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Hernández-Frausto M, Vivar C. Entorhinal cortex-hippocampal circuit connectivity in health and disease. Front Hum Neurosci 2024; 18:1448791. [PMID: 39372192 PMCID: PMC11449717 DOI: 10.3389/fnhum.2024.1448791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2024] [Accepted: 09/03/2024] [Indexed: 10/08/2024] Open
Abstract
The entorhinal cortex (EC) and hippocampal (HC) connectivity is the main source of episodic memory formation and consolidation. The entorhinal-hippocampal (EC-HC) connection is classified as canonically glutamatergic and, more recently, has been characterized as a non-canonical GABAergic connection. Recent evidence shows that both EC and HC receive inputs from dopaminergic, cholinergic, and noradrenergic projections that modulate the mnemonic processes linked to the encoding and consolidation of memories. In the present review, we address the latest findings on the EC-HC connectivity and the role of neuromodulations during the mnemonic mechanisms of encoding and consolidation of memories and highlight the value of the cross-species approach to unravel the underlying cellular mechanisms known. Furthermore, we discuss how EC-HC connectivity early neurodegeneration may contribute to the dysfunction of episodic memories observed in aging and Alzheimer's disease (AD). Finally, we described how exercise may be a fundamental tool to prevent or decrease neurodegeneration.
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Affiliation(s)
- Melissa Hernández-Frausto
- NYU Neuroscience Institute, Department of Neuroscience and Physiology, NYU Grossman School of Medicine, New York University Langone Medical Center, New York, NY, United States
| | - Carmen Vivar
- Laboratory of Neurogenesis and Neuroplasticity, Department of Physiology, Biophysics and Neuroscience, Centro de Investigacion y de Estudios Avanzados del Instituto Politécnico Nacional, Mexico City, Mexico
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2
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Santoro B, Srinivas KV, Reyes I, Tian C, Masurkar AV. Cell type-specific impact of aging and Alzheimer disease on hippocampal CA1 perforant path input. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.08.27.609952. [PMID: 39253428 PMCID: PMC11383042 DOI: 10.1101/2024.08.27.609952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/11/2024]
Abstract
The perforant path (PP) carries direct inputs from entorhinal cortex to CA1 pyramidal neurons (PNs), with an impact dependent on PN position across transverse (CA1a-CA1c) and radial (superficial/deep) axes. It remains unclear how aging and Alzheimer disease (AD) affect PP input, despite its critical role in memory and early AD. Applying ex vivo recordings and two-photon microscopy in slices from mice up to 30 months old, we interrogated PP responses across PN subpopulations and compared them to Schaffer collateral and intrinsic excitability changes. We found that aging uniquely impacts PP excitatory responses, abolishing transverse and radial differences via a mechanism independent of presynaptic and membrane excitability change. This is amplified in aged 3xTg-AD mice, with further weakening of PP inputs to CA1a superficial PNs associated with distal dendritic spine loss. This demonstrates a unique feature of aging-related circuit dysfunction, with mechanistic implications related to memory impairment and synaptic vulnerability.
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Klinger K, del Ángel M, Çalışkan G, Stork O. Increasing NPYergic transmission in the hippocampus rescues aging-related deficits of long-term potentiation in the mouse dentate gyrus. Front Aging Neurosci 2023; 15:1283581. [PMID: 38020778 PMCID: PMC10673643 DOI: 10.3389/fnagi.2023.1283581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2023] [Accepted: 10/26/2023] [Indexed: 12/01/2023] Open
Abstract
Loss of neuropeptide Y (NPY)-expressing interneurons in the hippocampus and decaying cholinergic neuromodulation are thought to contribute to impaired cognitive function during aging. However, the interaction of these two neuromodulatory systems in maintaining hippocampal synaptic plasticity during healthy aging has not been explored so far. Here we report profound sex differences in the Neuropeptide-Y (NPY) levels in the dorsal dentate gyrus (DG) with higher NPY concentrations in the male mice compared to their female counterparts and a reduction of NPY levels during aging specifically in males. This change in aged males is accompanied by a deficit in theta burst-induced long-term potentiation (LTP) in the medial perforant path-to-dorsal DG (MPP-DG) synapse, which can be rescued by enhancing cholinergic activation with the acetylcholine esterase blocker, physostigmine. Importantly, NPYergic transmission is required for this rescue of LTP. Moreover, exogenous NPY application alone is sufficient to recover LTP induction in aged male mice, even in the absence of the cholinergic stimulator. Together, our results suggest that in male mice NPYergic neurotransmission is a critical factor for maintaining dorsal DG LTP during aging.
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Affiliation(s)
- Katharina Klinger
- Department of Genetics and Molecular Neurobiology, Institute of Biology, Otto-von-Guericke University, Magdeburg, Germany
- Research Group “Synapto-Oscillopathies”, Institute of Biology, Otto-von-Guericke-University, Magdeburg, Germany
| | - Miguel del Ángel
- Department of Genetics and Molecular Neurobiology, Institute of Biology, Otto-von-Guericke University, Magdeburg, Germany
| | - Gürsel Çalışkan
- Department of Genetics and Molecular Neurobiology, Institute of Biology, Otto-von-Guericke University, Magdeburg, Germany
- Research Group “Synapto-Oscillopathies”, Institute of Biology, Otto-von-Guericke-University, Magdeburg, Germany
- Center for Behavioral Brain Sciences, Magdeburg, Germany
| | - Oliver Stork
- Department of Genetics and Molecular Neurobiology, Institute of Biology, Otto-von-Guericke University, Magdeburg, Germany
- Center for Behavioral Brain Sciences, Magdeburg, Germany
- Center for Intervention and Research on Adaptive and Maladaptive Brain Circuits Underlying Mental Health (C-I-R-C), Magdeburg, Germany
- German Center for Mental Health (DZPG), Magdeburg, Germany
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4
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McDermott KD, Frechou MA, Jordan JT, Martin SS, Gonçalves JT. Delayed formation of neural representations of space in aged mice. Aging Cell 2023; 22:e13924. [PMID: 37491802 PMCID: PMC10497831 DOI: 10.1111/acel.13924] [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: 03/29/2023] [Revised: 05/31/2023] [Accepted: 06/20/2023] [Indexed: 07/27/2023] Open
Abstract
Aging is associated with cognitive deficits, with spatial memory being very susceptible to decline. The hippocampal dentate gyrus (DG) is important for processing spatial information in the brain and is particularly vulnerable to aging, yet its sparse activity has led to difficulties in assessing changes in this area. Using in vivo two-photon calcium imaging, we compared DG neuronal activity and representations of space in young and aged mice walking on an unfamiliar treadmill. We found that calcium activity was significantly higher and less tuned to location in aged mice, resulting in decreased spatial information encoded in the DG. However, with repeated exposure to the same treadmill, both spatial tuning and information levels in aged mice became similar to young mice, while activity remained elevated. Our results show that spatial representations of novel environments are impaired in the aged hippocampus and gradually improve with increased familiarity. Moreover, while the aged DG is hyperexcitable, this does not disrupt neural representations of familiar environments.
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Affiliation(s)
- Kelsey D. McDermott
- Dominick P. Purpura Department of Neuroscience and Gottesmann Institute for Stem Cell Biology and Regenerative MedicineAlbert Einstein College of MedicineBronxNew YorkUSA
| | - M. Agustina Frechou
- Dominick P. Purpura Department of Neuroscience and Gottesmann Institute for Stem Cell Biology and Regenerative MedicineAlbert Einstein College of MedicineBronxNew YorkUSA
| | - Jake T. Jordan
- Dominick P. Purpura Department of Neuroscience and Gottesmann Institute for Stem Cell Biology and Regenerative MedicineAlbert Einstein College of MedicineBronxNew YorkUSA
| | - Sunaina S. Martin
- Dominick P. Purpura Department of Neuroscience and Gottesmann Institute for Stem Cell Biology and Regenerative MedicineAlbert Einstein College of MedicineBronxNew YorkUSA
| | - J. Tiago Gonçalves
- Dominick P. Purpura Department of Neuroscience and Gottesmann Institute for Stem Cell Biology and Regenerative MedicineAlbert Einstein College of MedicineBronxNew YorkUSA
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5
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McDermott KD, Frechou MA, Jordan JT, Martin SS, Gonçalves JT. Delayed formation of neural representations of space in aged mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.03.531021. [PMID: 37034736 PMCID: PMC10081265 DOI: 10.1101/2023.03.03.531021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Aging is associated with cognitive deficits, with spatial memory being very susceptible to decline. The hippocampal dentate gyrus (DG) is important for processing spatial information in the brain and is particularly vulnerable to aging, yet its sparse activity has led to difficulties in assessing changes in this area. Using in vivo two-photon calcium imaging, we compared DG neuronal activity and representations of space in young and aged mice walking on an unfamiliar treadmill. We found that calcium activity was significantly higher and less tuned to location in aged mice, resulting in decreased spatial information encoded in the DG. However, with repeated exposure to the same treadmill, both spatial tuning and information levels in aged mice became similar to young mice, while activity remained elevated. Our results show that spatial representations of novel environments are impaired in the aged hippocampus and gradually improve with increased familiarity. Moreover, while the aged DG is hyperexcitable, this does not disrupt neural representations of familiar environments.
