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Zhang XL, Li YX, Berglund N, Burgdorf JS, Donello JE, Moskal JR, Stanton PK. Zelquistinel acts at an extracellular binding domain to modulate intracellular calcium inactivation of N-methyl-d-aspartate receptors. Neuropharmacology 2024; 259:110100. [PMID: 39117105 DOI: 10.1016/j.neuropharm.2024.110100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2024] [Revised: 07/31/2024] [Accepted: 08/01/2024] [Indexed: 08/10/2024]
Abstract
Stinels are a novel class of N-methyl-d-aspartate glutamate receptor (NMDAR) positive allosteric modulators. We explored mechanism of action and NR2 subtype specificity of the stinel zelquistinel (ZEL) in HEK 293 cells expressing recombinant NMDARs. ZEL potently enhanced NMDAR current at NR2A (EC50 = 9.9 ± 0.5 nM) and NR2C-containing (EC50 = 9.7 ± 0.6 nM) NMDARs, with a larger ceiling enhancement at NR2B-NMDAR (EC50 = 35.0 ± 0.7 nM), while not affecting NR2D-containing NMDARs. In cells expressing NR2A and NR2C-containing NMDARs, ZEL exhibited an inverted-U dose-response relation, with a low concentration enhancement and high concentration suppression of NMDAR currents. Extracellular application of ZEL potentiated NMDAR receptor activity via prolongation of NMDAR currents. Replacing the slow Ca2+ intracellular chelator EGTA with the fast chelator BAPTA blocked ZEL potentiation of NMDARs, suggesting an action on intracellular Ca2+-calmodulin-dependent inactivation (CDI). Consistent with this mechanism of action, removal of the NR1 intracellular C-terminus, or intracellular infusion of a calmodulin blocking peptide, blocked ZEL potentiation of NMDAR current. In contrast, BAPTA did not prevent high-dose suppression of current, indicating this effect has a different mechanism of action. These data indicate ZEL is a novel positive allosteric modulator that binds extracellularly and acts through a unique long-distance mechanism to reduce NMDAR CDI, eliciting enhancement of NMDAR current. The critical role that NMDARs play in long-term, activity-dependent synaptic plasticity, learning, memory and cognition, suggests dysregulation of CDI may contribute to psychiatric disorders such as depression, schizophrenia and others, and that the stinel class of drugs can restore NMDAR-dependent synaptic plasticity by reducing activity-dependent CDI.
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Affiliation(s)
- Xiao-Lei Zhang
- Department of Cell Biology & Anatomy, New York Medical College, Valhalla, NY, 10595, USA
| | - Yong-Xin Li
- AbbVie Inc, 2525 Dupont Drive, Irvine, CA, 92612, USA
| | - Nils Berglund
- Department of Chemistry, Aarhus University, Aarhus, Denmark; Eve BioTek, Warrington, UK
| | | | - John E Donello
- Gate Neurosciences, 1210 Waterway Blvd, Indianapolis, IN, 46202, USA
| | - Joseph R Moskal
- Department of Biomedical Engineering, McCormick School of Engineering and Applied Sciences, Northwestern University, Evanston, IL, 60208, USA
| | - Patric K Stanton
- Department of Cell Biology & Anatomy, New York Medical College, Valhalla, NY, 10595, USA; Department of Neurology, New York Medical College, Valhalla, NY, 10595, USA.
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Yang JS, Jang HJ, Sung KW, Rhie DJ, Yoon SH. Roles of metabotropic glutamate receptor 5 in low [Mg 2+] o-induced interictal epileptiform activity in rat hippocampal slices. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2024; 28:413-422. [PMID: 39198222 PMCID: PMC11362004 DOI: 10.4196/kjpp.2024.28.5.413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Revised: 04/26/2024] [Accepted: 05/01/2024] [Indexed: 09/01/2024]
Abstract
Group I metabotropic glutamate receptors (mGluRs) modulate postsynaptic neuronal excitability and epileptogenesis. We investigated roles of group I mGluRs on low extracellular Mg2+ concentration ([Mg2+]o)-induced epileptiform activity and neuronal cell death in the CA1 regions of isolated rat hippocampal slices without the entorhinal cortex using extracellular recording and propidium iodide staining. Exposure to Mg2+-free artificial cerebrospinal fluid can induce interictal epileptiform activity in the CA1 regions of rat hippocampal slices. MPEP, a mGluR 5 antagonist, significantly inhibited the spike firing of the low [Mg2+]o-induced epileptiform activity, whereas LY367385, a mGluR1 antagonist, did not. DHPG, a group 1 mGluR agonist, significantly increased the spike firing of the epileptiform activity. U73122, a PLC inhibitor, inhibited the spike firing. Thapsigargin, an ER Ca2+-ATPase antagonist, significantly inhibited the spike firing and amplitude of the epileptiform activity. Both the IP3 receptor antagonist 2-APB and the ryanodine receptor antagonist dantrolene significantly inhibited the spike firing. The PKC inhibitors such as chelerythrine and GF109203X, significantly increased the spike firing. Flufenamic acid, a relatively specific TRPC 1, 4, 5 channel antagonist, significantly inhibited the spike firing, whereas SKF96365, a relatively non-specific TRPC channel antagonist, did not. MPEP significantly decreased low [Mg2+]o DMEM-induced neuronal cell death in the CA1 regions, but LY367385 did not. We suggest that mGluR 5 is involved in low [Mg2+]oinduced interictal epileptiform activity in the CA1 regions of rat hippocampal slices through PLC, release of Ca2+ from intracellular stores and PKC and TRPC channels, which could be involved in neuronal cell death.
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Affiliation(s)
- Ji Seon Yang
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
- Catholic Neuroscience Institute, The Catholic University of Korea, Seoul 06591, Korea
| | - Hyun-Jong Jang
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
- Catholic Neuroscience Institute, The Catholic University of Korea, Seoul 06591, Korea
| | - Ki-Wug Sung
- Catholic Neuroscience Institute, The Catholic University of Korea, Seoul 06591, Korea
- Department of Pharmacology, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
| | - Duck-Joo Rhie
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
- Catholic Neuroscience Institute, The Catholic University of Korea, Seoul 06591, Korea
| | - Shin Hee Yoon
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
- Catholic Neuroscience Institute, The Catholic University of Korea, Seoul 06591, Korea
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3
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Burgdorf J, Zhang XL, Weiss C, Gross A, Boikess SR, Kroes RA, Khan MA, Burch RM, Rex CS, Disterhoft JF, Stanton PK, Moskal JR. The long-lasting antidepressant effects of rapastinel (GLYX-13) are associated with a metaplasticity process in the medial prefrontal cortex and hippocampus. Neuroscience 2015; 308:202-11. [PMID: 26343295 DOI: 10.1016/j.neuroscience.2015.09.004] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Revised: 08/28/2015] [Accepted: 09/01/2015] [Indexed: 01/14/2023]
Abstract
Rapastinel (GLYX-13) is an N-methyl-d-aspartate receptor (NMDAR) modulator that has characteristics of a glycine site partial agonist. Rapastinel is a robust cognitive enhancer and facilitates hippocampal long-term potentiation (LTP) of synaptic transmission in slices. In human clinical trials, rapastinel has been shown to produce marked antidepressant properties that last for at least one week following a single dose. The long-lasting antidepressant effect of a single dose of rapastinel (3mg/kg IV) was assessed in rats using the Porsolt, open field and ultrasonic vocalization assays. Cognitive enhancement was examined using the Morris water maze, positive emotional learning, and contextual fear extinction tests. LTP was assessed in hippocampal slices. Dendritic spine morphology was measured in the dentate gyrus and the medial prefrontal cortex. Significant antidepressant-like or cognitive enhancing effects were observed that lasted for at least one week in each model. Rapastinel facilitated LTP 1day-2weeks but not 4weeks post-dosing. Biweekly dosing with rapastinel sustained this effect for at least 8weeks. A single dose of rapastinel increased the proportion of whole-cell NMDAR current contributed by NR2B-containing NMDARs in the hippocampus 1week post-dosing, that returned to baseline by 4weeks post-dosing. The NMDAR antagonist 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) blocked the antidepressant-like effect of rapastinel 1week post dosing. A single injection of rapastinel also increased mature spine density in both brain regions 24h post-dosing. These data demonstrate that rapastinel produces its long-lasting antidepressant effects via triggering NMDAR-dependent processes that lead to increased sensitivity to LTP that persist for up to two weeks. These data also suggest that these processes led to the alterations in dendritic spine morphologies associated with the maintenance of long-term changes in synaptic plasticity associated with learning and memory.
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Affiliation(s)
- J Burgdorf
- Falk Center for Molecular Therapeutics, Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, 1801 Maple Avenue, Suite 4300, Evanston, IL 60201, USA
| | - X-L Zhang
- Department of Cell Biology & Anatomy, Basic Sciences Building, Room 217, New York Medical College, Valhalla, NY 10595, USA
| | - C Weiss
- Department of Physiology, Northwestern University Feinberg School of Medicine, 303 East Chicago Avenue, Ward Building 7-140, Chicago, IL 60611, USA
| | - A Gross
- Naurex Inc., 1801 Maple Avenue, Suite 4300, Evanston, IL 60201, USA
| | - S R Boikess
- Afraxis Inc., 11099 North Torrey Pines Road, Suite 290, La Jolla, CA 92037, USA
| | - R A Kroes
- Naurex Inc., 1801 Maple Avenue, Suite 4300, Evanston, IL 60201, USA
| | - M A Khan
- Naurex Inc., 1801 Maple Avenue, Suite 4300, Evanston, IL 60201, USA
| | - R M Burch
- Naurex Inc., 1801 Maple Avenue, Suite 4300, Evanston, IL 60201, USA
| | - C S Rex
- Afraxis Inc., 11099 North Torrey Pines Road, Suite 290, La Jolla, CA 92037, USA
| | - J F Disterhoft
- Department of Physiology, Northwestern University Feinberg School of Medicine, 303 East Chicago Avenue, Ward Building 7-140, Chicago, IL 60611, USA
| | - P K Stanton
- Department of Cell Biology & Anatomy, Basic Sciences Building, Room 217, New York Medical College, Valhalla, NY 10595, USA
| | - J R Moskal
- Falk Center for Molecular Therapeutics, Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, 1801 Maple Avenue, Suite 4300, Evanston, IL 60201, USA; Naurex Inc., 1801 Maple Avenue, Suite 4300, Evanston, IL 60201, USA.
