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Quintanilla J, Jia Y, Pruess BS, Chavez J, Gall CM, Lynch G, Gunn BG. Pre- versus Post-synaptic Forms of LTP in Two Branches of the Same Hippocampal Afferent. J Neurosci 2024; 44:e1449232024. [PMID: 38326038 PMCID: PMC10919254 DOI: 10.1523/jneurosci.1449-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 12/18/2023] [Accepted: 01/22/2024] [Indexed: 02/09/2024] Open
Abstract
There has been considerable controversy about pre- versus postsynaptic expression of memory-related long-term potentiation (LTP), with corresponding disputes about underlying mechanisms. We report here an instance in male mice, in which both types of potentiation are expressed but in separate branches of the same hippocampal afferent. Induction of LTP in the dentate gyrus (DG) branch of the lateral perforant path (LPP) reduces paired-pulse facilitation, is blocked by antagonism of cannabinoid receptor type 1, and is not affected by suppression of postsynaptic actin polymerization. These observations are consistent with presynaptic expression. The opposite pattern of results was obtained in the LPP branch that innervates the distal dendrites of CA3: LTP did not reduce paired-pulse facilitation, was unaffected by the cannabinoid receptor blocker, and required postsynaptic actin filament assembly. Differences in the two LPP termination sites were also noted for frequency facilitation of synaptic responses, an effect that was reproduced in a two-step simulation by small adjustments to vesicle release dynamics. These results indicate that different types of glutamatergic neurons impose different forms of filtering and synaptic plasticity on their afferents. They also suggest that inputs are routed to, and encoded by, different sites within the hippocampus depending upon the pattern of activity arriving over the parent axon.
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Affiliation(s)
- J Quintanilla
- Department of Anatomy & Neurobiology, University of California, Irvine, California 92697
| | - Y Jia
- Department of Anatomy & Neurobiology, University of California, Irvine, California 92697
| | - B S Pruess
- Department of Anatomy & Neurobiology, University of California, Irvine, California 92697
| | - J Chavez
- Department of Anatomy & Neurobiology, University of California, Irvine, California 92697
| | - C M Gall
- Department of Anatomy & Neurobiology, University of California, Irvine, California 92697
- Neurobiology & Behavior, University of California, Irvine, California 92697
| | - G Lynch
- Department of Anatomy & Neurobiology, University of California, Irvine, California 92697
- Psychiatry & Human Behavior, University of California, Irvine, California 92697
| | - B G Gunn
- Department of Anatomy & Neurobiology, University of California, Irvine, California 92697
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2
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Kocsis B, Pittman-Polletta B. Neuropsychiatric consequences of COVID-19 related olfactory dysfunction: could non-olfactory cortical-bound inputs from damaged olfactory bulb also contribute to cognitive impairment? Front Neurosci 2023; 17:1164042. [PMID: 37425004 PMCID: PMC10323442 DOI: 10.3389/fnins.2023.1164042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Accepted: 05/24/2023] [Indexed: 07/11/2023] Open
Affiliation(s)
- Bernat Kocsis
- Department of Psychiatry, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA, United States
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3
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Quintanilla J, Jia Y, Lauterborn JC, Pruess BS, Le AA, Cox CD, Gall CM, Lynch G, Gunn BG. Novel types of frequency filtering in the lateral perforant path projections to dentate gyrus. J Physiol 2022; 600:3865-3896. [PMID: 35852108 PMCID: PMC9513824 DOI: 10.1113/jp283012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Accepted: 06/26/2022] [Indexed: 11/08/2022] Open
Abstract
Despite its evident importance to learning theory and models, the manner in which the lateral perforant path (LPP) transforms signals from entorhinal cortex to hippocampus is not well understood. The present studies measured synaptic responses in the dentate gyrus (DG) of adult mouse hippocampal slices during different patterns of LPP stimulation. Theta (5 Hz) stimulation produced a modest within-train facilitation that was markedly enhanced at the level of DG output. Gamma (50 Hz) activation resulted in a singular pattern with initial synaptic facilitation being followed by a progressively greater depression. DG output was absent after only two pulses. Reducing release probability with low extracellular calcium instated frequency facilitation to gamma stimulation while long-term potentiation, which increases release by LPP terminals, enhanced within-train depression. Relatedly, per terminal concentrations of VGLUT2, a vesicular glutamate transporter associated with high release probability, were much greater in the LPP than in CA3-CA1 connections. Attempts to circumvent the potent gamma filter using a series of short (three-pulse) 50 Hz trains spaced by 200 ms were only partially successful: composite responses were substantially reduced after the first burst, an effect opposite to that recorded in field CA1. The interaction between bursts was surprisingly persistent (>1.0 s). Low calcium improved throughput during theta/gamma activation but buffering of postsynaptic calcium did not. In all, presynaptic specializations relating to release probability produce an unusual but potent type of frequency filtering in the LPP. Patterned burst input engages a different type of filter with substrates that are also likely to be located presynaptically. KEY POINTS: The lateral perforant path (LPP)-dentate gyrus (DG) synapse operates as a low-pass filter, where responses to a train of 50 Hz, γ frequency activation are greatly suppressed. Activation with brief bursts of γ frequency information engages a secondary filter that persists for prolonged periods (lasting seconds). Both forms of LPP frequency filtering are influenced by presynaptic, as opposed to postsynaptic, processes; this contrasts with other hippocampal synapses. LPP frequency filtering is modified by the unique presynaptic long-term potentiation at this synapse. Computational simulations indicate that presynaptic factors associated with release probability and vesicle recycling may underlie the potent LPP-DG frequency filtering.
