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Cheng KW, Alhasan L, Rezk AR, Al-Abboodi A, Doran PM, Yeo LY, Chan PPY. Fast three-dimensional micropatterning of PC12 cells in rapidly crosslinked hydrogel scaffolds using ultrasonic standing waves. Biofabrication 2019; 12:015013. [DOI: 10.1088/1758-5090/ab4cca] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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von Bernhardi R, Eugenín-von Bernhardi J, Flores B, Eugenín León J. Glial Cells and Integrity of the Nervous System. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 949:1-24. [PMID: 27714682 DOI: 10.1007/978-3-319-40764-7_1] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Today, there is enormous progress in understanding the function of glial cells, including astroglia, oligodendroglia, Schwann cells, and microglia. Around 150 years ago, glia were viewed as a glue among neurons. During the course of the twentieth century, microglia were discovered and neuroscientists' views evolved toward considering glia only as auxiliary cells of neurons. However, over the last two to three decades, glial cells' importance has been reconsidered because of the evidence on their involvement in defining central nervous system architecture, brain metabolism, the survival of neurons, development and modulation of synaptic transmission, propagation of nerve impulses, and many other physiological functions. Furthermore, increasing evidence shows that glia are involved in the mechanisms of a broad spectrum of pathologies of the nervous system, including some psychiatric diseases, epilepsy, and neurodegenerative diseases to mention a few. It appears safe to say that no neurological disease can be understood without considering neuron-glia crosstalk. Thus, this book aims to show different roles played by glia in the healthy and diseased nervous system, highlighting some of their properties while considering that the various glial cell types are essential components not only for cell function and integration among neurons, but also for the emergence of important brain homeostasis.
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Affiliation(s)
- Rommy von Bernhardi
- Department of Neurology, School of Medicine, Pontificia Universidad Católica de Chile, Marcoleta 391, Santiago, Chile.
| | - Jaime Eugenín-von Bernhardi
- Physiological Genomics, Biomedical Center, Ludwig-Maximilians-University, Pettenkoferstr.12, 80336, Munich, Germany.,Graduate School of Systemic Neuroscience, Ludwig-Maximilians-University, 82152, Planegg-Martinsried, Munich, Germany
| | - Betsi Flores
- Department of Neurology, School of Medicine, Pontificia Universidad Católica de Chile, Marcoleta 391, Santiago, Chile
| | - Jaime Eugenín León
- Department of Biology, Faculty of Chemistry and Biology, USACH, Santiago, Chile
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Schraut NB, Walton S, Monsef JB, Shott S, Serici A, Soulii L, Amirouche F, Gonzalez MH, Kerns JM. What Protects Certain Nerves from Stretch Injury? Anat Rec (Hoboken) 2015; 299:111-7. [DOI: 10.1002/ar.23286] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 09/14/2015] [Accepted: 09/30/2015] [Indexed: 11/10/2022]
Affiliation(s)
- Nicholas B. Schraut
- Department of Orthopaedic Surgery; University of Illinois Chicago; Chicago Illinois
| | - Sharon Walton
- Department of Orthopaedic Surgery; University of Illinois Chicago; Chicago Illinois
| | - Jad Bou Monsef
- Department of Orthopaedic Surgery; University of Illinois Chicago; Chicago Illinois
| | - Susan Shott
- Department of Internal Medicine; Rush University Medical Center; Chicago Illinois
| | - Anthony Serici
- Department of Anatomy and Cell Biology; Rush University Medical Center; Chicago Illinois
| | - Lioubov Soulii
- Department of Orthopaedic Surgery; University of Illinois Chicago; Chicago Illinois
| | - Farid Amirouche
- Department of Orthopaedic Surgery; University of Illinois Chicago; Chicago Illinois
| | - Mark H. Gonzalez
- Department of Orthopaedic Surgery; University of Illinois Chicago; Chicago Illinois
| | - James M. Kerns
- Department of Orthopaedic Surgery; University of Illinois Chicago; Chicago Illinois
- Department of Anatomy and Cell Biology; Rush University Medical Center; Chicago Illinois
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Leinders M, Koehrn FJ, Bartok B, Boyle DL, Shubayev V, Kalcheva I, Yu NK, Park J, Kaang BK, Hefferan MP, Firestein GS, Sorkin LS. Differential distribution of PI3K isoforms in spinal cord and dorsal root ganglia: potential roles in acute inflammatory pain. Pain 2014; 155:1150-1160. [PMID: 24631588 PMCID: PMC4128246 DOI: 10.1016/j.pain.2014.03.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Revised: 03/03/2014] [Accepted: 03/05/2014] [Indexed: 11/30/2022]
Abstract
