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https://www.readbyqxmd.com/read/28643105/differential-role-of-gabaa-receptors-and-neuroligin-2-for-perisomatic-gabaergic-synapse-formation-in-the-hippocampus
#1
Patrizia Panzanelli, Simon Früh, Jean-Marc Fritschy
Perisomatic GABAergic synapses onto hippocampal pyramidal cells arise from two populations of basket cells with different neurochemical and functional properties. The presence of the dystrophin-glycoprotein complex in their postsynaptic density (PSD) distinguishes perisomatic synapses from GABAergic synapses on dendrites and the axon-initial segment. Targeted deletion of neuroligin 2 (NL2), a transmembrane protein interacting with presynaptic neurexin, has been reported to disrupt postsynaptic clustering of GABAA receptors (GABAAR) and their anchoring protein, gephyrin, at perisomatic synapses...
June 22, 2017: Brain Structure & Function
https://www.readbyqxmd.com/read/28634442/mild-traumatic-brain-injury-evokes-pyramidal-neuron-axon-initial-segment-plasticity-and-diffuse-presynaptic-inhibitory-terminal-loss
#2
Michal Vascak, Jianli Sun, Matthew Baer, Kimberle M Jacobs, John T Povlishock
The axon initial segment (AIS) is the site of action potential (AP) initiation, thus a crucial regulator of neuronal activity. In excitatory pyramidal neurons, the high density of voltage-gated sodium channels (NaV1.6) at the distal AIS regulates AP initiation. A surrogate AIS marker, ankyrin-G (ankG) is a structural protein regulating neuronal functional via clustering voltage-gated ion channels. In neuronal circuits, changes in presynaptic input can alter postsynaptic output via AIS structural-functional plasticity...
2017: Frontiers in Cellular Neuroscience
https://www.readbyqxmd.com/read/28624616/age-related-plasticity-of-the-axon-initial-segment-of-cortical-pyramidal-cells-in-marmoset-monkeys
#3
Nafiseh Atapour, Marcello G P Rosa
Structural plasticity of the axon initial segment (AIS), the site of action potential initiation, is observed as part of the normal early development of the cortex, as well as in association with injury and disease. Here, we show that structural AIS plasticity also occurs with normal aging in adult marmosets. Immunohistochemical techniques were used to reveal the extent of the AIS of layer 2/3A pyramidal cells in 8 neocortical areas. We found that the AIS length varied significantly between areas in young adult (2-3 years old) marmosets, with neurons in frontal area 14C having the longest AIS, and those in the primary visual cortex the shortest...
May 22, 2017: Neurobiology of Aging
https://www.readbyqxmd.com/read/28612392/linking-activity-dependent-control-of-axon-initial-segment-structure-to-the-cytoskeleton
#4
Oriol Ros, Xavier Nicol
No abstract text is available yet for this article.
June 14, 2017: European Journal of Neuroscience
https://www.readbyqxmd.com/read/28595650/acute-neuroinflammation-induces-ais-structural-plasticity-in-a-nox2-dependent-manner
#5
S D Benusa, N M George, B A Sword, G H DeVries, J L Dupree
BACKGROUND: Chronic microglia-mediated inflammation and oxidative stress are well-characterized underlying factors in neurodegenerative disease, whereby reactive inflammatory microglia enhance ROS production and impact neuronal integrity. Recently, it has been shown that during chronic inflammation, neuronal integrity is compromised through targeted disruption of the axon initial segment (AIS), the axonal domain critical for action potential initiation. AIS disruption was associated with contact by reactive inflammatory microglia which wrap around the AIS, increasing association with disease progression...