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Affiliation(s)
- Julian Quintanilla
- Departments of Anatomy & Neurobiology, University of California, Irvine, CA, USA
| | - Yousheng Jia
- Departments of Anatomy & Neurobiology, University of California, Irvine, CA, USA
| | - Julie C Lauterborn
- Departments of Anatomy & Neurobiology, University of California, Irvine, CA, USA
| | - Benedict S Pruess
- Departments of Anatomy & Neurobiology, University of California, Irvine, CA, USA
| | - Aliza A Le
- Departments of Anatomy & Neurobiology, University of California, Irvine, CA, USA
| | - Conor D Cox
- Departments of Anatomy & Neurobiology, University of California, Irvine, CA, USA
| | - Christine M Gall
- Departments of Anatomy & Neurobiology, University of California, Irvine, CA, USA.,Departments of Neurobiology & Behavior, University of California, Irvine, CA, USA
| | - Gary Lynch
- Departments of Anatomy & Neurobiology, University of California, Irvine, CA, USA.,Departments of Psychiatry & Human Behavior, University of California, Irvine, CA, USA
| | - Benjamin G Gunn
- Departments of Anatomy & Neurobiology, University of California, Irvine, CA, USA
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4
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Roysommuti S, Wyss JM. Brain-Derived Neurotrophic Factor Potentiates Entorhinal-Dentate but not Hippocampus CA1 Pathway in Adult Male Rats: A Mechanism of Taurine-Modulated BDNF on Learning and Memory. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1370:369-379. [PMID: 35882811 PMCID: PMC9467516 DOI: 10.1007/978-3-030-93337-1_35] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Taurine plays an important role in neural growth and function from early to adult life, particularly in learning and memory via BDNF action. This study tested the hypothesis that BDNF differentially potentiates entorhinal-hippocampal synaptic transmission in vivo in adult rats. In anesthetized male Sprague-Dawley rats, a stainless steel recording electrode with an attached microinjector was placed into CA1 and the dentate gyrus to record fEPSP, and a paired stainless steel electrode was inserted into entorhinal cortex for continuous paired-pulse stimulation of that brain region. In the dentate gyrus, microinjection of BDNF resulted in a gradual increase in the peak slope of the fEPSP. Following the infusion, the peak fEPSP began to rise in about 8 min, reached a maximum of 120 ± 2% (from baseline) by about 20 min, and remained near peak elevation (~115%) for more than 30 min. In contrast, the same dose of BDNF when injected into CA1 had no consistent effect on fEPSP slopes in the CA1. Further, an equimolar cytochrome C (horse heart) infusion had no significant effect on fEPSP slopes in either the dentate gyrus or CA1. The potentiation effect of BDNF in the dentate gyrus is consistent with a significant increase in power spectral density of dentate gyrus field potentials at 70-200 Hz, but not at frequencies below 70 Hz. In addition, the CA1 power spectral density was not affected by BDNF (compared to cytochrome C). These data indicate that in vivo BDNF potentiates entorhinal-hippocampal synaptic transmission in dentate gyrus, but not in CA1.
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Affiliation(s)
- Sanya Roysommuti
- Department of Cell, Developmental and Integrative Biology, School of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA.
- Department of Physiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.
| | - James Michael Wyss
- Department of Cell, Developmental and Integrative Biology, School of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
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5
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Le AA, Quintanilla J, Amani M, Piomelli D, Lynch G, Gall CM. Persistent sexually dimorphic effects of adolescent THC exposure on hippocampal synaptic plasticity and episodic memory in rodents. Neurobiol Dis 2022; 162:105565. [PMID: 34838664 DOI: 10.1016/j.nbd.2021.105565] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 10/04/2021] [Accepted: 11/23/2021] [Indexed: 01/01/2023] Open
Abstract
There is evidence that cannabis use during adolescence leads to memory and cognitive problems in young adulthood but little is known about effects of early life cannabis exposure on synaptic operations that are critical for encoding and organizing information. We report here that a 14-day course of daily Δ9-tetrahydrocannabinol treatments administered to adolescent rats and mice (aTHC) leads to profound but selective deficits in synaptic plasticity in two axonal systems in female, and to lesser extent male, hippocampus as assessed in adulthood. Adolescent-THC exposure did not alter basic synaptic transmission (input/output curves) and had only modest effects on frequency facilitation. Nevertheless, aTHC severely impaired the endocannabinoid-dependent long-term potentiation in the lateral perforant path in females of both species, and in male mice; this was reliably associated with impaired acquisition of a component of episodic memory that depends on lateral perforant path function. Potentiation in the Schaffer-commissural (S-C) projection to field CA1 was disrupted by aTHC treatment in females only and this was associated with both a deficit in estrogen effects on S-C synaptic responses and impairments to CA1-dependent spatial (object location) memory. In all the results demonstrate sexually dimorphic and projection system-specific effects of aTHC exposure that could underlie discrete effects of early life cannabinoid usage on adult cognitive function. Moreover they suggest that some of the enduring, sexually dimorphic effects of cannabis use reflect changes in synaptic estrogen action.
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Affiliation(s)
- Aliza A Le
- Departments of Anatomy & Neurobiology, University of California, Irvine, CA 92697, United States of America
| | - Julian Quintanilla
- Departments of Anatomy & Neurobiology, University of California, Irvine, CA 92697, United States of America
| | - Mohammad Amani
- Departments of Anatomy & Neurobiology, University of California, Irvine, CA 92697, United States of America
| | - Daniele Piomelli
- Departments of Anatomy & Neurobiology, University of California, Irvine, CA 92697, United States of America
| | - Gary Lynch
- Departments of Anatomy & Neurobiology, University of California, Irvine, CA 92697, United States of America; Departments of Psychiatry & Human Behavior, University of California, Irvine, CA 92868, United States of America.
| | - Christine M Gall
- Departments of Anatomy & Neurobiology, University of California, Irvine, CA 92697, United States of America; Departments of Neurobiology & Behavior, University of California, Irvine, CA 92697, United States of America.
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6
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Bin Ibrahim MZ, Benoy A, Sajikumar S. Long-term plasticity in the hippocampus: maintaining within and 'tagging' between synapses. FEBS J 2021; 289:2176-2201. [PMID: 34109726 DOI: 10.1111/febs.16065] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 05/15/2021] [Accepted: 06/01/2021] [Indexed: 12/11/2022]
Abstract
Synapses between neurons are malleable biochemical structures, strengthening and diminishing over time dependent on the type of information they receive. This phenomenon known as synaptic plasticity underlies learning and memory, and its different forms, long-term potentiation (LTP) and long-term depression (LTD), perform varied cognitive roles in reinforcement, relearning and associating memories. Moreover, both LTP and LTD can exist in an early transient form (early-LTP/LTD) or a late persistent form (late-LTP/LTD), which are triggered by different induction protocols, and also differ in their dependence on protein synthesis and the involvement of key molecular players. Beyond homosynaptic modifications, synapses can also interact with one another. This is encapsulated in the synaptic tagging and capture hypothesis (STC), where synapses expressing early-LTP/LTD present a 'tag' that can capture the protein synthesis products generated during a temporally proximal late-LTP/LTD induction. This 'tagging' phenomenon forms the framework of synaptic interactions in various conditions and accounts for the cellular basis of the time-dependent associativity of short-lasting and long-lasting memories. All these synaptic modifications take place under controlled neuronal conditions, regulated by subcellular elements such as epigenetic regulation, proteasomal degradation and neuromodulatory signals. Here, we review current understanding of the different forms of synaptic plasticity and its regulatory mechanisms in the hippocampus, a brain region critical for memory formation. We also discuss expression of plasticity in hippocampal CA2 area, a long-overlooked narrow hippocampal subfield and the behavioural correlate of STC. Lastly, we put forth perspectives for an integrated view of memory representation in synapses.
