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Harley P, Kerins C, Gatt A, Neves G, Riccio F, Machado CB, Cheesbrough A, R'Bibo L, Burrone J, Lieberam I. Aberrant axon initial segment plasticity and intrinsic excitability of ALS hiPSC motor neurons. Cell Rep 2023; 42:113509. [PMID: 38019651 DOI: 10.1016/j.celrep.2023.113509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 10/06/2023] [Accepted: 11/13/2023] [Indexed: 12/01/2023] Open
Abstract
Dysregulated neuronal excitability is a hallmark of amyotrophic lateral sclerosis (ALS). We sought to investigate how functional changes to the axon initial segment (AIS), the site of action potential generation, could impact neuronal excitability in ALS human induced pluripotent stem cell (hiPSC) motor neurons. We find that early TDP-43 and C9orf72 hiPSC motor neurons show an increase in the length of the AIS and impaired activity-dependent AIS plasticity that is linked to abnormal homeostatic regulation of neuronal activity and intrinsic hyperexcitability. In turn, these hyperactive neurons drive increased spontaneous myofiber contractions of in vitro hiPSC motor units. In contrast, late hiPSC and postmortem ALS motor neurons show AIS shortening, and hiPSC motor neurons progress to hypoexcitability. At a molecular level, aberrant expression of the AIS master scaffolding protein ankyrin-G and AIS-specific voltage-gated sodium channels mirror these dynamic changes in AIS function and excitability. Our results point toward the AIS as an important site of dysfunction in ALS motor neurons.
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Affiliation(s)
- Peter Harley
- Centre for Gene Therapy & Regenerative Medicine, Kings College London, London SE1 9RT, UK; Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, UK; UCL Queen Square Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, UCL, London, UK
| | - Caoimhe Kerins
- Centre for Gene Therapy & Regenerative Medicine, Kings College London, London SE1 9RT, UK; Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, UK; Centre for Craniofacial & Regenerative Biology, King's College London, London SE1 9RT, UK
| | - Ariana Gatt
- Queen Square Brain Bank, Department of Neurodegenerative Disease, Institute of Neurology, University College London, London WC1N 1PJ, UK
| | - Guilherme Neves
- Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, UK
| | - Federica Riccio
- Centre for Gene Therapy & Regenerative Medicine, Kings College London, London SE1 9RT, UK; Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, UK
| | - Carolina Barcellos Machado
- Centre for Gene Therapy & Regenerative Medicine, Kings College London, London SE1 9RT, UK; Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, UK
| | - Aimee Cheesbrough
- Centre for Gene Therapy & Regenerative Medicine, Kings College London, London SE1 9RT, UK; Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, UK
| | - Lea R'Bibo
- Centre for Gene Therapy & Regenerative Medicine, Kings College London, London SE1 9RT, UK; Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, UK
| | - Juan Burrone
- Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, UK; MRC Centre for Neurodevelopmental Disorders, Kings College London, London SE1 1UL, UK.
| | - Ivo Lieberam
- Centre for Gene Therapy & Regenerative Medicine, Kings College London, London SE1 9RT, UK; Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, UK; MRC Centre for Neurodevelopmental Disorders, Kings College London, London SE1 1UL, UK.
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2
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Rigby M, Grillo FW, Compans B, Neves G, Gallinaro J, Nashashibi S, Horton S, Pereira Machado PM, Carbajal MA, Vizcay-Barrena G, Levet F, Sibarita JB, Kirkland A, Fleck RA, Clopath C, Burrone J. Multi-synaptic boutons are a feature of CA1 hippocampal connections in the stratum oriens. Cell Rep 2023; 42:112397. [PMID: 37074915 PMCID: PMC10695768 DOI: 10.1016/j.celrep.2023.112397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 01/21/2023] [Accepted: 03/30/2023] [Indexed: 04/20/2023] Open
Abstract
Excitatory synapses are typically described as single synaptic boutons (SSBs), where one presynaptic bouton contacts a single postsynaptic spine. Using serial section block-face scanning electron microscopy, we found that this textbook definition of the synapse does not fully apply to the CA1 region of the hippocampus. Roughly half of all excitatory synapses in the stratum oriens involved multi-synaptic boutons (MSBs), where a single presynaptic bouton containing multiple active zones contacted many postsynaptic spines (from 2 to 7) on the basal dendrites of different cells. The fraction of MSBs increased during development (from postnatal day 22 [P22] to P100) and decreased with distance from the soma. Curiously, synaptic properties such as active zone (AZ) or postsynaptic density (PSD) size exhibited less within-MSB variation when compared with neighboring SSBs, features that were confirmed by super-resolution light microscopy. Computer simulations suggest that these properties favor synchronous activity in CA1 networks.
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Affiliation(s)
- Mark Rigby
- MRC Centre for Neurodevelopmental Disorders, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK; Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK
| | - Federico W Grillo
- MRC Centre for Neurodevelopmental Disorders, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK; Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK
| | - Benjamin Compans
- MRC Centre for Neurodevelopmental Disorders, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK; Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK
| | - Guilherme Neves
- MRC Centre for Neurodevelopmental Disorders, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK; Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK; The Rosalind Franklin Institute, Harwell Campus, Didcot OX11 0FA, UK
| | - Julia Gallinaro
- Bioengineering Department, Imperial College London, London, UK
| | - Sophie Nashashibi
- MRC Centre for Neurodevelopmental Disorders, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK; Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK
| | - Sally Horton
- MRC Centre for Neurodevelopmental Disorders, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK; Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK
| | - Pedro M Pereira Machado
- Centre for Ultrastructural Imaging (CUI), Kings College London, New Hunts House, Guys Hospital Campus, London SE1 1UL, UK
| | - Maria Alejandra Carbajal
- Centre for Ultrastructural Imaging (CUI), Kings College London, New Hunts House, Guys Hospital Campus, London SE1 1UL, UK
| | - Gema Vizcay-Barrena
- Centre for Ultrastructural Imaging (CUI), Kings College London, New Hunts House, Guys Hospital Campus, London SE1 1UL, UK
| | - Florian Levet
- University Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297, 33000 Bordeaux, France; University Bordeaux, CNRS, INSERM, Bordeaux Imaging Center, BIC, UAR3420, US 4, 33000 Bordeaux, France
| | - Jean-Baptiste Sibarita
- University Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297, 33000 Bordeaux, France
| | - Angus Kirkland
- The Rosalind Franklin Institute, Harwell Campus, Didcot OX11 0FA, UK
| | - Roland A Fleck
- Centre for Ultrastructural Imaging (CUI), Kings College London, New Hunts House, Guys Hospital Campus, London SE1 1UL, UK
| | - Claudia Clopath
- Bioengineering Department, Imperial College London, London, UK
| | - Juan Burrone
- MRC Centre for Neurodevelopmental Disorders, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK; Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK.