June 8, 2017: Journal of Neuroinflammation
https://www.readbyqxmd.com/read/28584914/optical-coherence-tomography-for-the-diagnosis-and-monitoring-of-idiopathic-intracranial-hypertension
#6
Philipp Albrecht, Christine Blasberg, Marius Ringelstein, Ann-Kristin Müller, David Finis, Rainer Guthoff, Ella-Maria Kadas, Wolf Lagreze, Orhan Aktas, Hans-Peter Hartung, Friedemann Paul, Alexander U Brandt, Axel Methner
The objectives of the study were to investigate the value of optical coherence tomography in detecting papilledema in patients with idiopathic intracranial hypertension (IIH), a disease which is difficult to monitor and which can lead to permanent visual deficits; to analyze retinal changes over time. In this non-interventional case-control study, spectral-domain optical coherence tomography (SD-OCT) was used to analyze the retinal and optic nerve head (ONH) morphology of 21 patients with IIH and 27 age- and sex-matched healthy controls over time...
June 5, 2017: Journal of Neurology
https://www.readbyqxmd.com/read/28584877/neocortical-chandelier-cells-developmentally-shape-axonal-arbors-through-reorganization-but-establish-subcellular-synapse-specificity-without-refinement
#7
André Steinecke, Ellie Hozhabri, Stephen Tapanes, Yugo Ishino, Hongkui Zeng, Naomi Kamasawa, Hiroki Taniguchi
Diverse types of cortical interneurons (INs) mediate various kinds of inhibitory control mechanisms to balance and shape network activity. Distinct IN subtypes develop uniquely organized axonal arbors that innervate different subcellular compartments of excitatory principal neurons (PNs), which critically contribute to determining their output properties. However, it remains poorly understood how they establish this peculiar axonal organization and synaptic connectivity during development. Here, taking advantage of genetic labeling of IN progenitors, we examined developmental processes of axonal arbors and synaptic connections formed by murine chandelier cells (ChCs), which innervate axon initial segments (AISs) of PNs and thus powerfully regulate their spike generation...
May 2017: ENeuro
https://www.readbyqxmd.com/read/28572759/dendritic-actin-cytoskeleton-structure-functions-and-regulations
#8
REVIEW
Anja Konietzny, Julia Bär, Marina Mikhaylova
Actin is a versatile and ubiquitous cytoskeletal protein that plays a major role in both the establishment and the maintenance of neuronal polarity. For a long time, the most prominent roles that were attributed to actin in neurons were the movement of growth cones, polarized cargo sorting at the axon initial segment, and the dynamic plasticity of dendritic spines, since those compartments contain large accumulations of actin filaments (F-actin) that can be readily visualized using electron- and fluorescence microscopy...
2017: Frontiers in Cellular Neuroscience
https://www.readbyqxmd.com/read/28536506/axonal-membranes-and-their-domains-assembly-and-function-of-the-axon-initial-segment-and-node-of-ranvier
#9
REVIEW
Andrew D Nelson, Paul M Jenkins
Neurons are highly specialized cells of the nervous system that receive, process and transmit electrical signals critical for normal brain function. Here, we review the intricate organization of axonal membrane domains that facilitate rapid action potential conduction underlying communication between complex neuronal circuits. Two critical excitable domains of vertebrate axons are the axon initial segment (AIS) and the nodes of Ranvier, which are characterized by the high concentrations of voltage-gated ion channels, cell adhesion molecules and specialized cytoskeletal networks...
2017: Frontiers in Cellular Neuroscience
https://www.readbyqxmd.com/read/28536263/axodendritic-sorting-and-pathological-missorting-of-tau-is-isoform-specific-and-determined-by-axon-initial-segment-architecture
#10
Hans Zempel, Frank Dennissen, Yatender Kumar, Julia Luedtke, Jacek Biernat, Eva-Maria Mandelkow, Eckhard Mandelkow
Subcellular mislocalization of the microtubule-associated protein Tau is a hallmark of Alzheimer disease (AD) and other tauopathies. Six Tau isoforms, differentiated by the presence or absence of a second repeat or of N-terminal inserts, exist in the human CNS but their physiological and pathological differences have long remained remain elusive. Here, we investigated the properties and distributions of human and rodent Tau isoforms in primary forebrain rodent neurons. We found that the Tau-Diffusion-Barrier (TDB), located within the Axon-Initial-Segment (AIS), controls retrograde (axon-to-soma) and anterograde (soma-to-axon) traffic of Tau...
