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Celen MC, Akkoca A, Tuncer S, Dalkilic N, Ilhan B. Protective vs. Therapeutic Effects of Mitochondria-Targeted Antioxidant MitoTEMPO on Rat Sciatic Nerve Crush Injury: A Comprehensive Electrophysiological Analysis. Biomedicines 2023; 11:3306. [PMID: 38137528 PMCID: PMC10741406 DOI: 10.3390/biomedicines11123306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Revised: 12/08/2023] [Accepted: 12/12/2023] [Indexed: 12/24/2023] Open
Abstract
Protective vs. Therapeutic Effects of Mitochondria-Targeted Antioxidant MitoTEMPO on Rat Sciatic Nerve Crush Injury: A Comprehensive Electrophysiological Analysis. Peripheral nerve injuries often result in long-lasting functional deficits, prompting the need for effective interventions. MitoTEMPO (2-(2,2,6,6-tetramethylpiperidin-1-oxyl-4-ylamino)-2-oxoethyl) triphenylphosphonium chloride) is a mitochondria-targeted antioxidant that has shown protective and therapeutic effects against pathologies associated with reactive oxygen species. This study explores the utilization of MitoTEMPO as a therapeutic and protective agent for sciatic nerve crush injuries. By employing advanced mathematical approaches, the study seeks to comprehensively analyze nerve conduction parameters, nerve excitability, and the distribution of nerve conduction velocities to gauge the potential. Forty Wistar-Albino rats were randomly divided into following groups: (I) SHAM-animals subjected to sham operation and treated intraperitoneally (i.p.) with vehicle (bidistilled water) for 14 days; (II) CI (crush injury)-animals subjected to CI and treated with vehicle 14 days; (III) MiP-animals subjected to 7 days i.p. MitoTEMPO treatment before CI (0.7 mg/kg/day dissolved in vehicle) and, only vehicle for 7 days after CI, protective MitoTEMPO; and (IV) MiT-animals i.p. treated with only vehicle for 7 days before CI and 7 days with MitoTEMPO (0.7 mg/kg/day dissolved in vehicle) after CI, therapeutic MitoTEMPO. Nerve excitability parameters were measured, including rheobase and chronaxie, along with compound action potential (CAP) recordings. Advanced mathematical analyses were applied to CAP recordings to determine nerve conduction velocities and distribution patterns. The study revealed significant differences in nerve excitability parameters between groups. Nerve conduction velocity was notably reduced in the MiP and CI groups, whereas CAP area values were diminished in the MiP and CI groups compared to the MiT group. Furthermore, CAP velocity was lower in the MiP and CI groups, and maximum depolarization values were markedly lower in the MiP and CI groups compared to the SHAM group. The distribution of nerve conduction velocities indicated alterations in the composition of nerve fiber groups following crush injuries. In conclusion, postoperative MitoTEMPO administration demonstrated promising results in mitigating the detrimental effects of nerve crush injuries.
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Affiliation(s)
- Murat Cenk Celen
- Department of Biophysics, Faculty of Medicine, Ankara Medipol University, 06570 Ankara, Türkiye
| | - Ahmet Akkoca
- Department of Occupational Health and Safety, Taskent Vocational School, Selcuk University, 42960 Konya, Türkiye
| | - Seckin Tuncer
- Department of Biophysics, Faculty of Medicine, Eskisehir Osmangazi University, 26040 Eskisehir, Türkiye
| | - Nizamettin Dalkilic
- Department of Biophysics, Faculty of Medicine, Baskent University, 06490 Ankara, Türkiye
| | - Barkin Ilhan
- Department of Biophysics, Meram School of Medicine, Necmettin Erbakan University, 42090 Konya, Türkiye
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Pia H, Nochi Z, Kristensen AG, Pelz B, Goetz M, Hoeink JN, Blockeel AJ, Mouraux A, Truini A, Finnerup NB, Phillips KG, Treede RD, Tankisi H. The test–retest reliability of large and small fiber nerve excitability testing with threshold tracking. Clin Neurophysiol Pract 2023; 8:71-78. [PMID: 37181417 PMCID: PMC10172996 DOI: 10.1016/j.cnp.2023.03.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 03/08/2023] [Accepted: 03/26/2023] [Indexed: 04/09/2023] Open
Abstract
Objective Standard nerve excitability testing (NET) predominantly assesses Aα- and Aβ-fiber function, but a method examining small afferents would be of great interest in pain studies. Here, we examined the properties of a novel perception threshold tracking (PTT) method that preferentially activates Aδ-fibers using weak currents delivered by a novel multipin electrode and compared its reliability with NET. Methods Eighteen healthy subjects (mean age:34.06 ± 2.0) were examined three times with motor and sensory NET and PTT in morning and afternoon sessions on the same day (intra-day reliability) and after a week (inter-day reliability). NET was performed on the median nerve, while PTT stimuli were delivered through a multipin electrode located on the forearm. During PTT, subjects indicated stimulus perception via a button press and the intensity of the current was automatically increased or decreased accordingly by Qtrac software. This allowed changes in the perception threshold to be tracked during strength-duration time constant (SDTC) and threshold electrotonus protocols. Results The coefficient of variation (CoV) and interclass coefficient of variation (ICC) showed good-excellent reliability for most NET parameters. PTT showed poor reliability for both SDTC and threshold electrotonus parameters. There was a significant correlation between large (sensory NET) and small (PTT) fiber SDTC when all sessions were pooled (r = 0.29, p = 0.03). Conclusions Threshold tracking technique can be applied directly to small fibers via a psychophysical readout, but with the current technique, the reliability is poor. Significance Further studies are needed to examine whether Aβ-fiber SDTC may be a surrogate biomarker for peripheral nociceptive signalling.
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Buccino AP, Yuan X, Emmenegger V, Xue X, Gänswein T, Hierlemann A. An automated method for precise axon reconstruction from recordings of high-density micro-electrode arrays. J Neural Eng 2022; 19. [PMID: 35234667 PMCID: PMC7612575 DOI: 10.1088/1741-2552/ac59a2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Accepted: 03/01/2022] [Indexed: 11/13/2022]
Abstract
Objective Neurons communicate with each other by sending action potentials through their axons. The velocity of axonal signal propagation describes how fast electrical action potentials can travel. This velocity can be affected in a human brain by several pathologies, including multiple sclerosis, traumatic brain injury and channelopathies. High-density microelectrode arrays (HD-MEAs) provide unprecedented spatio-temporal resolution to extracellularly record neural electrical activity. The high density of the recording electrodes enables to image the activity of individual neurons down to subcellular resolution, which includes the propagation of axonal signals. However, axon reconstruction, to date, mainly relies on manual approaches to select the electrodes and channels that seemingly record the signals along a specific axon, while an automated approach to track multiple axonal branches in extracellular action-potential recordings is still missing. Approach In this article, we propose a fully automated approach to reconstruct axons from extracellular electrical-potential landscapes, so-called “electrical footprints” of neurons. After an initial electrode and channel selection, the proposed method first constructs a graph based on the voltage signal amplitudes and latencies. Then, the graph is interrogated to extract possible axonal branches. Finally, the axonal branches are pruned, and axonal action-potential propagation velocities are computed. Main results We first validate our method using simulated data from detailed reconstructions of neurons, showing that our approach is capable of accurately reconstructing axonal branches. We then apply the reconstruction algorithm to experimental recordings of HD-MEAs and show that it can be used to determine axonal morphologies and signal-propagation velocities at high throughput. Significance We introduce a fully automated method to reconstruct axonal branches and estimate axonal action-potential propagation velocities using HD-MEA recordings. Our method yields highly reliable and reproducible velocity estimations, which constitute an important electrophysiological feature of neuronal preparations.