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Affiliation(s)
- Kelsey D. McDermott
- Dominick P. Purpura Department of Neuroscience and Gottesmann Institute for Stem Cell Biology and Regenerative Medicine, Albert Einstein College of Medicine, Bronx, NY
| | - M. Agustina Frechou
- Dominick P. Purpura Department of Neuroscience and Gottesmann Institute for Stem Cell Biology and Regenerative Medicine, Albert Einstein College of Medicine, Bronx, NY
| | - Jake T. Jordan
- Dominick P. Purpura Department of Neuroscience and Gottesmann Institute for Stem Cell Biology and Regenerative Medicine, Albert Einstein College of Medicine, Bronx, NY
| | - Sunaina S. Martin
- Dominick P. Purpura Department of Neuroscience and Gottesmann Institute for Stem Cell Biology and Regenerative Medicine, Albert Einstein College of Medicine, Bronx, NY
| | - J. Tiago Gonçalves
- Dominick P. Purpura Department of Neuroscience and Gottesmann Institute for Stem Cell Biology and Regenerative Medicine, Albert Einstein College of Medicine, Bronx, NY
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6
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Lu X, Lambert P, Benz A, Zorumski CF, Mennerick SJ. Allopregnanolone Effects on Inhibition in Hippocampal Parvalbumin Interneurons. eNeuro 2023; 10:ENEURO.0392-22.2023. [PMID: 36725341 PMCID: PMC10012327 DOI: 10.1523/eneuro.0392-22.2023] [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: 09/18/2022] [Revised: 01/12/2023] [Accepted: 01/18/2023] [Indexed: 02/03/2023] Open
Abstract
Allopregnanolone (AlloP) is a neurosteroid that potentiates ionotropic GABAergic (GABAA) inhibition and is approved for treating postpartum depression in women. Although the antidepressant mechanism of AlloP is largely unknown, it could involve selective action at GABAA receptors containing the δ subunit. Despite previous evidence for selective effects of AlloP on α4/δ-containing receptors of hippocampal dentate granule cells (DGCs), other recent results failed to demonstrate selectivity at these receptors (Lu et al., 2020). In contrast to DGCs, hippocampal fast-spiking parvalbumin (PV) interneurons express an unusual variant partnership of δ subunits with α1 subunits. Here, we hypothesized that native α1/δ receptors in hippocampal fast-spiking interneurons may provide a preferred substrate for AlloP. Contrary to the hypothesis, electrophysiology from genetically tagged PV interneurons in hippocampal slices from male mice showed that 100 nm AlloP promoted phasic inhibition by increasing the sIPSC decay, but tonic inhibition was not detectably altered. Co-application of AlloP with 5 μm GABA did augment tonic current, which was not primarily through δ-containing receptors. Furthermore, AlloP decreased the membrane resistance and the number of action potentials of DGCs, but the impact on PV interneurons was weaker than on DGCs. Thus, our results indicate that hippocampal PV interneurons possess low sensitivity to AlloP and suggest they are unlikely contributors to mood-altering effects of neurosteroids through GABA effects.
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Affiliation(s)
- Xinguo Lu
- Department of Psychiatry, Washington University in St. Louis, St. Louis, MO 63110
| | - Peter Lambert
- Department of Psychiatry, Washington University in St. Louis, St. Louis, MO 63110
| | - Ann Benz
- Department of Psychiatry, Washington University in St. Louis, St. Louis, MO 63110
| | - Charles F Zorumski
- Department of Psychiatry, Washington University in St. Louis, St. Louis, MO 63110
- Department of Neuroscience, Washington University in St. Louis, St. Louis, MO 63110
- Taylor Family Institute for Innovative Psychiatric Research, Washington University in St. Louis, St. Louis, MO 63110
| | - Steven J Mennerick
- Department of Psychiatry, Washington University in St. Louis, St. Louis, MO 63110
- Department of Neuroscience, Washington University in St. Louis, St. Louis, MO 63110
- Taylor Family Institute for Innovative Psychiatric Research, Washington University in St. Louis, St. Louis, MO 63110
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7
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Joshi S, Williams CL, Kapur J. Limbic progesterone receptors regulate spatial memory. Sci Rep 2023; 13:2164. [PMID: 36750584 PMCID: PMC9905062 DOI: 10.1038/s41598-023-29100-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 01/30/2023] [Indexed: 02/09/2023] Open
Abstract
Progesterone and its receptors (PRs) participate in mating and reproduction, but their role in spatial declarative memory is not understood. Male mice expressed PRs, predominately in excitatory neurons, in brain regions that support spatial memory, such as the hippocampus and entorhinal cortex (EC). Furthermore, segesterone, a specific PR agonist, activates neurons in both the EC and hippocampus. We assessed the contribution of PRs in promoting spatial and non-spatial cognitive learning in male mice by examining the performance of mice lacking this receptor (PRKO), in novel object recognition, object placement, Y-maze alternation, and Morris-Water Maze (MWM) tasks. In the recognition test, the PRKO mice preferred the familiar object over the novel object. A similar preference for the familiar object was also seen following the EC-specific deletion of PRs. PRKO mice were also unable to recognize the change in object position. We confirmed deficits in spatial memory of PRKO mice by testing them on the Y-maze forced alternation and MWM tasks; PR deletion affected animal's performance in both these tasks. In contrast to spatial tasks, PR removal did not alter the response to fear conditioning. These studies provide novel insights into the role of PRs in facilitating spatial, declarative memory in males, which may help with finding reproductive partners.
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Affiliation(s)
- Suchitra Joshi
- Department of Neurology, University of Virginia, Health Sciences Center, P.O. Box 801330, Charlottesville, VA, 22908, USA.
| | - Cedric L Williams
- Department of Psychology, University of Virginia, Charlottesville, VA, 22908, USA
| | - Jaideep Kapur
- Department of Neurology, University of Virginia, Health Sciences Center, P.O. Box 801330, Charlottesville, VA, 22908, USA.,Department of Neuroscience, University of Virginia, Charlottesville, VA, 22908, USA.,UVA Brain Institute, University of Virginia, Charlottesville, VA, 22908, USA
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8
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Poon CH, Liu Y, Pak S, Zhao RC, Aquili L, Tipoe GL, Leung GKK, Chan YS, Yang S, Fung ML, Wu EX, Lim LW. Prelimbic Cortical Stimulation with L-methionine Enhances Cognition through Hippocampal DNA Methylation and Neuroplasticity Mechanisms. Aging Dis 2023; 14:112-135. [PMID: 36818556 PMCID: PMC9937711 DOI: 10.14336/ad.2022.0706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2022] [Accepted: 07/06/2022] [Indexed: 11/18/2022] Open
Abstract
Declining global DNA methylation and cognitive impairment are reported to occur in the normal aging process. It is not known if DNA methylation plays a role in the efficacy of memory-enhancing therapies. In this study, aged animals were administered prelimbic cortical deep brain stimulation (PrL DBS) and/or L-methionine (MET) treatment. We found that PrL DBS and MET (MET-PrL DBS) co-administration resulted in hippocampal-dependent spatial memory enhancements in aged animals. Molecular data suggested MET-PrL DBS induced DNA methyltransferase DNMT3a-dependent methylation, robust synergistic upregulation of neuroplasticity-related genes, and simultaneous inhibition of the memory-suppressing gene calcineurin in the hippocampus. We further found that MET-PrL DBS also activated the PKA-CaMKIIα-BDNF pathway, increased hippocampal neurogenesis, and enhanced dopaminergic and serotonergic neurotransmission. We next inhibited the activity of DNA methyltransferase (DNMT) by RG108 infusion in the hippocampus of young animals to establish a causal relationship between DNMT activity and the effects of PrL DBS. Hippocampal DNMT inhibition in young animals was sufficient to recapitulate the behavioral deficits observed in aged animals and abolished the memory-enhancing and molecular effects of PrL DBS. Our findings implicate hippocampal DNMT as a therapeutic target for PrL DBS and pave way for the potential use of non-invasive neuromodulation modalities against dementia.