PI3-kinases (PI3Ks) participate in nociception within spinal cord, dorsal root ganglion (DRG), and peripheral nerves. To extend our knowledge, we immunohistochemically stained for each of the 4 class I PI3K isoforms along with several cell-specific markers within the lumbar spinal cord, DRG, and sciatic nerve of naive rats. Intrathecal and intraplantar isoform specific antagonists were given as pretreatments before intraplantar carrageenan; pain behavior was then assessed over time. The α-isoform was localized to central terminals of primary afferent fibers in spinal cord laminae IIi to IV as well as to neurons in ventral horn and DRG. The PI3Kβ isoform was the only class I isoform seen in dorsal horn neurons; it was also observed in DRG, Schwann cells, and axonal paranodes. The δ-isoform was found in spinal cord white matter oligodendrocytes and radial astrocytes, and the γ-isoform was seen in a subpopulation of IB4-positive DRG neurons. No isoform co-localized with microglial markers or satellite cells in naive tissue. Only the PI3Kβ antagonist, but none of the other antagonists, had anti-allodynic effects when administered intrathecally; coincident with reduced pain behavior, this agent completely blocked paw carrageenan-induced dorsal horn 2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl) propanoic acid (AMPA) receptor trafficking to plasma membranes. Intraplantar administration of the γ-antagonist prominently reduced pain behavior. These data suggest that each isoform displays specificity with regard to neuronal type as well as to specific tissues. Furthermore, each PI3K isoform has a unique role in development of nociception and tissue inflammation.
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Affiliation(s)
- Mathias Leinders
- Department of Anesthesiology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Fred J. Koehrn
- Department of Anesthesiology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Beatrix Bartok
- Deprtment of Medicine, Division of Rheumatology, University of California, San Diego, La Jolla, CA
| | - David L. Boyle
- Deprtment of Medicine, Division of Rheumatology, University of California, San Diego, La Jolla, CA
| | - Veronica Shubayev
- Department of Anesthesiology, University of California, San Diego, La Jolla, CA 92093, USA
- San Diego VA Healthcare System, La Jolla, CA
| | - Iveta Kalcheva
- Deprtment of Medicine, Division of Rheumatology, University of California, San Diego, La Jolla, CA
| | - Nam-Kyung Yu
- Department of Biological Sciences and Brain and Cognitive Sciences, Seoul National University, Seoul 151-747, Korea
| | - Jihye Park
- Department of Biological Sciences and Brain and Cognitive Sciences, Seoul National University, Seoul 151-747, Korea
| | - Bong-Kiun Kaang
- Department of Biological Sciences and Brain and Cognitive Sciences, Seoul National University, Seoul 151-747, Korea
| | | | - Gary S. Firestein
- Deprtment of Medicine, Division of Rheumatology, University of California, San Diego, La Jolla, CA
| | - Linda S. Sorkin
- Department of Anesthesiology, University of California, San Diego, La Jolla, CA 92093, USA
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Nualart-Marti A, Solsona C, Fields RD. Gap junction communication in myelinating glia. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:69-78. [PMID: 22326946 DOI: 10.1016/j.bbamem.2012.01.024] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 01/17/2012] [Accepted: 01/26/2012] [Indexed: 10/14/2022]
Abstract
Gap junction communication is crucial for myelination and axonal survival in both the peripheral nervous system (PNS) and central nervous system (CNS). This review examines the different types of gap junctions in myelinating glia of the PNS and CNS (Schwann cells and oligodendrocytes respectively), including their functions and involvement in neurological disorders. Gap junctions mediate intercellular communication among Schwann cells in the PNS, and among oligodendrocytes and between oligodendrocytes and astrocytes in the CNS. Reflexive gap junctions mediating transfer between different regions of the same cell promote communication between cellular compartments of myelinating glia that are separated by layers of compact myelin. Gap junctions in myelinating glia regulate physiological processes such as cell growth, proliferation, calcium signaling, and participate in extracellular signaling via release of neurotransmitters from hemijunctions. In the CNS, gap junctions form a glial network between oligodendrocytes and astrocytes. This transcellular communication is hypothesized to maintain homeostasis by facilitating restoration of membrane potential after axonal activity via electrical coupling and the re-distribution of potassium ions released from axons. The generation of transgenic mice for different subsets of connexins has revealed the contribution of different connexins in gap junction formation and illuminated new subcellular mechanisms underlying demyelination and cognitive defects. Alterations in metabolic coupling have been reported in animal models of X-linked Charcot-Marie-Tooth disease (CMTX) and Pelizaeus-Merzbarcher-like disease (PMLD), which are caused by mutations in the genes encoding for connexin 32 and connexin 47 respectively. Future research identifying the expression and regulation of gap junctions in myelinating glia is likely to provide a better understanding of myelinating glia in nervous system function, plasticity, and disease. This article is part of a Special Issue entitled: The Communicating junctions, roles and dysfunctions.