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Affiliation(s)
| | - Xinyue Yuan
- D-BSSE, ETH Zürich, Basel, Zurich, 8092, SWITZERLAND
| | | | - Xiaohan Xue
- D-BSSE, ETH Zürich, Basel, Zurich, 8092, SWITZERLAND
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Nochi Z, Pia H, Bloms-Funke P, Boesl I, Caspani O, Chapman SC, Fardo F, Genser B, Goetz M, Kostenko AV, Leone C, Li T, Mouraux A, Pelz B, Pogatzki-Zahn E, Schilder A, Schnetter E, Schubart K, Stouffs A, Tracey I, Troconiz IF, Truini A, Van Niel J, Vela JM, Vincent K, Vollert J, Wanigasekera V, Wittayer M, Tankisi H, Finnerup NB, Phillips KG, Treede RD. IMI2-PainCare-BioPain-RCT1: study protocol for a randomized, double-blind, placebo-controlled, crossover, multi-center trial in healthy subjects to investigate the effects of lacosamide, pregabalin, and tapentadol on biomarkers of pain processing observed by peripheral nerve excitability testing (NET). Trials 2022; 23:163. [PMID: 35183242 PMCID: PMC8857873 DOI: 10.1186/s13063-022-06087-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Accepted: 02/05/2022] [Indexed: 12/12/2022] Open
Abstract
Abstract
Background
Few new drugs have been developed for chronic pain. Drug development is challenged by uncertainty about whether the drug engages the human target sufficiently to have a meaningful pharmacodynamic effect. IMI2-PainCare-BioPain-RCT1 is one of four similarly designed studies that aim to link different functional biomarkers of drug effects on the nociceptive system that could serve to accelerate the future development of analgesics. This study focusses on biomarkers derived from nerve excitability testing (NET) using threshold tracking of the peripheral nervous system.
Methods
This is a multisite single-dose, subject and assessor-blind, randomized, placebo-controlled, 4-period, 4-way crossover, pharmacodynamic (PD), and pharmacokinetic (PK) study in healthy subjects. Biomarkers derived from NET of large sensory and motor fibers and small sensory fibers using perception threshold tracking will be obtained before and three times after administration of three medications known to act on the nociceptive system (lacosamide, pregabalin, tapentadol) and placebo, given as a single oral dose with at least 1 week apart. Motor and sensory NET will be assessed on the right wrist in a non-sensitized normal condition while perception threshold tracking will be performed bilaterally on both non-sensitized and sensitized forearm skin. Cutaneous high-frequency electrical stimulation is used to induce hyperalgesia. Blood samples will be taken for pharmacokinetic purposes and pain ratings as well as predictive psychological traits will be collected. A sequentially rejective multiple testing approach will be used with overall alpha error of the primary analysis split across the two primary outcomes: strength-duration time constant (SDTC; a measure of passive membrane properties and nodal persistent Na+ conductance) of large sensory fibers and SDTC of large motor fibers comparing lacosamide and placebo. The key secondary endpoint is the SDTC measured in small sensory fibers. Remaining treatment arm effects on key NET outcomes and PK modelling are other prespecified secondary or exploratory analyses.
Discussion
Measurements of NET using threshold tracking protocols are sensitive to membrane potential at the site of stimulation. Sets of useful indices of axonal excitability collectively may provide insights into the mechanisms responsible for membrane polarization, ion channel function, and activity of ionic pumps during the process of impulse conduction. IMI2-PainCare-BioPain-RCT1 hypothesizes that NET can serve as biomarkers of target engagement of analgesic drugs in this compartment of the nociceptive system for future Phase 1 clinical trials. Phase 2 and 3 clinical trials could also benefit from these tools for patient stratification.
Trial registration
This trial was registered 25/06/2019 in EudraCT (2019-000942-36).
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The additional diagnostic value of motor nerve excitability testing in chronic axonal neuropathy. Clin Neurophysiol Pract 2022; 7:27-33. [PMID: 35128215 PMCID: PMC8803553 DOI: 10.1016/j.cnp.2021.12.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 12/23/2021] [Accepted: 12/27/2021] [Indexed: 11/29/2022] Open
Abstract
Nerve excitability testing was correlated with conventional nerve conduction studies. Nerve excitability testing was similar in patients with and without neuropathy and normal nerve conduction. There is no support for the potential additional diagnostic value of nerve excitability testing in mixed etiology neuropathy.
Objective To explore potential differences in motor nerve excitability testing (NET) variables at group levels between patients with a clinical diagnosis of polyneuropathy (PNP), which did not fulfil diagnostic criteria of conventional nerve conduction studies (NCS) and patients without polyneuropathy. Such differences could support a role for NET in increasing the diagnostic sensitivity of NCS in chronic axonal PNP. Methods Motor NET was performed using the median nerve in patients with a clinical suspicion of PNP in addition to conventional NCS, skin biopsies, corneal confocal microscopy and structured clinical evaluation including scoring of neuropathy symptoms and signs. Results Of the 57 patients included, 32 had PNP, half of which had NCS, which fulfilled criteria for PNP (NCS+ PNP). There were no significant differences for any of the NET variables between PNP patients with non-diagnostic conventional NCS (NCS− PNP) and patients without PNP. Rheobase was increased, and Ted (undershoot) and subexcitability were decreased in NCS+ PNP. Sural amplitude, peroneal nerve F-wave latency and tibial nerve F-wave-latency were correlated with subexcitability, and tibial nerve motor amplitude was correlated with rheobase. Conclusions NET was correlated with conventional NCS and no differences were found between NCS− PNP patients and patients without PNP. Significance NET does not seem to offer any additional diagnostic value in chronic mixed etiology neuropathy.
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Moldovan M, Pisciotta C, Pareyson D, Krarup C. Myelin protein zero gene dose dependent axonal ion-channel dysfunction in a family with Charcot-Marie-Tooth disease. Clin Neurophysiol 2020; 131:2440-2451. [PMID: 32829291 DOI: 10.1016/j.clinph.2020.06.034] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 05/29/2020] [Accepted: 06/28/2020] [Indexed: 11/28/2022]
Abstract
OBJECTIVE The myelin impairment in demyelinating Charcot-Marie-Tooth (CMT) disease leads to various degrees of axonal degeneration, the ultimate cause of disability. We aimed to assess the pathophysiological changes in axonal function related to the neuropathy severity in hypo-/demyelinating CMT patients associated with myelin protein zero gene (MPZ) deficiency. METHODS We investigated four family members (two parents and two sons) harboring a frameshift mutation (c.306delA, p.Asp104ThrfsTer14) in the MPZ gene, predicted to result in a nonfunctional P0, by conventional conduction studies and multiple measures of motor axon excitability. In addition to the conventional excitability studies of the median nerve at the wrist, we tested the spinal accessory nerves. Control measures were obtained from 14 healthy volunteers. RESULTS The heterozygous parents (aged 56 and 63) had a mild CMT1B whereas their two homozygous sons (aged 31 and 39 years) had a severe Dejerine-Sottas disease phenotype. The spinal accessory nerve excitability could be measured in all patients. The sons showed reduced deviations during depolarizing threshold electrotonus and other depolarizing features which were not apparent in the accessory and median nerve studies of the parents. Mathematical modeling indicated impairment in voltage-gated sodium channels. This interpretation was supported by comparative modeling of excitability measurements in MPZ deficient mice. CONCLUSION Our data suggest that axonal depolarization in the context of abnormal voltage-gated sodium channels precedes axonal degeneration in severely hypo-/demyelinating CMT as previously reported in the mouse models. SIGNIFICANCE Measures of the accessory nerve excitability could provide pathophysiological markers of neurotoxicity in severe demyelinating neuropathies.
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Affiliation(s)
- Mihai Moldovan
- Department of Neuroscience, University of Copenhagen, Denmark; Department of Clinical Neurophysiology, Rigshospitalet, Copenhagen, Denmark
| | - Chiara Pisciotta
- Unit of Rare Neurodegenerative and Neurometabolic Diseases, Department of Clinical Neurosciences, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Davide Pareyson
- Unit of Rare Neurodegenerative and Neurometabolic Diseases, Department of Clinical Neurosciences, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Christian Krarup
- Department of Neuroscience, University of Copenhagen, Denmark; Department of Clinical Neurophysiology, Rigshospitalet, Copenhagen, Denmark.