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Affiliation(s)
- Mohammad Zaki Bin Ibrahim
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.,Life Sciences Institute Neurobiology Programme, National University of Singapore, Singapore
| | - Amrita Benoy
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.,Life Sciences Institute Neurobiology Programme, National University of Singapore, Singapore
| | - Sreedharan Sajikumar
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.,Life Sciences Institute Neurobiology Programme, National University of Singapore, Singapore.,Healthy Longevity Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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7
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Amani M, Lauterborn JC, Le AA, Cox BM, Wang W, Quintanilla J, Cox CD, Gall CM, Lynch G. Rapid Aging in the Perforant Path Projections to the Rodent Dentate Gyrus. J Neurosci 2021; 41:2301-2312. [PMID: 33514675 PMCID: PMC8018768 DOI: 10.1523/jneurosci.2376-20.2021] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 01/04/2021] [Accepted: 01/16/2021] [Indexed: 12/15/2022] Open
Abstract
Why layers II/III of entorhinal cortex (EC) deteriorate in advance of other regions during the earliest stages of Alzheimer's disease is poorly understood. Failure of retrograde trophic support from synapses to cell bodies is a common cause of neuronal atrophy, and we accordingly tested for early-life deterioration in projections of rodent layer II EC neurons. Using electrophysiology and quantitative imaging, changes in EC terminals during young adulthood were evaluated in male rats and mice. Field excitatory postsynaptic potentials, input/output curves, and frequency following capacity by lateral perforant path (LPP) projections from lateral EC to dentate gyrus were unchanged from 3 to 8-10 months of age. In contrast, the unusual presynaptic form of long-term potentiation (LTP) expressed by the LPP was profoundly impaired by 8 months in rats and mice. This impairment was accompanied by a reduction in the spine to terminal endocannabinoid signaling needed for LPP-LTP induction and was offset by an agent that enhances signaling. There was a pronounced age-related increase in synaptophysin within LPP terminals, an effect suggestive of incipient pathology. Relatedly, presynaptic levels of TrkB-receptors mediating retrograde trophic signaling-were reduced in the LPP terminal field. LTP and TrkB content were also reduced in the medial perforant path of 8- to 10-month-old rats. As predicted, performance on an LPP-dependent episodic memory task declined by late adulthood. We propose that memory-related synaptic plasticity in EC projections is unusually sensitive to aging, which predisposes EC neurons to pathogenesis later in life.SIGNIFICANCE STATEMENT Neurons within human superficial entorhinal cortex are particularly vulnerable to effects of aging and Alzheimer's disease, although why this is the case is not understood. Here we report that perforant path projections from layer II entorhinal cortex to the dentate gyrus exhibit rapid aging in rodents, including reduced synaptic plasticity and abnormal protein content by 8-10 months of age. Moreover, there was a substantial decline in the performance of an episodic memory task that depends on entorhinal cortical projections at the same ages. Overall, the results suggest that the loss of plasticity and related trophic signaling predispose the entorhinal neurons to functional decline in relatively young adulthood.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Gary Lynch
- Departments of Anatomy & Neurobiology
- Psychiatry & Human Behavior, University of California, Irvine, Irvine, California 92697
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8
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Ribeiro M, Brigas HC, Temido-Ferreira M, Pousinha PA, Regen T, Santa C, Coelho JE, Marques-Morgado I, Valente CA, Omenetti S, Stockinger B, Waisman A, Manadas B, Lopes LV, Silva-Santos B, Ribot JC. Meningeal γδ T cell-derived IL-17 controls synaptic plasticity and short-term memory. Sci Immunol 2020; 4:4/40/eaay5199. [PMID: 31604844 DOI: 10.1126/sciimmunol.aay5199] [Citation(s) in RCA: 173] [Impact Index Per Article: 43.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Accepted: 09/03/2019] [Indexed: 12/12/2022]
Abstract
The notion of "immune privilege" of the brain has been revised to accommodate its infiltration, at steady state, by immune cells that participate in normal neurophysiology. However, the immune mechanisms that regulate learning and memory remain poorly understood. Here, we show that noninflammatory interleukin-17 (IL-17) derived from a previously unknown fetal-derived meningeal-resident γδ T cell subset promotes cognition. When tested in classical spatial learning paradigms, mice lacking γδ T cells or IL-17 displayed deficient short-term memory while retaining long-term memory. The plasticity of glutamatergic synapses was reduced in the absence of IL-17, resulting in impaired long-term potentiation in the hippocampus. Conversely, IL-17 enhanced glial cell production of brain-derived neurotropic factor, whose exogenous provision rescued the synaptic and behavioral phenotypes of IL-17-deficient animals. Together, our work provides previously unknown clues on the mechanisms that regulate short-term versus long-term memory and on the evolutionary and functional link between the immune and nervous systems.
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Affiliation(s)
- Miguel Ribeiro
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - Helena C Brigas
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - Mariana Temido-Ferreira
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - Paula A Pousinha
- Institut de Pharmacologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique, Université de Côte d'Azur, Nice, France
| | - Tommy Regen
- Institute for Molecular Medicine, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Cátia Santa
- Center for Neuroscience and Cell Biology, Universidade de Coimbra, Coimbra, Portugal.,Institute for Interdisciplinary Research, Universidade de Coimbra, Coimbra, Portugal
| | - Joana E Coelho
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - Inês Marques-Morgado
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - Cláudia A Valente
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | | | | | - Ari Waisman
- Institute for Molecular Medicine, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Bruno Manadas
- Center for Neuroscience and Cell Biology, Universidade de Coimbra, Coimbra, Portugal
| | - Luísa V Lopes
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - Bruno Silva-Santos
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal.
| | - Julie C Ribot
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal.
