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Griesius S, O'Donnell C, Waldron S, Thomas KL, Dwyer DM, Wilkinson LS, Hall J, Robinson ESJ, Mellor JR. Correction: Reduced expression of the psychiatric risk gene DLG2 (PSD93) impairs hippocampal synaptic integration and plasticity. Neuropsychopharmacology 2024; 49:766. [PMID: 38225398 PMCID: PMC10876557 DOI: 10.1038/s41386-024-01801-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2024]
Affiliation(s)
- Simonas Griesius
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Cian O'Donnell
- Computational Neuroscience Unit, School of Computer Science, Electrical and Electronic Engineering, and Engineering Mathematics, University of Bristol, Bristol, BS8 1UB, UK
| | - Sophie Waldron
- Neuroscience and Mental Health Research Institute, Cardiff, CF24 4HQ, UK
- School of Psychology, Cardiff, CF24 4HQ, UK
| | - Kerrie L Thomas
- Neuroscience and Mental Health Research Institute, Cardiff, CF24 4HQ, UK
- School of Medicine, Cardiff, CF24 4HQ, UK
| | - Dominic M Dwyer
- Neuroscience and Mental Health Research Institute, Cardiff, CF24 4HQ, UK
- School of Psychology, Cardiff, CF24 4HQ, UK
| | - Lawrence S Wilkinson
- Neuroscience and Mental Health Research Institute, Cardiff, CF24 4HQ, UK
- School of Psychology, Cardiff, CF24 4HQ, UK
- MRC Centre for Neuropsychiatric Genetics and Genomics, Cardiff, CF24 4HQ, UK
| | - Jeremy Hall
- Neuroscience and Mental Health Research Institute, Cardiff, CF24 4HQ, UK
- School of Medicine, Cardiff, CF24 4HQ, UK
- MRC Centre for Neuropsychiatric Genetics and Genomics, Cardiff, CF24 4HQ, UK
| | - Emma S J Robinson
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Jack R Mellor
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol, BS8 1TD, UK.
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2
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Griesius S, Waldron S, Kamenish KA, Cherbanich N, Wilkinson LS, Thomas KL, Hall J, Mellor JR, Dwyer DM, Robinson ESJ. A mild impairment in reversal learning in a bowl-digging substrate deterministic task but not other cognitive tests in the Dlg2+/- rat model of genetic risk for psychiatric disorder. Genes Brain Behav 2023; 22:e12865. [PMID: 37705179 PMCID: PMC10733576 DOI: 10.1111/gbb.12865] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 08/22/2023] [Accepted: 08/25/2023] [Indexed: 09/15/2023]
Abstract
Variations in the Dlg2 gene have been linked to increased risk for psychiatric disorders, including schizophrenia, autism spectrum disorders, intellectual disability, bipolar disorder, attention deficit hyperactivity disorder, and pubertal disorders. Recent studies have reported disrupted brain circuit function and behaviour in models of Dlg2 knockout and haploinsufficiency. Specifically, deficits in hippocampal synaptic plasticity were found in heterozygous Dlg2+/- rats suggesting impacts on hippocampal dependent learning and cognitive flexibility. Here, we tested these predicted effects with a behavioural characterisation of the heterozygous Dlg2+/- rat model. Dlg2+/- rats exhibited a specific, mild impairment in reversal learning in a substrate deterministic bowl-digging reversal learning task. The performance of Dlg2+/- rats in other bowl digging task, visual discrimination and reversal, novel object preference, novel location preference, spontaneous alternation, modified progressive ratio, and novelty-suppressed feeding test were not impaired. These findings suggest that despite altered brain circuit function, behaviour across different domains is relatively intact in Dlg2+/- rats, with the deficits being specific to only one test of cognitive flexibility. The specific behavioural phenotype seen in this Dlg2+/- model may capture features of the clinical presentation associated with variation in the Dlg2 gene.
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Affiliation(s)
- Simonas Griesius
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University WalkBristolUK
| | - Sophie Waldron
- Neuroscience and Mental Health Research Institute, PsychologyCardiffUK
- Department of PsychologyCardiffUK
| | - Katie A. Kamenish
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University WalkBristolUK
| | - Nick Cherbanich
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University WalkBristolUK
| | - Lawrence S. Wilkinson
- Neuroscience and Mental Health Research Institute, PsychologyCardiffUK
- Department of PsychologyCardiffUK
- MRC Centre for Neuropsychiatric Genetics and Genomics, Schools of Medicine and Genetics and Genomics, Schools of Medicine and PsychologyCardiffUK
| | - Kerrie L. Thomas
- Neuroscience and Mental Health Research Institute, PsychologyCardiffUK
- Department of Medicine and PsychologyCardiffUK
| | - Jeremy Hall
- Neuroscience and Mental Health Research Institute, PsychologyCardiffUK
- MRC Centre for Neuropsychiatric Genetics and Genomics, Schools of Medicine and Genetics and Genomics, Schools of Medicine and PsychologyCardiffUK
- Department of Medicine and PsychologyCardiffUK
| | - Jack R. Mellor
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University WalkBristolUK
| | - Dominic M. Dwyer
- Neuroscience and Mental Health Research Institute, PsychologyCardiffUK
- Department of PsychologyCardiffUK
| | - Emma S. J. Robinson
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University WalkBristolUK
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Al-Amri AH, Armstrong P, Amici M, Ligneul C, Rouse J, El-Asrag ME, Pantiru A, Vancollie VE, Ng HW, Ogbeta JA, Goodchild K, Ellegood J, Lelliott CJ, Mullins JG, Bretman A, Al-Ali R, Beetz C, Al-Gazali L, Al Shamsi A, Lerch JP, Mellor JR, Al Sayegh A, Ali M, Inglehearn CF, Clapcote SJ. PDZD8 Disruption Causes Cognitive Impairment in Humans, Mice, and Fruit Flies. Biol Psychiatry 2022; 92:323-334. [PMID: 35227461 PMCID: PMC9302898 DOI: 10.1016/j.biopsych.2021.12.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 12/13/2021] [Accepted: 12/14/2021] [Indexed: 12/16/2022]
Abstract
BACKGROUND The discovery of coding variants in genes that confer risk of intellectual disability (ID) is an important step toward understanding the pathophysiology of this common developmental disability. METHODS Homozygosity mapping, whole-exome sequencing, and cosegregation analyses were used to identify gene variants responsible for syndromic ID with autistic features in two independent consanguineous families from the Arabian Peninsula. For in vivo functional studies of the implicated gene's function in cognition, Drosophila melanogaster and mice with targeted interference of the orthologous gene were used. Behavioral, electrophysiological, and structural magnetic resonance imaging analyses were conducted for phenotypic testing. RESULTS Homozygous premature termination codons in PDZD8, encoding an endoplasmic reticulum-anchored lipid transfer protein, showed cosegregation with syndromic ID in both families. Drosophila melanogaster with knockdown of the PDZD8 ortholog exhibited impaired long-term courtship-based memory. Mice homozygous for a premature termination codon in Pdzd8 exhibited brain structural, hippocampal spatial memory, and synaptic plasticity deficits. CONCLUSIONS These data demonstrate the involvement of homozygous loss-of-function mutations in PDZD8 in a neurodevelopmental cognitive disorder. Model organisms with manipulation of the orthologous gene replicate aspects of the human phenotype and suggest plausible pathophysiological mechanisms centered on disrupted brain development and synaptic function. These findings are thus consistent with accruing evidence that synaptic defects are a common denominator of ID and other neurodevelopmental conditions.
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Affiliation(s)
- Ahmed H. Al-Amri
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom,Leeds Institute of Medical Research, University of Leeds, Leeds, United Kingdom,National Genetic Centre, Royal Hospital, Muscat, Oman
| | - Paul Armstrong
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Mascia Amici
- School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol, United Kingdom
| | - Clemence Ligneul
- Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neuroscience, University of Oxford, Oxford, United Kingdom
| | - James Rouse
- School of Biology, University of Leeds, Leeds, United Kingdom
| | - Mohammed E. El-Asrag
- Leeds Institute of Medical Research, University of Leeds, Leeds, United Kingdom,Department of Zoology, Faculty of Science, Benha University, Benha, Egypt,Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham
| | - Andreea Pantiru
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | | | - Hannah W.Y. Ng
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Jennifer A. Ogbeta
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Kirstie Goodchild
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Jacob Ellegood
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, Ontario, Canada
| | | | | | - Amanda Bretman
- School of Biology, University of Leeds, Leeds, United Kingdom
| | | | | | - Lihadh Al-Gazali
- Department of Paediatrics, College of Medicine & Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Aisha Al Shamsi
- Pediatrics Department, Tawam Hospital, Al Ain, United Arab Emirates
| | - Jason P. Lerch
- Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neuroscience, University of Oxford, Oxford, United Kingdom
| | - Jack R. Mellor
- School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol, United Kingdom
| | - Abeer Al Sayegh
- Genetics Department, Sultan Qaboos University Hospital, Muscat, Oman
| | - Manir Ali
- Leeds Institute of Medical Research, University of Leeds, Leeds, United Kingdom
| | - Chris F. Inglehearn
- Leeds Institute of Medical Research, University of Leeds, Leeds, United Kingdom
| | - Steven J. Clapcote
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom,Address correspondence to Steven J. Clapcote, Ph.D.
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4
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Griesius S, O'Donnell C, Waldron S, Thomas KL, Dwyer DM, Wilkinson LS, Hall J, Robinson ESJ, Mellor JR. Reduced expression of the psychiatric risk gene DLG2 (PSD93) impairs hippocampal synaptic integration and plasticity. Neuropsychopharmacology 2022; 47:1367-1378. [PMID: 35115661 PMCID: PMC9117295 DOI: 10.1038/s41386-022-01277-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 01/04/2022] [Accepted: 01/12/2022] [Indexed: 11/15/2022]
Abstract
Copy number variants indicating loss of function in the DLG2 gene have been associated with markedly increased risk for schizophrenia, autism spectrum disorder, and intellectual disability. DLG2 encodes the postsynaptic scaffolding protein DLG2 (PSD93) that interacts with NMDA receptors, potassium channels, and cytoskeletal regulators but the net impact of these interactions on synaptic plasticity, likely underpinning cognitive impairments associated with these conditions, remains unclear. Here, hippocampal CA1 neuronal excitability and synaptic function were investigated in a novel clinically relevant heterozygous Dlg2+/- rat model using ex vivo patch-clamp electrophysiology, pharmacology, and computational modelling. Dlg2+/- rats had reduced supra-linear dendritic integration of synaptic inputs resulting in impaired associative long-term potentiation. This impairment was not caused by a change in synaptic input since NMDA receptor-mediated synaptic currents were, conversely, increased and AMPA receptor-mediated currents were unaffected. Instead, the impairment in associative long-term potentiation resulted from an increase in potassium channel function leading to a decrease in input resistance, which reduced supra-linear dendritic integration. Enhancement of dendritic excitability by blockade of potassium channels or activation of muscarinic M1 receptors with selective allosteric agonist 77-LH-28-1 reduced the threshold for dendritic integration and 77-LH-28-1 rescued the associative long-term potentiation impairment in the Dlg2+/- rats. These findings demonstrate a biological phenotype that can be reversed by compound classes used clinically, such as muscarinic M1 receptor agonists, and is therefore a potential target for therapeutic intervention.
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Affiliation(s)
- Simonas Griesius
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Cian O'Donnell
- Computational Neuroscience Unit, School of Computer Science, Electrical and Electronic Engineering, and Engineering Mathematics, University of Bristol, Bristol, BS8 1UB, UK
| | - Sophie Waldron
- Neuroscience and Mental Health Research Institute, Cardiff, CF24 4HQ, UK
- School of Psychology, Cardiff, CF24 4HQ, UK
| | - Kerrie L Thomas
- Neuroscience and Mental Health Research Institute, Cardiff, CF24 4HQ, UK
- School of Medicine, Cardiff, CF24 4HQ, UK
| | - Dominic M Dwyer
- Neuroscience and Mental Health Research Institute, Cardiff, CF24 4HQ, UK
- School of Psychology, Cardiff, CF24 4HQ, UK
| | - Lawrence S Wilkinson
- Neuroscience and Mental Health Research Institute, Cardiff, CF24 4HQ, UK
- School of Psychology, Cardiff, CF24 4HQ, UK
- MRC Centre for Neuropsychiatric Genetics and Genomics, Cardiff, CF24 4HQ, UK
| | - Jeremy Hall
- Neuroscience and Mental Health Research Institute, Cardiff, CF24 4HQ, UK
- School of Medicine, Cardiff, CF24 4HQ, UK
- MRC Centre for Neuropsychiatric Genetics and Genomics, Cardiff, CF24 4HQ, UK
| | - Emma S J Robinson
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Jack R Mellor
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol, BS8 1TD, UK.