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Blackband SJ, Flint JJ, Hansen B, Shepherd TM, Lee CH, Streit WJ, Forder JR. On the Origins of Diffusion MRI Signal Changes in Stroke. Front Neurol 2020; 11:549. [PMID: 32714267 PMCID: PMC7344185 DOI: 10.3389/fneur.2020.00549] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Accepted: 05/15/2020] [Indexed: 12/20/2022] Open
Abstract
Magnetic resonance imaging (MRI) is a leading diagnostic technique especially for neurological studies. However, the physical origin of the hyperintense signal seen in MR images of stroke immediately after ischemic onset in the brain has been a matter of debate since it was first demonstrated in 1990. In this article, we hypothesize and provide evidence that changes in the glial cells, comprising roughly one-half of the brain's cells and therefore a significant share of its volume, accompanying ischemia, are the root cause of the MRI signal change. Indeed, a primary function of the glial cells is osmoregulation in order to maintain homeostasis in the neurons and nerve fibers for accurate and consistent function. This realization also impacts our understanding of signal changes in other tissues following ischemia. We anticipate that this paradigm shift will facilitate new and improved models of MRI signals in tissues, which will, in turn, impact clinical utility.
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Affiliation(s)
- Stephen J Blackband
- Department of Neuroscience, University of Florida, Gainesville, FL, United States.,McKnight Brain Institute, University of Florida, Gainesville, FL, United States.,Center for Structural Biology, University of Florida, Gainesville, FL, United States.,National High Magnetic Field Laboratory, Tallahassee, FL, United States
| | - Jeremy J Flint
- Department of Neuroscience, University of Florida, Gainesville, FL, United States.,McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Brian Hansen
- Center of Functionally Integrative Neuroscience, Aarhus University, Aarhus, Denmark
| | - Timothy M Shepherd
- Department of Radiology, New York University School of Medicine, New York, NY, United States
| | - Choong H Lee
- Department of Radiology, New York University School of Medicine, New York, NY, United States
| | - Wolfgang J Streit
- Department of Neuroscience, University of Florida, Gainesville, FL, United States
| | - John R Forder
- McKnight Brain Institute, University of Florida, Gainesville, FL, United States.,National High Magnetic Field Laboratory, Tallahassee, FL, United States.,Department of Biomedical Engineering, University of Florida, Gainesville, FL, United States.,Department of Radiology, University of Florida, Gainesville, FL, United States
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Moldovan M. Threshold tracking as a tool to study activity-dependent axonal plasticity. Clin Neurophysiol 2020; 131:1381-1382. [PMID: 32224021 DOI: 10.1016/j.clinph.2020.03.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 03/10/2020] [Indexed: 11/26/2022]
Affiliation(s)
- Mihai Moldovan
- Department of Clinical Neurophysiology, Rigshospitalet, Copenhagen, Denmark; Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark.
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Issar T, Arnold R, Kwai NCG, Walker S, Yan A, Borire AA, Poynten AM, Pussell BA, Endre ZH, Kiernan MC, Krishnan AV. Relative contributions of diabetes and chronic kidney disease to neuropathy development in diabetic nephropathy patients. Clin Neurophysiol 2019; 130:2088-2095. [PMID: 31541986 DOI: 10.1016/j.clinph.2019.08.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 07/04/2019] [Accepted: 08/12/2019] [Indexed: 12/12/2022]
Abstract
OBJECTIVE Chronic kidney disease (CKD) caused by diabetes is known as diabetic kidney disease (DKD). The present study aimed to examine the underlying mechanisms of axonal dysfunction and features of neuropathy in DKD compared to CKD and type 2 diabetes (T2DM) alone. METHODS Patients with DKD (n = 30), CKD (n = 28) or T2DM (n = 40) and healthy controls (n = 41) underwent nerve excitability assessments to examine axonal function. Neuropathy was assessed using the Total Neuropathy Score. A validated mathematical model of human axons was utilised to provide an indication of the underlying causes of nerve pathophysiology. RESULTS Total neuropathy score was significantly higher in patients with DKD compared to those with either CKD or T2DM (p < 0.05). In DKD, nerve excitability measures (S2 accommodation and superexcitability, p < 0.05) were more severely affected compared to both CKD and T2DM and worsened with increasing serum K+ (p < 0.01). Mathematical modelling indicated the basis for nerve dysfunction in DKD was an elevation of extracellular K+ and reductions in Na+ permeability and the hyperpolarisation-activated cation current, which was similar to CKD. CONCLUSIONS Patients with DKD manifested a more severe neuropathy phenotype and shared features of nerve dysfunction to that of CKD. SIGNIFICANCE The CKD, and not diabetes component, appears to underlie axonal pathophysiology in DKD.
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Affiliation(s)
- Tushar Issar
- Prince of Wales Clinical School, UNSW Sydney, NSW 2031, Australia
| | - Ria Arnold
- School of Medical Sciences, UNSW Sydney, NSW 2052, Australia
| | - Natalie C G Kwai
- Prince of Wales Clinical School, UNSW Sydney, NSW 2031, Australia; Department of Exercise Physiology, UNSW Sydney, NSW 2052, Australia
| | - Susan Walker
- Prince of Wales Clinical School, UNSW Sydney, NSW 2031, Australia
| | - Aimy Yan
- Prince of Wales Clinical School, UNSW Sydney, NSW 2031, Australia
| | - Adeniyi A Borire
- Prince of Wales Clinical School, UNSW Sydney, NSW 2031, Australia
| | - Ann M Poynten
- Department of Endocrinology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Bruce A Pussell
- Department of Nephrology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Zoltan H Endre
- Department of Nephrology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Matthew C Kiernan
- Brain and Mind Centre, University of Sydney and Royal Prince Alfred Hospital, Sydney, NSW 2050, Australia
| | - Arun V Krishnan
- Prince of Wales Clinical School, UNSW Sydney, NSW 2031, Australia.
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Kiernan MC, Bostock H, Park SB, Kaji R, Krarup C, Krishnan AV, Kuwabara S, Lin CSY, Misawa S, Moldovan M, Sung J, Vucic S, Wainger BJ, Waxman S, Burke D. Measurement of axonal excitability: Consensus guidelines. Clin Neurophysiol 2019; 131:308-323. [PMID: 31471200 DOI: 10.1016/j.clinph.2019.07.023] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 07/17/2019] [Accepted: 07/24/2019] [Indexed: 12/12/2022]
Abstract
Measurement of axonal excitability provides an in vivo indication of the properties of the nerve membrane and of the ion channels expressed on these axons. Axonal excitability techniques have been utilised to investigate the pathophysiological mechanisms underlying neurological diseases. This document presents guidelines derived for such studies, based on a consensus of international experts, and highlights the potential difficulties when interpreting abnormalities in diseased axons. The present manuscript provides a state-of-the-art review of the findings of axonal excitability studies and their interpretation, in addition to suggesting guidelines for the optimal performance of excitability studies.
