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Gómez-Gonzalo M, Navarrete M, Perea G, Covelo A, Martín-Fernández M, Shigemoto R, Luján R, Araque A. Endocannabinoids Induce Lateral Long-Term Potentiation of Transmitter Release by Stimulation of Gliotransmission. Cereb Cortex 2014; 25:3699-712. [PMID: 25260706 DOI: 10.1093/cercor/bhu231] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Endocannabinoids (eCBs) play key roles in brain function, acting as modulatory signals in synaptic transmission and plasticity. They are recognized as retrograde messengers that mediate long-term synaptic depression (LTD), but their ability to induce long-term potentiation (LTP) is poorly known. We show that eCBs induce the long-term enhancement of transmitter release at single hippocampal synapses through stimulation of astrocytes when coincident with postsynaptic activity. This LTP requires the coordinated activity of the 3 elements of the tripartite synapse: 1) eCB-evoked astrocyte calcium signal that stimulates glutamate release; 2) postsynaptic nitric oxide production; and 3) activation of protein kinase C and presynaptic group I metabotropic glutamate receptors, whose location at presynaptic sites was confirmed by immunoelectron microscopy. Hence, while eCBs act as retrograde signals to depress homoneuronal synapses, they serve as lateral messengers to induce LTP in distant heteroneuronal synapses through stimulation of astrocytes. Therefore, eCBs can trigger LTP through stimulation of astrocyte-neuron signaling, revealing novel cellular mechanisms of eCB effects on synaptic plasticity.
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Affiliation(s)
| | - Marta Navarrete
- Instituto Cajal, CSIC, Madrid 28002, Spain Current address: Department of Neurobiology, Centro de Biología Molecular "Severo Ochoa," (CSIC/UAM), Madrid, Spain
| | | | - Ana Covelo
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | | | - Ryuichi Shigemoto
- Division of Cerebral Structure, National Institute for Physiological Sciences, Okazaki 444-8787, Japan
| | - Rafael Luján
- Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Albacete 02006, Spain
| | - Alfonso Araque
- Instituto Cajal, CSIC, Madrid 28002, Spain Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
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52
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Pankratov Y, Lalo U. Calcium permeability of ligand-gated Ca2+ channels. Eur J Pharmacol 2014; 739:60-73. [DOI: 10.1016/j.ejphar.2013.11.017] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 10/22/2013] [Accepted: 11/07/2013] [Indexed: 11/28/2022]
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Perin M, Longordo F, Massonnet C, Welker E, Lüthi A. Diurnal inhibition of NMDA-EPSCs at rat hippocampal mossy fibre synapses through orexin-2 receptors. J Physiol 2014; 592:4277-95. [PMID: 25085886 DOI: 10.1113/jphysiol.2014.272757] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Diurnal release of the orexin neuropeptides orexin-A (Ox-A, hypocretin-1) and orexin-B (Ox-B, hypocretin-2) stabilises arousal, regulates energy homeostasis and contributes to cognition and learning. However, whether cellular correlates of brain plasticity are regulated through orexins, and whether they do so in a time-of-day-dependent manner, has never been assessed. Immunohistochemically we found sparse but widespread innervation of hippocampal subfields through Ox-A- and Ox-B-containing fibres in young adult rats. The actions of Ox-A were studied on NMDA receptor (NMDAR)-mediated excitatory synaptic transmission in acute hippocampal slices prepared around the trough (Zeitgeber time (ZT) 4-8, corresponding to 4-8 h into the resting phase) and peak (ZT 23) of intracerebroventricular orexin levels. At ZT 4-8, exogenous Ox-A (100 nm in bath) inhibited NMDA receptor-mediated excitatory postsynaptic currents (NMDA-EPSCs) at mossy fibre (MF)-CA3 (to 55.6 ± 6.8% of control, P = 0.0003) and at Schaffer collateral-CA1 synapses (70.8 ± 6.3%, P = 0.013), whereas it remained ineffective at non-MF excitatory synapses in CA3. Ox-A actions were mediated postsynaptically and blocked by the orexin-2 receptor (OX2R) antagonist JNJ10397049 (1 μm), but not by orexin-1 receptor inhibition (SB334867, 1 μm) or by adrenergic and cholinergic antagonists. At ZT 23, inhibitory effects of exogenous Ox-A were absent (97.6 ± 2.9%, P = 0.42), but reinstated (87.2 ± 3.3%, P = 0.002) when endogenous orexin signalling was attenuated for 5 h through i.p. injections of almorexant (100 mg kg(-1)), a dual orexin receptor antagonist. In conclusion, endogenous orexins modulate hippocampal NMDAR function in a time-of-day-dependent manner, suggesting that they may influence cellular plasticity and consequent variations in memory performance across the sleep-wake cycle.
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Affiliation(s)
- Martina Perin
- Department of Fundamental Neurosciences, University of Lausanne, Rue du Bugnon 9, CH-1005, Lausanne, Switzerland
| | - Fabio Longordo
- Department of Fundamental Neurosciences, University of Lausanne, Rue du Bugnon 9, CH-1005, Lausanne, Switzerland
| | - Christine Massonnet
- Department of Fundamental Neurosciences, University of Lausanne, Rue du Bugnon 9, CH-1005, Lausanne, Switzerland
| | - Egbert Welker
- Department of Fundamental Neurosciences, University of Lausanne, Rue du Bugnon 9, CH-1005, Lausanne, Switzerland
| | - Anita Lüthi
- Department of Fundamental Neurosciences, University of Lausanne, Rue du Bugnon 9, CH-1005, Lausanne, Switzerland
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Critical role of canonical transient receptor potential channel 7 in initiation of seizures. Proc Natl Acad Sci U S A 2014; 111:11533-8. [PMID: 25049394 DOI: 10.1073/pnas.1411442111] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Status epilepticus (SE) is a life-threatening disease that has been recognized since antiquity but still causes over 50,000 deaths annually in the United States. The prevailing view on the pathophysiology of SE is that it is sustained by a loss of normal inhibitory mechanisms of neuronal activity. However, the early process leading to the initiation of SE is not well understood. Here, we show that, as seen in electroencephalograms, SE induced by the muscarinic agonist pilocarpine in mice is preceded by a specific increase in the gamma wave, and genetic ablation of canonical transient receptor potential channel (TRPC) 7 significantly reduces this pilocarpine-induced increase of gamma wave activity, preventing the occurrence of SE. At the cellular level, TRPC7 plays a critical role in the generation of spontaneous epileptiform burst firing in cornu ammonis (CA) 3 pyramidal neurons in brain slices. At the synaptic level, TRPC7 plays a significant role in the long-term potentiation at the CA3 recurrent collateral synapses and Schaffer collateral-CA1 synapses, but not at the mossy fiber-CA3 synapses. Taken together, our data suggest that epileptiform burst firing generated in the CA3 region by activity-dependent enhancement of recurrent collateral synapses may be an early event in the initiation process of SE and that TRPC7 plays a critical role in this cellular event. Our findings reveal that TRPC7 is intimately involved in the initiation of seizures both in vitro and in vivo. To our knowledge, this contribution to initiation of seizures is the first identified functional role for the TRPC7 ion channel.
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Unlearning: NMDA receptor-mediated metaplasticity in the anterior piriform cortex following early odor preference training in rats. J Neurosci 2014; 34:5143-51. [PMID: 24719094 DOI: 10.1523/jneurosci.0128-14.2014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Here we demonstrate metaplastic effect of a change in NMDA receptor (NMDAR) number in the anterior piriform cortex (aPC) in rat induced by a 10 min pairing of peppermint odor + stroking, which significantly modifies later learning and memory. Using isolated synaptoneurosomes, we found NR1 receptor downregulation 3 h after training and upregulation at 24 h. Consistent with the NR1 pattern, the NMDAR-mediated EPSP was smaller at 3 h and larger at 24 h. Subunit composition was unchanged. Whereas LTP was reduced at both times by training, LTD was facilitated only at 3 h. Behaviorally, pups, given a pairing of peppermint + stroking 3 h after an initial peppermint + stroking training, lost the normally acquired peppermint preference 24 h later. To probe the pathway specificity of this unlearning effect, pups were trained first with peppermint and then, at 3 h, given a second training with peppermint or vanillin. Pups given peppermint training at both times lost the learned peppermint preference. Pups given vanillin retraining at 3 h had normal peppermint preference. Downregulating NR1 with siRNA prevented odor preference learning. Finally, the NMDAR antagonist MK-801 blocked the LTD facilitation seen 3 h after training, and giving MK-801 before the second peppermint training trial eliminated the loss of peppermint odor preference. A training-associated reduction in NMDARs facilitates LTD 3 h later; training at the time of LTD facilitation reverses an LTP-dependent odor preference. Experience-dependent, pathway-specific metaplastic effects in a cortical structure have broad implications for the optimal spacing of learning experiences.