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Affiliation(s)
- Anna Nualart-Marti
- Department of Pathology and Experimental Therapeutics, University of Barcelona, Barcelona, Spain.
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Velumian AA, Samoilova M, Fehlings MG. Visualization of cytoplasmic diffusion within living myelin sheaths of CNS white matter axons using microinjection of the fluorescent dye Lucifer Yellow. Neuroimage 2010; 56:27-34. [PMID: 21073961 DOI: 10.1016/j.neuroimage.2010.11.022] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2010] [Revised: 08/10/2010] [Accepted: 11/04/2010] [Indexed: 01/16/2023] Open
Abstract
The compactness of myelin allows for efficient insulation defining rapid propagation of action potentials, but also raises questions about how cytoplasmic access to its membranes is achieved, which is critical for physiological activity. Understanding the organization of cytoplasmic ('water') spaces of myelin is also important for diffusion MRI studies of CNS white matter. Using longitudinal slices of mature rat spinal cord, we monitored the diffusion of the water-soluble fluorescent dye Lucifer Yellow injected into individual oligodendrocytes or internodal myelin. We show that living myelin sheaths on CNS axons are fenestrated by a network of diffusionally interconnected cytoplasmic 'pockets' (1.9 ± 0.2 pockets per 10μm sheath length, n=58) that included Schmidt-Lanterman clefts (SLCs) and numerous smaller compartments. 3-D reconstructions of these cytoplasmic networks show that the outer cytoplasmic layer of CNS myelin is cylindrically 'encuffing', which differs from EM studies using fixed tissue. SLCs were found in different 'open states' and remained stable within a 1-2hour observation period. Unlike the peripheral nervous system, where similarly small (<500Da) molecules diffuse along the whole myelin segment within a few minutes, in mature CNS this takes more than one hour. The slower cytoplasmic diffusion in CNS myelin possibly contributes to its known vulnerability to injury and limited capacity for repair. Our findings point to an elaborate cytoplasmic access to compact CNS myelin. These results could be of relevance to MRI studies of CNS white matter and to CNS repair/regeneration strategies.
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Affiliation(s)
- Alexander A Velumian
- Division of Genetics and Development, Toronto Western Research Institute, Canada.