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Affiliation(s)
- Matthew C Kiernan
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney 2006, Australia.
| | - Hugh Bostock
- UCL Queen Square Institute of Neurology, London WC1N 3BG, United Kingdom
| | - Susanna B Park
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney 2006, Australia
| | - Ryuji Kaji
- National Utano Hospital, 8-Narutaki Ondoyamacho, Ukyoku, Kyoto 616-8255, Japan
| | - Christian Krarup
- Department of Neuroscience, University of Copenhagen and Department of Clinical Neurophysiology, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark
| | - Arun V Krishnan
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - Satoshi Kuwabara
- Department of Neurology, Graduate School of Medicine, Chiba University, Japan
| | - Cindy Shin-Yi Lin
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney 2006, Australia
| | - Sonoko Misawa
- Department of Neurology, Graduate School of Medicine, Chiba University, Japan
| | - Mihai Moldovan
- Department of Neuroscience, University of Copenhagen and Department of Clinical Neurophysiology, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark
| | - Jiaying Sung
- Taipei Medical University, Wanfang Hospital, Taipei, Taiwan
| | - Steve Vucic
- Department of Neurology, Westmead Hospital, Western Clinical School, University of Sydney, Australia
| | - Brian J Wainger
- Department of Neurology and Anesthesiology, Critical Care & Pain Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Stephen Waxman
- Department of Neurology, Yale Medical School, New Haven, CT 06510, USA; Neurorehabilitation Research Center, Veterans Affairs Hospital, West Haven, CT 06516, USA
| | - David Burke
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney 2006, Australia
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Emmenegger V, Obien MEJ, Franke F, Hierlemann A. Technologies to Study Action Potential Propagation With a Focus on HD-MEAs. Front Cell Neurosci 2019; 13:159. [PMID: 31118887 PMCID: PMC6504789 DOI: 10.3389/fncel.2019.00159] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 04/08/2019] [Indexed: 12/26/2022] Open
Abstract
Axons convey information in neuronal circuits via reliable conduction of action potentials (APs) from the axon initial segment (AIS) to the presynaptic terminals. Recent experimental findings increasingly evidence that the axonal function is not limited to the simple transmission of APs. Advances in subcellular-resolution recording techniques have shown that axons display activity-dependent modulation in spike shape and conduction velocity, which influence synaptic strength and latency. We briefly review here, how recent methodological developments facilitate the understanding of the axon physiology. We included the three most common methods, i.e., genetically encoded voltage imaging (GEVI), subcellular patch-clamp and high-density microelectrode arrays (HD-MEAs). We then describe the potential of using HD-MEAs in studying axonal physiology in more detail. Due to their robustness, amenability to high-throughput and high spatiotemporal resolution, HD-MEAs can provide a direct functional electrical readout of single cells and cellular ensembles at subcellular resolution. HD-MEAs can, therefore, be employed in investigating axonal pathologies, the effects of large-scale genomic interventions (e.g., with RNAi or CRISPR) or in compound screenings. A combination of extracellular microelectrode arrays (MEAs), intracellular microelectrodes and optical imaging may potentially reveal yet unexplored repertoires of axonal functions.
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Affiliation(s)
- Vishalini Emmenegger
- Department of Biosystems Science and Engineering, ETH Zürich, Basel, Switzerland
| | - Marie Engelene J. Obien
- Department of Biosystems Science and Engineering, ETH Zürich, Basel, Switzerland
- MaxWell Biosystems AG, Basel, Switzerland
| | - Felix Franke
- Department of Biosystems Science and Engineering, ETH Zürich, Basel, Switzerland
| | - Andreas Hierlemann
- Department of Biosystems Science and Engineering, ETH Zürich, Basel, Switzerland
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Czesnik D, Howells J, Bartl M, Veiz E, Ketzler R, Kemmet O, Walters AS, Trenkwalder C, Burke D, Paulus W. I h contributes to increased motoneuron excitability in restless legs syndrome. J Physiol 2018; 597:599-609. [PMID: 30430565 DOI: 10.1113/jp275341] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Accepted: 10/18/2018] [Indexed: 12/17/2022] Open
Abstract
KEY POINTS Restless legs patients complain about sensory and motor symptoms leading to sleep disturbances. Symptoms include painful sensations, an urge to move and involuntary leg movements. The responsible mechanisms of restless legs syndrome are still not known, although current studies indicate an increased neuronal network excitability. Reflex studies indicate the involvement of spinal structures. Peripheral mechanisms have not been investigated so far. In the present study, we provide evidence of increased hyperpolarization-activated cyclic nucleotide-gated (HCN) channel-mediated inward rectification in motor axons. The excitability of sensory axons was not changed. We conclude that, in restless legs syndrome, an increased HCN current in motoneurons may play a pathophysiological role, such that these channels could represent a valuable target for pharmaceutical intervention. ABSTRACT Restless legs syndrome is a sensorimotor network disorder. So far, the responsible pathophysiological mechanisms are poorly understood. In the present study, we provide evidence that the excitability of peripheral motoneurons contributes to the pathophysiology of restless legs syndrome. In vivo excitability studies on motor and sensory axons of the median nerve were performed on patients with idiopathic restless legs syndrome (iRLS) who were not currently on treatment. The iRLS patients had greater accommodation in motor but not sensory axons to long-lasting hyperpolarization compared to age-matched healthy subjects, indicating greater inward rectification in iRLS. The most reasonable explanation is that hyperpolarization-activated cyclic nucleotide-gated (HCN) channels open at less hyperpolarized membrane potentials, a view supported by mathematical modelling. The half-activation potential for HCN channels (Bq) was the single best parameter that accounted for the difference between normal controls and iRLS data. A 6 mV depolarization of Bq reduced the discrepancy between the normal control model and the iRLS data by 92.1%. Taken together, our results suggest an increase in the excitability of motor units in iRLS that could enhance the likelihood of leg movements. The abnormal axonal properties are consistent with other findings indicating that the peripheral system is part of the network involved in iRLS.
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Affiliation(s)
- Dirk Czesnik
- Department of Clinical Neurophysiology, Medical School Göttingen, University of Göttingen, Göttingen, Germany
| | - James Howells
- Brain & Mind Centre, The University of Sydney, Sydney, NSW, Australia
| | - Michael Bartl
- Department of Clinical Neurophysiology, Medical School Göttingen, University of Göttingen, Göttingen, Germany
| | - Elisabeth Veiz
- Department of Clinical Neurophysiology, Medical School Göttingen, University of Göttingen, Göttingen, Germany
| | - Rebecca Ketzler
- Department of Clinical Neurophysiology, Medical School Göttingen, University of Göttingen, Göttingen, Germany
| | - Olga Kemmet
- Department of Clinical Neurophysiology, Medical School Göttingen, University of Göttingen, Göttingen, Germany
| | - Arthur S Walters
- Division of Sleep Medicine, School of Medicine, Medical Center North, Vanderbilt University, Nashville, TN, USA
| | - Claudia Trenkwalder
- Clinic of Neurosurgery, University Medical Center, Paracelsus Klinik Kassel, Göttingen, Germany
| | - David Burke
- Royal Prince Alfred Hospital and The University of Sydney, Sydney, NSW, Australia
| | - Walter Paulus
- Department of Clinical Neurophysiology, Medical School Göttingen, University of Göttingen, Göttingen, Germany
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Matamala JM, Howells J, Dharmadasa T, Huynh W, Park SB, Burke D, Kiernan MC. Excitability of sensory axons in amyotrophic lateral sclerosis. Clin Neurophysiol 2018; 129:1472-1478. [PMID: 29661595 DOI: 10.1016/j.clinph.2018.03.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 02/22/2018] [Accepted: 03/11/2018] [Indexed: 12/11/2022]
Abstract
OBJECTIVE To evaluate the excitability of sensory axons in patients with amyotrophic lateral sclerosis (ALS). METHODS Comprehensive sensory nerve excitability studies were prospectively performed on 28 sporadic ALS patients, compared to age-matched controls. Sensory nerve action potentials were recorded from digit 2 following median nerve stimulation at the wrist. Disease severity was measured using motor unit number estimation (MUNE), the revised ALS Functional Rating Scale (ALSFRS-R) and the MRC scale. RESULTS There were no significant differences in standard and extended measures of nerve excitability between ALS patients and controls. These unchanged excitability measures included accommodation to long-lasting hyperpolarization and the threshold changes after two supramaximal stimuli during the recovery cycle. Excitability parameters did not correlate with MUNE, ALSFRS-R, APB MRC scale or disease duration. CONCLUSIONS This cross-sectional study has identified normal axonal membrane properties in myelinated sensory axons of ALS patients. Previously described sensory abnormalities could be the result of axonal fallout, possibly due to a ganglionopathy, or to involvement of central sensory pathways rostral to gracile and cuneate nuclei. SIGNIFICANCE These results demonstrate the absence of generalized dysfunction of the membrane properties of sensory axons in ALS in the face of substantial deficits in motor function.