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5
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Waldron S, Pass R, Griesius S, Mellor JR, Robinson ESJ, Thomas KL, Wilkinson LS, Humby T, Hall J, Dwyer DM. Behavioural and molecular characterisation of the Dlg2 haploinsufficiency rat model of genetic risk for psychiatric disorder. Genes Brain Behav 2022; 21:e12797. [PMID: 35075790 PMCID: PMC9393932 DOI: 10.1111/gbb.12797] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [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] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 01/13/2022] [Accepted: 01/13/2022] [Indexed: 11/28/2022]
Abstract
Genetic studies implicate disruption to the DLG2 gene in copy number variants as increasing risk for schizophrenia, autism spectrum disorders and intellectual disability. To investigate psychiatric endophenotypes associated with DLG2 haploinsufficiency (and concomitant PSD-93 protein reduction) a novel clinically relevant Dlg2+/- rat was assessed for abnormalities in anxiety, sensorimotor gating, hedonic reactions, social behaviour, and locomotor response to the N-Methyl-D-aspartic acid receptor antagonist phencyclidine. Dlg gene and protein expression were also investigated to assess model validity. Reductions in PSD-93 messenger RNA and protein were observed in the absence of compensation by other related genes or proteins. Behaviourally Dlg2+/- rats show a potentiated locomotor response to phencyclidine, as is typical of psychotic disorder models, in the absence of deficits in the other behavioural phenotypes assessed here. This shows that the behavioural effects of Dlg2 haploinsufficiency may specifically relate to psychosis vulnerability but are subtle, and partially dissimilar to behavioural deficits previously reported in Dlg2+/- mouse models demonstrating issues surrounding the comparison of models with different aetiology and species. Intact performance on many of the behavioural domains assessed here, such as anxiety and reward processing, will remove these as confounds when continuing investigation into this model using more complex cognitive tasks.
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Affiliation(s)
| | - Rachel Pass
- Neuroscience and Mental Health Research InstituteCardiff UniversityCardiffUK
- Neurobiology Research UnitOkinawa Institute of Science and TechnologyOnna‐sonOkinawaJapan
| | - Simonas Griesius
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and NeuroscienceUniversity of Bristol, University WalkBristolUK
| | - Jack R. Mellor
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and NeuroscienceUniversity of Bristol, University WalkBristolUK
| | - Emma S. J. Robinson
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and NeuroscienceUniversity of Bristol, University WalkBristolUK
| | - Kerrie L. Thomas
- Neuroscience and Mental Health Research InstituteCardiff UniversityCardiffUK
| | - Lawrence S. Wilkinson
- School of PsychologyCardiff UniversityCardiffUK
- Neuroscience and Mental Health Research InstituteCardiff UniversityCardiffUK
| | | | - Jeremy Hall
- Neuroscience and Mental Health Research InstituteCardiff UniversityCardiffUK
- Medical Research Council Centre for Neuropsychiatric Genetics and GenomicsCardiff UniversityCardiffUK
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6
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Palacios-Filardo J, Udakis M, Brown GA, Tehan BG, Congreve MS, Nathan PJ, Brown AJH, Mellor JR. Author Correction: Acetylcholine prioritises direct synaptic inputs from entorhinal cortex to CA1 by differential modulation of feedforward inhibitory circuits. Nat Commun 2021; 12:7265. [PMID: 34880229 PMCID: PMC8654943 DOI: 10.1038/s41467-021-27351-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Affiliation(s)
- Jon Palacios-Filardo
- Center for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol, UK
| | - Matt Udakis
- Center for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol, UK
| | - Giles A Brown
- Sosei Heptares, Steinmetz Building, Granta Park, Great Abingdon, Cambridge, UK.,OMass Therapeutics Ltd, The Schrödinger Building, Oxford, UK
| | - Benjamin G Tehan
- Sosei Heptares, Steinmetz Building, Granta Park, Great Abingdon, Cambridge, UK.,OMass Therapeutics Ltd, The Schrödinger Building, Oxford, UK
| | - Miles S Congreve
- Sosei Heptares, Steinmetz Building, Granta Park, Great Abingdon, Cambridge, UK
| | - Pradeep J Nathan
- Department of Psychiatry, University of Cambridge, Cambridge, UK
| | - Alastair J H Brown
- Sosei Heptares, Steinmetz Building, Granta Park, Great Abingdon, Cambridge, UK
| | - Jack R Mellor
- Center for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol, UK.
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7
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Humphries R, Mellor JR, O'Donnell C. Acetylcholine Boosts Dendritic NMDA Spikes in a CA3 Pyramidal Neuron Model. Neuroscience 2021; 489:69-83. [PMID: 34780920 DOI: 10.1016/j.neuroscience.2021.11.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 10/12/2021] [Accepted: 11/05/2021] [Indexed: 11/25/2022]
Abstract
Acetylcholine has been proposed to facilitate the formation of memory ensembles within the hippocampal CA3 network, by enhancing plasticity at CA3-CA3 recurrent synapses. Regenerative NMDA receptor (NMDAR) activation in CA3 neuron dendrites (NMDA spikes) increase synaptic Ca2+ influx and can trigger this synaptic plasticity. Acetylcholine inhibits potassium channels which enhances dendritic excitability and therefore could facilitate NMDA spike generation. Here, we investigate NMDAR-mediated nonlinear synaptic integration in stratum radiatum (SR) and stratum lacunosum moleculare (SLM) dendrites in a reconstructed CA3 neuron computational model and study the effect of cholinergic inhibition of potassium conductances on this nonlinearity. We found that distal SLM dendrites, with a higher input resistance, had a lower threshold for NMDA spike generation compared to SR dendrites. Simulating acetylcholine by blocking potassium channels (M-type, A-type, Ca2+-activated, and inwardly-rectifying) increased dendritic excitability and reduced the number of synapses required to generate NMDA spikes, particularly in the SR dendrites. The magnitude of this effect was heterogeneous across different dendritic branches within the same neuron. These results predict that acetylcholine facilitates dendritic integration and NMDA spike generation in selected CA3 dendrites which could strengthen connections between specific CA3 neurons to form memory ensembles.
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Affiliation(s)
- Rachel Humphries
- Center for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol BS8 1TD, UK; Computational Neuroscience Unit, School of Computer Science, Electrical and Electronic Engineering, and Engineering Mathematics, University of Bristol, Bristol BS8 1UB, UK
| | - Jack R Mellor
- Center for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Cian O'Donnell
- Computational Neuroscience Unit, School of Computer Science, Electrical and Electronic Engineering, and Engineering Mathematics, University of Bristol, Bristol BS8 1UB, UK; School of Computing, Engineering and Intelligent Systems, Ulster University, Magee Campus, Northland Road, Derry/Londonderry BT48 7JL, UK.
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8
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Prince LY, Bacon T, Humphries R, Tsaneva-Atanasova K, Clopath C, Mellor JR. Separable actions of acetylcholine and noradrenaline on neuronal ensemble formation in hippocampal CA3 circuits. PLoS Comput Biol 2021; 17:e1009435. [PMID: 34597293 PMCID: PMC8513881 DOI: 10.1371/journal.pcbi.1009435] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 10/13/2021] [Accepted: 09/08/2021] [Indexed: 11/19/2022] Open
Abstract
In the hippocampus, episodic memories are thought to be encoded by the formation of ensembles of synaptically coupled CA3 pyramidal cells driven by sparse but powerful mossy fiber inputs from dentate gyrus granule cells. The neuromodulators acetylcholine and noradrenaline are separately proposed as saliency signals that dictate memory encoding but it is not known if they represent distinct signals with separate mechanisms. Here, we show experimentally that acetylcholine, and to a lesser extent noradrenaline, suppress feed-forward inhibition and enhance Excitatory-Inhibitory ratio in the mossy fiber pathway but CA3 recurrent network properties are only altered by acetylcholine. We explore the implications of these findings on CA3 ensemble formation using a hierarchy of models. In reconstructions of CA3 pyramidal cells, mossy fiber pathway disinhibition facilitates postsynaptic dendritic depolarization known to be required for synaptic plasticity at CA3-CA3 recurrent synapses. We further show in a spiking neural network model of CA3 how acetylcholine-specific network alterations can drive rapid overlapping ensemble formation. Thus, through these distinct sets of mechanisms, acetylcholine and noradrenaline facilitate the formation of neuronal ensembles in CA3 that encode salient episodic memories in the hippocampus but acetylcholine selectively enhances the density of memory storage.
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Affiliation(s)
- Luke Y. Prince
- Centre for Synaptic Plasticity, School of Physiology Pharmacology, and Neuroscience, University of Bristol, Bristol, United Kingdom
- Mila, Montreal, Quebec, Canada
- School of Computer Science, McGill University, Montreal, Quebec, Canada
| | - Travis Bacon
- Centre for Synaptic Plasticity, School of Physiology Pharmacology, and Neuroscience, University of Bristol, Bristol, United Kingdom
| | - Rachel Humphries
- Centre for Synaptic Plasticity, School of Physiology Pharmacology, and Neuroscience, University of Bristol, Bristol, United Kingdom
| | - Krasimira Tsaneva-Atanasova
- Department of Mathematics and Living Systems Institute, University of Exeter, Exeter, United Kingdom
- EPRSC Centre for Predictive Modelling in Healthcare, University of Exeter, Exeter, United Kingdom
| | - Claudia Clopath
- Bioengineering Department, Imperial College London, London, United Kingdom
| | - Jack R. Mellor
- Centre for Synaptic Plasticity, School of Physiology Pharmacology, and Neuroscience, University of Bristol, Bristol, United Kingdom
- * E-mail:
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9
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Nair JD, Braksator E, Yucel BP, Fletcher-Jones A, Seager R, Mellor JR, Bashir ZI, Wilkinson KA, Henley JM. Sustained postsynaptic kainate receptor activation downregulates AMPA receptor surface expression and induces hippocampal LTD. iScience 2021; 24:103029. [PMID: 34553130 PMCID: PMC8441151 DOI: 10.1016/j.isci.2021.103029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [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: 12/28/2020] [Revised: 07/27/2021] [Accepted: 08/20/2021] [Indexed: 01/21/2023] Open
Abstract
It is well established that long-term depression (LTD) can be initiated by either NMDA or mGluR activation. Here we report that sustained activation of GluK2 subunit-containing kainate receptors (KARs) leads to α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) endocytosis and induces LTD of AMPARs (KAR-LTDAMPAR) in hippocampal neurons. The KAR-evoked loss of surface AMPARs is blocked by the ionotropic KAR inhibitor UBP 310 indicating that KAR-LTDAMPAR requires KAR channel activity. Interestingly, however, blockade of PKC or PKA also reduces GluA2 surface expression and occludes the effect of KAR activation. In acute hippocampal slices, kainate application caused a significant loss of GluA2-containing AMPARs from synapses and long-lasting depression of AMPAR excitatory postsynaptic currents in CA1. These data, together with our previously reported KAR-LTPAMPAR, demonstrate that KARs can bidirectionally regulate synaptic AMPARs and synaptic plasticity via different signaling pathways.
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Affiliation(s)
- Jithin D Nair
- Centre for Synaptic Plasticity, School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Ellen Braksator
- Centre for Synaptic Plasticity, School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Busra P Yucel
- Centre for Synaptic Plasticity, School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Alexandra Fletcher-Jones
- Centre for Synaptic Plasticity, School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Richard Seager
- Centre for Synaptic Plasticity, School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Jack R Mellor
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Zafar I Bashir
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Kevin A Wilkinson
- Centre for Synaptic Plasticity, School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Jeremy M Henley
- Centre for Synaptic Plasticity, School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK.,Centre for Neuroscience and Regenerative Medicine, Faculty of Science, University of Technology Sydney, Ultimo, NSW, Australia
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10
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Palacios-Filardo J, Udakis M, Brown GA, Tehan BG, Congreve MS, Nathan PJ, Brown AJH, Mellor JR. Acetylcholine prioritises direct synaptic inputs from entorhinal cortex to CA1 by differential modulation of feedforward inhibitory circuits. Nat Commun 2021; 12:5475. [PMID: 34531380 PMCID: PMC8445995 DOI: 10.1038/s41467-021-25280-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [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: 01/16/2020] [Accepted: 07/21/2021] [Indexed: 02/08/2023] Open
Abstract
Acetylcholine release in the hippocampus plays a central role in the formation of new memory representations. An influential but largely untested theory proposes that memory formation requires acetylcholine to enhance responses in CA1 to new sensory information from entorhinal cortex whilst depressing inputs from previously encoded representations in CA3. Here, we show that excitatory inputs from entorhinal cortex and CA3 are depressed equally by synaptic release of acetylcholine in CA1. However, feedforward inhibition from entorhinal cortex exhibits greater depression than CA3 resulting in a selective enhancement of excitatory-inhibitory balance and CA1 activation by entorhinal inputs. Entorhinal and CA3 pathways engage different feedforward interneuron subpopulations and cholinergic modulation of presynaptic function is mediated differentially by muscarinic M3 and M4 receptors, respectively. Thus, our data support a role and mechanisms for acetylcholine to prioritise novel information inputs to CA1 during memory formation.
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Affiliation(s)
- Jon Palacios-Filardo
- Center for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol, UK
| | - Matt Udakis
- Center for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol, UK
| | - Giles A Brown
- Sosei Heptares, Steinmetz Building, Granta Park, Great Abingdon, Cambridge, UK
- OMass Therapeutics Ltd, The Schrödinger Building, Oxford, UK
| | - Benjamin G Tehan
- Sosei Heptares, Steinmetz Building, Granta Park, Great Abingdon, Cambridge, UK
- OMass Therapeutics Ltd, The Schrödinger Building, Oxford, UK
| | - Miles S Congreve
- Sosei Heptares, Steinmetz Building, Granta Park, Great Abingdon, Cambridge, UK
| | - Pradeep J Nathan
- Department of Psychiatry, University of Cambridge, Cambridge, UK
| | - Alastair J H Brown
- Sosei Heptares, Steinmetz Building, Granta Park, Great Abingdon, Cambridge, UK
| | - Jack R Mellor
- Center for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol, UK.
