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Koek LA, Sanderson TM, Georgiou J, Collingridge GL. The role of calcium stores in long-term potentiation and synaptic tagging and capture in mouse hippocampus. Philos Trans R Soc Lond B Biol Sci 2024; 379:20230241. [PMID: 38853556 PMCID: PMC11343308 DOI: 10.1098/rstb.2023.0241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 03/25/2024] [Accepted: 04/08/2024] [Indexed: 06/11/2024] Open
Abstract
The roles of Ca2+-induced calcium release in synaptic plasticity and metaplasticity are poorly understood. The present study has addressed the role of intracellular Ca2+ stores in long-term potentiation (LTP) and a form of heterosynaptic metaplasticity known as synaptic tagging and capture (STC) at CA1 synapses in mouse hippocampal slices. The effects of two compounds, ryanodine and cyclopiazonic acid (CPA), were examined on LTP induced by three distinct induction protocols: weak (w), compressed (c) and spaced (s) theta-burst stimulation (TBS). These compounds did not significantly affect LTP induced by the wTBS (one episode of TBS; 25 stimuli) or cTBS (three such episodes with a 10 s inter-episode interval (IEI); 75 stimuli) but substantially inhibited LTP induced by a sTBS (10 min IEI; 75 stimuli). Ryanodine and CPA also prevented a small heterosynaptic potentiation that was observed with the sTBS protocol. Interestingly, these compounds also prevented STC when present during either the sTBS or the subsequent wTBS, applied to an independent input. All of these effects of ryanodine and CPA were similar to that of a calcium-permeable AMPA receptor blocker. In conclusion, Ca2+ stores provide one way in which signals are propagated between synaptic inputs and, by virtue of their role in STC, may be involved in associative long-term memories. This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'.
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Affiliation(s)
- Laura A. Koek
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Sinai Health System, Toronto, OntarioM5G 1X5, Canada
- Department of Physiology, University of Toronto, Toronto, OntarioM5S 1A8, Canada
| | - Thomas M. Sanderson
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Sinai Health System, Toronto, OntarioM5G 1X5, Canada
| | - John Georgiou
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Sinai Health System, Toronto, OntarioM5G 1X5, Canada
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, OntarioM5S 1A8, Canada
| | - Graham L. Collingridge
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Sinai Health System, Toronto, OntarioM5G 1X5, Canada
- Department of Physiology, University of Toronto, Toronto, OntarioM5S 1A8, Canada
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, OntarioM5S 1A8, Canada
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2
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Al-Amri AH, Armstrong P, Amici M, Ligneul C, Rouse J, El-Asrag ME, Pantiru A, Vancollie VE, Ng HW, Ogbeta JA, Goodchild K, Ellegood J, Lelliott CJ, Mullins JG, Bretman A, Al-Ali R, Beetz C, Al-Gazali L, Al Shamsi A, Lerch JP, Mellor JR, Al Sayegh A, Ali M, Inglehearn CF, Clapcote SJ. PDZD8 Disruption Causes Cognitive Impairment in Humans, Mice, and Fruit Flies. Biol Psychiatry 2022; 92:323-334. [PMID: 35227461 PMCID: PMC9302898 DOI: 10.1016/j.biopsych.2021.12.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 12/13/2021] [Accepted: 12/14/2021] [Indexed: 12/16/2022]
Abstract
BACKGROUND The discovery of coding variants in genes that confer risk of intellectual disability (ID) is an important step toward understanding the pathophysiology of this common developmental disability. METHODS Homozygosity mapping, whole-exome sequencing, and cosegregation analyses were used to identify gene variants responsible for syndromic ID with autistic features in two independent consanguineous families from the Arabian Peninsula. For in vivo functional studies of the implicated gene's function in cognition, Drosophila melanogaster and mice with targeted interference of the orthologous gene were used. Behavioral, electrophysiological, and structural magnetic resonance imaging analyses were conducted for phenotypic testing. RESULTS Homozygous premature termination codons in PDZD8, encoding an endoplasmic reticulum-anchored lipid transfer protein, showed cosegregation with syndromic ID in both families. Drosophila melanogaster with knockdown of the PDZD8 ortholog exhibited impaired long-term courtship-based memory. Mice homozygous for a premature termination codon in Pdzd8 exhibited brain structural, hippocampal spatial memory, and synaptic plasticity deficits. CONCLUSIONS These data demonstrate the involvement of homozygous loss-of-function mutations in PDZD8 in a neurodevelopmental cognitive disorder. Model organisms with manipulation of the orthologous gene replicate aspects of the human phenotype and suggest plausible pathophysiological mechanisms centered on disrupted brain development and synaptic function. These findings are thus consistent with accruing evidence that synaptic defects are a common denominator of ID and other neurodevelopmental conditions.
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Affiliation(s)
- Ahmed H. Al-Amri
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom,Leeds Institute of Medical Research, University of Leeds, Leeds, United Kingdom,National Genetic Centre, Royal Hospital, Muscat, Oman
| | - Paul Armstrong
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Mascia Amici
- School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol, United Kingdom
| | - Clemence Ligneul
- Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neuroscience, University of Oxford, Oxford, United Kingdom
| | - James Rouse
- School of Biology, University of Leeds, Leeds, United Kingdom
| | - Mohammed E. El-Asrag
- Leeds Institute of Medical Research, University of Leeds, Leeds, United Kingdom,Department of Zoology, Faculty of Science, Benha University, Benha, Egypt,Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham
| | - Andreea Pantiru
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | | | - Hannah W.Y. Ng
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Jennifer A. Ogbeta
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Kirstie Goodchild
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Jacob Ellegood
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, Ontario, Canada
| | | | | | - Amanda Bretman
- School of Biology, University of Leeds, Leeds, United Kingdom
| | | | | | - Lihadh Al-Gazali
- Department of Paediatrics, College of Medicine & Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Aisha Al Shamsi
- Pediatrics Department, Tawam Hospital, Al Ain, United Arab Emirates
| | - Jason P. Lerch
- Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neuroscience, University of Oxford, Oxford, United Kingdom
| | - Jack R. Mellor
- School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol, United Kingdom
| | - Abeer Al Sayegh
- Genetics Department, Sultan Qaboos University Hospital, Muscat, Oman
| | - Manir Ali
- Leeds Institute of Medical Research, University of Leeds, Leeds, United Kingdom
| | - Chris F. Inglehearn
- Leeds Institute of Medical Research, University of Leeds, Leeds, United Kingdom
| | - Steven J. Clapcote
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom,Address correspondence to Steven J. Clapcote, Ph.D.
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3
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Luessen DJ, Conn PJ. Allosteric Modulators of Metabotropic Glutamate Receptors as Novel Therapeutics for Neuropsychiatric Disease. Pharmacol Rev 2022; 74:630-661. [PMID: 35710132 PMCID: PMC9553119 DOI: 10.1124/pharmrev.121.000540] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Metabotropic glutamate (mGlu) receptors, a family of G-protein-coupled receptors, have been identified as novel therapeutic targets based on extensive research supporting their diverse contributions to cell signaling and physiology throughout the nervous system and important roles in regulating complex behaviors, such as cognition, reward, and movement. Thus, targeting mGlu receptors may be a promising strategy for the treatment of several brain disorders. Ongoing advances in the discovery of subtype-selective allosteric modulators for mGlu receptors has provided an unprecedented opportunity for highly specific modulation of signaling by individual mGlu receptor subtypes in the brain by targeting sites distinct from orthosteric or endogenous ligand binding sites on mGlu receptors. These pharmacological agents provide the unparalleled opportunity to selectively regulate neuronal excitability, synaptic transmission, and subsequent behavioral output pertinent to many brain disorders. Here, we review preclinical and clinical evidence supporting the utility of mGlu receptor allosteric modulators as novel therapeutic approaches to treat neuropsychiatric diseases, such as schizophrenia, substance use disorders, and stress-related disorders.