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56
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Weiss S, Mori F, Rossi S, Centonze D. Disability in multiple sclerosis: When synaptic long-term potentiation fails. Neurosci Biobehav Rev 2014; 43:88-99. [DOI: 10.1016/j.neubiorev.2014.03.023] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Revised: 02/11/2014] [Accepted: 03/31/2014] [Indexed: 12/13/2022]
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Ceccom J, Halley H, Daumas S, Lassalle JM. A specific role for hippocampal mossy fiber's zinc in rapid storage of emotional memories. Learn Mem 2014; 21:287-97. [PMID: 24741109 PMCID: PMC3994499 DOI: 10.1101/lm.033472.113] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
We investigated the specific role of zinc present in large amounts in the synaptic vesicles of mossy fibers and coreleased with glutamate in the CA3 region. In previous studies, we have shown that blockade of zinc after release has no effect on the consolidation of spatial learning, while zinc is required for the consolidation of contextual fear conditioning. Although both are hippocampo-dependent processes, fear conditioning to the context implies a strong emotional burden. To verify the hypothesis that zinc could play a specific role in enabling sustainable memorization of a single event with a strong emotional component, we used a neuropharmacological approach combining a glutamate receptor antagonist with different zinc chelators. Results show that zinc is mandatory to allow the consolidation of one-shot memory, thus being the key element allowing the hippocampus submitted to a strong emotional charge to switch from the cognitive mode to a flashbulb memory mode. Individual differences in learning abilities have been known for a long time to be totally or partially compensated by distributed learning practice. Here we show that contextual fear conditioning impairments due to zinc blockade can be efficiently reduced by distributed learning practice.
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Affiliation(s)
- Johnatan Ceccom
- Université de Toulouse, UPS, Centre de Recherches sur la Cognition Animale, F-31062 Toulouse Cedex 9, France
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59
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Dupuis JP, Ladépêche L, Seth H, Bard L, Varela J, Mikasova L, Bouchet D, Rogemond V, Honnorat J, Hanse E, Groc L. Surface dynamics of GluN2B-NMDA receptors controls plasticity of maturing glutamate synapses. EMBO J 2014; 33:842-61. [PMID: 24591565 DOI: 10.1002/embj.201386356] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
NMDA-type glutamate receptors (NMDAR) are central actors in the plasticity of excitatory synapses. During adaptive processes, the number and composition of synaptic NMDAR can be rapidly modified, as in neonatal hippocampal synapses where a switch from predominant GluN2B- to GluN2A-containing receptors is observed after the induction of long-term potentiation (LTP). However, the cellular pathways by which surface NMDAR subtypes are dynamically regulated during activity-dependent synaptic adaptations remain poorly understood. Using a combination of high-resolution single nanoparticle imaging and electrophysiology, we show here that GluN2B-NMDAR are dynamically redistributed away from glutamate synapses through increased lateral diffusion during LTP in immature neurons. Strikingly, preventing this activity-dependent GluN2B-NMDAR surface redistribution through cross-linking, either with commercial or with autoimmune anti-NMDA antibodies from patient with neuropsychiatric symptoms, affects the dynamics and spine accumulation of CaMKII and impairs LTP. Interestingly, the same impairments are observed when expressing a mutant of GluN2B-NMDAR unable to bind CaMKII. We thus uncover a non-canonical mechanism by which GluN2B-NMDAR surface dynamics plays a critical role in the plasticity of maturing synapses through a direct interplay with CaMKII.
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Affiliation(s)
- Julien P Dupuis
- Interdisciplinary Institute for Neuroscience University de Bordeaux UMR 5297, Bordeaux, France
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60
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Evstratova A, Tóth K. Information processing and synaptic plasticity at hippocampal mossy fiber terminals. Front Cell Neurosci 2014; 8:28. [PMID: 24550783 PMCID: PMC3912358 DOI: 10.3389/fncel.2014.00028] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Accepted: 01/20/2014] [Indexed: 11/13/2022] Open
Abstract
Granule cells of the dentate gyrus receive cortical information and they transform and transmit this code to the CA3 area via their axons, the mossy fibers (MFs). Structural and functional complexity of this network has been extensively studied at various organizational levels. This review is focused on the anatomical and physiological properties of the MF system. We will discuss the mechanism by which dentate granule cells process signals from single action potentials (APs), short bursts and longer stimuli. Various parameters of synaptic interactions at different target cells such as quantal transmission, short- and long-term plasticity (LTP) will be summarized. Different types of synaptic contacts formed by MFs have unique sets of rules for information processing during different rates of granule cell activity. We will investigate the complex interactions between key determinants of information transfer between the dentate gyrus and the CA3 area of the hippocampus.
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Affiliation(s)
- Alesya Evstratova
- Faculty of Medicine, Department of Psychiatry and Neuroscience, Quebec Mental Health Institute, Université Laval Quebec City, QC, Canada
| | - Katalin Tóth
- Faculty of Medicine, Department of Psychiatry and Neuroscience, Quebec Mental Health Institute, Université Laval Quebec City, QC, Canada
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61
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Soluble pathological tau in the entorhinal cortex leads to presynaptic deficits in an early Alzheimer's disease model. Acta Neuropathol 2014; 127:257-70. [PMID: 24271788 DOI: 10.1007/s00401-013-1215-5] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Revised: 10/28/2013] [Accepted: 11/09/2013] [Indexed: 10/26/2022]
Abstract
Neurofibrillary tangles (NFTs), a hallmark of Alzheimer's disease, are intracellular silver and thioflavin S-staining aggregates that emerge from earlier accumulation of phospho-tau in the soma. Whether soluble misfolded but nonfibrillar tau disrupts neuronal function is unclear. Here we investigate if soluble pathological tau, specifically directed to the entorhinal cortex (EC), can cause behavioral or synaptic deficits. We studied rTgTauEC transgenic mice, in which P301L mutant human tau overexpressed primarily in the EC leads to the development of tau pathology, but only rare NFT at 16 months of age. We show that the early tau lesions are associated with nearly normal performance in contextual fear conditioning, a hippocampal-related behavior task, but more robust changes in neuronal system activation as marked by Arc induction and clear electrophysiological defects in perforant pathway synaptic plasticity. Electrophysiological changes were likely due to a presynaptic deficit and changes in probability of neurotransmitter release. The data presented here support the hypothesis that misfolded and hyperphosphorylated tau can impair neuronal function within the entorhinal-hippocampal network, even prior to frank NFT formation and overt neurodegeneration.
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62
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Tang R, Dai J. Spatiotemporal imaging of glutamate-induced biophotonic activities and transmission in neural circuits. PLoS One 2014; 9:e85643. [PMID: 24454909 PMCID: PMC3893221 DOI: 10.1371/journal.pone.0085643] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Accepted: 11/29/2013] [Indexed: 11/18/2022] Open
Abstract
The processing of neural information in neural circuits plays key roles in neural functions. Biophotons, also called ultra-weak photon emissions (UPE), may play potential roles in neural signal transmission, contributing to the understanding of the high functions of nervous system such as vision, learning and memory, cognition and consciousness. However, the experimental analysis of biophotonic activities (emissions) in neural circuits has been hampered due to technical limitations. Here by developing and optimizing an in vitro biophoton imaging method, we characterize the spatiotemporal biophotonic activities and transmission in mouse brain slices. We show that the long-lasting application of glutamate to coronal brain slices produces a gradual and significant increase of biophotonic activities and achieves the maximal effect within approximately 90 min, which then lasts for a relatively long time (>200 min). The initiation and/or maintenance of biophotonic activities by glutamate can be significantly blocked by oxygen and glucose deprivation, together with the application of a cytochrome c oxidase inhibitor (sodium azide), but only partly by an action potential inhibitor (TTX), an anesthetic (procaine), or the removal of intracellular and extracellular Ca(2+). We also show that the detected biophotonic activities in the corpus callosum and thalamus in sagittal brain slices mostly originate from axons or axonal terminals of cortical projection neurons, and that the hyperphosphorylation of microtubule-associated protein tau leads to a significant decrease of biophotonic activities in these two areas. Furthermore, the application of glutamate in the hippocampal dentate gyrus results in increased biophotonic activities in its intrahippocampal projection areas. These results suggest that the glutamate-induced biophotonic activities reflect biophotonic transmission along the axons and in neural circuits, which may be a new mechanism for the processing of neural information.
