longer. In contrast, CA3 responses were exponentially depressed at all frequencies, but depression was significantly less intense at θ frequency in epileptic preparations. Failure of fibers to fire action potentials could account for some of the aforementioned characteristics, but waveforms of the intracellular action potentials also changed as the field responses did, i.e., half-duration and time-to-peak increased in both structures along the stimulation trains. Noteworthy, block of glutamate and GABA ionotropic receptors prevented resonance and reduced the depression of antidromic responses to β/γ and γ stimulation recorded in the DG, but not in CA3. We show that the different behavior in the information transfer along these pathways depends on the frequency at which action potentials are generated, excitability history and anatomical features, including myelination and tortuosity. In addition, the mossy fibers are endowed with ionotropic receptors and terminal active properties conferring them their sui generis non-passive antidromic responses.
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Affiliation(s)
- Luis M Franco
- Department of Physiology, Biophysics and Neurosciences, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional, Av. Instituto Politécnico Nacional, 07360, Mexico D.F., Mexico
| | - Jesús Q Beltrán
- Department of Physiology, Biophysics and Neurosciences, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional, Av. Instituto Politécnico Nacional, 07360, Mexico D.F., Mexico
| | - Jesús A Tapia
- Institute of Physiology, Benemérita Universidad Autónoma de Puebla, 14 Sur 6301, 72570, Puebla, Mexico
| | - Franco Ortiz
- Department of Pharmacobiology, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional, Calzada de los Tenorios No. 235, 14330, Mexico D.F., Mexico.,Institute of Cell Physiology, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico D.F., Mexico
| | - Elías Manjarrez
- Institute of Physiology, Benemérita Universidad Autónoma de Puebla, 14 Sur 6301, 72570, Puebla, Mexico
| | - Rafael Gutiérrez
- Department of Pharmacobiology, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional, Calzada de los Tenorios No. 235, 14330, Mexico D.F., Mexico.
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138
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Martinello K, Huang Z, Lujan R, Tran B, Watanabe M, Cooper EC, Brown DA, Shah MM. Cholinergic afferent stimulation induces axonal function plasticity in adult hippocampal granule cells. Neuron 2015; 85:346-63. [PMID: 25578363 PMCID: PMC4306544 DOI: 10.1016/j.neuron.2014.12.030] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/08/2014] [Indexed: 01/25/2023]
Abstract
Acetylcholine critically influences hippocampal-dependent learning. Cholinergic fibers innervate hippocampal neuron axons, dendrites, and somata. The effects of acetylcholine on axonal information processing, though, remain unknown. By stimulating cholinergic fibers and making electrophysiological recordings from hippocampal dentate gyrus granule cells, we show that synaptically released acetylcholine preferentially lowered the action potential threshold, enhancing intrinsic excitability and synaptic potential-spike coupling. These effects persisted for at least 30 min after the stimulation paradigm and were due to muscarinic receptor activation. This caused sustained elevation of axonal intracellular Ca2+ via T-type Ca2+ channels, as indicated by two-photon imaging. The enhanced Ca2+ levels inhibited an axonal KV7/M current, decreasing the spike threshold. In support, immunohistochemistry revealed muscarinic M1 receptor, CaV3.2, and KV7.2/7.3 subunit localization in granule cell axons. Since alterations in axonal signaling affect neuronal firing patterns and neurotransmitter release, this is an unreported cellular mechanism by which acetylcholine might, at least partly, enhance cognitive processing. Cholinergic fiber stimulation caused a persistent reduction in the spike threshold Post-synaptic muscarinic receptor activation enhanced axonal CaV3.2 channel activity The sustained Ca2+ entry inhibited axonal KV7 channels, lowering the spike threshold The lower spike threshold increased the propensity for action potential generation
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Affiliation(s)
| | - Zhuo Huang
- UCL School of Pharmacy, University College London, London, WC1N 1AX, UK
| | - Rafael Lujan
- Departamento de Ciencias Medicas, Universidad de Castilla-La Mancha, 02006 Albacete, Spain
| | - Baouyen Tran
- Neurology and Neuroscience, Baylor College of Medicine, TX 77030, USA
| | - Masahiko Watanabe
- Anatomy, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan
| | - Edward C Cooper
- Neurology and Neuroscience, Baylor College of Medicine, TX 77030, USA
| | - David A Brown
- Neuroscience, Physiology and Pharmacology, University College London, London, WC1E 6BT, UK
| | - Mala M Shah
- UCL School of Pharmacy, University College London, London, WC1N 1AX, UK.