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4
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Jones OD. Do group I metabotropic glutamate receptors mediate LTD? Neurobiol Learn Mem 2016; 138:85-97. [PMID: 27545442 DOI: 10.1016/j.nlm.2016.08.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Revised: 08/01/2016] [Accepted: 08/17/2016] [Indexed: 01/31/2023]
Abstract
Synapses undergo significant structural and functional reorganization in response to varying patterns of stimulation. These forms of plasticity are considered fundamental to cognition and neuronal homeostasis. An increasing number of reports highlight the importance of activity-dependent synaptic strengthening (long term potentiation: LTP) for learning. However, the functional significance of activity-dependent weakening of synapses (long term depression: LTD) remains relatively poorly understood. One form of synaptic weakening, induced by group I metabotropic glutamate receptors (mGluRs), has received significant attention from a mechanistic point of view and because of its augmentation in a murine model of Fragile X Syndrome. Yet, studies of this form of plasticity often yield confusing, contradictory results. These conflicting findings are likely attributable to the bulk stimulation and recording techniques often used to study synaptic plasticity (typically involving evoked extracellular recordings, which represent the summed activity of many synapses). Such studies inherently blur the identity of the synapses undergoing change, thus giving the illusion that synapses per se are being modified when in fact this may only be true of a specific subset of synapses. Indeed, studies employing minimal synaptic activation paint a fundamentally different picture of what is commonly called "mGluR-LTD". Here, I review the evidence in favour of group I mGluRs as mediators of various forms of synaptic downregulation and attempt to explain discrepancies in the literature. I argue that, while multiple forms of synaptic weakening may be triggered by these receptors, the canonical form of group I mGluR-mediated depression, mGluR-LTD, is in fact not a depression of basal synaptic responses. Rather, it is a reversal of established LTP and thus a form of depotentiation. Far from being arbitrary, this distinction has significant implications for the role of group I mGluRs in cognition, both in the healthy brain and in pathological conditions. Further, the differential actions of group I mGluRs at naïve and potentiated synapses suggest these receptors signal in a state-dependent manner to regulate various stages of the learning process.
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Affiliation(s)
- Owen D Jones
- Department of Psychology, Brain Health Research Centre & Brain Research New Zealand, University of Otago, Dunedin, New Zealand.
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5
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Alford ST, Alpert MH. A synaptic mechanism for network synchrony. Front Cell Neurosci 2014; 8:290. [PMID: 25278839 PMCID: PMC4166887 DOI: 10.3389/fncel.2014.00290] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 08/31/2014] [Indexed: 01/06/2023] Open
Abstract
Within neural networks, synchronization of activity is dependent upon the synaptic connectivity of embedded microcircuits and the intrinsic membrane properties of their constituent neurons. Synaptic integration, dendritic Ca2+ signaling, and non-linear interactions are crucial cellular attributes that dictate single neuron computation, but their roles promoting synchrony and the generation of network oscillations are not well understood, especially within the context of a defined behavior. In this regard, the lamprey spinal central pattern generator (CPG) stands out as a well-characterized, conserved vertebrate model of a neural network (Smith et al., 2013a), which produces synchronized oscillations in which neural elements from the systems to cellular level that control rhythmic locomotion have been determined. We review the current evidence for the synaptic basis of oscillation generation with a particular emphasis on the linkage between synaptic communication and its cellular coupling to membrane processes that control oscillatory behavior of neurons within the locomotor network. We seek to relate dendritic function found in many vertebrate systems to the accessible lamprey central nervous system in which the relationship between neural network activity and behavior is well understood. This enables us to address how Ca2+ signaling in spinal neuron dendrites orchestrate oscillations that drive network behavior.
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Affiliation(s)
- Simon T Alford
- Department of Biological Sciences, University of Illinois at Chicago Chicago, IL, USA
| | - Michael H Alpert
- Department of Biological Sciences, University of Illinois at Chicago Chicago, IL, USA
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6
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Benhassine N, Berger T. Large-conductance calcium-dependent potassium channels prevent dendritic excitability in neocortical pyramidal neurons. Pflugers Arch 2008; 457:1133-45. [PMID: 18762971 DOI: 10.1007/s00424-008-0569-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2008] [Revised: 06/25/2008] [Accepted: 07/29/2008] [Indexed: 10/21/2022]
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7
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Tokuda K, Zorumski CF, Izumi Y. Modulation of hippocampal long-term potentiation by slow increases in ethanol concentration. Neuroscience 2007; 146:340-9. [PMID: 17346891 PMCID: PMC1934937 DOI: 10.1016/j.neuroscience.2007.01.037] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2006] [Revised: 01/03/2007] [Accepted: 01/12/2007] [Indexed: 10/23/2022]
Abstract
To determine how acute ethanol intoxication may alter memory processing, we examined the effects of stepwise increases in ethanol on long-term potentiation (LTP) in rat hippocampal slices. LTP was inhibited by acute administration of 60 mM ethanol, but was readily induced if ethanol was increased gradually to 60 mM over 75 min. Administration of 2-amino-5 phosphonovalerate (APV), an N-methyl-D-aspartate receptor (NMDAR) antagonist, during the stepwise increase in ethanol inhibited LTP, suggesting involvement of NMDARs in the development of tolerance. However, APV and nifedipine, an inhibitor of L-type calcium channels, failed to inhibit LTP when administered following the slow increase in ethanol. Ethanol-tolerant LTP was inhibited by thapsigargin, suggesting a major role for intracellular calcium release in this form of plasticity. The unique properties of ethanol-tolerant LTP suggest that memories formed during binge drinking are not acquired by standard synaptic mechanisms and that acute tolerance may involve the induction of novel mechanisms to maintain function.
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Affiliation(s)
- K Tokuda
- Department of Psychiatry, Washington University School of Medicine, 660 South Euclid, Box 8134, St. Louis, MO 63110, USA
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8
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Ferraguti F, Shigemoto R. Metabotropic glutamate receptors. Cell Tissue Res 2006; 326:483-504. [PMID: 16847639 DOI: 10.1007/s00441-006-0266-5] [Citation(s) in RCA: 388] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2006] [Accepted: 05/31/2006] [Indexed: 12/22/2022]
Abstract
Metabotropic glutamate receptors (mGlus) are a family of G-protein-coupled receptors activated by the neurotransmitter glutamate. Molecular cloning has revealed eight different subtypes (mGlu1-8) with distinct molecular and pharmacological properties. Multiplicity in this receptor family is further generated through alternative splicing. mGlus activate a multitude of signalling pathways important for modulating neuronal excitability, synaptic plasticity and feedback regulation of neurotransmitter release. In this review, we summarize anatomical findings (from our work and that of other laboratories) describing their distribution in the central nervous system. Recent evidence regarding the localization of these receptors in peripheral tissues will also be examined. The distinct regional, cellular and subcellular distribution of mGlus in the brain will be discussed in view of their relationship to neurotransmitter release sites and of possible functional implications.
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Affiliation(s)
- Francesco Ferraguti
- Department of Pharmacology, Innsbruck Medical University, Peter Mayr Strasse 1a, A-6020, Innsbruck, Austria
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9
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Verkhratsky A. Physiology and Pathophysiology of the Calcium Store in the Endoplasmic Reticulum of Neurons. Physiol Rev 2005; 85:201-79. [PMID: 15618481 DOI: 10.1152/physrev.00004.2004] [Citation(s) in RCA: 560] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The endoplasmic reticulum (ER) is the largest single intracellular organelle, which is present in all types of nerve cells. The ER is an interconnected, internally continuous system of tubules and cisterns, which extends from the nuclear envelope to axons and presynaptic terminals, as well as to dendrites and dendritic spines. Ca2+release channels and Ca2+pumps residing in the ER membrane provide for its excitability. Regulated ER Ca2+release controls many neuronal functions, from plasmalemmal excitability to synaptic plasticity. Enzymatic cascades dependent on the Ca2+concentration in the ER lumen integrate rapid Ca2+signaling with long-lasting adaptive responses through modifications in protein synthesis and processing. Disruptions of ER Ca2+homeostasis are critically involved in various forms of neuropathology.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester, Faculty of Biological Sciences, United Kingdom.
