1
|
Lee CT, Bell M, Bonilla-Quintana M, Rangamani P. Biophysical Modeling of Synaptic Plasticity. Annu Rev Biophys 2024; 53:397-426. [PMID: 38382115 DOI: 10.1146/annurev-biophys-072123-124954] [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] [Indexed: 02/23/2024]
Abstract
Dendritic spines are small, bulbous compartments that function as postsynaptic sites and undergo intense biochemical and biophysical activity. The role of the myriad signaling pathways that are implicated in synaptic plasticity is well studied. A recent abundance of quantitative experimental data has made the events associated with synaptic plasticity amenable to quantitative biophysical modeling. Spines are also fascinating biophysical computational units because spine geometry, signal transduction, and mechanics work in a complex feedback loop to tune synaptic plasticity. In this sense, ideas from modeling cell motility can inspire us to develop multiscale approaches for predictive modeling of synaptic plasticity. In this article, we review the key steps in postsynaptic plasticity with a specific focus on the impact of spine geometry on signaling, cytoskeleton rearrangement, and membrane mechanics. We summarize the main experimental observations and highlight how theory and computation can aid our understanding of these complex processes.
Collapse
Affiliation(s)
- Christopher T Lee
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California, USA;
| | - Miriam Bell
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California, USA;
| | - Mayte Bonilla-Quintana
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California, USA;
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California, USA;
| |
Collapse
|
2
|
Knobloch JA, Laurent G, Lauterbach MA. STED microscopy reveals dendrite-specificity of spines in turtle cortex. Prog Neurobiol 2023; 231:102541. [PMID: 37898315 DOI: 10.1016/j.pneurobio.2023.102541] [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: 06/09/2023] [Revised: 10/20/2023] [Accepted: 10/21/2023] [Indexed: 10/30/2023]
Abstract
Dendritic spines are key structures for neural communication, learning and memory. Spine size and shape probably reflect synaptic strength and learning. Imaging with superresolution STED microscopy the detailed shape of the majority of the spines of individual neurons in turtle cortex (Trachemys scripta elegans) revealed several distinguishable shape classes. Dendritic spines of a given class were not distributed randomly, but rather decorated significantly more often some dendrites than others. The individuality of dendrites was corroborated by significant inter-dendrite differences in other parameters such as spine density and length. In addition, many spines were branched or possessed spinules. These findings may have implications for the role of individual dendrites in this cortex.
Collapse
Affiliation(s)
- Jan A Knobloch
- Department of Molecular Imaging, Center for Integrative Physiology and Molecular Medicine, Saarland University, Building 48, 66421 Homburg, Germany
| | - Gilles Laurent
- Max Planck Institute for Brain Research, Max-von-Laue-Str. 4, 60438 Frankfurt am Main, Germany
| | - Marcel A Lauterbach
- Department of Molecular Imaging, Center for Integrative Physiology and Molecular Medicine, Saarland University, Building 48, 66421 Homburg, Germany; Max Planck Institute for Brain Research, Max-von-Laue-Str. 4, 60438 Frankfurt am Main, Germany.
| |
Collapse
|
3
|
Priel A, Dai XQ, Chen XZ, Scarinci N, Cantero MDR, Cantiello HF. Electrical recordings from dendritic spines of adult mouse hippocampus and effect of the actin cytoskeleton. Front Mol Neurosci 2022; 15:769725. [PMID: 36090255 PMCID: PMC9453158 DOI: 10.3389/fnmol.2022.769725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 07/26/2022] [Indexed: 11/28/2022] Open
Abstract
Dendritic spines (DS) are tiny protrusions implicated in excitatory postsynaptic responses in the CNS. To achieve their function, DS concentrate a high density of ion channels and dynamic actin networks in a tiny specialized compartment. However, to date there is no direct information on DS ionic conductances. Here, we used several experimental techniques to obtain direct electrical information from DS of the adult mouse hippocampus. First, we optimized a method to isolate DS from the dissected hippocampus. Second, we used the lipid bilayer membrane (BLM) reconstitution and patch clamping techniques and obtained heretofore unavailable electrical phenotypes on ion channels present in the DS membrane. Third, we also patch clamped DS directly in cultured adult mouse hippocampal neurons, to validate the electrical information observed with the isolated preparation. Electron microscopy and immunochemistry of PDS-95 and NMDA receptors and intrinsic actin networks confirmed the enrichment of the isolated DS preparation, showing open and closed DS, and multi-headed DS. The preparation was used to identify single channel activities and “whole-DS” electrical conductance. We identified NMDA and Ca2+-dependent intrinsic electrical activity in isolated DS and in situ DS of cultured adult mouse hippocampal neurons. In situ recordings in the presence of local NMDA, showed that individual DS intrinsic electrical activity often back-propagated to the dendrite from which it sprouted. The DS electrical oscillations were modulated by changes in actin cytoskeleton dynamics by addition of the F-actin disrupter agent, cytochalasin D, and exogenous actin-binding proteins. The data indicate that DS are elaborate excitable electrical devices, whose activity is a functional interplay between ion channels and the underlying actin networks. The data argue in favor of the active contribution of individual DS to the electrical activity of neurons at the level of both the membrane conductance and cytoskeletal signaling.
Collapse
Affiliation(s)
- Avner Priel
- The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Xiao-Qing Dai
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - Xing-Zhen Chen
- Department of Physiology, University of Alberta, Edmonton, AB, Canada
| | - Noelia Scarinci
- Laboratorio de Canales Iónicos, Instituto Multidisciplinario de Salud, Tecnología y Desarrollo, Consejo Nacional de Investigaciones Científicas y Técnicas de Argentina (CONICET) - Universidad Nacional de Santiago del Estero (UNSE), Santiago del Estero, Argentina
| | - María del Rocío Cantero
- Laboratorio de Canales Iónicos, Instituto Multidisciplinario de Salud, Tecnología y Desarrollo, Consejo Nacional de Investigaciones Científicas y Técnicas de Argentina (CONICET) - Universidad Nacional de Santiago del Estero (UNSE), Santiago del Estero, Argentina
| | - Horacio F. Cantiello
- Laboratorio de Canales Iónicos, Instituto Multidisciplinario de Salud, Tecnología y Desarrollo, Consejo Nacional de Investigaciones Científicas y Técnicas de Argentina (CONICET) - Universidad Nacional de Santiago del Estero (UNSE), Santiago del Estero, Argentina
- *Correspondence: Horacio F. Cantiello,
| |
Collapse
|
4
|
Bell MK, Holst MV, Lee CT, Rangamani P. Dendritic spine morphology regulates calcium-dependent synaptic weight change. J Gen Physiol 2022; 154:e202112980. [PMID: 35819365 PMCID: PMC9280073 DOI: 10.1085/jgp.202112980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Revised: 05/28/2022] [Accepted: 06/07/2022] [Indexed: 01/14/2023] Open
Abstract
Dendritic spines act as biochemical computational units and must adapt their responses according to their activation history. Calcium influx acts as the first signaling step during postsynaptic activation and is a determinant of synaptic weight change. Dendritic spines also come in a variety of sizes and shapes. To probe the relationship between calcium dynamics and spine morphology, we used a stochastic reaction-diffusion model of calcium dynamics in idealized and realistic geometries. We show that despite the stochastic nature of the various calcium channels, receptors, and pumps, spine size and shape can modulate calcium dynamics and subsequently synaptic weight updates in a deterministic manner. Through a series of exhaustive simulations and analyses, we found that the calcium dynamics and synaptic weight change depend on the volume-to-surface area of the spine. The relationships between calcium dynamics and spine morphology identified in idealized geometries also hold in realistic geometries, suggesting that there are geometrically determined deterministic relationships that may modulate synaptic weight change.
Collapse
Affiliation(s)
- Miriam K. Bell
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA
| | - Maven V. Holst
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA
| | - Christopher T. Lee
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA
| |
Collapse
|
5
|
Song A, Gauthier JL, Pillow JW, Tank DW, Charles AS. Neural anatomy and optical microscopy (NAOMi) simulation for evaluating calcium imaging methods. J Neurosci Methods 2021; 358:109173. [PMID: 33839190 PMCID: PMC8217135 DOI: 10.1016/j.jneumeth.2021.109173] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 03/21/2021] [Accepted: 03/24/2021] [Indexed: 11/20/2022]
Abstract
BACKGROUND The past decade has seen a multitude of new in vivo functional imaging methodologies. However, the lack of ground-truth comparisons or evaluation metrics makes the large-scale, systematic validation vital to the continued development and use of optical microscopy impossible. NEW-METHOD We provide a new framework for evaluating two-photon microscopy methods via in silico Neural Anatomy and Optical Microscopy (NAOMi) simulation. Our computationally efficient model generates large anatomical volumes of mouse cortex, simulates neural activity, and incorporates optical propagation and scanning to create realistic calcium imaging datasets. RESULTS We verify NAOMi simulations against in vivo two-photon recordings from mouse cortex. We leverage this in silico ground truth to directly compare different segmentation algorithms and optical designs. We find modern segmentation algorithms extract strong neural time-courses comparable to estimation using oracle spatial information, but with an increase in the false positive rate. Comparison between optical setups demonstrate improved resilience to motion artifacts in sparsely labeled samples using Bessel beams, increased signal-to-noise ratio and cell-count using low numerical aperture Gaussian beams and nuclear GCaMP, and more uniform spatial sampling with temporal focusing versus multi-plane imaging. COMPARISON WITH EXISTING METHODS NAOMi is a first-of-its kind framework for assessing optical imaging modalities. Existing methods are either anatomical simulations or do not address functional imaging. Thus there is no competing method for simulating realistic functional optical microscopy data. CONCLUSIONS By leveraging the rich accumulated knowledge of neural anatomy and optical physics, we provide a powerful new tool to assess and develop important methods in neural imaging.
