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Yamamoto N, Yokose J, Ramesh K, Kitamura T, Ogawa SK. Outer layer of Vb neurons in medial entorhinal cortex project to hippocampal dentate gyrus in mice. Mol Brain 2024; 17:5. [PMID: 38317261 PMCID: PMC10845563 DOI: 10.1186/s13041-024-01079-5] [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: 11/07/2023] [Accepted: 01/25/2024] [Indexed: 02/07/2024] Open
Abstract
Entorhinal cortical (EC)-hippocampal (HPC) circuits are crucial for learning and memory. Although it was traditionally believed that superficial layers (II/III) of the EC mainly project to the HPC and deep layers (V/VI) receive input from the HPC, recent studies have highlighted the significant projections from layers Va and VI of the EC into the HPC. However, it still remains unknown whether Vb neurons in the EC provide projections to the hippocampus. In this study, using a molecular marker for Vb and retrograde tracers, we identified that the outer layer of Vb neurons in the medial EC (MEC) directly project to both dorsal and ventral hippocampal dentate gyrus (DG), with a significant preference for the ventral DG. In contrast to the distribution of DG-projecting Vb cells, anterior thalamus-projecting Vb cells are distributed through the outer to the inner layer of Vb. Furthermore, dual tracer injections revealed that DG-projecting Vb cells and anterior thalamus-projecting Vb cells are distinct populations. These results suggest that the roles of MEC Vb neurons are not merely limited to the formation of EC-HPC loop circuits, but rather contribute to multiple neural processes for learning and memory.
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Affiliation(s)
- Naoki Yamamoto
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Jun Yokose
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Kritika Ramesh
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Takashi Kitamura
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
- Peter O'Donnell Jr. Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
| | - Sachie K Ogawa
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
- Peter O'Donnell Jr. Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
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2
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Gusain P, Taketoshi M, Tominaga Y, Tominaga T. Functional Dissection of Ipsilateral and Contralateral Neural Activity Propagation Using Voltage-Sensitive Dye Imaging in Mouse Prefrontal Cortex. eNeuro 2023; 10:ENEURO.0161-23.2023. [PMID: 37977827 DOI: 10.1523/eneuro.0161-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 11/03/2023] [Accepted: 11/10/2023] [Indexed: 11/19/2023] Open
Abstract
Prefrontal cortex (PFC) intrahemispheric activity and the interhemispheric connection have a significant impact on neuropsychiatric disorder pathology. This study aimed to generate a functional map of FC intrahemispheric and interhemispheric connections. Functional dissection of mouse PFCs was performed using the voltage-sensitive dye (VSD) imaging method with high speed (1 ms/frame), high resolution (256 × 256 pixels), and a large field of view (∼10 mm). Acute serial 350 μm slices were prepared from the bregma covering the PFC and numbered 1-5 based on their distance from the bregma (i.e., 1.70, 1.34, 0.98, 0.62, and 0.26 mm) with reference to the Mouse Brain Atlas (Paxinos and Franklin, 2008). The neural response to electrical stimulation was measured at nine sites and then averaged, and a functional map of the propagation patterns was created. Intracortical propagation was observed in slices 3-5, encompassing the anterior cingulate cortex (ACC) and corpus callosum (CC). The activity reached area 33 of the ACC. Direct white matter stimulation activated area 33 in both hemispheres. Similar findings were obtained via DiI staining of the CC. Imaging analysis revealed directional biases in neural signals traveling within the ACC, whereby the signal transmission speed and probability varied based on the signal direction. Specifically, the spread of neural signals from cg2 to cg1 was stronger than that from cingulate cortex area 1(cg1) to cingulate cortex area 2(cg2), which has implications for interhemispheric functional connections. These findings highlight the importance of understanding the PFC functional anatomy in evaluating neuromodulators like serotonin and dopamine, as well as other factors related to neuropsychiatric diseases.
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Affiliation(s)
- Pooja Gusain
- Institute of Neuroscience, Tokushima Bunri University, Sanuki 769-2193, Japan
| | - Makiko Taketoshi
- Institute of Neuroscience, Tokushima Bunri University, Sanuki 769-2193, Japan
| | - Yoko Tominaga
- Institute of Neuroscience, Tokushima Bunri University, Sanuki 769-2193, Japan
| | - Takashi Tominaga
- Institute of Neuroscience, Tokushima Bunri University, Sanuki 769-2193, Japan
- Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Sanuki 769-2193, Japan
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3
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Beesley S, Gunjan A, Kumar SS. Visualizing the triheteromeric N-methyl-D-aspartate receptor subunit composition. Front Synaptic Neurosci 2023; 15:1156777. [PMID: 37292368 PMCID: PMC10244591 DOI: 10.3389/fnsyn.2023.1156777] [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: 02/01/2023] [Accepted: 05/10/2023] [Indexed: 06/10/2023] Open
Abstract
N-methyl-D-aspartate receptors (NMDARs) are one of three ligand-gated ionotropic channels that transduce the effects of neurotransmitter glutamate at excitatory synapses within the central nervous system. Their ability to influx Ca2+ into cells, unlike mature AMPA or kainate receptors, implicates them in a variety of processes ranging from synaptic plasticity to cell death. Many of the receptor's capabilities, including binding glutamate and regulating Ca2+ influx, have been attributed to their subunit composition, determined putatively using cell biology, electrophysiology and/or pharmacology. Here, we show that subunit composition of synaptic NMDARs can also be readily visualized in acute brain slices (rat) using highly specific antibodies directed against extracellular epitopes of the subunit proteins and high-resolution confocal microscopy. This has helped confirm the expression of triheteromeric t-NMDARs (containing GluN1, GluN2, and GluN3 subunits) at synapses for the first time and reconcile functional differences with diheteromeric d-NMDARs (containing GluN1 and GluN2 subunits) described previously. Even though structural information about individual receptors is still diffraction limited, fluorescently tagged receptor subunit puncta coalesce with precision at various magnifications and/or with the postsynaptic density (PSD-95) but not the presynaptic active zone marker Bassoon. These data are particularly relevant for identifying GluN3A-containing t-NMDARs that are highly Ca2+ permeable and whose expression at excitatory synapses renders neurons vulnerable to excitotoxicity and cell death. Imaging NMDAR subunit proteins at synapses not only offers firsthand insights into subunit composition to correlate function but may also help identify zones of vulnerability within brain structures underlying neurodegenerative diseases like Temporal Lobe Epilepsy.
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Affiliation(s)
| | | | - Sanjay S. Kumar
- Department of Biomedical Sciences, College of Medicine and Program in Neuroscience, Florida State University, Tallahassee, FL, United States
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4
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Limbic and olfactory cortical circuits in focal seizures. Neurobiol Dis 2023; 178:106007. [PMID: 36682502 DOI: 10.1016/j.nbd.2023.106007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Revised: 01/17/2023] [Accepted: 01/18/2023] [Indexed: 01/22/2023] Open
Abstract
Epilepsies affecting the limbic regions are common and generate seizures often resistant to pharmacological treatment. Clinical evidence demonstrates that diverse regions of the mesial portion of the temporal lobe participate in limbic seizures; these include the hippocampus, the entorhinal, perirhinal and parahippocampal regions and the piriform cortex. The network mechanisms involved in the generation of olfactory-limbic epileptiform patterns will be here examined, with particular emphasis on acute interictal and ictal epileptiform discharges obtained by treatment with pro-convulsive drugs and by high-frequency stimulations on in vitro preparations, such as brain slices and the isolated guinea pig brain. The interactions within olfactory-limbic circuits can be summarized as follows: independent, region-specific seizure-like events (SLE) are generated in the olfactory and in the limbic cortex; SLEs generated in the hippocampal-parahippocampal regions tend to remain within these areas; the perirhinal region controls the neocortical propagation and the generalization of limbic seizures; interictal spiking in the olfactory regions prevents the invasion by SLEs generated in limbic regions. The potential relevance of these observations for human focal epilepsy is discussed.
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Ohara S, Rannap M, Tsutsui KI, Draguhn A, Egorov AV, Witter MP. Hippocampal-medial entorhinal circuit is differently organized along the dorsoventral axis in rodents. Cell Rep 2023; 42:112001. [PMID: 36680772 DOI: 10.1016/j.celrep.2023.112001] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 10/14/2022] [Accepted: 12/31/2022] [Indexed: 01/21/2023] Open
Abstract
The general understanding of hippocampal circuits is that the hippocampus and the entorhinal cortex (EC) are topographically connected through parallel identical circuits along the dorsoventral axis. Our anterograde tracing and in vitro electrophysiology data, however, show a markedly different dorsoventral organization of the hippocampal projection to the medial EC (MEC). While dorsal hippocampal projections are confined to the dorsal MEC, ventral hippocampal projections innervate both dorsal and ventral MEC. Further, whereas the dorsal hippocampus preferentially targets layer Vb (LVb) neurons, the ventral hippocampus mainly targets cells in layer Va (LVa). This connectivity scheme differs from hippocampal projections to the lateral EC, which are topographically organized along the dorsoventral axis. As LVa neurons project to telencephalic structures, our findings indicate that the ventral hippocampus regulates LVa-mediated entorhinal-neocortical output from both dorsal and ventral MEC. Overall, the marked dorsoventral differences in hippocampal-entorhinal connectivity impose important constraints on signal flow in hippocampal-neocortical circuits.
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Affiliation(s)
- Shinya Ohara
- Laboratory of Systems Neuroscience, Tohoku University Graduate School of Life Sciences, Sendai, Japan; Kavli Institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and Technology, Trondheim, Norway; PRESTO, Japan Science and Technology Agency (JST), Tokyo, Japan
| | - Märt Rannap
- Institute of Physiology and Pathophysiology, Medical Faculty, Heidelberg University, Heidelberg, Germany
| | - Ken-Ichiro Tsutsui
- Laboratory of Systems Neuroscience, Tohoku University Graduate School of Life Sciences, Sendai, Japan
| | - Andreas Draguhn
- Institute of Physiology and Pathophysiology, Medical Faculty, Heidelberg University, Heidelberg, Germany
| | - Alexei V Egorov
- Institute of Physiology and Pathophysiology, Medical Faculty, Heidelberg University, Heidelberg, Germany.
| | - Menno P Witter
- Kavli Institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and Technology, Trondheim, Norway.
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6
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Mello e Souza T. Unraveling molecular and system processes for fear memory. Neuroscience 2022; 497:14-29. [DOI: 10.1016/j.neuroscience.2022.03.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 03/02/2022] [Accepted: 03/14/2022] [Indexed: 11/26/2022]
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Blankvoort S, Olsen LC, Kentros CG. Single Cell Transcriptomic and Chromatin Profiles Suggest Layer Vb Is the Only Layer With Shared Excitatory Cell Types in the Medial and Lateral Entorhinal Cortex. Front Neural Circuits 2022; 15:806154. [PMID: 35153682 PMCID: PMC8826650 DOI: 10.3389/fncir.2021.806154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 12/06/2021] [Indexed: 11/21/2022] Open
Abstract
All brain functionality arises from the activity in neural circuits in different anatomical regions. These regions contain different circuits comprising unique cell types. An integral part to understanding neural circuits is a full census of the constituent parts, i.e., the neural cell types. This census can be based on different characteristics. Previously combinations of morphology and physiology, gene expression, and chromatin accessibility have been used in various cortical and subcortical regions. This has given an extensive yet incomplete overview of neural cell types. However, these techniques have not been applied to all brain regions. Here we apply single cell analysis of accessible chromatin on two similar but different cortical regions, the medial and the lateral entorhinal cortices. Even though these two regions are anatomically similar, their intrinsic and extrinsic connectivity are different. In 4,136 cells we identify 20 different clusters representing different cell types. As expected, excitatory cells show regionally specific clusters, whereas inhibitory neurons are shared between regions. We find that several deep layer excitatory neuronal cell types as defined by chromatin profile are also shared between the two different regions. Integration with a larger scRNA-seq dataset maintains this shared characteristic for cells in Layer Vb. Interestingly, this layer contains three clusters, two specific to either subregion and one shared between the two. These clusters can be putatively associated with particular functional and anatomical cell types found in this layer. This information is a step forwards into elucidating the cell types within the entorhinal circuit and by extension its functional underpinnings.