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10
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Rae MG, Irving AJ. Both mGluR1 and mGluR5 mediate Ca2+ release and inward currents in hippocampal CA1 pyramidal neurons. Neuropharmacology 2004; 46:1057-1069. [PMID: 15111012 DOI: 10.1016/j.neuropharm.2004.02.002] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2003] [Revised: 12/11/2003] [Accepted: 02/03/2004] [Indexed: 10/26/2022]
Abstract
Using combined whole-cell voltage-clamp recording and Ca2+ imaging we have investigated further the characteristics and pharmacology of group I metabotropic l-glutamate receptor (mGluR)-mediated responses in CA1 pyramidal neurons of the rat hippocampus. The selective group I mGluR agonist, (RS)-3,5-dihydroxyphenylglycine (DHPG), evoked a transient increase in intracellular Ca2+ levels ([Ca2+]i), within neuronal somas and apical dendrites, together with a relatively long lasting inward current (I(DHPG)). Both types of response were enhanced by depolarisation (-30 mV), and this condition was used for their characterisation. The DHPG-induced [Ca2+]i rise was much more sensitive to manipulations of Ca2+ homeostasis, such as using the Ca2+ store depleting agent, cyclopiazonic acid (50-100 microM), the fast Ca2+ buffer, BAPTA (intracellular; 20-40 mM) and Ca(2+)-free/EGTA (1 mM) bath solution, than I(DHPG), suggesting that these responses are, in the main part, mediated by distinct processes. The selective mGluR1 and mGluR5 antagonists, (S)-(+)-alpha-amino-a-methylbenzeneacetic acid (LY367385; 100 microM) and 2-methyl-6-(phenylethynyl)-pyridine (MPEP;10 microM), respectively, markedly inhibited both I(DHPG) and the DHPG-evoked increase in [Ca2+]i. Moreover, these antagonists inhibited the Ca2+ response by more than 50% suggesting a synergistic interaction between mGluR1 and mGluR5. This study demonstrates that in CA1 pyramidal neurons group I mGluR-mediated inward currents and Ca2+ release from intracellular stores are enhanced under depolarising conditions and that mGluR1 and mGluR5 both contribute to these phenomena.
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Affiliation(s)
- Mark G Rae
- Division of Pathology and Neuroscience, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, Scotland, UK.
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11
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Matias CM, Dionísio JC, Arif M, Quinta-Ferreira ME. Effect of D-2 amino-5-phosphonopentanoate and nifedipine on postsynaptic calcium changes associated with long-term potentiation in hippocampal CA1 area. Brain Res 2003; 976:90-9. [PMID: 12763626 DOI: 10.1016/s0006-8993(03)02698-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The induction of long-term potentiation (LTP) in CA1 hippocampal area requires a rise in intracellular postsynaptic calcium. Two major calcium mechanisms may mediate the transmembrane calcium influxes that contribute to this calcium accumulation: the N-methyl-D-aspartate (NMDA) receptor channels, which are voltage dependent and have large calcium permeability and voltage-dependent calcium channels (VDCCs). We have addressed the relative contribution of these routes of calcium entry before and during LTP expression, in synaptically evoked dendritic calcium transients from a population of CA1 pyramidal neurons. Combining the use of the fluorescent calcium indicator Fura-2 with field potential measurements, we observed that the calcium transients evoked by single stimuli, during the maintenance phase of LTP, were enhanced. These transients were not affected by D-2 amino-5-phosphonopentanoate (D-APV) (50 microM), an antagonist of NMDA receptors but were reduced by approximately one-quarter, in the presence of the L-type VDCCs blocker nifedipine (10 microM). During tetanic stimulation (100 Hz, 1 s) the components triggered by the activation of those two calcium mechanisms had comparable magnitudes representing the sum about half of the intracellular calcium accumulation. Thus, following both single and high frequency stimulation, a substantial fraction of calcium entry may occur through other types of VDCCs or be due to calcium release from intracellular stores.
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Affiliation(s)
- Carlos M Matias
- Department of Physics, University of Trás-os-Montes and Alto Douro (UTAD), 5001-911 Vila Real, Portugal
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12
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Matias C, Dionísio JC, Quinta-Ferreira ME. Thapsigargin blocks STP and LTP related calcium enhancements in hippocampal CA1 area. Neuroreport 2002; 13:2577-80. [PMID: 12499871 DOI: 10.1097/00001756-200212200-00039] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Multiple calcium signaling pathways, including intracellular calcium release that is mediated by inositol triphosphate (IP3) or ryanodine calcium store receptors, seem to be involved in CA1 hippocampal synaptic plasticity. We have addressed the role of dendritic calcium release in short- and long-term potentiation (STP and LTP) using thapsigargin, which depletes intracellular calcium stores. Measuring Fura-2 calcium signals and extracellular field potentials, we have found that thapsigargin did not affect single pre-tetanus calcium transients but reduced tetanically evoked calcium changes. The latter effect prevented the formation of short- and long-lasting calcium enhancements. These results are consistent with the idea that intracellular calcium release is not involved in baseline synaptic transmission but is essential for those forms of synaptic plasticity.
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Affiliation(s)
- Carlos Matias
- Department of Zoology, Faculty of Sciences, University of Lisbon, Campo Grande 1700 Lisbon, Portugal
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13
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Matias C, Foley P, Quinta-Ferreira ME. L-AP3 blocks rises in intracellular calcium associated with hippocampal CA1 LTP. Neuroreport 2002; 13:751-5. [PMID: 11997681 DOI: 10.1097/00001756-200205070-00004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The involvement of type I metabotropic glutamate receptors in hippocampal CA1 long-term potentiation (LTP) depends on the applied tetanic stimulation protocol. Activation of these receptors may cause an elevation of intracellular calcium via the formation of the second messenger inositol triphosphate (IP3) and subsequent intracellular calcium release. It has been shown that the type I metabotropic receptors antagonist L-2-amino-3-phosphonopropionate (L-AP3) blocks CA1 LTP. Combining dendritic calcium and field potential measurements in CA1 hippocampal area, we found that L-AP3 did not affect single calcium transients but reduced the calcium changes evoked by a single tetanus, preventing the long-lasting calcium enhancements associated with CA1 LTP. These findings suggest that the formation of this type of LTP requires calcium release from IP3-sensitive stores.
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Affiliation(s)
- Carlos Matias
- Physics Department, University of Trás-os-montes e Alto Douro, 5001-911 Vila Real, Portugal
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14
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Vanderklish PW, Edelman GM. Dendritic spines elongate after stimulation of group 1 metabotropic glutamate receptors in cultured hippocampal neurons. Proc Natl Acad Sci U S A 2002; 99:1639-44. [PMID: 11818568 PMCID: PMC122243 DOI: 10.1073/pnas.032681099] [Citation(s) in RCA: 165] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Changes in the morphology of dendritic spines are correlated with synaptic plasticity and may relate mechanistically to its expression and stabilization. Recent work has shown that spine length can be altered by manipulations that affect intracellular calcium, and spine length is abnormal in genetic conditions affecting protein synthesis in neurons. We have investigated how ligands of group 1 metabotropic glutamate receptors (mGluRs) affect spine shape; stimulation of these receptors leads both to calcium release from intracellular stores and to dendritic protein synthesis. Thirty-minute incubation of cultured hippocampal slices and dissociated neurons with the selective group 1 mGluR agonist (S)-3,5-dihydroxyphenylglycine (DHPG) induced a significant increase in the average length of dendritic spines. This elongation resulted mainly from the growth of existing spines and was also seen even in the presence of antagonists of ionotropic receptors, indicating that activation of these receptors by mGluR-induced glutamate release was not required. Prolonged antagonism of group 1 mGluRs with (S)-alpha-methyl-4-carboxyphenylglycine (MCPG) did not result in shorter average spine length. Elongation of dendritic spines induced by DHPG was blocked by calcium chelation and by preincubation with the protein synthesis inhibitor puromycin. The results suggest that in vivo activation of group 1 mGluRs by synaptically released glutamate affects spine shape in a protein synthesis-dependent manner.