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Affiliation(s)
| | - James Howells
- Brain and Mind Centre, University of Sydney, Sydney, NSW 2050, Australia
| | - Thanuja Dharmadasa
- Brain and Mind Centre, University of Sydney, Sydney, NSW 2050, Australia
| | - William Huynh
- Brain and Mind Centre, University of Sydney, Sydney, NSW 2050, Australia
| | - Susanna B Park
- Brain and Mind Centre, University of Sydney, Sydney, NSW 2050, Australia
| | - David Burke
- Sydney Medical School, University of Sydney, Sydney, NSW 2006, Australia; Department of Neurology, Royal Prince Alfred Hospital, Sydney, NSW 2050, Australia
| | - Matthew C Kiernan
- Brain and Mind Centre, University of Sydney, Sydney, NSW 2050, Australia; Sydney Medical School, University of Sydney, Sydney, NSW 2006, Australia; Department of Neurology, Royal Prince Alfred Hospital, Sydney, NSW 2050, Australia
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Howells J, Bostock H, Park SB, Kiernan MC, Burke D. Tracking small sensory nerve action potentials in human axonal excitability studies. J Neurosci Methods 2018; 298:45-53. [DOI: 10.1016/j.jneumeth.2018.02.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 01/08/2018] [Accepted: 02/08/2018] [Indexed: 10/18/2022]
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Gajda GB, Bly SH. Magnetic Field Reference Levels for Arbitrary Periodic Waveforms for Prevention of Peripheral Nerve Stimulation. HEALTH PHYSICS 2017; 112:501-511. [PMID: 28441282 DOI: 10.1097/hp.0000000000000663] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Guidelines for prevention of peripheral nerve stimulation from exposure to low frequency magnetic fields have been developed by standard-setting bodies. Exposure limits or reference levels (RLs) are typically set in terms of the maximum root-mean-square amplitude of a sinusoidal waveform; however, environmental flux densities are often periodic, non-sinusoidal waveforms. This work presents a procedure for deriving RLs for any generalized periodic waveform using the empirical nerve-stimulation threshold data obtained from human volunteer MRI experiments. For this purpose, the "Law of Electrostimulation" (LOE), which sets forth conditions of a waveform necessary to trigger the action potential required to depolarize cell membranes, is applied to various waveforms. The results of the LOE analysis are waveform-specific, amplitude thresholds of stimulation that are found in terms of the empirically-derived rheobase threshold time-rate-of-change flux density and chronaxie from trapezoidal pulse MRI experiments. The thresholds are converted to amplitude RLs in two asymptotic frequency regimes as per the usual practice in standard setting. The resulting RLs have the same frequency dependence as in existing standards (i.e., inverse-frequency below a transition frequency and flat above). It is shown that the transition frequency is dependent only on the shape of the waveform. Both sinusoidal and non-sinusoidal waveforms have identical peak-to-peak amplitude RLs above their respective transition frequencies. Below these frequencies, all peak-to-peak amplitude RLs have the same functional dependence on frequency when the frequency is normalized to the waveform-specific transition frequency. This results in simple criteria for testing the amplitude of any arbitrary periodic waveform against potential for stimulation. These criteria are compared to guidance given for non-sinusoidal waveforms in the ICNIRP 1 Hz-100 kHz exposure standard.
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Arnold R, Moldovan M, Rosberg MR, Krishnan AV, Morris R, Krarup C. Nerve excitability in the rat forelimb: a technique to improve translational utility. J Neurosci Methods 2017; 275:19-24. [DOI: 10.1016/j.jneumeth.2016.10.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 10/01/2016] [Accepted: 10/18/2016] [Indexed: 01/09/2023]
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17
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KCC3 deficiency-induced disruption of paranodal loops and impairment of axonal excitability in the peripheral nervous system. Neuroscience 2016; 335:91-102. [DOI: 10.1016/j.neuroscience.2016.08.031] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Revised: 08/17/2016] [Accepted: 08/18/2016] [Indexed: 12/15/2022]
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18
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An oral NaV1.8 blocker improves motor function in mice completely deficient of myelin protein P0. Neurosci Lett 2016; 632:33-8. [PMID: 27530546 DOI: 10.1016/j.neulet.2016.08.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 08/11/2016] [Accepted: 08/12/2016] [Indexed: 01/06/2023]
Abstract
Mice deficient of myelin protein P0 are established models of demyelinating Charcot-Marie-Tooth (CMT) disease. Dysmyelination in these mice is associated with an ectopic expression of the sensory neuron specific sodium channel isoform NaV1.8 on motor axons. We reported that in P0+/-, a model of CMT1B, the membrane dysfunction could be acutely improved by a novel oral NaV1.8 blocker referred to as Compound 31 (C31, Bioorg. Med. Chem. Lett. 2010, 20, 6812; AbbVie Inc.). The aim of this study was to investigate the extent to which C31 treatment could also improve the motor axon function in P0-/-, a CMT model with a much more severe neuropathy. We found that the progressive impairment of motor performance from 1 to 4 months of age in P0-/- could be acutely reversed by C31 treatment. The effect was associated with an improvement of the amplitude of the plantar CMAP evoked by tibial nerve stimulation. The corresponding motor nerve excitability studies by "threshold tracking" showed changes after C31 consistent with attenuation of a resting membrane depolarization. Our data suggest that the depolarizing motor conduction failure in P0-/- could be acutely improved by C31. This provides proof-of-concept that treatment with oral subtype-selective NaV1.8 blockers could be used to improve the motor function in severe forms of demyelinating CMT.
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Rosberg MR, Alvarez S, Klein D, Nielsen FC, Martini R, Levinson SR, Krarup C, Moldovan M. Progression of motor axon dysfunction and ectopic Nav1.8 expression in a mouse model of Charcot-Marie-Tooth disease 1B. Neurobiol Dis 2016; 93:201-14. [PMID: 27215377 DOI: 10.1016/j.nbd.2016.05.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Revised: 05/11/2016] [Accepted: 05/18/2016] [Indexed: 12/13/2022] Open
Abstract
Mice heterozygously deficient for the myelin protein P0 gene (P0+/-) develop a slowly progressing neuropathy modeling demyelinating Charcot-Marie-Tooth disease (CMT1B). The aim of the study was to investigate the long-term progression of motor dysfunction in P0+/- mice at 3, 7, 12 and 20months. By comparison with WT littermates, P0+/- showed a decreasing motor performance with age. This was associated with a progressive reduction in amplitude and increase in latency of the plantar compound muscle action potential (CMAP) evoked by stimulation of the tibial nerve at ankle. This progressive functional impairment was in contrast to the mild demyelinating neuropathy of the tibial nerve revealed by histology. "Threshold-tracking" studies showed impaired motor axon excitability in P0+/- from 3months. With time, there was a progressive reduction in threshold deviations during both depolarizing and hyperpolarizing threshold electrotonus associated with increasing resting I/V slope and increasing strength-duration time constant. These depolarizing features in excitability in P0+/- as well as the reduced CMAP amplitude were absent in P0+/- NaV1.8 knockouts, and could be acutely reversed by selective pharmacologic block of NaV1.8 in P0+/-. Mathematical modeling indicated an association of altered passive cable properties with a depolarizing shift in resting membrane potential and increase in the persistent Na(+) current in P0+/-. Our data suggest that ectopic NaV1.8 expression precipitates depolarizing conduction failure in CMT1B, and that motor axon dysfunction in demyelinating neuropathy is pharmacologically reversible.