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Affiliation(s)
- Stefan Blankvoort
- Kavli Institute for Systems Neuroscience and Centre for Neural Computation, NTNU, Trondheim, Norway
- *Correspondence: Stefan Blankvoort
| | - Lene Christin Olsen
- Department of Clinical and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway
- BioCore Bioinformatics Core Facility, NTNU, Trondheim, Norway
- Department of Neurology, St. Olavs Hospital, Trondheim, Norway
| | - Clifford G. Kentros
- Kavli Institute for Systems Neuroscience and Centre for Neural Computation, NTNU, Trondheim, Norway
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8
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Denda M, Nakanishi S. Do epidermal keratinocytes have sensory and information processing systems? Exp Dermatol 2021; 31:459-474. [PMID: 34726302 DOI: 10.1111/exd.14494] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 10/26/2021] [Accepted: 10/30/2021] [Indexed: 01/22/2023]
Abstract
It was long considered that the role of epidermal keratinocytes is solely to construct a water-impermeable protective membrane, the stratum corneum, at the uppermost layer of the skin. However, in the last two decades, it has been found that keratinocytes contain multiple sensory systems that detect environmental changes, including mechanical stimuli, sound, visible radiation, electric fields, magnetic fields, temperature and chemical stimuli, and also a variety of receptor molecules associated with olfactory or taste sensation. Moreover, neurotransmitters and their receptors that play crucial roles in the brain are functionally expressed in keratinocytes. Recent studies have demonstrated that excitation of keratinocytes can induce sensory perception in the brain. Here, we review the sensory and information processing capabilities of keratinocytes. We discuss the possibility that epidermal keratinocytes might represent the earliest stage in the development of the brain during the evolution of vertebrates.
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Affiliation(s)
- Mitsuhiro Denda
- Institute for Advanced Study of Mathematical Sciences, Meiji University, Nakano-ku, Tokyo, 164-8525, Japan
| | - Shinobu Nakanishi
- Shiseido Global Innovation Center, Nishi-ku, Yokohama, 220-0011, Japan
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9
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Ohara S, Blankvoort S, Nair RR, Nigro MJ, Nilssen ES, Kentros C, Witter MP. Local projections of layer Vb-to-Va are more prominent in lateral than in medial entorhinal cortex. eLife 2021; 10:e67262. [PMID: 33769282 PMCID: PMC8051944 DOI: 10.7554/elife.67262] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 03/25/2021] [Indexed: 11/13/2022] Open
Abstract
The entorhinal cortex, in particular neurons in layer V, allegedly mediate transfer of information from the hippocampus to the neocortex, underlying long-term memory. Recently, this circuit has been shown to comprise a hippocampal output recipient layer Vb and a cortical projecting layer Va. With the use of in vitro electrophysiology in transgenic mice specific for layer Vb, we assessed the presence of the thus necessary connection from layer Vb-to-Va in the functionally distinct medial (MEC) and lateral (LEC) subdivisions; MEC, particularly its dorsal part, processes allocentric spatial information, whereas the corresponding part of LEC processes information representing elements of episodes. Using identical experimental approaches, we show that connections from layer Vb-to-Va neurons are stronger in dorsal LEC compared with dorsal MEC, suggesting different operating principles in these two regions. Although further in vivo experiments are needed, our findings imply a potential difference in how LEC and MEC mediate episodic systems consolidation.
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Grants
- endowment Kavli Foundation
- infrastructure grant NORBRAIN,#197467 Norwegian Research Council
- the Centre of Excellence scheme - Centre for Neural Computation,#223262 Norwegian Research Council
- research grant,# 227769 Norwegian Research Council
- KAKENHI,#19K06917 Ministry of Education, Culture, Sports, Science and Technology
- KAKENHI (#19K06917) Ministry of Education, Culture, Sports, Science and Technology
- #197467 Norwegian Research Council
- #223262 Norwegian Research Council
- #227769 Norwegian Research Council
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Affiliation(s)
- Shinya Ohara
- Kavli institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and TechnologyTrondheimNorway
- Laboratory of Systems Neuroscience, Tohoku University Graduate School of Life SciencesTohokuJapan
| | - Stefan Blankvoort
- Kavli institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and TechnologyTrondheimNorway
| | - Rajeevkumar Raveendran Nair
- Kavli institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and TechnologyTrondheimNorway
| | - Maximiliano J Nigro
- Kavli institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and TechnologyTrondheimNorway
| | - Eirik S Nilssen
- Kavli institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and TechnologyTrondheimNorway
| | - Clifford Kentros
- Kavli institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and TechnologyTrondheimNorway
| | - Menno P Witter
- Kavli institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and TechnologyTrondheimNorway
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10
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Cha YH, Ding L, Yuan H. Neuroimaging Markers of Mal de Débarquement Syndrome. Front Neurol 2021; 12:636224. [PMID: 33746890 PMCID: PMC7970001 DOI: 10.3389/fneur.2021.636224] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 01/22/2021] [Indexed: 01/10/2023] Open
Abstract
Mal de débarquement syndrome (MdDS) is a motion-induced disorder of oscillating vertigo that persists after the motion has ceased. The neuroimaging characteristics of the MdDS brain state have been investigated with studies on brain metabolism, structure, functional connectivity, and measurements of synchronicity. Baseline metabolism and resting-state functional connectivity studies indicate that a limbic focus in the left entorhinal cortex and amygdala may be important in the pathology of MdDS, as these structures are hypermetabolic in MdDS and exhibit increased functional connectivity to posterior sensory processing areas and reduced connectivity to the frontal and temporal cortices. Both structures are tunable with periodic stimulation, with neurons in the entorhinal cortex required for spatial navigation, acting as a critical efferent pathway to the hippocampus, and sending and receiving projections from much of the neocortex. Voxel-based morphometry measurements have revealed volume differences between MdDS and healthy controls in hubs of multiple resting-state networks including the default mode, salience, and executive control networks. In particular, volume in the bilateral anterior cingulate cortices decreases and volume in the bilateral inferior frontal gyri/anterior insulas increases with longer duration of illness. Paired with noninvasive neuromodulation interventions, functional neuroimaging with functional magnetic resonance imaging (fMRI), electroencephalography (EEG), and simultaneous fMRI-EEG have shown changes in resting-state functional connectivity that correlate with symptom modulation, particularly in the posterior default mode network. Reduced parieto-occipital connectivity with the entorhinal cortex and reduced long-range fronto-parieto-occipital connectivity correlate with symptom improvement. Though there is a general theme of desynchronization correlating with reduced MdDS symptoms, the prediction of optimal stimulation parameters for noninvasive brain stimulation in individuals with MdDS remains a challenge due to the large parameter space. However, the pairing of functional neuroimaging and noninvasive brain stimulation can serve as a probe into the biological underpinnings of MdDS and iteratively lead to optimal parameter space identification.
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Affiliation(s)
- Yoon Hee Cha
- Department of Neurology, University of Minnesota, Minneapolis, MN, United States
| | - Lei Ding
- Stephenson School of Biomedical Engineering, University of Oklahoma, Norman, OK, United States.,Institute for Biomedical Engineering, Science, and Technology, University of Oklahoma, Norman, OK, United States
| | - Han Yuan
- Stephenson School of Biomedical Engineering, University of Oklahoma, Norman, OK, United States.,Institute for Biomedical Engineering, Science, and Technology, University of Oklahoma, Norman, OK, United States
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Beesley S, Sullenberger T, Ailani R, D'Orio C, Crockett MS, Kumar SS. d-Serine Intervention In The Medial Entorhinal Area Alters TLE-Related Pathology In CA1 Hippocampus Via The Temporoammonic Pathway. Neuroscience 2021; 453:168-186. [PMID: 33197499 PMCID: PMC7796904 DOI: 10.1016/j.neuroscience.2020.10.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 10/20/2020] [Accepted: 10/22/2020] [Indexed: 01/15/2023]
Abstract
Entrainment of the hippocampus by the medial entorhinal area (MEA) in Temporal Lobe Epilepsy (TLE), the most common type of drug-resistant epilepsy in adults, is believed to be mediated primarily through the perforant pathway (PP), which connects stellate cells in layer (L) II of the MEA with granule cells of the dentate gyrus (DG) to drive the hippocampal tri-synaptic circuit. Using immunohistochemistry, high-resolution confocal microscopy and the rat pilocarpine model of TLE, we show here that the lesser known temporoammonic pathway (TAP) plays a significant role in transferring MEA pathology to the CA1 region of the hippocampus independently of the PP. The pathology observed was region-specific and restricted primarily to the CA1c subfield of the hippocampus. As shown previously, daily intracranial infusion of d-serine (100 μm), an antagonist of GluN3-containing triheteromeric N-Methyl d-aspartate receptors (t-NMDARs), into the MEA prevented loss of LIII neurons and epileptogenesis. This intervention in the MEA led to the rescue of hippocampal CA1 neurons that would have otherwise perished in the epileptic animals, and down regulation of the expression of astrocytes and microglia thereby mitigating the effects of neuroinflammation. Interestingly, these changes were not observed to a similar extent in other regions of vulnerability like the hilus, DG or CA3, suggesting that the pathology manifest in CA1 is driven predominantly through the TAP. This work highlights TAP's role in the entrainment of the hippocampus and identifies specific areas for therapeutic intervention in dealing with TLE.
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Affiliation(s)
- Stephen Beesley
- Department of Biomedical Sciences, College of Medicine & Program in Neuroscience, Florida State University, 1115 W. Call Street, Tallahassee, FL 32306-4300, United States
| | - Thomas Sullenberger
- Department of Biomedical Sciences, College of Medicine & Program in Neuroscience, Florida State University, 1115 W. Call Street, Tallahassee, FL 32306-4300, United States
| | - Roshan Ailani
- Department of Biomedical Sciences, College of Medicine & Program in Neuroscience, Florida State University, 1115 W. Call Street, Tallahassee, FL 32306-4300, United States
| | - Cameron D'Orio
- Department of Biomedical Sciences, College of Medicine & Program in Neuroscience, Florida State University, 1115 W. Call Street, Tallahassee, FL 32306-4300, United States
| | - Mathew S Crockett
- Department of Biomedical Sciences, College of Medicine & Program in Neuroscience, Florida State University, 1115 W. Call Street, Tallahassee, FL 32306-4300, United States
| | - Sanjay S Kumar
- Department of Biomedical Sciences, College of Medicine & Program in Neuroscience, Florida State University, 1115 W. Call Street, Tallahassee, FL 32306-4300, United States.