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Affiliation(s)
- Chi Him Poon
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
| | - Yanzhi Liu
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
| | - Sojeong Pak
- Department of Neuroscience, City University of Hong Kong, Kowloon, Hong Kong, China.
| | | | - Luca Aquili
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.,College of Science, Health, Engineering and Education, Discipline of Psychology, Murdoch University, Perth, Australia.
| | - George Lim Tipoe
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
| | - Gilberto Ka-Kit Leung
- Department of Surgery, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
| | - Ying-Shing Chan
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
| | - Sungchil Yang
- Department of Neuroscience, City University of Hong Kong, Kowloon, Hong Kong, China.
| | - Man-Lung Fung
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
| | - Ed Xuekui Wu
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, China.
| | - Lee Wei Lim
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.,Correspondence should be addressed to: Dr. Lee Wei LIM, Neuromodulation Laboratory, School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China. .
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9
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Lee SH, Bolshakov VY, Shen J. Presenilins regulate synaptic plasticity in the perforant pathways of the hippocampus. Mol Brain 2023; 16:17. [PMID: 36710361 PMCID: PMC9885562 DOI: 10.1186/s13041-023-01009-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 01/20/2023] [Indexed: 01/31/2023] Open
Abstract
Mutations in the Presenilin genes (PSEN1 and PSEN2) are the major cause of familial Alzheimer's disease (AD), highlighting the importance of Presenilin (PS) in AD pathogenesis. Previous studies of PS function in the hippocampus demonstrated that loss of PS results in the impairment of short- and long-term synaptic plasticity and neurotransmitter release at hippocampal Schaffer collateral (SC) and mossy fiber (MF) synapses. Cortical input to the hippocampus through the lateral perforant pathway (LPP) and the medial perforant pathway (MPP) is critical for normal cognitive functions and is particularly vulnerable during aging and early stages of AD. Whether PS regulates synaptic function in the perforant pathways, however, remained unknown. In the current study, we investigate PS function in the LPP and MPP by performing whole-cell and field-potential electrophysiological recordings using acute hippocampal slices from postnatal forebrain-restricted excitatory neuron-specific PS conditional double knockout (cDKO) mice. We found that paired-pulse ratio (PPR) is reduced in the LPP and MPP of PS cDKO mice. Moreover, synaptic frequency facilitation or depression in the LPP or MPP, respectively, is impaired in PS cDKO mice. Notably, depletion of intracellular Ca2+ stores by inhibition of sarcoendoplasmic reticulum Ca2+ ATPase (SERCA) minics and occludes the effects of PS inactivation, as evidenced by decreases of the evoked excitatory postsynaptic currents (EPSCs) amplitude in the LPP and MPP of control neurons but no effect on the EPSC amplitude in PS cDKO neurons, suggesting that impaired intracellular calcium homeostasis in the absence of PS may contribute to the observed deficits in synaptic transmission. While spontaneous synaptic events, such as both the frequency and the amplitude of spontaneous or miniature EPSCs, are similar between PS cDKO and control neurons, long-term potentiation (LTP) is impaired in the LPP and MPP of PS cDKO mice, accompanied with reduction of evoked NMDA receptor-mediated responses. These findings show the importance of PS in the regulation of synaptic plasticity and intracellular calcium homeostasis in the hippocampal perforant pathways.
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Affiliation(s)
- Sang Hun Lee
- Department of Neurology, Brigham & Women's Hospital, Harvard Medical School, Boston, MA, 02115, USA.
| | - Vadim Y Bolshakov
- Department of Psychiatry, McLean Hospital, Harvard Medical School, Belmont, MA, 02478, USA
- Program in Neuroscience, Harvard Medical School, Boston, MA, 02115, USA
| | - Jie Shen
- Department of Neurology, Brigham & Women's Hospital, Harvard Medical School, Boston, MA, 02115, USA
- Program in Neuroscience, Harvard Medical School, Boston, MA, 02115, USA
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Di Castro MA, Volterra A. Astrocyte control of the entorhinal cortex-dentate gyrus circuit: Relevance to cognitive processing and impairment in pathology. Glia 2021; 70:1536-1553. [PMID: 34904753 PMCID: PMC9299993 DOI: 10.1002/glia.24128] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 11/28/2021] [Accepted: 11/30/2021] [Indexed: 12/20/2022]
Abstract
The entorhinal cortex-dentate gyrus circuit is centrally involved in memory processing conveying to the hippocampus spatial and nonspatial context information via, respectively, medial and lateral perforant path (MPP and LPP) excitatory projections onto dentate granule cells (GCs). Here, we review work of several years from our group showing that astrocytes sense local synaptic transmission and exert in turn a presynaptic control at PP-GC synapses. Modulation of neurotransmitter release probability by astrocytes sets basal synaptic strength and dynamic range for long-term potentiation of PP-GC synapses. Intriguingly, this astrocyte control is circuit-specific, being present only at MPP-GC (not LPP-GC) synapses, which selectively express atypical presynaptic N-methyl-D-aspartate receptors (NMDAR) suitable to activation by astrocyte-released glutamate. Moreover, the astrocytic control is peculiarly dependent on the cytokine TNFα, which at constitutive levels acts as a gating factor for the astrocyte signaling. During inflammation/infection processes, increased levels of TNFα lead to uncontrolled astrocyte glutamate release, altered PP-GC circuit processing and, ultimately, impaired contextual memory performance. The TNFα-dependent pathological switch of the synaptic control from astrocytes and its deleterious consequences are observed in animal models of HIV brain infection and multiple sclerosis, conditions both known to cause cognitive disturbances in up to 50% of patients. The review also discusses open issues related to the identified astrocytic pathway: its role in contextual memory processing, potential damaging role in Alzheimer's disease, the existence of vesicular glutamate release from DG astrocytes, and the possible synaptic-like connectivity between astrocytic output sites and PP receptive sites.
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Affiliation(s)
- Maria Amalia Di Castro
- Department of Fundamental Neuroscience, University of Lausanne, Lausanne, Switzerland.,Department of Physiology and Pharmacology, Sapienza University of Rome, Rome, Italy
| | - Andrea Volterra
- Department of Fundamental Neuroscience, University of Lausanne, Lausanne, Switzerland
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11
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Vyleta NP, Snyder JS. Prolonged development of long-term potentiation at lateral entorhinal cortex synapses onto adult-born neurons. PLoS One 2021; 16:e0253642. [PMID: 34143843 PMCID: PMC8213073 DOI: 10.1371/journal.pone.0253642] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 06/09/2021] [Indexed: 11/18/2022] Open
Abstract
Critical period plasticity at adult-born neuron synapses is widely believed to contribute to the learning and memory functions of the hippocampus. Experience regulates circuit integration and for a transient interval, until cells are ~6 weeks old, new neurons display enhanced long-term potentiation (LTP) at afferent and efferent synapses. Since neurogenesis declines substantially with age, this raises questions about the extent of lasting plasticity offered by adult-born neurons. Notably, however, the hippocampus receives sensory information from two major cortical pathways. Broadly speaking, the medial entorhinal cortex conveys spatial information to the hippocampus via the medial perforant path (MPP), and the lateral entorhinal cortex, via the lateral perforant path (LPP), codes for the cues and items that make experiences unique. While enhanced critical period plasticity at MPP synapses is relatively well characterized, no studies have examined long-term plasticity at LPP synapses onto adult-born neurons, even though the lateral entorhinal cortex is uniquely vulnerable to aging and Alzheimer's pathology. We therefore investigated LTP at LPP inputs both within (4-6 weeks) and beyond (8+ weeks) the traditional critical period. At immature stages, adult-born neurons did not undergo significant LTP at LPP synapses, and often displayed long-term depression after theta burst stimulation. However, over the course of 3-4 months, adult-born neurons displayed increasingly greater amounts of LTP. Analyses of short-term plasticity point towards a presynaptic mechanism, where transmitter release probability declines as cells mature, providing a greater dynamic range for strengthening synapses. Collectively, our findings identify a novel form of new neuron plasticity that develops over an extended interval, and may therefore be relevant for maintaining cognitive function in aging.