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Affiliation(s)
- Rendong Tang
- Wuhan Institute for Neuroscience and Neuroengineering, South-Central University for Nationalities, Wuhan, China
- College of Biomedical Engineering, South-Central University for Nationalities, Wuhan, China
| | - Jiapei Dai
- Wuhan Institute for Neuroscience and Neuroengineering, South-Central University for Nationalities, Wuhan, China
- College of Biomedical Engineering, South-Central University for Nationalities, Wuhan, China
- Department of Pharmacology, College of Pharmacy, South-Central University for Nationalities, Wuhan, China
- * E-mail:
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63
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Yuan T, Mameli M, O'Connor EC, O' Connor EC, Dey PN, Verpelli C, Sala C, Perez-Otano I, Lüscher C, Bellone C. Expression of cocaine-evoked synaptic plasticity by GluN3A-containing NMDA receptors. Neuron 2013; 80:1025-38. [PMID: 24183704 DOI: 10.1016/j.neuron.2013.07.050] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/30/2013] [Indexed: 12/27/2022]
Abstract
Drug-evoked synaptic plasticity in the mesolimbic dopamine (DA) system reorganizes neural circuits that may lead to addictive behavior. The first cocaine exposure potentiates AMPAR excitatory postsynaptic currents (EPSCs) onto DA neurons of the VTA but reduces the amplitude of NMDAR-EPSCs. While plasticity of AMPAR transmission is expressed by insertion of calcium (Ca(2+))-permeable GluA2-lacking receptors, little is known about the expression mechanism for altered NMDAR transmission. Combining ex vivo patch-clamp recordings, mouse genetics, and subcellular Ca(2+) imaging, we observe that cocaine drives the insertion of NMDARs that are quasi-Ca(2+)-impermeable and contain GluN3A and GluN2B subunits. These GluN3A-containing NMDARs appear necessary for the expression of cocaine-evoked plasticity of AMPARs. We identify an mGluR1-dependent mechanism to remove these noncanonical NMDARs that requires Homer/Shank interaction and protein synthesis. Our data provide insight into the early cocaine-driven reorganization of glutamatergic transmission onto DA neurons and offer GluN3A-containing NMDARs as new targets in drug addiction.
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Affiliation(s)
- Tifei Yuan
- Department of Basic Neurosciences, Medical Faculty, University of Geneva, 1 rue Michel Servet, CH-1211 Geneva, Switzerland
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64
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Ladépêche L, Dupuis JP, Groc L. Surface trafficking of NMDA receptors: gathering from a partner to another. Semin Cell Dev Biol 2013; 27:3-13. [PMID: 24177014 DOI: 10.1016/j.semcdb.2013.10.005] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 10/11/2013] [Accepted: 10/22/2013] [Indexed: 10/26/2022]
Abstract
Understanding the molecular and cellular pathways by which neurons integrate signals from different neurotransmitter systems has been among the major challenges of modern neuroscience. The ionotropic glutamate NMDA receptor plays a key role in the maturation and plasticity of glutamate synapses, both in physiology and pathology. It recently appeared that the surface distribution of NMDA receptors is dynamically regulated through lateral diffusion, providing for instance a powerful way to rapidly affect the content and composition of synaptic receptors. The ability of various neuromodulators to regulate NMDA receptor signaling revealed that this receptor can also serve as a molecular integrator of the ambient neuronal environment. Although still in its infancy, we here review our current understanding of the cellular regulation of NMDA receptor surface dynamics. We specifically discuss the roles of well-known modulators, such as dopamine, and membrane interactors in these regulatory processes, exemplifying the recent evidence that the direct interaction between NMDAR and dopamine receptors regulates their surface diffusion and distribution. In addition to the well-established modulation of NMDA receptor signaling by intracellular pathways, the surface dynamics of the receptor is now emerging as the first level of regulation, opening new pathophysiological perspectives for innovative therapeutical strategies.
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Affiliation(s)
- Laurent Ladépêche
- Université de Bordeaux, Interdisciplinary Institute for Neuroscience, UMR 5297, F-33000 Bordeaux, France; CNRS, Interdisciplinary Institute for Neuroscience, UMR 5297, F-33000 Bordeaux, France
| | - Julien Pierre Dupuis
- Université de Bordeaux, Interdisciplinary Institute for Neuroscience, UMR 5297, F-33000 Bordeaux, France; CNRS, Interdisciplinary Institute for Neuroscience, UMR 5297, F-33000 Bordeaux, France
| | - Laurent Groc
- Université de Bordeaux, Interdisciplinary Institute for Neuroscience, UMR 5297, F-33000 Bordeaux, France; CNRS, Interdisciplinary Institute for Neuroscience, UMR 5297, F-33000 Bordeaux, France.
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65
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Yang Y, Calakos N. Presynaptic long-term plasticity. Front Synaptic Neurosci 2013; 5:8. [PMID: 24146648 PMCID: PMC3797957 DOI: 10.3389/fnsyn.2013.00008] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Accepted: 09/09/2013] [Indexed: 01/01/2023] Open
Abstract
Long-term synaptic plasticity is a major cellular substrate for learning, memory, and behavioral adaptation. Although early examples of long-term synaptic plasticity described a mechanism by which postsynaptic signal transduction was potentiated, it is now apparent that there is a vast array of mechanisms for long-term synaptic plasticity that involve modifications to either or both the presynaptic terminal and postsynaptic site. In this article, we discuss current and evolving approaches to identify presynaptic mechanisms as well as discuss their limitations. We next provide examples of the diverse circuits in which presynaptic forms of long-term synaptic plasticity have been described and discuss the potential contribution this form of plasticity might add to circuit function. Finally, we examine the present evidence for the molecular pathways and cellular events underlying presynaptic long-term synaptic plasticity.
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Affiliation(s)
- Ying Yang
- Department of Pediatrics, Stanford University School of Medicine Stanford, CA, USA
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66
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Schildt S, Endres T, Lessmann V, Edelmann E. Acute and chronic interference with BDNF/TrkB-signaling impair LTP selectively at mossy fiber synapses in the CA3 region of mouse hippocampus. Neuropharmacology 2013; 71:247-54. [DOI: 10.1016/j.neuropharm.2013.03.041] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2012] [Revised: 02/27/2013] [Accepted: 03/01/2013] [Indexed: 11/27/2022]
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67
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Long-term depression of synaptic kainate receptors reduces excitability by relieving inhibition of the slow afterhyperpolarization. J Neurosci 2013; 33:9536-45. [PMID: 23719820 DOI: 10.1523/jneurosci.0034-13.2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Kainate receptors (KARs) are ionotropic glutamate receptors that also activate noncanonical G-protein-coupled signaling pathways to depress the slow afterhyperpolarization (sAHP). Here we show that long-term depression of KAR-mediated synaptic transmission (KAR LTD) at rat hippocampal mossy fiber synapses relieves inhibition of the sAHP by synaptic transmission. KAR LTD is induced by high-frequency mossy fiber stimulation and natural spike patterns and requires activation of adenosine A2A receptors. Natural spike patterns also cause long-term potentiation of NMDA receptor-mediated synaptic transmission that overrides the effects of KAR LTD on the cellular response to low-frequency synaptic input. However, KAR LTD is dominant at higher frequency synaptic stimulation where it decreases the cellular response by relieving inhibition of the sAHP. Thus we describe a form of glutamate receptor plasticity induced by natural spike patterns whose primary physiological function is to regulate cellular excitability.
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68
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Hunt DL, Puente N, Grandes P, Castillo PE. Bidirectional NMDA receptor plasticity controls CA3 output and heterosynaptic metaplasticity. Nat Neurosci 2013; 16:1049-59. [PMID: 23852115 PMCID: PMC3740388 DOI: 10.1038/nn.3461] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2012] [Accepted: 06/11/2013] [Indexed: 12/31/2022]
Abstract
NMDA receptors (NMDARs) are classically known as coincidence detectors for the induction of long-term synaptic plasticity and have been implicated in hippocampal CA3 cell-dependent spatial memory functions that likely rely on dynamic cellular ensemble encoding of space. The unique functional properties of both NMDARs and mossy fiber projections to CA3 pyramidal cells place mossy fiber NMDARs in a prime position to influence CA3 ensemble dynamics. By mimicking presynaptic and postsynaptic activity patterns observed in vivo, we found a burst timing-dependent pattern of activity that triggered bidirectional long-term NMDAR plasticity at mossy fiber-CA3 synapses in rat hippocampal slices. This form of plasticity imparts bimodal control of mossy fiber-driven CA3 burst firing and spike temporal fidelity. Moreover, we found that mossy fiber NMDARs mediate heterosynaptic metaplasticity between mossy fiber and associational-commissural synapses. Thus, bidirectional NMDAR plasticity at mossy fiber-CA3 synapses could substantially contribute to the formation, storage and recall of CA3 cell assembly patterns.
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Affiliation(s)
- David L Hunt
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, USA
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69
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Ceccom J, Bouhsira E, Halley H, Daumas S, Lassalle JM. Differential needs of zinc in the CA3 area of dorsal hippocampus for the consolidation of contextual fear and spatial memories. Learn Mem 2013; 20:348-51. [PMID: 23772088 DOI: 10.1101/lm.029017.112] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
One peculiarity of the hippocampal CA3 mossy fiber terminals is the co-release of zinc and glutamate upon synaptic transmission. How these two players act on hippocampal-dependent memories is still unclear. To decipher their respective involvement in memory consolidation, a pharmacological approach was chosen. Using two hippocampal-dependent behavioral paradigms (water maze and contextual fear conditioning) we now report that glutamate at CA3 synapses is necessary and sufficient for the spatial learning consolidation process, whereas glutamate and zinc released by mossy fibers are both mandatory and exert cumulative effects on contextual fear consolidation, a form of learning with a strong emotional component.