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Palomero-Gallagher N, Kedo O, Mohlberg H, Zilles K, Amunts K. Multimodal mapping and analysis of the cyto- and receptorarchitecture of the human hippocampus. Brain Struct Funct 2020; 225:881-907. [PMID: 31955294 PMCID: PMC7166210 DOI: 10.1007/s00429-019-02022-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 12/26/2019] [Indexed: 12/29/2022]
Abstract
The human hippocampal formation is relevant for various aspects of memory and learning, and the different hippocampal regions are differentially affected by neuropsychiatric disorders. Therefore, the hippocampal formation has been subject of numerous cytoarchitectonic and other mapping studies, which resulted in divergent parcellation schemes. To understand the principles of hippocampal architecture, it is necessary to integrate different levels of hippocampal organisation, going beyond one modality. We here applied a multimodal mapping approach combining cyto- and multi-receptorarchitectonic analyses, and generated probabilistic maps in stereotaxic space of the identified regions. Cytoarchitecture in combination with the regional and laminar distribution of 15 neurotransmitter receptors visualized by in vitro receptor autoradiography were analysed in seven hemispheres from 6 unfixed shock frozen and serially sectioned brains. Cytoarchitectonic delineations for generation of probabilistic maps were carried out on histological sections from ten fixed, paraffin embedded and serially sectioned brains. Nine cyto- and receptorarchitectonically distinct regions were identified within the hippocampal formation (i.e., fascia dentata, cornu Ammonis (CA) regions 1-4, prosubiculum, subiculum proper, presubiculum and parasubiculum), as well as the hippocampal-amygdaloid transition area and the periallocortical transsubiculum. Subsequently generated probabilistic maps quantify intersubject variability in the size and extent of these cyto- and receptorarchitectonically distinct regions. The regions did not differ in their volume between the hemispheres and gender. Receptor mapping revealed additional subdivisions which could not be detected by cytoarchitectonic analysis alone. They correspond to parcellations previously found in immunohistochemical and connectivity studies. The multimodal approach enabled the definition of regions not consistently reported, e.g., CA4 region or prosubiculum. The ensuing detailed probabilistic maps of the hippocampal formation constitute the basis for future architectonically informed analyses of in vivo neuroimaging studies.
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Affiliation(s)
- Nicola Palomero-Gallagher
- Institute of Neuroscience and Medicine (INM-1), Research Centre Jülich, 52425, Jülich, Germany.
- Department of Psychiatry, Psychotherapy and Psychosomatics, Medical Faculty, RWTH Aachen University, Aachen, Germany.
- C. & O. Vogt Institute for Brain Research, Heinrich-Heine-University, 40225, Düsseldorf, Germany.
| | - Olga Kedo
- Institute of Neuroscience and Medicine (INM-1), Research Centre Jülich, 52425, Jülich, Germany
| | - Hartmut Mohlberg
- Institute of Neuroscience and Medicine (INM-1), Research Centre Jülich, 52425, Jülich, Germany
| | - Karl Zilles
- Institute of Neuroscience and Medicine (INM-1), Research Centre Jülich, 52425, Jülich, Germany
- JARA-BRAIN, Jülich-Aachen Research Alliance, Jülich, Germany
| | - Katrin Amunts
- Institute of Neuroscience and Medicine (INM-1), Research Centre Jülich, 52425, Jülich, Germany
- C. & O. Vogt Institute for Brain Research, Heinrich-Heine-University, 40225, Düsseldorf, Germany
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10
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Carver CM, Hastings SD, Cook ME, Shapiro MS. Functional responses of the hippocampus to hyperexcitability depend on directed, neuron-specific KCNQ2 K + channel plasticity. Hippocampus 2019; 30:435-455. [PMID: 31621989 DOI: 10.1002/hipo.23163] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 07/24/2019] [Accepted: 08/30/2019] [Indexed: 12/14/2022]
Abstract
M-type (KCNQ2/3) K+ channels play dominant roles in regulation of active and passive neuronal discharge properties such as resting membrane potential, spike-frequency adaptation, and hyper-excitatory states. However, plasticity of M-channel expression and function in nongenetic forms of epileptogenesis are still not well understood. Using transgenic mice with an EGFP reporter to detect expression maps of KCNQ2 mRNA, we assayed hyperexcitability-induced alterations in KCNQ2 transcription across subregions of the hippocampus. Pilocarpine and pentylenetetrazol chemoconvulsant models of seizure induction were used, and brain tissue examined 48 hr later. We observed increases in KCNQ2 mRNA in CA1 and CA3 pyramidal neurons after chemoconvulsant-induced hyperexcitability at 48 hr, but no significant change was observed in dentate gyrus (DG) granule cells. Using chromogenic in situ hybridization assays, changes to KCNQ3 transcription were not detected after hyper-excitation challenge, but the results for KCNQ2 paralleled those using the KCNQ2-mRNA reporter mice. In mice 7 days after pilocarpine challenge, levels of KCNQ2 mRNA were similar in all regions to those from control mice. In brain-slice electrophysiology recordings, CA1 pyramidal neurons demonstrated increased M-current amplitudes 48 hr after hyperexcitability; however, there were no significant changes to DG granule cell M-current amplitude. Traumatic brain injury induced significantly greater KCNQ2 expression in the hippocampal hemisphere that was ipsilateral to the trauma. In vivo, after a secondary challenge with subconvulsant dose of pentylenetetrazole, control mice were susceptible to tonic-clonic seizures, whereas mice administered the M-channel opener retigabine were protected from such seizures. This study demonstrates that increased excitatory activity promotes KCNQ2 upregulation in the hippocampus in a cell-type specific manner. Such novel ion channel expressional plasticity may serve as a compensatory mechanism after a hyperexcitable event, at least in the short term. The upregulation described could be potentially leveraged in anticonvulsant enhancement of KCNQ2 channels as therapeutic target for preventing onset of epileptogenic seizures.
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Affiliation(s)
- Chase M Carver
- Department of Cellular and Integrative Physiology, University of Texas Health San Antonio, San Antonio, Texas
| | - Shayne D Hastings
- Department of Cellular and Integrative Physiology, University of Texas Health San Antonio, San Antonio, Texas
| | - Mileah E Cook
- Department of Cellular and Integrative Physiology, University of Texas Health San Antonio, San Antonio, Texas
| | - Mark S Shapiro
- Department of Cellular and Integrative Physiology, University of Texas Health San Antonio, San Antonio, Texas
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11
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Wang W, Jia Y, Pham DT, Palmer LC, Jung KM, Cox CD, Rumbaugh G, Piomelli D, Gall CM, Lynch G. Atypical Endocannabinoid Signaling Initiates a New Form of Memory-Related Plasticity at a Cortical Input to Hippocampus. Cereb Cortex 2019; 28:2253-2266. [PMID: 28520937 DOI: 10.1093/cercor/bhx126] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 05/02/2017] [Indexed: 01/16/2023] Open
Abstract
Endocannabinoids (ECBs) depress transmitter release at sites throughout the brain. Here, we describe another form of ECB signaling that triggers a novel form of long-term potentiation (LTP) localized to the lateral perforant path (LPP) which conveys semantic information from cortex to hippocampus. Two cannabinoid CB1 receptor (CB1R) signaling cascades were identified in hippocampus. The first is pregnenolone sensitive, targets vesicular protein Munc18-1 and depresses transmitter release; this cascade is engaged by CB1Rs in Schaffer-Commissural afferents to CA1 but not in the LPP, and it does not contribute to LTP. The second cascade is pregnenolone insensitive and LPP specific; it entails co-operative CB1R/β1-integrin signaling to effect synaptic potentiation via stable enhancement of transmitter release. The latter cascade is engaged during LPP-dependent learning. These results link atypical ECB signaling to the encoding of a fundamental component of episodic memory and suggest a novel route whereby endogenous and exogenous cannabinoids affect cognition.