May 23, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28534438/the-axonal-cytoskeleton-and-the-assembly-of-nodes-of-ranvier
#11
Aniket Ghosh, Diane L Sherman, Peter J Brophy
Vertebrate nervous systems rely on rapid nerve impulse transmission to support their complex functions. Fast conduction depends on ensheathment of nerve axons by myelin-forming glia and the clustering of high concentrations of voltage-gated sodium channels (Nav) in the axonal gaps between myelinated segments. These gaps are the nodes of Ranvier. Depolarization of the axonal membrane initiates the action potential responsible for impulse transmission, and the Nav help ensure that this is restricted to nodes...
May 1, 2017: Neuroscientist: a Review Journal Bringing Neurobiology, Neurology and Psychiatry
https://www.readbyqxmd.com/read/28533267/the-kv1-associated-molecules-tag-1-and-caspr2-are-selectively-targeted-to-axon-initial-segment-in-hippocampal-neurons
#12
Delphine Pinatel, Bruno Hivert, Margaux Saint-Martin, Nelly Noraz, Maria Savvaki, Domna Karagogeos, Catherine Faivre-Sarrailh
Caspr2 and TAG-1 are cell adhesion molecules (CAMs) associated with the voltage-gated potassium channels Kv1.1/1.2 at regions controlling axonal excitability, the axon initial segment (AIS) and juxtaparanodes of myelinated axons. The distribution of Kv1 at juxtaparanodes requires axo-glial contacts mediated by Caspr2 and TAG-1. In the present study, we showed that TAG-1 strongly co-localizes with Kv1.2 at the AIS of cultured hippocampal neurons whereas Caspr2 is uniformly expressed along the axolemma. Live-cell imaging revealed that Caspr2 and TAG-1 are sorted together in axonal transport vesicles...
May 22, 2017: Journal of Cell Science
https://www.readbyqxmd.com/read/28522735/d3-receptors-regulate-excitability-in-a-unique-class-of-prefrontal-pyramidal-cells
#13
Rebecca L Clarkson, Alayna T Liptak, Steven M Gee, Vikaas S Sohal, Kevin J Bender
The D3 dopamine receptor, a member of the Gi-coupled D2 family of dopamine receptors, is expressed throughout limbic circuits affected in neuropsychiatric disorders, including prefrontal cortex (PFC). These receptors are important for prefrontal executive function because pharmacological and genetic manipulations that affect prefrontal D3 receptors alter anxiety, social interaction, and reversal learning. However, the mechanisms by which D3 receptors regulate prefrontal circuits and whether D3 receptors regulate specific prefrontal subnetworks remains unknown...
June 14, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/28469558/intracellular-fibroblast-growth-factor-14-emerging-risk-factor-for-brain-disorders
#14
REVIEW
Jessica Di Re, Paul A Wadsworth, Fernanda Laezza
The finely tuned regulation of neuronal firing relies on the integrity of ion channel macromolecular complexes. Minimal disturbances of these tightly regulated networks can lead to persistent maladaptive plasticity of brain circuitry. The intracellular fibroblast growth factor 14 (FGF14) belongs to the nexus of proteins interacting with voltage-gated Na+ (Nav) channels at the axonal initial segment. Through isoform-specific interactions with the intracellular C-terminal tail of neuronal Nav channels (Nav1.1, Nav1...
2017: Frontiers in Cellular Neuroscience
https://www.readbyqxmd.com/read/28452088/myosin-ii-activity-is-required-for-structural-plasticity-at-the-axon-initial-segment
#15
Mark D Evans, Candida Tufo, Adna S Dumitrescu, Matthew S Grubb
In neurons, axons possess a molecularly defined and highly organised proximal region - the axon initial segment (AIS) - that is a key regulator of both electrical excitability and cellular polarity. Despite existing as a large, dense structure with specialised cytoskeletal architecture, the AIS is surprisingly plastic, with sustained alterations in neuronal activity bringing about significant alterations to its position, length or molecular composition. However, although the upstream activity-dependent signalling pathways that lead to such plasticity have begun to be elucidated, the downstream mechanisms that produce structural changes at the AIS are completely unknown...