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Affiliation(s)
- Peter W Vanderklish
- Department of Neurobiology, The Scripps Research Institute 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
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15
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Canossa M, Gärtner A, Campana G, Inagaki N, Thoenen H. Regulated secretion of neurotrophins by metabotropic glutamate group I (mGluRI) and Trk receptor activation is mediated via phospholipase C signalling pathways. EMBO J 2001; 20:1640-50. [PMID: 11285228 PMCID: PMC145457 DOI: 10.1093/emboj/20.7.1640] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Neurotrophins (NTs) play an essential role in modulating activity-dependent neuronal plasticity. In this context, the site and extent of NT secretion are of crucial importance. Here, we demonstrate that the activation of phospolipase C (PLC) and the subsequent mobilization of Ca(2+) from intracellular stores are essential for NT secretion initiated by both Trk and glutamate receptor activation. Mutational analysis of tyrosine residues, highly conserved in the cytoplasmic domain of all Trk receptors, revealed that the activation of PLC-gamma in cultured hippocampal neurons and nnr5 cells is necessary to mobilize Ca(2+) from intracellular stores, the key mechanism for regulated NT secretion. A similar signalling mechanism has been identified for glutamate-mediated NT secretion-which in part depends on the activation of PLC via metabotropic receptors-leading to the mobilization of Ca(2+) from internal stores by inositol trisphosphate. Thus, PLC-mediated signal transduction pathways are the common mechanisms for both Trk- and mGluRI-mediated NT secretion.
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Affiliation(s)
- Marco Canossa
- Department of Neurobiochemistry, Max-Planck Institute of Neurobiology, Am Klopferspitz 18A, D-82152 Martinsried, Germany, Department of Pharmacology, University of Bologna, Irnerio 48, I-40126 Bologna, Italy and Division of Signal Transduction, Nara Institute of Science and Technology, Ikoma 630-0101, Japan Corresponding author e-mail:
| | - Annette Gärtner
- Department of Neurobiochemistry, Max-Planck Institute of Neurobiology, Am Klopferspitz 18A, D-82152 Martinsried, Germany, Department of Pharmacology, University of Bologna, Irnerio 48, I-40126 Bologna, Italy and Division of Signal Transduction, Nara Institute of Science and Technology, Ikoma 630-0101, Japan Corresponding author e-mail:
| | - Gabriele Campana
- Department of Neurobiochemistry, Max-Planck Institute of Neurobiology, Am Klopferspitz 18A, D-82152 Martinsried, Germany, Department of Pharmacology, University of Bologna, Irnerio 48, I-40126 Bologna, Italy and Division of Signal Transduction, Nara Institute of Science and Technology, Ikoma 630-0101, Japan Corresponding author e-mail:
| | - Naoyuki Inagaki
- Department of Neurobiochemistry, Max-Planck Institute of Neurobiology, Am Klopferspitz 18A, D-82152 Martinsried, Germany, Department of Pharmacology, University of Bologna, Irnerio 48, I-40126 Bologna, Italy and Division of Signal Transduction, Nara Institute of Science and Technology, Ikoma 630-0101, Japan Corresponding author e-mail:
| | - Hans Thoenen
- Department of Neurobiochemistry, Max-Planck Institute of Neurobiology, Am Klopferspitz 18A, D-82152 Martinsried, Germany, Department of Pharmacology, University of Bologna, Irnerio 48, I-40126 Bologna, Italy and Division of Signal Transduction, Nara Institute of Science and Technology, Ikoma 630-0101, Japan Corresponding author e-mail:
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Gee CE, Woodhall G, Lacaille JC. Synaptically activated calcium responses in dendrites of hippocampal oriens-alveus interneurons. J Neurophysiol 2001; 85:1603-13. [PMID: 11287484 DOI: 10.1152/jn.2001.85.4.1603] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activation of metabotropic glutamate receptors (mGluRs) by agonists increases intracellular calcium levels ([Ca(2+)](i)) in interneurons of stratum oriens/alveus (OA) of the hippocampus. We examined the mechanisms that contribute to dendritic Ca(2+) increases in these interneurons during agonist activation of mGluRs and during synaptically evoked burst discharges, using simultaneous whole cell recordings and confocal Ca(2+) imaging in rat hippocampal slices. First, we found that the group I/II mGluR agonist 1S,3R-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD; 100 microM) increased dendritic [Ca(2+)](i) and depolarized OA interneurons. Dendritic Ca(2+) responses were correlated with membrane depolarizations, but Ca(2+) responses induced by ACPD were larger in amplitude than those elicited by equivalent somatic depolarization. Next, we used linescans to measure changes in dendritic [Ca(2+)](i) during synaptically evoked burst discharges and somatically elicited repetitive firing in disinhibited slices. Dendritic Ca(2+) signals and electrophysiological responses were stable over repeated trials. Peak Ca(2+) responses were linearly related to number and frequency of action potentials in burst discharges for both synaptic and somatic stimulation, but the slope of the relationship was steeper for responses evoked somatically. Synaptically evoked [Ca(2+)](i) rises and excitatory postsynaptic potentials were abolished by antagonists of ionotropic glutamate receptors. The group I/II mGluR antagonist S-alpha-methyl-4-carboxyphenylglycine (500 microM) produced a significant partial reduction of synaptically evoked dendritic Ca(2+) responses. The mGluR antagonist did not affect synaptically evoked burst discharges and did not reduce either Ca(2+) responses or burst discharges evoked somatically. Therefore ionotropic glutamate receptors appear necessary for synaptically evoked dendritic Ca(2+) responses, and group I/II mGluRs may contribute partially to these responses. Dendritic [Ca(2+)](i) rises mediated by both ionotropic and metabotropic glutamate receptors may be important for synaptic plasticity and the selective vulnerability to excitotoxicity of OA interneurons.
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Affiliation(s)
- C E Gee
- Centre de Recherche en Sciences Neurologiques, Département de Physiologie, Université de Montréal, Montreal, Quebec H3C 3J7, Canada
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Role of Ca2+ stores in metabotropic L-glutamate receptor-mediated supralinear Ca2+ signaling in rat hippocampal neurons. J Neurosci 2001. [PMID: 11102467 DOI: 10.1523/jneurosci.20-23-08628.2000] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The role of metabotropic l-glutamate (mGlu) receptors in supralinear Ca(2+) signaling was investigated in cultured hippocampal cells using Ca(2+) imaging techniques and whole-cell voltage-clamp recording. In neurons, but not glia, global supralinear Ca(2+) release from intracellular stores was observed when the mGlu receptor agonist (RS)-3,5-dihydroxyphenylglycine (DHPG) was combined with elevated extracellular K(+) levels (10.8 mm), moderate depolarization (15-30 mV), or NMDA (3 micrometer). There was a delay (2-8 min) before the stores were fully charged, and the enhancement persisted for a short period (up to 10 min) after removal of the store-loading stimulus. Studies with the mGlu receptor antagonist 2-methyl-6-(phenylethynyl)-pyridine demonstrated that these effects were mediated by activation of the mGlu(5) receptor subtype. The L-type voltage-gated Ca(2+) channel antagonist nifedipine (10 micrometer) substantially reduced responses to DHPG obtained in the presence of elevated extracellular K(+) but not NMDA. This suggests that the Ca(2+) that is required to load the stores can enter either through L-type voltage-gated Ca(2+) channels or directly through NMDA receptors. The findings that both depolarization and NMDA receptor activation can facilitate mGlu receptor Ca(2+) signaling adds considerable flexibility to the processes that underlie activity-dependent changes in synaptic strength. In particular, a temporal separation between the store-loading stimulus and the activation of mGlu receptors could be used as a recency detector in neurons.