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139
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A computational theory of hippocampal function, and tests of the theory: New developments. Neurosci Biobehav Rev 2015; 48:92-147. [DOI: 10.1016/j.neubiorev.2014.11.009] [Citation(s) in RCA: 226] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2014] [Revised: 10/24/2014] [Accepted: 11/12/2014] [Indexed: 01/01/2023]
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140
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Holleman E, Battaglia FP. Memory Consolidation, Replay, and Cortico-Hippocampal Interactions. SPRINGER SERIES IN COMPUTATIONAL NEUROSCIENCE 2015. [DOI: 10.1007/978-1-4939-1969-7_10] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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141
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Temprana SG, Mongiat LA, Yang SM, Trinchero MF, Alvarez DD, Kropff E, Giacomini D, Beltramone N, Lanuza GM, Schinder AF. Delayed coupling to feedback inhibition during a critical period for the integration of adult-born granule cells. Neuron 2014; 85:116-130. [PMID: 25533485 DOI: 10.1016/j.neuron.2014.11.023] [Citation(s) in RCA: 142] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/14/2014] [Indexed: 10/24/2022]
Abstract
Developing granule cells (GCs) of the adult dentate gyrus undergo a critical period of enhanced activity and synaptic plasticity before becoming mature. The impact of developing GCs on the activity of preexisting dentate circuits remains unknown. Here we combine optogenetics, acute slice electrophysiology, and in vivo chemogenetics to activate GCs at different stages of maturation to study the recruitment of local target networks. We show that immature (4-week-old) GCs can efficiently drive distal CA3 targets but poorly activate proximal interneurons responsible for feedback inhibition (FBI). As new GCs transition toward maturity, they reliably recruit GABAergic feedback loops that restrict spiking of neighbor GCs, a mechanism that would promote sparse coding. Such inhibitory loop impinges only weakly in new cohorts of young GCs. A computational model reveals that the delayed coupling of new GCs to FBI could be crucial to achieve a fine-grain representation of novel inputs in the dentate gyrus.
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Affiliation(s)
- Silvio G Temprana
- Laboratory of Neuronal Plasticity, Leloir Institute-CONICET, Av. Patricias Argentinas 435, Buenos Aires, C1405BWE, Argentina
| | - Lucas A Mongiat
- Laboratory of Neuronal Plasticity, Leloir Institute-CONICET, Av. Patricias Argentinas 435, Buenos Aires, C1405BWE, Argentina
| | - Sung M Yang
- Laboratory of Neuronal Plasticity, Leloir Institute-CONICET, Av. Patricias Argentinas 435, Buenos Aires, C1405BWE, Argentina
| | - Mariela F Trinchero
- Laboratory of Neuronal Plasticity, Leloir Institute-CONICET, Av. Patricias Argentinas 435, Buenos Aires, C1405BWE, Argentina
| | - Diego D Alvarez
- Laboratory of Neuronal Plasticity, Leloir Institute-CONICET, Av. Patricias Argentinas 435, Buenos Aires, C1405BWE, Argentina
| | - Emilio Kropff
- Laboratory of Neuronal Plasticity, Leloir Institute-CONICET, Av. Patricias Argentinas 435, Buenos Aires, C1405BWE, Argentina
| | - Damiana Giacomini
- Laboratory of Neuronal Plasticity, Leloir Institute-CONICET, Av. Patricias Argentinas 435, Buenos Aires, C1405BWE, Argentina
| | - Natalia Beltramone
- Laboratory of Neuronal Plasticity, Leloir Institute-CONICET, Av. Patricias Argentinas 435, Buenos Aires, C1405BWE, Argentina
| | - Guillermo M Lanuza
- Laboratory of Developmental Neurobiology, Leloir Institute-CONICET, Av. Patricias Argentinas 435, Buenos Aires, C1405BWE, Argentina
| | - Alejandro F Schinder
- Laboratory of Neuronal Plasticity, Leloir Institute-CONICET, Av. Patricias Argentinas 435, Buenos Aires, C1405BWE, Argentina.