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3
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Braga L, Ali H, Secco I, Chiavacci E, Neves G, Goldhill D, Penn R, Jimenez-Guardeño JM, Ortega-Prieto AM, Bussani R, Cannatà A, Rizzari G, Collesi C, Schneider E, Arosio D, Shah AM, Barclay WS, Malim MH, Burrone J, Giacca M. Drugs that inhibit TMEM16 proteins block SARS-CoV-2 spike-induced syncytia. Nature 2021; 594:88-93. [PMID: 33827113 PMCID: PMC7611055 DOI: 10.1038/s41586-021-03491-6] [Citation(s) in RCA: 246] [Impact Index Per Article: 82.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 03/25/2021] [Indexed: 02/01/2023]
Abstract
COVID-19 is a disease with unique characteristics that include lung thrombosis1, frequent diarrhoea2, abnormal activation of the inflammatory response3 and rapid deterioration of lung function consistent with alveolar oedema4. The pathological substrate for these findings remains unknown. Here we show that the lungs of patients with COVID-19 contain infected pneumocytes with abnormal morphology and frequent multinucleation. The generation of these syncytia results from activation of the SARS-CoV-2 spike protein at the cell plasma membrane level. On the basis of these observations, we performed two high-content microscopy-based screenings with more than 3,000 approved drugs to search for inhibitors of spike-driven syncytia. We converged on the identification of 83 drugs that inhibited spike-mediated cell fusion, several of which belonged to defined pharmacological classes. We focused our attention on effective drugs that also protected against virus replication and associated cytopathicity. One of the most effective molecules was the antihelminthic drug niclosamide, which markedly blunted calcium oscillations and membrane conductance in spike-expressing cells by suppressing the activity of TMEM16F (also known as anoctamin 6), a calcium-activated ion channel and scramblase that is responsible for exposure of phosphatidylserine on the cell surface. These findings suggest a potential mechanism for COVID-19 disease pathogenesis and support the repurposing of niclosamide for therapy.
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Affiliation(s)
- Luca Braga
- King's College London, British Heart Foundation Centre of Research Excellence, School of Cardiovascular Medicine & Sciences, London, UK
| | - Hashim Ali
- King's College London, British Heart Foundation Centre of Research Excellence, School of Cardiovascular Medicine & Sciences, London, UK
| | - Ilaria Secco
- King's College London, British Heart Foundation Centre of Research Excellence, School of Cardiovascular Medicine & Sciences, London, UK
| | - Elena Chiavacci
- King's College London, British Heart Foundation Centre of Research Excellence, School of Cardiovascular Medicine & Sciences, London, UK
| | - Guilherme Neves
- MRC Centre for Neurodevelopmental Disorders, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
- Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - Daniel Goldhill
- Department of Infectious Diseases, Imperial College London, London, UK
| | - Rebecca Penn
- Department of Infectious Diseases, Imperial College London, London, UK
| | - Jose M Jimenez-Guardeño
- Department of Infectious Diseases, School of Immunology & Microbial Sciences, King's College London, London, UK
| | - Ana M Ortega-Prieto
- Department of Infectious Diseases, School of Immunology & Microbial Sciences, King's College London, London, UK
| | - Rossana Bussani
- Department of Medical, Surgical and Health Sciences, University of Trieste, Trieste, Italy
| | - Antonio Cannatà
- King's College London, British Heart Foundation Centre of Research Excellence, School of Cardiovascular Medicine & Sciences, London, UK
| | - Giorgia Rizzari
- King's College London, British Heart Foundation Centre of Research Excellence, School of Cardiovascular Medicine & Sciences, London, UK
| | - Chiara Collesi
- Department of Medical, Surgical and Health Sciences, University of Trieste, Trieste, Italy
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Trieste, Italy
| | - Edoardo Schneider
- King's College London, British Heart Foundation Centre of Research Excellence, School of Cardiovascular Medicine & Sciences, London, UK
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Trieste, Italy
| | - Daniele Arosio
- Istituto di Biofisica (IBF), Consiglio Nazionale delle Ricerche (CNR), Trento, Italy
| | - Ajay M Shah
- King's College London, British Heart Foundation Centre of Research Excellence, School of Cardiovascular Medicine & Sciences, London, UK
| | - Wendy S Barclay
- Department of Infectious Diseases, Imperial College London, London, UK
| | - Michael H Malim
- Department of Infectious Diseases, School of Immunology & Microbial Sciences, King's College London, London, UK
| | - Juan Burrone
- MRC Centre for Neurodevelopmental Disorders, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
- Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - Mauro Giacca
- King's College London, British Heart Foundation Centre of Research Excellence, School of Cardiovascular Medicine & Sciences, London, UK.
- Department of Medical, Surgical and Health Sciences, University of Trieste, Trieste, Italy.
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Trieste, Italy.
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Pan-Vazquez A, Wefelmeyer W, Gonzalez Sabater V, Neves G, Burrone J. Activity-Dependent Plasticity of Axo-axonic Synapses at the Axon Initial Segment. Neuron 2020; 106:265-276.e6. [PMID: 32109363 PMCID: PMC7181187 DOI: 10.1016/j.neuron.2020.01.037] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 12/06/2019] [Accepted: 01/27/2020] [Indexed: 12/20/2022]
Abstract
The activity-dependent rules that govern the wiring of GABAergic interneurons are not well understood. Chandelier cells (ChCs) are a type of GABAergic interneuron that control pyramidal cell output through axo-axonic synapses that target the axon initial segment. In vivo imaging of ChCs during development uncovered a narrow window (P12-P18) over which axons arborized and formed connections. We found that increases in the activity of either pyramidal cells or individual ChCs during this temporal window result in a reversible decrease in axo-axonic connections. Voltage imaging of GABAergic transmission at the axon initial segment (AIS) showed that axo-axonic synapses were depolarizing during this period. Identical manipulations of network activity in older mice (P40-P46), when ChC synapses are inhibitory, resulted instead in an increase in axo-axonic synapses. We propose that the direction of ChC synaptic plasticity follows homeostatic rules that depend on the polarity of axo-axonic synapses.