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18
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Doherty AJ, Palmer MJ, Bortolotto ZA, Hargreaves A, Kingston AE, Ornstein PL, Schoepp DD, Lodge D, Collingridge GL. A novel, competitive mGlu(5) receptor antagonist (LY344545) blocks DHPG-induced potentiation of NMDA responses but not the induction of LTP in rat hippocampal slices. Br J Pharmacol 2000; 131:239-44. [PMID: 10991916 PMCID: PMC1572327 DOI: 10.1038/sj.bjp.0703574] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2000] [Revised: 06/29/2000] [Accepted: 06/30/2000] [Indexed: 11/08/2022] Open
Abstract
1. We have investigated the pharmacological properties of LY344545, a structurally related epimer of the broad spectrum competitive metabotropic glutamate receptor antagonist, LY341495. We have found that LY344545 also antagonizes competitively nearly all mGlu receptor subtypes, but with a wide spectrum of activity. The order of potency for the human receptor isoforms was mGlu(5a) (IC(50) of 5. 5+/-0.6 microM)>mGlu(2)=mGlu(3)>mGlu(1alpha)=mG lu(7)>mGlu(6)=mGlu(8). No significant mGlu(4) receptor antagonist activity was detected at the highest concentration used (100 microM). 100 microM LY344545 displaced 50+/-5% of [(3)H]-CGP39653 binding, but less than 30% of [(3)H]-kainate or [(3)H]-AMPA in radioligand binding assays. 2. LY344545 antagonized L-glutamate stimulated Ca(2+) release in CHO cells transfected with mGlu receptors in a concentration dependent manner with a 10 fold higher affinity for the rat mGlu(5a) receptor (K:(i)=2.1+/-0.6 microM) compared to the rat mGlu(1alpha) receptor (K:(i)=20.5+/-2.1 microM). 50 microM (1S, 3R)-ACPD-induced Ca(2+) rises in hippocampal CA1 neurones were also antagonized (IC(50)=6. 8+/-0.7 microM). 3. LY344545 antagonized 10 microM (S)-3,5-DHPG-induced potentiation of NMDA depolarizations in CA1 neurones (EC(50)=10. 6+/-1.0 microM). At higher concentrations (> or =100 microM), LY344545 was an NMDA receptor antagonist. 4. LY344545 also blocked the induction, but not the expression, of LTP at CA3 to CA1 synapses with an IC(50)>300 microM. This effect is consistent with its weak activity at NMDA receptors. 5. These results demonstrate that the binding of ligands to mGlu receptor subtypes is critically dependent on the spatial orientation of the same molecular substituents within a given chemical pharmacophore. The identification of LY344545 as the first competitive antagonist to show selectivity towards mGlu(5) receptors supports the potential to design more selective and potent competitive antagonists of this receptor. 6. These results further indicate that mGlu receptor-mediated potentiation of NMDA responses is not essential for the induction of LTP.
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Affiliation(s)
- A J Doherty
- MRC Centre for Synaptic Plasticity, Department of Anatomy, School of Medical Sciences, University of Bristol, University Walk, Bristol, BS8 1TD.
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19
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Fukunaga K, Muller D, Ohmitsu M, Bakó E, DePaoli-Roach AA, Miyamoto E. Decreased protein phosphatase 2A activity in hippocampal long-term potentiation. J Neurochem 2000; 74:807-17. [PMID: 10646534 DOI: 10.1046/j.1471-4159.2000.740807.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Using autophosphorylated Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) as substrate, we now find that long-term potentian (LTP) induction and maintenance are also associated with a significant decrease in calyculin A-sensitive protein phosphatase (protein phosphatase 2A) activity, without changes in Mg2+-dependent protein phosphatase (protein phosphatase 2C) activity. This decrease in protein phosphatase 2A activity was prevented when LTP induction was inhibited by treatment with calmidazolium or D-2-amino-5-phosphonopentanoic acid. In addition, the application of high-frequency stimulation to 32P-labeled hippocampal slices resulted in increases in the phosphorylation of a 55-kDa protein immunoprecipitated with anti-phosphatase 2A antibodies. Use of a specific antibody revealed that the 55-kDa protein is the B'alpha subunit of protein phosphatase 2A. Following purification of brain protein phosphatase 2A, the B'alpha subunit was phosphorylated by CaM kinase II, an event that led to the reduction of protein phosphatase 2A activity. These results suggest that the decreased activity in protein phosphatase 2A following LTP induction contributes to the maintenance of constitutively active CaM kinase II and to the long-lasting increase in phosphorylation of synaptic components implicated in LTP.
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Affiliation(s)
- K Fukunaga
- Department of Pharmacology, Kumamoto University School of Medicine, Japan.
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20
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Shigemoto R, Mizuno N. Chapter III Metabotropic glutamate receptors — immunocytochemical and in situ hybridization analyses. GLUTAMATE 2000. [DOI: 10.1016/s0924-8196(00)80044-5] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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21
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Nakamura T, Barbara JG, Nakamura K, Ross WN. Synergistic release of Ca2+ from IP3-sensitive stores evoked by synaptic activation of mGluRs paired with backpropagating action potentials. Neuron 1999; 24:727-37. [PMID: 10595522 DOI: 10.1016/s0896-6273(00)81125-3] [Citation(s) in RCA: 264] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Increases in postsynaptic [Ca2+]i can result from Ca2+ entry through ligand-gated channels or voltage-gated Ca2+ channels, or through release from intracellular stores. Most attention has focused on entry through the N-methyl-D-aspartate (NMDA) receptor in causing [Ca2+]i increases since this pathway requires both presynaptic stimulation and postsynaptic depolarization, making it a central component in models of synaptic plasticity. Here, we report that repetitive synaptic activation of metabotropic glutamate receptors (mGluRs), paired with backpropagating action potentials, causes large, wave-like increases in [Ca2+]i predominantly in restricted regions of the proximal apical dendrites and soma of hippocampal CA1 pyramidal neurons. [Ca2+]i changes of several micromolars can be reached by regenerative release caused by the synergistic effect of mGluR-generated inositol 1,4,5-trisphosphate (IP3) and spike-evoked Ca2+ entry acting on the IP3 receptor.
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Affiliation(s)
- T Nakamura
- Department of Physiology, New York Medical College, Valhalla 10595, USA
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22
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Takechi H, Eilers J, Konnerth A. A new class of synaptic response involving calcium release in dendritic spines. Nature 1998; 396:757-60. [PMID: 9874373 DOI: 10.1038/25547] [Citation(s) in RCA: 324] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In the classical view, transmission of signals across synapses in the mammalian brain involves changes in the membrane potential of the postsynaptic cell. The use of high-resolution cellular imaging has revealed excitatory synapses at which postsynaptic, transient alterations in calcium ion concentration are tightly associated with electrical responses. Here, by investigating the synapse between parallel glutamatergic fibres and Purkinje cells in the mouse cerebellum, we identify a class of postsynaptic responses that consist of transient increases in dendritic Ca2+ concentration but not changes in somatic membrane potential. Our results indicate that these synaptic Ca2+ transients are mediated by activation of metabotropic glutamate-responsive mGluR1-type receptors and require inositol-1,4,5-trisphosphate-mediated Ca2+ release from intradendritic stores. The new type of synaptic response is restricted to postsynaptic microdomains, which range, depending on the frequency of stimulation, from individual spines to small spinodendritic compartments. Thus, the synaptic Ca2+-release signal may be one of the critical cues that determine the input specificity of long-term depression, a well-established form of activity-dependent plasticity at these synapses.
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Affiliation(s)
- H Takechi
- I. Physiologisches Institut, Universität des Saarlandes, Homburg, Germany
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23
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Abstract
A major effort in neuroscience is directed towards understanding the roles of Ca2+ signalling in the induction of synaptic plasticity. Here, we summarize the evidence concerning Ca2+ signalling, paying particular attention to CA1 excitatory synapses, and its relationship to the induction of long-term potentiation and long-term depression. We discuss the ways in which synaptic activation can elevate Ca2+ postsynaptically and how dendritic spines may act as a Ca2+ compartment which can both isolate and integrate Ca2+ signals.
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Affiliation(s)
- R Chittajallu
- Department of Anatomy, Medical School, University of Bristol, UK.