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142
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Crépel V, Mulle C. Physiopathology of kainate receptors in epilepsy. Curr Opin Pharmacol 2014; 20:83-8. [PMID: 25506747 DOI: 10.1016/j.coph.2014.11.012] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Revised: 11/28/2014] [Accepted: 11/28/2014] [Indexed: 10/24/2022]
Abstract
Kainate receptors (KARs) are tetrameric ionotropic glutamate receptors composed of the combinations of five subunits GluK1-GluK5. KARs are structurally related to AMPA receptors but they serve quite distinct functions by regulating the activity of synaptic circuits at presynaptic and postsynaptic sites, through either ionotropic or metabotropic actions. Although kainate is a potent neurotoxin known to induce acute seizures through activation of KARs, the actual role of KARs in the clinically-relevant chronic phase of temporal lobe epilepsy (TLE) has long been elusive. Recent evidences have described pathophysiological mechanisms of heteromeric GluK2/GluK5 KARs in generating recurrent seizures in chronic epilepsy. The role of the other major subunit GluK1 in epileptogenic activity is still a matter of debate. This review will present the current knowledge on the subtype-specific pharmacology of KARs and highlight recent results linking KARs to epileptic conditions.
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Affiliation(s)
- Valérie Crépel
- INSERM, INMED, U901, 13009 Marseille, France; Aix-Marseille Université, UMR 901, 13009 Marseille, France
| | - Christophe Mulle
- Interdisciplinary Institute for Neuroscience, CNRS UMR 5297, France; University of Bordeaux, F-33000 Bordeaux, France.
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143
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Aimone JB, Li Y, Lee SW, Clemenson GD, Deng W, Gage FH. Regulation and function of adult neurogenesis: from genes to cognition. Physiol Rev 2014; 94:991-1026. [PMID: 25287858 DOI: 10.1152/physrev.00004.2014] [Citation(s) in RCA: 421] [Impact Index Per Article: 42.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Adult neurogenesis in the hippocampus is a notable process due not only to its uniqueness and potential impact on cognition but also to its localized vertical integration of different scales of neuroscience, ranging from molecular and cellular biology to behavior. This review summarizes the recent research regarding the process of adult neurogenesis from these different perspectives, with particular emphasis on the differentiation and development of new neurons, the regulation of the process by extrinsic and intrinsic factors, and their ultimate function in the hippocampus circuit. Arising from a local neural stem cell population, new neurons progress through several stages of maturation, ultimately integrating into the adult dentate gyrus network. The increased appreciation of the full neurogenesis process, from genes and cells to behavior and cognition, makes neurogenesis both a unique case study for how scales in neuroscience can link together and suggests neurogenesis as a potential target for therapeutic intervention for a number of disorders.
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Affiliation(s)
- James B Aimone
- Cognitive Modeling Group, Sandia National Laboratories, Albuquerque, New Mexico; and Laboratory of Genetics, Salk Institute for Biological Studies, La Jolla, California
| | - Yan Li
- Cognitive Modeling Group, Sandia National Laboratories, Albuquerque, New Mexico; and Laboratory of Genetics, Salk Institute for Biological Studies, La Jolla, California
| | - Star W Lee
- Cognitive Modeling Group, Sandia National Laboratories, Albuquerque, New Mexico; and Laboratory of Genetics, Salk Institute for Biological Studies, La Jolla, California
| | - Gregory D Clemenson
- Cognitive Modeling Group, Sandia National Laboratories, Albuquerque, New Mexico; and Laboratory of Genetics, Salk Institute for Biological Studies, La Jolla, California
| | - Wei Deng
- Cognitive Modeling Group, Sandia National Laboratories, Albuquerque, New Mexico; and Laboratory of Genetics, Salk Institute for Biological Studies, La Jolla, California
| | - Fred H Gage
- Cognitive Modeling Group, Sandia National Laboratories, Albuquerque, New Mexico; and Laboratory of Genetics, Salk Institute for Biological Studies, La Jolla, California
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144
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Hummos A, Franklin CC, Nair SS. Intrinsic mechanisms stabilize encoding and retrieval circuits differentially in a hippocampal network model. Hippocampus 2014; 24:1430-48. [PMID: 24978936 PMCID: PMC9121438 DOI: 10.1002/hipo.22324] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 06/13/2014] [Accepted: 06/16/2014] [Indexed: 01/09/2023]
Abstract
Acetylcholine regulates memory encoding and retrieval by inducing the hippocampus to switch between pattern separation and pattern completion modes. However, both processes can introduce significant variations in the level of network activity and potentially cause a seizure-like spread of excitation. Thus, mechanisms that keep network excitation within certain bounds are necessary to prevent such instability. We developed a biologically realistic computational model of the hippocampus to investigate potential intrinsic mechanisms that might stabilize the network dynamics during encoding and retrieval. The model was developed by matching experimental data, including neuronal behavior, synaptic current dynamics, network spatial connectivity patterns, and short-term synaptic plasticity. Furthermore, it was constrained to perform pattern completion and separation under the effects of acetylcholine. The model was then used to investigate the role of short-term synaptic depression at the recurrent synapses in CA3, and inhibition by basket cell (BC) interneurons and oriens lacunosum-moleculare (OLM) interneurons in stabilizing these processes. Results showed that when CA3 was considered in isolation, inhibition solely by BCs was not sufficient to control instability. However, both inhibition by OLM cells and short-term depression at the recurrent CA3 connections stabilized the network activity. In the larger network including the dentate gyrus, the model suggested that OLM inhibition could control the network during high cholinergic levels while depressing synapses at the recurrent CA3 connections were important during low cholinergic states. Our results demonstrate that short-term plasticity is a critical property of the network that enhances its robustness. Furthermore, simulations suggested that the low and high cholinergic states can each produce runaway excitation through unique mechanisms and different pathologies. Future studies aimed at elucidating the circuit mechanisms of epilepsy could benefit from considering the two modulatory states separately.