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11
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Nair JD, Wilkinson KA, Henley JM, Mellor JR. Kainate receptors and synaptic plasticity. Neuropharmacology 2021; 196:108540. [PMID: 33794245 DOI: 10.1016/j.neuropharm.2021.108540] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 03/22/2021] [Accepted: 03/23/2021] [Indexed: 10/21/2022]
Abstract
Synaptic plasticity has classically been characterized to involve the NMDA and AMPA subtypes of glutamate receptors, with NMDA receptors providing the key trigger for the induction of long-term plasticity leading to changes in AMPA receptor expression. Here we review the more subtle roles played by kainate receptors, which contribute critical postsynaptic signalling as well as playing major presynaptic auto-receptor roles. We focus on two research areas: plasticity of kainate receptors themselves and the contribution they make to the plasticity of synaptic transmission. This article is part of the special issue on Glutamate Receptors - Kainate receptors.
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Affiliation(s)
- Jithin D Nair
- Center for Synaptic Plasticity, School of Biochemistry, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Kevin A Wilkinson
- Center for Synaptic Plasticity, School of Biochemistry, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Jeremy M Henley
- Center for Synaptic Plasticity, School of Biochemistry, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Jack R Mellor
- Center for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol, BS8 1TD, UK.
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12
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Watkins JC, Evans RH, Bayés À, Booker SA, Gibb A, Mabb AM, Mayer M, Mellor JR, Molnár E, Niu L, Ortega A, Pankratov Y, Ramos-Vicente D, Rodríguez-Campuzano A, Rodríguez-Moreno A, Wang LY, Wang YT, Wollmuth L, Wyllie DJA, Zhuo M, Frenguelli BG. 21st century excitatory amino acid research: A Q & A with Jeff Watkins and Dick Evans. Neuropharmacology 2021; 198:108743. [PMID: 34363811 DOI: 10.1016/j.neuropharm.2021.108743] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
In 1981 Jeff Watkins and Dick Evans wrote what was to become a seminal review on excitatory amino acids (EAAs) and their receptors (Watkins and Evans, 1981). Bringing together various lines of evidence dating back over several decades on: the distribution in the nervous system of putative amino acid neurotransmitters; enzymes involved in their production and metabolism; the uptake and release of amino acids; binding of EAAs to membranes; the pharmacological action of endogenous excitatory amino acids and their synthetic analogues, and notably the actions of antagonists for the excitations caused by both nerve stimulation and exogenous agonists, often using pharmacological tools developed by Jeff and his colleagues, they provided a compelling account for EAAs, especially l-glutamate, as a bona fide neurotransmitter in the nervous system. The rest, as they say, is history, but far from being consigned to history, EAA research is in rude health well into the 21st Century as this series of Special Issues of Neuropharmacology exemplifies. With EAAs and their receptors flourishing across a wide range of disciplines and clinical conditions, we enter into a dialogue with two of the most prominent and influential figures in the early days of EAA research: Jeff Watkins and Dick Evans.
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Affiliation(s)
| | | | - Àlex Bayés
- Molecular Physiology of the Synapse Laboratory, Biomedical Research Institute Sant Pau, Barcelona, Spain and Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Sam A Booker
- Simons Initiative for the Developing Brain, Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH8 9XD, UK
| | - Alasdair Gibb
- Research Department of Neuroscience, Physiology & Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Angela M Mabb
- Neuroscience Institute, Georgia State University, Atlanta, GA, United States
| | - Mark Mayer
- Bldg 35A, Room 3D-904, 35A Convent Drive, NINDS, NIH, Bethesda, MD, 20892, USA
| | - Jack R Mellor
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, BS8 1TD, UK
| | - Elek Molnár
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, BS8 1TD, UK
| | - Li Niu
- Chemistry Department, University at Albany, SUNY, 1400 Washington Ave, Albany, NY, 12222, USA
| | - Arturo Ortega
- Department of Toxicology, Cinvestav, Mexico City, Mexico
| | - Yuriy Pankratov
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
| | - David Ramos-Vicente
- Molecular Physiology of the Synapse Laboratory, Biomedical Research Institute Sant Pau, Barcelona, Spain and Universitat Autònoma de Barcelona, Barcelona, Spain
| | | | | | - Lu-Yang Wang
- Program in Neurosciences & Mental Health, SickKids Research Institute and Department of Physiology, University of Toronto, 555 University Ave, Toronto, Ontario, M5G 1X8, Canada
| | - Yu Tian Wang
- Department of Medicine, University of British Columbia, Vancouver, BC, V6T 2B5, Canada
| | - Lonnie Wollmuth
- Depts. of Neurobiology & Behavior and Biochemistry & Cell Biology, Center for Nervous System Disorders, Stony Brook University, Stony Brook, NY, 11794-5230, USA
| | - David J A Wyllie
- Simons Initiative for the Developing Brain, Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH8 9XD, UK
| | - Min Zhuo
- Institute of Brain Research, Qingdao International Academician Park, Qingdao, 266000, China
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13
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Griesius S, Mellor JR, Robinson ES. Comparison of acute treatment with delayed-onset versus rapid-acting antidepressants on effort-related choice behaviour. Psychopharmacology (Berl) 2020; 237:2381-2394. [PMID: 32435818 PMCID: PMC7351874 DOI: 10.1007/s00213-020-05541-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Accepted: 04/27/2020] [Indexed: 12/11/2022]
Abstract
RATIONALE Reward-related impairments are common in major depressive disorder (MDD) and may contribute to the loss of interest in pleasurable activities. A novel approach to studying reward-related decision-making are effort-based tasks; however, direct comparisons between delayed-onset and rapid-acting antidepressants (ADs) have not yet been carried out. OBJECTIVES To investigate the effects of conventional delayed-onset ADs versus rapid-acting ADs, ketamine and scopolamine, on effort-related choice behaviour. METHODS Female Lister hooded rats were trained in an operant effort for reward task (EfRT) where animals choose between working for a high value-high effort reward and consuming low value-low effort chow. Using a within-subject study design, animals were then tested following acute treatment with different monoaminergic ADs, and the rapid-acting ADs ketamine or scopolamine. RESULTS Consistent with previous findings, we found choice behaviour was sensitive to dopaminergic manipulations. We observed that pre-feeding altered choice behaviour and that the use of high or low value reward differentially affected behaviour. Monoamine re-uptake inhibitors and rapid-acting ADs resulted in similar, general patterns of reduced motivation without any evidence for specific effects, and we did not observe any clear differences between these classes of antidepressant. CONCLUSIONS Motivational changes induced by dopaminergic manipulations and pre-feeding differentially affect effort choice behaviour. However, both conventional delayed-onset ADs and ketamine and scopolamine appear to have detrimental effects on motivation in this task at the higher doses tested without any evidence of specificity for effort-related choice behaviour, in contrast to their specificity in tasks which look at more cognitive aspects of reward processing.
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Affiliation(s)
- Simonas Griesius
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, BS8 1TD, UK.
| | - Jack R Mellor
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, BS8 1TD, UK
| | - Emma Sj Robinson
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, BS8 1TD, UK
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14
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Bacon TJ, Pickering AE, Mellor JR. Noradrenaline Release from Locus Coeruleus Terminals in the Hippocampus Enhances Excitation-Spike Coupling in CA1 Pyramidal Neurons Via β-Adrenoceptors. Cereb Cortex 2020; 30:6135-6151. [PMID: 32607551 PMCID: PMC7609922 DOI: 10.1093/cercor/bhaa159] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [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: 02/27/2020] [Revised: 05/13/2020] [Accepted: 05/13/2020] [Indexed: 12/29/2022] Open
Abstract
Release of the neuromodulator noradrenaline signals salience during wakefulness, flagging novel or important experiences to reconfigure information processing and memory representations in the hippocampus. Noradrenaline is therefore expected to enhance hippocampal responses to synaptic input; however, noradrenergic agonists have been found to have mixed and sometimes contradictory effects on Schaffer collateral synapses and the resulting CA1 output. Here, we examine the effects of endogenous, optogenetically driven noradrenaline release on synaptic transmission and spike output in mouse hippocampal CA1 pyramidal neurons. We show that endogenous noradrenaline release enhances the probability of CA1 pyramidal neuron spiking without altering feedforward excitatory or inhibitory synaptic inputs in the Schaffer collateral pathway. β-adrenoceptors mediate this enhancement of excitation-spike coupling by reducing the charge required to initiate action potentials, consistent with noradrenergic modulation of voltage-gated potassium channels. Furthermore, we find the likely effective concentration of endogenously released noradrenaline is sub-micromolar. Surprisingly, although comparable concentrations of exogenous noradrenaline cause robust depression of slow afterhyperpolarization currents, endogenous release of noradrenaline does not, indicating that endogenous noradrenaline release is targeted to specific cellular locations. These findings provide a mechanism by which targeted endogenous release of noradrenaline can enhance information transfer in the hippocampus in response to salient events.
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Affiliation(s)
- Travis J Bacon
- Centre for Synaptic Plasticity, University of Bristol, Bristol, UK.,School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol BS8 1TD, UK
| | - Anthony E Pickering
- School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol BS8 1TD, UK.,Bristol Anaesthesia, Pain & Critical Care Sciences, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol BS2 8HW, UK
| | - Jack R Mellor
- Centre for Synaptic Plasticity, University of Bristol, Bristol, UK.,School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol BS8 1TD, UK
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15
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Abstract
Pseudoreplication occurs when the number of measured values or data points exceeds the number of genuine replicates, and when the statistical analysis treats all data points as independent and thus fully contributing to the result. By artificially inflating the sample size, pseudoreplication contributes to irreproducibility, and it is a pervasive problem in biological research. In some fields, more than half of published experiments have pseudoreplication - making it one of the biggest threats to inferential validity. Researchers may be reluctant to use appropriate statistical methods if their hypothesis is about the pseudoreplicates and not the genuine replicates; for example, when an intervention is applied to pregnant female rodents (genuine replicates) but the hypothesis is about the effect on the multiple offspring (pseudoreplicates). We propose using a Bayesian predictive approach, which enables researchers to make valid inferences about biological entities of interest, even if they are pseudoreplicates, and show the benefits of this approach using two in vivo data sets.
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Affiliation(s)
- Stanley E Lazic
- Prioris.ai Inc., 459-207 Bank Street, Ottawa, K2P 2N2, Canada.
| | - Jack R Mellor
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, BS8 1TD, UK
| | - Michael C Ashby
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, BS8 1TD, UK
| | - Marcus R Munafo
- MRC Integrative Epidemiology Unit, UK Centre for Tobacco and Alcohol Studies, School of Experimental Psychology, University of Bristol, Bristol, BS8 1TU, UK
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16
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Wilkinson MP, Grogan JP, Mellor JR, Robinson ESJ. Comparison of conventional and rapid-acting antidepressants in a rodent probabilistic reversal learning task. Brain Neurosci Adv 2020; 4:2398212820907177. [PMID: 32219179 PMCID: PMC7085917 DOI: 10.1177/2398212820907177] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Accepted: 01/15/2020] [Indexed: 12/15/2022] Open
Abstract
Deficits in reward processing are a central feature of major depressive disorder with patients exhibiting decreased reward learning and altered feedback sensitivity in probabilistic reversal learning tasks. Methods to quantify probabilistic learning in both rodents and humans have been developed, providing translational paradigms for depression research. We have utilised a probabilistic reversal learning task to investigate potential differences between conventional and rapid-acting antidepressants on reward learning and feedback sensitivity. We trained 12 rats in a touchscreen probabilistic reversal learning task before investigating the effect of acute administration of citalopram, venlafaxine, reboxetine, ketamine or scopolamine. Data were also analysed using a Q-learning reinforcement learning model to understand the effects of antidepressant treatment on underlying reward processing parameters. Citalopram administration decreased trials taken to learn the first rule and increased win-stay probability. Reboxetine decreased win-stay behaviour while also decreasing the number of rule changes animals performed in a session. Venlafaxine had no effect. Ketamine and scopolamine both decreased win-stay probability, number of rule changes performed and motivation in the task. Insights from the reinforcement learning model suggested that reboxetine led animals to choose a less optimal strategy, while ketamine decreased the model-free learning rate. These results suggest that reward learning and feedback sensitivity are not differentially modulated by conventional and rapid-acting antidepressant treatment in the probabilistic reversal learning task.