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Kuhn B, Picollo F, Carabelli V, Rispoli G. Advanced real-time recordings of neuronal activity with tailored patch pipettes, diamond multi-electrode arrays and electrochromic voltage-sensitive dyes. Pflugers Arch 2020; 473:15-36. [PMID: 33047171 PMCID: PMC7782438 DOI: 10.1007/s00424-020-02472-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 09/29/2020] [Accepted: 10/02/2020] [Indexed: 12/03/2022]
Abstract
To understand the working principles of the nervous system is key to figure out its electrical activity and how this activity spreads along the neuronal network. It is therefore crucial to develop advanced techniques aimed to record in real time the electrical activity, from compartments of single neurons to populations of neurons, to understand how higher functions emerge from coordinated activity. To record from single neurons, a technique will be presented to fabricate patch pipettes able to seal on any membrane with a single glass type and whose shanks can be widened as desired. This dramatically reduces access resistance during whole-cell recording allowing fast intracellular and, if required, extracellular perfusion. To simultaneously record from many neurons, biocompatible probes will be described employing multi-electrodes made with novel technologies, based on diamond substrates. These probes also allow to synchronously record exocytosis and neuronal excitability and to stimulate neurons. Finally, to achieve even higher spatial resolution, it will be shown how voltage imaging, employing fast voltage-sensitive dyes and two-photon microscopy, is able to sample voltage oscillations in the brain spatially resolved and voltage changes in dendrites of single neurons at millisecond and micrometre resolution in awake animals.
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Affiliation(s)
- Bernd Kuhn
- Optical Neuroimaging Unit, OIST Graduate University, 1919-1 Tancha, Onna-son, Okinawa, Japan
| | - Federico Picollo
- Department of Physics, NIS Interdepartmental Centre, University of Torino and Italian Institute of Nuclear Physics, via Giuria 1, 10125, Torino, Italy
| | - Valentina Carabelli
- Department of Drug and Science Technology, NIS Interdepartmental Centre, University of Torino, Corso Raffaello 30, 10125, Torino, Italy
| | - Giorgio Rispoli
- Department of Biomedical and Specialist Surgical Sciences, University of Ferrara, Via Luigi Borsari 46, 44121, Ferrara, Italy.
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13
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Roome CJ, Kuhn B. Voltage imaging with ANNINE dyes and two-photon microscopy of Purkinje dendrites in awake mice. Neurosci Res 2020; 152:15-24. [DOI: 10.1016/j.neures.2019.11.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 11/07/2019] [Accepted: 11/12/2019] [Indexed: 12/13/2022]
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14
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Li T, Arleo A, Sheynikhovich D. Modeling place cells and grid cells in multi-compartment environments: Entorhinal–hippocampal loop as a multisensory integration circuit. Neural Netw 2020; 121:37-51. [DOI: 10.1016/j.neunet.2019.09.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 07/24/2019] [Accepted: 09/02/2019] [Indexed: 01/11/2023]
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15
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Khan IS, D'Agostino EN, Calnan DR, Lee JE, Aronson JP. Deep Brain Stimulation for Memory Modulation: A New Frontier. World Neurosurg 2019; 126:638-646. [DOI: 10.1016/j.wneu.2018.12.184] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 12/18/2018] [Accepted: 12/20/2018] [Indexed: 12/30/2022]
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16
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Kajiwara R, Tominaga Y, Tominaga T. Network Plasticity Involved in the Spread of Neural Activity Within the Rhinal Cortices as Revealed by Voltage-Sensitive Dye Imaging in Mouse Brain Slices. Front Cell Neurosci 2019; 13:20. [PMID: 30804757 PMCID: PMC6378919 DOI: 10.3389/fncel.2019.00020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2018] [Accepted: 01/16/2019] [Indexed: 11/13/2022] Open
Abstract
The rhinal cortices, such as the perirhinal cortex (PC) and the entorhinal cortex (EC), are located within the bidirectional pathway between the neocortex and the hippocampus. Physiological studies indicate that the perirhinal transmission of neocortical inputs to the EC occurs at an extremely low probability, though many anatomical studies indicated strong connections exist in the pathway. Our previous study in rat brain slices indicated that an increase in excitability in deep layers of the PC/EC border initiated the neural activity transfer from the PC to the EC. In the present study, we hypothesized that such changes in network dynamics are not incidental observations but rather due to the plastic features of the perirhinal network, which links with the EC. To confirm this idea, we analyzed the network properties of neural transmission throughout the rhinal cortices and the plastic behavior of the network by performing a single-photon wide-field optical recording technique with a voltage-sensitive dye (VSD) in mouse brain slices of the PC, the EC, and the hippocampus. The low concentration of 4-aminopyridine (4-AP; 40 μM) enhanced neural activity in the PC, which eventually propagated to the EC via the deep layers of the PC/EC border. Interestingly, washout of 4-AP was unable to reverse entorhinal activation to the previous state. This change in the network property persisted for more than 1 h. This observation was not limited to the application of 4-AP. Burst stimulation to neurons in the perirhinal deep layers also induced the same change of network property. These results indicate the long-lasting modification of physiological connection between the PC and the EC, suggesting the existence of plasticity in the perirhinal-entorhinal network.
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Affiliation(s)
- Riichi Kajiwara
- Department of Electronics and Bioinformatics, School of Science and Technology, Meiji University, Kawasaki, Japan
| | - Yoko Tominaga
- Laboratory for Neural Circuit Systems, Institute of Neuroscience, Tokushima Bunri University, Sanuki, Japan
| | - Takashi Tominaga
- Laboratory for Neural Circuit Systems, Institute of Neuroscience, Tokushima Bunri University, Sanuki, Japan
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17
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Beesley S, Sullenberger T, Pilli J, Abbasi S, Gunjan A, Kumar SS. Colocalization of distinct NMDA receptor subtypes at excitatory synapses in the entorhinal cortex. J Neurophysiol 2018; 121:238-254. [PMID: 30461362 DOI: 10.1152/jn.00468.2018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The subunit composition of N-methyl-d-aspartate receptors (NMDARs) at synaptic inputs onto a neuron can either vary or be uniform depending on the type of neuron and/or brain region. Excitatory pyramidal neurons in the frontal and somatosensory cortices (L5), for example, show pathway-specific differences in NMDAR subunit composition in contrast with the entorhinal cortex (L3), where we now show colocalization of NMDARs with distinct subunit compositions at individual synaptic inputs onto these neurons. Subunit composition was deduced electrophysiologically based on alterations of current-voltage relationship ( I-V) profiles, amplitudes, and decay kinetics of minimally evoked, pharmacologically isolated, NMDAR-mediated excitatory postsynaptic currents by known subunit-preferring antagonists. The I-Vs were outwardly rectifying in a majority of neurons assayed (~80%), indicating expression of GluN1/GluN2/GluN3-containing triheteromeric NMDARs ( t-NMDARs) and of the conventional type, reversing close to 0 mV with prominent regions of negative slope, in the rest of the neurons sampled (~20%), indicating expression of GluN1/GluN2-containing diheteromeric NMDARs ( d-NMDARs). Blocking t-NMDARs in neurons with outwardly rectifying I-Vs pharmacologically unmasked d-NMDARs, with all responses antagonized using D-AP5. Coimmunoprecipitation assays of membrane-bound protein complexes isolated from the medial entorhinal area using subunit-selective antibodies corroborated stoichiometry and together suggested the coexpression of t- and d-NMDARs at these synapses. Colocalization of functionally distinct NMDAR subtypes at individual synaptic inputs likely enhances the repertoire of pyramidal neurons for information processing and plasticity within the entorhinal cortex. NEW & NOTEWORTHY The subunit composition of a N-methyl-d-aspartate (NMDA) receptor, which dictates most aspects of its function, can vary between neurons in different brain regions and/or between synaptic inputs onto single neurons. Here we demonstrate colocalization of tri- and diheteromeric-NMDA receptors at the same/single synaptic input onto excitatory neurons in the entorhinal cortex. Synaptic colocalization of distinct NMDAR subtypes might endow entorhinal cortical neurons with the ability to encode distinct patterns of neuronal activity through single synapses.
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Affiliation(s)
- Stephen Beesley
- Department of Biomedical Sciences, College of Medicine and Program in Neuroscience, Florida State University , Tallahassee, Florida
| | - Thomas Sullenberger
- Department of Biomedical Sciences, College of Medicine and Program in Neuroscience, Florida State University , Tallahassee, Florida
| | - Jyotsna Pilli
- Department of Biomedical Sciences, College of Medicine and Program in Neuroscience, Florida State University , Tallahassee, Florida
| | - Saad Abbasi
- Department of Biomedical Sciences, College of Medicine and Program in Neuroscience, Florida State University , Tallahassee, Florida
| | - Akash Gunjan
- Department of Biomedical Sciences, College of Medicine and Program in Neuroscience, Florida State University , Tallahassee, Florida
| | - Sanjay S Kumar
- Department of Biomedical Sciences, College of Medicine and Program in Neuroscience, Florida State University , Tallahassee, Florida
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18
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Ohara S, Onodera M, Simonsen ØW, Yoshino R, Hioki H, Iijima T, Tsutsui KI, Witter MP. Intrinsic Projections of Layer Vb Neurons to Layers Va, III, and II in the Lateral and Medial Entorhinal Cortex of the Rat. Cell Rep 2018; 24:107-116. [DOI: 10.1016/j.celrep.2018.06.014] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 05/04/2018] [Accepted: 06/01/2018] [Indexed: 12/29/2022] Open
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19
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D’Albis T, Kempter R. A single-cell spiking model for the origin of grid-cell patterns. PLoS Comput Biol 2017; 13:e1005782. [PMID: 28968386 PMCID: PMC5638623 DOI: 10.1371/journal.pcbi.1005782] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 10/12/2017] [Accepted: 09/18/2017] [Indexed: 11/19/2022] Open
Abstract
Spatial cognition in mammals is thought to rely on the activity of grid cells in the entorhinal cortex, yet the fundamental principles underlying the origin of grid-cell firing are still debated. Grid-like patterns could emerge via Hebbian learning and neuronal adaptation, but current computational models remained too abstract to allow direct confrontation with experimental data. Here, we propose a single-cell spiking model that generates grid firing fields via spike-rate adaptation and spike-timing dependent plasticity. Through rigorous mathematical analysis applicable in the linear limit, we quantitatively predict the requirements for grid-pattern formation, and we establish a direct link to classical pattern-forming systems of the Turing type. Our study lays the groundwork for biophysically-realistic models of grid-cell activity.