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Gess B, Lohmann C, Halfter H, Young P. Sodium-dependent vitamin C transporter 2 (SVCT2) is necessary for the uptake of L-ascorbic acid into Schwann cells. Glia 2010; 58:287-99. [PMID: 19672970 DOI: 10.1002/glia.20923] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Ascorbic acid has been shown to be an essential component for in vitro myelination and to improve the clinical and pathological phenotype of a mouse model of Charcot-Marie-tooth disease 1A. The mechanism of ascorbic acid uptake into peripheral nerves, however, has not been addressed so far. Hence, we studied the expression and activity of sodium-dependent vitamin C transporters 1 and 2 (SVCT1 and 2) in the peripheral nervous system. Using immunohistochemistry, immunoblotting, and reverse transcription PCR, we could show that SVCT1 and 2 were differentially expressed in myelinated peripheral nerve fibers and Schwann cell (SC) cultures. SVCT1 was expressed at very low levels confined to the axons, whereas SVCT2 was highly expressed both in the axons and in the SCs. SVCT2 was localized particularly in SC compartments of uncompacted myelin. Uptake assays using (14)C-labeled ascorbic acid showed transport of ascorbic acid into SC cultures. Ascorbic acid transport was dependent on the concentration of sodium, magnesium, and calcium in the extracellular medium. Treatment with the flavonoid phloretin, a known inhibitor of SVCT1 and 2, and specific RNA interference with SVCT2 caused significant reductions in ascorbic acid uptake into SCs. Phloretin-inhibited uptake of ascorbic acid was further shown in freshly dissected, cell-culture-naïve rat sciatic nerves. These results provide evidence for the first time that uptake of ascorbic acid in the peripheral nervous system is crucially dependent on the expression and activity of SVCT2.
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Affiliation(s)
- Burkhard Gess
- Department of Neurology, University of Muenster, Albert-Schweitzer-Strasse 33, Muenster, Germany
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Zoga V, Kawano T, Liang MY, Bienengraeber M, Weihrauch D, McCallum B, Gemes G, Hogan Q, Sarantopoulos C. KATP channel subunits in rat dorsal root ganglia: alterations by painful axotomy. Mol Pain 2010; 6:6. [PMID: 20102598 PMCID: PMC2825500 DOI: 10.1186/1744-8069-6-6] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2009] [Accepted: 01/26/2010] [Indexed: 11/16/2022] Open
Abstract
Background ATP-sensitive potassium (KATP) channels in neurons mediate neuroprotection, they regulate membrane excitability, and they control neurotransmitter release. Because loss of DRG neuronal KATP currents is involved in the pathophysiology of pain after peripheral nerve injury, we characterized the distribution of the KATP channel subunits in rat DRG, and determined their alterations by painful axotomy using RT-PCR, immunohistochemistry and electron microscopy. Results PCR demonstrated Kir6.1, Kir6.2, SUR1 and SUR2 transcripts in control DRG neurons. Protein expression for all but Kir6.1 was confirmed by Western blots and immunohistochemistry. Immunostaining of these subunits was identified by fluorescent and confocal microscopy in plasmalemmal and nuclear membranes, in the cytosol, along the peripheral fibers, and in satellite glial cells. Kir6.2 co-localized with SUR1 subunits. Kir6.2, SUR1, and SUR2 subunits were identified in neuronal subpopulations, categorized by positive or negative NF200 or CGRP staining. KATP current recorded in excised patches was blocked by glybenclamide, but preincubation with antibody against SUR1 abolished this blocking effect of glybenclamide, confirming that the antibody targets the SUR1 protein in the neuronal plasmalemmal membrane. In the myelinated nerve fibers we observed anti-SUR1 immunostaining in regularly spaced funneled-shaped structures. These structures were identified by electron microscopy as Schmidt-Lanterman incisures (SLI) formed by the Schwann cells. Immunostaining against SUR1 and Kir6.2 colocalized with anti-Caspr at paranodal sites. DRG excised from rats made hyperalgesic by spinal nerve ligation exhibited similar staining against Kir6.2, SUR1 or SUR2 as DRG from controls, but showed decreased prevalence of SUR1 immunofluorescent NF200 positive neurons. In DRG and dorsal roots proximal to axotomy SLI were smaller and showed decreased SUR1 immunofluorescence. Conclusions We identified Kir6.2/SUR1 and Kir6.2/SUR2 KATP channels in rat DRG neuronal somata, peripheral nerve fibers, and glial satellite and Schwann cells, in both normal state and after painful nerve injury. This is the first report of KATP channels in paranodal sites adjacent to nodes of Ranvier and in the SLI of the Schwann cells. After painful axotomy KATP channels are downregulated in large, myelinated somata and also in SLI, which are also of smaller size compared to controls. Because KATP channels may have diverse functional roles in neurons and glia, further studies are needed to explore the potential of KATP channels as targets of therapies against neuropathic pain and neurodegeneration.