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Affiliation(s)
- Matthew P. Wilkinson
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - John P. Grogan
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Jack R. Mellor
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - Emma S. J. Robinson
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
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17
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Palacios-Filardo J, Mellor JR. Neuromodulation of hippocampal long-term synaptic plasticity. Curr Opin Neurobiol 2018; 54:37-43. [PMID: 30212713 PMCID: PMC6367596 DOI: 10.1016/j.conb.2018.08.009] [Citation(s) in RCA: 89] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Revised: 07/26/2018] [Accepted: 08/15/2018] [Indexed: 12/31/2022]
Abstract
Acetylcholine, noradrenaline, dopamine and serotonin all facilitate long-term synaptic plasticity. Neuromodulators facilitate long-term synaptic plasticity by common and divergent mechanisms. Common mechanisms include NMDA receptor facilitation by potassium channel inhibition, gliotransmission and disinhibition. Divergent mechanisms include diversity of disinhibition and temporal and spatial neuromodulator release.
Multiple neuromodulators including acetylcholine, noradrenaline, dopamine and serotonin are released in response to uncertainty to focus attention on events where the predicted outcome does not match observed reality. In these situations, internal representations need to be updated, a process that requires long-term synaptic plasticity. Through a variety of common and divergent mechanisms, it is recently shown that all these neuromodulators facilitate the induction and/or expression of long-term synaptic plasticity within the hippocampus. Under physiological conditions, this may be critical for suprathreshold induction of plasticity endowing neuromodulators with a gating function and providing a mechanism by which neuromodulators enable the targeted updating of memory with relevant information to improve the accuracy of future predictions.
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Affiliation(s)
- Jon Palacios-Filardo
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol BS8 1TD, UK
| | - Jack R Mellor
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol BS8 1TD, UK.
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18
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Parkinson GT, Chamberlain SEL, Jaafari N, Turvey M, Mellor JR, Hanley JG. Cortactin regulates endo-lysosomal sorting of AMPARs via direct interaction with GluA2 subunit. Sci Rep 2018. [PMID: 29515177 PMCID: PMC5841360 DOI: 10.1038/s41598-018-22542-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
AMPA receptor (AMPAR) trafficking is a key determinant of synaptic strength and synaptic plasticity. Under basal conditions, constitutive trafficking maintains surface AMPARs by internalization into the endosomal system, where the majority are sorted and targeted for recycling back to the plasma membrane. NMDA receptor (NMDAR)-dependent Long-Term Depression (LTD) is characterised by a reduction in synaptic strength, and involves endosomal sorting of AMPARs away from recycling pathways to lysosomes. The mechanisms that determine whether AMPARs are trafficked to lysosomes or to recycling endosomes, especially in response to NMDAR stimulation, are unclear. Here, we define a role for the actin-regulatory protein cortactin as a mediator of AMPAR endosomal sorting by direct interaction with the GluA2 subunit. Disrupting GluA2-cortactin binding in neurons causes the targeting of GluA2/A3-containing receptors to lysosomes and their consequent degradation, resulting in a loss of surface and synaptic GluA2 under basal conditions and an occlusion of subsequent LTD expression. Furthermore, we show that NMDAR stimulation causes a dissociation of endogenous cortactin from GluA2 via tyrosine phosphorylation of cortactin. These results demonstrate that cortactin maintains GluA2/A3 levels by directing receptors away from lysosomes, and that disrupting GluA2-cortactin interactions to target GluA2/A3 to lysosomes is an essential component of LTD expression.
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Affiliation(s)
- Gabrielle T Parkinson
- Centre for Synaptic Plasticity and School of Biochemistry, Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8, 1TD, UK
| | - Sophie E L Chamberlain
- Centre for Synaptic Plasticity and School of Physiology, Pharmacology & Neuroscience, Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8, 1TD, UK
| | - Nadia Jaafari
- Centre for Synaptic Plasticity and School of Biochemistry, Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8, 1TD, UK
| | - Matthew Turvey
- Centre for Synaptic Plasticity and School of Biochemistry, Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8, 1TD, UK
| | - Jack R Mellor
- Centre for Synaptic Plasticity and School of Physiology, Pharmacology & Neuroscience, Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8, 1TD, UK
| | - Jonathan G Hanley
- Centre for Synaptic Plasticity and School of Biochemistry, Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8, 1TD, UK.
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19
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Teles-Grilo Ruivo LM, Baker KL, Conway MW, Kinsley PJ, Gilmour G, Phillips KG, Isaac JTR, Lowry JP, Mellor JR. Coordinated Acetylcholine Release in Prefrontal Cortex and Hippocampus Is Associated with Arousal and Reward on Distinct Timescales. Cell Rep 2017; 18:905-917. [PMID: 28122241 PMCID: PMC5289927 DOI: 10.1016/j.celrep.2016.12.085] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [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: 07/19/2016] [Revised: 11/05/2016] [Accepted: 12/26/2016] [Indexed: 02/06/2023] Open
Abstract
Cholinergic neurotransmission throughout the neocortex and hippocampus regulates arousal, learning, and attention. However, owing to the poorly characterized timing and location of acetylcholine release, its detailed behavioral functions remain unclear. Using electrochemical biosensors chronically implanted in mice, we made continuous measurements of the spatiotemporal dynamics of acetylcholine release across multiple behavioral states. We found that tonic levels of acetylcholine release were coordinated between the prefrontal cortex and hippocampus and maximal during training on a rewarded working memory task. Tonic release also increased during REM sleep but was contingent on subsequent wakefulness. In contrast, coordinated phasic acetylcholine release occurred only during the memory task and was strongly localized to reward delivery areas without being contingent on trial outcome. These results show that coordinated acetylcholine release between the prefrontal cortex and hippocampus is associated with reward and arousal on distinct timescales, providing dual mechanisms to support learned behavior acquisition during cognitive task performance.
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Affiliation(s)
- Leonor M Teles-Grilo Ruivo
- Lilly Centre for Cognitive Neuroscience, Eli Lilly and Company Ltd., Erl Wood Manor, Windlesham, Surrey GU20 6PH, UK; Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol BS8 1TD, UK
| | - Keeley L Baker
- Department of Chemistry, Maynooth University, Co. Kildare, Ireland
| | - Michael W Conway
- Lilly Centre for Cognitive Neuroscience, Eli Lilly and Company Ltd., Erl Wood Manor, Windlesham, Surrey GU20 6PH, UK
| | - Peter J Kinsley
- Lilly Centre for Cognitive Neuroscience, Eli Lilly and Company Ltd., Erl Wood Manor, Windlesham, Surrey GU20 6PH, UK
| | - Gary Gilmour
- Lilly Centre for Cognitive Neuroscience, Eli Lilly and Company Ltd., Erl Wood Manor, Windlesham, Surrey GU20 6PH, UK
| | - Keith G Phillips
- Lilly Centre for Cognitive Neuroscience, Eli Lilly and Company Ltd., Erl Wood Manor, Windlesham, Surrey GU20 6PH, UK
| | - John T R Isaac
- Lilly Centre for Cognitive Neuroscience, Eli Lilly and Company Ltd., Erl Wood Manor, Windlesham, Surrey GU20 6PH, UK
| | - John P Lowry
- Department of Chemistry, Maynooth University, Co. Kildare, Ireland.
| | - Jack R Mellor
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol BS8 1TD, UK.
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20
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Newton AJH, Seidenstein AH, McDougal RA, Pérez-Cervera A, Huguet G, M-Seara T, Haimerl C, Angulo-Garcia D, Torcini A, Cossart R, Malvache A, Skiker K, Maouene M, Ragognetti G, Lorusso L, Viggiano A, Marcelli A, Senatore R, Parziale A, Stramaglia S, Pellicoro M, Angelini L, Amico E, Aerts H, Cortés J, Laureys S, Marinazzo D, Stramaglia S, Bassez I, Faes L, Almgren H, Razi A, Van de Steen F, Krebs R, Aerts H, Kanari L, Dlotko P, Scolamiero M, Levi R, Shillcock J, de Kock CP, Hess K, Markram H, Ly C, Marsat G, Gillespie T, Sandström M, Abrams M, Grethe JS, Martone M, De Gernier R, Solinas S, Rössert C, Haelterman M, Massar S, Pasquale V, Pastore VP, Martinoia S, Massobrio P, Capone C, Tort-Colet N, Sanchez-Vives MV, Mattia M, Almasi A, Cloherty SL, Grayden DB, Wong YT, Ibbotson MR, Meffin H, Prince LY, Tsaneva-Atanasova K, Mellor JR, Mazzoni A, Rosa M, Carpaneto J, Romito LM, Priori A, Micera S, Migliore R, Lupascu CA, Franchina F, Bologna LL, Romani A, Saray S, Van Geit W, Káli S, Thomson A, Mercer A, Lange S, Falck J, Muller E, Schürmann F, Todorov D, Capps R, Barnett W, Molkov Y, Devalle F, Pazó D, Montbrió E, Mochol G, Azab H, Hayden BY, Moreno-Bote R, Balasubramani PP, Chakravarthy SV, Muddapu VR, Gheorghiu MD, Mimica B, Withlock J, Mureșan RC, Zick JL, Schultz K, Blackman RK, Chafee MV, Netoff TI, Roberts N, Nagaraj V, Lamperski A, Netoff TI, Grado LL, Johnson MD, Darrow DP, Lonardoni D, Amin H, Di Marco S, Maccione A, Berdondini L, Nieus T, Stimberg M, Goodman DFM, Nowotny T, Koren V, Dragoi V, Obermayer K, Castro S, Fernandez M, El-Deredy W, Xu K, Maidana JP, Orio P, Chen W, Hepburn I, Casalegno F, Devresse A, Ovcharenko A, Pereira F, Delalondre F, De Schutter E, Bratby P, Gallimore AR, Klingbeil G, Zamora C, Zang Y, Crotty P, Palmerduca E, Antonietti A, Casellato C, Erö C, D’Angelo E, Gewaltig MO, Pedrocchi A, Bytschok I, Dold D, Schemmel J, Meier K, Petrovici MA, Shen HA, Surace SC, Pfister JP, Lefebvre B, Marre O, Yger P, Papoutsi A, Park J, Ash R, Smirnakis S, Poirazi P, Felix RA, Dimitrov AG, Portfors C, Daun S, Toth TI, Jędrzejewska-Szmek J, Kabbani N, Blackwel KT, Moezzi B, Schaworonkow N, Plogmacher L, Goldsworthy MR, Hordacre B, McDonnell MD, Iannella N, Ridding MC, Triesch J, Maex R, Safaryan K, Steuber V, Tang R, Tang YY, Verveyko DV, Brazhe AR, Verisokin AY, Postnov DE, Günay C, Panuccio G, Giugliano M, Prinz AA, Varona P, Rabinovich MI, Denham J, Ranner T, Cohen N, Reva M, Rebola N, Kirizs T, Nusser Z, DiGregorio D, Mavritsaki E, Rentzelas P, Ukani NH, Tomkins A, Yeh CH, Bruning W, Fenichel AL, Zhou Y, Huang YC, Florescu D, Ortiz CL, Richmond P, Lo CC, Coca D, Chiang AS, Lazar AA, Moezzi B, Creaser JL, Lin C, Ashwin P, Brown JT, Ridler T, Levenstein D, Watson BO, Buzsáki G, Rinzel J, Curtu R, Nguyen A, Assadzadeh S, Robinson PA, Sanz-Leon P, Forlim CG, de Almeida LOB, Pinto RD, Rodríguez FB, Lareo Á, Forlim CG, Rodríguez FB, Montero A, Mosqueiro T, Huerta R, Rodriguez FB, Changoluisa V, Rodriguez FB, Cordeiro VL, Ceballos CC, Kamiji NL, Roque AC, Lytton WW, Knox A, Rosenthal JJC, Daun S, Popovych S, Liu L, Wang BA, Tóth TI, Grefkes C, Fink GR, Rosjat N, Perez-Trujillo A, Espinal A, Sotelo-Figueroa MA, Cruz-Aceves I, Rostro-Gonzalez H, Zapotocky M, Hoskovcová M, Kopecká J, Ulmanová O, Růžička E, Gärtner M, Duvarci S, Roeper J, Schneider G, Albert S, Schmack K, Remme M, Schreiber S, Migliore M, Lupascu CA, Bologna LL, Antonel SM, Courcol JD, Schürmann F, Çelikok SU, Navarro-López EM, Şengör NS, Elibol R, Sengor NS, Özdemir MY, Li T, Arleo A, Sheynikhovich D, Nakamura A, Shimono M, Song Y, Park S, Choi I, Jeong J, Shin HS, Sadeh S, Gleeson P, Angus Silver R, Chatzikalymniou AP, Skinner FK, Sanchez-Rodriguez LM, Sotero RC, Hertäg L, Mackwood O, Sprekeler H, Puhlmann S, Weber SN, Higgins D, Naumann LB, Weber SN, Iyer R, Mihalas S, Ticcinelli V, Stankovski T, McClintock PVE, Stefanovska A, Janjić P, Solev D, Seifert G, Kocarev L, Steinhäuser C, Salmasi M, Glasauer S, Stemmler M, Zhang D, Zhang C, Stepanyants A, Goncharenko J, Kros L, Davey N, de Zeeuw C, Hoebeek F, Sinha A, Adams R, Schmuker M, Psarrou M, Schilstra M, Torben-Nielsen B, Metzner C, Schweikard A, Mäki-Marttunen T, Zurowski B, Marinazzo D, Faes L, Stramaglia S, Jordan HOC, Stringer SM, Gajewska-Dendek E, Suffczyński P, Tam N, Zouridakis G, Pollonini L, Tang YY, Asl MM, Valizadeh A, Tass PA, Nold A, Fan W, Konrad S, Endle H, Vogt J, Tchumatchenko T, Herpich J, Tetzlaff C, Luboeinski J, Nachstedt T, Ciba M, Bahmer A, Thielemann C, Kuebler ES, Tauskela JS, Thivierge JP, Bakker R, García-Amado M, Evangelio M, Clascá F, Tiesinga P, Buckley CL, Toyoizumi T, Dubreuil AM, Monasson R, Treves A, Spalla D, Rosay S, Kleberg FI, Wong W, de Oliveira Floriano B, Matsuo T, Uchida T, Dibenedetto D, Uludağ K, Goodarzinick A, Schmidt M, Hilgetag CC, Diesmann M, van Albada SJ, Fauth M, van Rossum M, Reyes-Sánchez M, Amaducci R, Muñiz C, Varona P, Elices I, Arroyo D, Levi R, Cohen B, Chow C, Vattikuti S, Bertolotti E, Burioni R, di Volo M, Vezzani A, Menzat B, Vogels TP, Wagatsuma N, Saha S, Kapoor R, Kerr R, Wagner J, del Molino LCG, Yang GR, Mejias JF, Wang XJ, Song H, Goodliffe J, Luebke J, Weaver CM, Thomas J, Sinha N, Shaju N, Maszczyk T, Jin J, Cash SS, Dauwels J, Brandon Westover M, Karimian M, Moerel M, De Weerd P, Burwick T, Westra RL, Abeysuriya R, Hadida J, Sotiropoulos S, Jbabdi S, Woolrich M, Bensmail C, Wrobel B, Zhou X, Ji Z, Liu X, Xia Y, Wu S, Wang X, Zhang M, Wu S, Ofer N, Shefi O, Yaari G, Carnevale T, Majumdar A, Sivagnanam S, Yoshimoto K, Smirnova EY, Amakhin DV, Malkin SL, Zaitsev AV, Chizhov AV, Zaleshina M, Zaleshin A, Barranca VJ, Zhu G, Skilling QM, Maruyama D, Ognjanovski N, Aton SJ, Zochowski M, Wu J, Aton S, Rich S, Booth V, Budak M, Dura-Bernal S, Neymotin SA, Suter BA, Shepherd GMG, Felton MA, Yu AB, Boothe DL, Oie KS, Franaszczuk PJ, Shuvaev SA, Başerdem B, Zador A, Koulakov AA, López-Madrona VJ, Pereda E, Mirasso CR, Canals S, Masoli S, Rongala UB, Mazzoni A, Spanne A, Jorntell H, Oddo CM, Vartanov AV, Neklyudova AK, Kozlovskiy SA, Kiselnikov AA, Marakshina JA, Teleńczuk M, Teleńczuk B, Destexhe A, Kuokkanen PT, Kraemer A, McColgan T, Carr CE, Kempter R. 26th Annual Computational Neuroscience Meeting (CNS*2017): Part 3. BMC Neurosci 2017. [PMCID: PMC5592441 DOI: 10.1186/s12868-017-0372-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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21