Collapse
Affiliation(s)
- Alexander Song
- Princeton Neuroscience Institute, Princeton University, Princeton, 08540 NJ, USA; Department of Physics, Princeton University, Princeton, 08540 NJ, USA
| | - Jeff L Gauthier
- Princeton Neuroscience Institute, Princeton University, Princeton, 08540 NJ, USA
| | - Jonathan W Pillow
- Princeton Neuroscience Institute, Princeton University, Princeton, 08540 NJ, USA; Department of Psychology, Princeton University, Princeton, 08540 NJ, USA
| | - David W Tank
- Princeton Neuroscience Institute, Princeton University, Princeton, 08540 NJ, USA; Bezos Center for Neural Circuit Dynamics, Princeton University, Princeton, 08540 NJ, USA; Department of Molecular Biology, Princeton University, Princeton, 08540 NJ, USA
| | - Adam S Charles
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, 21218, MD, USA; Mathematical Institute for Data Science, Johns Hopkins University, Baltimore, 21218, MD, USA; Center for Imaging Science, Johns Hopkins University, Baltimore, 21218, MD, USA; Kavli Neuroscience Discovery Institute, Johns Hopkins University, Baltimore, 21218, MD, USA
| |
Collapse
|
6
|
Warling A, Uchida R, Shin H, Dodelson C, Garcia ME, Shea-Shumsky NB, Svirsky S, Pothast M, Kelley H, Schumann CM, Brzezinski C, Bauman MD, Alexander A, McKee AC, Stein TD, Schall M, Jacobs B. Putative dendritic correlates of chronic traumatic encephalopathy: A preliminary quantitative Golgi exploration. J Comp Neurol 2020; 529:1308-1326. [PMID: 32869318 DOI: 10.1002/cne.25022] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 08/24/2020] [Accepted: 08/25/2020] [Indexed: 12/14/2022]
Abstract
Chronic traumatic encephalopathy (CTE) is a neurodegenerative disorder that is associated with repetitive head impacts. Neuropathologically, it is defined by the presence of perivascular hyperphosphorylated tau aggregates in cortical tissue (McKee et al., 2016, Acta Neuropathologica, 131, 75-86). Although many pathological and assumed clinical correlates of CTE have been well characterized, its effects on cortical dendritic arbors are still unknown. Here, we quantified dendrites and dendritic spines of supragranular pyramidal neurons in tissue from human frontal and occipital lobes, in 11 cases with (Mage = 79 ± 7 years) and 5 cases without (Mage = 76 ± 11 years) CTE. Tissue was stained with a modified rapid Golgi technique. Dendritic systems of 20 neurons per region in each brain (N = 640 neurons) were quantified using computer-assisted morphometry. One key finding was that CTE neurons exhibited increased variability and distributional changes across six of the eight dendritic system measures, presumably due to ongoing degeneration and compensatory reorganization of dendritic systems. However, despite heightened variation among CTE neurons, CTE cases exhibited lower mean values than Control cases in seven of the eight dendritic system measures. These dendritic alterations may represent a new pathological marker of CTE, and further examination of dendritic changes could contribute to both mechanistic and functional understandings of the disease.
Collapse
Affiliation(s)
- Allysa Warling
- Laboratory of Quantitative Neuromorphology, Neuroscience Program, Department of Psychology, Colorado College, Colorado Springs, Colorado, USA
| | - Riri Uchida
- Laboratory of Quantitative Neuromorphology, Neuroscience Program, Department of Psychology, Colorado College, Colorado Springs, Colorado, USA
| | - Hyunsoo Shin
- Laboratory of Quantitative Neuromorphology, Neuroscience Program, Department of Psychology, Colorado College, Colorado Springs, Colorado, USA
| | - Coby Dodelson
- Laboratory of Quantitative Neuromorphology, Neuroscience Program, Department of Psychology, Colorado College, Colorado Springs, Colorado, USA
| | - Madeleine E Garcia
- Laboratory of Quantitative Neuromorphology, Neuroscience Program, Department of Psychology, Colorado College, Colorado Springs, Colorado, USA
| | - N Beckett Shea-Shumsky
- Laboratory of Quantitative Neuromorphology, Neuroscience Program, Department of Psychology, Colorado College, Colorado Springs, Colorado, USA
| | - Sarah Svirsky
- Department of Neurology, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Morgan Pothast
- Department of Neurology, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Hunter Kelley
- Department of Neurology, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Cynthia M Schumann
- Department of Psychiatry and Behavioral Sciences, University of California, Sacramento, California, USA
| | - Christine Brzezinski
- Department of Neurosurgery, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Melissa D Bauman
- Department of Psychiatry and Behavioral Sciences, University of California, Sacramento, California, USA
| | - Allyson Alexander
- Department of Neurosurgery, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Ann C McKee
- Department of Neurology, Boston University School of Medicine, Boston, Massachusetts, USA.,Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, Massachusetts, USA.,Boston University Alzheimer's Disease and CTE Center, Boston University School of Medicine, Boston, Massachusetts, USA.,VA Boston Healthcare System, Boston, Massachusetts, USA.,Department of Veterans Affairs Medical Center, Bedford, Massachusetts, USA
| | - Thor D Stein
- Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, Massachusetts, USA.,Boston University Alzheimer's Disease and CTE Center, Boston University School of Medicine, Boston, Massachusetts, USA.,VA Boston Healthcare System, Boston, Massachusetts, USA.,Department of Veterans Affairs Medical Center, Bedford, Massachusetts, USA
| | - Matthew Schall
- Laboratory of Quantitative Neuromorphology, Neuroscience Program, Department of Psychology, Colorado College, Colorado Springs, Colorado, USA
| | - Bob Jacobs
- Laboratory of Quantitative Neuromorphology, Neuroscience Program, Department of Psychology, Colorado College, Colorado Springs, Colorado, USA
| |
Collapse
|
7
|
Mäki-Marttunen T, Iannella N, Edwards AG, Einevoll GT, Blackwell KT. A unified computational model for cortical post-synaptic plasticity. eLife 2020; 9:55714. [PMID: 32729828 PMCID: PMC7426095 DOI: 10.7554/elife.55714] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 07/29/2020] [Indexed: 12/15/2022] Open
Abstract
Signalling pathways leading to post-synaptic plasticity have been examined in many types of experimental studies, but a unified picture on how multiple biochemical pathways collectively shape neocortical plasticity is missing. We built a biochemically detailed model of post-synaptic plasticity describing CaMKII, PKA, and PKC pathways and their contribution to synaptic potentiation or depression. We developed a statistical AMPA-receptor-tetramer model, which permits the estimation of the AMPA-receptor-mediated maximal synaptic conductance based on numbers of GluR1s and GluR2s predicted by the biochemical signalling model. We show that our model reproduces neuromodulator-gated spike-timing-dependent plasticity as observed in the visual cortex and can be fit to data from many cortical areas, uncovering the biochemical contributions of the pathways pinpointed by the underlying experimental studies. Our model explains the dependence of different forms of plasticity on the availability of different proteins and can be used for the study of mental disorder-associated impairments of cortical plasticity.
Collapse
Affiliation(s)
| | | | | | - Gaute T Einevoll
- Faculty of Science and Technology, Norwegian University of Life Sciences, Oslo, Norway.,Department of Physics, University of Oslo, Oslo, Norway
| | - Kim T Blackwell
- The Krasnow Institute for Advanced Study, George Mason University, Fairfax, United States
| |
Collapse
|
8
|
Classical-quantum interfaces in living neural tissue supporting conscious functions. ADVANCES IN QUANTUM CHEMISTRY 2020. [DOI: 10.1016/bs.aiq.2020.08.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
9
|
Patwa S, Benson CA, Dyer L, Olson K, Bangalore L, Hill M, Waxman SG, Tan AM. Spinal cord motor neuron plasticity accompanies second-degree burn injury and chronic pain. Physiol Rep 2019; 7:e14288. [PMID: 31858746 PMCID: PMC6923170 DOI: 10.14814/phy2.14288] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Burn injuries and associated complications present a major public health challenge. Many burn patients develop clinically intractable complications, including pain and other sensory disorders. Recent evidence has shown that dendritic spine neuropathology in spinal cord sensory and motor neurons accompanies central nervous system (CNS) or peripheral nervous system (PNS) trauma and disease. However, no research has investigated similar dendritic spine neuropathologies following a cutaneous thermal burn injury. In this retrospective investigation, we analyzed dendritic spine morphology and localization in alpha-motor neurons innervating a burn-injured area of the body (hind paw). To identify a molecular regulator of these dendritic spine changes, we further profiled motor neuron dendritic spines in adult mice treated with romidepsin, a clinically approved Pak1-inhibitor, or vehicle control at two postburn time points: Day 6 immediately after treatment, or Day 10 following drug withdrawal. In control treated mice, we observed an overall increase in dendritic spine density, including structurally mature spines with mushroom-shaped morphology. Pak1-inhibitor treatment reduced injury-induced changes to similar levels observed in animals without burn injury. The effectiveness of the Pak1-inhibitor was durable, since normalized dendritic spine profiles remained as long as 4 days despite drug withdrawal. This study is the first report of evidence demonstrating that a second-degree burn injury significantly affects motor neuron structure within the spinal cord. Furthermore, our results support the opportunity to study dendritic spine dysgenesis as a novel avenue to clarify the complexities of neurological disease following traumatic injury.
Collapse
Affiliation(s)
- Siraj Patwa
- Department of Neurology and Center for Neuroscience and Regeneration ResearchYale University School of MedicineNew HavenConnecticut
- Rehabilitation Research CenterVeterans Affairs Connecticut Healthcare SystemWest HavenConnecticut
| | - Curtis A. Benson
- Department of Neurology and Center for Neuroscience and Regeneration ResearchYale University School of MedicineNew HavenConnecticut
- Rehabilitation Research CenterVeterans Affairs Connecticut Healthcare SystemWest HavenConnecticut
| | - Lauren Dyer
- Department of Neurology and Center for Neuroscience and Regeneration ResearchYale University School of MedicineNew HavenConnecticut
- Rehabilitation Research CenterVeterans Affairs Connecticut Healthcare SystemWest HavenConnecticut
| | - Kai‐Lan Olson
- Department of Neurology and Center for Neuroscience and Regeneration ResearchYale University School of MedicineNew HavenConnecticut
- Rehabilitation Research CenterVeterans Affairs Connecticut Healthcare SystemWest HavenConnecticut
| | - Lakshmi Bangalore
- Department of Neurology and Center for Neuroscience and Regeneration ResearchYale University School of MedicineNew HavenConnecticut
- Rehabilitation Research CenterVeterans Affairs Connecticut Healthcare SystemWest HavenConnecticut
| | - Myriam Hill
- Department of Neurology and Center for Neuroscience and Regeneration ResearchYale University School of MedicineNew HavenConnecticut
- Rehabilitation Research CenterVeterans Affairs Connecticut Healthcare SystemWest HavenConnecticut
| | - Stephen G. Waxman
- Department of Neurology and Center for Neuroscience and Regeneration ResearchYale University School of MedicineNew HavenConnecticut
- Rehabilitation Research CenterVeterans Affairs Connecticut Healthcare SystemWest HavenConnecticut
| | - Andrew M. Tan
- Department of Neurology and Center for Neuroscience and Regeneration ResearchYale University School of MedicineNew HavenConnecticut
- Rehabilitation Research CenterVeterans Affairs Connecticut Healthcare SystemWest HavenConnecticut
| |
Collapse
|
10
|
Cao XC, Pappalardo LW, Waxman SG, Tan AM. Dendritic spine dysgenesis in superficial dorsal horn sensory neurons after spinal cord injury. Mol Pain 2017; 13:1744806916688016. [PMID: 28326929 PMCID: PMC5302173 DOI: 10.1177/1744806916688016] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Neuropathic pain is a major complication of spinal cord injury, and despite aggressive efforts, this type of pain is refractory to available clinical treatment. Our previous work has demonstrated a structure–function link between dendritic spine dysgenesis on nociceptive sensory neurons in the intermediate zone, laminae IV/V, and chronic pain in central nervous system and peripheral nervous system injury models of neuropathic pain. To extend these findings, we performed a follow-up structural analysis to assess whether dendritic spine remodeling occurs on superficial dorsal horn neurons located in lamina II after spinal cord injury. Lamina II neurons are responsible for relaying deep, delocalized, often thermally associated pain commonly experienced in spinal cord injury pathologies. We analyzed dendritic spine morphometry and localization in tissue obtained from adult rats exhibiting neuropathic pain one-month following spinal cord injury. Although the total density of dendritic spines on lamina II neurons did not change after spinal cord injury, we observed an inverse relationship between the densities of thin- and mushroom-shaped spines: thin-spine density decreased while mushroom-spine density increased. These structural changes were specifically noted along dendritic branches within 150 µm from the soma, suggesting a possible adverse contribution to nociceptive circuit function. Intrathecal treatment with NSC23766, a Rac1-GTPase inhibitor, significantly reduced spinal cord injury-induced changes in both thin- and mushroom-shaped dendritic spines. Overall, these observations demonstrate that dendritic spine remodeling occurs in lamina II, regulated in part by the Rac1-signaling pathway, and suggests that structural abnormalities in this spinal cord region may also contribute to abnormal nociception after spinal cord injury.