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Affiliation(s)
- Alejandro Pan-Vazquez
- MRC Centre for Neurodevelopmental Disorders, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK; Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK
| | - Winnie Wefelmeyer
- MRC Centre for Neurodevelopmental Disorders, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK; Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK
| | - Victoria Gonzalez Sabater
- MRC Centre for Neurodevelopmental Disorders, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK; Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK
| | - Guilherme Neves
- MRC Centre for Neurodevelopmental Disorders, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK; Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK; The Rosalind Franklin Institute, Harwell Campus, Didcot OX11 0FA, UK
| | - Juan Burrone
- MRC Centre for Neurodevelopmental Disorders, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK; Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK.
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5
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Denaxa M, Neves G, Burrone J, Pachnis V. Transplantation of Chemogenetically Engineered Cortical Interneuron Progenitors into Early Postnatal Mouse Brains. J Vis Exp 2019. [PMID: 31498303 DOI: 10.3791/59568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Neuronal development is regulated by a complex combination of environmental and genetic factors. Assessing the relative contribution of each component is a complicated task, which is particularly difficult in regards to the development of γ-aminobutyric acid (GABA)ergic cortical interneurons (CIs). CIs are the main inhibitory neurons in the cerebral cortex, and they play key roles in neuronal networks, by regulating both the activity of individual pyramidal neurons, as well as the oscillatory behavior of neuronal ensembles. They are generated in transient embryonic structures (medial and caudal ganglionic eminences - MGE and CGE) that are very difficult to efficiently target using in utero electroporation approaches. Interneuron progenitors migrate long distances during normal embryonic development, before they integrate in the cortical circuit. This remarkable ability to disperse and integrate into a developing network can be hijacked by transplanting embryonic interneuron precursors into early post-natal host cortices. Here, we present a protocol that allows genetic modification of embryonic interneuron progenitors using focal ex vivo electroporation. These engineered interneuron precursors are then transplanted into early post-natal host cortices, where they will mature into easily identifiable CIs. This protocol allows the use of multiple genetically encoded tools, or the ability to regulate the expression of specific genes in interneuron progenitors, in order to investigate the impact of either genetic or environmental variables on the maturation and integration of CIs.
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Affiliation(s)
- Myrto Denaxa
- Nervous System Development and Homeostasis Laboratory, The Francis Crick Institute; Neuroscience Centre, Biomedical Sciences Research Centre "Al. Fleming";
| | - Guilherme Neves
- Centre for Developmental Neurobiology, King's College London
| | - Juan Burrone
- Centre for Developmental Neurobiology, King's College London
| | - Vassilis Pachnis
- Nervous System Development and Homeostasis Laboratory, The Francis Crick Institute
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6
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Denaxa M, Neves G, Rabinowitz A, Kemlo S, Liodis P, Burrone J, Pachnis V. Modulation of Apoptosis Controls Inhibitory Interneuron Number in the Cortex. Cell Rep 2019; 22:1710-1721. [PMID: 29444425 PMCID: PMC6230259 DOI: 10.1016/j.celrep.2018.01.064] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 12/18/2017] [Accepted: 01/22/2018] [Indexed: 12/20/2022] Open
Abstract
Cortical networks are composed of excitatory projection neurons and inhibitory interneurons. Finding the right balance between the two is important for controlling overall cortical excitation and network dynamics. However, it is unclear how the correct number of cortical interneurons (CIs) is established in the mammalian forebrain. CIs are generated in excess from basal forebrain progenitors, and their final numbers are adjusted via an intrinsically determined program of apoptosis that takes place during an early postnatal window. Here, we provide evidence that the extent of CI apoptosis during this critical period is plastic and cell-type specific and can be reduced in a cell-autonomous manner by acute increases in neuronal activity. We propose that the physiological state of the emerging neural network controls the activity levels of local CIs to modulate their numbers in a homeostatic manner. Lhx6 is required for survival of CIs generated in the MGE MGE-derived CI loss is compensated for by a decrease in CGE-derived interneuron apoptosis Increases in cortical network activity are correlated with improved CI survival Transient, cell-autonomous depolarization improves the survival of grafted CIs
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Affiliation(s)
- Myrto Denaxa
- Nervous System Development and Homeostasis Laboratory, Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.
| | - Guilherme Neves
- Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK; MRC Centre for Neurodevelopmental Disorders, King's College London, London SE1 1UL, UK.
| | - Adam Rabinowitz
- Bioinformatics and Biostatistics Laboratory, Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Sarah Kemlo
- Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK; MRC Centre for Neurodevelopmental Disorders, King's College London, London SE1 1UL, UK
| | - Petros Liodis
- Molecular Neurobiology, National Institute for Medical Research, the Ridgeway, Mill Hill, London NW7 1AA, UK
| | - Juan Burrone
- Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK; MRC Centre for Neurodevelopmental Disorders, King's College London, London SE1 1UL, UK.
| | - Vassilis Pachnis
- Nervous System Development and Homeostasis Laboratory, Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.
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Denaxa M, Neves G, Burrone J, Pachnis V. Homeostatic Regulation of Interneuron Apoptosis During Cortical Development. J Exp Neurosci 2018; 12:1179069518784277. [PMID: 30013387 PMCID: PMC6043931 DOI: 10.1177/1179069518784277] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 05/29/2018] [Indexed: 12/31/2022] Open
Abstract
The mammalian cortex consists of two main neuronal types: the principal excitatory pyramidal neurons (PNs) and the inhibitory interneurons (INs). The interplay between these two neuronal populations – which drive excitation and inhibition (E/I balance), respectively – is crucial for controlling the overall activity in the brain. A number of neurological and psychiatric disorders have been associated with changes in E/I balance. It is not surprising, therefore, that neural networks employ several different mechanisms to maintain their firing rates at a stable level, collectively referred as homeostatic forms of plasticity. Here, we share our views on how the size of IN populations may provide an early homeostatic checkpoint for controlling brain activity. In a recent paper published in Cell Reports, we demonstrate that the extent of IN apoptosis during a critical early postnatal period is plastic, cell type specific, and can be reduced in a cell-autonomous manner by acute increases in neuronal activity. We propose that a critical interplay between the physiological state of the network and its cellular units fine-tunes the size of IN populations with the aim of stabilizing network activity.