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Betterton RT, Broad LM, Tsaneva‐Atanasova K, Mellor JR. Acetylcholine modulates gamma frequency oscillations in the hippocampus by activation of muscarinic M1 receptors. Eur J Neurosci 2017; 45:1570-1585. [PMID: 28406538 PMCID: PMC5518221 DOI: 10.1111/ejn.13582] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [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: 10/24/2016] [Revised: 04/04/2017] [Accepted: 04/07/2017] [Indexed: 12/21/2022]
Abstract
Modulation of gamma oscillations is important for the processing of information and the disruption of gamma oscillations is a prominent feature of schizophrenia and Alzheimer's disease. Gamma oscillations are generated by the interaction of excitatory and inhibitory neurons where their precise frequency and amplitude are controlled by the balance of excitation and inhibition. Acetylcholine enhances the intrinsic excitability of pyramidal neurons and suppresses both excitatory and inhibitory synaptic transmission, but the net modulatory effect on gamma oscillations is not known. Here, we find that the power, but not frequency, of optogenetically induced gamma oscillations in the CA3 region of mouse hippocampal slices is enhanced by low concentrations of the broad‐spectrum cholinergic agonist carbachol but reduced at higher concentrations. This bidirectional modulation of gamma oscillations is replicated within a mathematical model by neuronal depolarisation, but not by reducing synaptic conductances, mimicking the effects of muscarinic M1 receptor activation. The predicted role for M1 receptors was supported experimentally; bidirectional modulation of gamma oscillations by acetylcholine was replicated by a selective M1 receptor agonist and prevented by genetic deletion of M1 receptors. These results reveal that acetylcholine release in CA3 of the hippocampus modulates gamma oscillation power but not frequency in a bidirectional and dose‐dependent manner by acting primarily through muscarinic M1 receptors.
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Affiliation(s)
- Ruth T. Betterton
- Centre for Synaptic PlasticitySchool of Physiology, Pharmacology and NeuroscienceUniversity of BristolBristolBS8 1TDUK
| | | | - Krasimira Tsaneva‐Atanasova
- Department of MathematicsCollege of Engineering, Mathematics and Physical SciencesUniversity of ExeterExeterEX4 4QFUK
| | - Jack R. Mellor
- Centre for Synaptic PlasticitySchool of Physiology, Pharmacology and NeuroscienceUniversity of BristolBristolBS8 1TDUK
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Prince LY, Bacon TJ, Tigaret CM, Mellor JR. Neuromodulation of the Feedforward Dentate Gyrus-CA3 Microcircuit. Front Synaptic Neurosci 2016; 8:32. [PMID: 27799909 PMCID: PMC5065980 DOI: 10.3389/fnsyn.2016.00032] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [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: 07/31/2016] [Accepted: 09/20/2016] [Indexed: 12/16/2022] Open
Abstract
The feedforward dentate gyrus-CA3 microcircuit in the hippocampus is thought to activate ensembles of CA3 pyramidal cells and interneurons to encode and retrieve episodic memories. The creation of these CA3 ensembles depends on neuromodulatory input and synaptic plasticity within this microcircuit. Here we review the mechanisms by which the neuromodulators aceylcholine, noradrenaline, dopamine, and serotonin reconfigure this microcircuit and thereby infer the net effect of these modulators on the processes of episodic memory encoding and retrieval.
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Affiliation(s)
- Luke Y Prince
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol Bristol, UK
| | - Travis J Bacon
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol Bristol, UK
| | - Cezar M Tigaret
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol Bristol, UK
| | - Jack R Mellor
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol Bristol, UK
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23
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Griffith T, Tsaneva-Atanasova K, Mellor JR. Control of Ca2+ Influx and Calmodulin Activation by SK-Channels in Dendritic Spines. PLoS Comput Biol 2016; 12:e1004949. [PMID: 27232631 PMCID: PMC4883788 DOI: 10.1371/journal.pcbi.1004949] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 04/28/2016] [Indexed: 11/18/2022] Open
Abstract
The key trigger for Hebbian synaptic plasticity is influx of Ca2+ into postsynaptic dendritic spines. The magnitude of [Ca2+] increase caused by NMDA-receptor (NMDAR) and voltage-gated Ca2+ -channel (VGCC) activation is thought to determine both the amplitude and direction of synaptic plasticity by differential activation of Ca2+ -sensitive enzymes such as calmodulin. Ca2+ influx is negatively regulated by Ca2+ -activated K+ channels (SK-channels) which are in turn inhibited by neuromodulators such as acetylcholine. However, the precise mechanisms by which SK-channels control the induction of synaptic plasticity remain unclear. Using a 3-dimensional model of Ca2+ and calmodulin dynamics within an idealised, but biophysically-plausible, dendritic spine, we show that SK-channels regulate calmodulin activation specifically during neuron-firing patterns associated with induction of spike timing-dependent plasticity. SK-channel activation and the subsequent reduction in Ca2+ influx through NMDARs and L-type VGCCs results in an order of magnitude decrease in calmodulin (CaM) activation, providing a mechanism for the effective gating of synaptic plasticity induction. This provides a common mechanism for the regulation of synaptic plasticity by neuromodulators. Hebbian or associative plasticity is triggered by postsynaptic Ca2+ influx which activates calmodulin and CaMKII. The influx of Ca2+ through voltage-dependent NMDA receptors and Ca2+ channels is regulated by Ca2+ -activated K+ channels (SK-channels) providing negative feedback regulation of postsynaptic [Ca2+]. Using 3-dimensional modeling of Ca2+ and calmodulin dynamics within dendritic spines we show that the non-linear relationship between Ca2+ influx and calmodulin activation endows SK-channels with the ability to “gate” calmodulin activation and therefore the induction of Hebbian synaptic plasticity. Since SK-channels are inhibited by several neuromodulator receptors including acetylcholine and noradrenaline, the gating of synaptic plasticity by SK-channels could represent a common mechanism by which neuromodulators control the induction of synaptic plasticity.
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Affiliation(s)
- Thom Griffith
- Department of Engineering Mathematics, University of Bristol, Bristol, United Kingdom
- Bristol Centre for Complexity Sciences, University of Bristol, Bristol, United Kingdom
| | - Krasimira Tsaneva-Atanasova
- Department of Mathematics, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, United Kingdom
- EPSRC Centre for Predictive Modelling in Healthcare, University of Exeter, Exeter, United Kingdom
- * E-mail: (KTA); (JRM)
| | - Jack R. Mellor
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom
- * E-mail: (KTA); (JRM)
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24
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Tigaret CM, Olivo V, Sadowski JHLP, Ashby MC, Mellor JR. Coordinated activation of distinct Ca(2+) sources and metabotropic glutamate receptors encodes Hebbian synaptic plasticity. Nat Commun 2016; 7:10289. [PMID: 26758963 PMCID: PMC4735496 DOI: 10.1038/ncomms10289] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 11/26/2015] [Indexed: 01/10/2023] Open
Abstract
At glutamatergic synapses, induction of associative synaptic plasticity requires time-correlated presynaptic and postsynaptic spikes to activate postsynaptic NMDA receptors (NMDARs). The magnitudes of the ensuing Ca2+ transients within dendritic spines are thought to determine the amplitude and direction of synaptic change. In contrast, we show that at mature hippocampal Schaffer collateral synapses the magnitudes of Ca2+ transients during plasticity induction do not match this rule. Indeed, LTP induced by time-correlated pre- and postsynaptic spikes instead requires the sequential activation of NMDARs followed by voltage-sensitive Ca2+ channels within dendritic spines. Furthermore, LTP requires inhibition of SK channels by mGluR1, which removes a negative feedback loop that constitutively regulates NMDARs. Therefore, rather than being controlled simply by the magnitude of the postsynaptic calcium rise, LTP induction requires the coordinated activation of distinct sources of Ca2+ and mGluR1-dependent facilitation of NMDAR function. During STDP, the magnitude of postsynaptic Ca2+ transients is hypothesized to determine the strength of synaptic plasticity. Here, the authors find that STDP in mature hippocampal synapses does not obey this rule but instead relies on the coordinated activation of NMDARs and VGCCs and their regulation by mGluRs and SK channels.
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Affiliation(s)
- Cezar M Tigaret
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Valeria Olivo
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Josef H L P Sadowski
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Michael C Ashby
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Jack R Mellor
- Centre for Synaptic Plasticity, School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol BS8 1TD, UK
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Dennis SH, Pasqui F, Colvin EM, Sanger H, Mogg AJ, Felder CC, Broad LM, Fitzjohn SM, Isaac JTR, Mellor JR. Activation of Muscarinic M1 Acetylcholine Receptors Induces Long-Term Potentiation in the Hippocampus. Cereb Cortex 2015; 26:414-26. [PMID: 26472558 PMCID: PMC4677984 DOI: 10.1093/cercor/bhv227] [Citation(s) in RCA: 106] [Impact Index Per Article: 11.8] [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: 11/29/2022] Open
Abstract
Muscarinic M1 acetylcholine receptors (M1Rs) are highly expressed in the hippocampus, and their inhibition or ablation disrupts the encoding of spatial memory. It has been hypothesized that the principal mechanism by which M1Rs influence spatial memory is by the regulation of hippocampal synaptic plasticity. Here, we use a combination of recently developed, well characterized, selective M1R agonists and M1R knock-out mice to define the roles of M1Rs in the regulation of hippocampal neuronal and synaptic function. We confirm that M1R activation increases input resistance and depolarizes hippocampal CA1 pyramidal neurons and show that this profoundly increases excitatory postsynaptic potential-spike coupling. Consistent with a critical role for M1Rs in synaptic plasticity, we now show that M1R activation produces a robust potentiation of glutamatergic synaptic transmission onto CA1 pyramidal neurons that has all the hallmarks of long-term potentiation (LTP): The potentiation requires NMDA receptor activity and bi-directionally occludes with synaptically induced LTP. Thus, we describe synergistic mechanisms by which acetylcholine acting through M1Rs excites CA1 pyramidal neurons and induces LTP, to profoundly increase activation of CA1 pyramidal neurons. These features are predicted to make a major contribution to the pro-cognitive effects of cholinergic transmission in rodents and humans.