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Affiliation(s)
- Mette R Rosberg
- Institute of Neuroscience and Pharmacology, University of Copenhagen, Denmark; Department of Clinical Neurophysiology, The Neuroscience Center, Copenhagen University Hospital (Rigshospitalet), Denmark
| | - Susana Alvarez
- Institute of Neuroscience and Pharmacology, University of Copenhagen, Denmark; Department of Clinical Neurophysiology, The Neuroscience Center, Copenhagen University Hospital (Rigshospitalet), Denmark
| | - Dennis Klein
- Neurology, Developmental Neurobiology, University of Würzburg, Germany
| | | | - Rudolf Martini
- Neurology, Developmental Neurobiology, University of Würzburg, Germany
| | - S Rock Levinson
- University of Colorado, Denver, Physiology and Biophysics, United States
| | - Christian Krarup
- Institute of Neuroscience and Pharmacology, University of Copenhagen, Denmark; Department of Clinical Neurophysiology, The Neuroscience Center, Copenhagen University Hospital (Rigshospitalet), Denmark
| | - Mihai Moldovan
- Institute of Neuroscience and Pharmacology, University of Copenhagen, Denmark; Department of Clinical Neurophysiology, The Neuroscience Center, Copenhagen University Hospital (Rigshospitalet), Denmark
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Moldovan M, Rosberg MR, Alvarez S, Klein D, Martini R, Krarup C. Aging-associated changes in motor axon voltage-gated Na + channel function in mice. Neurobiol Aging 2016; 39:128-39. [DOI: 10.1016/j.neurobiolaging.2015.12.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2014] [Revised: 12/13/2015] [Accepted: 12/14/2015] [Indexed: 01/17/2023]
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21
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Moldovan M, Alvarez S, Rosberg MR, Krarup C. Persistent alterations in active and passive electrical membrane properties of regenerated nerve fibers of man and mice. Eur J Neurosci 2015; 43:388-403. [DOI: 10.1111/ejn.13047] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Revised: 07/31/2015] [Accepted: 08/13/2015] [Indexed: 12/12/2022]
Affiliation(s)
- Mihai Moldovan
- Department of Neuroscience and Pharmacology; University of Copenhagen; Copenhagen Denmark
- Department of Clinical Neurophysiology; NF3063 Rigshospitalet 9 Blegdamsvej 2100 Copenhagen Denmark
| | - Susana Alvarez
- Department of Neuroscience and Pharmacology; University of Copenhagen; Copenhagen Denmark
- Department of Clinical Neurophysiology; NF3063 Rigshospitalet 9 Blegdamsvej 2100 Copenhagen Denmark
| | - Mette R. Rosberg
- Department of Neuroscience and Pharmacology; University of Copenhagen; Copenhagen Denmark
- Department of Clinical Neurophysiology; NF3063 Rigshospitalet 9 Blegdamsvej 2100 Copenhagen Denmark
| | - Christian Krarup
- Department of Neuroscience and Pharmacology; University of Copenhagen; Copenhagen Denmark
- Department of Clinical Neurophysiology; NF3063 Rigshospitalet 9 Blegdamsvej 2100 Copenhagen Denmark
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Czesnik D, Howells J, Negro F, Wagenknecht M, Hanner S, Farina D, Burke D, Paulus W. Increased HCN channel driven inward rectification in benign cramp fasciculation syndrome. Brain 2015; 138:3168-79. [DOI: 10.1093/brain/awv254] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 07/08/2015] [Indexed: 12/13/2022] Open
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Lorenz C, Jones KE. IH activity is increased in populations of slow versus fast motor axons of the rat. Front Hum Neurosci 2014; 8:766. [PMID: 25309406 PMCID: PMC4174588 DOI: 10.3389/fnhum.2014.00766] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 09/10/2014] [Indexed: 11/25/2022] Open
Abstract
Much is known about the electrophysiological variation in motoneuron somata across different motor units. However, comparatively less is known about electrophysiological variation in motor axons and how this could impact function or electrodiagnosis in healthy or diseased states. We performed nerve excitability testing on two groups of motor axons in Sprague–Dawley rats that are known to differ significantly in their chronic daily activity patterns and in the relative proportion of motor unit types: one group innervating the soleus (“slow motor axons”) and the other group innervating the tibialis anterior (“fast motor axons”) muscles. We found that slow motor axons have significantly larger accommodation compared to fast motor axons upon application of a 100 ms hyperpolarizing conditioning stimulus that is 40% of axon threshold (Z = 3.24, p = 0.001) or 20% of axon threshold (Z = 2.67, p = 0.008). Slow motor axons had larger accommodation to hyperpolarizing currents in the current-threshold measurement (-80% Z = 3.07, p = 0.002; -90% Z = 2.98, p = 0.003). In addition, we found that slow motor axons have a significantly smaller rheobase than fast motor axons (Z = -1.99, p = 0.047) accompanied by a lower threshold in stimulus-response curves. The results provide evidence that slow motor axons have greater activity of the hyperpolarization-activated inwardly rectifying cation conductance (IH) than fast motor axons. It is possible that this difference between fast and slow axons is caused by an adaptation to their chronic differences in daily activity patterns, and that this adaptation might have a functional effect on the motor unit. Moreover, these findings indicate that slow and fast motor axons may react differently to pathological conditions.
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Affiliation(s)
- Chad Lorenz
- Faculty of Physical Education and Recreation, University of Alberta Edmonton, AB, Canada
| | - Kelvin E Jones
- Faculty of Physical Education and Recreation, University of Alberta Edmonton, AB, Canada ; Neuroscience and Mental Health Institute, University of Alberta Edmonton, AB, Canada
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Boërio D, Bostock H, Spescha R, Z'Graggen WJ. Potassium and the excitability properties of normal human motor axons in vivo. PLoS One 2014; 9:e98262. [PMID: 24893161 PMCID: PMC4043986 DOI: 10.1371/journal.pone.0098262] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2014] [Accepted: 04/30/2014] [Indexed: 11/18/2022] Open
Abstract
Hyperkalemia is an important cause of membrane depolarization in renal failure. A recent theoretical model of axonal excitability explains the effects of potassium on threshold electrotonus, but predicts changes in superexcitability in the opposite direction to those observed. To resolve this contradiction we assessed the relationship between serum potassium and motor axon excitability properties in 38 volunteers with normal potassium levels. Most threshold electrotonus measures were strongly correlated with potassium, and superexcitability decreased at higher potassium levels (P = 0.016), contrary to the existing model. Improved modelling of potassium effects was achieved by making the potassium currents obey the constant-field theory, and by making the potassium permeabilities proportional to external potassium, as has been observed in vitro. This new model also accounted well for the changes in superexcitability and other excitability measures previously reported in renal failure. These results demonstrate the importance of taking potassium levels into account when assessing axonal membrane dysfunction by excitability testing, and provide evidence that potassium currents are activated by external potassium in vivo.
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Affiliation(s)
- Delphine Boërio
- Department of Neurology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
| | - Hugh Bostock
- Department of Neurology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland; Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, United Kingdom
| | - Romana Spescha
- Department of Neurology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
| | - Werner J Z'Graggen
- Department of Neurology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland; Department of Neurosurgery, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
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Liang C, Howells J, Kennerson M, Nicholson GA, Burke D, Ng K. Axonal excitability in X-linked dominant Charcot Marie Tooth disease. Clin Neurophysiol 2014; 125:1261-9. [PMID: 24290847 DOI: 10.1016/j.clinph.2013.11.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2013] [Revised: 10/22/2013] [Accepted: 11/01/2013] [Indexed: 10/26/2022]
Abstract
OBJECTIVE We investigated peripheral nerve function in X-linked Charcot-Marie-Tooth disease type 1 (CMTX1), and considered the functional consequences of mutant connexin-32. METHODS Twelve subjects (9 female, 3 male) were assessed clinically, by nerve conduction and excitability studies. A model of myelinated axon was used to clarify the contributing changes. RESULTS All subjects had abnormal nerve conduction. Excitability studies on median nerve axons showed greater threshold changes to hyperpolarising currents, with "fanning out" in threshold electrotonus, and modest changes in the recovery cycle. Modelling suggested shortening of internodal length, increase in nodal fast potassium currents, shift of the voltage activation hyperpolarisation-activated cyclic-nucleotide-gated channels, and axonal hyperpolarisation. Plotting threshold versus extent of hyperpolarising threshold change in threshold electrotonus distinguished the CMTX1 patients from other chronic demyelinating neuropathies reported in the literature except hereditary neuropathy with pressure palsies (HNPP). CONCLUSIONS Some measures of axonal excitability are similar in CMTX1 and HNPP (though not the recovery cycle), but they differ from those in other chronic demyelinating neuropathies. The findings in CMTX1 are consistent with known pathology, but are not correlated to neuropathy severity. SIGNIFICANCE The findings in CMTX1 could be largely the result of morphological alterations, rather than plasticity in channel expression or distribution.