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Affiliation(s)
- Vasiliki Zoga
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
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Bellinger SC, Miyazawa G, Steinmetz PN. Submyelin potassium accumulation may functionally block subsets of local axons during deep brain stimulation: a modeling study. J Neural Eng 2008; 5:263-74. [PMID: 18566505 DOI: 10.1088/1741-2560/5/3/001] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Deep brain stimulation has been used for over a decade to relieve the symptoms of Parkinson's disease, although its mechanism of action remains poorly understood. To better understand the direct effects of DBS on central neurons, a computational model of a myelinated axon has been constructed which includes the effects of K(+) accumulation within the peri-axonal space. Using best estimates of anatomic and electrogenic model parameters for in vivo STN axons, the model predicts a functional block along the axon due to K(+) accumulation in the submyelin space. The functional block occurs for a range of model parameters: high stimulation frequencies (>130 Hz); high extracellular K(+) concentrations (>3 x 10(-3) M); low maximum Na(+)/K(+) ATPase current densities (<0.026 A m(-2)); low diffusion coefficients for K(+) diffusion out of the submyelin space (<2.4 x 10(-9) m(2) s(-1)); small periaxonal space widths of the myelin attachment sections (<2.7 x 10(-9) m) and perinodal/internodal sections (<8.4 x 10(-9) m). These results suggest that therapeutic DBS of the STN likely results in a functional block for many STN axons, although a subset of STN axons may also be activated at the stimulating frequency.
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Affiliation(s)
- S C Bellinger
- Harrington Department of Bioengineering, Arizona State University, Tempe, AZ 85287-9709, USA
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Kretschmer T, Nguyen DH, Beuerman RW, Tiel RL, Kline DG. Elevated ankyrin G in a plexiform neurofibroma and neuromas associated with pain. J Clin Neurosci 2008; 11:886-9. [PMID: 15519868 DOI: 10.1016/j.jocn.2003.09.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2003] [Accepted: 09/04/2003] [Indexed: 12/23/2022]
Abstract
UNLABELLED Ankyrin G has recently been shown to be responsible for activation of sodium channels in the developing and regenerating axonal membrane. Via this sodium channel mechanism, elevated ankyrin G levels have been linked with spontaneous ectopic hyperexcitability and thus with pain phenomena in nervous tissue. Ankyrin G, a transmembrane, structural protein of the axon, was examined in four conditions: (a) painful plexiform neurofibroma; (b) painful neuroma; (c) non-painful neuromas; (d) normal nerve. Neurofibroma tissue was obtained from an 18-year old male patient who developed an intensely painful, plexiform neurofibroma of the posterior femoral cutaneous nerve and subsequently underwent surgery. Sample proteins were separated by PAGE and labeled with anti-ankyrin G antibodies in a Western blot procedure. RESULTS The ankyrin G band density (mug) of protein for the painful neurofibroma was 6014 and was 3557 for the painful neuroma as compared to 3041, 1988 and 606 (mean+/-SD=1878+/-1221) for the three non-painful neuromas. Ankyrin G expression in normal nerves (8 specimens from 7 patients) was comparatively less (mean+/-SD=411+/-339). CONCLUSION Our results may represent the first evidence for abnormally increased levels of ankyrin G protein with painful neurofibromas. Due to ankyrin G's multifunctional role in the development and remodeling of excitable membranes, it can be hypothesized that the significant increase contributes to the development of hyperexcitable axonal membranes in neurofibromas and potentially other peripheral pain conditions.
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Inda MC, DeFelipe J, Muñoz A. Voltage-gated ion channels in the axon initial segment of human cortical pyramidal cells and their relationship with chandelier cells. Proc Natl Acad Sci U S A 2006; 103:2920-5. [PMID: 16473933 PMCID: PMC1413846 DOI: 10.1073/pnas.0511197103] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The axon initial segment (AIS) of pyramidal cells is a critical region for the generation of action potentials and for the control of pyramidal cell activity. Here we show that Na+ and K+ voltage-gated channels, together with other molecules involved in the localization of ion channels, are distributed asymmetrically in the AIS of pyramidal cells situated in the human temporal neocortex. There is a high density of Na+ channels distributed along the length of the AIS together with the associated proteins spectrin betaIV and ankyrin G. In contrast, Kv1.2 channels are associated with the adhesion molecule Caspr2, and they are mostly localized to the distal region of the AIS. In general, the distal region of the AIS is targeted by the GABAergic axon terminals of chandelier cells, whereas the proximal region is innervated, mostly by other types of GABAergic interneurons. We suggest that this molecular segregation and the consequent regional specialization of the GABAergic input to the AIS of pyramidal cells may have important functional implications for the control of pyramidal cell activity.