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Affiliation(s)
- Siobhan H Dennis
- Neuroscience, Eli Lilly & Company, Windlesham, Surrey GU20 6PH, UK
| | - Francesca Pasqui
- Neuroscience, Eli Lilly & Company, Windlesham, Surrey GU20 6PH, UK
| | - Ellen M Colvin
- Neuroscience, Eli Lilly & Company, Windlesham, Surrey GU20 6PH, UK
| | - Helen Sanger
- Neuroscience, Eli Lilly & Company, Windlesham, Surrey GU20 6PH, UK
| | - Adrian J Mogg
- Neuroscience, Eli Lilly & Company, Windlesham, Surrey GU20 6PH, UK
| | | | - Lisa M Broad
- Neuroscience, Eli Lilly & Company, Windlesham, Surrey GU20 6PH, UK
| | - Steve M Fitzjohn
- Neuroscience, Eli Lilly & Company, Windlesham, Surrey GU20 6PH, UK School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, UK
| | - John T R Isaac
- Neuroscience, Eli Lilly & Company, Windlesham, Surrey GU20 6PH, UK
| | - Jack R Mellor
- School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, UK
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26
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Rocca DL, Amici M, Antoniou A, Blanco Suarez E, Halemani N, Murk K, McGarvey J, Jaafari N, Mellor JR, Collingridge GL, Hanley JG. The small GTPase Arf1 modulates Arp2/3-mediated actin polymerization via PICK1 to regulate synaptic plasticity. Neuron 2013; 79:293-307. [PMID: 23889934 PMCID: PMC3725416 DOI: 10.1016/j.neuron.2013.05.003] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/23/2013] [Indexed: 11/17/2022]
Abstract
Inhibition of Arp2/3-mediated actin polymerization by PICK1 is a central mechanism to AMPA receptor (AMPAR) internalization and long-term depression (LTD), although the signaling pathways that modulate this process in response to NMDA receptor (NMDAR) activation are unknown. Here, we define a function for the GTPase Arf1 in this process. We show that Arf1-GTP binds PICK1 to limit PICK1-mediated inhibition of Arp2/3 activity. Expression of mutant Arf1 that does not bind PICK1 leads to reduced surface levels of GluA2-containing AMPARs and smaller spines in hippocampal neurons, which occludes subsequent NMDA-induced AMPAR internalization and spine shrinkage. In organotypic slices, NMDAR-dependent LTD of AMPAR excitatory postsynaptic currents is abolished in neurons expressing mutant Arf1. Furthermore, NMDAR stimulation downregulates Arf1 activation and binding to PICK1 via the Arf-GAP GIT1. This study defines Arf1 as a critical regulator of actin dynamics and synaptic function via modulation of PICK1. The Arf1-PICK1-Arp2/3 pathway regulates actin polymerization NMDAR activation activates the Arf-GAP GIT1 to deactivate Arf1 Arf1 controls NMDAR-dependent, PICK1-mediated AMPAR trafficking and LTD A noncanonical role is described for Arf1 in vesicle traffic, distinct from COPI regulation
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Affiliation(s)
- Daniel L Rocca
- School of Biochemistry, Centre for Synaptic Plasticity, Medical Sciences Building and Dorothy Hodgkin Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
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27
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Abstract
Cholinergic septohippocampal projections from the medial septal area to the hippocampus are proposed to have important roles in cognition by modulating properties of the hippocampal network. However, the precise spatial and temporal profile of acetylcholine release in the hippocampus remains unclear making it difficult to define specific roles for cholinergic transmission in hippocampal dependent behaviors. This is partly due to a lack of tools enabling specific intervention in, and recording of, cholinergic transmission. Here, we review the organization of septohippocampal cholinergic projections and hippocampal acetylcholine receptors as well as the role of cholinergic transmission in modulating cellular excitability, synaptic plasticity, and rhythmic network oscillations. We point to a number of open questions that remain unanswered and discuss the potential for recently developed techniques to provide a radical reappraisal of the function of cholinergic inputs to the hippocampus.
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Affiliation(s)
- Leonor M Teles-Grilo Ruivo
- Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, University Walk Bristol, UK
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28
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Craig TJ, Jaafari N, Petrovic MM, Jacobs SC, Rubin PP, Mellor JR, Henley JM. Homeostatic synaptic scaling is regulated by protein SUMOylation. J Biol Chem 2013. [DOI: 10.1074/jbc.a112.356337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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29
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Chamberlain SEL, González-González IM, Wilkinson KA, Konopacki FA, Kantamneni S, Henley JM, Mellor JR. SUMOylation and phosphorylation of GluK2 regulate kainate receptor trafficking and synaptic plasticity. Nat Neurosci 2012; 15:845-52. [PMID: 22522402 PMCID: PMC3435142 DOI: 10.1038/nn.3089] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [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: 12/12/2011] [Accepted: 03/14/2012] [Indexed: 02/07/2023]
Abstract
Phosphorylation or SUMOylation of the kainate receptor (KAR) subunit GluK2 have both individually been shown to regulate KAR surface expression. However, it is unknown whether phosphorylation and SUMOylation of GluK2 are important for activity-dependent KAR synaptic plasticity. We found that protein kinase C–mediated phosphorylation of GluK2 at serine 868 promotes GluK2 SUMOylation at lysine 886 and that both of these events are necessary for the internalization of GluK2-containing KARs that occurs during long-term depression of KAR-mediated synaptic transmission at rat hippocampal mossy fiber synapses. Conversely, phosphorylation of GluK2 at serine 868 in the absence of SUMOylation led to an increase in KAR surface expression by facilitating receptor recycling between endosomal compartments and the plasma membrane. Our results suggest a role for the dynamic control of synaptic SUMOylation in the regulation of KAR synaptic transmission and plasticity.
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Affiliation(s)
- Sophie E L Chamberlain
- MRC Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Inmaculada M González-González
- MRC Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Kevin A Wilkinson
- MRC Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Filip A Konopacki
- MRC Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Sriharsha Kantamneni
- MRC Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Jeremy M Henley
- MRC Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Jack R Mellor
- MRC Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, University Walk, Bristol, BS8 1TD, UK
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30
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Abstract
Homeostatic scaling allows neurons to alter synaptic transmission to compensate for changes in network activity. Here, we show that suppression of network activity with tetrodotoxin, which increases surface expression of AMPA receptors (AMPARs), dramatically reduces levels of the deSUMOylating (where SUMO is small ubiquitin-like modifier) enzyme SENP1, leading to a consequent increase in protein SUMOylation. Overexpression of the catalytic domain of SENP1 prevents this scaling effect, and we identify Arc as a SUMO substrate involved in the tetrodotoxin-induced increase in AMPAR surface expression. Thus, protein SUMOylation plays an important and previously unsuspected role in synaptic trafficking of AMPARs that underlies homeostatic scaling.
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Affiliation(s)
- Tim J Craig
- Medical Research Council Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, Bristol BS8 1TD, United Kingdom
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Petrovic MM, Nowacki J, Olivo V, Tsaneva-Atanasova K, Randall AD, Mellor JR. Inhibition of post-synaptic Kv7/KCNQ/M channels facilitates long-term potentiation in the hippocampus. PLoS One 2012; 7:e30402. [PMID: 22348007 PMCID: PMC3278412 DOI: 10.1371/journal.pone.0030402] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 12/20/2011] [Indexed: 12/02/2022] Open
Abstract
Activation of muscarinic acetylcholine receptors (mAChR) facilitates the induction of synaptic plasticity and enhances cognitive function. In the hippocampus, M1 mAChR on CA1 pyramidal cells inhibit both small conductance Ca2+-activated KCa2 potassium channels and voltage-activated Kv7 potassium channels. Inhibition of KCa2 channels facilitates long-term potentiation (LTP) by enhancing Ca2+calcium influx through postsynaptic NMDA receptors (NMDAR). Inhibition of Kv7 channels is also reported to facilitate LTP but the mechanism of action is unclear. Here, we show that inhibition of Kv7 channels with XE-991 facilitated LTP induced by theta burst pairing at Schaffer collateral commissural synapses in rat hippocampal slices. Similarly, negating Kv7 channel conductance using dynamic clamp methodologies also facilitated LTP. Negation of Kv7 channels by XE-991 or dynamic clamp did not enhance synaptic NMDAR activation in response to theta burst synaptic stimulation. Instead, Kv7 channel inhibition increased the amplitude and duration of the after-depolarisation following a burst of action potentials. Furthermore, the effects of XE-991 were reversed by re-introducing a Kv7-like conductance with dynamic clamp. These data reveal that Kv7 channel inhibition promotes NMDAR opening during LTP induction by enhancing depolarisation during and after bursts of postsynaptic action potentials. Thus, during the induction of LTP M1 mAChRs enhance NMDAR opening by two distinct mechanisms namely inhibition of KCa2 and Kv7 channels.
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Affiliation(s)
- Milos M. Petrovic
- Medical Research Council Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
- Institute of Medical Physiology, School of Medicine, Belgrade University, Beograd, Serbia
| | - Jakub Nowacki
- Bristol Centre for Applied Nonlinear Mathematics, Department of Engineering Mathematics, University of Bristol, Bristol, United Kingdom
| | - Valeria Olivo
- Medical Research Council Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
| | - Krasimira Tsaneva-Atanasova
- Bristol Centre for Applied Nonlinear Mathematics, Department of Engineering Mathematics, University of Bristol, Bristol, United Kingdom
| | - Andrew D. Randall
- Medical Research Council Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
| | - Jack R. Mellor
- Medical Research Council Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
- * E-mail:
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Sadowski JHLP, Mellor JR. Putting Plasticity in Its Place. Front Neurosci 2012; 6:110. [PMID: 22826695 PMCID: PMC3395797 DOI: 10.3389/fnins.2012.00110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Accepted: 06/27/2012] [Indexed: 11/13/2022] Open
Affiliation(s)
- Josef H. L. P. Sadowski
- MRC Centre for Synaptic Plasticity, School of Physiological and Pharmacology, University of BristolBristol, UK
- *Correspondence:
| | - Jack R. Mellor
- MRC Centre for Synaptic Plasticity, School of Physiological and Pharmacology, University of BristolBristol, UK
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Konopacki FA, Jaafari N, Rocca DL, Wilkinson KA, Chamberlain S, Rubin P, Kantamneni S, Mellor JR, Henley JM. Agonist-induced PKC phosphorylation regulates GluK2 SUMOylation and kainate receptor endocytosis. Proc Natl Acad Sci U S A 2011; 108:19772-7. [PMID: 22089239 PMCID: PMC3241814 DOI: 10.1073/pnas.1111575108] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [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: 11/18/2022] Open
Abstract
The surface expression and regulated endocytosis of kainate (KA) receptors (KARs) plays a critical role in neuronal function. PKC can modulate KAR trafficking, but the sites of action and molecular consequences have not been fully characterized. Small ubiquitin-like modifier (SUMO) modification of the KAR subunit GluK2 mediates agonist-evoked internalization, but how KAR activation leads to GluK2 SUMOylation is unclear. Here we show that KA stimulation causes rapid phosphorylation of GluK2 by PKC, and that PKC activation increases GluK2 SUMOylation both in vitro and in neurons. The intracellular C-terminal domain of GluK2 contains two predicted PKC phosphorylation sites, S846 and S868, both of which are phosphorylated in response to KA. Phosphomimetic mutagenesis of S868 increased GluK2 SUMOylation, and mutation of S868 to a nonphosphorylatable alanine prevented KA-induced SUMOylation and endocytosis in neurons. Infusion of SUMO-1 dramatically reduced KAR-mediated currents in HEK293 cells expressing WT GluK2 or nonphosphorylatable S846A mutant, but had no effect on currents mediated by the S868A mutant. These data demonstrate that agonist activation of GluK2 promotes PKC-dependent phosphorylation of S846 and S868, but that only S868 phosphorylation is required to enhance GluK2 SUMOylation and promote endocytosis. Thus, direct phosphorylation by PKC and GluK2 SUMOylation are intimately linked in regulating the surface expression and function of GluK2-containing KARs.
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Affiliation(s)
| | | | | | | | - Sophie Chamberlain
- School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom
| | | | | | - Jack R. Mellor
- School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom
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Nakamura Y, Wood CL, Patton AP, Jaafari N, Henley JM, Mellor JR, Hanley JG. PICK1 inhibition of the Arp2/3 complex controls dendritic spine size and synaptic plasticity. EMBO J 2011; 30:719-30. [PMID: 21252856 PMCID: PMC3041953 DOI: 10.1038/emboj.2010.357] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2010] [Accepted: 12/20/2010] [Indexed: 12/19/2022] Open
Abstract
Activity-dependent remodelling of dendritic spines is essential for neural circuit development and synaptic plasticity, but the precise molecular mechanisms that regulate this process are unclear. Activators of Arp2/3-mediated actin polymerisation are required for spine enlargement; however, during long-term depression (LTD), spines shrink via actin depolymerisation and Arp2/3 inhibitors in this process have not yet been identified. Here, we show that PICK1 regulates spine size in hippocampal neurons via inhibition of the Arp2/3 complex. PICK1 knockdown increases spine size, whereas PICK1 overexpression reduces spine size. NMDA receptor activation results in spine shrinkage, which is blocked by PICK1 knockdown or overexpression of a PICK1 mutant that cannot bind Arp2/3. Furthermore, we show that PICK1-Arp2/3 interactions are required for functional hippocampal LTD. This work demonstrates that PICK1 is a novel regulator of spine dynamics. Via Arp2/3 inhibition, PICK1 has complementary yet distinct roles during LTD to regulate AMPA receptor trafficking and spine size, and therefore functions as a crucial factor in both structural and functional plasticity.