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Affiliation(s)
- Christina Liang
- Department of Neurology and Clinical Neurophysiology, Royal North Shore Hospital, NSW, Australia; The University of Sydney, NSW, Australia
| | - James Howells
- Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, NSW, Australia; The University of Sydney, NSW, Australia
| | - Marina Kennerson
- ANZAC Research Institute, Concord Repatriation Hospital, NSW, Australia; The University of Sydney, NSW, Australia
| | - Garth A Nicholson
- ANZAC Research Institute, Concord Repatriation Hospital, NSW, Australia; The University of Sydney, NSW, Australia
| | - David Burke
- Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, NSW, Australia; The University of Sydney, NSW, Australia
| | - Karl Ng
- Department of Neurology and Clinical Neurophysiology, Royal North Shore Hospital, NSW, Australia; Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, NSW, Australia; The University of Sydney, NSW, Australia.
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Moldovan M, Lange KHW, Aachmann-Andersen NJ, Kjær TW, Olsen NV, Krarup C. Transient impairment of the axolemma following regional anaesthesia by lidocaine in humans. J Physiol 2014; 592:2735-50. [PMID: 24710060 DOI: 10.1113/jphysiol.2014.270827] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The local anaesthetic lidocaine is known to block voltage-gated Na(+) channels (VGSCs), although at high concentration it was also reported to block other ion channel currents as well as to alter lipid membranes. The aim of this study was to investigate whether the clinical regional anaesthetic action of lidocaine could be accounted for solely by the block of VGSCs or whether other mechanisms are also relevant. We tested the recovery of motor axon conduction and multiple measures of excitability by 'threshold-tracking' after ultrasound-guided distal median nerve regional anaesthesia in 13 healthy volunteers. Lidocaine caused rapid complete motor axon conduction block localized at the wrist. Within 3 h, the force of the abductor pollicis brevis muscle and median motor nerve conduction studies returned to normal. In contrast, the excitability of the motor axons at the wrist remained markedly impaired as indicated by a 7-fold shift of the stimulus-response curves to higher currents with partial recovery by 6 h and full recovery by 24 h. The strength-duration properties were abnormal with markedly increased rheobase and reduced strength-duration time constant. The changes in threshold during electrotonus, especially during depolarization, were markedly reduced. The recovery cycle showed increased refractoriness and reduced superexcitability. The excitability changes were only partly similar to those previously observed after poisoning with the VGSC blocker tetrodotoxin. Assuming an unaltered ion-channel gating, modelling indicated that, apart from up to a 4-fold reduction in the number of functioning VGSCs, lidocaine also caused a decrease of passive membrane resistance and an increase of capacitance. Our data suggest that the lidocaine effects, even at clinical 'sub-blocking' concentrations, could reflect, at least in part, a reversible structural impairment of the axolemma.
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Affiliation(s)
- Mihai Moldovan
- Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Kai Henrik Wiborg Lange
- Department of Anesthesia, Nordsjællands Hospital and University of Copenhagen, Copenhagen, Denmark
| | | | - Troels Wesenberg Kjær
- Department of Clinical Neurophysiology, The Neuroscience Center, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
| | - Niels Vidiendal Olsen
- Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark Department of Neuroanesthesia, The Neuroscience Center, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
| | - Christian Krarup
- Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark Department of Clinical Neurophysiology, The Neuroscience Center, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
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Moldovan M, Alvarez S, Romer Rosberg M, Krarup C. Axonal voltage-gated ion channels as pharmacological targets for pain. Eur J Pharmacol 2013; 708:105-12. [PMID: 23500193 DOI: 10.1016/j.ejphar.2013.03.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Accepted: 03/04/2013] [Indexed: 12/19/2022]
Abstract
Upon peripheral nerve injury (caused by trauma or disease process) axons of the dorsal root ganglion (DRG) somatosensory neurons have the ability to sprout and regrow/remyelinate to reinnervate distant target tissue or form a tangled scar mass called a neuroma. This regenerative response can become maladaptive leading to a persistent and debilitating pain state referred to as chronic pain corresponding to the clinical description of neuropathic/chronic inflammatory pain. There is little agreement to what causes peripheral chronic pain other than hyperactivity of the nociceptive DRG neurons which ultimately depends on the function of voltage-gated ion channels. This review focuses on the pharmacological modulators of voltage-gated ion channels known to be present on axonal membrane which represents by far the largest surface of DRG neurons. Blockers of voltage-gated Na(+) channels, openers of voltage-gated K(+) channels and blockers of hyperpolarization-activated cyclic nucleotide-gated channels that were found to reduce neuronal activity were also found to be effective in neuropathic and inflammatory pain states. The isoforms of these channels present on nociceptive axons have limited specificity. The rationale for considering axonal voltage-gated ion channels as targets for pain treatment comes from the accumulating evidence that chronic pain states are associated with a dysregulation of these channels that could alter their specificity and make them more susceptible to pharmacological modulation. This drives the need for further development of subtype-specific voltage-gated ion channels modulators, as well as clinically available neurophysiological techniques for monitoring axonal ion channel function in peripheral nerves.
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Affiliation(s)
- Mihai Moldovan
- Institute of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark.
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Crone C, Krarup C. Neurophysiological approach to disorders of peripheral nerve. HANDBOOK OF CLINICAL NEUROLOGY 2013; 115:81-114. [PMID: 23931776 DOI: 10.1016/b978-0-444-52902-2.00006-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Disorders of the peripheral nerve system (PNS) are heterogeneous and may involve motor fibers, sensory fibers, small myelinated and unmyelinated fibers and autonomic nerve fibers, with variable anatomical distribution (single nerves, several different nerves, symmetrical affection of all nerves, plexus, or root lesions). Furthermore pathological processes may result in either demyelination, axonal degeneration or both. In order to reach an exact diagnosis of any neuropathy electrophysiological studies are crucial to obtain information about these variables. Conventional electrophysiological methods including nerve conduction studies and electromyography used in the study of patients suspected of having a neuropathy and the significance of the findings are discussed in detail and more novel and experimental methods are mentioned. Diagnostic considerations are based on a flow chart classifying neuropathies into eight categories based on mode of onset, distribution, and electrophysiological findings, and the electrophysiological characteristics in each type of neuropathy are discussed.
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Affiliation(s)
- Clarissa Crone
- Department of Clinical Neurophysiology, Rigshospitalet and University of Copenhagen, Copenhagen, Denmark
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KUNHIMANGALAM REEDA, OVALLATH SUJITH, JOSEPH PAULK. ARTIFICIAL NEURAL NETWORKS IN THE IDENTIFICATION OF PERIPHERAL NERVE DISORDERS. J MECH MED BIOL 2012. [DOI: 10.1142/s0219519412400180] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The recent years have witnessed an increase in the use of newer analytical tools in the field of medicine to assist in diagnostic procedure. Among the new tools, artificial neural networks (ANNs) have received particular attention because of their ability to analyze complex nonlinear data sets. This study suggests that ANNs can be used for the diagnosis of peripheral nerve disorders particularly the carpal tunnel syndrome (CTS) and neuropathy. This paper aims at building a classifier using a feed forward neural network that can distinguish between CTS, neuropathy, and normal controls using a reduced set of measurements or features from nerve conduction study (NCS) data. Three different ANN training algorithms, viz. Levenberg–Marquardt (LM), Conjugate gradient (CGB), and resilient back-propagation (RP) are used to see which algorithm produces better results and has faster training for the application under consideration. The data used were obtained from the Neurology Department, Kannur Medical College, Kerala, India. The obtained resultant confusion matrix indicated only a few misclassifications in all the three cases. The analysis showed that the CGB and RB algorithms provide faster convergence on pattern recognition problems, but the best performance in terms of accuracy is given by the LM algorithm. The accuracy obtained for the LM, CGB, and RB were 98.3%, 97.8%, and 97.2%, respectively. The respective sensitivities were 96.1%, 94.1%, and 94.1%, while the specificities were found to be equal to 99.4%, 98.8%, and 97.5%, respectively. The study aims at showing that ANNs may prove useful in combination with other systems in providing diagnostic and predictive medical opinions. However, it must always be kept in mind that ANNs represent only one form of computer-aided diagnosis, and the clinician's responsibility and overall control of patient care should never be underestimated.