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Affiliation(s)
- Tiziano D’Albis
- Institute for Theoretical Biology, Department of Biology, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Richard Kempter
- Institute for Theoretical Biology, Department of Biology, Humboldt-Universität zu Berlin, Berlin, Germany
- Bernstein Center for Computational Neuroscience Berlin, Berlin, Germany
- Einstein Center for Neurosciences Berlin, Berlin, Germany
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20
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Nixima K, Okanoya K, Ichinohe N, Kurotani T. Fast voltage-sensitive dye imaging of excitatory and inhibitory synaptic transmission in the rat granular retrosplenial cortex. J Neurophysiol 2017; 118:1784-1799. [PMID: 28701546 DOI: 10.1152/jn.00734.2016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 07/05/2017] [Accepted: 07/05/2017] [Indexed: 11/22/2022] Open
Abstract
Rodent granular retrosplenial cortex (GRS) has dense connections between the anterior thalamic nuclei (ATN) and hippocampal formation. GRS superficial pyramidal neurons exhibit distinctive late spiking (LS) firing property and form patchy clusters with prominent apical dendritic bundles. The aim of this study was to investigate spatiotemporal dynamics of signal transduction in the GRS induced by ATN afferent stimulation by using fast voltage-sensitive dye imaging in rat brain slices. In coronal slices, layer 1a stimulation, which presumably activated thalamic fibers, evoked propagation of excitatory synaptic signals from layers 2-4 to layers 5-6 in a direction perpendicular to the layer axis, followed by transverse signal propagation within each layer. In the presence of ionotropic glutamate receptor antagonists, inhibitory responses were observed in superficial layers, induced by direct activation of inhibitory interneurons in layer 1. In horizontal slices, excitatory signals in deep layers propagated transversely mainly from posterior to anterior via superficial layers. Cortical inhibitory responses upon layer 1a stimulation in horizontal slices were weaker than those in the coronal slices. Observed differences between coronal and horizontal planes suggest anisotropy of the intracortical circuitry. In conclusion, ATN inputs are processed differently in coronal and horizontal planes of the GRS and then conveyed to other cortical areas. In both planes, GRS superficial layers play an important role in signal propagation, which suggests that superficial neuronal cascade is crucial in the integration of multiple information sources.NEW & NOTEWORTHY Superficial neurons in the rat granular retrosplenial cortex (GRS) show distinctive late-spiking (LS) firing property. However, little is known about spatiotemporal dynamics of signal transduction in the GRS. We demonstrated LS neuron network relaying thalamic inputs to deep layers and anisotropic distribution of inhibition between coronal and horizontal planes. Since deep layers of the GRS receive inputs from the subiculum, GRS circuits may work as an integrator of multiple sources such as sensory and memory information.
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Affiliation(s)
- Ken'ichi Nixima
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro, Tokyo, Japan.,ERATO Okanoya Emotional Information Project, Japan Science and Technology Agency, Hirosawa, Wako, Saitama, Japan.,Emotional Information Joint Research Laboratory, RIKEN Brain Science Institute, Hirosawa, Wako, Saitama, Japan; and
| | - Kazuo Okanoya
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro, Tokyo, Japan.,ERATO Okanoya Emotional Information Project, Japan Science and Technology Agency, Hirosawa, Wako, Saitama, Japan.,Emotional Information Joint Research Laboratory, RIKEN Brain Science Institute, Hirosawa, Wako, Saitama, Japan; and
| | - Noritaka Ichinohe
- Molecular Analysis of Higher Brain Function (Ichinohe group), RIKEN Brain Science Institute, Hirosawa, Wako, Saitama, Japan
| | - Tohru Kurotani
- ERATO Okanoya Emotional Information Project, Japan Science and Technology Agency, Hirosawa, Wako, Saitama, Japan; .,Emotional Information Joint Research Laboratory, RIKEN Brain Science Institute, Hirosawa, Wako, Saitama, Japan; and.,Molecular Analysis of Higher Brain Function (Ichinohe group), RIKEN Brain Science Institute, Hirosawa, Wako, Saitama, Japan
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21
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Chen T, Tanaka M, Wang Y, Sha S, Furuya K, Chen L, Sokabe M. Neurosteroid dehydroepiandrosterone enhances activity and trafficking of astrocytic GLT-1 via σ 1 receptor-mediated PKC activation in the hippocampal dentate gyrus of rats. Glia 2017; 65:1491-1503. [PMID: 28581152 DOI: 10.1002/glia.23175] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 05/14/2017] [Accepted: 05/15/2017] [Indexed: 11/08/2022]
Abstract
Neurosteroid dehydroepiandrosterone (DHEA) has been reported to exert a potent neuroprotective effect against glutamate-induced excitotoxicity. However, the underlying mechanism remains to be elucidated. One of the possible mechanisms may be an involvement of astrocytic glutamate transporter subtype-1 (GLT-1) that can quickly clear spilled glutamate at the synapse to prevent excitotoxicity. To examine the effect of DHEA on GLT-1 activity, we measured synaptically induced glial depolarization (SIGD) in the dentate gyrus (DG) of adult rats by applying an optical recording technique to the hippocampal slices stained with voltage-sensitive dye RH155. Bath-application of DHEA for 10 min dose-dependently increased SIGD without changing presynaptic glutamate releases, which was sensitive to the GLT-1 blocker DHK. Patch-clamp recordings in astrocytes showed that an application of 50 μM DHEA increased glutamate-evoked inward currents (Iglu) by approximately 1.5-fold, which was dependent on the GLT-1 activity. In addition, the level of biotinylated GLT-1 protein in the surface of astrocytes was significantly elevated by DHEA. The DHEA-increased SIGD, Iglu, and GLT-1 translocation to the cell surface were blocked by the σ1 R antagonist NE100 and mimicked by the σ1 R agonist PRE084. DHEA elevated the phosphorylation level of PKC in a σ1 R-dependent manner. Furthermore, the PKC inhibitor chelerythrine could prevent the DHEA-increased SIGD, Iglu, and GLT-1 translocation. Collectively, present results suggest that DHEA enhances the activity and translocation to cell surface of astrocytic GLT-1 mainly via σ1 R-mediated PKC cascade.
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Affiliation(s)
- Tingting Chen
- Department of Physiology, Laboratory of Reproductive Medicine, Nanjing Medical University, Tianyuan East Road 818, Nanjing, China
| | - Motoki Tanaka
- Mechanobiology Laboratory, Nagoya University Graduate School of Medicine, 65 Tsurumai, Nagoya, 466-8550, Japan
| | - Ya Wang
- Department of Physiology, Laboratory of Reproductive Medicine, Nanjing Medical University, Tianyuan East Road 818, Nanjing, China
| | - Sha Sha
- Department of Physiology, Laboratory of Reproductive Medicine, Nanjing Medical University, Tianyuan East Road 818, Nanjing, China
| | - Kishio Furuya
- ICORP/SORST Cell Mechanosensing, JST, 65 Tsurumai, Nagoya, 466-8550, Japan
| | - Ling Chen
- Department of Physiology, Laboratory of Reproductive Medicine, Nanjing Medical University, Tianyuan East Road 818, Nanjing, China.,Mechanobiology Laboratory, Nagoya University Graduate School of Medicine, 65 Tsurumai, Nagoya, 466-8550, Japan
| | - Masahiro Sokabe
- Mechanobiology Laboratory, Nagoya University Graduate School of Medicine, 65 Tsurumai, Nagoya, 466-8550, Japan.,ICORP/SORST Cell Mechanosensing, JST, 65 Tsurumai, Nagoya, 466-8550, Japan
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22
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Willems JGP, Wadman WJ, Cappaert NLM. Distinct Spatiotemporal Activation Patterns of the Perirhinal-Entorhinal Network in Response to Cortical and Amygdala Input. Front Neural Circuits 2016; 10:44. [PMID: 27378860 PMCID: PMC4906015 DOI: 10.3389/fncir.2016.00044] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 05/30/2016] [Indexed: 11/14/2022] Open
Abstract
The perirhinal (PER) and entorhinal cortex (EC) receive input from the agranular insular cortex (AiP) and the subcortical lateral amygdala (LA) and the main output area is the hippocampus. Information transfer through the PER/EC network however, is not always guaranteed. It is hypothesized that this network actively regulates the (sub)cortical activity transfer to the hippocampal network and that the inhibitory system is involved in this function. This study determined the recruitment by the AiP and LA afferents in PER/EC network with the use of voltage sensitive dye (VSD) imaging in horizontal mouse brain slices. Electrical stimulation (500 μA) of the AiP induced activity that gradually propagated predominantly in the rostro-caudal direction: from the PER to the lateral EC (LEC). In the presence of 1 μM of the competitive γ-aminobutyric acid (GABAA) receptor antagonist bicuculline, AiP stimulation recruited the medial EC (MEC) as well. In contrast, LA stimulation (500 μA) only induced activity in the deep layers of the PER. In the presence of bicuculline, the initial population activity in the PER propagated further towards the superficial layers and the EC after a delay. The latency of evoked responses decreased with increasing stimulus intensities (50–500 μA) for both the AiP and LA stimuli. The stimulation threshold for evoking responses in the PER/EC network was higher for the LA than for the AiP. This study showed that the extent of the PER/EC network activation depends on release of inhibition. When GABAA dependent inhibition is reduced, both the AiP and the LA activate spatially overlapping regions, although in a distinct spatiotemporal fashion. It is therefore hypothesized that the inhibitory network regulates excitatory activity from both cortical and subcortical areas that has to be transmitted through the PER/EC network.
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Affiliation(s)
- Janske G P Willems
- Center for NeuroScience, Swammerdam Institute for Life Sciences, University of Amsterdam Amsterdam, Netherlands
| | - Wytse J Wadman
- Center for NeuroScience, Swammerdam Institute for Life Sciences, University of Amsterdam Amsterdam, Netherlands
| | - Natalie L M Cappaert
- Center for NeuroScience, Swammerdam Institute for Life Sciences, University of Amsterdam Amsterdam, Netherlands
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23
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Dengler CG, Coulter DA. Normal and epilepsy-associated pathologic function of the dentate gyrus. PROGRESS IN BRAIN RESEARCH 2016; 226:155-78. [PMID: 27323942 DOI: 10.1016/bs.pbr.2016.04.005] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The dentate gyrus plays critical roles both in cognitive processing, and in regulation of the induction and propagation of pathological activity. The cellular and circuit mechanisms underlying these diverse functions overlap extensively. At the cellular level, the intrinsic properties of dentate granule cells combine to endow these neurons with a fundamental reluctance to activate, one of their hallmark traits. At the circuit level, the dentate gyrus constitutes one of the more heavily inhibited regions of the brain, with strong, fast feedforward and feedback GABAergic inhibition dominating responses to afferent activation. In pathologic states such as epilepsy, a number of alterations within the dentate gyrus combine to compromise the regulatory properties of this circuit, culminating in a collapse of its normal function. This epilepsy-associated transformation in the fundamental properties of this critical regulatory hippocampal circuit may contribute both to seizure propensity, and cognitive and emotional comorbidities characteristic of this disease state.
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Affiliation(s)
- C G Dengler
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - D A Coulter
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States; The Research Institute of the Children's Hospital of Philadelphia, Philadelphia, PA, United States.
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24
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McKenzie S, Keene CS, Farovik A, Bladon J, Place R, Komorowski R, Eichenbaum H. Representation of memories in the cortical-hippocampal system: Results from the application of population similarity analyses. Neurobiol Learn Mem 2015; 134 Pt A:178-191. [PMID: 26748022 DOI: 10.1016/j.nlm.2015.12.008] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2015] [Revised: 12/08/2015] [Accepted: 12/24/2015] [Indexed: 01/07/2023]
Abstract
Here we consider the value of neural population analysis as an approach to understanding how information is represented in the hippocampus and cortical areas and how these areas might interact as a brain system to support memory. We argue that models based on sparse coding of different individual features by single neurons in these areas (e.g., place cells, grid cells) are inadequate to capture the complexity of experience represented within this system. By contrast, population analyses of neurons with denser coding and mixed selectivity reveal new and important insights into the organization of memories. Furthermore, comparisons of the organization of information in interconnected areas suggest a model of hippocampal-cortical interactions that mediates the fundamental features of memory.