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4
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Atwood BK, Lovinger DM, Mathur BN. Presynaptic long-term depression mediated by Gi/o-coupled receptors. Trends Neurosci 2014; 37:663-73. [PMID: 25160683 DOI: 10.1016/j.tins.2014.07.010] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 07/09/2014] [Accepted: 07/25/2014] [Indexed: 01/20/2023]
Abstract
Long-term depression (LTD) of the efficacy of synaptic transmission is now recognized as an important mechanism for the regulation of information storage and the control of actions, as well as for synapse, neuron, and circuit development. Studies of LTD mechanisms have focused mainly on postsynaptic AMPA-type glutamate receptor trafficking. However, the focus has now expanded to include presynaptically expressed plasticity, the predominant form being initiated by presynaptically expressed Gi/o-coupled metabotropic receptor (Gi/o-GPCR) activation. Several forms of LTD involving activation of different presynaptic Gi/o-GPCRs as a 'common pathway' are described. We review here the literature on presynaptic Gi/o-GPCR-mediated LTD, discuss known mechanisms, gaps in our knowledge, and evaluate whether all Gi/o-GPCRs are capable of inducing presynaptic LTD.
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Affiliation(s)
- Brady K Atwood
- Section on Synaptic Pharmacology, Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, US National Institutes of Health, 5625 Fishers Lane, MSC 9411, Bethesda, MD 20852-9411, USA
| | - David M Lovinger
- Section on Synaptic Pharmacology, Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, US National Institutes of Health, 5625 Fishers Lane, MSC 9411, Bethesda, MD 20852-9411, USA
| | - Brian N Mathur
- Department of Pharmacology, University of Maryland, School of Medicine, Baltimore, MD 21201, USA.
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5
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Rodríguez-Durán LF, Escobar ML. NMDA receptor activation and PKC but not PKA lead to the modification of the long-term potentiation in the insular cortex induced by conditioned taste aversion: Differential role of kinases in metaplasticity. Behav Brain Res 2014; 266:58-62. [DOI: 10.1016/j.bbr.2014.02.049] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Revised: 02/20/2014] [Accepted: 02/27/2014] [Indexed: 11/15/2022]
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6
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Liu MG, Zhuo M. Loss of long-term depression in the insular cortex after tail amputation in adult mice. Mol Pain 2014; 10:1. [PMID: 24398034 PMCID: PMC3912895 DOI: 10.1186/1744-8069-10-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Accepted: 12/30/2013] [Indexed: 01/01/2023] Open
Abstract
The insular cortex (IC) is an important forebrain structure involved in pain perception and taste memory formation. Using a 64-channel multi-electrode array system, we recently identified and characterized two major forms of synaptic plasticity in the adult mouse IC: long-term potentiation (LTP) and long-term depression (LTD). In this study, we investigate injury-related metaplastic changes in insular synaptic plasticity after distal tail amputation. We found that tail amputation in adult mice produced a selective loss of low frequency stimulation-induced LTD in the IC, without affecting (RS)-3,5-dihydroxyphenylglycine (DHPG)-evoked LTD. The impaired insular LTD could be pharmacologically rescued by priming the IC slices with a lower dose of DHPG application, a form of metaplasticity which involves activation of protein kinase C but not protein kinase A or calcium/calmodulin-dependent protein kinase II. These findings provide important insights into the synaptic mechanisms of cortical changes after peripheral amputation and suggest that restoration of insular LTD may represent a novel therapeutic strategy against the synaptic dysfunctions underlying the pathophysiology of phantom pain.
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Affiliation(s)
| | - Min Zhuo
- Center for Neuron and Disease, Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an 710049, China.
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Parvez S, Ramachandran B, Frey JU. Properties of subsequent induction of long-term potentiation and/or depression in one synaptic input in apical dendrites of hippocampal CA1 neurons in vitro. Neuroscience 2010; 171:712-20. [PMID: 20850506 DOI: 10.1016/j.neuroscience.2010.09.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Revised: 09/02/2010] [Accepted: 09/10/2010] [Indexed: 11/17/2022]
Abstract
The hippocampus is a prominent structure to study mechanisms of learning and memory at the cellular level. Long-term potentiation (LTP) as well as long-term depression (LTD) are the major cellular models which could underlie learning and memory formation. LTP and LTD consist of at least two phases, an early protein synthesis-independent transient stage (<4 h; E-LTP, E-LTD) as well as a prolonged phase (>4 h; L-LTP, L-LTD) requiring the synthesis of new proteins. It is known that during E-LTP the further induction of longer lasting LTP is precluded. However, if E-LTP is transformed into L-LTP, the same synapses now allow the induction of LTP again. We reproduced the LTP-results first and then investigated whether hippocampal LTP or LTD also prevents the establishment of subsequent LTD-induction in the same synaptic input. We show that the prior induction of LTP or LTD does not prevent a short-term depression (STD) but occludes LTD in apical dendrites of CA1 neurons in hippocampal slices in vitro during the early phase of LTP or LTD. However, LTD can again be induced in addition to STD after the establishment of L-LTP or L-LTD, that is about 4 h after the induction of the first event in the same synaptic input. We suggest that the neuronal input preserves the capacity for STD immediately after an initial potentiation or depression, but for the onset of additional longer lasting LTD in the same synaptic input, the establishment of the late plasticity form of the preceding event is critical.
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Affiliation(s)
- S Parvez
- Department of Neurophysiology, Leibniz-Institute for Neurobiology, Brenneckestrasse 6, 39118 Magdeburg, Germany
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8
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Coincidence detection and stress modulation of spike time-dependent long-term depression in the hippocampus. J Neurosci 2010; 30:6225-35. [PMID: 20445048 DOI: 10.1523/jneurosci.6411-09.2010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Associative long-term depression (LTD) in the hippocampus is a form of spike time-dependent synaptic plasticity that is induced by the asynchronous pairing of postsynaptic action potentials and EPSPs. Although metabotropic glutamate receptors (mGluRs) and postsynaptic Ca(2+) signaling have been suggested to mediate associative LTD, mechanisms are unclear further downstream. Here we show that either mGluR1 or mGluR5 activation is necessary for LTD induction, which is therefore mediated by group I mGluRs. Inhibition of postsynaptic phospholipase C, inositol-1,4,5-trisphosphate, and PKC prevents associative LTD. Activation of PKC by a phorbol ester causes a presynaptic potentiation of synaptic responses and facilitates LTD induction by a postsynaptic mechanism. Lithium, an inhibitor of the PKC pathway, inhibits LTD and the presynaptic and postsynaptic effects of the phorbol ester. Furthermore, LTD is sensitive to the postsynaptic application of synthetic peptides that inhibit the interaction of AMPA receptors with PDZ domains, suggesting an involvement of protein interacting with C-kinase 1 (PICK1)-mediated receptor endocytosis. Finally, enhanced PKC phosphorylation, induced by behavioral stress, is associated with enhanced LTD. Both increased PKC phosphorylation and stress-induced LTD facilitation can be reversed by lithium, indicating that this clinically used mood stabilizer may act on synaptic depression via PKC modulation. These data suggest that PKC mediates the expression of associative LTD via the PICK1-dependent internalization of AMPA receptors. Moreover, modulation of the PKC activity adjusts the set point for LTD induction in a behavior-dependent manner.
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Phosphatidylinositol-linked novel D(1) dopamine receptor facilitates long-term depression in rat hippocampal CA1 synapses. Neuropharmacology 2009; 57:164-71. [PMID: 19465033 DOI: 10.1016/j.neuropharm.2009.05.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2008] [Revised: 05/02/2009] [Accepted: 05/05/2009] [Indexed: 11/23/2022]
Abstract
Recent work has demonstrated that a phosphatidylinositol (PI)-linked D(1) dopamine receptor selective agonist, SKF83959, mediates phosphatidylinositol hydrolysis via activation of phospholipase C(beta) in brain. Specific contributions of SKF83959 to synaptic plasticity have not been well elucidated. The aim of the current investigation was to characterize the role of SKF83959 on long-term depression (LTD) in the CA1 region of rat hippocampal slices and to explore the molecular events leading to these changes. The results indicated that SKF83959 stimulation significantly depressed field excitatory postsynaptic potentials (fEPSPs) in a dose-dependent manner and facilitated the induction of LTD by LFS. SKF83959-facilitated LTD required activation of phospholipase C (PLC). NMDA receptors were involved in this response. Calcium chelator, BAPTA-AM prevented SKF83959-facilitated LTD, indicating that cytosolic free calcium concentration ([Ca(2+)](i)) elevation could account for this response. Furthermore, SKF83959-facilitated LTD was significantly depressed in the presence of calcineurin (PP2B) inhibitors cyclosporin A (CsA) and associated with a persistent increase in the expression of calcineurin A. Taken together, these findings demonstrate a novel role for PI-linked D(1) dopamine receptor in the neuromodulation of hippocampal LTD.
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10
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Abraham WC. Metaplasticity: tuning synapses and networks for plasticity. Nat Rev Neurosci 2008; 9:387. [PMID: 18401345 DOI: 10.1038/nrn2356] [Citation(s) in RCA: 705] [Impact Index Per Article: 41.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Synaptic plasticity is a key component of the learning machinery in the brain. It is vital that such plasticity be tightly regulated so that it occurs to the proper extent at the proper time. Activity-dependent mechanisms that have been collectively termed metaplasticity have evolved to help implement these essential computational constraints. Various intercellular signalling molecules can trigger lasting changes in the ability of synapses to express plasticity; their mechanisms of action are reviewed here, along with a consideration of how metaplasticity might affect learning and clinical conditions.
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Affiliation(s)
- Wickliffe C Abraham
- Department of Psychology and the Brain Health and Repair Research Centre, University of Otago, BOX 56, Dunedin, 9054, New Zealand.