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Affiliation(s)
- Myrto Denaxa
- Development and Function of Cortical Interneurons Lab, BSRC Al. Fleming, Athens, Greece
| | - Guilherme Neves
- Centre for Developmental Neurobiology, King's College London, London, UK
| | - Juan Burrone
- Centre for Developmental Neurobiology, King's College London, London, UK
| | - Vassilis Pachnis
- Development and Homeostasis of the Nervous System Laboratory, The Francis Crick Institute, London, UK
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Grillo FW, Neves G, Walker A, Vizcay-Barrena G, Fleck RA, Branco T, Burrone J. A Distance-Dependent Distribution of Presynaptic Boutons Tunes Frequency-Dependent Dendritic Integration. Neuron 2018; 99:275-282.e3. [PMID: 29983327 PMCID: PMC6078905 DOI: 10.1016/j.neuron.2018.06.015] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 03/23/2018] [Accepted: 06/08/2018] [Indexed: 11/28/2022]
Abstract
How presynaptic inputs and neurotransmitter release dynamics are distributed along a dendritic tree is not well established. Here, we show that presynaptic boutons that form onto basal dendrites of CA1 pyramidal neurons display a decrease in active zone (AZ) size with distance from the soma, resulting in a distance-dependent increase in short-term facilitation. Our findings suggest that the spatial distribution of short-term facilitation serves to compensate for the electrotonic attenuation of subthreshold distal inputs during repeated stimulation and fine-tunes the preferred input frequency of dendritic domains. Presynaptic inputs decrease in size with distance along CA1 basal dendrites Release probability decreases with distance along basal dendrites Short-term facilitation increases with distance along basal dendrites Increased synaptic facilitation offsets passive decay and boosts supralinear events
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Affiliation(s)
- Federico W Grillo
- Centre for Developmental Neurobiology, Kings College London, New Hunts House, Guys Hospital Campus, London, SE1 1UL, UK; MRC Centre for Neurodevelopmental Disorders, Kings College London, New Hunts House, Guys Hospital Campus, London, SE1 1UL, UK
| | - Guilherme Neves
- Centre for Developmental Neurobiology, Kings College London, New Hunts House, Guys Hospital Campus, London, SE1 1UL, UK; MRC Centre for Neurodevelopmental Disorders, Kings College London, New Hunts House, Guys Hospital Campus, London, SE1 1UL, UK
| | - Alison Walker
- Centre for Developmental Neurobiology, Kings College London, New Hunts House, Guys Hospital Campus, London, SE1 1UL, UK
| | - Gema Vizcay-Barrena
- Centre for Ultrastructural Imaging (CUI), Kings College London, New Hunts House, Guys Hospital Campus, London, SE1 1UL, UK
| | - Roland A Fleck
- Centre for Ultrastructural Imaging (CUI), Kings College London, New Hunts House, Guys Hospital Campus, London, SE1 1UL, UK
| | - Tiago Branco
- The Sainsbury Wellcome Centre, University College London, 25 Howland Street, London, W1T 4JG, UK
| | - Juan Burrone
- Centre for Developmental Neurobiology, Kings College London, New Hunts House, Guys Hospital Campus, London, SE1 1UL, UK; MRC Centre for Neurodevelopmental Disorders, Kings College London, New Hunts House, Guys Hospital Campus, London, SE1 1UL, UK.
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9
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Walker AS, Neves G, Grillo F, Jackson RE, Rigby M, O'Donnell C, Lowe AS, Vizcay-Barrena G, Fleck RA, Burrone J. Distance-dependent gradient in NMDAR-driven spine calcium signals along tapering dendrites. Proc Natl Acad Sci U S A 2017; 114:E1986-E1995. [PMID: 28209776 PMCID: PMC5347575 DOI: 10.1073/pnas.1607462114] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Neurons receive a multitude of synaptic inputs along their dendritic arbor, but how this highly heterogeneous population of synaptic compartments is spatially organized remains unclear. By measuring N-methyl-d-aspartic acid receptor (NMDAR)-driven calcium responses in single spines, we provide a spatial map of synaptic calcium signals along dendritic arbors of hippocampal neurons and relate this to measures of synapse structure. We find that quantal NMDAR calcium signals increase in amplitude as they approach a thinning dendritic tip end. Based on a compartmental model of spine calcium dynamics, we propose that this biased distribution in calcium signals is governed by a gradual, distance-dependent decline in spine size, which we visualized using serial block-face scanning electron microscopy. Our data describe a cell-autonomous feature of principal neurons, where tapering dendrites show an inverse distribution of spine size and NMDAR-driven calcium signals along dendritic trees, with important implications for synaptic plasticity rules and spine function.