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Affiliation(s)
- Maria Carmen Inda
- *Departamento de Biología Celular, Universidad Complutense de Madrid, Jose Antonio Novais 2, 28040 Madrid, Spain; and
- Instituto Cajal, Consejo Superior de Investigaciones Cientificas, Avenida Doctor Arce 37, 28002 Madrid, Spain
| | - Javier DeFelipe
- Instituto Cajal, Consejo Superior de Investigaciones Cientificas, Avenida Doctor Arce 37, 28002 Madrid, Spain
- To whom correspondence should be addressed. E-mail:
| | - Alberto Muñoz
- *Departamento de Biología Celular, Universidad Complutense de Madrid, Jose Antonio Novais 2, 28040 Madrid, Spain; and
- Instituto Cajal, Consejo Superior de Investigaciones Cientificas, Avenida Doctor Arce 37, 28002 Madrid, Spain
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Giannì M, Liberti M, Apollonio F, D'Inzeo G. Modeling electromagnetic fields detectability in a HH-like neuronal system: stochastic resonance and window behavior. BIOLOGICAL CYBERNETICS 2006; 94:118-27. [PMID: 16369796 DOI: 10.1007/s00422-005-0029-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2005] [Accepted: 09/22/2005] [Indexed: 05/05/2023]
Abstract
Noise has already been shown to play a constructive role in neuronal processing and reliability, according to stochastic resonance (SR). Here another issue is addressed, concerning noise role in the detectability of an exogenous signal, here representing an electromagnetic (EM) field. A Hodgkin-Huxley like neuronal model describing a myelinated nerve fiber is proposed and validated, excited with a suprathreshold stimulation. EM field is introduced as an additive voltage input and its detectability in neuronal response is evaluated in terms of the output signal-to-noise ratio. Noise intensities maximizing spiking activity coherence with the exogenous EM signal are clearly shown, indicating a stochastic resonant behavior, strictly connected to the model frequency sensitivity. In this study SR exhibits a window of occurrence in the values of field frequency and intensity, which is a kind of effect long reported in bioelectromagnetic experimental studies. The spatial distribution of the modeled structure also allows to investigate possible effects on action potentials saltatory propagation, which results to be reliable and robust over the presence of an exogenous EM field and biological noise. The proposed approach can be seen as assessing biophysical bases of medical applications funded on electric and magnetic stimulation where the role of noise as a cooperative factor has recently gained growing attention.
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Affiliation(s)
- Matteo Giannì
- ICEmB at Department of Electronic Engineering, La Sapienza University of Rome, 00184 Rome, Italy.
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Lee KH, Ryu CJ, Hong HJ, Kim J, Lee EH. cDNA Microarray Analysis of Nerve Growth Factor-Regulated Gene Expression Profile in Rat PC12 Cells. Neurochem Res 2005; 30:533-40. [PMID: 16076023 DOI: 10.1007/s11064-005-2688-y] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Nerve growth factor (NGF)-driven differentiation of PC12 cells into neuronal-like cells provides a representative model system for studying neuronal differentiation processes. Despite of extensive research, gene regulation associated with the differentiation program in PC12 cells still needs to be elucidated. We used cDNA microarray analysis to characterize the response of PC12 cells to NGF at mRNA expression. Forty-six genes were reproducibly influenced by 2-fold or more after NGF treatment for 5 days. Twenty-five of the regulated transcripts were matched to genes which have known functions. Among the microarray results confirmed with real-time reverse transcriptase assay, several genes have not previously known to be modulated by NGF. The results mostly reflected changes in molecules regulating neural plasticity, cytoskeletal organization, and lipid metabolism, which include neuritin, PDZ protein Mrt1, lipoprotein lipase, tropomodulin 1 and rhoB. These observed genetic changes may provide new information about molecular mechanisms underlying NGF-promoted differentiation of PC12 cells.