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11
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Spatial learning in the holeboard impairs an early phase of long-term potentiation in the rat hippocampal CA1-region. Neurobiol Learn Mem 2008; 89:545-51. [DOI: 10.1016/j.nlm.2007.11.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2007] [Revised: 11/15/2007] [Accepted: 11/19/2007] [Indexed: 10/22/2022]
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12
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Artola A. Diabetes-, stress- and ageing-related changes in synaptic plasticity in hippocampus and neocortex — The same metaplastic process? Eur J Pharmacol 2008; 585:153-62. [DOI: 10.1016/j.ejphar.2007.11.084] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2007] [Revised: 10/04/2007] [Accepted: 11/15/2007] [Indexed: 10/22/2022]
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Pöschel B, Stanton PK. Comparison of cellular mechanisms of long-term depression of synaptic strength at perforant path-granule cell and Schaffer collateral-CA1 synapses. PROGRESS IN BRAIN RESEARCH 2007; 163:473-500. [PMID: 17765734 DOI: 10.1016/s0079-6123(07)63026-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
This chapter compares the cellular mechanisms that have been implicated in the induction and expression of long-term depression (LTD) at Schaffer collateral-CA1 synapses to perforant path-dentate gyrus (DG) synapses. In general, Schaffer collateral LTD and long-term potentiation (LTP) both appear to be a complex combination of many alterations in synaptic transmission that occur at both presynaptic and postsynaptic sites, while at perforant path synapses, most evidence has focused on postsynaptic long-term alterations. Within the DG, the medial perforant path is far more studied than lateral perforant path synapses, where most evidence relates to the induction of heterosynaptic LTD at lateral perforant path synapses when LTP is induced in the medial perforant path. Of course, there remain many other classes of synapses in the DG where synaptic plasticity, including LTD, have been largely neglected. It is clear that a better understanding of the range of DG loci where long-lasting activity-dependent plasticity, both LTD and LTP, are expressed will be essential to improve our understanding of the cognitive roles of such DG plasticity.
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Affiliation(s)
- Beatrice Pöschel
- Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY 10595, USA
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14
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Zhabotinsky AM, Camp RN, Epstein IR, Lisman JE. Role of the neurogranin concentrated in spines in the induction of long-term potentiation. J Neurosci 2006; 26:7337-47. [PMID: 16837580 PMCID: PMC6674191 DOI: 10.1523/jneurosci.0729-06.2006] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Synaptic plasticity in CA1 hippocampal neurons depends on Ca2+ elevation and the resulting activation of calmodulin-dependent enzymes. Induction of long-term depression (LTD) depends on calcineurin, whereas long-term potentiation (LTP) depends on Ca2+/calmodulin-dependent protein kinase II (CaMKII). The concentration of calmodulin in neurons is considerably less than the total concentration of the apocalmodulin-binding proteins neurogranin and GAP-43, resulting in a low level of free calmodulin in the resting state. Neurogranin is highly concentrated in dendritic spines. To elucidate the role of neurogranin in synaptic plasticity, we constructed a computational model with emphasis on the interaction of calmodulin with neurogranin, calcineurin, and CaMKII. The model shows how the Ca2+ transients that occur during LTD or LTP induction affect calmodulin and how the resulting activation of calcineurin and CaMKII affects AMPA receptor-mediated transmission. In the model, knockout of neurogranin strongly diminishes the LTP induced by a single 100 Hz, 1 s tetanus and slightly enhances LTD, in accord with experimental data. Our simulations show that exchange of calmodulin between a spine and its parent dendrite is limited. Therefore, inducing LTP with a short tetanus requires calmodulin stored in spines in the form of rapidly dissociating calmodulin-neurogranin complexes.
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Affiliation(s)
- Anatol M Zhabotinsky
- Department of Chemistry, Brandeis University, Waltham, Massachusetts 02454-9110, USA.
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15
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Artola A, von Frijtag JC, Fermont PCJ, Gispen WH, Schrama LH, Kamal A, Spruijt BM. Long-lasting modulation of the induction of LTD and LTP in rat hippocampal CA1 by behavioural stress and environmental enrichment. Eur J Neurosci 2006; 23:261-72. [PMID: 16420435 DOI: 10.1111/j.1460-9568.2005.04552.x] [Citation(s) in RCA: 184] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Behavioural experience (e.g. chronic stress, environmental enrichment) can have long-lasting effects on cognitive functions. Because activity-dependent persistent changes in synaptic strength are believed to mediate memory processes in brain areas such as hippocampus, we tested whether behaviour has also long-lasting effects on synaptic plasticity by examining the induction of long-term potentiation (LTP) and long-term depression (LTD) in slices of hippocampal CA1 obtained from rats either 7-9 months after social defeat (behavioural stress) or 3-5 weeks after 5-week exposure to environmental enrichment. Compared with age-matched controls, defeated rats showed markedly reduced LTP. LTP was even completely impaired but LTD was enhanced in defeated and, subsequently, individually housed (during the 7-9-month period after defeat) rats. However, increasing stimulus intensity during 100-Hz stimulation resulted in significant LTP. This suggests that the threshold for LTP induction is still raised and that for LTD lowered several months after a short stressful experience. Both LTD and LTP were enhanced in environmentally enriched rats, 3-5 weeks after enrichment, as compared with age-matched controls. Because enrichment reduced paired-pulse facilitation, an increase in presynaptic release, facilitating both LTD and LTP induction, might contribute to enhanced synaptic changes. Consistently, enrichment reduced the number of 100-Hz stimuli required for inducing LTP. But enrichment may also actually enhance the range of synaptic modification. Repeated LTP and LTD induction produced larger synaptic changes in enriched than in control rats. These data reveal that exposure to very different behavioural experiences can produce long-lasting effects on the susceptibility to synaptic plasticity, involving pre- and postsynaptic processes.
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Affiliation(s)
- Alain Artola
- Department of Animals, Science & Society, Utrecht University, Yalelaan 2, 3584 CM, Utrecht, The Netherlands
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16
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Perez-Pinzon MA, Raval AP, Dave KR. Protein kinase C and synaptic dysfunction after cardiac arrest. PATHOPHYSIOLOGY 2005; 12:29-34. [PMID: 15927822 DOI: 10.1016/j.pathophys.2005.02.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2005] [Accepted: 02/18/2005] [Indexed: 11/21/2022] Open
Abstract
It is now understood that the mechanisms leading to neuronal cell death after cardiac arrest (CA) are highly complex. A well established fact in this field is that neurons continue to die over days and months after ischemia. It has been suggested that decreases in electrophysiological activities precede the morphologic deterioration in postischemic CA1 neurons and that this deterioration may be one cause for delayed cell death. The link between synaptic dysfunction and cardiac arrest is evident by the fact that about 50% of long-term survivors of cardiac arrest exhibit impaired mental abilities, manifested as learning impairment, memory disturbance. Since PKC is known to be a key player in synaptic function and has been implicated in promoting cell death after cerebral ischemia, it is a logical candidate as a modulator of synaptic derangements after CA. In this review, we provide an overview of synaptic dysfunction following CA and the putative role of PKC on this dysfunction.
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Affiliation(s)
- Miguel A Perez-Pinzon
- Cerebral Vascular Disease Research Center, Department of Neurology (D4-5) and Neuroscience Program, University of Miami School of Medicine, PO Box 016960, Miami, FL-33101, USA
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17
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Artola A, Kamal A, Ramakers GMJ, Biessels GJ, Gispen WH. Diabetes mellitus concomitantly facilitates the induction of long-term depression and inhibits that of long-term potentiation in hippocampus. Eur J Neurosci 2005; 22:169-78. [PMID: 16029206 DOI: 10.1111/j.1460-9568.2005.04205.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Memory impairments, which occur regularly across species as a result of ageing, disease (such as diabetes mellitus) and psychological insults, constitute a useful area for investigating the neurobiological basis of learning and memory. Previous studies in rats found that induction of diabetes (with streptozotocin, STZ) impairs long-term potentiation (LTP) but enhances long-term depression (LTD) induced by high- (HFS) and low-frequency stimulations (LFS), respectively. Using a pairing protocol under whole-cell recording conditions to induce synaptic plasticity at Schaffer collateral synapses in hippocampal CA1 slices, we show that LTD and LTP have similar magnitudes in diabetic and age-matched control rats. But, in diabetic animals, LTD is induced at more polarized and LTP more depolarized membrane potentials (V(ms)) compared with controls: diabetes produces a 10 mV leftward shift in the threshold for LTD induction and 10 mV rightward shift in the LTD-LTP crossover point of the voltage-response curve for synaptic plasticity. Prior repeated short-term potentiations or LTP are known to similarly, though reversibly, lower the threshold for LTD induction and raise that for LTP induction. Thus, diabetes- and activity-dependent modulation of synaptic plasticity (referred to as metaplasticity) display similar phenomenologies. In addition, compared with naïve synapses, prior induction of LTP produces a 10 mV leftward shift in Vms for inducing subsequent LTD in control but not in diabetic rats. This could indicate that diabetes acts on synaptic plasticity through mechanisms involved in metaplasticity. Persistent facilitation of LTD and inhibition of LTP may contribute to learning and memory impairments associated with diabetes mellitus.
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Affiliation(s)
- A Artola
- Department of Pharmacology and Anatomy, Rudolf Magnus Institute of Neuroscience, University Medical Centre Utrecht, Utrecht, The Netherlands.
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18
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Froc DJ, Racine RJ. Interactions Between LTP- and LTD-Inducing Stimulation in the Sensorimotor Cortex of the Awake Freely Moving Rat. J Neurophysiol 2005; 93:548-56. [PMID: 15356176 DOI: 10.1152/jn.00253.2004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Bidirectional modifications in synaptic efficacy are central components in models of cortical learning and memory. More recently, the regulation of synaptic plasticity according to the history of synaptic activation, termed “metaplasticity,” has become a focus of research on the physiology of memory. Here we explore such interactions between long-term potentiation (LTP) and long-term depression (LTD) in the chronically prepared rat. The effects of successive high- and low-frequency stimulation were examined in sensorimotor cortex in the adult, freely moving rat. High-frequency (300 Hz) stimulation (HFS) applied to the white matter was used to induce LTP, and prolonged, low-frequency (1 Hz) stimulation (LFS) was used to induce either depotentiation or LTD. Combined stimulation (HFS/LFS or LFS/HFS) during the induction phase attenuated potentiation effects only if the LFS followed the HFS. LTD induced by LFS alone was expressed as a reduction in the amplitude of both short- and long-latency field potential components, whereas depotentiation was primarily expressed as a decrease in the amplitude of the potentiated long-latency component. In other experiments, LTP (or LTD) was induced to asymptotic levels before applying LFS (or HFS). LFS caused depotentiation of the late component but had no measurable effect on the early component. HFS reversed previously induced LTD, but the potentiation decayed more rapidly than usual. LTP and LTD therefore modulate each other in the awake, behaving rat.