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Affiliation(s)
- Weisheng Wang
- Department of Anatomy and Neurobiology, University of California, Irvine, CA, USA
| | - Yousheng Jia
- Department of Anatomy and Neurobiology, University of California, Irvine, CA, USA
| | - Danielle T Pham
- Department of Anatomy and Neurobiology, University of California, Irvine, CA, USA
| | - Linda C Palmer
- Department of Anatomy and Neurobiology, University of California, Irvine, CA, USA
| | - Kwang-Mook Jung
- Department of Anatomy and Neurobiology, University of California, Irvine, CA, USA
| | - Conor D Cox
- Department of Anatomy and Neurobiology, University of California, Irvine, CA, USA
| | - Gavin Rumbaugh
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL, USA
| | - Daniele Piomelli
- Department of Anatomy and Neurobiology, University of California, Irvine, CA, USA.,Department of Pharmacology, University of California, Irvine, CA, USA.,Department of Biological Chemistry, University of California, Irvine, CA, USA.,Drug Discovery and Development, Instituto Italiano di Tecnologia, Genoa, Italy
| | - Christine M Gall
- Department of Anatomy and Neurobiology, University of California, Irvine, CA, USA.,Department of Neurobiology and Behavior, University of California, Irvine, CA, USA
| | - Gary Lynch
- Department of Anatomy and Neurobiology, University of California, Irvine, CA, USA.,Department of Psychiatry and Human Behavior, University of California, Irvine, CA, USA
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12
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Cox BM, Cox CD, Gunn BG, Le AA, Inshishian VC, Gall CM, Lynch G. Acquisition of temporal order requires an intact CA3 commissural/associational (C/A) feedback system in mice. Commun Biol 2019; 2:251. [PMID: 31286068 PMCID: PMC6610080 DOI: 10.1038/s42003-019-0494-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 05/30/2019] [Indexed: 12/31/2022] Open
Abstract
Episodic memory, an essential element of orderly thinking, requires the organization of serial events into narratives about the identity of cues along with their locations and temporal order (what, where, and when). The hippocampus plays a central role in the acquisition and retrieval of episodes with two of its subsystems being separately linked to what and where information. The substrates for the third element are poorly understood. Here we report that in hippocampal slices field CA3 maintains self-sustained activity for remarkable periods following a brief input and that this effect is extremely sensitive to minor network perturbations. Using behavioral tests, that do not involve training or explicit rewards, we show that partial silencing of the CA3 commissural/associational network in mice blocks acquisition of temporal order, but not the identity or location, of odors. These results suggest a solution to the question of how hippocampus adds time to episodic memories.
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Affiliation(s)
- Brittney M. Cox
- Department of Anatomy and Neurobiology, University of California, Irvine, CA 92697 USA
| | - Conor D. Cox
- Department of Anatomy and Neurobiology, University of California, Irvine, CA 92697 USA
| | - Benjamin G. Gunn
- Department of Anatomy and Neurobiology, University of California, Irvine, CA 92697 USA
| | - Aliza A. Le
- Department of Anatomy and Neurobiology, University of California, Irvine, CA 92697 USA
| | | | - Christine M. Gall
- Department of Anatomy and Neurobiology, University of California, Irvine, CA 92697 USA
- Department of Neurobiology and Behavior, University of California, Irvine, CA 92697 USA
| | - Gary Lynch
- Department of Anatomy and Neurobiology, University of California, Irvine, CA 92697 USA
- Department of Psychiatry and Human Behavior, University of California, Irvine, CA 92697 USA
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13
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Rotermund N, Schulz K, Hirnet D, Lohr C. Purinergic Signaling in the Vertebrate Olfactory System. Front Cell Neurosci 2019; 13:112. [PMID: 31057369 PMCID: PMC6477478 DOI: 10.3389/fncel.2019.00112] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 03/07/2019] [Indexed: 12/15/2022] Open
Abstract
Adenosine 5'-triphosphate (ATP) is an ubiquitous co-transmitter in the vertebrate brain. ATP itself, as well as its breakdown products ADP and adenosine are involved in synaptic transmission and plasticity, neuron-glia communication and neural development. Although purinoceptors have been demonstrated in the vertebrate olfactory system by means of histological techniques for many years, detailed insights into physiological properties and functional significance of purinergic signaling in olfaction have been published only recently. We review the current literature on purinergic neuromodulation, neuron-glia interactions and neurogenesis in the vertebrate olfactory system.
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Affiliation(s)
- Natalie Rotermund
- Division of Neurophysiology, University of Hamburg, Hamburg, Germany
| | - Kristina Schulz
- Division of Neurophysiology, University of Hamburg, Hamburg, Germany
| | - Daniela Hirnet
- Division of Neurophysiology, University of Hamburg, Hamburg, Germany
| | - Christian Lohr
- Division of Neurophysiology, University of Hamburg, Hamburg, Germany
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14
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Cellular and Molecular Differences Between Area CA1 and the Dentate Gyrus of the Hippocampus. Mol Neurobiol 2019; 56:6566-6580. [PMID: 30874972 DOI: 10.1007/s12035-019-1541-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 02/27/2019] [Indexed: 12/16/2022]
Abstract
A distinct feature of the hippocampus of the brain is its unidirectional tri-synaptic pathway originating from the entorhinal cortex and projecting to the dentate gyrus (DG) then to area CA3 and subsequently, area CA1 of the Ammon's horn. Each of these areas of the hippocampus has its own cellular structure and distinctive function. The principal neurons in these areas are granule cells in the DG and pyramidal cells in the Ammon's horn's CA1 and CA3 areas with a vast network of interneurons. This review discusses the fundamental differences between the CA1 and DG areas regarding cell morphology, synaptic plasticity, signaling molecules, ability for neurogenesis, vulnerability to various insults and pathologies, and response to pharmacological agents.