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Affiliation(s)
- Johnatan Ceccom
- Université de Toulouse, UPS, Centre de Recherches sur la Cognition Animale, F-31062 Toulouse Cedex 9, France
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70
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Kostakis E, Smith C, Jang MK, Martin SC, Richards KG, Russek SJ, Gibbs TT, Farb DH. The neuroactive steroid pregnenolone sulfate stimulates trafficking of functional N-methyl D-aspartate receptors to the cell surface via a noncanonical, G protein, and Ca2+-dependent mechanism. Mol Pharmacol 2013; 84:261-74. [PMID: 23716622 DOI: 10.1124/mol.113.085696] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
N-methyl D-aspartate (NMDA) receptors (NMDARs) mediate fast excitatory synaptic transmission and play a critical role in synaptic plasticity associated with learning and memory. NMDAR hypoactivity has been implicated in the pathophysiology of schizophrenia, and clinical studies have revealed reduced negative symptoms of schizophrenia with a dose of pregnenolone that elevates serum levels of the neuroactive steroid pregnenolone sulfate (PregS). This report describes a novel process of delayed-onset potentiation whereby PregS approximately doubles the cell's response to NMDA via a mechanism that is pharmacologically and kinetically distinct from rapid positive allosteric modulation by PregS. The number of functional cell-surface NMDARs in cortical neurons increases 60-100% within 10 minutes of exposure to PregS, as shown by surface biotinylation and affinity purification. Delayed-onset potentiation is reversible and selective for expressed receptors containing the NMDAR subunit subtype 2A (NR2A) or NR2B, but not the NR2C or NR2D, subunits. Moreover, substitution of NR2B J/K helices and M4 domain with the corresponding region of NR2D ablates rapid allosteric potentiation of the NMDA response by PregS but not delayed-onset potentiation. This demonstrates that the initial phase of rapid positive allosteric modulation is not a first step in NMDAR upregulation. Delayed-onset potentiation by PregS occurs via a noncanonical, pertussis toxin-sensitive, G protein-coupled, and Ca(2+)-dependent mechanism that is independent of NMDAR ion channel activation. Further investigation into the sequelae for PregS-stimulated trafficking of NMDARs to the neuronal cell surface may uncover a new target for the pharmacological treatment of disorders in which NMDAR hypofunction has been implicated.
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Affiliation(s)
- Emmanuel Kostakis
- Laboratory of Molecular Neurobiology, Department of Pharmacology & Experimental Therapeutics, Boston University School of Medicine, Boston, MA, USA
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71
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Paoletti P, Bellone C, Zhou Q. NMDA receptor subunit diversity: impact on receptor properties, synaptic plasticity and disease. Nat Rev Neurosci 2013; 14:383-400. [DOI: 10.1038/nrn3504] [Citation(s) in RCA: 1525] [Impact Index Per Article: 138.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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72
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Scharfman HE, MacLusky NJ. Differential regulation of BDNF, synaptic plasticity and sprouting in the hippocampal mossy fiber pathway of male and female rats. Neuropharmacology 2013; 76 Pt C:696-708. [PMID: 23660230 DOI: 10.1016/j.neuropharm.2013.04.029] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 04/10/2013] [Accepted: 04/15/2013] [Indexed: 10/26/2022]
Abstract
Many studies have described potent effects of BDNF, 17β-estradiol or androgen on hippocampal synapses and their plasticity. Far less information is available about the interactions between 17β-estradiol and BDNF in hippocampus, or interactions between androgen and BDNF in hippocampus. Here we review the regulation of BDNF in the mossy fiber pathway, a critical part of hippocampal circuitry. We discuss the emerging view that 17β-estradiol upregulates mossy fiber BDNF synthesis in the adult female rat, while testosterone exerts a tonic suppression of mossy fiber BDNF levels in the adult male rat. The consequences are interesting to consider: in females, increased excitability associated with high levels of BDNF in mossy fibers could improve normal functions of area CA3, such as the ability to perform pattern completion. However, memory retrieval may lead to anxiety if stressful events are recalled. Therefore, the actions of 17β-estradiol on the mossy fiber pathway in females may provide a potential explanation for the greater incidence of anxiety-related disorders and post-traumatic stress syndrome (PTSD) in women relative to men. In males, suppression of BDNF-dependent plasticity in the mossy fibers may be protective, but at the 'price' of reduced synaptic plasticity in CA3. This article is part of the Special Issue entitled 'BDNF Regulation of Synaptic Structure, Function, and Plasticity'.
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Affiliation(s)
- Helen E Scharfman
- Center for Dementia Research, The Nathan Kline Institute for Psychiatric Research, 140 Old Orangeburg Rd., Bldg. 35, Orangeburg, NY 10962, USA; Department of Child & Adolescent Psychiatry, New York University Langone Medical Center, New York, NY 10016, USA; Department of Physiology & Neuroscience, New York University Langone Medical Center, New York, NY 10016, USA; Department of Psychiatry, New York University Langone Medical Center, New York, NY 10016, USA.
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73
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Baker KD, Edwards TM, Rickard NS. The role of intracellular calcium stores in synaptic plasticity and memory consolidation. Neurosci Biobehav Rev 2013; 37:1211-39. [PMID: 23639769 DOI: 10.1016/j.neubiorev.2013.04.011] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 04/18/2013] [Accepted: 04/22/2013] [Indexed: 12/20/2022]
Abstract
Memory processing requires tightly controlled signalling cascades, many of which are dependent upon intracellular calcium (Ca(2+)). Despite this, most work investigating calcium signalling in memory formation has focused on plasma membrane channels and extracellular sources of Ca(2+). The intracellular Ca(2+) release channels, ryanodine receptors (RyRs) and inositol (1,4,5)-trisphosphate receptors (IP3Rs) have a significant capacity to regulate intracellular Ca(2+) signalling. Evidence at both cellular and behavioural levels implicates both RyRs and IP3Rs in synaptic plasticity and memory formation. Pharmacobehavioural experiments using young chicks trained on a single-trial discrimination avoidance task have been particularly useful by demonstrating that RyRs and IP3Rs have distinct roles in memory formation. RyR-dependent Ca(2+) release appears to aid the consolidation of labile memory into a persistent long-term memory trace. In contrast, IP3Rs are required during long-term memory. This review discusses various functions for RyRs and IP3Rs in memory processing, including neuro- and glio-transmitter release, dendritic spine remodelling, facilitating vasodilation, and the regulation of gene transcription and dendritic excitability. Altered Ca(2+) release from intracellular stores also has significant implications for neurodegenerative conditions.
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Affiliation(s)
- Kathryn D Baker
- School of Psychology and Psychiatry, Monash University, Clayton 3800, Victoria, Australia.
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74
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Testosterone depletion in adult male rats increases mossy fiber transmission, LTP, and sprouting in area CA3 of hippocampus. J Neurosci 2013; 33:2338-55. [PMID: 23392664 DOI: 10.1523/jneurosci.3857-12.2013] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Androgens have dramatic effects on neuronal structure and function in hippocampus. However, androgen depletion does not always lead to hippocampal impairment. To address this apparent paradox, we evaluated the hippocampus of adult male rats after gonadectomy (Gdx) or sham surgery. Surprisingly, Gdx rats showed increased synaptic transmission and long-term potentiation of the mossy fiber (MF) pathway. Gdx rats also exhibited increased excitability and MF sprouting. We then addressed the possible underlying mechanisms and found that Gdx induced a long-lasting upregulation of MF BDNF immunoreactivity. Antagonism of Trk receptors, which bind neurotrophins, such as BDNF, reversed the increase in MF transmission, excitability, and long-term potentiation in Gdx rats, but there were no effects of Trk antagonism in sham controls. To determine which androgens were responsible, the effects of testosterone metabolites DHT and 5α-androstane-3α,17β-diol were examined. Exposure of slices to 50 nm DHT decreased the effects of Gdx on MF transmission, but 50 nm 5α-androstane-3α,17β-diol had no effect. Remarkably, there was no effect of DHT in control males. The data suggest that a Trk- and androgen receptor-sensitive form of MF transmission and synaptic plasticity emerges after Gdx. We suggest that androgens may normally be important in area CA3 to prevent hyperexcitability and aberrant axon outgrowth but limit MF synaptic transmission and some forms of plasticity. The results also suggest a potential explanation for the maintenance of hippocampal-dependent cognitive function after androgen depletion: a reduction in androgens may lead to compensatory upregulation of MF transmission and plasticity.