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Affiliation(s)
- Ali Hummos
- Department of Health Informatics, University of Missouri, Columbia, Missouri
- Department of Psychiatry, University of Missouri, Columbia, Missouri
| | - Charles C. Franklin
- Department of Electrical & Computer Engineering, University of Missouri, Columbia, Missouri
| | - Satish S. Nair
- Department of Electrical & Computer Engineering, University of Missouri, Columbia, Missouri
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145
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Evstratova A, Chamberland S, Faundez V, Tóth K. Vesicles derived via AP-3-dependent recycling contribute to asynchronous release and influence information transfer. Nat Commun 2014; 5:5530. [PMID: 25410111 PMCID: PMC4239664 DOI: 10.1038/ncomms6530] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 10/10/2014] [Indexed: 12/21/2022] Open
Abstract
Action potentials trigger synchronous and asynchronous neurotransmitter release. Temporal properties of both types of release could be altered in an activity-dependent manner. While the effects of activity-dependent changes in synchronous release on postsynaptic signal integration have been studied, the contribution of asynchronous release to information transfer during natural stimulus patterns is unknown. Here we find that during trains of stimulations, asynchronous release contributes to the precision of action potential firing. Our data show that this form of release is selectively diminished in AP-3b2 KO animals, which lack functional neuronal AP-3, an adaptor protein regulating vesicle formation from endosomes generated during bulk endocytosis. We find that in the absence of neuronal AP-3, asynchronous release is attenuated and the activity-dependent increase in the precision of action potential timing is compromised. Lack of asynchronous release decreases the capacity of synaptic information transfer and renders synaptic communication less reliable in response to natural stimulus patterns.
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Affiliation(s)
- Alesya Evstratova
- Department of Psychiatry and Neuroscience, Quebec Mental Health Institute, Université Laval, Quebec City, Quebec, Canada G1J 2G3
| | - Simon Chamberland
- Department of Psychiatry and Neuroscience, Quebec Mental Health Institute, Université Laval, Quebec City, Quebec, Canada G1J 2G3
| | - Victor Faundez
- Department of Cell Biology, Emory University, Atlanta, Georgia 30322, USA
| | - Katalin Tóth
- Department of Psychiatry and Neuroscience, Quebec Mental Health Institute, Université Laval, Quebec City, Quebec, Canada G1J 2G3
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146
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Ghitani N, Bayguinov PO, Ma Y, Jackson MB. Single-trial imaging of spikes and synaptic potentials in single neurons in brain slices with genetically encoded hybrid voltage sensor. J Neurophysiol 2014; 113:1249-59. [PMID: 25411462 DOI: 10.1152/jn.00691.2014] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Genetically encoded voltage sensors expand the optogenetics toolkit into the important realm of electrical recording, enabling researchers to study the dynamic activity of complex neural circuits in real time. However, these probes have thus far performed poorly when tested in intact neural circuits. Hybrid voltage sensors (hVOS) enable the imaging of voltage by harnessing the resonant energy transfer that occurs between a genetically encoded component, a membrane-tethered fluorescent protein that serves as a donor, and a small charged molecule, dipicrylamine, which serves as an acceptor. hVOS generates optical signals as a result of voltage-induced changes in donor-acceptor distance. We expressed the hVOS probe in mouse brain by in utero electroporation and in transgenic mice with a neuronal promoter. Under conditions favoring sparse labeling we could visualize single-labeled neurons. hVOS imaging reported electrically evoked fluorescence changes from individual neurons in slices from entorhinal cortex, somatosensory cortex, and hippocampus. These fluorescence signals tracked action potentials in individual neurons in a single trial with excellent temporal fidelity, producing changes that exceeded background noise by as much as 16-fold. Subthreshold synaptic potentials were detected in single trials in multiple distinct cells simultaneously. We followed signal propagation between different cells within one field of view and between dendrites and somata of the same cell. hVOS imaging thus provides a tool for high-resolution recording of electrical activity from genetically targeted cells in intact neuronal circuits.