Collapse
Affiliation(s)
- Xiaoyu C Cao
- 1 Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, USA.,2 Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA
| | - Laura W Pappalardo
- 1 Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, USA.,2 Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA
| | - Stephen G Waxman
- 1 Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, USA.,2 Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA
| | - Andrew M Tan
- 1 Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, USA.,2 Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA
| |
Collapse
|
11
|
Krieger P, de Kock CPJ, Frick A. Calcium Dynamics in Basal Dendrites of Layer 5A and 5B Pyramidal Neurons Is Tuned to the Cell-Type Specific Physiological Action Potential Discharge. Front Cell Neurosci 2017; 11:194. [PMID: 28744201 PMCID: PMC5504123 DOI: 10.3389/fncel.2017.00194] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 06/21/2017] [Indexed: 11/13/2022] Open
Abstract
Layer 5 (L5) is a major neocortical output layer containing L5A slender-tufted (L5A-st) and L5B thick-tufted (L5B-tt) pyramidal neurons. These neuron types differ in their in vivo firing patterns, connectivity and dendritic morphology amongst other features, reflecting their specific functional role within the neocortical circuits. Here, we asked whether the active properties of the basal dendrites that receive the great majority of synaptic inputs within L5 differ between these two pyramidal neuron classes. To quantify their active properties, we measured the efficacy with which action potential (AP) firing patterns backpropagate along the basal dendrites by measuring the accompanying calcium transients using two-photon laser scanning microscopy in rat somatosensory cortex slices. For these measurements we used both "artificial" three-AP patterns and more complex physiological AP patterns that were previously recorded in anesthetized rats in L5A-st and L5B-tt neurons in response to whisker stimulation. We show that AP patterns with relatively few APs (3APs) evoke a calcium response in L5B-tt, but not L5A-st, that is dependent on the temporal pattern of the three APs. With more complex in vivo recorded AP patterns, the average calcium response was similar in the proximal dendrites but with a decay along dendrites (measured up to 100 μm) of L5B-tt but not L5A-st neurons. Interestingly however, the whisker evoked AP patterns-although very different for the two cell types-evoke similar calcium responses. In conclusion, although the effectiveness with which different AP patterns evoke calcium transients vary between L5A-st and L5B-tt cell, the calcium influx appears to be tuned such that whisker-evoked calcium transients are within the same dynamic range for both cell types.
Collapse
Affiliation(s)
- Patrik Krieger
- Department of Cell Physiology, Max Planck Institute for Medical ResearchHeidelberg, Germany.,Department of Systems Neuroscience, Medical Faculty, Ruhr University BochumBochum, Germany
| | - Christiaan P J de Kock
- Department of Cell Physiology, Max Planck Institute for Medical ResearchHeidelberg, Germany.,Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research (CNCR), VU University AmsterdamAmsterdam, Netherlands
| | - Andreas Frick
- Department of Cell Physiology, Max Planck Institute for Medical ResearchHeidelberg, Germany.,INSERM, Neurocentre Magendie, U1215Bordeaux, France.,University of Bordeaux, Neurocentre Magendie, U1215Bordeaux, France
| |
Collapse
|
12
|
Maiti P, Manna J, Ilavazhagan G, Rossignol J, Dunbar GL. Molecular regulation of dendritic spine dynamics and their potential impact on synaptic plasticity and neurological diseases. Neurosci Biobehav Rev 2015; 59:208-37. [PMID: 26562682 DOI: 10.1016/j.neubiorev.2015.09.020] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 08/20/2015] [Accepted: 09/07/2015] [Indexed: 12/12/2022]
Abstract
The structure and dynamics of dendritic spines reflect the strength of synapses, which are severely affected in different brain diseases. Therefore, understanding the ultra-structure, molecular signaling mechanism(s) regulating dendritic spine dynamics is crucial. Although, since last century, dynamics of spine have been explored by several investigators in different neurological diseases, but despite countless efforts, a comprehensive understanding of the fundamental etiology and molecular signaling pathways involved in spine pathology is lacking. The purpose of this review is to provide a contextual framework of our current understanding of the molecular mechanisms of dendritic spine signaling, as well as their potential impact on different neurodegenerative and psychiatric diseases, as a format for highlighting some commonalities in function, as well as providing a format for new insights and perspectives into this critical area of research. Additionally, the potential strategies to restore spine structure-function in different diseases are also pointed out. Overall, these informations should help researchers to design new drugs to restore the structure-function of dendritic spine, a "hot site" of synaptic plasticity.
Collapse
Affiliation(s)
- Panchanan Maiti
- Field Neurosciences Institute, St. Mary's of Michigan, Saginaw, MI, USA; Department of Psychology and Neurosciences Program, Central Michigan University, Mt. Pleasant, MI, USA.
| | - Jayeeta Manna
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN, USA.
| | - G Ilavazhagan
- Hindustan University, Rajiv Gandhi Salai (OMR), Padur, Kelambakam, Chennai, TN, India.
| | - Julien Rossignol
- Department of Psychology and Neurosciences Program, Central Michigan University, Mt. Pleasant, MI, USA; College of Medicine, Central Michigan University, Mt. Pleasant, MI, USA.
| | - Gary L Dunbar
- Field Neurosciences Institute, St. Mary's of Michigan, Saginaw, MI, USA; Department of Psychology and Neurosciences Program, Central Michigan University, Mt. Pleasant, MI, USA.
| |
Collapse
|
13
|
Adrian M, Kusters R, Wierenga CJ, Storm C, Hoogenraad CC, Kapitein LC. Barriers in the brain: resolving dendritic spine morphology and compartmentalization. Front Neuroanat 2014; 8:142. [PMID: 25538570 PMCID: PMC4255500 DOI: 10.3389/fnana.2014.00142] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Accepted: 11/13/2014] [Indexed: 11/23/2022] Open
Abstract
Dendritic spines are micron-sized protrusions that harbor the majority of excitatory synapses in the central nervous system. The head of the spine is connected to the dendritic shaft by a 50-400 nm thin membrane tube, called the spine neck, which has been hypothesized to confine biochemical and electric signals within the spine compartment. Such compartmentalization could minimize interspinal crosstalk and thereby support spine-specific synapse plasticity. However, to what extent compartmentalization is governed by spine morphology, and in particular the diameter of the spine neck, has remained unresolved. Here, we review recent advances in tool development - both experimental and theoretical - that facilitate studying the role of the spine neck in compartmentalization. Special emphasis is given to recent advances in microscopy methods and quantitative modeling applications as we discuss compartmentalization of biochemical signals, membrane receptors and electrical signals in spines. Multidisciplinary approaches should help to answer how dendritic spine architecture affects the cellular and molecular processes required for synapse maintenance and modulation.
Collapse
Affiliation(s)
- Max Adrian
- Cell Biology, Department of Biology, Faculty of Science, Utrecht UniversityUtrecht, Netherlands
| | - Remy Kusters
- Department of Applied Physics, Eindhoven University of TechnologyEindhoven, Netherlands
| | - Corette J. Wierenga
- Cell Biology, Department of Biology, Faculty of Science, Utrecht UniversityUtrecht, Netherlands
| | - Cornelis Storm
- Department of Applied Physics, Eindhoven University of TechnologyEindhoven, Netherlands
- Institute for Complex Molecular Systems, Eindhoven University of TechnologyEindhoven, Netherlands
| | - Casper C. Hoogenraad
- Cell Biology, Department of Biology, Faculty of Science, Utrecht UniversityUtrecht, Netherlands
| | - Lukas C. Kapitein
- Cell Biology, Department of Biology, Faculty of Science, Utrecht UniversityUtrecht, Netherlands
| |
Collapse
|
14
|
Mancuso JJ, Cheng J, Yin Z, Gilliam JC, Xia X, Li X, Wong STC. Integration of multiscale dendritic spine structure and function data into systems biology models. Front Neuroanat 2014; 8:130. [PMID: 25429262 PMCID: PMC4228840 DOI: 10.3389/fnana.2014.00130] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Accepted: 10/22/2014] [Indexed: 12/27/2022] Open
Abstract
Comprising 1011 neurons with 1014 synaptic connections the human brain is the ultimate systems biology puzzle. An increasing body of evidence highlights the observation that changes in brain function, both normal and pathological, consistently correlate with dynamic changes in neuronal anatomy. Anatomical changes occur on a full range of scales from the trafficking of individual proteins, to alterations in synaptic morphology both individually and on a systems level, to reductions in long distance connectivity and brain volume. The major sites of contact for synapsing neurons are dendritic spines, which provide an excellent metric for the number and strength of signaling connections between elements of functional neuronal circuits. A comprehensive model of anatomical changes and their functional consequences would be a holy grail for the field of systems neuroscience but its realization appears far on the horizon. Various imaging technologies have advanced to allow for multi-scale visualization of brain plasticity and pathology, but computational analysis of the big data sets involved forms the bottleneck toward the creation of multiscale models of brain structure and function. While a full accounting of techniques and progress toward a comprehensive model of brain anatomy and function is beyond the scope of this or any other single paper, this review serves to highlight the opportunities for analysis of neuronal spine anatomy and function provided by new imaging technologies and the high-throughput application of older technologies while surveying the strengths and weaknesses of currently available computational analytical tools and room for future improvement.