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75
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Ramos-Languren LE, Escobar ML. Plasticity and metaplasticity of adult rat hippocampal mossy fibers induced by neurotrophin-3. Eur J Neurosci 2013; 37:1248-59. [DOI: 10.1111/ejn.12141] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Revised: 12/18/2012] [Accepted: 12/23/2012] [Indexed: 12/29/2022]
Affiliation(s)
- L. E. Ramos-Languren
- División de Investigación y Estudios de Posgrado; Facultad de Psicología; Universidad Nacional Autónoma de México; 04510; México City; D.F.; México
| | - M. L. Escobar
- División de Investigación y Estudios de Posgrado; Facultad de Psicología; Universidad Nacional Autónoma de México; 04510; México City; D.F.; México
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76
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Lateral thinking: CaMKII uncouples kainate receptors from mossy fibre synapses. EMBO J 2013; 32:487-9. [PMID: 23361317 DOI: 10.1038/emboj.2013.12] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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77
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Carta M, Opazo P, Veran J, Athané A, Choquet D, Coussen F, Mulle C. CaMKII-dependent phosphorylation of GluK5 mediates plasticity of kainate receptors. EMBO J 2013; 32:496-510. [PMID: 23288040 DOI: 10.1038/emboj.2012.334] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2012] [Accepted: 11/16/2012] [Indexed: 01/15/2023] Open
Abstract
Calmodulin-dependent kinase II (CaMKII) is key for long-term potentiation of synaptic AMPA receptors. Whether CaMKII is involved in activity-dependent plasticity of other ionotropic glutamate receptors is unknown. We show that repeated pairing of pre- and postsynaptic stimulation at hippocampal mossy fibre synapses induces long-term depression of kainate receptor (KAR)-mediated responses, which depends on Ca(2+) influx, activation of CaMKII, and on the GluK5 subunit of KARs. CaMKII phosphorylation of three residues in the C-terminal domain of GluK5 subunit markedly increases lateral mobility of KARs, possibly by decreasing the binding of GluK5 to PSD-95. CaMKII activation also promotes surface expression of KARs at extrasynaptic sites, but concomitantly decreases its synaptic content. Using a molecular replacement strategy, we demonstrate that the direct phosphorylation of GluK5 by CaMKII is necessary for KAR-LTD. We propose that CaMKII-dependent phosphorylation of GluK5 is responsible for synaptic depression by untrapping of KARs from the PSD and increased diffusion away from synaptic sites.
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Affiliation(s)
- Mario Carta
- Université Bordeaux, Institut Interdisciplinaire de Neurosciences, UMR 5297, Bordeaux, France
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78
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Pre- and postsynaptic localization of NMDA receptor subunits at hippocampal mossy fibre synapses. Neuroscience 2013; 230:139-50. [DOI: 10.1016/j.neuroscience.2012.10.061] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2012] [Revised: 10/25/2012] [Accepted: 10/26/2012] [Indexed: 11/20/2022]
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79
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Zhao S, Studer D, Chai X, Graber W, Brose N, Nestel S, Young C, Rodriguez EP, Saetzler K, Frotscher M. Structural plasticity of hippocampal mossy fiber synapses as revealed by high-pressure freezing. J Comp Neurol 2012; 520:2340-51. [PMID: 22237743 DOI: 10.1002/cne.23040] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Despite recent progress in fluorescence microscopy techniques, electron microscopy (EM) is still superior in the simultaneous analysis of all tissue components at high resolution. However, it is unclear to what extent conventional fixation for EM using aldehydes results in tissue alteration. Here we made an attempt to minimize tissue alteration by using rapid high-pressure freezing (HPF) of hippocampal slice cultures. We used this approach to monitor fine-structural changes at hippocampal mossy fiber synapses associated with chemically induced long-term potentiation (LTP). Synaptic plasticity in LTP has been known to involve structural changes at synapses including reorganization of the actin cytoskeleton and de novo formation of spines. While LTP-induced formation and growth of postsynaptic spines have been reported, little is known about associated structural changes in presynaptic boutons. Mossy fiber synapses are assumed to exhibit presynaptic LTP expression and are easily identified by EM. In slice cultures from wildtype mice, we found that chemical LTP increased the length of the presynaptic membrane of mossy fiber boutons, associated with a de novo formation of small spines and an increase in the number of active zones. Of note, these changes were not observed in slice cultures from Munc13-1 knockout mutants exhibiting defective vesicle priming. These findings show that activation of hippocampal mossy fibers induces pre- and postsynaptic structural changes at mossy fiber synapses that can be monitored by EM.
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Affiliation(s)
- Shanting Zhao
- Department for Structural Neurobiology, Center for Molecular Neurobiology Hamburg-ZMNH, University of Hamburg, D-20246 Hamburg, Germany
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80
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Hovelsø N, Sotty F, Montezinho LP, Pinheiro PS, Herrik KF, Mørk A. Therapeutic potential of metabotropic glutamate receptor modulators. Curr Neuropharmacol 2012; 10:12-48. [PMID: 22942876 PMCID: PMC3286844 DOI: 10.2174/157015912799362805] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2010] [Revised: 01/10/2011] [Accepted: 03/04/2011] [Indexed: 12/21/2022] Open
Abstract
Glutamate is the main excitatory neurotransmitter in the central nervous system (CNS) and is a major player in complex brain functions. Glutamatergic transmission is primarily mediated by ionotropic glutamate receptors, which include NMDA, AMPA and kainate receptors. However, glutamate exerts modulatory actions through a family of metabotropic G-protein-coupled glutamate receptors (mGluRs). Dysfunctions of glutamatergic neurotransmission have been implicated in the etiology of several diseases. Therefore, pharmacological modulation of ionotropic glutamate receptors has been widely investigated as a potential therapeutic strategy for the treatment of several disorders associated with glutamatergic dysfunction. However, blockade of ionotropic glutamate receptors might be accompanied by severe side effects due to their vital role in many important physiological functions. A different strategy aimed at pharmacologically interfering with mGluR function has recently gained interest. Many subtype selective agonists and antagonists have been identified and widely used in preclinical studies as an attempt to elucidate the role of specific mGluRs subtypes in glutamatergic transmission. These studies have allowed linkage between specific subtypes and various physiological functions and more importantly to pathological states. This article reviews the currently available knowledge regarding the therapeutic potential of targeting mGluRs in the treatment of several CNS disorders, including schizophrenia, addiction, major depressive disorder and anxiety, Fragile X Syndrome, Parkinson’s disease, Alzheimer’s disease and pain.
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Affiliation(s)
- N Hovelsø
- Department of Neurophysiology, H. Lundbeck A/S, Ottiliavej 9, 2500 Copenhagen-Valby, Denmark
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81
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Deak F, Sonntag WE. Aging, synaptic dysfunction, and insulin-like growth factor (IGF)-1. J Gerontol A Biol Sci Med Sci 2012; 67:611-25. [PMID: 22503992 PMCID: PMC3348499 DOI: 10.1093/gerona/gls118] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 03/16/2012] [Indexed: 01/05/2023] Open
Abstract
Insulin-like growth factor (IGF)-1 is an important neurotrophic hormone. Deficiency of this hormone has been reported to influence the genesis of cognitive impairment and dementia in the elderly patients. Nevertheless, there are studies indicating that cognitive function can be maintained into old age even in the absence of circulating IGF-1 and studies that link IGF-1 to an acceleration of neurological diseases. Although IGF-1 has a complex role in brain function, synaptic effects appear to be central to the IGF-1-induced improvement in learning and memory. In this review, synaptic mechanisms of learning and memory and the effects of IGF-1 on synaptic communication are discussed. The emerging data indicate that synaptic function decreases with age and that IGF-1 contributes to information processing in the brain. Further studies that detail the specific actions of this important neurotrophic hormone will likely lead to therapies that result in improved cognitive function for the elderly patients.
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Affiliation(s)
- Ferenc Deak
- Department of Neuroscience, Mayo Clinic, Jacksonville, Florida
| | - William E. Sonntag
- Reynolds Oklahoma Center on Aging, Donald W. Reynolds Department of Geriatric Medicine, Oklahoma City, Oklahoma
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82
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Harney SC, Anwyl R. Plasticity of NMDA receptor-mediated excitatory postsynaptic currents at perforant path inputs to dendrite-targeting interneurons. J Physiol 2012; 590:3771-86. [PMID: 22615437 DOI: 10.1113/jphysiol.2012.234740] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Synaptic plasticity of NMDA receptors (NMDARs) has been recently described in a number of brain regions and we have previously characterised LTP and LTD of glutamatergic NMDA receptor-mediated EPSCs (NMDAR-EPSCs) in granule cells of dentate gyrus. The functional significance of NMDAR plasticity at perforant path synapses on hippocampal network activity depends on whether this is a common feature of perforant path synapses on all postsynaptic target cells or if this plasticity occurs only at synapses on principal cells. We recorded NMDAR-EPSCs at medial perforant path synapses on interneurons in dentate gyrus which had significantly slower decay kinetics compared to those recorded in granule cells. NMDAR pharmacology in interneurons was consistent with expression of both GluN2B- and GluN2D-containing receptors. In contrast to previously described high frequency stimulation-induced bidirectional plasticity of NMDAR-EPSCs in granule cells, only LTD of NMDAR-EPSCs was induced in interneurons in our standard experimental conditions. In interneurons, LTD of NMDAR-EPSCs was associated with a loss of sensitivity to a GluN2D-selective antagonist and was inhibited by the actin stabilising agent, jasplakinolide. While LTP of NMDAR-EPSCs can be readily induced in granule cells, this form of plasticity was only observed in interneurons when extracellular calcium was increased above physiological concentrations during HFS or when PKC was directly activated by phorbol ester, suggesting that opposing forms of plasticity at inputs to interneurons and principal cells may act to regulate granule cell dendritic integration and processing.