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24
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Abstract
The involvement of metabotropic glutamate receptors (mGluRs) in hippocampal long-term potentiation (LTP) is a matter of controversial debate. Using [Ca2+]i measurements by confocal laser scanning microscopy and field recordings of EPSPs (fEPSPs) in the hippocampal CA1-region, we found that the efficacy of the broad-spectrum mGluR-antagonist (S)-alpha-methyl-4-carboxyphenylglycine (MCPG) and of (S)-4-carboxy-phenylglycine (4-CPG), a selective antagonist at class I mGluRs, in LTP is contingent on the tetanization strength and the resulting [Ca2+]i response. As indicated by experiments in which we blocked voltage-dependent calcium channels (VDCCs) and intracellular Ca2+ stores (ICSs), the functional significance of class I mGluRs in LTP is confined to certain types of potentiation, which are induced by weak tetanization protocols and require the release of Ca2+ from ICSs for induction. During strong tetanic stimulation, this Ca2+ source is functionally bypassed by activating VDCCs.
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25
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Affiliation(s)
- M J Berridge
- The Babraham Institute, Babraham Laboratory of Molecular Signalling, Cambridge, United Kingdom
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26
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Matzel LD, Talk AC, Muzzio IA, Rogers RF. Ubiquitous molecular substrates for associative learning and activity-dependent neuronal facilitation. Rev Neurosci 1998; 9:129-67. [PMID: 9833649 DOI: 10.1515/revneuro.1998.9.3.129] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Recent evidence suggests that many of the molecular cascades and substrates that contribute to learning-related forms of neuronal plasticity may be conserved across ostensibly disparate model systems. Notably, the facilitation of neuronal excitability and synaptic transmission that contribute to associative learning in Aplysia and Hermissenda, as well as associative LTP in hippocampal CA1 cells, all require (or are enhanced by) the convergence of a transient elevation in intracellular Ca2+ with transmitter binding to metabotropic cell-surface receptors. This temporal convergence of Ca2+ and G-protein-stimulated second-messenger cascades synergistically stimulates several classes of serine/threonine protein kinases, which in turn modulate receptor function or cell excitability through the phosphorylation of ion channels. We present a summary of the biophysical and molecular constituents of neuronal and synaptic facilitation in each of these three model systems. Although specific components of the underlying molecular cascades differ across these three systems, fundamental aspects of these cascades are widely conserved, leading to the conclusion that the conceptual semblance of these superficially disparate systems is far greater than is generally acknowledged. We suggest that the elucidation of mechanistic similarities between different systems will ultimately fulfill the goal of the model systems approach, that is, the description of critical and ubiquitous features of neuronal and synaptic events that contribute to memory induction.
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Affiliation(s)
- L D Matzel
- Department of Psychology, Program in Biopsychology and Behavioral Neuroscience, Rutgers University, New Brunswick, NJ 08854-8020, USA
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27
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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: 109] [Impact Index Per Article: 4.2] [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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28
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Schwartz NE, Alford S. Modulation of pre- and postsynaptic calcium dynamics by ionotropic glutamate receptors at a plastic synapse. J Neurophysiol 1998; 79:2191-203. [PMID: 9535978 DOI: 10.1152/jn.1998.79.4.2191] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
This study was conducted to assess the role of ionotropic glutamate receptors in the modulation of calcium dynamics on both sides of a vertebrate plastic synapse. Retrograde labeling of neuronal elements with high-affinity calcium-sensitive dyes was used in conjunction with confocal imaging techniques in an in vitro lamprey brain stem preparation. A prolonged calcium transient was measured both pre- and postsynaptically in response to a period of high-frequency ("tetanic") stimulation to the vestibulospinal-reticulospinal synapse. The ionotropic glutamate receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (10 microM) and D,L-2-amino-5-phosphonopentanoate (D,L-AP5; 100 microM) reduced the calcium signal in both compartments of the synapse. The presynaptic D,L-AP5-sensitive component was enhanced markedly by the removal of Mg2+ from the superfusate. Increasing the extracellular stimulus intensity progressively augmented the presynaptic calcium signal, suggesting the recruitment of excitatory axo-axonic inputs onto these fibers. Further, the presence of an excitatory amino acid-mediated presynaptic potential underlying a component of the Ca2+ signal was demonstrated by electrophysiological recordings from vestibulospinal axons. Bath application of agonist, in the presence of tetrodotoxin (1 microM), confirmed the existence of N-methyl-D-aspartate receptors at the presynaptic element capable of modulating calcium levels. The postsynaptic Ca2+ response, which is known to be necessary for long-term potentiation (LTP) induction at this synapse, was localized to areas of the dendritic tree that correlated with the location of known synaptic inputs; thus the synaptically activated rise in postsynaptic calcium may confer the synapse specificity of LTP induction previously demonstrated. In summary, we have demonstrated the existence of physiologically activated presynaptic ionotropic glutamate receptors that are capable of modulating levels of intracellular calcium and have highlighted the importance of receptor-mediated increases in postsynaptic calcium for neuronal plasticity in the lamprey.
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Affiliation(s)
- N E Schwartz
- Department of Physiology, Northwestern University Medical School, Chicago, Illinois 60611, USA
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29
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Vickery RM, Morris SH, Bindman LJ. Metabotropic glutamate receptors are involved in long-term potentiation in isolated slices of rat medial frontal cortex. J Neurophysiol 1997; 78:3039-46. [PMID: 9405523 DOI: 10.1152/jn.1997.78.6.3039] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The prelimbic region of medial frontal cortex in the rat receives a direct input from the hippocampus and this functional connection is essential for aspects of spatial memory. Activity-dependent changes in the effectiveness of synaptic transmission in the medial frontal cortex, namely long-term potentiation (LTP) and long-term depression (LTD) can persist for tens of minutes or hours and may be the basis of learning and memory storage. Glutamatergic activation of ionotropic receptors is required to induce both LTP and LTD. We now present evidence of the involvement of metabotropic glutamate receptors in LTP in isolated slices of frontal cortex. Repetitive bursts of stimulation at theta frequencies (TBS) were applied to layer II, and monosynaptic EPSPs were monitored in layer V neurons of the prelimbic area. TBS was found to be more effective at inducing LTP than tetanic stimulation at 100 Hz and produced LTP that lasted >30 min in 8 out of 14 neurons. Tetanic stimulation at 100 Hz in the presence of the N-methyl--aspartate (NMDA)-antagonist 2-amino-5-phosphonopentanoate (AP5) was reported to be a reliable method of inducing LTD in prelimbic cortex (). However we found that this protocol did not facilitate the induction of LTD. The role of metabotropic glutamate receptors (mGluR) in LTP was assessed by using the selective, broad-spectrum antagonist (R, S)-alpha-methyl-4- carboxyphenylglycine (MCPG). This drug significantly reduced the incidence of LTP after TBS to only 1 of 14 neurons (P < 0.02, chi2 test). The pooled responses to TBS in MCPG showed significantly reduced potentiation [(P < 0.02, analysis of variance (ANOVA)]. The broad-spectrum mGluR agonist (1S, 3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD) and the selective group I agonist S-3 hydroxyphenylglycine(S-3HPG) both produced membrane depolarization, an increase in number of spikes evoked by depolarizing current pulses, and a reduction in the afterhyperpolarization. Similar effects were produced by these agonists even when synaptic transmission was blocked by use of the gamma-aminobutyric acid-B (GABAB) receptor agonist, 200 microM baclofen, which suggests that group I mGluRs are present on layer V neurons. We conclude that mGluRs participate in the production of LTP in prelimbic cortex, and that this excitatory effect could be mediated by the postsynaptic group I mGluRs.