Collapse
Affiliation(s)
- James J Mancuso
- Department of Systems Medicine and Bioengineering, Houston Methodist Research Institute Houston, TX, USA ; TT and WF Chao Center for Bioinformatics Research and Imaging for Neurosciences, Houston Methodist Research Institute Houston, TX, USA
| | - Jie Cheng
- Department of Systems Medicine and Bioengineering, Houston Methodist Research Institute Houston, TX, USA ; TT and WF Chao Center for Bioinformatics Research and Imaging for Neurosciences, Houston Methodist Research Institute Houston, TX, USA
| | - Zheng Yin
- Department of Systems Medicine and Bioengineering, Houston Methodist Research Institute Houston, TX, USA ; TT and WF Chao Center for Bioinformatics Research and Imaging for Neurosciences, Houston Methodist Research Institute Houston, TX, USA
| | - Jared C Gilliam
- Department of Systems Medicine and Bioengineering, Houston Methodist Research Institute Houston, TX, USA ; TT and WF Chao Center for Bioinformatics Research and Imaging for Neurosciences, Houston Methodist Research Institute Houston, TX, USA
| | - Xiaofeng Xia
- Department of Systems Medicine and Bioengineering, Houston Methodist Research Institute Houston, TX, USA ; TT and WF Chao Center for Bioinformatics Research and Imaging for Neurosciences, Houston Methodist Research Institute Houston, TX, USA
| | - Xuping Li
- Department of Systems Medicine and Bioengineering, Houston Methodist Research Institute Houston, TX, USA ; TT and WF Chao Center for Bioinformatics Research and Imaging for Neurosciences, Houston Methodist Research Institute Houston, TX, USA
| | - Stephen T C Wong
- Department of Systems Medicine and Bioengineering, Houston Methodist Research Institute Houston, TX, USA ; TT and WF Chao Center for Bioinformatics Research and Imaging for Neurosciences, Houston Methodist Research Institute Houston, TX, USA
| |
Collapse
|
15
|
Anwar H, Roome CJ, Nedelescu H, Chen W, Kuhn B, De Schutter E. Dendritic diameters affect the spatial variability of intracellular calcium dynamics in computer models. Front Cell Neurosci 2014; 8:168. [PMID: 25100945 PMCID: PMC4107854 DOI: 10.3389/fncel.2014.00168] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 06/02/2014] [Indexed: 11/13/2022] Open
Abstract
There is growing interest in understanding calcium dynamics in dendrites, both experimentally and computationally. Many processes influence these dynamics, but in dendrites there is a strong contribution of morphology because the peak calcium levels are strongly determined by the surface to volume ratio (SVR) of each branch, which is inversely related to branch diameter. In this study we explore the predicted variance of dendritic calcium concentrations due to local changes in dendrite diameter and how this is affected by the modeling approach used. We investigate this in a model of dendritic calcium spiking in different reconstructions of cerebellar Purkinje cells and in morphological analysis of neocortical and hippocampal pyramidal neurons. We report that many published models neglect diameter-dependent effects on calcium concentration and show how to implement this correctly in the NEURON simulator, both for phenomenological pool based models and for implementations using radial 1D diffusion. More detailed modeling requires simulation of 3D diffusion and we demonstrate that this does not dissipate the local concentration variance due to changes of dendritic diameter. In many cases 1D diffusion of models of calcium buffering give a good approximation provided an increased morphological resolution is implemented.
Collapse
Affiliation(s)
- Haroon Anwar
- Theoretical Neurobiology and Neuroengineering, University of Antwerp Wilrijk, Belgium ; Computational Neuroscience Unit, Okinawa Institute of Science and Technology Onna-Son, Okinawa, Japan
| | - Christopher J Roome
- Optical Neuroimaging Unit, Okinawa Institute of Science and Technology Onna-Son, Okinawa, Japan
| | - Hermina Nedelescu
- Theoretical Neurobiology and Neuroengineering, University of Antwerp Wilrijk, Belgium ; Computational Neuroscience Unit, Okinawa Institute of Science and Technology Onna-Son, Okinawa, Japan
| | - Weiliang Chen
- Computational Neuroscience Unit, Okinawa Institute of Science and Technology Onna-Son, Okinawa, Japan
| | - Bernd Kuhn
- Optical Neuroimaging Unit, Okinawa Institute of Science and Technology Onna-Son, Okinawa, Japan
| | - Erik De Schutter
- Theoretical Neurobiology and Neuroengineering, University of Antwerp Wilrijk, Belgium ; Computational Neuroscience Unit, Okinawa Institute of Science and Technology Onna-Son, Okinawa, Japan
| |
Collapse
|
16
|
Power JM, Sah P. Dendritic spine heterogeneity and calcium dynamics in basolateral amygdala principal neurons. J Neurophysiol 2014; 112:1616-27. [PMID: 24944224 DOI: 10.1152/jn.00770.2013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Glutamatergic synapses on pyramidal neurons are formed on dendritic spines where glutamate activates ionotropic receptors, and calcium influx via N-methyl-d-aspartate receptors leads to a localized rise in spine calcium that is critical for the induction of synaptic plasticity. In the basolateral amygdala, activation of metabotropic receptors is also required for synaptic plasticity and amygdala-dependent learning. Here, using acute brain slices from rats, we show that, in basolateral amygdala principal neurons, high-frequency synaptic stimulation activates metabotropic glutamate receptors and raises spine calcium by releasing calcium from inositol trisphosphate-sensitive calcium stores. This spine calcium release is unevenly distributed, being present in proximal spines, but largely absent in more distal spines. Activation of metabotropic receptors also generated calcium waves that differentially invaded spines as they propagated toward the soma. Dendritic wave invasion was dependent on diffusional coupling between the spine and parent dendrite which was determined by spine neck length, with waves preferentially invading spines with short necks. Spine calcium is a critical trigger for the induction of synaptic plasticity, and our findings suggest that calcium release from inositol trisphosphate-sensitive calcium stores may modulate homosynaptic plasticity through store-release in the spine head, and heterosynaptic plasticity of unstimulated inputs via dendritic calcium wave invasion of the spine head.
Collapse
Affiliation(s)
- John M Power
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, The University of New South Wales, Sydney, New South Wales, Australia; and Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
| | - Pankaj Sah
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
| |
Collapse
|
17
|
Konsolaki E, Skaliora I. Premature Aging Phenotype in Mice Lacking High-Affinity Nicotinic Receptors: Region-Specific Changes in Layer V Pyramidal Cell Morphology. Cereb Cortex 2014; 25:2138-48. [PMID: 24554727 DOI: 10.1093/cercor/bhu019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The mechanisms by which aging leads to alterations in brain structure and cognitive deficits are unclear. Α deficient cholinergic system has been implicated as one of the main factors that could confer a heightened vulnerability to the aging process, and mice lacking high-affinity nicotinic receptors (β2(-/-)) have been proposed as an animal model of accelerated cognitive aging. To date, however, age-related changes in neuronal microanatomy have not been studied in these mice. In the present study, we examine the neuronal structure of yellow fluorescent protein (YFP(+)) layer V neurons in 2 cytoarchitectonically distinct cortical regions in wild-type (WT) and β2(-/-) animals. We find that (1) substantial morphological differences exist between YFP(+) cells of the anterior cingulate cortex (ACC) and primary visual cortex (V1), in both genotypes; (2) in WT animals, ACC cells are more susceptible to aging compared with cells in V1; and (3) β2 deletion is associated with a regionally and temporally specific increase in vulnerability to aging. ACC cells exhibit a prematurely aged phenotype already at 4-6 months, whereas V1 cells are spared in adulthood but strongly affected in old animals. Collectively, our data reveal region-specific synergistic effects of aging and genotype and suggest distinct vulnerabilities in V1 and ACC neurons.
Collapse
Affiliation(s)
- Eleni Konsolaki
- Neurophysiology Laboratory, Division of Developmental Biology, Biomedical Research Foundation of the Academy of Athens, Athens 115 27, Greece
| | - Irini Skaliora
- Neurophysiology Laboratory, Division of Developmental Biology, Biomedical Research Foundation of the Academy of Athens, Athens 115 27, Greece
| |
Collapse
|
18
|
Affiliation(s)
- Rafael Yuste
- HHMI, Departments of Biological Sciences and Neuroscience, and Kavli Institute for Brain Science, Columbia University, New York, NY 10027;
| |
Collapse
|
19
|
Separate Ca2+ sources are buffered by distinct Ca2+ handling systems in aplysia neuroendocrine cells. J Neurosci 2013; 33:6476-91. [PMID: 23575846 DOI: 10.1523/jneurosci.6384-11.2013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Although the contribution of Ca(2+) buffering systems can vary between neuronal types and cellular compartments, it is unknown whether distinct Ca(2+) sources within a neuron have different buffers. As individual Ca(2+) sources can have separate functions, we propose that each is handled by unique systems. Using Aplysia californica bag cell neurons, which initiate reproduction through an afterdischarge involving multiple Ca(2+)-dependent processes, we investigated the role of endoplasmic reticulum (ER) and mitochondrial sequestration, as well as extrusion via the plasma membrane Ca(2+)-ATPase (PMCA) and Na(+)/Ca(2+) exchanger, to the clearance of voltage-gated Ca(2+) influx, Ca(2+)-induced Ca(2+)-release (CICR), and store-operated Ca(2+) influx. Cultured bag cell neurons were filled with the Ca(2+) indicator, fura-PE3, to image Ca(2+) under whole-cell voltage clamp. A 5 Hz, 1 min train of depolarizing voltage steps elicited voltage-gated Ca(2+) influx followed by EGTA-sensitive CICR from the mitochondria. A compartment model of Ca(2+) indicated the effect of EGTA on CICR was due to buffering of released mitochondrial Ca(2+) rather than uptake competition. Removal of voltage-gated Ca(2+) influx was dominated by the mitochondria and PMCA, with no contribution from the Na(+)/Ca(2+) exchanger or sarcoplasmic/endoplasmic Ca(2+)-ATPase (SERCA). In contrast, CICR recovery was slowed by eliminating the Na(+)/Ca(2+) exchanger and PMCA. Last, store-operated influx, evoked by ER depletion, was removed by the SERCA and depended on the mitochondrial membrane potential. Our results demonstrate that distinct buffering systems are dedicated to particular Ca(2+) sources. In general, this may represent a means to differentially regulate Ca(2+)-dependent processes, and for Aplysia, influence how reproductive behavior is triggered.
Collapse
|
20
|
Diffusion and extrusion shape standing calcium gradients during ongoing parallel fiber activity in dendrites of Purkinje neurons. THE CEREBELLUM 2012; 11:694-705. [PMID: 21298581 DOI: 10.1007/s12311-010-0246-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Synaptically induced calcium transients in dendrites of Purkinje neurons (PNs) play a key role in the induction of plasticity in the cerebellar cortex (Ito, Physiol Rev 81:1143-1195, 2001). Long-term depression at parallel fiber-PN synapses can be induced by stimulation paradigms that are associated with long-lasting (>1 min) calcium signals. These signals remain strictly localized (Eilers et al., Learn Mem 3:159-168, 1997), an observation that was rather unexpected, given the high concentration of the mobile endogenous calcium-binding proteins parvalbumin and calbindin in PNs (Fierro and Llano, J Physiol (Lond) 496:617-625, 1996; Kosaka et al., Exp Brain Res 93:483-491, 1993). By combining two-photon calcium imaging experiments in acute slices with numerical computer simulations, we found that significant calcium diffusion out of active branches indeed takes places. It is outweighed, however, by rapid and powerful calcium extrusion along the dendritic shaft. The close interplay of diffusion and extrusion defines the spread of calcium between active and inactive dendritic branches, forming a steep gradient in calcium with drop ranges of ~13 μm (interquartile range, 10-18 μm).