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Affiliation(s)
- Nicholas P. Vyleta
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
| | - Jason S. Snyder
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
- * E-mail:
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12
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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: 17] [Impact Index Per Article: 5.7] [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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13
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The aging mouse brain: cognition, connectivity and calcium. Cell Calcium 2021; 94:102358. [PMID: 33517250 DOI: 10.1016/j.ceca.2021.102358] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 01/16/2021] [Accepted: 01/18/2021] [Indexed: 02/08/2023]
Abstract
Aging is a complex process that differentially impacts multiple cognitive, sensory, neuronal and molecular processes. Technological innovations now allow for parallel investigation of neuronal circuit function, structure and molecular composition in the brain of awake behaving adult mice. Thus, mice have become a critical tool to better understand how aging impacts the brain. However, a more granular systems-based approach, which considers the impact of age on key features relating to neural processing, is required. Here, we review evidence probing the impact of age on the mouse brain. We focus on a range of processes relating to neuronal function, including cognitive abilities, sensory systems, synaptic plasticity and calcium regulation. Across many systems, we find evidence for prominent age-related dysregulation even before 12 months of age, suggesting that emerging age-related alterations can manifest by late adulthood. However, we also find reports suggesting that some processes are remarkably resilient to aging. The evidence suggests that aging does not drive a parallel, linear dysregulation of all systems, but instead impacts some processes earlier, and more severely, than others. We propose that capturing the more fine-scale emerging features of age-related vulnerability and resilience may provide better opportunities for the rejuvenation of the aged brain.
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14
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Blackmore DG, Turpin F, Palliyaguru T, Evans HT, Chicoteau A, Lee W, Pelekanos M, Nguyen N, Song J, Sullivan RKP, Sah P, Bartlett PF, Götz J. Low-intensity ultrasound restores long-term potentiation and memory in senescent mice through pleiotropic mechanisms including NMDAR signaling. Mol Psychiatry 2021; 26:6975-6991. [PMID: 34040151 PMCID: PMC8760044 DOI: 10.1038/s41380-021-01129-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 03/31/2021] [Accepted: 04/14/2021] [Indexed: 12/20/2022]
Abstract
Advanced physiological aging is associated with impaired cognitive performance and the inability to induce long-term potentiation (LTP), an electrophysiological correlate of memory. Here, we demonstrate in the physiologically aged, senescent mouse brain that scanning ultrasound combined with microbubbles (SUS+MB), by transiently opening the blood-brain barrier, fully restores LTP induction in the dentate gyrus of the hippocampus. Intriguingly, SUS treatment without microbubbles (SUSonly), i.e., without the uptake of blood-borne factors, proved even more effective, not only restoring LTP, but also ameliorating the spatial learning deficits of the aged mice. This functional improvement is accompanied by an altered milieu of the aged hippocampus, including a lower density of perineuronal nets, increased neurogenesis, and synaptic signaling, which collectively results in improved spatial learning. We therefore conclude that therapeutic ultrasound is a non-invasive, pleiotropic modality that may enhance cognition in elderly humans.
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Affiliation(s)
- Daniel G. Blackmore
- grid.1003.20000 0000 9320 7537Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD Australia
| | - Fabrice Turpin
- grid.1003.20000 0000 9320 7537Queensland Brain Institute, The University of Queensland, Brisbane, QLD Australia
| | - Tishila Palliyaguru
- grid.1003.20000 0000 9320 7537Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD Australia
| | - Harrison T. Evans
- grid.1003.20000 0000 9320 7537Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD Australia
| | - Antony Chicoteau
- grid.1003.20000 0000 9320 7537Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD Australia
| | - Wendy Lee
- grid.1003.20000 0000 9320 7537Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD Australia
| | - Matthew Pelekanos
- grid.1003.20000 0000 9320 7537Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD Australia
| | - Nghia Nguyen
- grid.1003.20000 0000 9320 7537Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD Australia
| | - Jae Song
- grid.1003.20000 0000 9320 7537Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD Australia
| | - Robert K. P. Sullivan
- grid.1003.20000 0000 9320 7537Queensland Brain Institute, The University of Queensland, Brisbane, QLD Australia
| | - Pankaj Sah
- grid.1003.20000 0000 9320 7537Queensland Brain Institute, The University of Queensland, Brisbane, QLD Australia ,grid.263817.90000 0004 1773 1790Joint Center for Neuroscience and Neural Engineering, and Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong Province P. R. China
| | - Perry F. Bartlett
- grid.1003.20000 0000 9320 7537Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD Australia ,grid.1003.20000 0000 9320 7537Queensland Brain Institute, The University of Queensland, Brisbane, QLD Australia ,grid.263817.90000 0004 1773 1790Joint Center for Neuroscience and Neural Engineering, and Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong Province P. R. China
| | - Jürgen Götz
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD, Australia.
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15
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Ghoweri AO, Ouillette L, Frazier HN, Anderson KL, Lin RL, Gant JC, Parent R, Moore S, Murphy GG, Thibault O. Electrophysiological and Imaging Calcium Biomarkers of Aging in Male and Female 5×FAD Mice. J Alzheimers Dis 2020; 78:1419-1438. [PMID: 33164928 PMCID: PMC7836067 DOI: 10.3233/jad-200109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
BACKGROUND In animal models and tissue preparations, calcium dyshomeostasis is a biomarker of aging and Alzheimer's disease that is associated with synaptic dysfunction, neuritic pruning, and dysregulated cellular processes. It is unclear, however, whether the onset of calcium dysregulation precedes, is concurrent with, or is the product of pathological cellular events (e.g., oxidation, amyloid-β production, and neuroinflammation). Further, neuronal calcium dysregulation is not always present in animal models of amyloidogenesis, questioning its reliability as a disease biomarker. OBJECTIVE Here, we directly tested for the presence of calcium dysregulation in dorsal hippocampal neurons in male and female 5×FAD mice on a C57BL/6 genetic background using sharp electrodes coupled with Oregon-green Bapta-1 imaging. We focused on three ages that coincide with the course of amyloid deposition: 1.5, 4, and 10 months old. METHODS Outcome variables included measures of the afterhyperpolarization, short-term synaptic plasticity, and calcium kinetics during synaptic activation. Quantitative analyses of spatial learning and memory were also conducted using the Morris water maze. Main effects of sex, age, and genotype were identified on measures of electrophysiology and calcium imaging. RESULTS Measures of resting Oregon-green Bapta-1 fluorescence showed significant reductions in the 5×FAD group compared to controls. Deficits in spatial memory, along with increases in Aβ load, were detectable at older ages, allowing us to test for temporal associations with the onset of calcium dysregulation. CONCLUSION Our results provide evidence that reduced, rather than elevated, neuronal calcium is identified in this 5×FAD model and suggests that this surprising result may be a novel biomarker of AD.