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Affiliation(s)
- David J Froc
- Department of Psychology, McMaster University, Hamilton, Ontario, L8S 4K1, Canada
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19
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Monfils MH, Teskey GC. Induction of long-term depression is associated with decreased dendritic length and spine density in layers III and V of sensorimotor neocortex. Synapse 2004; 53:114-21. [PMID: 15170823 DOI: 10.1002/syn.20039] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Long-term potentiation (LTP) and long-term depression (LTD) are currently the most widely investigated models of the synaptic mechanisms underlying learning and memory. Previous research has shown that induction of LTP increases measures of pyramidal cell dendritic morphology in the hippocampus and layers III and V of the neocortex. However, to date there are no reports on the direct effects of LTD induction on dendritic morphology. Here, we investigated the effects of LTD induction on sensorimotor pyramidal cell dendritic morphology. Rats carried a stimulating electrode in the corpus callosum (midline) and a recording electrode in the right sensorimotor cortex. Each rat received low-frequency stimulation composed of 900 pulses at 1 Hz or handling daily for a total 15 days. Evoked potentials (EPs) of the transcallosal pathway were recorded in the right hemisphere before and after the 15 days of stimulation or handling. The rats were then perfused with saline and the brains were immediately processed for Golgi-Cox staining. Our results show that LTD induction is related to decreases in dendritic length and spine density both in layers III and V as well as a decrease in dendritic branch complexity in layer V of the sensorimotor cortex. Thus, neuronal alterations following modifications in neocortical synaptic efficacy may provide a general mechanism for the physical instantiation of learning and memory.
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Affiliation(s)
- Marie-H Monfils
- Behavioural Neuroscience Research Group, Department of Psychology, University of Calgary, Alberta, Canada, T2N 1N4
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20
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Nijholt I, Farchi N, Kye M, Sklan EH, Shoham S, Verbeure B, Owen D, Hochner B, Spiess J, Soreq H, Blank T. Stress-induced alternative splicing of acetylcholinesterase results in enhanced fear memory and long-term potentiation. Mol Psychiatry 2004; 9:174-83. [PMID: 14581933 DOI: 10.1038/sj.mp.4001446] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Stress insults intensify fear memory; however, the mechanism(s) facilitating this physiological response is still unclear. Here, we report the molecular, neurophysiological and behavioral findings attributing much of this effect to alternative splicing of the acetylcholinesterase (AChE) gene in hippocampal neurons. As a case study, we explored immobilization-stressed mice with intensified fear memory and enhanced long-term potentiation (LTP), in which alternative splicing was found to induce overproduction of neuronal 'readthrough' AChE-R (AChE-R). Selective downregulation of AChE-R mRNA and protein by antisense oligonucleotides abolished the stress-associated increase in AChE-R, the elevation of contextual fear and LTP in the hippocampal CA1 region. Reciprocally, we intrahippocampally injected a synthetic peptide representing the C-terminal sequence unique to AChE-R. The injected peptide, which has been earlier found to exhibit no enzymatic activity, was incorporated into cortical, hippocampal and basal nuclei neurons by endocytosis and retrograde transport and enhanced contextual fear. Compatible with this hypothesis, inherited AChE-R overexpression in transgenic mice resulted in perikaryal clusters enriched with PKCbetaII, accompanied by PKC-augmented LTP enhancement. Our findings demonstrate a primary role for stress-induced alternative splicing of the AChE gene to elevated contextual fear and synaptic plasticity, and attribute to the AChE-R splice variant a major role in this process.
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Affiliation(s)
- I Nijholt
- Department of Molecular Neuroendocrinology, Max Planck Institute for Experimental Medicine, Goettingen, Germany
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21
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Gisabella B, Rowan MJ, Anwyl R. Mechanisms underlying the inhibition of long-term potentiation by preconditioning stimulation in the hippocampus in vitro. Neuroscience 2003; 121:297-305. [PMID: 14521989 DOI: 10.1016/s0306-4522(03)00440-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We have investigated the mechanisms underlying a form of metaplasticity, namely the inhibition by preconditioning stimulation of high frequency stimulation (HFS)-induced long-term potentiation (LTP) in the medial perforant path of the dentate gyrus. Preconditioning stimulation (weak 50 Hz) was found to inhibit subsequent LTP induction if applied 10-20 min, but not 2 or 45 min, prior to the HFS. Preconditioning stimulation in the form of low frequency stimulation did not block LTP induction. The inhibition of LTP was not caused by a reduction in N-methyl-D-aspartate receptor (NMDAR) transmission, as the preconditioning stimulation did not reduce isolated NMDAR-mediated EPSPs. The involvement of group I and group II metabotropic glutamate receptor (mGluR) activation in the inhibition of LTP was demonstrated by experiments in which the inhibition of LTP by the preconditioning stimulation was prevented by the presence of antagonists of group I or group II mGluR during the preconditioning stimulation. Moreover, group I and group II mGluR agonists directly inhibited subsequent LTP induction. The involvement of NMDAR in the preconditioning stimulation was shown by the ability of an NMDAR antagonist to prevent the inhibition of LTP by the preconditioning stimulation. The preconditioning inhibition of LTP induction was shown by the use of kinase inhibitors to involve activation of PKC and p38 MAP kinase, but not p42 MAP kinase or tyrosine kinase. We conclude that the preconditioning inhibition of LTP induction is a complex process which involves activation of NMDAR, group I and group II mGluR, and intracellular cascades activating PKC and p38 MAP kinase.
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Affiliation(s)
- B Gisabella
- Department of Physiology, Trinity College, Dublin 2, Ireland
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22
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Mockett B, Coussens C, Abraham WC. NMDA receptor-mediated metaplasticity during the induction of long-term depression by low-frequency stimulation. Eur J Neurosci 2002; 15:1819-26. [PMID: 12081662 DOI: 10.1046/j.1460-9568.2002.02008.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Metaplasticity refers to the activity-dependent modification of the ability of synapses to undergo subsequent synaptic plasticity. Here, we have addressed the question of whether metaplasticity contributes to the induction of long-term depression (LTD) by low-frequency stimulation (LFS). The experiments were conducted using standard extracellular recording techniques in stratum radiatum of area CA1 in hippocampal slices made from adult Sprague-Dawley rats. The degree of LTD induction was found to be a nonlinear function of the number of pulses during a 1-Hz LFS. Little LTD was observed following 600 or 900 pulses, but a significant LTD occurred following 1200 pulses of LFS, whether delivered in one episode, or in two bouts of 600 pulses given 10 min apart. A similar pattern was observed for 3 Hz LFS. The data support the suggestion that pulses occurring early in the LFS train prime synapses for LTD induction, as triggered by later occurring stimuli. The priming effect lasted at least 120 min, when tested by giving two bouts of 1 Hz LFS (600 pulses each) at different intervals. Neither heterosynaptic nor homosynaptic stimulation by itself was sufficient to prime LTD. However, a combination of the stimuli, induced by increased stimulus strength during the LFS, appeared necessary for inducing the effect. An N-methyl-d-aspartate (NMDA) receptor antagonist markedly reduced total LTD induction, regardless of whether it was administered during the first or second LFS in a protocol employing two bouts of 600 pulse LFS, 30 min apart. These findings strongly support the hypothesis that NMDA receptor-dependent metaplasticity processes contribute to the induction of LTD during standard LFS protocols.
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Affiliation(s)
- Bruce Mockett
- Department of Psychology and the Neuroscience Research Centre, University of Otago, Box 56, Dunedin, New Zealand.
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23
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Rapid synaptic remodeling by protein kinase C: reciprocal translocation of NMDA receptors and calcium/calmodulin-dependent kinase II. J Neurosci 2002. [PMID: 11896155 DOI: 10.1523/jneurosci.22-06-02153.2002] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In contrast to the rapid regulation of AMPA receptors, previous evidence has supported the idea that the synaptic density of NMDA-type glutamate receptors is fairly static, modulated only over a long time scale in a homeostatic manner. We report here that selective activation of protein kinase C (PKC) with phorbol esters induces a rapid dispersal of NMDA receptors from synaptic to extrasynaptic plasma membrane in cultured rat hippocampal neurons. PKC activation induced a simultaneous translocation of calcium/calmodulin-dependent kinase II (CaMKII) to synapses but no change in spine number, presynaptic terminal number, or the distribution of AMPA receptors or the synaptic scaffolding protein PSD-95. PKC-induced accumulation of CaMKII was dependent on filamentous actin, whereas dispersal of NMDA receptors occurred by a different mechanism independent of actin or CaMKII. Consistent with the decrease in synaptic density of NMDA receptors, phorbol ester pretreatment reduced excitotoxicity. These results reveal a surprisingly dynamic nature to the molecular composition and functional properties of glutamatergic postsynaptic specializations.
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24
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Fong DK, Rao A, Crump FT, Craig AM. Rapid synaptic remodeling by protein kinase C: reciprocal translocation of NMDA receptors and calcium/calmodulin-dependent kinase II. J Neurosci 2002; 22:2153-64. [PMID: 11896155 PMCID: PMC6758278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023] Open
Abstract
In contrast to the rapid regulation of AMPA receptors, previous evidence has supported the idea that the synaptic density of NMDA-type glutamate receptors is fairly static, modulated only over a long time scale in a homeostatic manner. We report here that selective activation of protein kinase C (PKC) with phorbol esters induces a rapid dispersal of NMDA receptors from synaptic to extrasynaptic plasma membrane in cultured rat hippocampal neurons. PKC activation induced a simultaneous translocation of calcium/calmodulin-dependent kinase II (CaMKII) to synapses but no change in spine number, presynaptic terminal number, or the distribution of AMPA receptors or the synaptic scaffolding protein PSD-95. PKC-induced accumulation of CaMKII was dependent on filamentous actin, whereas dispersal of NMDA receptors occurred by a different mechanism independent of actin or CaMKII. Consistent with the decrease in synaptic density of NMDA receptors, phorbol ester pretreatment reduced excitotoxicity. These results reveal a surprisingly dynamic nature to the molecular composition and functional properties of glutamatergic postsynaptic specializations.