Collapse
|
21
|
Saftenku EÈ. Effects of calretinin on Ca2+ signals in cerebellar granule cells: implications of cooperative Ca2+ binding. THE CEREBELLUM 2012; 11:102-20. [PMID: 21394464 DOI: 10.1007/s12311-011-0263-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Calretinin is thought to be the main endogenous calcium buffer in cerebellar granule cells (GrCs). However, little is known about the impact of cooperative Ca(2+) binding to calretinin on highly localized and more global (regional) Ca(2+) signals in these cells. Using numerical simulations, we show that an essential property of calretinin is a delayed equilibration with Ca(2+). Therefore, the amount of Ca(2+), which calretinin can accumulate with respect to equilibrium levels, depends on stimulus conditions. Based on our simulations of buffered Ca(2+) diffusion near a single Ca(2+) channel or a large cluster of Ca(2+) channels and previous experimental findings that 150 μM 1,2-bis(o-aminophenoxy) ethane-N, N, N', N'-tetraacetic acid (BAPTA) and endogenous calretinin have similar effects on GrC excitability, we estimated the concentration of mobile calretinin in GrCs in the range of 0.7-1.2 mM. Our results suggest that this estimate can provide a starting point for further analysis. We find that calretinin prominently reduces the action potential associated increase in cytosolic free Ca(2+) concentration ([Ca(2+)]( i )) even at a distance of 30 nm from a single Ca(2+) channel. In spite of a buildup of residual Ca(2+), it maintains almost constant maximal [Ca(2+)]( i ) levels during repetitive channel openings with a frequency less than 80 Hz. This occurs because of accelerated Ca(2+) binding as calretinin binds more Ca(2+). Unlike the buffering of high Ca(2+) levels within Ca(2+) nano/microdomains sensed by large conductance Ca(2+)-activated K(+) channels, the buffering of regional Ca(2+) signals by calretinin can never be mimicked by certain concentration of BAPTA under all different experimental conditions.
Collapse
Affiliation(s)
- Elena È Saftenku
- Department of General Physiology of Nervous System, A. A. Bogomoletz Institute of Physiology, Bogomoletz St., 4, Kyiv 01024, Ukraine.
| |
Collapse
|
22
|
Schmidt H. Three functional facets of calbindin D-28k. Front Mol Neurosci 2012; 5:25. [PMID: 22435048 PMCID: PMC3304297 DOI: 10.3389/fnmol.2012.00025] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Accepted: 02/14/2012] [Indexed: 11/13/2022] Open
Abstract
Many neurons of the vertebrate central nervous system (CNS) express the Ca2+ binding protein calbindin D-28k (CB), including important projection neurons like cerebellar Purkinje cells but also neocortical interneurons. CB has moderate cytoplasmic mobility and comprises at least four EF-hands that function in Ca2+ binding with rapid to intermediate kinetics and affinity. Classically it was viewed as a pure Ca2+ buffer important for neuronal survival. This view was extended by showing that CB is a critical determinant in the control of synaptic Ca2+ dynamics, presumably with strong impact on plasticity and information processing. Already 30 years ago, in vitro studies suggested that CB could have an additional Ca2+ sensor function, like its prominent acquaintance calmodulin (CaM). More recent work substantiated this hypothesis, revealing direct CB interactions with several target proteins. Different from a classical sensor, however, CB appears to interact with its targets both, in its Ca2+-loaded and Ca2+-free forms. Finally, CB has been shown to be involved in buffered transport of Ca2+, in neurons but also in kidney. Thus, CB serves a threefold function as buffer, transporter and likely as a non-canonical sensor.
Collapse
Affiliation(s)
- Hartmut Schmidt
- Medical Faculty, Carl-Ludwig Institute for Physiology, University of Leipzig Leipzig, Germany.
| |
Collapse
|
23
|
Combined computational and experimental approaches to understanding the Ca(2+) regulatory network in neurons. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:569-601. [PMID: 22453961 DOI: 10.1007/978-94-007-2888-2_26] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Ca(2+) is a ubiquitous signaling ion that regulates a variety of neuronal functions by binding to and altering the state of effector proteins. Spatial relationships and temporal dynamics of Ca(2+) elevations determine many cellular responses of neurons to chemical and electrical stimulation. There is a wealth of information regarding the properties and distribution of Ca(2+) channels, pumps, exchangers, and buffers that participate in Ca(2+) regulation. At the same time, new imaging techniques permit characterization of evoked Ca(2+) signals with increasing spatial and temporal resolution. However, understanding the mechanistic link between functional properties of Ca(2+) handling proteins and the stimulus-evoked Ca(2+) signals they orchestrate requires consideration of the way Ca(2+) handling mechanisms operate together as a system in native cells. A wide array of biophysical modeling approaches is available for studying this problem and can be used in a variety of ways. Models can be useful to explain the behavior of complex systems, to evaluate the role of individual Ca(2+) handling mechanisms, to extract valuable parameters, and to generate predictions that can be validated experimentally. In this review, we discuss recent advances in understanding the underlying mechanisms of Ca(2+) signaling in neurons via mathematical modeling. We emphasize the value of developing realistic models based on experimentally validated descriptions of Ca(2+) transport and buffering that can be tested and refined through new experiments to develop increasingly accurate biophysical descriptions of Ca(2+) signaling in neurons.
Collapse
|
24
|
|
25
|
Tan AM, Chang YW, Zhao P, Hains BC, Waxman SG. Rac1-regulated dendritic spine remodeling contributes to neuropathic pain after peripheral nerve injury. Exp Neurol 2011; 232:222-33. [DOI: 10.1016/j.expneurol.2011.08.028] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Revised: 08/11/2011] [Accepted: 08/18/2011] [Indexed: 10/17/2022]
|
26
|
Abstract
Dendritic spines receive most excitatory connections in pyramidal cells and many other principal neurons. But why do neurons use spines, when they could accommodate excitatory contacts directly on their dendritic shafts? One suggestion is that spines serve to connect with passing axons, thus increasing the connectivity of the dendrites. Another hypothesis is that spines are biochemical compartments that enable input-specific synaptic plasticity. A third possibility is that spines have an electrical role, filtering synaptic potentials and electrically isolating inputs from each other. In this review, I argue that, when viewed from the perspective of the circuit function, these three functions dovetail with one another to achieve a single overarching goal: to implement a distributed circuit with widespread connectivity. Spines would endow these circuits with nonsaturating, linear integration and input-specific learning rules, which would enable them to function as neural networks, with emergent encoding and processing of information.
Collapse
Affiliation(s)
- Rafael Yuste
- HHMI, Department Biological Sciences, Columbia University, New York, NY 10027, USA.
| |
Collapse
|
27
|
Cho HJ, Chun HJ, Kim ES, Cho BR. Multiphoton microscopy: An introduction to gastroenterologists. World J Gastroenterol 2011; 17:4456-60. [PMID: 22110275 PMCID: PMC3218135 DOI: 10.3748/wjg.v17.i40.4456] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Revised: 03/02/2011] [Accepted: 03/09/2011] [Indexed: 02/06/2023] Open
Abstract
Multiphoton microscopy, relying on the simultaneous absorption of two or more photons by a fluorophore, has come to occupy a prominent place in modern biomedical research with its ability to allow real-time observation of a single cell and molecules in intact tissues. Multiphoton microscopy exhibits nonlinear optical contrast properties, which can make it possible to provide an exceptionally large depth penetration with less phototoxicity. This system becomes more and more an inspiring tool for a non-invasive imaging system to realize “optical biopsy” and to examine the functions of living cells. In this review, we briefly present the physical principles and properties of multiphoton microscopy as well as the current applications in biological fields. In addition, we address what we see as the future potential of multiphoton microscopy for gastroenterologic research.
Collapse
|
28
|
Jung CKE, Fuhrmann M, Honarnejad K, Van Leuven F, Herms J. Role of presenilin1 in structural plasticity of cortical dendritic spines in vivo. J Neurochem 2011; 119:1064-73. [DOI: 10.1111/j.1471-4159.2011.07503.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
|
29
|
Verhoog MB, Mansvelder HD. Presynaptic ionotropic receptors controlling and modulating the rules for spike timing-dependent plasticity. Neural Plast 2011; 2011:870763. [PMID: 21941664 PMCID: PMC3173883 DOI: 10.1155/2011/870763] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Accepted: 07/15/2011] [Indexed: 11/18/2022] Open
Abstract
Throughout life, activity-dependent changes in neuronal connection strength enable the brain to refine neural circuits and learn based on experience. In line with predictions made by Hebb, synapse strength can be modified depending on the millisecond timing of action potential firing (STDP). The sign of synaptic plasticity depends on the spike order of presynaptic and postsynaptic neurons. Ionotropic neurotransmitter receptors, such as NMDA receptors and nicotinic acetylcholine receptors, are intimately involved in setting the rules for synaptic strengthening and weakening. In addition, timing rules for STDP within synapses are not fixed. They can be altered by activation of ionotropic receptors located at, or close to, synapses. Here, we will highlight studies that uncovered how network actions control and modulate timing rules for STDP by activating presynaptic ionotropic receptors. Furthermore, we will discuss how interaction between different types of ionotropic receptors may create "timing" windows during which particular timing rules lead to synaptic changes.
Collapse
Affiliation(s)
- Matthijs B. Verhoog
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research (CNCR), Neuroscience Campus Amsterdam, VU University Amsterdam, Room C-440, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands
| | - Huibert D. Mansvelder
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research (CNCR), Neuroscience Campus Amsterdam, VU University Amsterdam, Room C-440, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands
| |
Collapse
|
30
|
Tan AM, Waxman SG. Spinal cord injury, dendritic spine remodeling, and spinal memory mechanisms. Exp Neurol 2011; 235:142-51. [PMID: 21925174 DOI: 10.1016/j.expneurol.2011.08.026] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Revised: 08/17/2011] [Accepted: 08/25/2011] [Indexed: 01/27/2023]
Abstract
Spinal cord injury (SCI) often results in the development of neuropathic pain, which can persist for months and years after injury. Although many aberrant changes to sensory processing contribute to the development of chronic pain, emerging evidence demonstrates that mechanisms similar to those underlying classical learning and memory can contribute to central sensitization, a phenomenon of amplified responsiveness to stimuli in nociceptive dorsal horn neurons. Notably, dendritic spines have emerged as major players in learning and memory, providing a structural substrate for how the nervous system modifies connections to form and store information. Until now, most information regarding dendritic spines has been obtained from studies in the brain. Recent experimental data in the spinal cord, however, demonstrate that Rac1-regulated dendritic spine remodeling occurs on second-order wide dynamic range neurons and accompanies neuropathic pain after SCI. Thus, SCI-induced synaptic potentiation engages a putative spinal memory mechanism. A compelling, novel possibility for pain research is that a synaptic model of long-term memory storage could explain the persistent nature of neuropathic pain. Such a conceptual bridge between pain and memory could guide the development of more effective strategies for treatment of chronic pain after injury to the nervous system.