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Affiliation(s)
- Adam O Ghoweri
- UKMC MS313, Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY, USA
| | - Lara Ouillette
- 5037 BSRB, Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Hilaree N Frazier
- UKMC MS313, Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY, USA
| | - Katie L Anderson
- UKMC MS313, Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY, USA
| | - Ruei-Lung Lin
- UKMC MS313, Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY, USA
| | - John C Gant
- UKMC MS313, Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY, USA
| | - Rachel Parent
- 5037 BSRB, Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Shannon Moore
- 5037 BSRB, Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA.,5037 BSRB, Molecular and Integrative Physiology, Michigan Neuroscience Institute, University of Michigan, Ann Arbor, MI, USA
| | - Geoffrey G Murphy
- 5037 BSRB, Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA.,5037 BSRB, Molecular and Integrative Physiology, Michigan Neuroscience Institute, University of Michigan, Ann Arbor, MI, USA
| | - Olivier Thibault
- UKMC MS313, Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY, USA
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16
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Chronic hyperglycemia impairs hippocampal neurogenesis and memory in an Alzheimer's disease mouse model. Neurobiol Aging 2020; 92:98-113. [PMID: 32417750 DOI: 10.1016/j.neurobiolaging.2020.04.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 03/25/2020] [Accepted: 04/06/2020] [Indexed: 12/30/2022]
Abstract
During aging, lifestyle-related factors shape the brain's response to insults and modulate the progression of neurodegenerative pathologies such as Alzheimer's disease (AD). This is the case for chronic hyperglycemia associated with type 2 diabetes, which reduces the brain's ability to handle the neurodegenerative burden associated with AD. However, the mechanisms behind the effects of chronic hyperglycemia in the context of AD are not fully understood. Here, we show that newly generated neurons in the hippocampal dentate gyrus of triple transgenic AD (3xTg-AD) mice present increased dendritic arborization and a number of synaptic puncta, which may constitute a compensatory mechanism allowing the animals to cope with a lower neurogenesis rate. Contrariwise, chronic hyperglycemia decreases the complexity and differentiation of 3xTg-AD newborn neurons and reduces the levels of β-catenin, a key intrinsic modulator of neuronal maturation. Moreover, synaptic facilitation is depressed in hyperglycemic 3xTg-AD mice, accompanying the defective hippocampal-dependent memory. Our data suggest that hyperglycemia evokes cellular and functional alterations that accelerate the onset of AD-related symptoms, namely memory impairment.
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17
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Circuit-specific control of the medial entorhinal inputs to the dentate gyrus by atypical presynaptic NMDARs activated by astrocytes. Proc Natl Acad Sci U S A 2019; 116:13602-13610. [PMID: 31152131 PMCID: PMC6612919 DOI: 10.1073/pnas.1816013116] [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] [Indexed: 11/18/2022] Open
Abstract
Here, we investigated the properties of presynaptic N-methyl-d-aspartate receptors (pre-NMDARs) at corticohippocampal excitatory connections between perforant path (PP) afferents and dentate granule cells (GCs), a circuit involved in memory encoding and centrally affected in Alzheimer's disease and temporal lobe epilepsy. These receptors were previously reported to increase PP release probability in response to gliotransmitters released from astrocytes. Their activation occurred even under conditions of elevated Mg2+ and lack of action potential firing in the axons, although how this could be accomplished was unclear. We now report that these pre-NMDARs contain the GluN3a subunit conferring them low Mg2+ sensitivity. GluN3a-containing NMDARs at PP-GC synapses are preponderantly presynaptic vs. postsynaptic and persist beyond the developmental period. Moreover, they are expressed selectively at medial-not lateral-PP axons and act to functionally enhance release probability specifically of the medial perforant path (MPP) input to GC dendrites. By controlling release probability, GluN3a-containing pre-NMDARs also control the dynamic range for long-term potentiation (LTP) at MPP-GC synapses, an effect requiring Ca2+ signaling in astrocytes. Consistent with the functional observations, GluN3a subunits in MPP terminals are localized at sites away from the presynaptic release sites, often facing astrocytes, in line with a primary role for astrocytic inputs in their activation. Overall, GluN3A-containing pre-NMDARs emerge as atypical modulators of dendritic computations in the MPP-GC memory circuit.
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18
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Barbieri R, Contestabile A, Ciardo MG, Forte N, Marte A, Baldelli P, Benfenati F, Onofri F. Synapsin I and Synapsin II regulate neurogenesis in the dentate gyrus of adult mice. Oncotarget 2018; 9:18760-18774. [PMID: 29721159 PMCID: PMC5922353 DOI: 10.18632/oncotarget.24655] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2017] [Accepted: 02/25/2018] [Indexed: 01/23/2023] Open
Abstract
Adult neurogenesis is emerging as an important player in brain functions and homeostasis, while impaired or altered adult neurogenesis has been associated with a number of neuropsychiatric diseases, such as depression and epilepsy. Here we investigated the possibility that synapsins (Syns) I and II, beyond their known functions in developing and mature neurons, also play a role in adult neurogenesis. We performed a systematic evaluation of the distinct stages of neurogenesis in the hippocampal dentate gyrus of Syn I and Syn II knockout (KO) mice, before (2-months-old) and after (6-months-old) the appearance of the epileptic phenotype. We found that Syns I and II play an important role in the regulation of adult neurogenesis. In juvenile mice, Syn II deletion was associated with a specific decrease in the proliferation of neuronal progenitors, whereas Syn I deletion impaired the survival of newborn neurons. These defects were reverted after the appearance of the epileptic phenotype, with Syn I KO and Syn II KO mice exhibiting significant increases in survival and proliferation, respectively. Interestingly, long-term potentiation dependent on newborn neurons was present in both juvenile Syn mutants while, at later ages, it was only preserved in Syn II KO mice that also displayed an increased expression of brain-derived neurotrophic factor. This study suggests that Syns I and II play a role in adult neurogenesis and the defects in neurogenesis associated with Syn deletion may contribute to the alterations of cognitive functions observed in Syn-deficient mice.
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Affiliation(s)
- Raffaella Barbieri
- Department of Experimental Medicine, University of Genova, 16132, Genova, Italy
| | - Andrea Contestabile
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, 16163, Genova, Italy
| | - Maria Grazia Ciardo
- Department of Experimental Medicine, University of Genova, 16132, Genova, Italy
| | - Nicola Forte
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, 16132, Genova, Italy
| | - Antonella Marte
- Department of Experimental Medicine, University of Genova, 16132, Genova, Italy
| | - Pietro Baldelli
- Department of Experimental Medicine, University of Genova, 16132, Genova, Italy.,Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, 16132, Genova, Italy
| | - Fabio Benfenati
- Department of Experimental Medicine, University of Genova, 16132, Genova, Italy.,Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, 16132, Genova, Italy
| | - Franco Onofri
- Department of Experimental Medicine, University of Genova, 16132, Genova, Italy
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Leal SL, Noche JA, Murray EA, Yassa MA. Age-related individual variability in memory performance is associated with amygdala-hippocampal circuit function and emotional pattern separation. Neurobiol Aging 2016; 49:9-19. [PMID: 27723500 DOI: 10.1016/j.neurobiolaging.2016.08.018] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2016] [Revised: 08/12/2016] [Accepted: 08/16/2016] [Indexed: 12/27/2022]
Abstract
While aging is generally associated with episodic memory decline, not all older adults exhibit memory loss. Furthermore, emotional memories are not subject to the same extent of forgetting and appear preserved in aging. We conducted high-resolution fMRI during a task involving pattern separation of emotional information in older adults with and without age-related memory impairment (characterized by performance on a word-list learning task: low performers: LP vs. high performers: HP). We found signals consistent with emotional pattern separation in hippocampal dentate (DG)/CA3 in HP but not in LP individuals, suggesting a deficit in emotional pattern separation. During false recognition, we found increased DG/CA3 activity in LP individuals, suggesting that hyperactivity may be associated with overgeneralization. We additionally observed a selective deficit in basolateral amygdala-lateral entorhinal cortex-DG/CA3 functional connectivity in LP individuals during pattern separation of negative information. During negative false recognition, LP individuals showed increased medial temporal lobe functional connectivity, consistent with overgeneralization. Overall, these results suggest a novel mechanistic account of individual differences in emotional memory alterations exhibited in aging.
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Affiliation(s)
- Stephanie L Leal
- Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, CA, USA; Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD, USA
| | - Jessica A Noche
- Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, CA, USA
| | - Elizabeth A Murray
- Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, CA, USA
| | - Michael A Yassa
- Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, CA, USA.