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15
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Memory-Related Synaptic Plasticity Is Sexually Dimorphic in Rodent Hippocampus. J Neurosci 2018; 38:7935-7951. [PMID: 30209204 DOI: 10.1523/jneurosci.0801-18.2018] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 06/22/2018] [Accepted: 07/15/2018] [Indexed: 12/22/2022] Open
Abstract
Men are generally superior to women in remembering spatial relationships, whereas the reverse holds for semantic information, but the neurobiological bases for these differences are not understood. Here we describe striking sexual dimorphism in synaptic mechanisms of memory encoding in hippocampal field CA1, a region critical for spatial learning. Studies of acute hippocampal slices from adult rats and mice show that for excitatory Schaffer-commissural projections, the memory-related long-term potentiation (LTP) effect depends upon endogenous estrogen and membrane estrogen receptor α (ERα) in females but not in males; there was no evident involvement of nuclear ERα in females, or of ERβ or GPER1 (G-protein-coupled estrogen receptor 1) in either sex. Quantitative immunofluorescence showed that stimulation-induced activation of two LTP-related kinases (Src, ERK1/2), and of postsynaptic TrkB, required ERα in females only, and that postsynaptic ERα levels are higher in females than in males. Several downstream signaling events involved in LTP were comparable between the sexes. In contrast to endogenous estrogen effects, infused estradiol facilitated LTP and synaptic signaling in females via both ERα and ERβ. The estrogen dependence of LTP in females was associated with a higher threshold for both inducing potentiation and acquiring spatial information. These results indicate that the observed sexual dimorphism in hippocampal LTP reflects differences in synaptic kinase activation, including both a weaker association with NMDA receptors and a greater ERα-mediated kinase activation in response to locally produced estrogen in females. We propose that male/female differences in mechanisms and threshold for field CA1 LTP contribute to differences in encoding specific types of memories.SIGNIFICANCE STATEMENT There is good evidence for male/female differences in memory-related cognitive function, but the neurobiological basis for this sexual dimorphism is not understood. Here we describe sex differences in synaptic function in a brain area that is critical for learning spatial cues. Our results show that female rodents have higher synaptic levels of estrogen receptor α (ERα) and, in contrast to males, require membrane ERα for the activation of signaling kinases that support long-term potentiation (LTP), a form of synaptic plasticity thought to underlie learning. The additional requirement of estrogen signaling in females resulted in a higher threshold for both LTP and hippocampal field CA1-dependent spatial learning. These results describe a synaptic basis for sexual dimorphism in encoding spatial information.
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16
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Treating a novel plasticity defect rescues episodic memory in Fragile X model mice. Mol Psychiatry 2018; 23:1798-1806. [PMID: 29133950 PMCID: PMC5951717 DOI: 10.1038/mp.2017.221] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Revised: 07/02/2017] [Accepted: 07/28/2017] [Indexed: 11/18/2022]
Abstract
Episodic memory, a fundamental component of human cognition, is significantly impaired in autism. We believe we report the first evidence for this problem in the Fmr1-knockout (KO) mouse model of Fragile X syndrome and describe potentially treatable underlying causes. The hippocampus is critical for the formation and use of episodes, with semantic (cue identity) information relayed to the structure via the lateral perforant path (LPP). The unusual form of synaptic plasticity expressed by the LPP (lppLTP) was profoundly impaired in Fmr1-KOs relative to wild-type mice. Two factors contributed to this defect: (i) reduced GluN1 subunit levels in synaptic NMDA receptors and related currents, and (ii) impaired retrograde synaptic signaling by the endocannabinoid 2-arachidonoylglycerol (2-AG). Studies using a novel serial cue paradigm showed that episodic encoding is dependent on both the LPP and the endocannabinoid receptor CB1, and is strikingly impaired in Fmr1-KOs. Enhancing 2-AG signaling rescued both lppLTP and learning in the mutants. Thus, two consequences of the Fragile-X mutation converge on plasticity at one site in hippocampus to prevent encoding of a basic element of cognitive memory. Collectively, the results suggest a clinically plausible approach to treatment.
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17
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Converging, Synergistic Actions of Multiple Stress Hormones Mediate Enduring Memory Impairments after Acute Simultaneous Stresses. J Neurosci 2017; 36:11295-11307. [PMID: 27807170 DOI: 10.1523/jneurosci.2542-16.2016] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 09/16/2016] [Indexed: 11/21/2022] Open
Abstract
Stress influences memory, an adaptive process crucial for survival. During stress, hippocampal synapses are bathed in a mixture of stress-released molecules, yet it is unknown whether or how these interact to mediate the effects of stress on memory. Here, we demonstrate novel synergistic actions of corticosterone and corticotropin-releasing hormone (CRH) on synaptic physiology and dendritic spine structure that mediate the profound effects of acute concurrent stresses on memory. Spatial memory in mice was impaired enduringly after acute concurrent stresses resulting from loss of synaptic potentiation associated with disrupted structure of synapse-bearing dendritic spines. Combined application of the stress hormones corticosterone and CRH recapitulated the physiological and structural defects provoked by acute stresses. Mechanistically, corticosterone and CRH, via their cognate receptors, acted synergistically on the spine-actin regulator RhoA, promoting its deactivation and degradation, respectively, and destabilizing spines. Accordingly, blocking the receptors of both hormones, but not each alone, rescued memory. Therefore, the synergistic actions of corticosterone and CRH at hippocampal synapses underlie memory impairments after concurrent and perhaps also single, severe acute stresses, with potential implications to spatial memory dysfunction in, for example, posttraumatic stress disorder. SIGNIFICANCE STATEMENT Stress influences memory, an adaptive process crucial for survival. During stress, adrenal corticosterone and hippocampal corticotropin-releasing hormone (CRH) permeate memory-forming hippocampal synapses, yet it is unknown whether (and how) these hormones interact to mediate effects of stress. Here, we demonstrate novel synergistic actions of corticosterone and CRH on hippocampal synaptic plasticity and spine structure that mediate the memory-disrupting effects of stress. Combined application of both hormones provoked synaptic function collapse and spine disruption. Mechanistically, corticosterone and CRH synergized at the spine-actin regulator RhoA, promoting its deactivation and degradation, respectively, and destabilizing spines. Notably, blocking both hormones, but not each alone, prevented the enduring memory problems after acute concurrent stresses. Therefore, synergistic actions of corticosterone and CRH underlie enduring memory impairments after concurrent acute stresses, which might be relevant to spatial memory deficits described in posttraumatic stress disorder.