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Affiliation(s)
- Sarah C Harney
- Department of Physiology, Trinity College Dublin, Dublin 2, Ireland.
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83
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Flores CE, Nannapaneni S, Davidson KGV, Yasumura T, Bennett MVL, Rash JE, Pereda AE. Trafficking of gap junction channels at a vertebrate electrical synapse in vivo. Proc Natl Acad Sci U S A 2012; 109:E573-82. [PMID: 22323580 PMCID: PMC3295297 DOI: 10.1073/pnas.1121557109] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Trafficking and turnover of transmitter receptors required to maintain and modify the strength of chemical synapses have been characterized extensively. In contrast, little is known regarding trafficking of gap junction components at electrical synapses. By combining ultrastructural and in vivo physiological analysis at identified mixed (electrical and chemical) synapses on the goldfish Mauthner cell, we show here that gap junction hemichannels are added at the edges of GJ plaques where they dock with hemichannels in the apposed membrane to form cell-cell channels and, simultaneously, that intact junctional regions are removed from centers of these plaques into either presynaptic axon or postsynaptic dendrite. Moreover, electrical coupling is readily modified by intradendritic application of peptides that interfere with endocytosis or exocytosis, suggesting that the strength of electrical synapses at these terminals is sustained, at least in part, by fast (in minutes) turnover of gap junction channels. A peptide corresponding to a region of the carboxy terminus that is conserved in Cx36 and its two teleost homologs appears to interfere with formation of new gap junction channels, presumably by reducing insertion of hemichannels on the dendritic side. Thus, our data indicate that electrical synapses are dynamic structures and that their channels are turned over actively, suggesting that regulated trafficking of connexons may contribute to the modification of gap junctional conductance.
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Affiliation(s)
- Carmen E. Flores
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Srikant Nannapaneni
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461
| | | | - Thomas Yasumura
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523; and
| | - Michael V. L. Bennett
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461
| | - John E. Rash
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523; and
- Program in Cell and Molecular Biology, Colorado State University, Fort Collins, CO 80523
| | - Alberto E. Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461
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84
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Hunt DL, Castillo PE. Synaptic plasticity of NMDA receptors: mechanisms and functional implications. Curr Opin Neurobiol 2012; 22:496-508. [PMID: 22325859 DOI: 10.1016/j.conb.2012.01.007] [Citation(s) in RCA: 232] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Revised: 12/09/2011] [Accepted: 01/19/2012] [Indexed: 12/11/2022]
Abstract
Beyond their well-established role as triggers for LTP and LTD of fast synaptic transmission mediated by AMPA receptors, an expanding body of evidence indicates that NMDA receptors (NMDARs) themselves are also dynamically regulated and subject to activity-dependent long-term plasticity. NMDARs can significantly contribute to information transfer at synapses particularly during periods of repetitive activity. It is also increasingly recognized that NMDARs participate in dendritic synaptic integration and are critical for generating persistent activity of neural assemblies. Here we review recent advances on the mechanisms and functional consequences of NMDAR plasticity. Given the unique biophysical properties of NMDARs, synaptic plasticity of NMDAR-mediated transmission emerges as a particularly powerful mechanism for the fine tuning of information encoding and storage throughout the brain.
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Affiliation(s)
- David L Hunt
- Dominick P. Purpura, Department of Neuroscience, Albert Einstein College of Medicine, Kennedy Center, Room 703, Bronx, NY 10461, United States
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85
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A novel form of low-frequency hippocampal mossy fiber plasticity induced by bimodal mGlu1 receptor signaling. J Neurosci 2012; 31:16897-906. [PMID: 22114260 DOI: 10.1523/jneurosci.1264-11.2011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Mossy fiber synapses act as the critical mediators of highly dynamic communication between hippocampal granule cells in the dentate gyrus and CA3 pyramidal neurons. Excitatory synaptic strength at mossy fiber to CA3 pyramidal cell synapses is potentiated rapidly and reversibly by brief trains of low-frequency stimulation of mossy fiber axons. We show that slight modifications to the pattern of stimulation convert this short-term potentiation into prolonged synaptic strengthening lasting tens of minutes in rodent hippocampal slices. This low-frequency potentiation of mossy fiber EPSCs requires postsynaptic mGlu1 receptors for induction but is expressed presynaptically as an increased release probability and therefore impacts both AMPA and NMDA components of the mossy fiber EPSC. A nonconventional signaling pathway initiated by mGlu1 receptors contributes to induction of plasticity, because EPSC potentiation was prevented by a tyrosine kinase inhibitor and only partially reduced by guanosine 5'-O-(2-thiodiphosphate). A slowly reversible state of enhanced synaptic efficacy could serve as a mechanism for altering the integrative properties of this synapse within a relatively broad temporal window.
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86
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Vivar C, Traub RD, Gutiérrez R. Mixed electrical-chemical transmission between hippocampal mossy fibers and pyramidal cells. Eur J Neurosci 2011; 35:76-82. [PMID: 22151275 DOI: 10.1111/j.1460-9568.2011.07930.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Morphological and electrophysiological studies have shown that granule cell axons, the mossy fibers (MFs), establish gap junctions and therefore electrical communication among them. That granule cells express gap junctional proteins in their axons suggests the possibility that their terminals also express them. If this were to be the case, mixed electrical-chemical communication could be supported, as MF terminals normally use glutamate for fast communication with their target cells. Here we present electrophysiological studies in the rat and modeling studies consistent with this hypothesis. We show that MF activation produced fast spikelets followed by excitatory postsynaptic potentials in pyramidal cells (PCs), which, unlike the spikelets, underwent frequency potentiation and were strongly depressed by activation of metabotropic glutamate receptors, as expected from transmission of MF origin. The spikelets, which persisted during blockade of chemical transmission, were potentiated by dopamine and suppressed by the gap junction blocker carbenoxolone. The various waveforms evoked by MF stimulation were replicated in a multi-compartment model of a PC by brief current-pulse injections into the proximal apical dendritic compartment, where MFs are known to contact PCs. Mixed electrical and glutamatergic communication between granule cells and some PCs in CA3 may ensure the activation of sets of PCs, bypassing the strong action of concurrent feed-forward inhibition that granule cells activate. Importantly, MF-to-PC electrical coupling may allow bidirectional, possibly graded, communication that can be faster than chemical synapses and subject to different forms of modulation.
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Affiliation(s)
- Carmen Vivar
- Department of Physiology, Biophysics and Neurosciences, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional, México, D.F., México
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87
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Zhang P, Lisman JE. Activity-dependent regulation of synaptic strength by PSD-95 in CA1 neurons. J Neurophysiol 2011; 107:1058-66. [PMID: 22114157 DOI: 10.1152/jn.00526.2011] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
CaMKII and PSD-95 are the two most abundant postsynaptic proteins in the postsynaptic density (PSD). Overexpression of either can dramatically increase synaptic strength and saturate long-term potentiation (LTP). To do so, CaMKII must be activated, but the same is not true for PSD-95; expressing wild-type PSD-95 is sufficient. This raises the question of whether PSD-95's effects are simply an equilibrium process [increasing the number of AMPA receptor (AMPAR) slots] or whether activity is somehow involved. To examine this question, we blocked activity in cultured hippocampal slices with TTX and found that the effects of PSD-95 overexpression were greatly reduced. We next studied the type of receptors involved. The effects of PSD-95 were prevented by antagonists of group I metabotropic glutamate receptors (mGluRs) but not by antagonists of ionotropic glutamate receptors. The inhibition of PSD-95-induced strengthening was not simply a result of inhibition of PSD-95 synthesis. To understand the mechanisms involved, we tested the role of CaMKII. Overexpression of a CaMKII inhibitor, CN19, greatly reduced the effect of PSD-95. We conclude that PSD-95 cannot itself increase synaptic strength simply by increasing the number of AMPAR slots; rather, PSD-95's effects on synaptic strength require an activity-dependent process involving mGluR and CaMKII.