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Affiliation(s)
- Kyung-Hee Lee
- Graduate School of East-West Medical Science, Kyung Hee University, Korea
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McEwen DP, Isom LL. Heterophilic Interactions of Sodium Channel β1 Subunits with Axonal and Glial Cell Adhesion Molecules. J Biol Chem 2004; 279:52744-52. [PMID: 15466474 DOI: 10.1074/jbc.m405990200] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Voltage-gated sodium channels localize at high density in axon initial segments and nodes of Ranvier in myelinated axons. Sodium channels consist of a pore-forming alpha subunit and at least one beta subunit. beta1 is a member of the immunoglobulin superfamily of cell adhesion molecules and interacts homophilically and heterophilically with contactin and Nf186. In this study, we characterized beta1 interactions with contactin and Nf186 in greater detail and investigated interactions of beta1 with NrCAM, Nf155, and sodium channel beta2 and beta3 subunits. Using Fc fusion proteins and immunocytochemical techniques, we show that beta1 interacts with the fibronectin-like domains of contactin. beta1 also interacts with NrCAM, Nf155, sodium channel beta2, and Nf186 but not with sodium channel beta3. The interaction of the extracellular domains of beta1 and beta2 requires the region 169TEEEGKTDGEGNA181 located in the intracellular domain of beta2. Interaction of beta1 with Nf186 results in increased Nav).2 cell surface density over alpha alone, similar to that shown previously for contactin and beta2. We propose that beta1 is the critical communication link between sodium channels, nodal cell adhesion molecules, and ankyrinG.
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Affiliation(s)
- Dyke P McEwen
- Department of Pharmacology, University of Michigan, Ann Arbor, Michigan 48109-0632, USA
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Shen W, Hernandez-Lopez S, Tkatch T, Held JE, Surmeier DJ. Kv1.2-containing K+ channels regulate subthreshold excitability of striatal medium spiny neurons. J Neurophysiol 2003; 91:1337-49. [PMID: 13679409 DOI: 10.1152/jn.00414.2003] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A slowly inactivating, low-threshold K(+) current has been implicated in the regulation of state transitions and repetitive activity in striatal medium spiny neurons. However, the molecular identity of the channels underlying this current and their biophysical properties remain to be clearly determined. Because previous work had suggested this current arose from Kv1 family channels, high-affinity toxins for this family were tested for their ability to block whole cell K(+) currents activated by depolarization of acutely isolated neurons. alpha-Dendrotoxin, which blocks channels containing Kv1.1, Kv1.2, or Kv1.6 subunits, decreased currents evoked by depolarization. Three other Kv1 family toxins that lack a high affinity for Kv1.2 subunits, r-agitoxin-2, dendrotoxin-K, and r-margatoxin, failed to significantly reduce currents, implicating channels with Kv1.2 subunits. RT-PCR results confirmed the expression of Kv1.2 mRNA in identified medium spiny neurons. Currents attributable to Kv1.2 channels activated rapidly, inactivated slowly, and recovered from inactivation slowly. In the subthreshold range (ca. -60 mV), these currents accounted for as much as 50% of the depolarization-activated K(+) current. Moreover, their rapid activation and relatively slow deactivation suggested that they contribute to spike afterpotentials regulating repetitive discharge. This inference was confirmed in current-clamp recordings from medium spiny neurons in the slice preparation where Kv1.2 blockade reduced first-spike latency and increased discharge frequency evoked from hyperpolarized membrane potentials resembling the "down-state" found in vivo. These studies establish a clear functional role for somato-dendritic Kv1.2 channels in the regulation of state transitions and repetitive discharge in striatal medium spiny neurons.