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18
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Merrill CB, Basit A, Armirotti A, Jia Y, Gall CM, Lynch G, Piomelli D. Patch clamp-assisted single neuron lipidomics. Sci Rep 2017; 7:5318. [PMID: 28706218 PMCID: PMC5509708 DOI: 10.1038/s41598-017-05607-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 05/31/2017] [Indexed: 11/09/2022] Open
Abstract
Our understanding of the physiological and pathological functions of brain lipids is limited by the inability to analyze these molecules at cellular resolution. Here, we present a method that enables the detection of lipids in identified single neurons from live mammalian brains. Neuronal cell bodies are captured from perfused mouse brain slices by patch clamping, and lipids are analyzed using an optimized nanoflow liquid chromatography/mass spectrometry protocol. In a first application of the method, we identified more than 40 lipid species from dentate gyrus granule cells and CA1 pyramidal neurons of the hippocampus. This survey revealed substantial lipid profile differences between neurons and whole brain tissue, as well as between resting and physiologically stimulated neurons. The results suggest that patch clamp-assisted single neuron lipidomics could be broadly applied to investigate neuronal lipid homeostasis in healthy and diseased brains.
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Affiliation(s)
- Collin B Merrill
- Department of Anatomy and Neurobiology, University of California, Irvine, Irvine, CA, 92697, USA
| | - Abdul Basit
- Department of Drug Discovery and Development, Istituto Italiano di Tecnologia, Genoa, 16163, Italy
| | - Andrea Armirotti
- Department of Drug Discovery and Development, Istituto Italiano di Tecnologia, Genoa, 16163, Italy
| | - Yousheng Jia
- Department of Anatomy and Neurobiology, University of California, Irvine, Irvine, CA, 92697, USA
| | - Christine M Gall
- Department of Anatomy and Neurobiology, University of California, Irvine, Irvine, CA, 92697, USA.,Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA, 92697, USA
| | - Gary Lynch
- Department of Anatomy and Neurobiology, University of California, Irvine, Irvine, CA, 92697, USA.,Department of Psychiatry and Human Behavior, University of California, Irvine, Irvine, CA, 92697, USA
| | - Daniele Piomelli
- Department of Anatomy and Neurobiology, University of California, Irvine, Irvine, CA, 92697, USA. .,Department of Pharmacology, University of California, Irvine, Irvine, CA, 92697, USA. .,Department of Biological Chemistry, University of California, Irvine, Irvine, CA, 92697, USA.
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19
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Mutation of neuron-specific chromatin remodeling subunit BAF53b: rescue of plasticity and memory by manipulating actin remodeling. ACTA ACUST UNITED AC 2017; 24:199-209. [PMID: 28416631 PMCID: PMC5397687 DOI: 10.1101/lm.044602.116] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 02/28/2017] [Indexed: 12/21/2022]
Abstract
Recent human exome-sequencing studies have implicated polymorphic Brg1-associated factor (BAF) complexes (mammalian SWI/SNF chromatin remodeling complexes) in several intellectual disabilities and cognitive disorders, including autism. However, it remains unclear how mutations in BAF complexes result in impaired cognitive function. Post-mitotic neurons express a neuron-specific assembly, nBAF, characterized by the neuron-specific subunit BAF53b. Subdomain 2 of BAF53b is essential for the differentiation of neuronal precursor cells into neurons. We generated transgenic mice lacking subdomain 2 of Baf53b (BAF53bΔSB2). Long-term synaptic potentiation (LTP) and long-term memory, both of which are associated with phosphorylation of the actin severing protein cofilin, were assessed in these animals. A phosphorylation mimic of cofilin was stereotaxically delivered into the hippocampus of BAF53bΔSB2 mice in an effort to rescue LTP and memory. BAF53bΔSB2 mutant mice show impairments in phosphorylation of synaptic cofilin, LTP, and memory. Both the synaptic plasticity and memory deficits are rescued by overexpression of a phosphorylation mimetic of cofilin. Baseline physiology and behavior were not affected by the mutation or the experimental treatment. This study suggests a potential link between nBAF function, actin cytoskeletal remodeling at the dendritic spine, and memory formation. This work shows that a targeted manipulation of synaptic function can rescue adult plasticity and memory deficits caused by manipulations of nBAF, and thereby provides potential novel avenues for therapeutic development for multiple intellectual disability disorders.
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20
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Lauterborn JC, Kramár EA, Rice JD, Babayan AH, Cox CD, Karsten CA, Gall CM, Lynch G. Cofilin Activation Is Temporally Associated with the Cessation of Growth in the Developing Hippocampus. Cereb Cortex 2017; 27:2640-2651. [PMID: 27073215 PMCID: PMC5964364 DOI: 10.1093/cercor/bhw088] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Dendritic extension and synaptogenesis proceed at high rates in rat hippocampus during early postnatal life but markedly slow during the third week of development. The reasons for the latter, fundamental event are poorly understood. Here, we report that levels of phosphorylated (inactive) cofilin, an actin depolymerizing factor, decrease by 90% from postnatal days (pnds) 10 to 21. During the same period, levels of total and phosphorylated Arp2, which nucleates actin branches, increase. A search for elements that could explain the switch from inactive to active cofilin identified reductions in β1 integrin, TrkB, and LIM domain kinase 2b, upstream proteins that promote cofilin phosphorylation. Moreover, levels of slingshot 3, which dephosphorylates cofilin, increase during the period in which growth slows. Consistent with the cofilin results, in situ phalloidin labeling of F-actin demonstrated that spines and dendrites contained high levels of dynamic actin filaments during Week 2, but these fell dramatically by pnd 21. The results suggest that the change from inactive to constitutively active cofilin leads to a loss of dynamic actin filaments needed for process extension and thus the termination of spine formation and synaptogenesis. The relevance of these events to the emergence of memory-related synaptic plasticity is described.
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Affiliation(s)
| | | | | | | | | | | | - Christine M. Gall
- Department of Anatomy and Neurobiology
- Department of Neurobiology and Behavior
| | - Gary Lynch
- Department of Anatomy and Neurobiology
- Department of Psychiatry and Human Behavior, University of California at Irvine, Irvine, CA 92697, USA
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21
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Wang W, Kantorovich S, Babayan AH, Hou B, Gall CM, Lynch G. Estrogen's Effects on Excitatory Synaptic Transmission Entail Integrin and TrkB Transactivation and Depend Upon β1-integrin function. Neuropsychopharmacology 2016; 41:2723-32. [PMID: 27272766 PMCID: PMC5026741 DOI: 10.1038/npp.2016.83] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Revised: 05/17/2016] [Accepted: 05/20/2016] [Indexed: 01/19/2023]
Abstract
Estradiol (E2) perfusion rapidly increases the strength of fast excitatory transmission and facilitates long-term potentiation in the hippocampus, two effects likely related to its memory-enhancing properties. Past studies showed that E2's facilitation of transmission involves activation of RhoA signaling leading to actin polymerization in dendritic spines. Here we report that brief exposure of adult male hippocampal slices to 1 nM E2 increases the percentage of postsynaptic densities associated with high levels of immunoreactivity for activated forms of the BDNF receptor TrkB and β1-integrins, two synaptic receptors that engage actin regulatory RhoA signaling. The effects of E2 on baseline synaptic responses were unaffected by pretreatment with the TrkB-Fc scavenger for extracellular BDNF or TrkB antagonism, but were eliminated by neutralizing antisera for β1-integrins. E2 effects on synaptic responses were also absent in conditional β1-integrin knockouts, and with inhibition of matrix metalloproteinases, extracellular enzymes that generate integrin ligands. We propose that E2, acting through estrogen receptor-β, transactivates synaptic TrkB and β1-integrin, and via mechanisms dependent on integrin activation and signaling, reversibly reorganizes the spine cytoskeleton and thereby enhances synaptic responses in adult hippocampus.