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Affiliation(s)
- Alison S Walker
- Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, United Kingdom
| | - Guilherme Neves
- Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, United Kingdom
| | - Federico Grillo
- Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, United Kingdom
| | - Rachel E Jackson
- Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, United Kingdom
| | - Mark Rigby
- Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, United Kingdom
| | - Cian O'Donnell
- Department of Computer Science, University of Bristol, Bristol BS8 1UB, United Kingdom
| | - Andrew S Lowe
- Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, United Kingdom
| | - Gema Vizcay-Barrena
- Centre for Ultrastructural Imaging, Kings College London, London SE1 1UL, United Kingdom
| | - Roland A Fleck
- Centre for Ultrastructural Imaging, Kings College London, London SE1 1UL, United Kingdom
| | - Juan Burrone
- Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, United Kingdom;
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10
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Neves G, Shah MM, Liodis P, Achimastou A, Denaxa M, Roalfe G, Sesay A, Walker MC, Pachnis V. The LIM homeodomain protein Lhx6 regulates maturation of interneurons and network excitability in the mammalian cortex. ACTA ACUST UNITED AC 2012; 23:1811-23. [PMID: 22710612 PMCID: PMC3698365 DOI: 10.1093/cercor/bhs159] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Deletion of LIM homeodomain transcription factor-encoding Lhx6 gene in mice results in defective tangential migration of cortical interneurons and failure of differentiation of the somatostatin (Sst)- and parvalbumin (Pva)-expressing subtypes. Here, we characterize a novel hypomorphic allele of Lhx6 and demonstrate that reduced activity of this locus leads to widespread differentiation defects in Sst(+) interneurons, but relatively minor and localized changes in Pva(+) interneurons. The reduction in the number of Sst-expressing cells was not associated with a loss of interneurons, because the migration and number of Lhx6-expressing interneurons and expression of characteristic molecular markers, such as calretinin or Neuropeptide Y, were not affected in Lhx6 hypomorphic mice. Consistent with a selective deficit in the differentiation of Sst(+) interneurons in the CA1 subfield of the hippocampus, we observed reduced expression of metabotropic Glutamate Receptor 1 in the stratum oriens and characteristic changes in dendritic inhibition, but normal inhibitory input onto the somatic compartment of CA1 pyramidal cells. Moreover, Lhx6 hypomorphs show behavioral, histological, and electroencephalographic signs of recurrent seizure activity, starting from early adulthood. These results demonstrate that Lhx6 plays an important role in the maturation of cortical interneurons and the formation of inhibitory circuits in the mammalian cortex.
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Affiliation(s)
- Guilherme Neves
- Division of Molecular Neurobiology, MRC National Institute for Medical Research, London, UK
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11
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Yonekura S, Ting CY, Neves G, Hung K, Hsu SN, Chiba A, Chess A, Lee CH. The variable transmembrane domain of Drosophila N-cadherin regulates adhesive activity. Mol Cell Biol 2006; 26:6598-608. [PMID: 16914742 PMCID: PMC1592838 DOI: 10.1128/mcb.00241-06] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Drosophila N-cadherin (CadN) is an evolutionarily conserved classic cadherin which has a large, complex extracellular domain and a catenin-binding cytoplasmic domain. The CadN locus contains three modules of alternative exons (7a/b, 13a/b, and 18a/b) and undergoes alternative splicing to generate multiple isoforms. Using quantitative transcript analyses and green fluorescent protein-based cell sorting, we found that during development CadN alternative splicing is regulated in a temporal but not cell-type-specific fashion. In particular, exon 18b is predominantly expressed during early developmental stages, while exon 18a is prevalent at the late developmental and adult stages. All CadN isoforms share the same molecular architecture but have different sequences in their extracellular and transmembrane domains, suggesting functional diversity. In vitro quantitative cell aggregation assays revealed that all CadN isoforms mediate homophilic interactions, but the isoforms encoded by exon 18b have a higher adhesive activity than those by its alternative, 18a. Domain-swapping experiments further revealed that the different sequences in the transmembrane domains of isoforms are responsible for their differential adhesive activities. CadN alternative splicing might provide a novel mechanism to fine-tune its adhesive activity at different developmental stages or to restrict the use of high-affinity 18b-type isoforms at the adult stage.
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Affiliation(s)
- Shinichi Yonekura
- Unit of Neuronal Connectivity, Laboratory of Gene Regulation and Development, National Institute of Child Health and Human Development, National Institutes of Health, Building 18T, Room 106, MSC 5431, Bethesda, MD 20892, USA
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12
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Affiliation(s)
- G Neves
- Center for Human Genetic Research, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, and Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, USA
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13
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Zhan XL, Clemens JC, Neves G, Hattori D, Flanagan JJ, Hummel T, Vasconcelos ML, Chess A, Zipursky SL. Analysis of Dscam diversity in regulating axon guidance in Drosophila mushroom bodies. Neuron 2004; 43:673-86. [PMID: 15339649 DOI: 10.1016/j.neuron.2004.07.020] [Citation(s) in RCA: 151] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2004] [Revised: 05/21/2004] [Accepted: 06/18/2004] [Indexed: 10/25/2022]
Abstract
Dscam is an immunoglobulin (Ig) superfamily member that regulates axon guidance and targeting in Drosophila. Alternative splicing potentially generates 38,016 isoforms differing in their extracellular Ig and transmembrane domains. We demonstrate that Dscam mediates the sorting of axons in the developing mushroom body (MB). This correlates with the precise spatiotemporal pattern of Dscam protein expression. We demonstrate that MB neurons express different arrays of Dscam isoforms and that single MB neurons express multiple isoforms. Two different Dscam isoforms differing in their extracellular domains introduced as transgenes into single mutant cells partially rescued the mutant phenotype. Expression of one isoform of Dscam in a cohort of MB neurons induced dominant phenotypes, while expression of a single isoform in a single cell did not. We propose that different extracellular domains of Dscam share a common function and that differences in isoforms expressed on the surface of neighboring axons influence interactions between them.
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Affiliation(s)
- Xiao-Li Zhan
- Howard Hughes Medical Institute, Department of Biological Chemistry, The David Geffen School of Medicine, University of California, Los Angeles, 90095, USA
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14
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Neves G, Zucker J, Daly M, Chess A. Stochastic yet biased expression of multiple Dscam splice variants by individual cells. Nat Genet 2004; 36:240-6. [PMID: 14758360 DOI: 10.1038/ng1299] [Citation(s) in RCA: 191] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2003] [Accepted: 01/02/2004] [Indexed: 11/08/2022]
Abstract
The Drosophila melanogaster gene Dscam is essential for axon guidance and has 38,016 possible alternative splice forms. This diversity can potentially be used to distinguish cells. We analyzed the Dscam mRNA isoforms expressed by different cell types and individual cells. The choice of splice variants expressed is regulated both spatially and temporally. Different subtypes of photoreceptors express broad yet distinctive spectra of Dscam isoforms. Single-cell RT-PCR documented that individual cells express several different Dscam isoforms and allowed an estimation of the diversity that is present. For example, we estimate that each R3/R4 photoreceptor cell expresses 14-50 distinct mRNAs chosen from the spectrum of thousands of splice variants distinctive of its cell type. Thus, the Dscam repertoire of each cell is different from those of its neighbors, providing a potential mechanism for generating unique cell identity in the nervous system and elsewhere.