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Affiliation(s)
- Nima Ghitani
- Neuroscience Training Program, University of Wisconsin, Madison, Wisconsin
| | - Peter O Bayguinov
- Department of Neuroscience, University of Wisconsin, Madison, Wisconsin
| | - Yihe Ma
- Physiology Graduate Training Program, University of Wisconsin, Madison, Wisconsin; and
| | - Meyer B Jackson
- Neuroscience Training Program, University of Wisconsin, Madison, Wisconsin; Physiology Graduate Training Program, University of Wisconsin, Madison, Wisconsin; and Department of Neuroscience, University of Wisconsin, Madison, Wisconsin
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147
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Chamberland S, Evstratova A, Tóth K. Interplay between synchronization of multivesicular release and recruitment of additional release sites support short-term facilitation at hippocampal mossy fiber to CA3 pyramidal cells synapses. J Neurosci 2014; 34:11032-47. [PMID: 25122902 PMCID: PMC6705252 DOI: 10.1523/jneurosci.0847-14.2014] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 06/07/2014] [Accepted: 06/27/2014] [Indexed: 11/21/2022] Open
Abstract
Synaptic short-term plasticity is a key regulator of neuronal communication and is controlled via various mechanisms. A well established property of mossy fiber to CA3 pyramidal cell synapses is the extensive short-term facilitation during high-frequency bursts. We investigated the mechanisms governing facilitation using a combination of whole-cell electrophysiological recordings, electrical minimal stimulation, and random-access two-photon microscopy in acute mouse hippocampal slices. Two distinct presynaptic mechanisms were involved in short-term facilitation, with their relative contribution dependent on extracellular calcium concentration. The synchronization of multivesicular release was observed during trains of facilitating EPSCs recorded in 1.2 mM external Ca(2+) ([Ca(2+)]e). Indeed, covariance analysis revealed a gradual augmentation in quantal size during trains of EPSCs, and application of the low-affinity glutamate receptor antagonist γ-D-glutamylglycine showed an increase in cleft glutamate concentration during paired-pulse stimulation. Whereas synchronization of multivesicular release contributed to the facilitation in 1.2 mM [Ca(2+)]e, variance-mean analysis showed that recruitment of more release sites (N) was likely to account for the larger facilitation observed in 2.5 mM [Ca(2+)]e. Furthermore, this increase in N could be promoted by calcium microdomains of heterogeneous amplitudes observed in single mossy fiber boutons. Our findings suggest that the combination of multivesicular release and the recruitment of additional release sites act together to increase glutamate release during burst activity. This is supported by the compartmentalized spatial profile of calcium elevations in boutons and helps to expand the dynamic range of mossy fibers information transfer.
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Affiliation(s)
- Simon Chamberland
- Quebec Mental Health Institute, Department of Psychiatry and Neuroscience, Laval University, Quebec City, Quebec, Canada, G1J 2G3
| | - Alesya Evstratova
- Quebec Mental Health Institute, Department of Psychiatry and Neuroscience, Laval University, Quebec City, Quebec, Canada, G1J 2G3
| | - Katalin Tóth
- Quebec Mental Health Institute, Department of Psychiatry and Neuroscience, Laval University, Quebec City, Quebec, Canada, G1J 2G3
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148
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Petrantonakis PC, Poirazi P. A compressed sensing perspective of hippocampal function. Front Syst Neurosci 2014; 8:141. [PMID: 25152718 PMCID: PMC4126371 DOI: 10.3389/fnsys.2014.00141] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Accepted: 07/22/2014] [Indexed: 01/05/2023] Open
Abstract
Hippocampus is one of the most important information processing units in the brain. Input from the cortex passes through convergent axon pathways to the downstream hippocampal subregions and, after being appropriately processed, is fanned out back to the cortex. Here, we review evidence of the hypothesis that information flow and processing in the hippocampus complies with the principles of Compressed Sensing (CS). The CS theory comprises a mathematical framework that describes how and under which conditions, restricted sampling of information (data set) can lead to condensed, yet concise, forms of the initial, subsampled information entity (i.e., of the original data set). In this work, hippocampus related regions and their respective circuitry are presented as a CS-based system whose different components collaborate to realize efficient memory encoding and decoding processes. This proposition introduces a unifying mathematical framework for hippocampal function and opens new avenues for exploring coding and decoding strategies in the brain.