Collapse
Affiliation(s)
- Andrew M Tan
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, USA
| | | |
Collapse
|
31
|
Gilbert MT, Soderstrom K. Late-postnatal cannabinoid exposure persistently elevates dendritic spine densities in area X and HVC song regions of zebra finch telencephalon. Brain Res 2011; 1405:23-30. [PMID: 21737064 DOI: 10.1016/j.brainres.2011.06.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Revised: 06/01/2011] [Accepted: 06/05/2011] [Indexed: 10/18/2022]
Abstract
Centrally acting cannabinoids are well known for their ability to impair functions associated with both learning and memory but appreciation of the physiological mechanisms underlying these actions, particularly those that persist, remains incomplete. Our earlier studies have shown that song stereotypy is persistently reduced in male zebra finches that have been developmentally exposed to cannabinoids. In the present work, we examined the extent to which changes in neuronal morphology (dendritic spine densities and soma size) within brain regions associated with zebra finch vocal learning are affected by late-postnatal cannabinoid agonist exposure. We found that daily treatment with the cannabinoid agonist WIN55212-2 (WIN, 1mg/kg IM) is associated with 27% and 31% elevations in dendritic spine densities in the song regions Area X and HVC, respectively. We also found an overall increase in cell diameter within HVC. Changes in dendritic spine densities were only produced following developmental exposure; treatments given to adults that had completed vocal learning were not effective. These findings have important implications for understanding how repeated cannabinoid exposure can produce significant, lasting alteration of brain morphology, which may contribute to altered development and behavior.
Collapse
Affiliation(s)
- Marcoita T Gilbert
- Department of Pharmacology and Toxicology, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA
| | | |
Collapse
|
32
|
Sullivan KD, Brown EB. Multiphoton fluorescence recovery after photobleaching in bounded systems. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 83:051916. [PMID: 21728580 PMCID: PMC3413246 DOI: 10.1103/physreve.83.051916] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Revised: 01/17/2011] [Indexed: 05/31/2023]
Abstract
Multiphoton fluorescence recovery after photobleaching (MP-FRAP) is a laser microscopy technique used to measure diffusion coefficients of macromolecules in biological systems. The three-dimensional resolution and superior depth penetration within scattering samples offered by MP-FRAP make it an important tool for investigating both in vitro and in vivo systems. However, biological systems frequently confine diffusion within solid barriers, and to date the effect of such barriers on the measurement of absolute diffusion coefficients via MP-FRAP has not been studied. We have used Monte Carlo simulations of diffusion and MP-FRAP to understand the effect of barriers of varying geometries and positions relative to the two-photon focal volume. Furthermore, we supply ranges of barrier positions within which MP-FRAP can confidently be employed to measure accurate diffusion coefficients. Finally, we produce two new MP-FRAP models that can produce accurate diffusion coefficients in the presence of a single plane boundary or parallel infinite plane boundaries positioned parallel to the optical axis, up to the resolution limit of the multiphoton laser scanning microscope.
Collapse
Affiliation(s)
- Kelley D. Sullivan
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
| | - Edward B. Brown
- Department of Biomedical Engineering, University of Rochester, Rochester, New York 14627, USA
| |
Collapse
|
33
|
Calcium dynamics in dendritic spines: a link to structural plasticity. Math Biosci 2011; 230:55-66. [PMID: 21295598 DOI: 10.1016/j.mbs.2011.01.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Revised: 01/15/2011] [Accepted: 01/19/2011] [Indexed: 01/31/2023]
Abstract
Calcium signals evoked either by action potential or by synaptic activity play a crucial role for the synaptic plasticity within an individual spine. Because of the small size of spine and the indicators commonly used to measure spine calcium activity, calcium function can be severely disrupted. Therefore, it is very difficult to explain the exact relationship between spine geometry and spine calcium dynamics. Recently, it has been suggested that the medium range of calcium which induces long term potentiation leads to the structural stability stage of spines, while very low or very high amount of calcium leads to the long term depression stage which results in shortening and eventually pruning of spines. Here we propose a physiologically realistic computational model to examine the role of calcium and the mechanisms that govern its regulation in the spine morphology. Calcium enters into spine head through NMDA and AMPA channels and is regulated by internal stores. Contribution of this calcium in the induction of long term potentiation and long term depression is also discussed. Further it has also been predicted that the presence of internal stores depletes the total calcium accumulation in cytosol which is in agreement with the recent experimental and theoretical studies.
Collapse
|
34
|
Low-threshold Ca2+ current amplifies distal dendritic signaling in thalamic reticular neurons. J Neurosci 2010; 30:15419-29. [PMID: 21084598 DOI: 10.1523/jneurosci.3636-10.2010] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The low-threshold transient calcium current (I(T)) plays a critical role in modulating the firing behavior of thalamic neurons; however, the role of I(T) in the integration of afferent information within the thalamus is virtually unknown. We have used two-photon laser scanning microscopy coupled with whole-cell recordings to examine calcium dynamics in the neurons of the strategically located thalamic reticular nucleus (TRN). We now report that a single somatic burst discharge evokes large-magnitude calcium responses, via I(T), in distal TRN dendrites. The magnitude of the burst-evoked calcium response was larger than those observed in thalamocortical projection neurons under the same conditions. We also demonstrate that direct stimulation of distal TRN dendrites, via focal glutamate application and synaptic activation, can locally activate distal I(T), producing a large distal calcium response independent of the soma/proximal dendrites. These findings strongly suggest that distally located I(T) may function to amplify afferent inputs. Boosting the magnitude ensures integration at the somatic level by compensating for attenuation that would normally occur attributable to passive cable properties. Considering the functional architecture of the TRN, elongated nature of their dendrites, and robust dendritic signaling, these distal dendrites could serve as sites of intense intra-modal/cross-modal integration and/or top-down modulation, leading to focused thalamocortical communication.
Collapse
|
35
|
Manninen T, Hituri K, Kotaleski JH, Blackwell KT, Linne ML. Postsynaptic signal transduction models for long-term potentiation and depression. Front Comput Neurosci 2010; 4:152. [PMID: 21188161 PMCID: PMC3006457 DOI: 10.3389/fncom.2010.00152] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Accepted: 11/22/2010] [Indexed: 01/01/2023] Open
Abstract
More than a hundred biochemical species, activated by neurotransmitters binding to transmembrane receptors, are important in long-term potentiation (LTP) and long-term depression (LTD). To investigate which species and interactions are critical for synaptic plasticity, many computational postsynaptic signal transduction models have been developed. The models range from simple models with a single reversible reaction to detailed models with several hundred kinetic reactions. In this study, more than a hundred models are reviewed, and their features are compared and contrasted so that similarities and differences are more readily apparent. The models are classified according to the type of synaptic plasticity that is modeled (LTP or LTD) and whether they include diffusion or electrophysiological phenomena. Other characteristics that discriminate the models include the phase of synaptic plasticity modeled (induction, expression, or maintenance) and the simulation method used (deterministic or stochastic). We find that models are becoming increasingly sophisticated, by including stochastic properties, integrating with electrophysiological properties of entire neurons, or incorporating diffusion of signaling molecules. Simpler models continue to be developed because they are computationally efficient and allow theoretical analysis. The more complex models permit investigation of mechanisms underlying specific properties and experimental verification of model predictions. Nonetheless, it is difficult to fully comprehend the evolution of these models because (1) several models are not described in detail in the publications, (2) only a few models are provided in existing model databases, and (3) comparison to previous models is lacking. We conclude that the value of these models for understanding molecular mechanisms of synaptic plasticity is increasing and will be enhanced further with more complete descriptions and sharing of the published models.
Collapse
Affiliation(s)
- Tiina Manninen
- Department of Signal Processing, Tampere University of Technology Tampere, Finland
| | | | | | | | | |
Collapse
|
36
|
Michaelsen K, Lohmann C. Calcium dynamics at developing synapses: mechanisms and functions. Eur J Neurosci 2010; 32:218-23. [DOI: 10.1111/j.1460-9568.2010.07341.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
37
|
Andermann ML, Kerlin AM, Reid RC. Chronic cellular imaging of mouse visual cortex during operant behavior and passive viewing. Front Cell Neurosci 2010; 4:3. [PMID: 20407583 PMCID: PMC2854571 DOI: 10.3389/fncel.2010.00003] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Accepted: 02/18/2010] [Indexed: 11/24/2022] Open
Abstract
Nearby neurons in mammalian neocortex demonstrate a great diversity of cell types and connectivity patterns. The importance of this diversity for computation is not understood. While extracellular recording studies in visual cortex have provided a particularly rich description of behavioral modulation of neural activity, new methods are needed to dissect the contribution of specific circuit elements in guiding visual perception. Here, we describe a method for three-dimensional cellular imaging of neural activity in the awake mouse visual cortex during active discrimination and passive viewing of visual stimuli. Head-fixed mice demonstrated robust discrimination for many hundred trials per day after initial task acquisition. To record from multiple neurons during operant behavior with single-trial resolution and minimal artifacts, we built a sensitive microscope for two-photon calcium imaging, capable of rapid tracking of neurons in three dimensions. We demonstrate stable recordings of cellular calcium activity during discrimination behavior across hours, days, and weeks, using both synthetic and genetically encoded calcium indicators. When combined with molecular and genetic technologies in mice (e.g., cell-type specific transgenic labeling), this approach allows the identification of neuronal classes in vivo. Physiological measurements from distinct classes of neighboring neurons will enrich our understanding of the coordinated roles of diverse elements of cortical microcircuits in guiding sensory perception and perceptual learning. Further, our method provides a high-throughput, chronic in vivo assay of behavioral influences on cellular activity that is applicable to a wide range of mouse models of neurologic disease.