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Affiliation(s)
- Sam McKenzie
- The Neuroscience Institute, NYU Langone Medical Center, United States
| | | | - Anja Farovik
- Center for Memory and Brain, Boston University, United States
| | - John Bladon
- Center for Memory and Brain, Boston University, United States
| | - Ryan Place
- Center for Memory and Brain, Boston University, United States
| | - Robert Komorowski
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, United States
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25
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Velíšková J, Iacobas D, Iacobas S, Sidyelyeva G, Chachua T, Velíšek L. Oestradiol Regulates Neuropeptide Y Release and Gene Coupling with the GABAergic and Glutamatergic Synapses in the Adult Female Rat Dentate Gyrus. J Neuroendocrinol 2015; 27:911-20. [PMID: 26541912 DOI: 10.1111/jne.12332] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 09/03/2015] [Accepted: 10/27/2015] [Indexed: 12/13/2022]
Abstract
Neuropeptide Y (NPY) is an endogenous modulator of neuronal activity affecting both GABAergic and glutamatergic transmission. Previously, we found that oestradiol modifies the number of NPY immunoreactive neurones in the hippocampal dentate gyrus. In the present study, we investigated which oestrogen receptor type is responsible for these changes in the number of NPY-positive neurones. Furthermore, we determined the effects of oestrogen receptor activation on NPY release. Finally, we examined the contribution of oestrogen toward the remodelling of the GABAergic and glutamatergic gene networks in terms of coupling with Npy gene expression in ovariectomised rats. We found that activation of either oestrogen receptor type (ERα or ERβ) increases the number of NPY-immunopositive neurones and enhances NPY release in the dentate gyrus. We also found that, compared to oestrogen-lacking ovariectomised rats, oestrogen replacement increases the probability of synergistic/antagonistic coupling between the Npy and GABAergic synapse genes, whereas the glutamatergic synapse genes are less likely to be coupled with Npy under similar conditions. The data together suggest that oestrogens play a critical role in the regulation of NPY system activity and are also involved in the coupling/uncoupling of the Npy gene with the GABAergic and glutamatergic synapses in the female rat dentate gyrus.
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Affiliation(s)
- J Velíšková
- Department of Cell Biology & Anatomy, New York Medical College, Valhalla, NY, USA
- Department of Obstetrics & Gynecology, New York Medical College, Valhalla, NY, USA
- Department of Neurology, New York Medical College, Valhalla, NY, USA
| | - D Iacobas
- Department of Pathology, New York Medical College, Valhalla, NY, USA
- DP Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, USA
| | - S Iacobas
- Department of Pathology, New York Medical College, Valhalla, NY, USA
| | - G Sidyelyeva
- Department of Cell Biology & Anatomy, New York Medical College, Valhalla, NY, USA
| | - T Chachua
- Department of Cell Biology & Anatomy, New York Medical College, Valhalla, NY, USA
| | - L Velíšek
- Department of Cell Biology & Anatomy, New York Medical College, Valhalla, NY, USA
- Department of Neurology, New York Medical College, Valhalla, NY, USA
- Department of Pediatrics, New York Medical College, Valhalla, NY, USA
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26
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Stepan J, Hladky F, Uribe A, Holsboer F, Schmidt MV, Eder M. High-Speed imaging reveals opposing effects of chronic stress and antidepressants on neuronal activity propagation through the hippocampal trisynaptic circuit. Front Neural Circuits 2015; 9:70. [PMID: 26594153 PMCID: PMC4635222 DOI: 10.3389/fncir.2015.00070] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2015] [Accepted: 10/22/2015] [Indexed: 12/11/2022] Open
Abstract
Antidepressants (ADs) are used as first-line treatment for most stress-related psychiatric disorders. The alterations in brain circuit dynamics that can arise from stress exposure and underlie therapeutic actions of ADs remain, however, poorly understood. Here, enabled by a recently developed voltage-sensitive dye imaging (VSDI) assay in mouse brain slices, we examined the impact of chronic stress and concentration-dependent effects of eight clinically used ADs (belonging to different chemical/functional classes) on evoked neuronal activity propagations through the hippocampal trisynaptic circuitry (HTC: perforant path → dentate gyrus (DG) → area CA3 → area CA1). Exposure of mice to chronic social defeat stress led to markedly weakened activity propagations (“HTC-Waves”). In contrast, at concentrations in the low micromolar range, all ADs, which were bath applied to slices, caused an amplification of HTC-Waves in CA regions (invariably in area CA1). The fast-acting “antidepressant” ketamine, the mood stabilizer lithium, and brain-derived neurotrophic factor (BDNF) exerted comparable enhancing effects, whereas the antipsychotic haloperidol and the anxiolytic diazepam attenuated HTC-Waves. Collectively, we provide direct experimental evidence that chronic stress can depress neuronal signal flow through the HTC and demonstrate shared opposing effects of ADs. Thus, our study points to a circuit-level mechanism of ADs to counteract stress-induced impairment of hippocampal network function. However, the observed effects of ADs are impossible to depend on enhanced neurogenesis.
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Affiliation(s)
- Jens Stepan
- Max Planck Institute of Psychiatry Munich, Germany ; Department Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry Munich, Germany ; Scientific Core Unit "Electrophysiology and Neuronal Network Dynamics", Max Planck Institute of Psychiatry Munich, Germany ; Clinical Department, Max Planck Institute of Psychiatry Munich, Germany
| | - Florian Hladky
- Max Planck Institute of Psychiatry Munich, Germany ; Department Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry Munich, Germany ; Scientific Core Unit "Electrophysiology and Neuronal Network Dynamics", Max Planck Institute of Psychiatry Munich, Germany
| | - Andrés Uribe
- Max Planck Institute of Psychiatry Munich, Germany ; Department Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry Munich, Germany ; Research Group "Stress Resilience", Max Planck Institute of Psychiatry Munich, Germany
| | - Florian Holsboer
- Max Planck Institute of Psychiatry Munich, Germany ; HMNC GmbH Munich, Germany
| | - Mathias V Schmidt
- Max Planck Institute of Psychiatry Munich, Germany ; Department Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry Munich, Germany ; Research Group "Stress Resilience", Max Planck Institute of Psychiatry Munich, Germany
| | - Matthias Eder
- Max Planck Institute of Psychiatry Munich, Germany ; Department Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry Munich, Germany ; Scientific Core Unit "Electrophysiology and Neuronal Network Dynamics", Max Planck Institute of Psychiatry Munich, Germany
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27
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Sandler RA, Song D, Hampson RE, Deadwyler SA, Berger TW, Marmarelis VZ. Hippocampal closed-loop modeling and implications for seizure stimulation design. J Neural Eng 2015; 12:056017. [PMID: 26355815 DOI: 10.1088/1741-2560/12/5/056017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
OBJECTIVE Traditional hippocampal modeling has focused on the series of feedforward synapses known as the trisynaptic pathway. However, feedback connections from CA1 back to the hippocampus through the entorhinal cortex (EC) actually make the hippocampus a closed-loop system. By constructing a functional closed-loop model of the hippocampus, one may learn how both physiological and epileptic oscillations emerge and design efficient neurostimulation patterns to abate such oscillations. APPROACH Point process input-output models where estimated from recorded rodent hippocampal data to describe the nonlinear dynamical transformation from CA3 → CA1, via the schaffer-collateral synapse, and CA1 → CA3 via the EC. Each Volterra-like subsystem was composed of linear dynamics (principal dynamic modes) followed by static nonlinearities. The two subsystems were then wired together to produce the full closed-loop model of the hippocampus. MAIN RESULTS Closed-loop connectivity was found to be necessary for the emergence of theta resonances as seen in recorded data, thus validating the model. The model was then used to identify frequency parameters for the design of neurostimulation patterns to abate seizures. SIGNIFICANCE Deep-brain stimulation (DBS) is a new and promising therapy for intractable seizures. Currently, there is no efficient way to determine optimal frequency parameters for DBS, or even whether periodic or broadband stimuli are optimal. Data-based computational models have the potential to be used as a testbed for designing optimal DBS patterns for individual patients. However, in order for these models to be successful they must incorporate the complex closed-loop structure of the seizure focus. This study serves as a proof-of-concept of using such models to design efficient personalized DBS patterns for epilepsy.
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Affiliation(s)
- Roman A Sandler
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA
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Tocker G, Barak O, Derdikman D. Grid cells correlation structure suggests organized feedforward projections into superficial layers of the medial entorhinal cortex. Hippocampus 2015; 25:1599-613. [DOI: 10.1002/hipo.22481] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/17/2015] [Indexed: 01/29/2023]
Affiliation(s)
- Gilad Tocker
- Neuroscience Dept., The Rappaport Faculty of Medicine, Technion - Israel Institute of Technology; Bat Galim Haifa 31096 Israel
- Gonda Multidisciplinary Brain Research Center; Bar Ilan University; Ramat-Gan 52900 Israel
- Rappaport Research Institute; Bat Galim; Haifa 31096 Israel
| | - Omri Barak
- Neuroscience Dept., The Rappaport Faculty of Medicine, Technion - Israel Institute of Technology; Bat Galim Haifa 31096 Israel
| | - Dori Derdikman
- Neuroscience Dept., The Rappaport Faculty of Medicine, Technion - Israel Institute of Technology; Bat Galim Haifa 31096 Israel
- Rappaport Research Institute; Bat Galim; Haifa 31096 Israel
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Stepan J, Dine J, Eder M. Functional optical probing of the hippocampal trisynaptic circuit in vitro: network dynamics, filter properties, and polysynaptic induction of CA1 LTP. Front Neurosci 2015; 9:160. [PMID: 25999809 PMCID: PMC4422028 DOI: 10.3389/fnins.2015.00160] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 04/19/2015] [Indexed: 12/21/2022] Open
Abstract
Decades of brain research have identified various parallel loops linking the hippocampus with neocortical areas, enabling the acquisition of spatial and episodic memories. Especially the hippocampal trisynaptic circuit [entorhinal cortex layer II → dentate gyrus (DG) → cornu ammonis (CA)-3 → CA1] was studied in great detail because of its seemingly simple connectivity and characteristic structures that are experimentally well accessible. While numerous researchers focused on functional aspects, obtained from a limited number of cells in distinct hippocampal subregions, little is known about the neuronal network dynamics which drive information across multiple synapses for subsequent long-term storage. Fast voltage-sensitive dye imaging in vitro allows real-time recording of activity patterns in large/meso-scale neuronal networks with high spatial resolution. In this way, we recently found that entorhinal theta-frequency input to the DG most effectively passes filter mechanisms of the trisynaptic circuit network, generating activity waves which propagate across the entire DG-CA axis. These "trisynaptic circuit waves" involve high-frequency firing of CA3 pyramidal neurons, leading to a rapid induction of classical NMDA receptor-dependent long-term potentiation (LTP) at CA3-CA1 synapses (CA1 LTP). CA1 LTP has been substantially evidenced to be essential for some forms of explicit learning in mammals. Here, we review data with particular reference to whole network-level approaches, illustrating how activity propagation can take place within the trisynaptic circuit to drive formation of CA1 LTP.