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20
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Hayama T, Murakami K, Watanabe T, Maeda R, Kamata M, Kondo S. Single administration of a novel γ-secretase modulator ameliorates cognitive dysfunction in aged C57BL/6J mice. Brain Res 2016; 1633:52-61. [PMID: 26707406 DOI: 10.1016/j.brainres.2015.12.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Revised: 12/03/2015] [Accepted: 12/11/2015] [Indexed: 10/22/2022]
Abstract
Mutations in presenilin 1 (PS1) and presenilin 2 (PS2) are known to cause early onset of Alzheimer's disease (AD). These proteins comprise the catalytic domain of γ-secretase, which catalyzes the cleavage of β-amyloid (Aβ) from amyloid precursor protein (APP). In recent reports, PS1 and PS2 were linked to the modulation of intracellular calcium ion (Ca(2+)) dynamics, a key regulator of synaptic function. Ca(2+) dysregulation and synaptic dysfunction are leading hypothesis of cognitive dysfunctions during aging and AD progression. Accordingly, manipulations of presenilins by small molecules may have therapeutic potential for the treatment of cognitive dysfunction. In an accompanying report, we showed that chronic treatment with compound-1, a novel γ-secretase modulator (GSM), reduced Aβ production and ameliorated cognitive dysfunction in Tg2576 APP transgenic mice. Accordingly, in the present study we showed that single oral administration of compound-1 at 1 and 3mg/kg ameliorated cognitive dysfunction in aged non-transgenic mice. Moreover, compound-1 enhanced synaptic plasticity in hippocampal slices from aged C57BL/6J mice and increased messenger RNA (mRNA) expression of the immediate early gene c-fos, which has been shown to be related to synaptic plasticity in vivo. Finally, compound-1 modulated Ca(2+) signals through PS1 in mouse embryonic fibroblast cells. Taken together, compound-1 ameliorates both Aβ pathology and age-related cognitive dysfunctions. Hence, compound-1 may have potential as an early intervention for the cognitive declines that are commonly diagnosed in aged subjects, such as mild cognitive impairment (MCI) and prodromal AD.
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Affiliation(s)
- Tatsuya Hayama
- CNS Drug Discovery Unit, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1 Muraoka-higashi 2-chome, Fujisawa, Kanagawa 251-8555, Japan
| | - Koji Murakami
- CNS Drug Discovery Unit, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1 Muraoka-higashi 2-chome, Fujisawa, Kanagawa 251-8555, Japan
| | - Tomomichi Watanabe
- CNS Drug Discovery Unit, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1 Muraoka-higashi 2-chome, Fujisawa, Kanagawa 251-8555, Japan
| | - Ryota Maeda
- CNS Drug Discovery Unit, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1 Muraoka-higashi 2-chome, Fujisawa, Kanagawa 251-8555, Japan
| | - Makoto Kamata
- CNS Drug Discovery Unit, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1 Muraoka-higashi 2-chome, Fujisawa, Kanagawa 251-8555, Japan
| | - Shinichi Kondo
- CNS Drug Discovery Unit, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1 Muraoka-higashi 2-chome, Fujisawa, Kanagawa 251-8555, Japan.
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21
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Bates SL, Wolbers T. How cognitive aging affects multisensory integration of navigational cues. Neurobiol Aging 2014; 35:2761-2769. [DOI: 10.1016/j.neurobiolaging.2014.04.003] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 03/06/2014] [Accepted: 04/02/2014] [Indexed: 11/16/2022]
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22
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Dutta Roy R, Stefan MI, Rosenmund C. Biophysical properties of presynaptic short-term plasticity in hippocampal neurons: insights from electrophysiology, imaging and mechanistic models. Front Cell Neurosci 2014; 8:141. [PMID: 24904286 PMCID: PMC4033079 DOI: 10.3389/fncel.2014.00141] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 05/01/2014] [Indexed: 11/16/2022] Open
Abstract
Hippocampal neurons show different types of short-term plasticity (STP). Some exhibit facilitation of their synaptic responses and others depression. In this review we discuss presynaptic biophysical properties behind heterogeneity in STP in hippocampal neurons such as alterations in vesicle priming and docking, fusion, neurotransmitter filling and vesicle replenishment. We look into what types of information electrophysiology, imaging and mechanistic models have given about the time scales and relative impact of the different properties on STP with an emphasis on the use of mechanistic models as complementary tools to experimental procedures. Taken together this tells us that it is possible for a multitude of different mechanisms to underlie the same STP pattern, even though some are more important in specific cases, and that mechanistic models can be used to integrate the biophysical properties to see which mechanisms are more important in specific cases of STP.
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Affiliation(s)
- Ranjita Dutta Roy
- Department of Medicine Solna, Karolinska Insitutet Stockholm, Sweden ; Neuroscience Research Center (NWFZ), Charite Universitatsmedizin Berlin, Germany
| | - Melanie I Stefan
- Department of Neurobiology, Harvard Medical School Boston, MA, USA
| | - Christian Rosenmund
- Neuroscience Research Center (NWFZ), Charite Universitatsmedizin Berlin, Germany
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23
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Petersen R, Moradpour F, Eadie B, Shin J, Kannangara T, Delaney K, Christie B. Electrophysiological identification of medial and lateral perforant path inputs to the dentate gyrus. Neuroscience 2013; 252:154-68. [DOI: 10.1016/j.neuroscience.2013.07.063] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 07/23/2013] [Accepted: 07/27/2013] [Indexed: 10/26/2022]
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Scharfman HE, Chao MV. The entorhinal cortex and neurotrophin signaling in Alzheimer's disease and other disorders. Cogn Neurosci 2013; 4:123-35. [PMID: 24168199 PMCID: PMC3836904 DOI: 10.1080/17588928.2013.826184] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A major problem in the field of neurodegeneration is the basis of selective vulnerability of subsets of neurons to disease. In aging, Alzheimer's disease (AD), and other disorders such as temporal lobe epilepsy, the superficial layers of the entorhinal cortex (EC) are an area of selective vulnerability. In AD, it has been suggested that the degeneration of these neurons may play a role in causing the disease because it occurs at an early stage. Therefore, it is important to define the distinctive characteristics of the EC that make this region particularly vulnerable. It has been shown that neurotrophins such as brain-derived neurotrophic factor (BDNF) are critical to the maintenance of the cortical neurons in the adult brain, and specifically the EC. Here we review the circuitry, distinctive functions, and neurotrophin-dependence of the EC that are relevant to its vulnerability. We also suggest that a protein that is critical to the actions of BDNF, the ARMS/Kidins220 scaffold protein, plays an important role in neurotrophic support of the EC.
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Affiliation(s)
- Helen E Scharfman
- a Departments of Child & Adolescent Psychiatry, Physiology & Neuroscience and Psychiatry , New York University Langone Medical Center , New York , NY , USA
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25
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Vivar C, van Praag H. Functional circuits of new neurons in the dentate gyrus. Front Neural Circuits 2013; 7:15. [PMID: 23443839 PMCID: PMC3580993 DOI: 10.3389/fncir.2013.00015] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 01/23/2013] [Indexed: 01/17/2023] Open
Abstract
The hippocampus is crucial for memory formation. New neurons are added throughout life to the hippocampal dentate gyrus (DG), a brain area considered important for differential storage of similar experiences and contexts. To better understand the functional contribution of adult neurogenesis to pattern separation processes, we recently used a novel synapse specific trans-neuronal tracing approach to identify the (sub) cortical inputs to new dentate granule cells (GCs). It was observed that newly born neurons receive sequential innervation from structures important for memory function. Initially, septal-hippocampal cells provide input to new neurons, including transient innervation from mature GCs as well as direct feedback from area CA3 pyramidal neurons. After about 1 month perirhinal (PRH) and lateral entorhinal cortex (LEC), brain areas deemed relevant to integration of novel sensory and environmental information, become substantial input to new GCs. Here, we review the developmental time-course and proposed functional relevance of new neurons, within the context of their unique neural circuitry.
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Affiliation(s)
- Carmen Vivar
- Neuroplasticity and Behavior Unit, Laboratory of Neurosciences, Intramural Research Program, National Institute on Aging, National Institutes of Health Baltimore, MD, USA
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Sex Differences in Presynaptic Density and Neurogenesis in Middle-Aged ApoE4 and ApoE Knockout Mice. JOURNAL OF NEURODEGENERATIVE DISEASES 2013; 2013:531326. [PMID: 26316992 PMCID: PMC4437335 DOI: 10.1155/2013/531326] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 01/02/2013] [Indexed: 11/29/2022]
Abstract
Atherosclerosis and apolipoprotein E ε4 (APOE4) genotype are risk factors for Alzheimer's disease (AD) and cardiovascular disease (CVD). Sex differences exist in prevalence and manifestation of both diseases. We investigated sex differences respective to aging, focusing on cognitive parameters in apoE4 and apoE knockout (ko) mouse models of AD and CVD. Presynaptic density and neurogenesis were investigated immunohistochemically in male and female apoE4, apoE ko, and wild-type mice. Middle-aged female apoE4 mice showed decreased presynaptic density in the inner molecular layer of the dentate gyrus of the hippocampus. Middle-aged female apoE ko mice showed a trend towards increased neurogenesis in the hippocampus compared with wild-type mice. No differences in these parameters could be observed in middle-aged male mice. Specific harmful interactions between apoE4 and estrogen could be responsible for decreased presynaptic density in female apoE4 mice. The trend of increased neurogenesis found in female apoE ko mice supports previous studies suggesting that temporarily increased amount of synaptic contacts and/or neurogenesis is a compensatory mechanism for synaptic failure. To our knowledge, no other studies investigating presynaptic density in aging female apoE4 or apoE ko mice are available. Sex-specific differences between APOE genotypes could account for some sex differences in AD and CVD.