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Affiliation(s)
- Peng Zhang
- Biology Department and Volen Center for Complex Systems, Brandeis University, Waltham, Massachusetts 02454, USA
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88
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Sindreu C, Storm DR. Modulation of neuronal signal transduction and memory formation by synaptic zinc. Front Behav Neurosci 2011; 5:68. [PMID: 22084630 PMCID: PMC3211062 DOI: 10.3389/fnbeh.2011.00068] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Accepted: 10/03/2011] [Indexed: 12/31/2022] Open
Abstract
The physiological role of synaptic zinc has remained largely enigmatic since its initial detection in hippocampal mossy fibers over 50 years ago. The past few years have witnessed a number of studies highlighting the ability of zinc ions to regulate ion channels and intracellular signaling pathways implicated in neuroplasticity, and others that shed some light on the elusive role of synaptic zinc in learning and memory. Recent behavioral studies using knock-out mice for the synapse-specific zinc transporter ZnT-3 indicate that vesicular zinc is required for the formation of memories dependent on the hippocampus and the amygdala, two brain centers that are prominently innervated by zinc-rich fibers. A common theme emerging from this research is the activity-dependent regulation of the Erk1/2 mitogen-activated-protein kinase pathway by synaptic zinc through diverse mechanisms in neurons. Here we discuss current knowledge on how synaptic zinc may play a role in cognition through its impact on neuronal signaling.
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Affiliation(s)
- Carlos Sindreu
- Department of Pharmacology, University of Washington Seattle, WA, USA
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89
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Oxygen/glucose deprivation induces a reduction in synaptic AMPA receptors on hippocampal CA3 neurons mediated by mGluR1 and adenosine A3 receptors. J Neurosci 2011; 31:11941-52. [PMID: 21849555 DOI: 10.1523/jneurosci.1183-11.2011] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Hippocampal CA1 pyramidal neurons are highly sensitive to ischemic damage, whereas neighboring CA3 pyramidal neurons are less susceptible. It is proposed that switching of AMPA receptor (AMPAR) subunits on CA1 neurons during an in vitro model of ischemia, oxygen/glucose deprivation (OGD), leads to an enhanced permeability of AMPARs to Ca(2+), resulting in delayed cell death. However, it is unclear whether the same mechanisms exist in CA3 neurons and whether this underlies the differential sensitivity to ischemia. Here, we investigated the consequences of OGD for AMPAR function in CA3 neurons using electrophysiological recordings in rat hippocampal slices. Following a 15 min OGD protocol, a substantial depression of AMPAR-mediated synaptic transmission was observed at CA3 associational/commissural and mossy fiber synapses but not CA1 Schaffer collateral synapses. The depression of synaptic transmission following OGD was prevented by metabotropic glutamate receptor 1 (mGluR1) or A(3) receptor antagonists, indicating a role for both glutamate and adenosine release. Inhibition of PLC, PKC, or chelation of intracellular Ca(2+) also prevented the depression of synaptic transmission. Inclusion of peptides to interrupt the interaction between GluA2 and PICK1 or dynamin and amphiphysin prevented the depression of transmission, suggesting a dynamin and PICK1-dependent internalization of AMPARs after OGD. We also show that a reduction in surface and total AMPAR protein levels after OGD was prevented by mGluR1 or A(3) receptor antagonists, indicating that AMPARs are degraded following internalization. Thus, we describe a novel mechanism for the removal of AMPARs in CA3 pyramidal neurons following OGD that has the potential to reduce excitotoxicity and promote neuroprotection.
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90
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Nisticò R, Dargan SL, Amici M, Collingridge GL, Bortolotto ZA. Synergistic interactions between kainate and mGlu receptors regulate bouton Ca signalling and mossy fibre LTP. Sci Rep 2011; 1:103. [PMID: 22355621 PMCID: PMC3216588 DOI: 10.1038/srep00103] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Accepted: 09/07/2011] [Indexed: 12/04/2022] Open
Abstract
It is currently unknown why glutamatergic presynaptic terminals express multiple types of glutamate receptors. We have addressed this question by studying both acute and long-term regulation of mossy fibre function in the hippocampus. We find that inhibition of both mGlu1 and mGlu5 receptors together can block the induction of mossy fibre LTP. Furthermore, mossy fibre LTP can be induced by the pharmacological activation of either mGlu1 or mGlu5 receptors, provided that kainate receptors are also stimulated. Like conventional mossy fibre LTP, chemically-induced mossy fibre LTP (chem-LTPm) depends on Ca2+ release from intracellular stores and the activation of PKA. Similar synergistic interactions between mGlu receptors and kainate receptors were observed at the level of Ca2+ signalling in individual giant mossy fibre boutons. Thus three distinct glutamate receptors interact, in both an AND and OR gate fashion, to regulate both immediate and long-term presynaptic function in the brain.
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Affiliation(s)
- Robert Nisticò
- MRC Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol, BS8 1TD, United Kingdom
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91
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Pan E, Zhang XA, Huang Z, Krezel A, Zhao M, Tinberg CE, Lippard SJ, McNamara JO. Vesicular zinc promotes presynaptic and inhibits postsynaptic long-term potentiation of mossy fiber-CA3 synapse. Neuron 2011; 71:1116-26. [PMID: 21943607 DOI: 10.1016/j.neuron.2011.07.019] [Citation(s) in RCA: 153] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/15/2011] [Indexed: 01/05/2023]
Abstract
The presence of zinc in glutamatergic synaptic vesicles of excitatory neurons of mammalian cerebral cortex suggests that zinc might regulate plasticity of synapses formed by these neurons. Long-term potentiation (LTP) is a form of synaptic plasticity that may underlie learning and memory. We tested the hypothesis that zinc within vesicles of mossy fibers (mf) contributes to mf-LTP, a classical form of presynaptic LTP. We synthesized an extracellular zinc chelator with selectivity and kinetic properties suitable for study of the large transient of zinc in the synaptic cleft induced by mf stimulation. We found that vesicular zinc is required for presynaptic mf-LTP. Unexpectedly, vesicular zinc also inhibits a form of postsynaptic mf-LTP. Because the mf-CA3 synapse provides a major source of excitatory input to the hippocampus, regulating its efficacy by these dual actions, vesicular zinc is critical to proper function of hippocampal circuitry in health and disease.
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Affiliation(s)
- Enhui Pan
- Department of Medicine (Neurology), Duke University Medical Center, Durham, NC 27710, USA
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92
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Abstract
Ionotropic glutamate receptors of AMPA, NMDA, and kainate receptor (KAR) subtypes mediate fast excitatory synaptic transmission in the vertebrate CNS. Auxiliary proteins have been identified for AMPA and NMDA receptor complexes, but little is known about KAR complex proteins. We previously identified the CUB (complement C1r/C1s, Uegf, Bmpl) domain protein, Neto1, as an NMDA receptor-associated polypeptide. Here, we show that Neto1 is also an auxiliary subunit for endogenous synaptic KARs. We found that Neto1 and KARs coimmunoprecipitated from brain lysates, from postsynaptic densities (PSDs) and, in a manner dependent on Neto1 CUB domains, when coexpressed in heterologous cells. In Neto1-null mice, there was an ∼50% reduction in the abundance of GluK2-KARs in hippocampal PSDs. Neto1 strongly localized to CA3 stratum lucidum, and loss of Neto1 resulted in a selective deficit in KAR-mediated neurotransmission at mossy fiber-CA3 pyramidal cell (MF-CA3) synapses: KAR-mediated EPSCs in Neto1-null mice were reduced in amplitude and decayed more rapidly than did those in wild-type mice. In contrast, the loss of Neto2, which also localizes to stratum lucidum and interacts with KARs, had no effect on KAR synaptic abundance or MF-CA3 transmission. Indeed, MF-CA3 KAR deficits in Neto1/Neto2-double-null mutant mice were indistinguishable from Neto1 single-null mice. Thus, our findings establish Neto1 as an auxiliary protein required for synaptic function of KARs. The ability of Neto1 to regulate both NMDARs and KARs reveals a unique dual role in controlling synaptic transmission by serving as an auxiliary protein for these two classes of ionotropic glutamate receptors in a synapse-specific fashion.