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Affiliation(s)
- Jens Stepan
- Department Stress Neurobiology and Neurogenetics, Max Planck Institute of PsychiatryMunich, Germany
| | | | - Matthias Eder
- Department Stress Neurobiology and Neurogenetics, Max Planck Institute of PsychiatryMunich, Germany
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Dynamin-related protein 1 is required for normal mitochondrial bioenergetic and synaptic function in CA1 hippocampal neurons. Cell Death Dis 2015; 6:e1725. [PMID: 25880092 PMCID: PMC4650558 DOI: 10.1038/cddis.2015.94] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Revised: 02/15/2015] [Accepted: 03/02/2015] [Indexed: 12/11/2022]
Abstract
Disrupting particular mitochondrial fission and fusion proteins leads to the death of specific neuronal populations; however, the normal functions of mitochondrial fission in neurons are poorly understood, especially in vivo, which limits the understanding of mitochondrial changes in disease. Altered activity of the central mitochondrial fission protein dynamin-related protein 1 (Drp1) may contribute to the pathophysiology of several neurologic diseases. To study Drp1 in a neuronal population affected by Alzheimer's disease (AD), stroke, and seizure disorders, we postnatally deleted Drp1 from CA1 and other forebrain neurons in mice (CamKII-Cre, Drp1lox/lox (Drp1cKO)). Although most CA1 neurons survived for more than 1 year, their synaptic transmission was impaired, and Drp1cKO mice had impaired memory. In Drp1cKO cell bodies, we observed marked mitochondrial swelling but no change in the number of mitochondria in individual synaptic terminals. Using ATP FRET sensors, we found that cultured neurons lacking Drp1 (Drp1KO) could not maintain normal levels of mitochondrial-derived ATP when energy consumption was increased by neural activity. These deficits occurred specifically at the nerve terminal, but not the cell body, and were sufficient to impair synaptic vesicle cycling. Although Drp1KO increased the distance between axonal mitochondria, mitochondrial-derived ATP still decreased similarly in Drp1KO boutons with and without mitochondria. This indicates that mitochondrial-derived ATP is rapidly dispersed in Drp1KO axons, and that the deficits in axonal bioenergetics and function are not caused by regional energy gradients. Instead, loss of Drp1 compromises the intrinsic bioenergetic function of axonal mitochondria, thus revealing a mechanism by which disrupting mitochondrial dynamics can cause dysfunction of axons.
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Fujieda T, Koganezawa N, Ide Y, Shirao T, Sekino Y. An inhibitory pathway controlling the gating mechanism of the mouse lateral amygdala revealed by voltage-sensitive dye imaging. Neurosci Lett 2015; 590:126-31. [DOI: 10.1016/j.neulet.2015.01.079] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Revised: 01/28/2015] [Accepted: 01/29/2015] [Indexed: 01/11/2023]
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Reichel JM, Nissel S, Rogel-Salazar G, Mederer A, Käfer K, Bedenk BT, Martens H, Anders R, Grosche J, Michalski D, Härtig W, Wotjak CT. Distinct behavioral consequences of short-term and prolonged GABAergic depletion in prefrontal cortex and dorsal hippocampus. Front Behav Neurosci 2015; 8:452. [PMID: 25628548 PMCID: PMC4292780 DOI: 10.3389/fnbeh.2014.00452] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 12/17/2014] [Indexed: 11/13/2022] Open
Abstract
GABAergic interneurons are essential for a functional equilibrium between excitatory and inhibitory impulses throughout the CNS. Disruption of this equilibrium can lead to various neurological or neuropsychiatric disorders such as epilepsy or schizophrenia. Schizophrenia itself is clinically defined by negative (e.g., depression) and positive (e.g., hallucinations) symptoms as well as cognitive dysfunction. GABAergic interneurons are proposed to play a central role in the etiology and progression of schizophrenia; however, the specific mechanisms and the time-line of symptom development as well as the distinct involvement of cortical and hippocampal GABAergic interneurons in the etiology of schizophrenia-related symptoms are still not conclusively resolved. Previous work demonstrated that GABAergic interneurons can be selectively depleted in adult mice by means of saporin-conjugated anti-vesicular GABA transporter antibodies (SAVAs) in vitro and in vivo. Given their involvement in schizophrenia-related disease etiology, we ablated GABAergic interneurons in the medial prefrontal cortex (mPFC) and dorsal hippocampus (dHPC) in adult male C57BL/6N mice. Subsequently we assessed alterations in anxiety, sensory processing, hyperactivity and cognition after long-term (>14 days) and short-term (<14 days) GABAergic depletion. Long-term GABAergic depletion in the mPFC resulted in a decrease in sensorimotor-gating and impairments in cognitive flexibility. Notably, the same treatment at the level of the dHPC completely abolished spatial learning capabilities. Short-term GABAergic depletion in the dHPC revealed a transient hyperactive phenotype as well as marked impairments regarding the acquisition of a spatial memory. In contrast, recall of a spatial memory was not affected by the same intervention. These findings emphasize the importance of functional local GABAergic networks for the encoding but not the recall of hippocampus-dependent spatial memories.
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Affiliation(s)
- Judith M Reichel
- Department of Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry, Research Group "Neuronal Plasticity" Munich, Germany
| | - Sabine Nissel
- Paul Flechsig Institute for Brain Research, University of Leipzig Leipzig, Germany
| | - Gabriela Rogel-Salazar
- Department of Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry, Research Group "Neuronal Plasticity" Munich, Germany
| | - Anna Mederer
- Department of Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry, Research Group "Neuronal Plasticity" Munich, Germany
| | - Karola Käfer
- Department of Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry, Research Group "Neuronal Plasticity" Munich, Germany
| | - Benedikt T Bedenk
- Department of Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry, Research Group "Neuronal Plasticity" Munich, Germany
| | | | - Rebecca Anders
- Paul Flechsig Institute for Brain Research, University of Leipzig Leipzig, Germany
| | - Jens Grosche
- Paul Flechsig Institute for Brain Research, University of Leipzig Leipzig, Germany ; Effigos AG Leipzig, Germany
| | | | - Wolfgang Härtig
- Paul Flechsig Institute for Brain Research, University of Leipzig Leipzig, Germany
| | - Carsten T Wotjak
- Department of Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry, Research Group "Neuronal Plasticity" Munich, Germany
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Voltage-sensitive dye imaging of primary motor cortex activity produced by ventral tegmental area stimulation. J Neurosci 2014; 34:8894-903. [PMID: 24966388 DOI: 10.1523/jneurosci.5286-13.2014] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The primary motor cortex (M1) receives dopaminergic projections from the ventral tegmental area (VTA) through the mesocortical dopamine pathway. However, few studies have focused on changes in M1 neuronal activity caused by VTA activation. To address this issue, we used voltage-sensitive dye imaging (VSD) to reveal the spatiotemporal dynamics of M1 activity induced by single-pulse stimulation of VTA in anesthetized rats. VSD imaging showed that brief electrical stimulation of unilateral VTA elicited a short-latency excitatory-inhibitory sequence of neuronal activity not only in the ipsilateral but also in the contralateral M1. The contralateral M1 response was not affected by pharmacological blockade of ipsilateral M1 activity, but it was completely abolished by corpus callosum transection. Although the VTA-evoked neuronal activity extended throughout the entire M1, we found the most prominent activity in the forelimb area of M1. The 6-OHDA-lesioned VTA failed to evoke M1 activity. Furthermore, both excitatory and inhibitory intact VTA-induced activity was entirely extinguished by blocking glutamate receptors in the target M1. When intracortical microstimulation of M1 was paired with VTA stimulation, the evoked forelimb muscle activity was facilitated or inhibited, depending on the interval between the two stimuli. These findings suggest that VTA neurons directly modulate the excitability of M1 neurons via fast glutamate signaling and, consequently, may control the last cortical stage of motor command processing.
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l-DOPA reverses the impairment of Dentate Gyrus LTD in experimental parkinsonism via β-adrenergic receptors. Exp Neurol 2014; 261:377-85. [PMID: 25058044 DOI: 10.1016/j.expneurol.2014.07.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 05/30/2014] [Accepted: 07/08/2014] [Indexed: 11/20/2022]
Abstract
Parkinson's disease (PD) patients exhibit motor and non-motor symptoms that severely affect quality of life. Cognitive alterations in PD subjects have been related to both structural and functional hippocampal changes. Here we investigated the effects of the 6-hydroxydopamine (6-OHDA) lesion in the Medial Forebrain Bundle (MFB) on the hippocampus focusing on the Dentate Gyrus (DG). In vivo microdialysis measurements revealed that the 6-OHDA injection disrupts both dopaminergic and noradrenergic transmission in rat DG. In vitro electrophysiological recordings showed that these neurochemical alterations were accompanied by impairment of long-term depression (LTD) at medial perforant path/DG synapses. Furthermore, this alteration was reversed by l-DOPA treatment. Notably, the therapeutic effect of l-DOPA on LTD was blocked by the antagonism of β-noradrenergic receptors, but not by dopamine D1 or D2 receptor antagonists. Thus, while the dopaminergic transmission does not seem to be implicated in this therapeutic effect of l-DOPA, the noradrenergic system plays a central role in the synaptic dysfunction of the DG in experimental PD. Our work provides new evidence on the role of catecholamines in DG synaptic plasticity and sheds light on the possible synaptic mechanisms underlying cognitive deficits in PD. Furthermore, our results indicate that l-DOPA exerts a therapeutic effect on the parkinsonian brain through different, coexistent, mechanisms.
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Greenhill SD, Chamberlain SEL, Lench A, Massey PV, Yuill KH, Woodhall GL, Jones RSG. Background synaptic activity in rat entorhinal cortex shows a progressively greater dominance of inhibition over excitation from deep to superficial layers. PLoS One 2014; 9:e85125. [PMID: 24454801 PMCID: PMC3893176 DOI: 10.1371/journal.pone.0085125] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 11/22/2013] [Indexed: 11/21/2022] Open
Abstract
The entorhinal cortex (EC) controls hippocampal input and output, playing major roles in memory and spatial navigation. Different layers of the EC subserve different functions and a number of studies have compared properties of neurones across layers. We have studied synaptic inhibition and excitation in EC neurones, and we have previously compared spontaneous synaptic release of glutamate and GABA using patch clamp recordings of synaptic currents in principal neurones of layers II (L2) and V (L5). Here, we add comparative studies in layer III (L3). Such studies essentially look at neuronal activity from a presynaptic viewpoint. To correlate this with the postsynaptic consequences of spontaneous transmitter release, we have determined global postsynaptic conductances mediated by the two transmitters, using a method to estimate conductances from membrane potential fluctuations. We have previously presented some of this data for L3 and now extend to L2 and L5. Inhibition dominates excitation in all layers but the ratio follows a clear rank order (highest to lowest) of L2>L3>L5. The variance of the background conductances was markedly higher for excitation and inhibition in L2 compared to L3 or L5. We also show that induction of synchronized network epileptiform activity by blockade of GABA inhibition reveals a relative reluctance of L2 to participate in such activity. This was associated with maintenance of a dominant background inhibition in L2, whereas in L3 and L5 the absolute level of inhibition fell below that of excitation, coincident with the appearance of synchronized discharges. Further experiments identified potential roles for competition for bicuculline by ambient GABA at the GABAA receptor, and strychnine-sensitive glycine receptors in residual inhibition in L2. We discuss our results in terms of control of excitability in neuronal subpopulations of EC neurones and what these may suggest for their functional roles.