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Affiliation(s)
- Yasuko Nakamura
- MRC Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, University Walk, Bristol, UK
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35
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Buchanan KA, Petrovic MM, Chamberlain SEL, Marrion NV, Mellor JR. Facilitation of long-term potentiation by muscarinic M(1) receptors is mediated by inhibition of SK channels. Neuron 2011; 68:948-63. [PMID: 21145007 PMCID: PMC3003154 DOI: 10.1016/j.neuron.2010.11.018] [Citation(s) in RCA: 144] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/01/2010] [Indexed: 12/01/2022]
Abstract
Muscarinic receptor activation facilitates the induction of synaptic plasticity and enhances cognitive function. However, the specific muscarinic receptor subtype involved and the critical intracellular signaling pathways engaged have remained controversial. Here, we show that the recently discovered highly selective allosteric M1 receptor agonist 77-LH-28-1 facilitates long-term potentiation (LTP) induced by theta burst stimulation at Schaffer collateral synapses in the hippocampus. Similarly, release of acetylcholine by stimulation of cholinergic fibers facilitates LTP via activation of M1 receptors. N-methyl-D-aspartate receptor (NMDAR) opening during theta burst stimulation was enhanced by M1 receptor activation, indicating this is the mechanism for LTP facilitation. M1 receptors were found to enhance NMDAR activation by inhibiting SK channels that otherwise act to hyperpolarize postsynaptic spines and inhibit NMDAR opening. Thus, we describe a mechanism where M1 receptor activation inhibits SK channels, allowing enhanced NMDAR activity and leading to a facilitation of LTP induction in the hippocampus.
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Affiliation(s)
- Katherine A Buchanan
- Medical Research Council Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, University Walk, Bristol BS8 1TD, UK
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36
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Rackham OJL, Tsaneva-Atanasova K, Ganesh A, Mellor JR. A Ca-Based Computational Model for NMDA Receptor-Dependent Synaptic Plasticity at Individual Post-Synaptic Spines in the Hippocampus. Front Synaptic Neurosci 2010; 2:31. [PMID: 21423517 PMCID: PMC3059685 DOI: 10.3389/fnsyn.2010.00031] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [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] [Received: 01/21/2010] [Accepted: 06/27/2010] [Indexed: 11/22/2022] Open
Abstract
Associative synaptic plasticity is synapse specific and requires coincident activity in pre-synaptic and post-synaptic neurons to activate NMDA receptors (NMDARs). The resultant Ca2+ influx is the critical trigger for the induction of synaptic plasticity. Given its centrality for the induction of synaptic plasticity, a model for NMDAR activation incorporating the timing of pre-synaptic glutamate release and post-synaptic depolarization by back-propagating action potentials could potentially predict the pre- and post-synaptic spike patterns required to induce synaptic plasticity. We have developed such a model by incorporating currently available data on the timecourse and amplitude of the post-synaptic membrane potential within individual spines. We couple this with data on the kinetics of synaptic NMDARs and then use the model to predict the continuous spine [Ca2+] in response to regular or irregular pre- and post-synaptic spike patterns. We then incorporate experimental data from synaptic plasticity induction protocols by regular activity patterns to couple the predicted local peak [Ca2+] to changes in synaptic strength. We find that our model accurately describes [Ca2+] in dendritic spines resulting from NMDAR activation during pre-synaptic and post-synaptic activity when compared to previous experimental observations. The model also replicates the experimentally determined plasticity outcome of regular and irregular spike patterns when applied to a single synapse. This model could therefore be used to predict the induction of synaptic plasticity under a variety of experimental conditions and spike patterns.
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Affiliation(s)
- Owen J L Rackham
- Department of Engineering Mathematics, Bristol Centre for Complexity Sciences, University of Bristol, University Walk Bristol, UK
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37
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Buchanan KA, Mellor JR. The activity requirements for spike timing-dependent plasticity in the hippocampus. Front Synaptic Neurosci 2010; 2:11. [PMID: 21423497 PMCID: PMC3059701 DOI: 10.3389/fnsyn.2010.00011] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [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: 01/22/2010] [Accepted: 05/17/2010] [Indexed: 12/02/2022] Open
Abstract
Synaptic plasticity has historically been investigated most intensely in the hippocampus and therefore it is somewhat surprising that the majority of studies on spike timing-dependent plasticity (STDP) have focused not in the hippocampus but on synapses in the cortex. One of the major reasons for this bias is the relative ease in obtaining paired electrophysiological recordings from synaptically coupled neurons in cortical slices, in comparison to hippocampal slices. Another less obvious reason has been the difficulty in achieving reliable STDP in the hippocampal slice preparation and confusion surrounding the conditions required. The original descriptions of STDP in the hippocampus was performed on paired recordings from neurons in dissociated or slice cultures utilizing single pairs of presynaptic and postsynaptic spikes and were subsequently replicated in acute hippocampal slices. Further work in several laboratories using conditions that more closely replicate the situation in vivo revealed a requirement for multiple postsynaptic spikes that necessarily complicate the absolute timing rules for STDP. Here we review the hippocampal STDP literature focusing on data from acute hippocampal slice preparations and highlighting apparently contradictory results and the variations in experimental conditions that might account for the discrepancies. We conclude by relating the majority of the available experimental data to a model for STDP induction in the hippocampus based on a critical role for postsynaptic Ca2+ dynamics.
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Affiliation(s)
- Katherine A Buchanan
- Department of Neuroscience, Physiology and Pharmacology, University College London London, UK
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38
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Mistry R, Dennis S, Frerking M, Mellor JR. Dentate gyrus granule cell firing patterns can induce mossy fiber long-term potentiation in vitro. Hippocampus 2010; 21:1157-68. [PMID: 20635414 DOI: 10.1002/hipo.20815] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/25/2010] [Indexed: 11/09/2022]
Abstract
Hippocampal granule cells transmit information about behaviorally-relevant stimuli to CA3 pyramidal cells via mossy fiber synapses. These synapses express a form of long-term potentiation (mfLTP) that is non-Hebbian and does not require NMDA receptors. mfLTP is thought to be induced and expressed presynaptically, hence, the major determinant of whether mfLTP occurs is activity in the granule cells. However, it remains unclear whether mfLTP can be induced by activity patterns that granule cells exhibit in vivo, and-if so-what context generates these patterns. To address these issues, we examined granule cell activity from in vivo recordings from rats during performance of a delayed nonmatch-to-sample (DNMS) task and found that granule cells exhibit a wide range of spike patterns. In vitro slice experiments in mice demonstrated that some, but not all, of these patterns of activity could induce mfLTP. By further defining the activity thresholds for mfLTP in hippocampal slices, we found that mfLTP can only be induced by spike patterns that fire in high frequency bursts with a low average firing frequency. Using this information, we then screened for suprathreshold bursts of activity during the DNMS task. In a subset of cells, suprathreshold bursts occurred preferentially during the sampling phase of the task. If suprathreshold bursting took place later, during the delay phase, task performance was disrupted. We conclude that mfLTP can be induced by granule cell spike patterns during a memory task, and that the timing of mfLTP induction can predict task performance.
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Affiliation(s)
- Rajen Mistry
- Medical Research Council Centre for Synaptic Plasticity, Department of Anatomy, University of Bristol, United Kingdom
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39
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Dixon RM, Mellor JR, Hanley JG. PICK1-mediated glutamate receptor subunit 2 (GluR2) trafficking contributes to cell death in oxygen/glucose-deprived hippocampal neurons. J Biol Chem 2009; 284:14230-5. [PMID: 19321442 PMCID: PMC2682871 DOI: 10.1074/jbc.m901203200] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Oxygen and glucose deprivation (OGD) induces delayed cell death in
hippocampal CA1 neurons via Ca2+/Zn2+-permeable,
GluR2-lacking AMPA receptors (AMPARs). Following OGD, synaptic AMPAR currents
in hippocampal neurons show marked inward rectification and increased
sensitivity to channel blockers selective for GluR2-lacking AMPARs. This
occurs via two mechanisms: a delayed down-regulation of GluR2 mRNA expression
and a rapid internalization of GluR2-containing AMPARs during the OGD insult,
which are replaced by GluR2-lacking receptors. The mechanisms that underlie
this rapid change in subunit composition are unknown. Here, we demonstrate
that this trafficking event shares features in common with events that mediate
long term depression and long term potentiation and is initiated by the
activation of N-methyl-d-aspartic acid receptors. Using
biochemical and electrophysiological approaches, we show that peptides that
interfere with PICK1 PDZ domain interactions block the OGD-induced switch in
subunit composition, implicating PICK1 in restricting GluR2 from synapses
during OGD. Furthermore, we show that GluR2-lacking AMPARs that arise at
synapses during OGD as a result of PICK1 PDZ interactions are involved in
OGD-induced delayed cell death. This work demonstrates that PICK1 plays a
crucial role in the response to OGD that results in altered synaptic
transmission and neuronal death and has implications for our understanding of
the molecular mechanisms that underlie cell death during stroke.
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Affiliation(s)
- Rebecca M Dixon
- Medical Research Council (MRC) Centre for Synaptic Plasticity, Department of Anatomy, University of Bristol, University Walk, Bristol BS8 1TD, United Kingdom
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40
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Buchanan KA, Mellor JR. The development of synaptic plasticity induction rules and the requirement for postsynaptic spikes in rat hippocampal CA1 pyramidal neurones. J Physiol 2007; 585:429-45. [PMID: 17932146 DOI: 10.1113/jphysiol.2007.142984] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Coincident pre- and postsynaptic activity induces synaptic plasticity at the Schaffer collateral synapse onto CA1 pyramidal neurones. The precise timing, frequency and number of coincident action potentials required to induce synaptic plasticity is currently unknown. In this study we show that the postsynaptic activity required for the induction of long-term potentiation (LTP) changes with development. In acute slices from adult rats, coincident pre- and postsynaptic theta burst stimulation (TBS) induced LTP and we show that multiple high-frequency postsynaptic spikes are required. In contrast, in acute slices from juvenile (P14) rats, TBS failed to induce LTP unless the excitatory postsynaptic potentials (EPSPs) were of sufficient magnitude to initiate action potentials. We also show that coincident individual pre- and postsynaptic action potentials are only capable of inducing LTP in the juvenile when given at a frequency greater than 5 Hz and that the timing of individual pre- and postsynaptic action potentials relative to one another is not important. Finally, we show that local tetrodotoxin (TTX) application to the soma blocked LTP in adults, but not juveniles. These data demonstrate that somatic spiking is more important for LTP induction in the adult as opposed to juvenile rats and we hypothesize that the basis for this is the ability of action potentials in the postsynaptic CA1 pyramidal neurone to back-propagate into the dendrites. Therefore, the pre- and postsynaptic activity patterns required to induce LTP mature as the hippocampus develops.
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Affiliation(s)
- Katherine A Buchanan
- MRC Centre for Synaptic Plasticity, Department of Anatomy, University of Bristol, University Walk, Bristol BS8 1TD, UK
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41
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Mistry R, Mellor JR. Bidirectional activity-dependent plasticity of membrane potential and the influence on spiking in rat hippocampal dentate granule cells. Neuropharmacology 2007; 54:290-9. [PMID: 17998139 DOI: 10.1016/j.neuropharm.2007.09.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2007] [Revised: 09/26/2007] [Accepted: 09/27/2007] [Indexed: 10/22/2022]
Abstract
Granule cells of the dentate gyrus in the hippocampus generally fire at low frequencies but are known to respond to sensory cues by increasing their rate of firing. We have previously shown that a burst of action potentials in synaptically isolated granule cells can induce a long-term depolarisation (LTDepol) of the neuronal membrane potential. This form of excitability plasticity could be an important mechanism for learning and memory. Here we demonstrate that this depolarisation can be reversed by physiologically relevant firing patterns. At a basal action potential frequency of 0.1Hz the membrane potential depolarises in response to brief high frequency stimulation (HFS) but this depolarisation is blocked or reversed by 1Hz action potential firing. The depolarisation of the neurones did not, however, affect the input-output function of the dentate gyrus measured by field or single cell recordings. HFS or brief forskolin application that mimics LTDepol did not alter the excitatory input-output spike coupling measured using field potential recordings. Similarly, LTDepol did not change the probability of spike firing in response to a given input. The mechanism underlying the lack of change in input-output relationship was found to be a concurrent depolarisation of the threshold potential for the initiation of action potentials. We demonstrate that physiologically relevant patterns of activity regulate the membrane potential of dentate gyrus granule cells in a bidirectional manner but the changes in membrane potential do not alter the excitability of these neurones measured by their response to excitatory inputs.