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Affiliation(s)
- Weixing Shen
- Department of Physiology and Institute for Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
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Kretschmer T, Nguyen DH, Beuerman RW, Happel LT, England JD, Tiel RL, Kline DG. Painful neuromas: a potential role for a structural transmembrane protein, ankyrin G. J Neurosurg 2002; 97:1424-31. [PMID: 12507143 DOI: 10.3171/jns.2002.97.6.1424] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
OBJECT Severe nerve injury induces the formation of a neuroma. Some neuromas cause excruciating pain. Overexpression of Na+ channels leads to hyperexcitability and painful phenomena. Ankyrin G, a multifunctional transmembrane protein of the axolemma, might be a key protein in neuroma formation because it binds Na+ channels in the initial segments of a regenerating axon and links with neuronal cell adhesion molecules. The authors wanted to determine if ankyrin G could be detected in neuroma, and if present, whether there would be differences in distribution between nonpainful neuromas, painful neuromas, and normal nerve. METHODS First, frozen sections of nine nerve specimens obtained from six patients (six nonpainful neuromas, one painful neuroma, and two normal nerves) were immunocytochemically screened for ankyrin G by using confocal laser scanning microscopy. Second, specimens from 29 patients (seven painful neuromas, 15 nonpainful neuromas, and seven normal nerves) were examined using immunoblot analysis for their ankyrin G content. Western blot analysis detected ankyrin G, which was visualized by applying the enhanced chemiluminescence technique. Computerized densitometry was used to quantitate ankyrin G expression by comparing band intensities. Normal nerve served as control. Neurofilament was used as a marker for nerve tissue content. Ankyrin G could be detected and was found to be increased in neuromas. The mean band intensity values were 1838 for painful neuromas, 1166 for nonpainful neuromas, and 411 for normal nerves. In two cases the authors were able to compare specimens of painful neuroma and normal nerve from the same patient. The painful neuromas exhibited considerably higher levels of ankyrin G. Painful neuroma and normal nerve densitometry values were 499 and 165, respectively, for one patient, and 4254 and 821, respectively, for the other patient. Painful neuromas were also found to have higher neurofilament values than nonpainful neuromas. CONCLUSIONS Altered regulation of ankyrin G after nerve injury may lead to hyperexcitability and painful phenomena via clustering of Na+ channels. A propensity to overexpress ankyrin G after peripheral nerve trauma may turn out to be a factor in the development of painful neuromas and neuropathic pain. The relevant literature regarding the importance of ankyrin G for nerve regeneration and nerve membrane remodeling is reviewed.
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Affiliation(s)
- Thomas Kretschmer
- Center for Neuroscience, Louisiana State University Health Science Center, New Orleans, Louisiana, USA.
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Kretschmer T, England JD, Happel LT, Liu ZP, Thouron CL, Nguyen DH, Beuerman RW, Kline DG. Ankyrin G and voltage gated sodium channels colocalize in human neuroma--key proteins of membrane remodeling after axonal injury. Neurosci Lett 2002; 323:151-5. [PMID: 11950515 DOI: 10.1016/s0304-3940(02)00021-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
We tested if ankyrin G could be detected in human neuroma, if it colocalized with site-specific peripheral nerve sodium channels that accumulate at axon tips of injured nerve, and if there are differences in the distribution of these proteins in non-painful neuroma and painful neuroma tissue vs. normal nerve. Frozen sections from one painful, six non-painful, and three normal nerves were immunocytochemically examined. A double labeling technique with highly specific antibodies against peripheral nerve type 1 (Na(v)1.7), and peripheral nerve type 3 (Na(v)1.8) sodium channels and anti-ankyrin G antibodies detected sodium channels and ankyrin G on the same section, using confocal laser scanning microscopy. Ankyrin G colocalized with both types of sodium channels. Neuroma specimens exhibited considerably larger immunofluorescence for both sodium channels and ankyrin G compared with normal nerve. The painful neuroma presented an even more pronounced immunolabeling in clusters. Findings support results from animal models that link ankyrin G with clustering of sodium channels at axon tips of unmyelinated, sprouting fibers. A common (repair-) mechanism that exists throughout the human nervous system for clustering sodium channels at a high density is assumed. A dysregulation in this membrane remodeling mechanism might be an initial step in a cascade that leads to a painful rather than a non-painful neuroma.
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Affiliation(s)
- Thomas Kretschmer
- Department of Neurosurgery, University of Ulm, BKH Neurochirurgie, Ludwig-Heilmeyer-Strasse 2, D-89312 Günzburg, Germany.
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