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Affiliation(s)
- Guilherme Neves
- Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, Massachusetts 02142, USA
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15
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Tasso L, Neves G, Menegatti R, Fraga CAM, Barreiro EJ, Eifler-Lima VL, Rates SMK, Dalla Costa T. Validated HPLC method for determination of LASSBio-581, a new heterocyclic N-phenylpiperazine derivative, in rat plasma. J Pharm Biomed Anal 2003; 33:1127-33. [PMID: 14656603 DOI: 10.1016/s0731-7085(03)00407-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A rapid, simple and accurate high performance liquid chromatography (HPLC) method was developed and validated for the determination of LASSBio-581 (1-[1-(4-chloro-phenyl)-1H-[1,2,3]triazol-4-ylmethyl]-4-phenyl-piperazine) in rat plasma using ketoconazole as internal standard. Plasma samples were deproteinized with methanol. A good chromatographic separation was achieved using a reversed phase C18 column. Mobile phase consisting of sodium dihydrogen phosphate monohydrate (pH 4.5, 0.02 M) and methanol mixture (35:65, v/v) was used at a flow rate of 1.0 ml/min. The eluate was monitored using a UV detector at 248 nm. The retention times of LASSBio-581 and the internal standard were approximately 3.8 and 5.6 min, respectively. The calibration curves were linear over the concentration range of 0.25-8.0 microg/ml with correlation coefficients >0.99. The limit of quantitation was 0.25 microg/ml. The accuracy of the method was >90%. The intra-day relative standard deviation (R.S.D.) ranged from 6.15 to 10.52% at 0.4 microg/ml, 7.44 to 13.81% at 1.5 microg/ml and 6.10 to 13.94% at 6.0 microg/ml. The inter-day R.S.D. were 9.54, 8.42 and 8.25% at 0.4, 1.5 and 6.0 microg/ml, respectively. No interference from endogenous substances or metabolites were observed. The method has been used to measure plasma concentrations of LASSBio-581 in pharmacokinetic studies in rats.
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Affiliation(s)
- L Tasso
- Programa de Pós-Graduação em Ciências Farmacêuticas, Faculdade de Farmácia, Universidade Federal do Rio Grande do Sul (UFRGS), Av. Ipiranga, 2752, Porto Alegre, RS 90610-000, Brazil
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16
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Neves G, Fenner R, Heckler AP, Viana AF, Tasso L, Menegatti R, Fraga CAM, Barreiro EJ, Dalla-Costa T, Rates SMK. Dopaminergic profile of new heterocyclic N-phenylpiperazine derivatives. Braz J Med Biol Res 2003; 36:625-9. [PMID: 12715082 DOI: 10.1590/s0100-879x2003000500010] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Dopamine constitutes about 80% of the content of central catecholamines and has a crucial role in the etiology of several neuropsychiatric disorders, including Parkinson's disease, depression and schizophrenia. Several dopaminergic drugs are used to treat these pathologies, but many problems are attributed to these therapies. Within this context, the search for new more efficient dopaminergic agents with less adverse effects represents a vast research field. The aim of the present study was to report the structural design of two N-phenylpiperazine derivatives, compound 4: 1-[1-(4-chlorophenyl)-1H-4-pyrazolylmethyl]-4-phenylhexahydropyrazine and compound 5: 1-[1-(4-chlorophenyl)-1H-1,2,3-triazol-4-ylmethyl]-4-phenylhexahydropyrazine, planned to be dopamine ligands, and their dopaminergic action profile. The two compounds were assayed (dose range of 15-40 mg/kg) in three experimental models: 1) blockade of amphetamine (30 mg/kg, ip)-induced stereotypy in rats; 2) the catalepsy test in mice, and 3) apomorphine (1 mg/kg, ip)-induced hypothermia in mice. Both derivatives induced cataleptic behavior (40 mg/kg, ip) and a hypothermic response (30 mg/kg, ip) which was not prevented by haloperidol (0.5 mg/kg, ip). Compound 5 (30 mg/kg, ip) also presented a synergistic hypothermic effect with apomorphine (1 mg/kg, ip). Only compound 4 (30 mg/kg, ip) significantly blocked the amphetamine-induced stereotypy in rats. The N-phenylpiperazine derivatives 4 and 5 seem to have a peculiar profile of action on dopaminergic functions. On the basis of the results of catalepsy and amphetamine-induced stereotypy, the compounds demonstrated an inhibitory effect on dopaminergic behaviors. However, their hypothermic effect is compatible with the stimulation of dopaminergic function which seems not to be mediated by D2/D3 receptors.
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Affiliation(s)
- G Neves
- Laborat rio de Psicofarmacologia, Departamento de Produ o de Mat ria-Prima, Faculdade de Farm cia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil
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17
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Abstract
To describe early symptomatic and late seizures in a cohort of patients with acute cerebral vein and dural sinus thrombosis (CVDST) and to identify their determinants, we performed a prospective registry and follow-up study of CVDST patients admitted to 20 Portuguese hospitals, from June 1995 to June 1998. Of 91 registered patients, 31 (34%) had early symptomatic seizures; 29 (31.9%) as a presenting feature and 2 (2.1%) after admission. Early symptomatic seizures were more frequent in patients with motor and sensory deficits and in those with focal oedema/ischaemic infarcts or haemorrhages on admission CT/MR. On multivariate logistic regression analysis, sensory defects (OR = 7.8; 95% CI = 0.8-74.8) and a parenchymal lesion on admission CT/MR (OR = 3.7, 95% CI = 1.4-9.4) were found to be significant predictors of early symptomatic seizures. Seizures were directly related to acute death in 2 patients. Eight (9.5%) patients had late seizures, which were multiple in 4 (4.8%). Late seizures were more frequent in patients with early symptomatic seizures and with haemorrhage on admission CT/MR. Neither early symptomatic seizures nor late seizures were related to functional prognosis at the last follow-up (median = 1 year). There is a moderate risk of seizure recurrence early in the course and during the first year after CVDST. Seizures can be a cause of acute death, but might not have an independent influence on functional outcome. Pharmacological prevention of seizures after CVDST should probably be limited to patients with early symptomatic seizures and cerebral lesions on admission CT/MR.