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Hornick A, Lieb A, Vo NP, Rollinger JM, Stuppner H, Prast H. The coumarin scopoletin potentiates acetylcholine release from synaptosomes, amplifies hippocampal long-term potentiation and ameliorates anticholinergic- and age-impaired memory. Neuroscience 2011; 197:280-92. [PMID: 21945033 PMCID: PMC3212650 DOI: 10.1016/j.neuroscience.2011.09.006] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2011] [Revised: 08/17/2011] [Accepted: 09/06/2011] [Indexed: 12/22/2022]
Abstract
In a previous study the simple, naturally derived coumarin scopoletin (SCT) was identified as an inhibitor of acetylcholinesterase (AChE), using a pharmacophore-based virtual screening approach. In this study the potential of SCT as procholinergic and cognition-enhancing therapeutic was investigated in a more detailed way, using different experimental approaches like measuring newly synthesized acetylcholine (ACh) in synaptosomes, long-term potentiation (LTP) experiments in hippocampal slices, and behavior studies. SCT enhanced the K+-stimulated release of ACh from rat frontal cortex synaptosomes, showing a bell-shaped dose effect curve (Emax: 4 μM). This effect was blocked by the nicotinic ACh receptor (nAChR) antagonists mecamylamine (MEC) and dihydro-β-erythroidine (DHE). The nAChR agonist (and AChE inhibitor) galantamine induced a similar increase in ACh release (Emax: 1 μM). SCT potentiated LTP in hippocampal slices of rat brain. The high-frequency stimulation (HFS)-induced, N-methyl-D-aspartate (NMDA) receptor dependent LTP of field excitatory postsynaptic potentials at CA3-CA1 synapses was greatly enhanced by pre-HFS application of SCT (4 μM for 4 min). This effect was mimicked by nicotine (2 μM) and abolished by MEC, suggesting an effect on nAChRs. SCT did not restore the total inhibition of LTP by NMDA receptor antagonist d, l-2-amino-5-phosphonopentanoic acid (AP-5). SCT (2 μg, i.c.v.) increased T-maze alternation and ameliorated novel object recognition of mice with scopolamine-induced cholinergic deficit. It also reduced age-associated deficits in object memory of 15–18-month-old mice (2 mg/kg sc). Our findings suggest that SCT possesses memory-improving properties, which are based on its direct nAChR agonistic activity. Therefore, SCT might be able to rescue impaired cholinergic functions by enhancing nAChR-mediated release of neurotransmitters and promoting neural plasticity in hippocampus.
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Affiliation(s)
- A Hornick
- Institute of Pharmacy/Pharmacology and Toxicology, University of Innsbruck, Peter-Mayr-Str.1, A-6020 Innsbruck, Austria
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Selective vulnerability of neurons in layer II of the entorhinal cortex during aging and Alzheimer's disease. Neural Plast 2010; 2010:108190. [PMID: 21331296 PMCID: PMC3039218 DOI: 10.1155/2010/108190] [Citation(s) in RCA: 131] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Accepted: 10/26/2010] [Indexed: 01/04/2023] Open
Abstract
All neurons are not created equal. Certain cell populations in specific brain regions are more susceptible to age-related changes that initiate regional and system-level dysfunction. In this respect, neurons in layer II of the entorhinal cortex are selectively vulnerable in aging and Alzheimer's disease (AD). This paper will cover several hypotheses that attempt to account for age-related alterations among this cell population. We consider whether specific developmental, anatomical, or biochemical features of neurons in layer II of the entorhinal cortex contribute to their particular sensitivity to aging and AD. The entorhinal cortex is a functionally heterogeneous environment, and we will also review data suggesting that, within the entorhinal cortex, there is subregional specificity for molecular alterations that may initiate cognitive decline. Taken together, the existing data point to a regional cascade in which entorhinal cortical alterations directly contribute to downstream changes in its primary afferent region, the hippocampus.
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Altered distribution of mGlu2 receptors in β-amyloid-affected brain regions of Alzheimer cases and aged PS2APP mice. Brain Res 2010; 1363:180-90. [PMID: 20875805 DOI: 10.1016/j.brainres.2010.09.072] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Revised: 09/16/2010] [Accepted: 09/19/2010] [Indexed: 01/28/2023]
Abstract
Altered glutamatergic synaptic transmission is among the key events defining the course of Alzheimer's disease (AD). mGlu2 receptors, a subtype of group II metabotropic glutamate receptors, regulate (as autoreceptors) fast synaptic transmission in the CNS via the controlled release of the excitatory amino acid glutamate. Since their pharmacological manipulation in rodents has been reported to affect cognition, they are potential drug targets for AD therapy. We examined the fate of these receptors in cases of AD as well as in aging PS2APP mice--a proposed model of the disease. In vitro binding of [(3)H]LY354740, a selective group II agonist (with selective affinity for mGlu2 receptors, under the assay conditions used) and quantitative radioautography revealed a partial, but highly significant, loss of receptors in amyloid-affected discrete brain regions of AD cases and PS2APP mice. Among the mouse brain regions affected were, above all, the subiculum but also frontolateral cortex, dentate gyrus, lacunosum moleculare and caudate putamen. In AD, significant receptor losses were registered in entorhinal cortex and lacunosum moleculare (40% and 35%, respectively). These findings have implications for the development of selective ligands for symptomatic therapy in AD and for its diagnosis.
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Stranahan AM, Haberman RP, Gallagher M. Cognitive decline is associated with reduced reelin expression in the entorhinal cortex of aged rats. ACTA ACUST UNITED AC 2010; 21:392-400. [PMID: 20538740 DOI: 10.1093/cercor/bhq106] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Brain regions and neural circuits differ in their vulnerability to changes that occur during aging and in age-related neurodegenerative diseases. Among the areas that comprise the medial temporal lobe memory system, the layer II neurons of the entorhinal cortex, which form the perforant path input to the hippocampal formation, exhibit early alterations over the course of aging Reelin, a glycoprotein implicated in synaptic plasticity, is expressed by entorhinal cortical layer II neurons. Here, we report that an age-related reduction in reelin expression in the entorhinal cortex is associated with cognitive decline. Using immunohistochemistry and in situ hybridization, we observed decreases in the number of Reelin-immunoreactive cells and reelin messenger RNA expression in the lateral entorhinal cortex of aged rats that are cognitively impaired relative to young adults and aged rats with preserved cognitive abilities. The lateral entorhinal cortex of aged rats with cognitive impairment also exhibited changes in other molecular markers, including increased accumulation of phosphorylated tau and decreased synaptophysin immunoreactivity. Taken together, these findings suggest that reduced reelin expression, emanating from layer II entorhinal neurons, may contribute to network dysfunction that occurs during memory loss in aging.
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Affiliation(s)
- Alexis M Stranahan
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD 21218, USA
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Aging and alpha-synuclein affect synaptic plasticity in the dentate gyrus. J Neural Transm (Vienna) 2008; 116:13-22. [PMID: 19002552 DOI: 10.1007/s00702-008-0149-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Accepted: 10/20/2008] [Indexed: 10/21/2022]
Abstract
Although intracellular accumulation of alpha-synuclein (alpha-syn) is a characteristic pathological change in Parkinson's disease, Lewy body dementia and Alzheimer's disease, the normal function of this presynaptic protein is still unknown. To assess the contribution of alpha-syn to synaptic plasticity as well as to age-related synaptic degeneration in mice, we compared adult and aged mice overexpressing mutated (A30P) human alpha-syn with their nontransgenic littermates using behavioral tests and electrophysiological measures in the dentate gyrus. We found decreased basal synaptic transmission and paired-pulse facilitation in the perforant path-dentate granule cell synapses of aged mice. In addition, alpha-syn accumulation in aged A30P mice but not in aged wild-type mice led to long-term depression of synaptic transmission after a stimulation protocol that normally induces long-term potentiation. These findings suggest that overexpression of mutated alpha-syn exacerbates the aging process and leads to impaired synaptic plasticity.