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93
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Li S, Cao J, Yang X, Suo ZW, Shi L, Liu YN, Yang HB, Hu XD. NR2B phosphorylation at tyrosine 1472 in spinal dorsal horn contributed to N-methyl-D-aspartate-induced pain hypersensitivity in mice. J Neurosci Res 2011; 89:1869-76. [DOI: 10.1002/jnr.22719] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2010] [Revised: 05/10/2011] [Accepted: 05/19/2011] [Indexed: 12/30/2022]
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94
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NMDA receptor–dependent metaplasticity at hippocampal mossy fiber synapses. Nat Neurosci 2011; 14:691-3. [DOI: 10.1038/nn.2809] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Accepted: 03/17/2011] [Indexed: 11/09/2022]
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95
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Matta JA, Ashby MC, Sanz-Clemente A, Roche KW, Isaac JTR. mGluR5 and NMDA receptors drive the experience- and activity-dependent NMDA receptor NR2B to NR2A subunit switch. Neuron 2011; 70:339-51. [PMID: 21521618 PMCID: PMC3087383 DOI: 10.1016/j.neuron.2011.02.045] [Citation(s) in RCA: 144] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/15/2011] [Indexed: 11/30/2022]
Abstract
In cerebral cortex there is a developmental switch from NR2B- to NR2A-containing NMDA receptors (NMDARs) driven by activity and sensory experience. This subunit switch alters NMDAR function, influences synaptic plasticity, and its dysregulation is associated with neurological disorders. However, the mechanisms driving the subunit switch are not known. Here, we show in hippocampal CA1 pyramidal neurons that the NR2B to NR2A switch driven acutely by activity requires activation of NMDARs and mGluR5, involves PLC, Ca(2+) release from IP(3)R-dependent stores, and PKC activity. In mGluR5 knockout mice the developmental NR2B-NR2A switch in CA1 is deficient. Moreover, in visual cortex of mGluR5 knockout mice, the NR2B-NR2A switch evoked in vivo by visual experience is absent. Thus, we establish that mGluR5 and NMDARs are required for the activity-dependent NR2B-NR2A switch and play a critical role in experience-dependent regulation of NMDAR subunit composition in vivo.
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Affiliation(s)
- Jose A. Matta
- Developmental Synaptic Plasticity Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD20892, USA
| | - Michael C. Ashby
- Developmental Synaptic Plasticity Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD20892, USA
| | - Antonio Sanz-Clemente
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD20892, USA
| | - Katherine W. Roche
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD20892, USA
| | - John T. R. Isaac
- Developmental Synaptic Plasticity Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD20892, USA
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96
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Ng AN, Krogh M, Toresson H. Dendritic EGFP-STIM1 activation after type I metabotropic glutamate and muscarinic acetylcholine receptor stimulation in hippocampal neuron. J Neurosci Res 2011; 89:1235-44. [PMID: 21538465 DOI: 10.1002/jnr.22648] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2010] [Revised: 02/01/2011] [Accepted: 02/21/2011] [Indexed: 11/08/2022]
Abstract
Several signaling pathways in neurons engage the endoplasmic reticulum (ER) calcium store by triggering calcium release. After release, ER calcium levels must be restored. In many non-neuronal cell types, this is mediated by store-operated calcium entry (SOCE), a cellular homeostatic mechanism that activates specialized store-operated calcium channels (SOC). Although much evidence supports the existence of SOCE in neurons, its importance has been difficult to determine because of the abundance of calcium channels expressed and the lack of SOC-specific pharmacological agents. We have explored the function of the SOCE-inducing protein STIM1 in neurons. In EGFP-STIM1-expressing hippocampal neurons, the sarco- and endoplasmic reticulum calcium ATPase (SERCA) inhibitor thapsigargin caused rapid aggregation (i.e., activation) of STIM1 in soma and dendrites. Upon STIM1 activation by thapsigargin, a dramatic reduction in STIM1 mobility was detected by fluorescence recovery after photobleaching (FRAP). By triggering release of ER calcium with 3,5-dihydroxyphenylglycine (DHPG) or carbachol (Cch), agonists of type I metabotropic glutamate receptors (mGluR) and muscarinic acetylcholine receptors (mAChR), respectively, STIM1 was activated, and calcium entry (likely to represent SOCE) occurred in dendrites. It is therefore possible that neuronal SOCE is activated by physiological stimuli, some of which may alter the postsynaptic calcium signaling properties.
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Affiliation(s)
- Ai Na Ng
- Laboratory for Experimental Brain Research, Wallenberg Neuroscience Centre, Department of Clinical Sciences Lund, Lund University, Lund, Sweden.
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97
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Barak B, Williams A, Bielopolski N, Gottfried I, Okun E, Brown MA, Matti U, Rettig J, Stuenkel EL, Ashery U. Tomosyn expression pattern in the mouse hippocampus suggests both presynaptic and postsynaptic functions. Front Neuroanat 2010; 4:149. [PMID: 21191478 PMCID: PMC3010824 DOI: 10.3389/fnana.2010.00149] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Accepted: 11/30/2010] [Indexed: 11/30/2022] Open
Abstract
The protein tomosyn decreases synaptic transmission and release probability of vesicles, and is essential for modulating synaptic transmission in neurons. In this study, we provide a detailed description of the expression and localization patterns of tomosyn1 and tomosyn2 in the subareas of the mouse hippocampus. Using confocal and two-photon high-resolution microscopy we demonstrate that tomosyn colocalizes with several pre- and postsynaptic markers and is found mainly in glutamatergic synapses. Specifically, we show that tomosyn1 is differentially distributed in the mouse hippocampus and concentrated mainly in the hilus and mossy fibers. Surprisingly, we found that tomosyn2 is expressed in the subiculum, CA1 and CA2 pyramidal cell bodies, dendrites and spines, and colocalizes with PSD95, suggesting a postsynaptic role. These results suggest that in addition to the well-characterized presynaptic function of tomosyn in neurotransmitter release, tomosyn2 might have a postsynaptic function, and place tomosyn as a more general regulator of synaptic transmission and plasticity.
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Affiliation(s)
- Boaz Barak
- Department of Neurobiology, The George S. Wise Faculty of Life Sciences, Tel-Aviv University Tel Aviv, Israel
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98
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Galván EJ, Cosgrove KE, Barrionuevo G. Multiple forms of long-term synaptic plasticity at hippocampal mossy fiber synapses on interneurons. Neuropharmacology 2010; 60:740-7. [PMID: 21093459 DOI: 10.1016/j.neuropharm.2010.11.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2010] [Revised: 10/29/2010] [Accepted: 11/10/2010] [Indexed: 11/24/2022]
Abstract
The hippocampal mossy fiber (MF) pathway originates from the dentate gyrus granule cells and provides a powerful excitatory synaptic drive to neurons in the dentate gyrus hilus and area CA3. Much of the early work on the MF pathway focused on its electrophysiological properties, and ability to drive CA3 pyramidal cell activity. Over the last ten years, however, a new focus on the synaptic interaction between granule cells and inhibitory interneurons has emerged. These data have revealed an immense heterogeneity of long-term plasticity at MF synapses on various interneuron targets. Interestingly, these studies also indicate that the mechanisms of MF long-term plasticity in some interneuron subtypes may be more similar to pyramidal cells than previously appreciated. In this review, we first define the synapse types at each of the interneuron targets based on the receptors present. We then describe the different forms of long-term plasticity observed, and the mechanisms underlying each form as they are currently understood. Finally we highlight various open questions surrounding MF long-term plasticity in interneurons, focusing specifically on the induction and maintenance of LTP, and what the functional impact of persistent changes in efficacy at MF-interneuron synapses might be on the emergent properties of the inhibitory network dynamics in area CA3. This article is part of a Special Issue entitled 'Synaptic Plasticity & Interneurons'.
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Affiliation(s)
- Emilio J Galván
- Dept. of Pharmacobiology, CINVESTAV-Sur, Mexico City, Mexico.
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99
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Uchida T, Fukuda S, Kamiya H. Heterosynaptic enhancement of the excitability of hippocampal mossy fibers by long-range spill-over of glutamate. Hippocampus 2010; 22:222-9. [DOI: 10.1002/hipo.20885] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/15/2010] [Indexed: 11/06/2022]
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100
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Witton J, Brown JT, Jones MW, Randall AD. Altered synaptic plasticity in the mossy fibre pathway of transgenic mice expressing mutant amyloid precursor protein. Mol Brain 2010; 3:32. [PMID: 21040543 PMCID: PMC2988062 DOI: 10.1186/1756-6606-3-32] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Accepted: 11/01/2010] [Indexed: 01/05/2023] Open
Abstract
Aβ peptides derived from the cleavage of amyloid precursor protein are widely believed to play an important role in the pathophysiology of Alzheimer's disease. A common way to study the impact of these molecules on CNS function is to compare the physiology of transgenic mice that overproduce Aβ with non-transgenic animals. In the hippocampus, this approach has been frequently applied to the investigation of synaptic transmission and plasticity in the perforant and Schaffer collateral commissural pathways, the first and third components of the classical hippocampal trisynaptic circuit, respectively. Similar studies however have not been carried out on the remaining component of the trisynaptic circuit, the mossy fibre pathway. Using transverse hippocampal slices prepared from ~2 year old animals we have compared mossy fibre synaptic function in wild-type mice and their Tg2576 littermates which age-dependently overproduce Aβ. Input-output curves were not altered in slices from Tg2576 mice, but these animals exhibited a significant loss of the prominent frequency-facilitation expressed by the mossy fibre pathway. In addition to this change in short term synaptic plasticity, high frequency stimulation-induced, NMDA-receptor-independent LTP was absent in slices from the transgenic mice. These data represent the first description of functional deficits in the mossy fibre pathway of Aβ-overproducing transgenic mice.
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Affiliation(s)
- Jonathan Witton
- School of Physiology and Pharmacology, University of Bristol, University Walk, Bristol, BS8 1TD, UK
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