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Affiliation(s)
- Rajen Mistry
- MRC Centre for Synaptic Plasticity, Department of Anatomy, University of Bristol, University Walk, Bristol BS8 1TD, UK
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Martin S, Nishimune A, Mellor JR, Henley JM. SUMOylation regulates kainate-receptor-mediated synaptic transmission. Nature 2007; 447:321-5. [PMID: 17486098 PMCID: PMC3310901 DOI: 10.1038/nature05736] [Citation(s) in RCA: 230] [Impact Index Per Article: 13.5] [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: 12/18/2006] [Accepted: 03/07/2007] [Indexed: 01/27/2023]
Abstract
The small ubiquitin-like modifier protein (SUMO) regulates transcriptional activity and the translocation of proteins across the nuclear membrane. The identification of SUMO substrates outside the nucleus is progressing but little is yet known about the wider cellular role of protein SUMOylation. Here we report that in rat hippocampal neurons multiple SUMOylation targets are present at synapses and we show that the kainate receptor subunit GluR6 is a SUMO substrate. SUMOylation of GluR6 regulates endocytosis of the kainate receptor and modifies synaptic transmission. GluR6 exhibits low levels of SUMOylation under resting conditions and is rapidly SUMOylated in response to a kainate but not an N-methyl-D-aspartate (NMDA) treatment. Reducing GluR6 SUMOylation using the SUMO-specific isopeptidase SENP-1 prevents kainate-evoked endocytosis of the kainate receptor. Furthermore, a mutated non-SUMOylatable form of GluR6 is not endocytosed in response to kainate in COS-7 cells. Consistent with this, electrophysiological recordings in hippocampal slices demonstrate that kainate-receptor-mediated excitatory postsynaptic currents are decreased by SUMOylation and enhanced by deSUMOylation. These data reveal a previously unsuspected role for SUMO in the regulation of synaptic function.
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Affiliation(s)
- Stéphane Martin
- MRC Centre for Synaptic Plasticity, Anatomy Department, University Walk, University of Bristol, Bristol, BS8 1TD, UK
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43
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Abstract
Synaptic plasticity of ionotropic glutamate receptors has been extensively studied with a particular focus on the role played by NMDA (N-methyl-D-aspartate) receptors in the induction of synaptic plasticity and the subsequent movement of AMPA (alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) receptors. The third subtype of ionotropic glutamate receptor, kainate receptors, has not been studied to the same extent, but recent evidence shows that these receptors also exhibit synaptic plasticity in response to activity. There is also a growing body of data on the mechanisms underlying kainate receptor trafficking and the proteins they interact with. This review summarizes the current state of knowledge on this topic, focusing on the evidence for the removal or insertion of functional kainate receptors in response to synaptic activity and the cellular mechanisms that underlie this regulation of neuronal kainate receptor function.
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Affiliation(s)
- J R Mellor
- MRC Centre for Synaptic Plasticity, Department of Anatomy, University of Bristol, Bristol BS8 1TD, UK.
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44
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Nishimune A, Martin S, Mellor JR, Henley JM. SUMOylation regulates kainate receptor-mediated synaptic transmission. Neurosci Res 2007. [DOI: 10.1016/j.neures.2007.06.242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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45
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Abstract
GABA concentration jump experiments performed on membrane patches predict that postsynaptic GABAAreceptors will become desensitized following the release of the contents of a single GABA-containing synaptic vesicle. To examine this we used a single synaptic bouton stimulation technique to directly examine whether postsynaptic GABAA receptors in cultured cerebellar granule cells exhibit transmitter-induced desensitization. In a large number of recordings, no evidence was found for desensitization of postsynaptic GABAAreceptors by vesicularly released transmitter. This was the case even when as many as 40 vesicles were released from a single bouton within 1.5 s. In addition, postsynaptic depolarization and application of the benzodiazepine flunitrazepam, manipulations previously shown to enhance desensitization of GABAA receptors, failed to unmask transmitter-induced desensitization. In contrast, a single 2- to 3-s application of a high concentration of exogenous GABA was able to depress synaptic responsiveness for up to 70 s. Furthermore, pharmacological depletion of GABA eliminated inhibitory synaptic communication, suggesting that GABA is the transmitter and the desensitization-resistant inhibitory postsynaptic currents are not mediated by a “nondesensitizing” ligand such as β-alanine. Overall our data indicate that a specific desensitization-resistant population of GABAA receptors are present at postsynaptic sites on cultured cerebellar granule cells.
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Affiliation(s)
- J R Mellor
- Neurobiology Division, Medical Research Council, Laboratory of Molecular Biology, Cambridge CB2 2QH, United Kingdom
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46
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Mellor JR, Wisden W, Randall AD. Somato-synaptic variation of GABA(A) receptors in cultured murine cerebellar granule cells: investigation of the role of the alpha6 subunit. Neuropharmacology 2000; 39:1495-513. [PMID: 10854895 DOI: 10.1016/s0028-3908(00)00007-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [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: 11/25/2022]
Abstract
Electrophysiological investigation of cultured cerebellar murine granule cells revealed differences between the GABA(A) receptors at inhibitory synapses and those on the cell body. Specifically, mIPSCs decayed more rapidly than cell body receptors deactivated, the mean single channel conductance at the synapse (32 pS) was greater than that at cell body (21 pS) and only cell body receptors were sensitive to Zn(2+) (150 microM), which depressed response amplitude by 82+/-5% and almost doubled the rate of channel deactivation. The GABA(A) receptor alpha6 subunit is selectively expressed in cerebellar granule cells. Although concentrated at synapses, it is also found on extrasynaptic membranes. Using a mouse line (Deltaalpha6lacZ) lacking this subunit, we investigated its role in the somato-synaptic differences in GABA(A) receptor function. All differences between cell body and synaptic GABA(A) receptors observed in wild-type (WT) granule cells persisted in Deltaalpha6lacZ cells, thus demonstrating that they are not specifically due to the cellular distribution of the alpha6 subunit. However, mIPSCs from WT and Deltaalpha6lacZ cells differed in both their kinetics (faster decay in WT cells) and underlying single channel conductance (32 pS WT, 25 pS Deltaalpha6lacZ). This provides good evidence for a functional contribution of the alpha6 subunit to postsynaptic GABA(A) receptors in these cells. Despite this, deactivation kinetics of mIPSCs in WT and Deltaalpha6lacZ granule cells exhibited similar benzodiazepene (BDZ) sensitivity. This suggests that the enhanced BDZ-induced ataxia seen in Deltaalpha6lacZ mice may reflect physiological activity at extrasynaptic receptors which, unlike those at synapses, display differential BDZ-sensitivity in WT and Deltaalpha6lacZ granule cells (Jones, A.M., Korpi, E.R., McKernan, R.M., Nusser, Z., Pelz, R., Makela, R., Mellor, J.R., Pollard, S., Bahn, S., Stephenson, F.A., Randall, A.D., Sieghart, W., Somogyi, P., Smith, A.J.H., Wisden, W., 1997. Ligand-gated ion channel partnerships: GABA(A) receptor alpha(6) subunit inactivation inhibits delta subunit expression. Journal of Neuroscience 17, 1350-1362).
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Affiliation(s)
- J R Mellor
- Division of Neurobiology, MRC Laboratory of Molecular Biology, Hills Road, CB2 2QH, Cambridge, UK
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Mellor JR, Gunthorpe MJ, Randall AD. The taurine uptake inhibitor guanidinoethyl sulphonate is an agonist at gamma-aminobutyric acid(A) receptors in cultured murine cerebellar granule cells. Neurosci Lett 2000; 286:25-8. [PMID: 10822144 DOI: 10.1016/s0304-3940(00)01082-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [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: 11/17/2022]
Abstract
In patch clamp experiments the beta-amino acid uptake inhibitor guanidinoethyl sulphonate (GES) activated currents in intact cultured murine cerebellar granule neurones. These responses could be attenuated by the gamma-aminobutyric acid(A) (GABA(A)) receptor antagonists bicuculline and picrotoxin. With intracellular chloride concentrations of either 20 or 130 mM, GES-induced current responses reversed polarity near the chloride equilibrium potential. When fast applications of agonist were made to excised granule cell macropatches GES responses were dose-dependent and exhibited significant outward rectification. Like taurine (but unlike GABA and beta-alanine) responses, macroscopic desensitisation of GES-induced currents was slow. Our data indicate that care should be exercised when using GES as a taurine uptake inhibitor in systems that also contain GABA(A) receptors.
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Affiliation(s)
- J R Mellor
- Neuroscience Research, SmithKline Beecham Pharmaceuticals, Third Avenue, Essex, CM19 5AW, Harlow, UK
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Abstract
Recent studies have demonstrated that granule cells in rat cerebellar slices exhibit a tonic form of GABAergic inhibition. The presence of a similar constitutive GABAergic conductance was investigated in synaptically coupled cultures of neonatal rat cerebellum. In cells exhibiting spontaneous inhibitory postsynaptic currents (IPSCs), application of the GABA(A) receptor antagonist bicuculline (10 microM) eliminated the IPSCs and also produced a significant decrease in holding current. This latter effect was lacking in cells that did not exhibit IPSCs. Application of TTX (1 microM) and Cd(2+) (100 microM) decreased the IPSC frequency and also produced a change in holding current; these effects were eliminated by the prior application of bicuculline. In the presence of TTX, application of the benzodiazepine (BDZ) Flunitrazepam (1 microM) caused a 85+/-15% increase in the component of holding current that arose from GABA(A) receptor activity. Noise analysis indicated that the GABA(A) receptors underlying this tonic form of GABAergic inhibition exhibited a mean single channel conductance close to 14 pS, a value similar to that seen for somatic GABA(A) receptors in these cells. Thus, like their counterparts in cerebellar slices, cerebellar granule cells in culture exhibit a background GABAergic conductance. The most likely source of this tonic current is GABA spilt over from active inhibitory synapses. As this conductance was sensitive to benzodiazepine receptor agonists it is unlikely to arise entirely from GABA(A) receptors containing the alpha6 subunit.
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Affiliation(s)
- R M Leao
- Division of Neurobiology, MRC Laboratory of Molecular Biology, Hills Road, Cambridge, UK
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Abstract
We have studied the properties of GABA responses in oligodendrocyte-type 2 astrocyte (O-2A) progenitor cells derived from primary cultures of the neonatal rat brain. In whole cell voltage clamp recordings, rapid application of 1-10 mM GABA elicited current responses in > 85% of the cells examined. The dose-response relationship pooled from nine progenitor cells was best fit by a logistic function of EC50=113 microM and Hill coefficient=0.9. In contrast to the rate of current deactivation, the rate of current activation exhibited marked concentration-dependence. Pharmacologically, GABA, muscimol and ZAPA ((Z)-3[(aminiiminomethyl)thio]prop-2-enoic acid sulphate) produced responses with ligand-specific kinetics, whereas glycine and the GABA(C) receptor agonist CACA were without effect; bicuculline methochloride acted as a competitive antagonist. Neither the amplitude nor the kinetics of currents produced by 100 microM GABA were affected by the benzodiazepine flunitrazepam (1 microM). Similarly the benzodiazepine receptor inverse agonist DMCM (1 microM) was also without effect. GABA-activated currents reversed polarity within 2 mV of the calculated Cl- equilibrium potential. With brief agonist pulses deactivation was monoexponential, however, unlike neurones the rate of deactivation was voltage-independent. Desensitisation of responses to 10 mM GABA was bi-exponential and accelerated at depolarised membrane potentials. Increasing the amount of GABA(A) receptor desensitisation (by increasing the duration of the agonist exposure) consistently produced a slowing of deactivation.
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Affiliation(s)
- A V Williamson
- MRC Laboratory of Molecular Biology, Division of Neurobiology, Cambridge, UK
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Mellor JR, Merlo D, Jones A, Wisden W, Randall AD. Mouse cerebellar granule cell differentiation: electrical activity regulates the GABAA receptor alpha 6 subunit gene. J Neurosci 1998; 18:2822-33. [PMID: 9525999 PMCID: PMC6792580] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
GABAA receptor alpha6 subunit gene expression marks cerebellar granule cell maturation. To study this process, we used the Deltaalpha6lacZ mouse line, which has a lacZ reporter inserted into the alpha6 gene. At early stages of postnatal cerebellar development, alpha6-lacZ expression is mosaic; expression starts at postnatal day 5 in lobules 9 and 10, and alpha6-lacZ is switched on inside-out, appearing first in the deepest postmigratory granule cells. We looked for factors regulating this expression in cell culture. Membrane depolarization correlates inversely with alpha6-lacZ expression: granule cells grown in 25 mM [K+]o for 11-15 d do not express the alpha6 gene, whereas cultures grown for the same period in 5 mM [K+]o do. This is influenced by a critical early period: culturing for >/=3 d in 25 mM [K+]o curtails the ability to induce the alpha6 gene on transfer to 5 mM [K+]o. If the cells start in 5 mM [K+]o, however, they still express the alpha6-lacZ gene in 25 mM [K+]o. In contrast to granule cells grown in 5 mM [K+]o, cells cultured in 25 mM [K+]o exhibit no action potentials, mEPSCs, or mIPSCs. In chronic 5 mM [K+]o, factors may therefore be released that induce alpha6. Blockade of ionotropic and metabotropic GABA and glutamate receptors or L-, N-, and P/Q-type Ca2+ channels did not prevent alpha6-lacZ expression, but inhibition of action potentials with tetrodotoxin blocked expression in a subpopulation of cells.
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Affiliation(s)
- J R Mellor
- Medical Research Council Laboratory of Molecular Biology, Cambridge, CB2 2QH, United Kingdom
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