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Affiliation(s)
- J M Ferro
- Department of Neurology, Hospital de Santa Maria, Lisboa, Portugal.
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18
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Abstract
Calcium-triggered exocytosis at the synapse is suppressed by addition of calcium chelators, but the effects of endogenous Ca(2+) buffers have not been tested. We find that 80% of Ca(2+) binding sites in the synaptic terminal of retinal bipolar cells were associated with mobile molecules that suppressed activation of Ca(2+)-sensitive K(+) channels with an efficiency equivalent to approximately 1.2 mM BAPTA. Removing these buffers caused a 30-fold increase in the number of vesicles released by Ca(2+) tail currents lasting approximately 0.5 ms and a 2-fold increase in the rapidly releasable pool of vesicles (RRP). The effects of BAPTA and EGTA indicate that vesicles comprising the RRP were docked at variable distances from Ca(2+) channels. We propose that endogenous Ca(2+) buffers regulate the size of the RRP by suppressing the release of vesicles toward the periphery of the active zone.
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Affiliation(s)
- Juan Burrone
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, United Kingdom
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19
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Neves G, Gomis A, Lagnado L. Calcium influx selects the fast mode of endocytosis in the synaptic terminal of retinal bipolar cells. Proc Natl Acad Sci U S A 2001; 98:15282-7. [PMID: 11734626 PMCID: PMC65021 DOI: 10.1073/pnas.261311698] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2001] [Indexed: 11/18/2022] Open
Abstract
To investigate the regulation of endocytosis by Ca(2+), we have made capacitance measurements in the synaptic terminal of depolarizing bipolar cells from the retina of goldfish. After a brief depolarization, all of the excess membrane was retrieved rapidly (tau approximately 1 s). But when the rise in free [Ca(2+)] was reduced by the introduction of Ca(2+) buffers [1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetate (BAPTA) or EGTA], a large fraction of the membrane was retrieved by a second, slower mechanism (tau > or = 10 s). The block of fast endocytosis by EGTA could be overcome by increasing the amplitude of the Ca(2+) current, demonstrating that Ca(2+) influx was the trigger for fast endocytosis. These manipulations of the Ca(2+) signal altered the relative proportions of fast and slow endocytosis but did not modulate the rate constants of these processes. A brief stimulus that triggered fast endocytosis did not generate a significant rise in the spatially averaged [Ca(2+)], indicating that Ca(2+) regulated endocytosis through an action close to the active zone. The slow mode of retrieval occurred at the resting [Ca(2+)]. These results demonstrate that Ca(2+) influx couples fast endocytosis and exocytosis at this synapse.
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Affiliation(s)
- G Neves
- Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, United Kingdom
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20
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Abstract
1. We investigated the properties of Ca2+-sensitive steps in the cycling of synaptic vesicles by comparing the actions of Ca2+, Ba2+ and Sr2+ in the synaptic terminal of depolarizing bipolar cells isolated from the retina of goldfish. FM1-43 fluorescence and capacitance measurements demonstrated that exocytosis, endocytosis and vesicle mobilization were maintained when external Ca2+ was replaced by either Ba2+ or Sr2+. 2. The rapidly releasable pool of vesicles (RRP) was equivalent to 1.5 % of the membrane surface area when measured in the presence of 2.5 mM Ca2+, but only 0.4 % in 2.5 mM Sr2+. The relative sizes of the RRP in Ca2+, Sr2+ and Ba2+ were 1.0, 0.28 and 0.1, respectively. We conclude that a smaller proportion of docked vesicles are available for fast exocytosis triggered by the influx of Sr2+ or Ba2+ compared to Ca2+. 3. The slow phase of exocytosis was not altered when Ca2+ was replaced by Ba2+, but it was accelerated 1.6-fold in Sr2+. The peak concentrations of Ca2+, Sr2+ and Ba2+ (measured using Mag-fura-5) were approximately 4, approximately 14 and approximately 60 microM, respectively. The order of efficiency for the stimulation of slow exocytosis was Ca2+ approximately Sr2+ > Ba2+. 4. Exocytosis was prolonged after the influx of Sr2+ and Ba2+. Sr2+ was cleared from the synaptic terminal with the same time constant as Ca2+ (1.3 s), but Ba2+ was cleared 10-100 times more slowly. Although Ba(2+) stimulates the slow release of a large number of vesicles, it did so less efficiently than Ca2+ or Sr2+. 5. The recovery of the membrane capacitance was equally rapid in Sr2+ and Ca2+, demonstrating that the fast mode of endocytosis could be triggered by either cation.
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Affiliation(s)
- G Neves
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK
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21
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Abstract
Ganglion cells convey information from the retina back to the brain. Recent experiments have examined how ganglion cell receptive fields are assembled from many incoming signals.
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Affiliation(s)
- G Neves
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK
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Daudt R, Neves G, Rates SM. R. Daudt, G. L. Von poser, G. Neves and S. M. K. Rates, 'Screening for the antidepressant activity of some species of hypericum from south Brazil'. Phytotherapy research14(5) 2000, 344-346. Phytother Res 2000; 14:661. [PMID: 11114012 DOI: 10.1002/1099-1573(200012)14:8<661::aid-ptr806>3.0.co;2-v] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The original article to which this Erratum refers was published in Phytotherapy Research 14(5) 2000, 344-346. Following the publication of this paper in the August 2000 issue of Phytotherapy Research (14(5):344-346), it has come to our attention that there is a misleading statement regarding conclusions cited from the work of Butterweck et al. 1998. The discussion in the recent PTR paper states that those authors are 'in favour of the hypothesis that the antidepressant activity is due to the hypericin only'. We wish to make it clear that this is not the case, and the Butterweck paper actually concludes that 'both naphthodianthrones must be considered as active constituents of the crude extract of H. perforatum. However, previous studies indicate that the other consitutuents of the crude drug also have activity'. The authors apologize for this error and are happy to correct it.