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Affiliation(s)
- Dan K Fong
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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25
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Saitoh N, Hori T, Takahashi T. Activation of the epsilon isoform of protein kinase C in the mammalian nerve terminal. Proc Natl Acad Sci U S A 2001; 98:14017-21. [PMID: 11717460 PMCID: PMC61159 DOI: 10.1073/pnas.241333598] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Activation of protein kinase C (PKC) by phorbol ester facilitates hormonal secretion and transmitter release, and phorbol ester-induced synaptic potentiation (PESP) is a model for presynaptic facilitation. A variety of PKC isoforms are expressed in the central nervous system, but the isoform involved in the PESP has not been identified. To address this question, we have applied immunocytochemical and electrophysiological techniques to the calyx of Held synapse in the medial nucleus of the trapezoid body (MNTB) of rat auditory brainstem. Western blot analysis indicated that both the Ca(2+)-dependent "conventional" PKC and Ca(2+)-independent "novel" PKC isoforms are expressed in the MNTB. Denervation of afferent fibers followed by organotypic culture, however, selectively decreased "novel" epsilon PKC isoform expressed in this region. The afferent calyx terminal was clearly labeled with the epsilon PKC immunofluorescence. On stimulation with phorbol ester, presynaptic epsilon PKC underwent autophosphorylation and unidirectional translocation toward the synaptic side. Chelating presynaptic Ca(2+), by using membrane permeable EGTA analogue or high concentration of EGTA directly loaded into calyceal terminals, had only a minor attenuating effect on the PESP. We conclude that the Ca(2+)-independent epsilon PKC isoform mediates the PESP at this mammalian central nervous system synapse.
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Affiliation(s)
- N Saitoh
- Department of Neurophysiology, University of Tokyo, Graduate School of Medicine, Tokyo 113-0033, Japan
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26
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Hrabetova S, Sacktor TC. Transient translocation of conventional protein kinase C isoforms and persistent downregulation of atypical protein kinase Mzeta in long-term depression. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2001; 95:146-52. [PMID: 11687286 DOI: 10.1016/s0169-328x(01)00185-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Persistent dephosphorylation has been implicated in the molecular mechanisms of long-term depression (LTD). Dephosphorylation may be due to either a persistent increase in phosphatase activity or a persistent decrease in kinase activity. We have previously found that protein kinase Mzeta (PKMzeta), the autonomously active form of the atypical PKCzeta isozyme that increases in long-term potentiation (LTP), decreases in LTD. This is consistent with the hypothesis that decreased levels of phosphorylation by PKC are important in LTD. Recently, however, increased phosphorylation by PKC has also been implicated in LTD. These contradictory results might be explained, in part, by the multiple isoforms of PKC, which may be independently regulated during the different phases of LTD. We now find that 45 s after low-frequency (3 Hz) stimulation that induces LTD in the CA1 region of hippocampal slices, conventional Ca(2+)/lipid-dependent PKC isoforms translocate from the cytosol to the membrane. This translocation was transient, lasting less than 15 min. In contrast, PKMzeta was persistently decreased through 2 h of LTD maintenance. Therefore, the activation and downregulation of distinct PKC isoforms may participate in the induction and maintenance mechanisms of LTD.
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Affiliation(s)
- S Hrabetova
- Laboratory of Molecular Neuroscience, Department of Physiology, State University of New York, Downstate Medical Center, 450 Clarkson Avenue, Box 29, Brooklyn, NY 11203, USA
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27
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Hsu KS, Ho WC, Huang CC, Tsai JJ. Transient removal of extracellular Mg(2+) elicits persistent suppression of LTP at hippocampal CA1 synapses via PKC activation. J Neurophysiol 2000; 84:1279-88. [PMID: 10980002 DOI: 10.1152/jn.2000.84.3.1279] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous work has shown that seizure-like activity can disrupt the induction of long-term potentiation (LTP). However, how seizure-like event disrupts the LTP induction remains unknown. To understand the cellular and molecular mechanisms underlying this process better, a set of studies was implemented in area CA1 of rat hippocampal slices using extracellular recording methods. We showed here that prior transient seizure-like activity generated by perfused slices with Mg(2+)-free artificial cerebrospinal fluid (ACSF) exhibited a persistent suppression of LTP induction. This effect lasted between 2 and 3 h after normal ACSF replacement and was specifically inhibited by N-methyl-D-aspartate (NMDA) receptor antagonist D-2-amino-5-phosphovaleric acid (D-APV) and L-type voltage-operated Ca(2+) channel (VOCC) blocker nimodipine, but not by non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). In addition, this suppressive effect was specifically blocked by the selective protein kinase C (PKC) inhibitor NPC-15437. However, neither Ca(2+)/calmodulin-dependent protein kinase II inhibitor KN-62 nor cAMP-dependent protein kinase inhibitor Rp-adenosine 3', 5'-cyclic monophosphothioate (Rp-cAMPS) affected this suppressive effect. This persistent suppression of LTP was not secondary to the long-lasting changes in NMDA receptor activation, because the isolated NMDA receptor-mediated responses did not show a long-term enhancement in response to a 30-min Mg(2+)-free ACSF application. Additionally, in prior Mg(2+)-free ACSF-treated slices, the entire frequency-response curve of LTP and long-term depression (LTD) is shifted systematically to favor LTD. These results suggest that the increase of Ca(2+) influx through NMDA channels and L-type VOCCs in turn triggering a PKC-dependent signaling cascade is a possible cellular basis underlying this seizure-like activity-induced inhibition of LTP.
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Affiliation(s)
- K S Hsu
- Department of Pharmacology, College of Medicine, National Cheng-Kung University, Tainan City, Taiwan.
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28
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Hashimoto R, Nakamura Y, Komai S, Kashiwagi Y, Matsumoto N, Shiosaka S, Takeda M. Phosphorylation of neurofilament-L during LTD. Neuroreport 2000; 11:2739-42. [PMID: 10976954 DOI: 10.1097/00001756-200008210-00026] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We recently reported that CaMKII-dependent phosphorylation of the neurofilament-L (NF-L) head domain was induced in the apical dendrites during long-term potentiation. Long-term depression (LTD) is another cellular model for neuronal plasticity. In the present study, we examined the phosphorylation of NF-L during hippocampal LTD using a series of phospho-specific antibodies against the NF-L head domain. During LTD, these antibodies visualized NF-L phosphorylation at Ser57 in the apical dendrites of the hippocampal pyramidal neurons. The assembly and disassembly of NF-L filaments are regulated by phosphorylation of its head domain. Thus, our results indicated that NF-L phosphorylation might be associated with alterations of the neuronal structure during LTD.
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Affiliation(s)
- R Hashimoto
- Department of Clinical Neuroscience, Psychiatry, Osaka University Graduate School of Medicine, Japan
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29
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Moody TD, Carlisle HJ, O'Dell TJ. A nitric oxide-independent and beta-adrenergic receptor-sensitive form of metaplasticity limits theta-frequency stimulation-induced LTP in the hippocampal CA1 region. Learn Mem 1999; 6:619-33. [PMID: 10641766 PMCID: PMC311307 DOI: 10.1101/lm.6.6.619] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The induction of long-term potentiation (LTP) and long-term depression (LTD) at excitatory synapses in the hippocampus can be strongly modulated by patterns of synaptic stimulation that otherwise have no direct effect on synaptic strength. Likewise, patterns of synaptic stimulation that induce LTP or LTD not only modify synaptic strength but can also induce lasting changes that regulate how synapses will respond to subsequent trains of stimulation. Collectively known as metaplasticity, these activity-dependent processes that regulate LTP and LTD induction allow the recent history of synaptic activity to influence the induction of activity-dependent changes in synaptic strength and may thus have an important role in information storage during memory formation. To explore the cellular and molecular mechanisms underlying metaplasticity, we investigated the role of metaplasticity in the induction of LTP by theta-frequency (5-Hz) synaptic stimulation in the hippocampal CA1 region. Our results show that brief trains of theta-frequency stimulation not only induce LTP but also activate a process that inhibits the induction of additional LTP at potentiated synapses. Unlike other forms of metaplasticity, the inhibition of LTP induction at potentiated synapses does not appear to arise from activity-dependent changes in NMDA receptor function, does not require nitric oxide signaling, and is strongly modulated by beta-adrenergic receptor activation. Together with previous findings, our results indicate that mechanistically distinct forms of metaplasticity regulate LTP induction and suggest that one way modulatory transmitters may act to regulate synaptic plasticity is by modulating metaplasticity.
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Affiliation(s)
- T D Moody
- Interdepartmental Ph.D. Program for Neuroscience, School of Medicine, University of California at Los Angeles, 90095, USA
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30
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Hsu KS, Ho WC, Huang CC, Tsai JJ. Prior short-term synaptic disinhibition facilitates long-term potentiation and suppresses long-term depression at CA1 hippocampal synapses. Eur J Neurosci 1999; 11:4059-69. [PMID: 10583494 DOI: 10.1046/j.1460-9568.1999.00819.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Long-term potentiation (LTP) and long-term depression (LTD) are two main forms of activity-dependent synaptic plasticity that have been extensively studied as the putative mechanisms underlying learning and memory. Current studies have demonstrated that prior synaptic activity can influence the subsequent induction of LTP and LTD at Schaffer collateral-CA1 synapses. Here, we show that prior short-term synaptic disinhibition induced by type A gamma-aminobutyric acid (GABA) receptor antagonist picrotoxin exhibited a facilitation of LTP induction and an inhibition of LTD induction. This effect lasted between 10 and 30 min after washout of picrotoxin and was specifically inhibited by the L-type voltage-operated Ca2+ channel (VOCC) blocker nimodipine, but not by the N-methyl-D-aspartate (NMDA) receptor antagonist D-2-amino-5-phosphopentanoic acid (D-APV). Moreover, this picrotoxin-induced priming effect was mimicked by forskolin, an activator of cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA), and was blocked by the adenylyl cyclase inhibitor 9-(tetrahydro-2-furanyl)-9H-purin-6-amine (SQ 22536) and the PKA inhibitor Rp-adenosine 3',5'-cyclic monophosphothioate (Rp-cAMPS). It was also found that following picrotoxin application, CA1 neurons have a higher probability of synchronous discharge in response to a population of excitatory postsynaptic potential (EPSP) of fixed slope (EPSP/spike potentiation). However, picrotoxin treatment did not significantly affect paired-pulse facilitation (PPF). These findings suggest that a brief of GABAergic disinhibition can act as a priming stimulus for the subsequent induction of LTP and LTD at Schaffer collateral-CA1 synapses. The increase in Ca2+ influx through L-type VOCCs in turn triggering a cAMP/PKA signalling pathway is a possible molecular mechanism underlying this priming effect.