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Affiliation(s)
- R M Vickery
- Department of Physiology, University College London, London WC1E 6BT, United Kingdom
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30
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Afferent innervation influences the development of dendritic branches and spines via both activity-dependent and non-activity-dependent mechanisms. J Neurosci 1997. [PMID: 9236241 DOI: 10.1523/jneurosci.17-16-06314.1997] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The present investigation uses an in vitro co-culture system to study the role of afferent innervation in early development and differentiation of hippocampal neurons. Our experiments indicate that the formation of two key morphological features, dendritic branches and dendritic spines, is induced by afferent innervation. Hippocampal neurons develop multiple dendritic branches and spines only when extensively innervated by living axonal afferents. No morphological changes occurred when hippocampal neurons were plated on other cell surfaces such as fixed axons or astrocytes. Furthermore, afferents exerted their effect locally on individual dendrites that they contacted. When one portion of the dendritic arbor of a neuron was contacted by afferents and the other portion was not, morphological effects were restricted to the innervated dendrites. Innervation of some of the dendrites on a neuron did not produce global effects throughout the neuron. Afferent-induced dendritic branching is independent of activity, since branch induction was unaffected by chronic application of TTX or glutamate receptor blockers. In contrast, the formation of dendritic spines is influenced by activity. The number of developing spines was reduced when TTX or a cocktail of three glutamate receptor blockers was applied. Blockade of individual AMPA, NMDA, or metabotropic glutamate receptors did not affect the number of spines. These results, taken together, demonstrate that afferents can have a prominent influence on the development of postsynaptic target cells via both activity-dependent and non-activity-dependent mechanisms, indicating the presence of multiple signals. Accordingly, this suggests an important interplay between pre- and postsynaptic elements early in development.
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31
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Inglefield JR, Schwartz-Bloom RD. Confocal imaging of intracellular chloride in living brain slices: measurement of GABAA receptor activity. J Neurosci Methods 1997; 75:127-35. [PMID: 9288644 DOI: 10.1016/s0165-0270(97)00054-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: 02/05/2023]
Abstract
We have developed a method using UV laser-scanning confocal microscopy and the fluorescent chloride ion indicator, 6-methoxy-N-ethylquinolinium chloride (MEQ), to image GABA-mediated changes in intracellular chloride (Cli-) in individual neurons of the rat acute brain slice. After bath-loading slices with the cell-permeant form (reduced) of MEQ, there was intense fluorescence within neurons of diverse morphologies in the hippocampus, neocortex and cerebellum. MEQ fluorescence localized to the cytosolic compartment of both the somata and proximal dendrites. MEQ fluorescence was calibrated using the ionophores nigericin and tributyltin in the presence of varying extracellular Cl- concentrations. Neuronal MEQ fluorescence was inversely related to intracellular Cl-, with a Stern-Volmer constant of 16 M-1 (50% quench by 61 mM Cl-). Application of GABA in the perfusate produced a concentration-dependent decrease in MEQ fluorescence (EC50 = 40 microM) that was blocked in the presence of the Cl- channel antagonist, picrotoxin. Bath perfusion of hippocampal slices with modulators of the GABAA receptor, pentobarbital and diazepam, potentiated the GABA-mediated response by 85 and 44%, respectively. A regional comparison identified larger GABA responses for both cerebellar Purkinje and granule cells relative to pyramidal neurons of the hippocampus and neocortex and to hippocampal interneurons. Pressure ejection of the GABAA agonist, muscimol (40 microM), from a micropipet onto individual hippocampal neurons allowed the measurement of rapid responses (1-5 s), compared to those obtained with bath application. Thus, optical imaging of [Cl-]i using MEQ and UV-laser-scanning confocal microscopy provides investigators with a new method to study GABAA pharmacology in neighboring neurons and perhaps even in the soma versus dendrites simultaneously, within living brain slices.
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Affiliation(s)
- J R Inglefield
- Department of Pharmacology, Duke University Medical Center, Durham, NC 27710, USA.
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32
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A long-lasting calcium-activated nonselective cationic current is generated by synaptic stimulation or exogenous activation of group I metabotropic glutamate receptors in CA1 pyramidal neurons. J Neurosci 1997. [PMID: 9204921 DOI: 10.1523/jneurosci.17-14-05366.1997] [Citation(s) in RCA: 136] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We have shown previously that a selective metabotropic glutamate receptor (mGluR) agonist, 1S,3R-1-aminocyclo-pentane-1, 3-dicarboxylate (1S,3R-ACPD), evokes an inward current in CA1 pyramidal neurons of rat hippocampal slices in the presence of K+ channel blockers (). This current has been characterized as a Ca2+-activated nonselective cationic (CAN) current. Using whole-cell patch-clamp recordings and intracellular dialysis, we now have identified the mGluR subtype and the mechanisms underlying the CAN current (ICAN) and report for the first time the presence of a synaptic ICAN in the mammalian CNS. First, we have shown pharmacologically that activation of ICAN by 1S,3R-ACPD involves the group I mGluRs (and not the groups II and III) and a G-protein-dependent process. We also report that ICAN is modulated by the divalent cations (Mg2+, Cd2+, and Zn2+). Second, we have isolated a slow synaptic inward current evoked by a high-frequency stimulation in the presence of K+ channel blockers, ionotropic glutamate, and GABAA receptor antagonists. This current shows similar properties to the exogenously evoked ICAN: its reversal potential is close to the reversal potential of the 1S, 3R-ACPD-evoked ICAN, and it is G-protein- and Ca2+-dependent. Because the amplitude and duration of ICAN increased in the presence of a glutamate uptake blocker, we suggest that this synaptic current is generated via the activation of mGluRs. We propose that the synaptic ICAN, activated by a brief tetanic stimulation and leading to a long-lasting inward current, may be involved in neuronal plasticity and synchronized network-driven oscillations.
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Abstract
Recent advances in optical imaging technology have enabled the measurement of Ca2+ dynamics in individual synaptic spines with high time resolution. Results from work using this new technology have confirmed the view that individual synaptic spines can act as functional chemical compartments with independent dynamics of second-messenger concentration. In particular, the ability of Ca2+ to directly mediate Hebbian coincidence detection has been confirmed.
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Affiliation(s)
- W Denk
- Bell Laboratories, Lucent Technologies, 700 Mountain Avenue, Murray Hill, New Jersey 07974, USA
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Onodera S, Hicks TP. Patterns of transmitter labelling and connectivity of the cat's nucleus of Darkschewitsch: a wheat germ agglutinin-horseradish peroxidase and immunocytochemical study at light and electron microscopical levels. J Comp Neurol 1995; 361:553-73. [PMID: 8576414 DOI: 10.1002/cne.903610402] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Immunocytochemical studies using antibodies raised against a number of probable synaptic transmitters of the mesodiencephalic area, and fibre-tracing studies using wheat germ agglutinin-horseradish peroxidase (WGA-HRP), have been performed in adult cats. Glutamate and aspartate immunoreactivity produced a strong labelling of many cell bodies and terminals in the nucleus of Darkschewitsch (ND). gamma-Aminobutyrate (GABA) immunoreactivity in the ND appeared as a moderate label in some small neurones, and as a strong label in a few glial-like cells, in addition to being present in high levels to produce strong labelling in many GABA-immunopositive terminals that possessed pleomorphic vesicles. Some choline acetyltransferase-positive terminals and dendrites and a few substance P-positive fine fibres possessing varicosities also were observed in the ND. Following WGA-HRP injection in the ND, dense terminal labelling was seen ipsilaterally in the rostral half of the medial accessory olive, suggesting that there may be a certain degree of mediolateral and dorsoventral topographic correspondance within the ND-olive projection. In the same cases, many cell bodies containing HRP reaction product also were found 1) ipsilaterally in the motor cortex, anterior pretectal nucleus, and a restricted area of the caudal part of the substantia nigra pars reticulata; 2) contralaterally in the anterior and posterior interposed cerebellar nuclei as well as in a portion of the lateral cerebellar nucleus; and 3) bilaterally in the zona incerta, the posterior pretectal nucleus, the pedunculopontine tegmental nuclei, the spinal trigeminal nucleus, the dorsal column nuclei, and the spinal cord. Details of the interrelationships and functional considerations amongst the ND, adjacent nuclei, and longitudinal zones of the cerebellum are discussed.