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de-Paris F, Neves G, Salgueiro JB, Quevedo J, Izquierdo I, Rates SM. Psychopharmacological screening of Pfaffia glomerata Spreng. (Amarathanceae) in rodents. J Ethnopharmacol 2000; 73:261-269. [PMID: 11025164 DOI: 10.1016/s0378-8741(00)00329-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The alcoholic extract of Pfaffia glomerata roots (100, 500, 1000 mg/kg, intraperitoneally (i.p.), and 500, 1000, 1500 mg/kg, per os) was studied in several behavioral animal models for the evaluation of central activity: open field, barbiturate sleeping time, pentilenotetrazole (PTZ)-induced convulsions, elevated plus-maze, step-down inhibitory avoidance and forced swimming test. The acute treatment (500 mg/kg, i.p.) interfered with the open-field habituation, decreased sleep latency and increased barbiturate-induced sleeping time, protected partially the animals of PTZ-induced convulsions, decreased the memory retention in step-down inhibitory avoidance, and did not have an important effect in the elevated plus-maze test and forced swimming test. The same extract at 1000 mg/kg per os did not cause any effect in barbiturate sleeping time and pentilenotetrazole-induced convulsions models. Thus, the effect on the memory was deeper evaluated in the step-down inhibitory avoidance task. When administered by intraperitoneal route, the extract showed a dose-dependent effect causing full amnesia at 1000 mg/kg. On the other hand, when it was given by oral route at 500, 1000 and 1500 mg/kg, no influence on the memory retention was observed. These results suggest that the alcoholic extract of P. glomerata roots presents different effects depending on the route of administration: by i.p route, it seems to be a central nervous system depressant agent; by oral route, it seems to be ineffective, at least in the tested doses.
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Affiliation(s)
- F de-Paris
- Centro de Memória, Departamento de Bioquímica, Instituto de Ci encias Básicas da Saúde (ICBS), Universidade Federal do Rio Grande do Sul (UFRGS), RS, Porto Alegre, Brazil
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Abstract
The crude methanol extracts of three species of the genus Hypericum (H. brasiliense, H. caprifoliatum and H. myrianthum) native to South Brazil were evaluated for the antidepressant activity according to the forced swimming test, a classical animal model for antidepressant drug screening. Among the species studied, only H. caprifoliatum showed activity. Thus, this plant was fractionated with solvents in increasing polarity (petroleum ether; petroleum ether: chloroform (1:1); chloroform and methanol). The petroleum ether fraction was the only one which demonstrated antidepressant activity at a dose of 270 mg/kg/day (i.p.). The chemical analyses showed that this fraction is rich in phenolic compounds, mainly of the phloroglucinol type.
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Affiliation(s)
- R Daudt
- Núcleo de Farmacologia - Laboratório de Farmacognosia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
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25
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Affiliation(s)
- G Neves
- MRC Laboratory of Molecular Biology Hills Road, Cambridge, CB2 2QH, UK
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26
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Abstract
1. The kinetics of exocytosis and endocytosis were studied in the giant synaptic terminal of depolarizing bipolar cells from the goldfish retina. Two techniques were applied: capacitance measurements of changes in membrane surface area, and fluorescence measurements of exocytosis using the membrane dye FM1-43. 2. Three phases of exocytosis occurred during maintained depolarization to 0 mV. The first component was complete within about 10 ms and involved a pool of 1200-1800 vesicles (with a total membrane area equivalent to about 1.6 % of the surface of the terminal). The second component of exocytosis involved the release of about 4400 vesicles over 1 s. The third component of exocytosis was stimulated continuously at a rate of about 1000 vesicles s-1. 3. After short depolarizations (< 200 ms), neither the FM1-43 signal nor the capacitance signal continued to rise, indicating that exocytosis stopped rapidly after closure of Ca2+ channels. The fall in capacitance could therefore be used to monitor endocytosis independently of exocytosis. The capacitance measured after brief stimuli began to fall immediately, recovering to the pre-stimulus baseline with a rate constant of 0.8 s-1. 4. The amount of exocytosis measured using the capacitance and FM1-43 techniques was similar during the first 200 ms of depolarization, suggesting that the most rapidly released vesicles could be detected by either method. 5. After a few seconds of continuous stimulation, the net increase in membrane surface area reached a plateau at about 5 %, even though continuous exocytosis occurred at a rate of 0.9 % s-1. Under these conditions of balanced exocytosis and endocytosis, the rate constant of endocytosis was about 0.2 s-1. The average rate of endocytosis during maintained depolarization was therefore considerably slower than the rate observed after a brief stimulus. 6. After longer depolarizations (> 500 ms), both the capacitance and FM1-43 signals continued to rise for periods of seconds after closure of Ca2+ channels. The continuation of exocytosis was correlated with a persistent increase in [Ca2+]i in the synaptic terminal, as indicated by the activation of a Ca2+-dependent conductance and measurements of [Ca2+]i using the fluorescent indicator furaptra. 7. The delayed fall in membrane capacitance after longer depolarizations occurred along a double exponential time course indicating the existence of two endocytic processes: fast endocytosis, with a rate constant of 0.8 s-1, and slow endocytosis, with a rate constant of 0.1 s-1. 8. Increasing the duration of depolarization caused an increase in the fraction of membrane recovered by slow endocytosis. After a 100 ms stimulus, all the membrane was recycled by fast endocytosis, but after a 5 s depolarization, about 50 % of the membrane was recycled by slow endocytosis. 9. These results demonstrate the existence of fast and slow endocytic mechanisms at a synapse and support the idea that prolonged stimulation leads to an increase in the amount of membrane retrieved by the slower route. The rise in cytoplasmic Ca2+ that occurred during longer depolarizations was correlated with stimulation of continuous exocytosis and inhibition of fast endocytosis. The results also confirm that transient and continuous components of exocytosis coexist in the synaptic terminal of depolarizing bipolar cells.
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Affiliation(s)
- G Neves
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK
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Abstract
Twenty one patients with idiopathic Parkinsonism beginning before the age of 40 years were investigated. The mean duration of the disease was 19 years. There was a good and sustained response to levodopa. Only four patients reached stages IV and V (Hoehn and Yahr). Intolerance to levodopa was observed in the more advanced stages of the disease. In the series the familial incidence of Parkinsonism (2 cases) and essential tremor (3 cases) was very low. Thyroid disorder, diabetes mellitus or macrocytic anaemia was not found in any of the cases.
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