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Affiliation(s)
- K S Hsu
- Department of Pharmacology, College of Medicine, National Cheng-Kung University, Tainan City, Taiwan 70101, ROC
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31
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Migliore M, Lansky P. Long-term potentiation and depression induced by a stochastic conditioning of a model synapse. Biophys J 1999; 77:1234-43. [PMID: 10465738 PMCID: PMC1300415 DOI: 10.1016/s0006-3495(99)76975-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Protracted presynaptic activity can induce long-term potentiation (LTP) or long-term depression (LTD) of the synaptic strength. However, virtually all the experiments testing how LTP and LTD depend on the conditioning input are carried out with trains of stimuli at constant frequencies, whereas neurons in vivo most likely experience a stochastic variation of interstimulus intervals. We used a computational model of synaptic transmission to test if and to what extent the stochastic fluctuations of an input signal could alter the probability to change the state of a synapse. We found that, even if the mean stimulation frequency was maintained constant, the probability to induce LTD and LTP could be a function of the temporal variation of the input activity. This mechanism, which depends only on the statistical properties of the input and not on the onset of additional biochemical mechanisms, is not usually considered in the experiments, but it could have an important role to determine the amount of LTP/LTD induction in vivo. In response to a change in the distribution of the interstimulus intervals, as measured by the coefficient of variation, a synapse could be easily adapted to inputs that might require immediate attention, with a shift of the input thresholds required to elicit LTD or LTP, which are restored to their initial conditions as soon as the input pattern returns to the original temporal distribution.
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Affiliation(s)
- M Migliore
- Institute of Advanced Diagnostic Methodologies, National Research Council, Palermo, Italy.
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Kleshchevnikov AM. Synaptic plasticity in the hippocampus during afferent activation reproducing the pattern of the theta rhythm (theta plasticity). NEUROSCIENCE AND BEHAVIORAL PHYSIOLOGY 1999; 29:185-96. [PMID: 10432508 DOI: 10.1007/bf02465325] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
This review summarizes data on the plasticity of hippocampal synaptic pathways in conditions of afferent activation modeling the electrical activity of neurons during the theta rhythm. Activation with short trains of stimuli with frequencies of about 5 Hz efficiently induces long-term potentiation, i.e., stable facilitation of synaptic transmission. Contrarily, single stimuli presented at the same frequency "depotentiate" synapses or even induce long-term depression. Combined theta activity at two synaptic inputs, in phase with each other, induces long-term potentiation, while combined activity in antiphase produces long-term depression of the weakly-activated input (associative long-term potentiation and depression). Short trains of single stimuli at a frequency of 5 Hz induce heterosynaptic short-term depression: the efficiency of all synaptic inputs is decreased for time periods of the order of 1 min. Apart from changes in synaptic efficiency, theta activation affects the ability to induce synaptic rearrangements in conditions of subsequent afferent activation ("cryptic" plasticity). Thus, virtually all known types of synaptic plasticity are efficiently induced by afferent activation of the pattern of the hippocampal theta rhythm, which suggests the possible mechanisms for its roles in learning and memory processes.
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33
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Wang Y, Wu J, Rowan MJ, Anwyl R. Role of protein kinase C in the induction of homosynaptic long-term depression by brief low frequency stimulation in the dentate gyrus of the rat hippocampus in vitro. J Physiol 1998; 513 ( Pt 2):467-75. [PMID: 9806996 PMCID: PMC2231306 DOI: 10.1111/j.1469-7793.1998.467bb.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
1. Enhancement of the induction of long-term depression (LTD) of excitatory postsynaptic currents (EPSCs) by a priming stimulus was investigated in the medial perforant pathway of the dentate gyrus of the hippocampus in vitro. 2. In control, LTD could be induced by a conditioning low frequency stimulation (LFS) consisting of sixty, although not thirty or fewer, stimuli at 1 Hz applied at a holding potential of -40 mV. 3. A conditioning LFS of just five stimuli at 1 Hz was found to induce LTD if preceded 1-5 min, but not 15 min, by a priming LFS of five stimuli at 1 Hz, -40 mV, which did not by itself induce LTD. 4. A low concentration of the protein kinase C (PKC) activator (-)-indolactam V, which did not itself induce LTD, reduced the threshold for the number of stimuli inducing LTD following the priming stimulus, while a high concentration of (-)-indolactam V directly induced a depression of the test excitatory postsynaptic current (EPSC), which occluded LFS-induced LTD. This suggests that the priming of LTD and also the direct induction of LTD involves the activation of PKC. 5. The pseudosubstrate peptide inhibitor PKC19-36 inhibited the induction of LTD by the priming protocol and by the control induction conditioning protocol. 6. These experiments demonstrate that a covert synaptic change involving generation of PKC is very effective in producing conditions whereby LTD is induced by very brief synaptic stimulation.
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Affiliation(s)
- Y Wang
- Department of Physiology, Trinity College, Dublin 2, Ireland
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Cohen AS, Raymond CR, Abraham WC. Priming of long-term potentiation induced by activation of metabotropic glutamate receptors coupled to phospholipase C. Hippocampus 1998; 8:160-70. [PMID: 9572722 DOI: 10.1002/(sici)1098-1063(1998)8:2<160::aid-hipo8>3.0.co;2-p] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Activation of metabotropic glutamate receptors (mGluRs) with 1-aminocyclopentane-1S,3R-dicarboxylic acid 20 min prior to tetanus facilitates, or "primes," subsequent induction of long-term potentiation (LTP; Cohen and Abraham, J Neurophysiol 1996;76:953-962). In the present study, we investigated the receptor specificity and associated second messenger pathways involved in the mGluR priming effect by using field potentials recorded from area CA1 of rat hippocampal slices. In controls, mild theta-burst or high-frequency (100 Hz) stimulation induced 16% and 21% LTP, respectively. A 10-min application of the group I mGluR agonist 3,5-dihydroxyphenylglycine (DHPG) caused a transient depression of synaptic responses but a significant enhancement of subsequent LTP for both tetanus protocols (45% and 41% LTP, respectively). Maximal LTP, induced by stronger tetanization protocols, was not enhanced by DHPG, nor was mild LTP facilitated by post-tetanic application of DHPG. Priming with agonists selective for group II or III mGluRs had no effect on LTP. The mGluR antagonists L-2-amino-3-phosphonopropionic acid and 1-aminoindan-1,5-dicarboxylic acid inhibited the LTP facilitatory effect of DHPG but not the transient response depression, whereas alpha-methyl-4-carboxyphenylglycine produced the opposite effects. Priming with N-methyl-D-aspartate or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid did not facilitate LTP induction. Prior activation of muscarinic acetylcholine receptors produced at best a weak priming effect. Inhibition of phospholipase C by U-73122 completely abolished the priming of LTP by DHPG. We conclude that mGluR priming of LTP results from biochemical cascades triggered by activation of phospholipase C coupled to group I mGluRs.
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Affiliation(s)
- A S Cohen
- Department of Psychology and the Neuroscience Research Centre, University of Otago, Dunedin, New Zealand
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35
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Tompa P, Friedrich P. Synaptic metaplasticity and the local charge effect in postsynaptic densities. Trends Neurosci 1998; 21:97-102. [PMID: 9530914 DOI: 10.1016/s0166-2236(97)01176-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Synaptic plasticity might be one of the elementary processes that underlies higher brain functions, such as learning and memory. Intriguingly, the capacity of a synapse for plastic changes itself displays marked variation or plasticity. This higher-order plasticity, or metaplasticity, appears to depend on the same macromolecules as plasticity, most notably the NMDA receptor and Ca2+/calmodulin kinase II; yet we do not understand metaplasticity in molecular terms. Metaplasticity has a feedback-inhibition character that confers stability to synaptic patterns, whereas in plasticity, the molecular events implicated tend to have an opposite effect. As a resolution to this difference, we suggest that metaplasticity be considered in a biophysical context. It has been shown that autophosphorylation of Ca2+/calmodulin kinase II in postsynaptic densities generates changes in the local electrostatic potential sufficient to affect the direction of synaptic plasticity. We propose that this finding could help explain both the puzzling abundance of Ca2+/calmodulin kinase II in the postsynaptic density and the metaplasticity of synaptic transmission.
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Affiliation(s)
- P Tompa
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Budapest
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36
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Abstract
Previous studies have demonstrated that prior synaptic activity can influence the subsequent induction of synaptic plasticity in the brain. Such temporal modulation of synaptic plasticity has been called "metaplasticity." In this report, we describe the facilitatory effects of high-frequency stimulation on the induction of homosynaptic long-term depression (LTD) in the CA1 region of the rat hippocampus. The LTD induced by low-frequency stimulation (1 Hz) protocols was found to be homosynaptic and NMDA receptor-dependent. The facilitatory effects of the high-frequency stimulation-induced priming event itself were found to be NMDA receptor-independent and to have a duration of at least 90 min. The effects of priming also were heterosynaptic, because the induction of synaptic plasticity by low-frequency stimulation was enhanced at an unprimed synaptic pathway after the priming of an independent pathway. In addition to enhancing LTD, priming also enhanced the reversal of long-term potentiation elicited by a 5 Hz depotentiation protocol. Our results provide examples of how metaplasticity may play a key role in the ongoing modulation of the induction and stabilization of alterations in synaptic strength.
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37
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Holland LL, Wagner JJ. Primed facilitation of homosynaptic long-term depression and depotentiation in rat hippocampus. J Neurosci 1998; 18:887-94. [PMID: 9437010 PMCID: PMC6792762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Previous studies have demonstrated that prior synaptic activity can influence the subsequent induction of synaptic plasticity in the brain. Such temporal modulation of synaptic plasticity has been called "metaplasticity." In this report, we describe the facilitatory effects of high-frequency stimulation on the induction of homosynaptic long-term depression (LTD) in the CA1 region of the rat hippocampus. The LTD induced by low-frequency stimulation (1 Hz) protocols was found to be homosynaptic and NMDA receptor-dependent. The facilitatory effects of the high-frequency stimulation-induced priming event itself were found to be NMDA receptor-independent and to have a duration of at least 90 min. The effects of priming also were heterosynaptic, because the induction of synaptic plasticity by low-frequency stimulation was enhanced at an unprimed synaptic pathway after the priming of an independent pathway. In addition to enhancing LTD, priming also enhanced the reversal of long-term potentiation elicited by a 5 Hz depotentiation protocol. Our results provide examples of how metaplasticity may play a key role in the ongoing modulation of the induction and stabilization of alterations in synaptic strength.