Collapse
Affiliation(s)
- Mark L Andermann
- Department of Neurobiology, Harvard Medical School Boston, MA, USA
| | | | | |
Collapse
|
38
|
Dendritic vulnerability in neurodegenerative disease: insights from analyses of cortical pyramidal neurons in transgenic mouse models. Brain Struct Funct 2010; 214:181-99. [PMID: 20177698 DOI: 10.1007/s00429-010-0244-2] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Accepted: 02/05/2010] [Indexed: 12/27/2022]
Abstract
In neurodegenerative disorders, such as Alzheimer's disease, neuronal dendrites and dendritic spines undergo significant pathological changes. Because of the determinant role of these highly dynamic structures in signaling by individual neurons and ultimately in the functionality of neuronal networks that mediate cognitive functions, a detailed understanding of these changes is of paramount importance. Mutant murine models, such as the Tg2576 APP mutant mouse and the rTg4510 tau mutant mouse have been developed to provide insight into pathogenesis involving the abnormal production and aggregation of amyloid and tau proteins, because of the key role that these proteins play in neurodegenerative disease. This review showcases the multidimensional approach taken by our collaborative group to increase understanding of pathological mechanisms in neurodegenerative disease using these mouse models. This approach includes analyses of empirical 3D morphological and electrophysiological data acquired from frontal cortical pyramidal neurons using confocal laser scanning microscopy and whole-cell patch-clamp recording techniques, combined with computational modeling methodologies. These collaborative studies are designed to shed insight on the repercussions of dystrophic changes in neocortical neurons, define the cellular phenotype of differential neuronal vulnerability in relevant models of neurodegenerative disease, and provide a basis upon which to develop meaningful therapeutic strategies aimed at preventing, reversing, or compensating for neurodegenerative changes in dementia.
Collapse
|
39
|
Krieger P. Experience-dependent increase in spine calcium evoked by backpropagating action potentials in layer 2/3 pyramidal neurons in rat somatosensory cortex. Eur J Neurosci 2009; 30:1870-7. [PMID: 19912332 DOI: 10.1111/j.1460-9568.2009.06977.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
In spines on basal dendrites of layer 2/3 pyramidal neurons in somatosensory barrel cortex, calcium transients evoked by back-propagating action potentials (bAPs) were investigated (i) along the length of the basal dendrite, (ii) with postnatal development and (iii) with sensory deprivation during postnatal development. Layer 2/3 pyramidal neurons were investigated at three different ages. At all ages [postnatal day (P)8, P14, P21] the bAP-evoked calcium transient amplitude increased with distance from the soma with a peak at around 50 microm, followed by a gradual decline in amplitude. The effect of sensory deprivation on the bAP-evoked calcium was investigated using two different protocols. When all whiskers on one side of the rat snout were trimmed daily from P8 to P20-24 there was no difference in the bAP-evoked calcium transient between cells in the contralateral hemisphere, lacking sensory input from the whisker, and cells in the ipsilateral barrel cortex, with intact whisker activation. When, however, only the D-row whiskers on one side were trimmed the distribution of bAP-evoked calcium transients in spines was shifted towards larger amplitudes in cells located in the deprived D-column. In conclusion, (i) the bAP-evoked calcium transient gradient along the dendrite length is established at P8, (ii) the calcium transient increases in amplitude with age and (iii) this increase is enhanced in layer 2/3 pyramidal neurons located in a sensory-deprived barrel column that is bordered by non-deprived barrel columns.
Collapse
Affiliation(s)
- Patrik Krieger
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
| |
Collapse
|
40
|
Yu LMY, Goda Y. Dendritic signalling and homeostatic adaptation. Curr Opin Neurobiol 2009; 19:327-35. [PMID: 19640698 DOI: 10.1016/j.conb.2009.07.002] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2009] [Revised: 05/29/2009] [Accepted: 07/02/2009] [Indexed: 11/19/2022]
Abstract
Homeostatic plasticity mechanisms are employed by neurons to alter membrane excitability and synaptic strength to adapt to changes in network activity. Recent studies suggest that homeostatic processes can occur not only on a global scale but also within specific neuronal subcompartments, involving a wide range of molecules and signalling pathways. Here, we review new findings into homeostatic adaptation within dendrites and discuss potential signalling components and mechanisms that may mediate this local form of regulation.
Collapse
Affiliation(s)
- Lily M Y Yu
- MRC Laboratory for Molecular Cell Biology and MRC Cell Biology Unit, Department of Neuroscience, Physiology & Pharmacology, University College London, London, UK
| | | |
Collapse
|
41
|
Spine neck geometry determines spino-dendritic cross-talk in the presence of mobile endogenous calcium binding proteins. J Comput Neurosci 2009; 27:229-43. [PMID: 19229604 DOI: 10.1007/s10827-009-0139-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2008] [Revised: 01/27/2009] [Accepted: 01/29/2009] [Indexed: 01/23/2023]
Abstract
Dendritic spines are thought to compartmentalize second messengers like Ca2+. The notion of isolated spine signaling, however, was challenged by the recent finding that under certain conditions mobile endogenous Ca(2+)-binding proteins may break the spine limit and lead to activation of Ca(2+)-dependent dendritic signaling cascades. Since the size of spines is variable, the spine neck may be an important regulator of this spino-dendritic crosstalk. We tested this hypothesis by using an experimentally defined, kinetic computer model in which spines of Purkinje neurons were coupled to their parent dendrite by necks of variable geometry. We show that Ca2+ signaling and calmodulin activation in spines with long necks is essentially isolated from the dendrite, while stubby spines show a strong coupling with their dendrite, mediated particularly by calbindin D28k. We conclude that the spine neck geometry, in close interplay with mobile Ca(2+)-binding proteins, regulates the spino-dendritic crosstalk.
Collapse
|
42
|
Neuropathic pain memory is maintained by Rac1-regulated dendritic spine remodeling after spinal cord injury. J Neurosci 2009; 28:13173-83. [PMID: 19052208 DOI: 10.1523/jneurosci.3142-08.2008] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Localized increases in synaptic strength constitute a synaptic basis for learning and memory in the CNS and may also contribute to the maintenance of neuropathic pain after spinal cord injury (SCI) through the de novo formation or elaboration of postsynaptic dendritic structures. To determine whether SCI-induced dendritic spine remodeling contributes to neuronal hyperexcitability and neuropathic pain, we analyzed spine morphometry, localization, and functional influence in dorsal horn (DH) neurons in adult rats 1 month after sham surgery, contusion SCI, and SCI treated with a selective inhibitor of Rac1 activation, NSC23766. After SCI, DH neurons located in lamina IV-V exhibited increased spine density, redistributed spines, and mature spines compared with control neurons, which was associated with enhancement of EPSCs in computer simulations and hyperexcitable responsiveness to innocuous and noxious peripheral stimuli in unit recordings in vivo. SCI animals also exhibited symptoms of tactile allodynia and thermal hyperalgesia. Inhibition of the small GTP-binding protein Rac1 ameliorated post-SCI changes in spine morphology, attenuated injury-induced hyperexcitability of wide-dynamic range neurons, and progressively increased pain thresholds over a 3 d period. This suggests that Rac1 is an important intracellular signaling molecule involved in a spinal dendritic spine pathology associated with chronic neuropathic pain after SCI. Our report provides robust evidence for a novel conceptual bridge between learning and memory on the one hand, and neuropathic pain on the other.
Collapse
|
43
|
Computational study of non-homogeneous distribution of Ca(2+) handling systems in cerebellar granule cells. J Theor Biol 2008; 257:228-44. [PMID: 19121636 DOI: 10.1016/j.jtbi.2008.12.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Revised: 10/01/2008] [Accepted: 12/01/2008] [Indexed: 11/21/2022]
Abstract
The spatiotemporal distribution of cytosolic free calcium concentration ([Ca(2+)](i)) in cerebellar granule cells (GrCs) is thought to be critical in defining the occurrence and direction of long-term changes in synaptic strength at cerebellar mossy fiber-GrC synapses. Despite this, the mechanisms responsible for shaping Ca(2+) transients in GrCs are not well understood. To investigate the interplay between Ca(2+) entry, extrusion, buffering and dendritic morphology in shaping Ca(2+) elevations in GrCs, we developed a model of Ca(2+) regulation in these cells and examined the requirements for reproducing fluorescence responses to depolarization and synaptic stimulation previously described in the literature. Two conclusions can be drawn from our simulation results. First, a significant progressive decrease in the amplitudes of depolarization-evoked fluorescence transients from the dendritic endings (digits) toward the soma of GrCs, can be reproduced in the model only if the density of Ca(2+) channels is considerably higher or the concentration of endogenous buffers is much lower in the digits than in the parent dendrites. In contrast, heterogeneities in the distribution of Ca(2+) pumps or in cytosolic fractional volume cannot account for the formation of [Ca(2+)](i) gradients in GrCs. Second, much lower amplitudes of fluorescence transients induced by depolarization and synaptic stimulation than expected from typical measurements of Ca(2+) and NMDA receptor-mediated currents can be reconciled with a pronounced slowing of the decay of fluorescence responses in the digits of GrCs after introducing a high-affinity Ca(2+) indicator if a high-capacity immobile Ca(2+) buffer (presumably plasma membrane-associated) is suggested to be present in the soma and apical part of digits. Mitochondria also are likely to modulate synaptically evoked Ca(2+) responses in GrCs. The alternative hypotheses are thoroughly discussed and research avenues for their testing in future experiments are proposed.
Collapse
|
44
|
Penzes P, Cahill ME, Jones KA, Srivastava DP. Convergent CaMK and RacGEF signals control dendritic structure and function. Trends Cell Biol 2008; 18:405-13. [PMID: 18701290 DOI: 10.1016/j.tcb.2008.07.002] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Revised: 06/30/2008] [Accepted: 07/02/2008] [Indexed: 12/25/2022]
Abstract
Structural plasticity of excitatory synapses is a vital component of neuronal development, synaptic plasticity and behavior, and its malfunction underlies many neurodevelopmental and psychiatric disorders. However, the molecular mechanisms that control dendritic spine morphogenesis have only recently emerged. We summarize recent work that has revealed an important connection between calcium/calmodulin-dependent kinases (CaMKs) and guanine-nucleotide-exchange factors (GEFs) that activate the small GTPase Rac (RacGEFs) in controlling dendritic spine morphogenesis. These two groups of molecules function in neurons as a unique signaling cassette that transduces calcium influx into small GTPase activity and, thence, actin reorganization and spine morphogenesis. Through this pathway, CaMKs and RacGEFs amplify calcium signals and translate them into spatially and temporally regulated structural remodeling of dendritic spines.
Collapse
Affiliation(s)
- Peter Penzes
- Department of Physiology, Northwestern University Feinberg School of Medicine, 303 E. Chicago Avenue, Chicago, IL 60611, USA.
| | | | | | | |
Collapse
|
45
|
Sjöström PJ, Rancz EA, Roth A, Häusser M. Dendritic excitability and synaptic plasticity. Physiol Rev 2008; 88:769-840. [PMID: 18391179 DOI: 10.1152/physrev.00016.2007] [Citation(s) in RCA: 418] [Impact Index Per Article: 26.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Most synaptic inputs are made onto the dendritic tree. Recent work has shown that dendrites play an active role in transforming synaptic input into neuronal output and in defining the relationships between active synapses. In this review, we discuss how these dendritic properties influence the rules governing the induction of synaptic plasticity. We argue that the location of synapses in the dendritic tree, and the type of dendritic excitability associated with each synapse, play decisive roles in determining the plastic properties of that synapse. Furthermore, since the electrical properties of the dendritic tree are not static, but can be altered by neuromodulators and by synaptic activity itself, we discuss how learning rules may be dynamically shaped by tuning dendritic function. We conclude by describing how this reciprocal relationship between plasticity of dendritic excitability and synaptic plasticity has changed our view of information processing and memory storage in neuronal networks.