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Affiliation(s)
| | - Panayiota Poirazi
- Computational Biology Lab, Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-HellasHeraklion, Greece
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149
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Rennó-Costa C, Lisman JE, Verschure PFMJ. A signature of attractor dynamics in the CA3 region of the hippocampus. PLoS Comput Biol 2014; 10:e1003641. [PMID: 24854425 PMCID: PMC4031055 DOI: 10.1371/journal.pcbi.1003641] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Accepted: 04/09/2014] [Indexed: 12/02/2022] Open
Abstract
The notion of attractor networks is the leading hypothesis for how associative memories are stored and recalled. A defining anatomical feature of such networks is excitatory recurrent connections. These "attract" the firing pattern of the network to a stored pattern, even when the external input is incomplete (pattern completion). The CA3 region of the hippocampus has been postulated to be such an attractor network; however, the experimental evidence has been ambiguous, leading to the suggestion that CA3 is not an attractor network. In order to resolve this controversy and to better understand how CA3 functions, we simulated CA3 and its input structures. In our simulation, we could reproduce critical experimental results and establish the criteria for identifying attractor properties. Notably, under conditions in which there is continuous input, the output should be "attracted" to a stored pattern. However, contrary to previous expectations, as a pattern is gradually "morphed" from one stored pattern to another, a sharp transition between output patterns is not expected. The observed firing patterns of CA3 meet these criteria and can be quantitatively accounted for by our model. Notably, as morphing proceeds, the activity pattern in the dentate gyrus changes; in contrast, the activity pattern in the downstream CA3 network is attracted to a stored pattern and thus undergoes little change. We furthermore show that other aspects of the observed firing patterns can be explained by learning that occurs during behavioral testing. The CA3 thus displays both the learning and recall signatures of an attractor network. These observations, taken together with existing anatomical and behavioral evidence, make the strong case that CA3 constructs associative memories based on attractor dynamics.
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Affiliation(s)
- César Rennó-Costa
- Universitat Pompeu Fabra, Synthetic, Perceptive, Emotive and Cognitive Systems group (SPECS), Barcelona, Spain
- Federal University of Rio Grande do Norte (UFRN), Brain Institute (ICe), Natal, Rio Grande do Norte, Brazil
| | - John E. Lisman
- Brandeis University, Biology Department & Volen Center for Complex Systems, Waltham, Massachusetts, United States of America
| | - Paul F. M. J. Verschure
- Universitat Pompeu Fabra, Synthetic, Perceptive, Emotive and Cognitive Systems group (SPECS), Barcelona, Spain
- Catalan Institute of Advanced Research (ICREA), Passeig Lluís Companys 23, Barcelona, Spain
- Universitat Pompeu Fabra, Center of Autonomous Systems and Neurorobotics (NRAS), Barcelona, Spain
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150
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Mossy fiber-evoked subthreshold responses induce timing-dependent plasticity at hippocampal CA3 recurrent synapses. Proc Natl Acad Sci U S A 2014; 111:4303-8. [PMID: 24550458 DOI: 10.1073/pnas.1317667111] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Dentate granule cells exhibit exceptionally low levels of activity and rarely elicit action potentials in targeted CA3 pyramidal cells. It is thus unclear how such weak input from the granule cells sustains adequate levels of synaptic plasticity in the targeted CA3 network. We report that subthreshold potentials evoked by mossy fibers are sufficient to induce synaptic plasticity between CA3 pyramidal cells, thereby complementing the sparse action potential discharge. Repetitive pairing of a CA3-CA3 recurrent synaptic response with a subsequent subthreshold mossy fiber response induced long-term potentiation at CA3 recurrent synapses in rat hippocampus in vitro. Reversing the timing of the inputs induced long-term depression. The underlying mechanism depends on a passively conducted giant excitatory postsynaptic potential evoked by a mossy fiber that enhances NMDA receptor-mediated current at active CA3 recurrent synapses by relieving magnesium block. The resulting NMDA spike generates a supralinear depolarization that contributes to synaptic plasticity in hippocampal neuronal ensembles implicated in memory.
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