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Affiliation(s)
- L L Holland
- Department of Pharmaceutical Sciences, College of Pharmacy, North Dakota State University, Fargo, North Dakota 58105, USA
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Zhang Z, Guth L, Steward O. Mechanisms of motor recovery after subtotal spinal cord injury: insights from the study of mice carrying a mutation (WldS) that delays cellular responses to injury. Exp Neurol 1998; 149:221-9. [PMID: 9454631 DOI: 10.1006/exnr.1997.6717] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
UNLABELLED Partial lesions of the mammalian spinal cord result in an immediate motor impairment that recovers gradually over time; however, the cellular mechanisms responsible for the transient nature of this paralysis have not been defined. A unique opportunity to identify those injury-induced cellular responses that mediate the recovery of function has arisen from the discovery of a unique mutant strain of mice in which the onset of Wallerian degeneration is dramatically delayed. In this strain of mice (designated WldS for Wallerian degeneration, slow), many of the cellular responses to spinal cord injury are also delayed. We have used this experimental animal model to evaluate possible causal relationships between these delayed cellular responses and the onset of functional recovery. For this purpose, we have compared the time course of locomotor recovery in C57BL/6 (control) mice and in WldS (mutant) mice by hemisecting the spinal cord at T8 and evaluating locomotor function at daily postoperative intervals. The time course of locomotor recovery (as determined by the Tarlov open-field walking procedure) was substantially delayed in mice carrying the WldS mutation: C57BL/6 control mice began to stand and walk within 6 days (mean Tarlov score of 4), whereas mutant mice did not exhibit comparable locomotor function until 16 days postoperatively. INTERPRETATION AND CONCLUSION (a) The rapid return of locomotor function in the C57BL/6 mice suggests that the recovery resulted from processes of functional plasticity rather than from regeneration or collateral sprouting of nerve fibers. (b) The marked delay in the return of locomotor function in WldS mice indicates that the processes of neuroplasticity are induced by degenerative changes in the damaged neurons. (c) These strains of mice can be effectively used in future studies to elucidate the specific biochemical and physiological alterations responsible for inducing functional plasticity and restoring locomotor function after spinal cord injury.
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Affiliation(s)
- Z Zhang
- Department of Neuroscience and Neurosurgery, University of Virginia Health Sciences Center, Charlottesville 22908, USA
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Tokuda M, Hatase O. Regulation of neuronal plasticity in the central nervous system by phosphorylation and dephosphorylation. Mol Neurobiol 1998; 17:137-56. [PMID: 9887450 DOI: 10.1007/bf02802028] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Neuronal plasticity can be defined as adaptive changes in structure and function of the nervous system, an obvious example of which is the capacity to remember and learn. Long-term potentiation and long-term depression are the experimental models of memory in the central nervous system (CNS), and have been frequently utilized for the analysis of the molecular mechanisms of memory formation. Extensive studies have demonstrated that various kinases and phosphatases regulate neuronal plasticity by phosphorylating and dephosphorylating proteins essential to the basic processes of adaptive changes in the CNS. These proteins include receptors, ion channels, synaptic vesicle proteins, and nuclear proteins. Multifunctional kinases (cAMP-dependent protein kinase, Ca2+/phospholipid-dependent protein kinase, and Ca2+/calmodulin-dependent protein kinases) and phosphatases (calcineurin, protein phosphatases 1, and 2A) that specifically modulate the phosphorylation status of neuronal-signaling proteins have been shown to be required for neuronal plasticity. In general, kinases are involved in upregulation of the activity of target substrates, and phosphatases downregulate them. Although this rule is applicable in most of the cases studied, there are also a number of exceptions. A variety of regulation mechanisms via phosphorylation and dephosphorylation mediated by multiple kinases and phosphatases are discussed.
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Affiliation(s)
- M Tokuda
- Department of Physiology, Kagawa Medical University, Japan
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40
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Phosphorylation of the synaptic protein interaction site on N-type calcium channels inhibits interactions with SNARE proteins. J Neurosci 1997. [PMID: 9278528 DOI: 10.1523/jneurosci.17-18-06929.1997] [Citation(s) in RCA: 97] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The synaptic protein interaction (synprint) site on the N-type calcium channel alpha1B subunit binds to the soluble N-ethylmaleimide-sensitive attachment factor receptor (SNARE) proteins syntaxin and synaptosomal protein of 25 kDa (SNAP-25), and this association may be required for efficient fast synaptic transmission. Protein kinase C (PKC) and calcium and calmodulin-dependent protein kinase type II (CaM KII) phosphorylated a recombinant his-tagged synprint site polypeptide rapidly to a stoichiometry of 3-4 mol of phosphate/mol, whereas cAMP-dependent protein kinase (PKA) and cGMP-dependent protein kinase (PKG) phosphorylated the synprint peptide more slowly to a stoichiometry of <1 mol/mol. Two-dimensional phosphopeptide mapping revealed similar patterns of phosphorylation of synprint polypeptides and native rat brain N-type calcium channel alpha1B subunits by PKC and Cam KII. Phosphorylation of the synprint peptide with PKC or CaM KII, but not PKA or PKG, strongly inhibited binding of recombinant syntaxin or SNAP-25, even at a level of free calcium (15 microM) that stimulates maximal binding. In contrast, phosphorylation of syntaxin and SNAP-25 with PKC and CaM KII did not affect interactions with the synprint site. Binding assays with polypeptides representing the N- and C-terminal halves of the synprint site indicate that the PKC- and CaM KII-mediated inhibition of binding involves multiple, disperse phosphorylation sites. PKC or CaM KII phosphorylation of the synprint peptide also inhibited its interactions with native rat brain SNARE complexes containing syntaxin and SNAP-25. These results suggest that phosphorylation of the synprint site by PKC or CaM KII may serve as a biochemical switch for interactions between N-type calcium channels and SNARE protein complexes.
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41
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Yokoyama CT, Sheng ZH, Catterall WA. Phosphorylation of the synaptic protein interaction site on N-type calcium channels inhibits interactions with SNARE proteins. J Neurosci 1997; 17:6929-38. [PMID: 9278528 PMCID: PMC6573282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The synaptic protein interaction (synprint) site on the N-type calcium channel alpha1B subunit binds to the soluble N-ethylmaleimide-sensitive attachment factor receptor (SNARE) proteins syntaxin and synaptosomal protein of 25 kDa (SNAP-25), and this association may be required for efficient fast synaptic transmission. Protein kinase C (PKC) and calcium and calmodulin-dependent protein kinase type II (CaM KII) phosphorylated a recombinant his-tagged synprint site polypeptide rapidly to a stoichiometry of 3-4 mol of phosphate/mol, whereas cAMP-dependent protein kinase (PKA) and cGMP-dependent protein kinase (PKG) phosphorylated the synprint peptide more slowly to a stoichiometry of <1 mol/mol. Two-dimensional phosphopeptide mapping revealed similar patterns of phosphorylation of synprint polypeptides and native rat brain N-type calcium channel alpha1B subunits by PKC and Cam KII. Phosphorylation of the synprint peptide with PKC or CaM KII, but not PKA or PKG, strongly inhibited binding of recombinant syntaxin or SNAP-25, even at a level of free calcium (15 microM) that stimulates maximal binding. In contrast, phosphorylation of syntaxin and SNAP-25 with PKC and CaM KII did not affect interactions with the synprint site. Binding assays with polypeptides representing the N- and C-terminal halves of the synprint site indicate that the PKC- and CaM KII-mediated inhibition of binding involves multiple, disperse phosphorylation sites. PKC or CaM KII phosphorylation of the synprint peptide also inhibited its interactions with native rat brain SNARE complexes containing syntaxin and SNAP-25. These results suggest that phosphorylation of the synprint site by PKC or CaM KII may serve as a biochemical switch for interactions between N-type calcium channels and SNARE protein complexes.
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Affiliation(s)
- C T Yokoyama
- Graduate Program in Neurobiology and Behavior, University of Washington, Seattle, Washington 98195, USA
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42
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Group 1 and 2 metabotropic glutamate receptors play differential roles in hippocampal long-term depression and long-term potentiation in freely moving rats. J Neurosci 1997. [PMID: 9096163 DOI: 10.1523/jneurosci.17-09-03303.1997] [Citation(s) in RCA: 178] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
This study examined the role of metabotropic glutamate receptors (mGluRs) in hippocampal long-term depression (LTD) in vivo. The group 1 mGluR antagonist (S)4-carboxyphenylglycine (4CPG), group 1/2 antagonist (RS)-alpha-methyl-4-carboxyphenylglycine (MCPG), and group 2 antagonists (RS)-alpha-methylserine-O-phos-phate monophenyl ester (MSOPPE) and (2S)-alpha-ethylglutamic acid (EGLU) were used. The NMDA receptor antagonist D(-)-2-amino-5-phosphonopentanoic acid (AP5) was used to examine the NMDA receptor contribution to the observed LTD. Adult male Wistar rats underwent implantation of stimulating and recording electrodes into the Schaffer collaterals and CA1 stratum radiatum, respectively. After recovery of 5-7 d, the field EPSP was measured from freely moving animals. Drugs were applied either before or after 1 Hz low-frequency train (LFT) or 100 Hz stimulation via a cannula implanted in the lateral cerebral ventricle. Nine hundred pulses at 1 Hz produced an LTD that was marked and long-lasting. This LTD was completely inhibited by pre-LFT application of AP5. MCPG inhibited LTD from 2 hr post-LFT. 4CPG partially impaired LTD. MSOPPE and EGLU completely blocked induction of LTD, although short-term depression remained intact. MSOPPE did not block long-term potentiation (LTP) induced by 100 Hz stimulation, whereas 4CPG produced a significant inhibition. When MSOPPE was present, LTD could not be induced either before or after LTP induction, whereas LTD could be induced in an identical protocol in vehicle-injected animals. These results suggest a differential role for mGluRs in NMDA receptor-dependent hippocampal LTD in vivo. Group 1 mGluRs may play a role in both LTD and LTP, whereas group 2 mGluRs may be critically involved only in LTD induction.