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Affiliation(s)
- Stuart David Greenhill
- Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, United Kingdom
| | | | - Alex Lench
- Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, United Kingdom
| | - Peter Vernon Massey
- Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, United Kingdom
| | - Kathryn Heather Yuill
- School of Biomedical & Healthcare Sciences, Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth, United Kingdom
| | - Gavin Lawrence Woodhall
- Aston Brain Centre, School of Life and Health Sciences, Aston University, Birmingham, United Kingdom
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Witter MP, Canto CB, Couey JJ, Koganezawa N, O'Reilly KC. Architecture of spatial circuits in the hippocampal region. Philos Trans R Soc Lond B Biol Sci 2013; 369:20120515. [PMID: 24366129 DOI: 10.1098/rstb.2012.0515] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The hippocampal region contains several principal neuron types, some of which show distinct spatial firing patterns. The region is also known for its diversity in neural circuits and many have attempted to causally relate network architecture within and between these unique circuits to functional outcome. Still, much is unknown about the mechanisms or network properties by which the functionally specific spatial firing profiles of neurons are generated, let alone how they are integrated into a coherently functioning meta-network. In this review, we explore the architecture of local networks and address how they may interact within the context of an overarching space circuit, aiming to provide directions for future successful explorations.
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Affiliation(s)
- Menno P Witter
- Kavli Institute for Systems Neuroscience and Centre for Neural Computation, Norwegian University of Science and Technology, , 7030 Trondheim, Norway
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Abstract
The medial entorhinal cortex (MEC), presubiculum (PrS), and parasubiculum (PaS) are interconnected components of the hippocampal-parahippocampal spatial-representation system. Principal cells in all layers of MEC show signs of directional tuning, overt in head direction cells present in all layers except for layer II, and covert in grid cells, which are the major spatially modulated cell type in layer II. Directional information likely originates in the head direction-vestibular system and PrS and PaS are thought to provide this information to MEC. Efferents from PaS and PrS show a selective laminar terminal distribution in MEC superficial layers II and III, respectively. We hypothesized that this anatomically determined laminar distribution does not preclude monosynaptic interaction with neurons located in deeper layers of MEC in view of the extensive apical dendrites from deeper cells reaching layers II and III. This hypothesis was tested in the rat using tilted in vitro slices in which origins and terminations of PrS and PaS fibers were maintained, as assessed using anterograde anatomical tracing. Based on voltage-sensitive dye imaging, multipatch single-cell recordings, and scanning photostimulation of caged glutamate, we report first that principal neurons in all layers of MEC receive convergent monosynaptic inputs from PrS and PaS and second, that elicited responses show layer-specific decay times and frequency-dependent facilitation. These results indicate that regardless of their selective laminar terminal distribution, PrS and PaS inputs may monosynaptically convey directional information to principal neurons in all layers of MEC through synapses on their extensive dendritic arbors.
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Cha YH, Chakrapani S, Craig A, Baloh RW. Metabolic and functional connectivity changes in mal de debarquement syndrome. PLoS One 2012; 7:e49560. [PMID: 23209584 PMCID: PMC3510214 DOI: 10.1371/journal.pone.0049560] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Accepted: 10/15/2012] [Indexed: 12/24/2022] Open
Abstract
Background Individuals with mal de debarquement syndrome (MdDS) experience a chronic illusion of self-motion triggered by prolonged exposure to passive motion, such as from sea or air travel. The experience is one of rocking dizziness similar to when the individual was originally on the motion trigger such as a boat or airplane. MdDS represents a prolonged version of a normal phenomenon familiar to most individuals but which persists for months or years in others. It represents a natural example of the neuroplasticity of motion adaptation. However, the localization of where that motion adaptation occurs is unknown. Our goal was to localize metabolic and functional connectivity changes associated with persistent MdDS. Methods Twenty subjects with MdDS lasting a median duration of 17.5 months were compared to 20 normal controls with 18F FDG PET and resting state fMRI. Resting state metabolism and functional connectivity were calculated using age, grey matter volume, and mood and anxiety scores as nuisance covariates. Results MdDS subjects showed increased metabolism in the left entorhinal cortex and amygdala (z>3.3). Areas of relative hypometabolism included the left superior medial gyrus, left middle frontal gyrus, right amygdala, right insula, and clusters in the left superior, middle, and inferior temporal gyri. MdDS subjects showed increased connectivity between the entorhinal cortex/amygdala cluster and posterior visual and vestibular processing areas including middle temporal gyrus, motion sensitive area MT/V5, superior parietal lobule, and primary visual cortex, while showing decreased connectivity to multiple prefrontal areas. Conclusion These data show an association between resting state metabolic activity and functional connectivity between the entorhinal cortex and amygdala in a human disorder of abnormal motion perception. We propose a model for how these biological substrates can allow a limited period of motion exposure to lead to chronic perceptions of self-motion.
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Affiliation(s)
- Yoon-Hee Cha
- Department of Neurology, University of California Los Angeles, Los Angeles, CA, USA.
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Stepan J, Dine J, Fenzl T, Polta SA, von Wolff G, Wotjak CT, Eder M. Entorhinal theta-frequency input to the dentate gyrus trisynaptically evokes hippocampal CA1 LTP. Front Neural Circuits 2012; 6:64. [PMID: 22988432 PMCID: PMC3439738 DOI: 10.3389/fncir.2012.00064] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Accepted: 08/27/2012] [Indexed: 01/01/2023] Open
Abstract
There exists substantial evidence that some forms of explicit learning in mammals require long-term potentiation (LTP) at hippocampal CA3-CA1 synapses. While CA1 LTP has been well characterized at the monosynaptic level, it still remains unclear how the afferent systems to the hippocampus can initiate formation of this neuroplastic phenomenon. Using voltage-sensitive dye imaging (VSDI) in a mouse brain slice preparation, we show that evoked entorhinal cortical (EC) theta-frequency input to the dentate gyrus highly effectively generates waves of neuronal activity which propagate through the entire trisynaptic circuit of the hippocampus (“HTC-Waves”). This flow of activity, which we also demonstrate in vivo, critically depends on frequency facilitation of mossy fiber to CA3 synaptic transmission. The HTC-Waves are rapidly boosted by the cognitive enhancer caffeine (5 μM) and the stress hormone corticosterone (100 nM). They precisely follow the rhythm of the EC input, involve high-frequency firing (>100 Hz) of CA3 pyramidal neurons, and induce NMDA receptor-dependent CA1 LTP within a few seconds. Our study provides the first experimental evidence that synchronous theta-rhythmical spiking of EC stellate cells, as occurring during EC theta oscillations, has the capacity to drive induction of CA1 LTP via the hippocampal trisynaptic pathway. Moreover, we present data pointing to a basic filter mechanism of the hippocampus regarding EC inputs and describe a methodology to reveal alterations in the “input–output relationship” of the hippocampal trisynaptic circuit.
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Affiliation(s)
- Jens Stepan
- Research Group Neuronal Network Dynamics, Max Planck Institute of Psychiatry Munich, Germany
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Zhang XM, Zhu J. Kainic Acid-induced neurotoxicity: targeting glial responses and glia-derived cytokines. Curr Neuropharmacol 2012; 9:388-98. [PMID: 22131947 PMCID: PMC3131729 DOI: 10.2174/157015911795596540] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2009] [Revised: 09/28/2010] [Accepted: 10/18/2010] [Indexed: 01/01/2023] Open
Abstract
Glutamate excitotoxicity contributes to a variety of disorders in the central nervous system, which is triggered primarily by excessive Ca2+ influx arising from overstimulation of glutamate receptors, followed by disintegration of the endoplasmic reticulum (ER) membrane and ER stress, the generation and detoxification of reactive oxygen species as well as mitochondrial dysfunction, leading to neuronal apoptosis and necrosis. Kainic acid (KA), a potent agonist to the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate class of glutamate receptors, is 30-fold more potent in neuro-toxicity than glutamate. In rodents, KA injection resulted in recurrent seizures, behavioral changes and subsequent degeneration of selective populations of neurons in the brain, which has been widely used as a model to study the mechanisms of neurodegenerative pathways induced by excitatory neurotransmitter. Microglial activation and astrocytes proliferation are the other characteristics of KA-induced neurodegeneration. The cytokines and other inflammatory molecules secreted by activated glia cells can modify the outcome of disease progression. Thus, anti-oxidant and anti-inflammatory treatment could attenuate or prevent KA-induced neurodegeneration. In this review, we summarized updated experimental data with regard to the KA-induced neurotoxicity in the brain and emphasized glial responses and glia-oriented cytokines, tumor necrosis factor-α, interleukin (IL)-1, IL-12 and IL-18.
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Affiliation(s)
- Xing-Mei Zhang
- Department of Neurobiology, Care Sciences and Society, Karolinska Institute, Stockholm, Sweden
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Pilli J, Abbasi S, Richardson M, Kumar SS. Diversity and excitability of deep-layer entorhinal cortical neurons in a model of temporal lobe epilepsy. J Neurophysiol 2012; 108:1724-38. [PMID: 22745466 DOI: 10.1152/jn.00364.2012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The entorhinal cortex (ERC) is critically implicated in temporal lobe epileptogenesis--the most common type of adult epilepsy. Previous studies have suggested that epileptiform discharges likely initiate in seizure-sensitive deep layers (V-VI) of the medial entorhinal area (MEA) and propagate into seizure-resistant superficial layers (II-III) and hippocampus, establishing a lamina-specific distinction between activities of deep- versus superficial-layer neurons and their seizure susceptibilities. While layer II stellate cells in MEA have been shown to be hyperexcitable and hypersynchronous in patients and animal models of temporal lobe epilepsy (TLE), the fate of neurons in the deep layers under epileptic conditions and their overall contribution to epileptogenicity of this region have remained unclear. We used whole cell recordings from slices of the ERC in normal and pilocarpine-treated epileptic rats to characterize the electrophysiological properties of neurons in this region and directly assess changes in their excitatory and inhibitory synaptic drive under epileptic conditions. We found a surprising heterogeneity with at least three major types and two subtypes of functionally distinct excitatory neurons. However, contrary to expectation, none of the major neuron types characterized showed any significant changes in their excitability, barring loss of excitatory and inhibitory inputs in a subtype of neurons whose dendrite extended into layer III, where neurons are preferentially lost during TLE. We confirmed hyperexcitability of layer II neurons in the same slices, suggesting minimal influence of deep-layer input on superficial-layer neuron excitability under epileptic conditions. These data show that deep layers of ERC contain a more diverse population of excitatory neurons than previously envisaged that appear to belie their seizure-sensitive reputation.