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Molecular bases of caloric restriction regulation of neuronal synaptic plasticity. Mol Neurobiol 2008; 38:167-77. [PMID: 18759009 DOI: 10.1007/s12035-008-8040-1] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2008] [Accepted: 08/14/2008] [Indexed: 12/23/2022]
Abstract
Aging is associated with the decline of cognitive properties. This situation is magnified when neurodegenerative processes associated with aging appear in human patients. Neuronal synaptic plasticity events underlie cognitive properties in the central nervous system. Caloric restriction (CR; either a decrease in food intake or an intermittent fasting diet) can extend life span and increase disease resistance. Recent studies have shown that CR can have profound effects on brain function and vulnerability to injury and disease. Moreover, CR can stimulate the production of new neurons from stem cells (neurogenesis) and can enhance synaptic plasticity, which modulate pain sensation, enhance cognitive function, and may increase the ability of the brain to resist aging. The beneficial effects of CR appear to be the result of a cellular stress response stimulating the production of proteins that enhance neuronal plasticity and resistance to oxidative and metabolic insults; they include neurotrophic factors, neurotransmitter receptors, protein chaperones, and mitochondrial biosynthesis regulators. In this review, we will present and discuss the effect of CR in synaptic processes underlying analgesia and cognitive improvement in healthy, sick, and aging animals. We will also discuss the possible role of mitochondrial biogenesis induced by CR in regulation of neuronal synaptic plasticity.
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Murphy GG, Shah V, Hell JW, Silva AJ. Investigation of age-related cognitive decline using mice as a model system: neurophysiological correlates. Am J Geriatr Psychiatry 2006; 14:1012-21. [PMID: 17138808 DOI: 10.1097/01.jgp.0000209404.54310.b3] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Learning and memory impairments without overt pathology often accompany advancing age. To gain a better understanding of the underlying neuronal substrates associated with this age-related cognitive decline, the authors have begun to use mice as an animal model system. As described in the companion paper, mice exhibit age-related impairments in cognition. Here, the authors explore the possibility that age-related changes in neuronal function may be the result of deregulation of cytosolic free calcium homeostasis. METHODS Calcium homeostasis in young and aged mice was examined by measuring the slow afterhyperpolarization (sAHP) in hippocampal neurons as well as assessing voltage-dependent calcium channel mediated long-term potentiation (vdccLTP). In addition, putative changes in phosphorylation of the L-type channel Ca(V)1.2 by cAMP-dependent protein kinase were examined. RESULTS Both neurophysiological measures of calcium homeostasis indicated an increase in activity-dependent calcium influx. This increase was not the result of an age-related increase in phosphorylation of the L-type channel Ca(V)1.2 by cAMP-dependent protein kinase. CONCLUSIONS Like in other areas of biomedical research, mice have become an invaluable research tool in the investigation of learning and memory. It is expected that similar benefits can be realized by developing mouse models for age-related cognitive decline.
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Affiliation(s)
- Geoffrey G Murphy
- Department of Neurobiology, Brain Research Institute, University of California, Los Angeles, Los Angeles, CA 90095-1761, USA
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Akopian G, Walsh JP. Pre- and postsynaptic contributions to age-related alterations in corticostriatal synaptic plasticity. Synapse 2006; 60:223-38. [PMID: 16739119 DOI: 10.1002/syn.20289] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Aging creates deficits in motor performance related to changes in striatal processing of cortical information. This study describes age-related changes in corticostriatal snaptic plasticity and associated mechanisms, which may contribute to declines in motor behavior. Intracellular recordings revealed an age-related decrease in the expression of paired-pulse, posttetanic, and long-term potentiation (LTP). The age-related difference in LTP was associated with reduced sensitivity to block of N-methyl-D-aspartate (NMDA) receptors in the aged population. These age-related changes could not be explained by increased L-type Ca(2+)channel activity, since block of L-type Ca(2+) channels with nifedipine increased rather than decreased the age-related difference in long-term plasticity. Age-related increases in reactive oxygen species (ROS) modulation were also ruled out, since application of H(2)O(2) produced changes in synaptic function that were opposite to trends seen in aging, and addition of the antioxidant Trolox-C had a larger effect on long-term plasticity in young rats than in older rats. A robust age-related difference in long-term synaptic plasticity was found by studying synaptic plasticity following the blocking of D2 receptors with l-sulpiride, which may involve age-difference in NMDA receptor function. l-sulpiride consistently enabled a slow development of LTP at young (but not aged) corticostriatal synapses. However, No age differences were found in the sensitivity to the addition of the D2 receptor agonist quinpirole. These findings provide evidence for age-induced changes in the release properties of cortical terminals and in the functioning of postsynaptic striatal NMDA receptors, which may contribute to age-related deficits in striatum control of movement.
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Affiliation(s)
- G Akopian
- Andrus Gerontology Center, USC Program in Neuroscience, University of Southern California, Los Angeles, California 90089-0191, USA
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Christie BR, Li AM, Redila VA, Booth H, Wong BKY, Eadie BD, Ernst C, Simpson EM. Deletion of the nuclear receptor Nr2e1 impairs synaptic plasticity and dendritic structure in the mouse dentate gyrus. Neuroscience 2005; 137:1031-7. [PMID: 16289828 DOI: 10.1016/j.neuroscience.2005.08.091] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2005] [Revised: 07/14/2005] [Accepted: 08/15/2005] [Indexed: 11/17/2022]
Abstract
The spontaneous or targeted deletion of the nuclear receptor transcription factor Nr2e1 produces a mouse that shows hypoplasia of the hippocampal formation and reduced neurogenesis in adult mice. In these studies we show that hippocampal synaptic transmission appears normal in the dentate gyrus and cornu ammonis 1 subfields of adult mice that lack Nr2e1 (Nr2e1-/-), and that fEPSP shape, paired-pulse responses, and short-term plasticity are not substantially altered in either subfield. In contrast, the expression of long-term potentiation is selectively impaired in the dentate gyrus, and not in the cornu ammonis 1 subfield. Golgi analysis revealed that there was a significant reduction in both dendritic branching and dendritic length that was specific to dentate gyrus granule cells in the Nr2e1-/- mice. These results indicate that Nr2e1 deletion can significantly alter both synaptic plasticity and dendritic structure in the dentate gyrus.
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Affiliation(s)
- B R Christie
- Department of Psychology, University of British Columbia, 2136 West Mall, Vancouver, British Columbia, Canada V6T 1Z4.
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Zheng K, Kuteeva E, Xia S, Bartfai T, Hökfelt T, Xu ZQD. Age-related impairments of synaptic plasticity in the lateral perforant path input to the dentate gyrus of galanin overexpressing mice. Neuropeptides 2005; 39:259-67. [PMID: 15944020 DOI: 10.1016/j.npep.2005.02.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2005] [Accepted: 02/15/2005] [Indexed: 11/17/2022]
Abstract
In the present study, electrophysiological recordings were made from hippocampal slices obtained from mice overexpressing galanin under the promoter for the platelet-derived growth factor-B (GalOE mice). In these mice, a particularly strong galanin expression is seen in the granule cell layer/mossy fibers. Paired-pulse facilitation (PPF) of excitatory postsynaptic field potentials (fEPSPs) at the lateral perforant path (LPP)-dentate gyrus synapses was elicited in the dentate gyrus after stimulation with different interpulse intervals. Slices from young adult wild-type (WT) animals showed significant PPF of the 2nd EPSP evoked with paired-pulse stimuli, while PPF was reduced in slices from young adult GalOE mice, as well as aged WT mice, but were not observed at all in slices from aged GalOE animals. Application of the putative galanin antagonist M35 increased PPF in slices from aged WT mice as well as from adult and aged GalOE mice, but had no effect in slices taken from young adult WT mice. These data indicate that galanin is involved in hippocampal synaptic plasticity, in particular in age-related reduction of synaptic plasticity in the LPP input to the dentate gyrus. Galaninergic mechanisms may therefore represent therapeutic targets for treatment of age-related memory deficits and Alzheimer's disease.
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Affiliation(s)
- Kang Zheng
- Department of Neuroscience, Karolinska Institutet, S-171 71, Stockholm, Sweden
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