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Affiliation(s)
- REEDA KUNHIMANGALAM
- National Institute of Technology, NIT Calicut (PO), Kozhikode, Kerala 673601, India
| | - SUJITH OVALLATH
- Department of Neurology, Kannur Medical College, Anjarakandy (PO), Kerala, India
| | - PAUL K. JOSEPH
- National Institute of Technology, NIT Calicut (PO), Kozhikode, Kerala 673601, India
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Krarup C, Moldovan M. Reappraising I(h:) do myelinated motor and sensory axons of human peripheral nerves operate at different resting membrane potentials? J Physiol 2012; 590:1515-6. [PMID: 22467919 DOI: 10.1113/jphysiol.2012.230821] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Christian Krarup
- Institute of Neuroscience and Pharmacology, University of Copenhagen, 2100 Copenhagen, Denmark.
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Emery EC, Young GT, McNaughton PA. HCN2 ion channels: an emerging role as the pacemakers of pain. Trends Pharmacol Sci 2012; 33:456-63. [PMID: 22613784 DOI: 10.1016/j.tips.2012.04.004] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 04/07/2012] [Accepted: 04/13/2012] [Indexed: 02/08/2023]
Abstract
Acute nociceptive pain is caused by the direct action of a noxious stimulus on pain-sensitive nerve endings, whereas inflammatory pain (both acute and chronic) arises from the actions of a wide range of inflammatory mediators released following tissue injury. Neuropathic pain, which is triggered by nerve damage, is often considered to be very different in its origins, and is particularly difficult to treat effectively. Here we review recent evidence showing that members of the hyperpolarization-activated cyclic nucleotide-modulated (HCN) ion channel family - better known for their role in the pacemaker potential of the heart - play important roles in both inflammatory and neuropathic pain. Deletion of the HCN2 isoform from nociceptive neurons abolishes heat-evoked inflammatory pain and all aspects of neuropathic pain, but acute pain sensation is unaffected. This work shows that inflammatory and neuropathic pain have much in common, and suggests that selective blockers of HCN2 may have value as analgesics in the treatment of pain.
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Affiliation(s)
- Edward C Emery
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
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Boërio D, Greensmith L, Bostock H. A model of mouse motor nerve excitability and the effects of polarizing currents. J Peripher Nerv Syst 2011; 16:322-33. [DOI: 10.1111/j.1529-8027.2011.00364.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Bucher D, Goaillard JM. Beyond faithful conduction: short-term dynamics, neuromodulation, and long-term regulation of spike propagation in the axon. Prog Neurobiol 2011; 94:307-46. [PMID: 21708220 PMCID: PMC3156869 DOI: 10.1016/j.pneurobio.2011.06.001] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Revised: 05/27/2011] [Accepted: 06/07/2011] [Indexed: 12/13/2022]
Abstract
Most spiking neurons are divided into functional compartments: a dendritic input region, a soma, a site of action potential initiation, an axon trunk and its collaterals for propagation of action potentials, and distal arborizations and terminals carrying the output synapses. The axon trunk and lower order branches are probably the most neglected and are often assumed to do nothing more than faithfully conducting action potentials. Nevertheless, there are numerous reports of complex membrane properties in non-synaptic axonal regions, owing to the presence of a multitude of different ion channels. Many different types of sodium and potassium channels have been described in axons, as well as calcium transients and hyperpolarization-activated inward currents. The complex time- and voltage-dependence resulting from the properties of ion channels can lead to activity-dependent changes in spike shape and resting potential, affecting the temporal fidelity of spike conduction. Neural coding can be altered by activity-dependent changes in conduction velocity, spike failures, and ectopic spike initiation. This is true under normal physiological conditions, and relevant for a number of neuropathies that lead to abnormal excitability. In addition, a growing number of studies show that the axon trunk can express receptors to glutamate, GABA, acetylcholine or biogenic amines, changing the relative contribution of some channels to axonal excitability and therefore rendering the contribution of this compartment to neural coding conditional on the presence of neuromodulators. Long-term regulatory processes, both during development and in the context of activity-dependent plasticity may also affect axonal properties to an underappreciated extent.
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Affiliation(s)
- Dirk Bucher
- The Whitney Laboratory and Department of Neuroscience, University of Florida, St. Augustine, FL 32080, USA.
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Abstract
Axons are generally considered as reliable transmission cables in which stable propagation occurs once an action potential is generated. Axon dysfunction occupies a central position in many inherited and acquired neurological disorders that affect both peripheral and central neurons. Recent findings suggest that the functional and computational repertoire of the axon is much richer than traditionally thought. Beyond classical axonal propagation, intrinsic voltage-gated ionic currents together with the geometrical properties of the axon determine several complex operations that not only control signal processing in brain circuits but also neuronal timing and synaptic efficacy. Recent evidence for the implication of these forms of axonal computation in the short-term dynamics of neuronal communication is discussed. Finally, we review how neuronal activity regulates both axon morphology and axonal function on a long-term time scale during development and adulthood.
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Affiliation(s)
- Dominique Debanne
- Institut National de la Santé et de la Recherche Médicale U.641 and Université de la Méditerranée, Faculté de Médecine Secteur Nord, Marseille, France
| | - Emilie Campanac
- Institut National de la Santé et de la Recherche Médicale U.641 and Université de la Méditerranée, Faculté de Médecine Secteur Nord, Marseille, France
| | - Andrzej Bialowas
- Institut National de la Santé et de la Recherche Médicale U.641 and Université de la Méditerranée, Faculté de Médecine Secteur Nord, Marseille, France
| | - Edmond Carlier
- Institut National de la Santé et de la Recherche Médicale U.641 and Université de la Méditerranée, Faculté de Médecine Secteur Nord, Marseille, France
| | - Gisèle Alcaraz
- Institut National de la Santé et de la Recherche Médicale U.641 and Université de la Méditerranée, Faculté de Médecine Secteur Nord, Marseille, France
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Coşkun Ö, Naziroğlu M, Çömlekçi S, Özkorucuklu S. Effects of 50 Hertz-1 mT magnetic field on action potential in isolated rat sciatic nerve. Toxicol Ind Health 2010; 27:127-32. [DOI: 10.1177/0748233710381893] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The aim of this study was to investigate possible effects of 50 Hz-1 mT magnetic field (MF) on action potential in isolated rat sciatic nerve. We used 16 Wistar rats in the study. They were divided into control (n = 10) and MF (n = 6) groups. The sciatic nerve of left legs in the MF group was exposed to 50 Hz-1 mT MF for 30 min by using a Helmholtz applicator and then action potentials in control and experimental groups were recorded extracellularly. Maximum amplitude and hyperpolarization time and action potential were significantly (p ≤ 0.025) lower in the MF group than in control. However, conduction time, minimum amplitude, depolarization and repolarization times of the action potential was not different between control and MF groups evaluated. In conclusion, 50-1 mT MF caused to decrease amplitude value and hyperpolarization time of action potential in the rat nerve.
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Affiliation(s)
- Özlem Coşkun
- Department of Biomedical Device Technology, Süleyman Demirel University, Isparta, Turkey
| | - Mustafa Naziroğlu
- Department of Biophysics, Medical Faculty, Süleyman Demirel University, Isparta, Turkey,
| | - Selçuk Çömlekçi
- Department of Electronics and Communication Engineering, Faculty of Engineering, Süleyman Demirel University, Isparta, Turkey
| | - Suat Özkorucuklu
- Department of Physics, Science Faculty, Süleyman Demirel University, Isparta, Turkey
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