April 27, 2017: European Journal of Neuroscience
https://www.readbyqxmd.com/read/28450535/sodium-channel-nav1-8-underlies-ttx-resistant-axonal-action-potential-conduction-in-somatosensory-c-fibers-of-distal-cutaneous-nerves
#16
Amanda H Klein, Alina Vyshnevska, Timothy V Hartke, Roberto De Col, Joseph L Mankowski, Brian Turnquist, Frank Bosmans, Peter W Reeh, Martin Schmelz, Richard W Carr, Matthias Ringkamp
Voltage-gated sodium (NaV) channels are responsible for the initiation and conduction of action potentials within primary afferents. The nine NaV channel isoforms recognized in mammals are often functionally divided into tetrodotoxin (TTX)-sensitive (TTX-s) channels (NaV1.1-NaV1.4, NaV1.6-NaV1.7) that are blocked by nanomolar concentrations and TTX-resistant (TTX-r) channels (NaV1.8 and NaV1.9) inhibited by millimolar concentrations, with NaV1.5 having an intermediate toxin sensitivity. For small-diameter primary afferent neurons, it is unclear to what extent different NaV channel isoforms are distributed along the peripheral and central branches of their bifurcated axons...
May 17, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/28441389/the-basis-of-sharp-spike-onset-in-standard-biophysical-models
#17
Maria Telenczuk, Bertrand Fontaine, Romain Brette
In most vertebrate neurons, spikes initiate in the axonal initial segment (AIS). When recorded in the soma, they have a surprisingly sharp onset, as if sodium (Na) channels opened abruptly. The main view stipulates that spikes initiate in a conventional manner at the distal end of the AIS, then progressively sharpen as they backpropagate to the soma. We examined the biophysical models used to substantiate this view, and we found that spikes do not initiate through a local axonal current loop that propagates along the axon, but through a global current loop encompassing the AIS and soma, which forms an electrical dipole...
2017: PloS One
https://www.readbyqxmd.com/read/28440877/bdnf-nt3-regulate-ais-location-and-affect-neuronal-excitability-in-cultured-hippocampal-neurons
#18
Yu Guo, Zi-Jun Su, Yi-Kun Chen, Zhen Chai
Plasticity of the axon initial segment (AIS) has aroused great interest in recent years because it regulates action potential initiation and neuronal excitability. AIS plasticity manifests as modulation of ion channels or variation in AIS structure. However, the mechanisms underlying structural plasticity of the AIS are not well understood. Here, we combined immunofluorescence, patch-clamp recordings, and pharmacological methods in cultured hippocampal neurons to investigate the factors participating in AIS structural plasticity during development...
April 25, 2017: Journal of Neurochemistry
https://www.readbyqxmd.com/read/28436546/corrigendum-the-impact-of-early-environmental-interventions-on-structural-plasticity-of-the-axon-initial-segment-in-neocortex-m-nozari-t-suzuki-m-g-p-rosa-k-yamakawa-and-n-atapour
#19
(no author information available yet)
No abstract text is available yet for this article.
April 24, 2017: Developmental Psychobiology
https://www.readbyqxmd.com/read/28426968/map2-defines-a-pre-axonal-filtering-zone-to-regulate-kif1-versus-kif5-dependent-cargo-transport-in-sensory-neurons
#20
Laura F Gumy, Eugene A Katrukha, Ilya Grigoriev, Dick Jaarsma, Lukas C Kapitein, Anna Akhmanova, Casper C Hoogenraad
Polarized cargo transport is essential for neuronal function. However, the minimal basic components required for selective cargo sorting and distribution in neurons remain elusive. We found that in sensory neurons the axon initial segment is largely absent and that microtubule-associated protein 2 (MAP2) defines the cargo-filtering zone in the proximal axon. Here, MAP2 directs axonal cargo entry by coordinating the activities of molecular motors. We show that distinct kinesins differentially regulate cargo velocity: kinesin-3 drives fast axonal cargo trafficking, while kinesin-1 slows down axonal cargo transport...
April 19, 2017: Neuron
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