Collapse
Affiliation(s)
- P Jesper Sjöström
- Wolfson Institute for Biomedical Research and Department of Physiology, University College London, London, United Kingdom
| | | | | | | |
Collapse
|
46
|
Keller DX, Franks KM, Bartol TM, Sejnowski TJ. Calmodulin activation by calcium transients in the postsynaptic density of dendritic spines. PLoS One 2008; 3:e2045. [PMID: 18446197 PMCID: PMC2312328 DOI: 10.1371/journal.pone.0002045] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2008] [Accepted: 03/12/2008] [Indexed: 11/19/2022] Open
Abstract
The entry of calcium into dendritic spines can trigger a sequence of biochemical reactions that begins with the activation of calmodulin (CaM) and ends with long-term changes to synaptic strengths. The degree of activation of CaM can depend on highly local elevations in the concentration of calcium and the duration of transient increases in calcium concentration. Accurate measurement of these local changes in calcium is difficult because the spaces are so small and the numbers of molecules are so low. We have therefore developed a Monte Carlo model of intracellular calcium dynamics within the spine that included calcium binding proteins, calcium transporters and ion channels activated by voltage and glutamate binding. The model reproduced optical recordings using calcium indicator dyes and showed that without the dye the free intracellular calcium concentration transient was much higher than predicted from the fluorescent signal. Excitatory postsynaptic potentials induced large, long-lasting calcium gradients across the postsynaptic density, which activated CaM. When glutamate was released at the synapse 10 ms before an action potential occurred, simulating activity patterns that strengthen hippocampal synapses, the calcium gradient and activation of CaM in the postsynaptic density were much greater than when the order was reversed, a condition that decreases synaptic strengths, suggesting a possible mechanism underlying the induction of long-term changes in synaptic strength. The spatial and temporal mechanisms for selectivity in CaM activation demonstrated here could be used in other signaling pathways.
Collapse
Affiliation(s)
- Daniel X Keller
- The Salk Institute, Computational Neurobiology Laboratory, and Howard Hughes Medical Institute, La Jolla, California, United States of America.
| | | | | | | |
Collapse
|
47
|
Rodriguez A, Ehlenberger DB, Dickstein DL, Hof PR, Wearne SL. Automated three-dimensional detection and shape classification of dendritic spines from fluorescence microscopy images. PLoS One 2008; 3:e1997. [PMID: 18431482 PMCID: PMC2292261 DOI: 10.1371/journal.pone.0001997] [Citation(s) in RCA: 437] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2007] [Accepted: 03/04/2008] [Indexed: 11/18/2022] Open
Abstract
A fundamental challenge in understanding how dendritic spine morphology controls learning and memory has been quantifying three-dimensional (3D) spine shapes with sufficient precision to distinguish morphologic types, and sufficient throughput for robust statistical analysis. The necessity to analyze large volumetric data sets accurately, efficiently, and in true 3D has been a major bottleneck in deriving reliable relationships between altered neuronal function and changes in spine morphology. We introduce a novel system for automated detection, shape analysis and classification of dendritic spines from laser scanning microscopy (LSM) images that directly addresses these limitations. The system is more accurate, and at least an order of magnitude faster, than existing technologies. By operating fully in 3D the algorithm resolves spines that are undetectable with standard two-dimensional (2D) tools. Adaptive local thresholding, voxel clustering and Rayburst Sampling generate a profile of diameter estimates used to classify spines into morphologic types, while minimizing optical smear and quantization artifacts. The technique opens new horizons on the objective evaluation of spine changes with synaptic plasticity, normal development and aging, and with neurodegenerative disorders that impair cognitive function.
Collapse
Affiliation(s)
- Alfredo Rodriguez
- Department of Neuroscience, Mount Sinai School of Medicine, New York, New York, United States of America
- Laboratory of Biomathematics, Mount Sinai School of Medicine, New York, New York, United States of America
- Computational Neurobiology and Imaging Center, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Douglas B. Ehlenberger
- Department of Neuroscience, Mount Sinai School of Medicine, New York, New York, United States of America
- Laboratory of Biomathematics, Mount Sinai School of Medicine, New York, New York, United States of America
- Computational Neurobiology and Imaging Center, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Dara L. Dickstein
- Department of Neuroscience, Mount Sinai School of Medicine, New York, New York, United States of America
- Computational Neurobiology and Imaging Center, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Patrick R. Hof
- Department of Neuroscience, Mount Sinai School of Medicine, New York, New York, United States of America
- Computational Neurobiology and Imaging Center, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Susan L. Wearne
- Department of Neuroscience, Mount Sinai School of Medicine, New York, New York, United States of America
- Laboratory of Biomathematics, Mount Sinai School of Medicine, New York, New York, United States of America
- Computational Neurobiology and Imaging Center, Mount Sinai School of Medicine, New York, New York, United States of America
- * E-mail:
| |
Collapse
|
48
|
Cornelisse LN, van Elburg RAJ, Meredith RM, Yuste R, Mansvelder HD. High speed two-photon imaging of calcium dynamics in dendritic spines: consequences for spine calcium kinetics and buffer capacity. PLoS One 2007; 2:e1073. [PMID: 17957255 PMCID: PMC2034355 DOI: 10.1371/journal.pone.0001073] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2007] [Accepted: 10/04/2007] [Indexed: 11/29/2022] Open
Abstract
Rapid calcium concentration changes in postsynaptic structures are crucial for synaptic plasticity. Thus far, the determinants of postsynaptic calcium dynamics have been studied predominantly based on the decay kinetics of calcium transients. Calcium rise times in spines in response to single action potentials (AP) are almost never measured due to technical limitations, but they could be crucial for synaptic plasticity. With high-speed, precisely-targeted, two-photon point imaging we measured both calcium rise and decay kinetics in spines and secondary dendrites in neocortical pyramidal neurons. We found that both rise and decay kinetics of changes in calcium-indicator fluorescence are about twice as fast in spines. During AP trains, spine calcium changes follow each AP, but not in dendrites. Apart from the higher surface-to-volume ratio (SVR), we observed that neocortical dendritic spines have a markedly smaller endogenous buffer capacity with respect to their parental dendrites. Calcium influx time course and calcium extrusion rate were both in the same range for spines and dendrites when fitted with a dynamic multi-compartment model that included calcium binding kinetics and diffusion. In a subsequent analysis we used this model to investigate which parameters are critical determinants in spine calcium dynamics. The model confirmed the experimental findings: a higher SVR is not sufficient by itself to explain the faster rise time kinetics in spines, but only when paired with a lower buffer capacity in spines. Simulations at zero calcium-dye conditions show that calmodulin is more efficiently activated in spines, which indicates that spine morphology and buffering conditions in neocortical spines favor synaptic plasticity.
Collapse
Affiliation(s)
- L. Niels Cornelisse
- Department of Experimental Neurophysiology, Centre for Neurogenomics and Cognitive Research (CNCR), Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
- Department of Functional Genomics, Centre for Neurogenomics and Cognitive Research (CNCR), Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
- * To whom correspondence should be addressed. E-mail: (LC); (HM)
| | - Ronald A. J. van Elburg
- Department of Experimental Neurophysiology, Centre for Neurogenomics and Cognitive Research (CNCR), Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Rhiannon M. Meredith
- Department of Experimental Neurophysiology, Centre for Neurogenomics and Cognitive Research (CNCR), Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Rafael Yuste
- Howard Hughes Medical Institute, Department of Biological Sciences, Columbia University, New York, New York, United States of America
| | - Huibert D. Mansvelder
- Department of Experimental Neurophysiology, Centre for Neurogenomics and Cognitive Research (CNCR), Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
- * To whom correspondence should be addressed. E-mail: (LC); (HM)
| |
Collapse
|
49
|
Schmidt H, Kunerth S, Wilms C, Strotmann R, Eilers J. Spino-dendritic cross-talk in rodent Purkinje neurons mediated by endogenous Ca2+-binding proteins. J Physiol 2007; 581:619-29. [PMID: 17347272 PMCID: PMC2075171 DOI: 10.1113/jphysiol.2007.127860] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The range of actions of the second messenger Ca(2+) is a key determinant of neuronal excitability and plasticity. For dendritic spines, there is on-going debate regarding how diffusional efflux of Ca(2+) affects spine signalling. However, the consequences of spino-dendritic coupling for dendritic Ca(2+) homeostasis and downstream signalling cascades have not been explored to date. We addressed this question by four-dimensional computer simulations, which were based on Ca(2+)-imaging data from mice that either express or lack distinct endogenous Ca(2+)-binding proteins. Our simulations revealed that single active spines do not affect dendritic Ca(2+) signalling. Neighbouring, coactive spines, however, induce sizeable increases in dendritic [Ca(2+)](i) when they process slow synaptic Ca(2+) signals, such as those implicated in the induction of long-term plasticity. This spino-dendritic coupling is mediated by buffered diffusion, specifically by diffusing calbindin-bound Ca(2+). This represents a central mechanism for activating calmodulin in dendritic shafts and therefore a novel form of signal integration in spiny dendrites.
Collapse
Affiliation(s)
- Hartmut Schmidt
- Carl-Ludwig-Institut für Physiologie, Liebigstrasse 27, 04103 Leipzig, Germany.
| | | | | | | | | |
Collapse
|
50
|
Santamaria F, Wils S, De Schutter E, Augustine GJ. Anomalous diffusion in Purkinje cell dendrites caused by spines. Neuron 2007; 52:635-48. [PMID: 17114048 PMCID: PMC1994115 DOI: 10.1016/j.neuron.2006.10.025] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2005] [Revised: 02/15/2006] [Accepted: 10/18/2006] [Indexed: 11/28/2022]
Abstract
We combined local photolysis of caged compounds with fluorescence imaging to visualize molecular diffusion within dendrites of cerebellar Purkinje cells. Diffusion of a volume marker, fluorescein dextran, within spiny dendrites was remarkably slow in comparison to its diffusion in smooth dendrites. Computer simulations indicate that this retardation is due to a transient trapping of molecules within dendritic spines, yielding anomalous diffusion. We considered the influence of spine trapping on the diffusion of calcium ions (Ca(2+)) and inositol-1,4,5-triphospate (IP(3)), two synaptic second messengers. Diffusion of IP(3) was strongly influenced by the presence of dendritic spines, while Ca(2+) was removed so rapidly that it could not diffuse far enough to be trapped. We conclude that an important function of dendritic spines may be to trap chemical signals and thereby create slowed anomalous diffusion within dendrites.
Collapse
Affiliation(s)
- Fidel Santamaria
- Department of Neurobiology, Duke University Medical Center, PO Box 3209, Durham, North Carolina 27710, USA
| | | | | | | |
Collapse
|