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Affiliation(s)
- Weisheng Wang
- Department of Anatomy and Neurobiology, University of California, Irvine, CA, USA
| | - Svetlana Kantorovich
- Department of Anatomy and Neurobiology, University of California, Irvine, CA, USA
| | - Alex H Babayan
- Department of Anatomy and Neurobiology, University of California, Irvine, CA, USA
| | - Bowen Hou
- Department of Anatomy and Neurobiology, University of California, Irvine, CA, USA
| | - Christine M Gall
- Department of Anatomy and Neurobiology, University of California, Irvine, CA, USA,Department of Neurobiology and Behavior, University of California, Irvine, CA, USA,Department of Anatomy and Neurobiology, Gillespie Neuroscience Research Facility, University of California at Irvine, 837 Health Science Road, Irvine, CA 92697, USA, Tel: +1 949 824 8652, Fax: +1 949 824 0276, E-mail: or
| | - Gary Lynch
- Department of Anatomy and Neurobiology, University of California, Irvine, CA, USA,Department of Psychiatry and Human Behavior, University of California, Irvine, CA, USA,Department of Anatomy and Neurobiology, Gillespie Neuroscience Research Facility, University of California at Irvine, 837 Health Science Road, Irvine, CA 92697, USA, Tel: +1 949 824 8652, Fax: +1 949 824 0276, E-mail: or
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22
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A Primary Cortical Input to Hippocampus Expresses a Pathway-Specific and Endocannabinoid-Dependent Form of Long-Term Potentiation. eNeuro 2016; 3:eN-NWR-0160-16. [PMID: 27517090 PMCID: PMC4976302 DOI: 10.1523/eneuro.0160-16.2016] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 07/14/2016] [Accepted: 07/15/2016] [Indexed: 02/03/2023] Open
Abstract
The endocannabinoid 2-arachidonoyl-sn-glycerol (2-AG), a key modulator of synaptic transmission in mammalian brain, is produced in dendritic spines and then crosses the synaptic junction to depress neurotransmitter release. Here we report that 2-AG-dependent retrograde signaling also mediates an enduring enhancement of glutamate release, as assessed with independent tests, in the lateral perforant path (LPP), one of two cortical inputs to the granule cells of the dentate gyrus. Induction of this form of long-term potentiation (LTP) involved two types of glutamate receptors, changes in postsynaptic calcium, and the postsynaptic enzyme that synthesizes 2-AG. Stochastic optical reconstruction microscopy confirmed that CB1 cannabinoid receptors are localized presynaptically to LPP terminals, while the inhibition or knockout of the receptors eliminated LPP-LTP. Suppressing the enzyme that degrades 2-AG dramatically enhanced LPP potentiation, while overexpressing it produced the opposite effect. Priming with a CB1 agonist markedly reduced the threshold for LTP. Latrunculin A, which prevents actin polymerization, blocked LPP-LTP when applied extracellularly but had no effect when infused postsynaptically into granule cells, indicating that critical actin remodeling resides in the presynaptic compartment. Importantly, there was no evidence for the LPP form of potentiation in the Schaffer-commissural innervation of field CA1 or in the medial perforant path. Peripheral injections of compounds that block or enhance LPP-LTP had corresponding effects on the formation of long-term memory for cues conveyed to the dentate gyrus by the LPP. Together, these results indicate that the encoding of information carried by a principal hippocampal afferent involves an unusual, regionally differentiated form of plasticity.
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23
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Chronic Ampakine Treatments Stimulate Dendritic Growth and Promote Learning in Middle-Aged Rats. J Neurosci 2016; 36:1636-46. [PMID: 26843645 DOI: 10.1523/jneurosci.3157-15.2016] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
UNLABELLED Positive allosteric modulators of AMPA-type glutamate receptors (ampakines) have been shown to rescue synaptic plasticity and reduce neuropathology in rodent models of cognitive disorders. Here we tested whether chronic ampakine treatment offsets age-related dendritic retraction in middle-aged (MA) rats. Starting at 10 months of age, rats were housed in an enriched environment and given daily treatment with a short half-life ampakine or vehicle for 3 months. Dendritic branching and spine measures were collected from 3D reconstructions of Lucifer yellow-filled CA1 pyramidal cells. There was a substantial loss of secondary branches, relative to enriched 2.5-month-old rats, in apical and basal dendritic fields of vehicle-treated, but not ampakine-treated, 13-month-old rats. Baseline synaptic responses in CA1 were only subtly different between the two MA groups, but long-term potentiation was greater in ampakine-treated rats. Unsupervised learning of a complex environment was used to assess treatment effects on behavior. Vehicle- and drug-treated rats behaved similarly during a first 30 min session in the novel environment but differed markedly on subsequent measures of long-term memory. Markov sequence analysis uncovered a clear increase in the predictability of serial movements between behavioral sessions 2 and 3 in the ampakine, but not vehicle, group. These results show that a surprising degree of dendritic retraction occurs by middle age and that this can be mostly offset by pharmacological treatments without evidence for unwanted side effects. The functional consequences of rescue were prominent with regard to memory but also extended to self-organization of behavior. SIGNIFICANCE STATEMENT Brain aging is characterized by a progressive loss of dendritic arbors and the emergence of impairments to learning-related synaptic plasticity. The present studies show that dendritic losses are evident by middle age despite housing in an enriched environment and can be mostly reversed by long-term, oral administration of a positive allosteric modulator of AMPA-type glutamate receptors. Dendritic recovery was accompanied by improvements to both synaptic plasticity and the encoding of long-term memory of a novel, complex environment. Because the short half-life compound had no evident negative effects, the results suggest a plausible strategy for treating age-related neuronal deterioration.
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