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43
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Manahan-Vaughan D. Group 1 and 2 metabotropic glutamate receptors play differential roles in hippocampal long-term depression and long-term potentiation in freely moving rats. J Neurosci 1997; 17:3303-11. [PMID: 9096163 PMCID: PMC6573649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/1996] [Revised: 02/07/1997] [Accepted: 02/13/1997] [Indexed: 02/04/2023] Open
Abstract
This study examined the role of metabotropic glutamate receptors (mGluRs) in hippocampal long-term depression (LTD) in vivo. The group 1 mGluR antagonist (S)4-carboxyphenylglycine (4CPG), group 1/2 antagonist (RS)-alpha-methyl-4-carboxyphenylglycine (MCPG), and group 2 antagonists (RS)-alpha-methylserine-O-phos-phate monophenyl ester (MSOPPE) and (2S)-alpha-ethylglutamic acid (EGLU) were used. The NMDA receptor antagonist D(-)-2-amino-5-phosphonopentanoic acid (AP5) was used to examine the NMDA receptor contribution to the observed LTD. Adult male Wistar rats underwent implantation of stimulating and recording electrodes into the Schaffer collaterals and CA1 stratum radiatum, respectively. After recovery of 5-7 d, the field EPSP was measured from freely moving animals. Drugs were applied either before or after 1 Hz low-frequency train (LFT) or 100 Hz stimulation via a cannula implanted in the lateral cerebral ventricle. Nine hundred pulses at 1 Hz produced an LTD that was marked and long-lasting. This LTD was completely inhibited by pre-LFT application of AP5. MCPG inhibited LTD from 2 hr post-LFT. 4CPG partially impaired LTD. MSOPPE and EGLU completely blocked induction of LTD, although short-term depression remained intact. MSOPPE did not block long-term potentiation (LTP) induced by 100 Hz stimulation, whereas 4CPG produced a significant inhibition. When MSOPPE was present, LTD could not be induced either before or after LTP induction, whereas LTD could be induced in an identical protocol in vehicle-injected animals. These results suggest a differential role for mGluRs in NMDA receptor-dependent hippocampal LTD in vivo. Group 1 mGluRs may play a role in both LTD and LTP, whereas group 2 mGluRs may be critically involved only in LTD induction.
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Affiliation(s)
- D Manahan-Vaughan
- Federal Institute for Neurobiology, Department of Neurophysiology, D-39008 Magdeburg, Germany
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44
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Induction of hippocampal long-term depression requires release of Ca2+ from separate presynaptic and postsynaptic intracellular stores. J Neurosci 1996. [PMID: 8815877 DOI: 10.1523/jneurosci.16-19-05951.1996] [Citation(s) in RCA: 147] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Studies have suggested that an increase in intracellular [Ca2+] is necessary for the induction of both long-term potentiation (LTP) and long-term depression (LTD) of synaptic transmission, and that release of Ca2+ from intracellular storage pools can be necessary to induce LTP. We investigated whether release of Ca2+ from intracellular stores also is required for the induction of LTD at Schaffer collateral-CA1 synapses in hippocampal slices. Both thapsigargin (1 microM) and cyclopiazonic acid (1 microM), compounds that deplete all intracellular Ca2+ pools by blocking LTP-dependent Ca2+ uptake into intracellular compartments, blocked the induction, but not maintenance, of LTD by low-frequency stimulation (LFS) (1 Hz/15 min) without affecting baseline synaptic transmission. Washout of the reversible inhibitor cyclopiazonic acid restored the ability to induce LTD. In contrast, thapsigargin did not block depotentiation of LTP by 1 Hz LFS, suggesting that LTP causes a reduction in the threshold [Ca2+] necessary for LTD. Selective depletion of the ryanodine receptor-gated Ca2+ pool by bath application of ryanodine (10 microM) also blocked the induction of LTD, indicating a requirement for Ca(2+)-induced Ca2+ release. Impalement of CA1 pyramidal neurons with microelectrodes containing thapsigargin (500 nM to 200 microM) prevented the induction of LTD at synapses on that neuron without blocking LTD in the rest of the slice. In contrast, similar filling of CA1 pyramidal neurons with ryanodine (2 microM to 5 mM) did not block the induction of LTD. From these data, we conclude that the induction of LTD requires release of Ca2+ both from a presynaptic ryanodine-sensitive pool and from postsynaptic (presumably IP3-gated) stores.
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45
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Reyes M, Stanton PK. Induction of hippocampal long-term depression requires release of Ca2+ from separate presynaptic and postsynaptic intracellular stores. J Neurosci 1996; 16:5951-60. [PMID: 8815877 PMCID: PMC6579182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Studies have suggested that an increase in intracellular [Ca2+] is necessary for the induction of both long-term potentiation (LTP) and long-term depression (LTD) of synaptic transmission, and that release of Ca2+ from intracellular storage pools can be necessary to induce LTP. We investigated whether release of Ca2+ from intracellular stores also is required for the induction of LTD at Schaffer collateral-CA1 synapses in hippocampal slices. Both thapsigargin (1 microM) and cyclopiazonic acid (1 microM), compounds that deplete all intracellular Ca2+ pools by blocking LTP-dependent Ca2+ uptake into intracellular compartments, blocked the induction, but not maintenance, of LTD by low-frequency stimulation (LFS) (1 Hz/15 min) without affecting baseline synaptic transmission. Washout of the reversible inhibitor cyclopiazonic acid restored the ability to induce LTD. In contrast, thapsigargin did not block depotentiation of LTP by 1 Hz LFS, suggesting that LTP causes a reduction in the threshold [Ca2+] necessary for LTD. Selective depletion of the ryanodine receptor-gated Ca2+ pool by bath application of ryanodine (10 microM) also blocked the induction of LTD, indicating a requirement for Ca(2+)-induced Ca2+ release. Impalement of CA1 pyramidal neurons with microelectrodes containing thapsigargin (500 nM to 200 microM) prevented the induction of LTD at synapses on that neuron without blocking LTD in the rest of the slice. In contrast, similar filling of CA1 pyramidal neurons with ryanodine (2 microM to 5 mM) did not block the induction of LTD. From these data, we conclude that the induction of LTD requires release of Ca2+ both from a presynaptic ryanodine-sensitive pool and from postsynaptic (presumably IP3-gated) stores.
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Affiliation(s)
- M Reyes
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461-1602, USA
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46
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Abstract
LTD of synaptic transmission is a form of long-term synaptic plasticity with the potential to be as significant as LTP to both the activity-dependent development of neural circuitry and adult memory storage. In addition, interactions between LTP and LTD and the dynamic regulation of the gain of synaptic plasticity mechanisms are also very important. In particular, the computational ability of LTD to properly counterbalance LTP may be essential to maintaining synaptic strengths in the linear range, and to maximally sharpen the ability of synapses to compute and store frequency-based information about the phase relation between synapses. Experimental data confirm the presence of an activity-dependent "sliding threshold" with the expected properties. That is, when levels of neuronal activity are high, indicating circumstances increasing the likelihood of inducing LTP, compensatory changes cause the suppression of LTP and an enhanced likelihood of LTD. Conversely, we would predict that low levels of synaptic activity would shift the threshold in favor of greater LTP and less LTD, a hypothesis which has yet to be tested. The sliding threshold for LTP and LTD also has implications for underlying cellular mechanisms of both forms of long-term synaptic plasticity. If the thresholds for LTP and LTD are tightly and reciprocally co-regulated, that could imply that at least one component of LTD is a true depotentiation caused by reversal of a change mediating LTP. If so, the intuitively simplest hypothesis is that phosphorylation of AMPA glutamate receptors causes LTP of synaptic e.p.s.p.s, while dephosphorylation of the same site or sites causes depotentiation LTD. Of course, this hypothesis would refer only to a postsynaptic component of both LTP and LTD. There has been a recent report that, in neonatal rat hippocampus, a form of LTD that is expressed developmentally earlier than LTP appears to have a postsynaptic induction site, but is expressed as decreased presynaptic transmitter release (Bolshakov and Siegelbaum, 1994). Whether these properties will be retained as LTD matures is unknown, as is the likelihood that, if a component of LTP is expressed presynaptically, depotentiation of that presynaptic component can also occur. Equally unclear is the persistence of LTD relative to LTP. The few rigorous long-term anatomical studies available suggest that the latest phases of LTP may be expressed as changes in dendritic spine shapes and/or synaptic morphology. While heterosynaptic LTD has been reported to have a duration of weeks in vivo (Abraham et al., 1994), we do not know whether LTP-induced morphological changes that take many days to appear can be reversed in an activity-dependent manner. An important feature of the consolidation of memories may turn out to be the slow development of LTP that is resistant to reversal by LTD. While we still at an earlier stage in our understanding of the mechanisms underlying LTD compared to LTP, some things are becoming clear. LTD is induced by afferent neuronal activity that is relatively ineffective in exciting the postsynaptic cell--an "anti-hebbian" condition. This property, coupled with the hebbian properties of LTP and the dynamic nature of membrane conductances, necessarily confers upon synapses the ability to compute and store the results of a covariance function. However, the role of such a computation in processing and/or memory is unclear. In addition, LTD appears to require the activation of NMDA and metabotropic subtypes of glutamate receptors, release of Ca2+ from intracellular stores, and an increase in intracellular [Ca2+] that is lower than that necessary to induce LTP. The early evidence is consistent with some overlap of targets for modification by LTP and LTD, with some forms of LTD likely to be a reversal, or "depotentiation," of previous LTP, perhaps through dephosphorylation of AMPA receptors.
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Affiliation(s)
- P K Stanton
- Albert Einstein College of Medicine, Bronx, New York 10461-1602, USA
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Deisseroth K, Bito H, Schulman H, Tsien RW. Synaptic plasticity: A molecular mechanism for metaplasticity. Curr Biol 1995; 5:1334-8. [PMID: 8749377 DOI: 10.1016/s0960-9822(95)00262-4] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- K Deisseroth
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, California 94305, USA
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