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Affiliation(s)
- Jyotsna Pilli
- Dept. of Biomedical Sciences, College of Medicine, Florida State Univ., 1115 West Call St., Tallahassee, FL 32306-4300, USA
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Nomoto S, Yamamoto T, Tomioka JI, Nomoto E. Changes in synaptic efficacy of dentate granule cells during operant behavior in rats. Physiol Behav 2012; 105:938-47. [PMID: 22108509 DOI: 10.1016/j.physbeh.2011.11.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Revised: 11/01/2011] [Accepted: 11/07/2011] [Indexed: 12/20/2022]
Abstract
It is widely accepted that long-term potentiation (LTP) is one of the fundamental physiological mechanisms underlying memory function based on its response properties and behavior of the induced sites. Many experimental approaches have been used to investigate whether the mechanisms underlying LTP are activated during learning and whether these mechanisms underlie the formation of certain types of memory. However, relatively few studies have reported the time course of changes in the efficacy of synaptic transmission in the learning process. We simultaneously monitored changes in slope of field EPSPs (fEPSP slope) and the amplitude of population spikes (pop. spike) in perforant path-evoked potentials in the dentate gyrus over the course of an appetitively motivated operant paradigm in freely moving rats. We found that the fEPSP slope recorded from the granule cell layer was potentiated about 7%, the fEPSP slope recorded from the molecular layer was depressed about 20%, and the amplitude of pop. spike recorded from the granule cell layer was significantly depressed about 40% after the trial in which rats began to press the lever frequently. These results suggested that the granule cells in the dentate gyrus received excitatory inputs in the somatic region and inhibitory inputs in the dendritic region, and that outputs from the granule cells were significantly reduced in the process of acquisition of the operant behavioral task. We observed no LTP in this study although our rats were capable of having LTP induced by a high-frequency stimulus. The depression of fEPSP slope induced without any artificial stimulation in this study is thought to be another neural mechanism underlying learning and memory. The origins of excitatory and inhibitory inputs are unknown at the moment.
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Affiliation(s)
- Shigeki Nomoto
- Department of Central Nervous System, Tokyo Metropolitan Institute of Gerontology, Itabashi-ku, Tokyo 173-0015, Japan.
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Insights into spared memory capacity in amnestic MCI and Alzheimer's Disease via minimal interference. Brain Cogn 2012; 78:189-99. [PMID: 22261228 DOI: 10.1016/j.bandc.2011.12.005] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 12/01/2011] [Accepted: 12/06/2011] [Indexed: 01/02/2023]
Abstract
Impairment on standard tests of delayed recall is often already maximal in the aMCI stage of Alzheimer's Disease. Neuropathological work shows that the neural substrates of memory function continue to deteriorate throughout the progression of the disease, hinting that further changes in memory performance could be tracked by a more sensitive test of delayed recall. Recent work shows that retention in aMCI patients can be raised well above floor when the delay period is devoid of further material - 'Minimal Interference'. This memory enhancement is thought to be the result of improved memory consolidation. Here we used the minimal interference/interference paradigm (word list retention following 10 min of quiet resting vs. picture naming) in a group of 17 AD patients, 25 aMCI patients and 25 controls. We found (1) that retention can be improved significantly by minimal interference in patients with aMCI and patients with mild to moderate AD; (2) that the minimal interference paradigm is sensitive to decline in memory function with disease severity, even when performance on standard tests has reached floor; and (3) that this paradigm can differentiate well (80% sensitivity and 100% specificity) between aMCI patients who progress and do not progress to AD within 2 years. Our findings support the notion that the early memory dysfunction in AD is associated with an increased susceptibility to memory interference and are suggestive of a gradual decline in consolidation capacity with disease progression.
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Da Silva FHL, Gorter JA, Wadman WJ. Epilepsy as a dynamic disease of neuronal networks. HANDBOOK OF CLINICAL NEUROLOGY 2012; 107:35-62. [DOI: 10.1016/b978-0-444-52898-8.00003-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Canto CB, Witter MP. Cellular properties of principal neurons in the rat entorhinal cortex. I. The lateral entorhinal cortex. Hippocampus 2011; 22:1256-76. [PMID: 22162008 DOI: 10.1002/hipo.20997] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/22/2011] [Indexed: 11/10/2022]
Abstract
The lateral entorhinal cortex (LEC) provides a major cortical input to the hippocampal formation, equaling that of the medial entorhinal cortex (MEC). To understand the functional contributions made by LEC, basic knowledge of individual neurons, in the context of the intrinsic network, is needed. The aim of this study is to compare physiological and morphological properties of principal neurons in different LEC layers in postnatal rats. Using in vitro whole cell current-clamp recordings from up to four post hoc morphologically identified neurons simultaneously, we established that principal neurons show layer specific physiological and morphological properties, similar to those reported previously in adults. Principal neurons in L(ayer) I, LII, and LIII have the majority of their dendrites and axonal collaterals alone in superficial layers. LV contains mainly pyramidal neurons with dendrites and axons extending throughout all layers. A minority of LV and all principal neurons in LVI are neurons with dendrites confined to deep layers and axons in superficial and deep layers. Physiologically, input resistances and time constants of LII neurons are lower and shorter, respectively, than those observed in LV neurons. Fifty-four percent of LII neurons have sag potentials, resonance properties, and rebounds at the offset of hyperpolarizing current injection, whereas LIII and LVI neurons do not have any of these. LV neurons show prominent spike-frequency adaptation and a decrease in spike amplitudes in response to strong depolarization. Despite the well-developed interlaminar communication in LEC, the laminar differences in the biophysical and morphological properties of neurons suggest that their in vivo firing patterns and functions differ, similar to what is known for neurons in different MEC layers.
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Affiliation(s)
- Cathrin B Canto
- Kavli Institute for Systems Neuroscience and Centre for the Biology of Memory, Norwegian University of Science and Technology, Trondheim, Norway
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Avoli M, de Curtis M. GABAergic synchronization in the limbic system and its role in the generation of epileptiform activity. Prog Neurobiol 2011; 95:104-32. [PMID: 21802488 PMCID: PMC4878907 DOI: 10.1016/j.pneurobio.2011.07.003] [Citation(s) in RCA: 193] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 07/14/2011] [Accepted: 07/15/2011] [Indexed: 11/30/2022]
Abstract
GABA is the main inhibitory neurotransmitter in the adult forebrain, where it activates ionotropic type A and metabotropic type B receptors. Early studies have shown that GABA(A) receptor-mediated inhibition controls neuronal excitability and thus the occurrence of seizures. However, more complex, and at times unexpected, mechanisms of GABAergic signaling have been identified during epileptiform discharges over the last few years. Here, we will review experimental data that point at the paradoxical role played by GABA(A) receptor-mediated mechanisms in synchronizing neuronal networks, and in particular those of limbic structures such as the hippocampus, the entorhinal and perirhinal cortices, or the amygdala. After having summarized the fundamental characteristics of GABA(A) receptor-mediated mechanisms, we will analyze their role in the generation of network oscillations and their contribution to epileptiform synchronization. Whether and how GABA(A) receptors influence the interaction between limbic networks leading to ictogenesis will be also reviewed. Finally, we will consider the role of altered inhibition in the human epileptic brain along with the ability of GABA(A) receptor-mediated conductances to generate synchronous depolarizing events that may lead to ictogenesis in human epileptic disorders as well.
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Affiliation(s)
- Massimo Avoli
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery, and of Physiology, McGill University, Montreal H3A 2B4 Quebec, Canada.
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Beed P, Bendels MHK, Wiegand HF, Leibold C, Johenning FW, Schmitz D. Analysis of excitatory microcircuitry in the medial entorhinal cortex reveals cell-type-specific differences. Neuron 2011; 68:1059-66. [PMID: 21172609 DOI: 10.1016/j.neuron.2010.12.009] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/29/2010] [Indexed: 11/28/2022]
Abstract
Medial entorhinal cortex (MEC) plays an important role in physiological processes underlying navigation, learning, and memory. Excitatory cells in the different MEC layers project in a region-specific manner to the hippocampus. However, the intrinsic microcircuitry of the main excitatory cells in the superficial MEC layers is largely unknown. Using scanning photostimulation, we investigated the functional microcircuitry of two such cell types, stellate and pyramidal cells. We found cell-type-specific intralaminar and ascending interlaminar feedback inputs. The ascending interlaminar inputs display distinct organizational principles depending on the cell-type and its position within the superficial lamina: the spatial spread of inputs for stellate cells is narrower than for pyramidal cells, while inputs to pyramidal cells in layer 3, but not in layer 2, exhibit an asymmetric offset to the medial side of the cell's main axis. Differential laminar sources of excitatory inputs might contribute to the functional diversity of stellate and pyramidal cells.
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Affiliation(s)
- Prateep Beed
- Neuroscience Research Center, Charité-Universitätsmedizin Berlin, 10117 Berlin, Germany
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Drew MR, Denny CA, Hen R. Arrest of adult hippocampal neurogenesis in mice impairs single- but not multiple-trial contextual fear conditioning. Behav Neurosci 2010; 124:446-54. [PMID: 20695644 DOI: 10.1037/a0020081] [Citation(s) in RCA: 132] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The role of adult hippocampal neurogenesis in contextual fear conditioning (CFC) is debated. Several studies demonstrated that blocking adult hippocampal neurogenesis in rodents impairs CFC, while several other studies failed to observe an impairment. We sought to determine whether different CFC methods vary in their sensitivity to the arrest of adult neurogenesis. Adult neurogenesis was arrested in mice using low-dose, targeted x-irradiation, and the effects of irradiation were assayed in conditioning procedures that varied in the use of a discrete conditioned stimulus, the number of trials administered, and the final level of conditioning produced. We demonstrate that irradiation impairs CFC in mice when a single-trial CFC procedure is used but not when multiple-trial procedures are used, regardless of the final level of contextual fear produced. In addition, we show that the irradiation-induced deficit in single-trial CFC can be rescued by providing preexposure to the conditioning context. These results indicate that adult hippocampal neurogenesis is required for CFC in mice only when brief training is provided.
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Affiliation(s)
- Michael R Drew
- Department of Psychiatry, Columbia University, New York, NY 10032, USA.
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Chen L, Cai W, Chen L, Zhou R, Furuya K, Sokabe M. Modulatory metaplasticity induced by pregnenolone sulfate in the rat hippocampus: a leftward shift in LTP/LTD-frequency curve. Hippocampus 2010; 20:499-512. [PMID: 19475651 DOI: 10.1002/hipo.20649] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
We recently have found that an acute application of the neurosteroid pregnenolone sulfate (PREGS) at 50 muM to rat hippocampal slices induces a long-lasting potentiation (LLP(PREGS)) via a sustained ERK2/CREB activation at perforant-path/granule-cell synapses in the dentate gyrus. This study is a follow up to investigate whether the expression of LLP(PREGS) influences subsequent frequency-dependent synaptic plasticity. Conditioning electric stimuli (CS) at 0.1-200 Hz were given to the perforant-path of rat hippocampal slices expressing LLP(PREGS) to induce long-term potentiation (LTP) and long-term depression (LTD). The largest LTP was induced at about 20 Hz-CS, which is normally a subthreshold frequency, and the largest LTD at 0.5 Hz-CS, resulting in a leftward-shift of the LTP/LTD-frequency curve. Furthermore, the level of LTP at 100 Hz-CS was significantly attenuated to give band-pass filter characteristics of LTP induction with a center frequency of about 20 Hz. The LTP induced by 20 Hz-CS (termed 20 Hz-LTP) was found to be postsynaptic origin and dependent on L-type voltage-gated calcium channel (L-VGCC) but not on N-methyl-D-aspartate receptor (NMDAr). Moreover, the induction of 20 Hz-LTP required a sustained activation of ERK2 that had been triggered by PREGS. In conclusion, the transient elevation of PREGS is suggested to induce a modulatory metaplasticity through a sustained activation of ERK2 in an L-VGCC dependent manner.
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Affiliation(s)
- Ling Chen
- Laboratory of Reproductive Medicine, Department of Physiology, Nanjing Medical University, Nanjing, China.
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