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Affiliation(s)
- S Onodera
- Department of Anatomy, School of Medicine, Iwate Medical University, Morioka, Japan
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Larson-Prior LJ, Morrison PD, Bushey RM, Slater NT. Frequency dependent activation of a slow N-methyl-D-aspartate-dependent excitatory postsynaptic potential in turtle cerebellum by mossy fibre afferents. Neuroscience 1995; 67:867-79. [PMID: 7675211 DOI: 10.1016/0306-4522(94)00074-f] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The synaptic responses of turtle cerebellar Purkinje cells to stimulation of localized mossy fibre systems have been studied by use of intrasomatic and intradendritic recordings in a brainstem-cerebellum preparation in vitro. Activation of mossy fibre inputs from the spinocerebellar pathway evoked fast, disynaptic postsynaptic potentials which were graded in amplitude with stimulus intensity and elicited at latencies consistent with those reported for peripheral nerve stimulation. Repetitive activation (50-100 Hz, 2-10 stimuli) of both spinocerebellar and trigeminocerebellar pathways evoked a slow, long-lasting excitatory postsynaptic potential regardless of whether single stimuli resulted in excitatory, inhibitory, or no postsynaptic responses. This slow potential was capable of triggering dendritic pacemaker discharges in recorded Purkinje cells in addition to volleys of simple spikes when activated at or near resting membrane potential. The fast excitatory synaptic potentials evoked by spinocerebellar stimulation were blocked by the glutamate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione, consistent with the hypothesis that they are mediated by activation of ionotropic glutamate receptors of the alpha-amino-3-hydroxy-5-methylisox-azole-4-proprionic acid subtype at the mossy fibre-granule cell synapse and the subsequent parallel fibre-Purkinje cell synapse. The slow excitatory synaptic potential evoked by repetitive stimulation of either the spinocerebellar tract or trigeminal nerve was blocked by DL-2-amino-5-phosphonvalerate, indicating that this potential is primarily dependent upon N-methyl-D-aspartate receptors at the mossy fibre-granule cell synapse for its expression. This slow potential was reversibly potentiated by L-2-amino-4-phosphonobutyrate and bicuculline; the metabotropic glutamate antagonist (+)-alpha-methyl-4-carboxyphenylglycine did not block this potentiation. The ability of mossy fibre inputs to drive long, slow excitatory events in Purkinje cells adds another dimension to the mechanisms by which various sensory modalities can be processed interactively in the cerebellar cortex. The ability of incoming systems to access a second, longer duration response of the cerebellar output neuron may be of significant consequence to our understanding of the manner in which this neural centre integrates sensory information from multiple sources.
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Affiliation(s)
- L J Larson-Prior
- Department of Neuroscience and Anatomy, Pennsylvania State University College of Medicine, M.S. Hershey Medical Center, Hershey 17033, USA
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Abstract
The intracellular concentration of free Ca2+ ([Ca2+]i) displays complex fluctuations in response to a variety of stimuli, and acts as a pluripotent signal for many neuronal functions. It is well established that various 'metabotropic' neurotransmitter receptors can mediate the mobilization of Ca2+ stores via actions of inositol-polyphosphate second messengers, and more recent evidence suggests that 'ionotropic' receptor-mediated Ca2+ signals in neurones might also involve release of Ca2+ from intracellular stores. These two mechanisms of release of Ca2+ enable considerable temporal and spatial complexity of increases in the [Ca2+]i via multiple interactions at the level of intracellular-receptor activation. The complexity of Ca2+ signalling that is elicited via these interconnecting pathways might underlie mechanisms that are central to information transfer and integration within neuronal compartments.
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Affiliation(s)
- P B Simpson
- Dept of Cell Physiology and Pharmacology, University of Leicester, UK
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Petrozzino JJ, Pozzo Miller LD, Connor JA. Micromolar Ca2+ transients in dendritic spines of hippocampal pyramidal neurons in brain slice. Neuron 1995; 14:1223-31. [PMID: 7605633 DOI: 10.1016/0896-6273(95)90269-4] [Citation(s) in RCA: 124] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The magnitude and dynamics of [Ca2+] changes in spines and dendrites of hippocampal CA1 pyramidal neurons have been characterized using a low affinity fluorescent indicator, mag-Fura 5, that is sensitive to Ca2+ in the micromolar range. During tetanic stimulation (1 s), we observed progressive [Ca2+] increases in distal CA1 spines to as much as 20-40 microM, both in organotypic slice culture and acute slice. Similar accumulations were reached during continuous depolarization (+10 mV, 1 s) when K+ channels had been blocked, but not with spike trains driven by postsynaptic current injection. The large [Ca2+] increases due to tetanic stimulation were blocked by APV, indicating that NMDA receptor-dependent influx was critical for the large responses. These findings have significant implications for low affinity Ca(2+)-dependent biochemical processes and show a new upper limit for [Ca2+] changes measured in these neurons during stimulation.
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Affiliation(s)
- J J Petrozzino
- Roche Institute of Molecular Biology, Roche Research Center, Nutley, New Jersey 07110, USA
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Petrozzino JJ, Connor JA. Dendritic Ca2+ accumulations and metabotropic glutamate receptor activation associated with an N-methyl-D-aspartate receptor-independent long-term potentiation in hippocampal CA1 neurons. Hippocampus 1994; 4:546-58. [PMID: 7889125 DOI: 10.1002/hipo.450040504] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Bathing hippocampal slices in the potassium channel blocker tetraethylammonium (TEA), while stimulating the Schaffer collaterals at a low frequency, induces Ca(2+)-dependent, N-methyl-D-aspartate (NMDA) receptor-independent long-term potentiation of synaptic transmission (LTPk) in CA1 neurons. We have combined ratio imaging of fura-2 and mag-fura-5 in hippocampal CA1 neurons with intracellular and field recordings to evaluate postsynaptic Ca2+ changes that occur in the induction of LTPk. Test stimuli were applied at 0.05 Hz to stratum radiatum in the presence of the NMDA receptor antagonists D,L-2-amino-5-phosphonovaleric acid (100 microM) or MK-801 (10 microM). During TEA exposure (15-25 mM; 10 min), cells fired prolonged action potentials both spontaneously and in response to test stimuli resulting in transient, micromolar Ca2+ accumulations in both somata and dendrites. The initial EPSP slope, measured 60 min after TEA wash-out, was potentiated to approximately 200% of control. The Ca2+ channel blocker nimodipine (10 microM) greatly reduced Ca2+ transients in both magnitude and duration and prevented LTPk induction. Pretreatment of slices with compounds that block metabotropic glutamate receptor (mGluR)-stimulated phosphoinositide hydrolysis, L-2-amino-3-phosphonopropionic acid (L-AP3, 50-200 microM) or L-aspartate-beta-hydroxamate (50-100 microM), as well as protein kinase C (PKC) inhibitors (sphingosine, 20 microM; RO-31-8220, 0.2 microM; or calphostin C, 2 microM) also blocked LTPk. Ca2+ transients were unaffected by L-AP3 or RO-31-8220. These findings suggest that Ca2+ influx through voltage-gated channels and co-activation of PKC by mGluRs are both necessary for induction of LTPk. Activation of mGluRs must also occur in NMDA receptor-dependent induction paradigms, but is possibly of lesser importance owing to the much greater gating of Ca2+ directly into the dendritic spines.
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Affiliation(s)
- J J Petrozzino
- Roche Institute of Molecular Biology, Roche Research Center, Nutley, New Jersey 07110
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Abstract
Further characterization of the biochemical components that contribute to calcium handling, together with advances in optical imaging of ion concentration, are providing quantitative information on the dynamics of calcium in the dendrites of neurons in tissue culture, brain slices and in vivo. It has recently been demonstrated that strong spatial gradients and transient calcium elevations result from the geometry and membrane properties of dendrites. These studies are adding to our understanding of calcium's role in synaptic plasticity and in shaping the electrophysiological properties of neurons.
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Affiliation(s)
- W G Regehr
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115
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Chapter 6. Recent Progress in Excitatory Amino Acid Research. ANNUAL REPORTS IN MEDICINAL CHEMISTRY 1994. [DOI: 10.1016/s0065-7743(08)60719-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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