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Pavey NA, Menon P, Peterchev AV, Kiernan MC, Vucic S. Abnormalities of cortical stimulation strength-duration time constant in amyotrophic lateral sclerosis. Clin Neurophysiol 2024; 164:161-167. [PMID: 38901111 PMCID: PMC11345808 DOI: 10.1016/j.clinph.2024.05.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2024] [Revised: 04/23/2024] [Accepted: 05/26/2024] [Indexed: 06/22/2024]
Abstract
OBJECTIVES Strength-duration time constant (SDTC) may now be determined for cortical motor neurones, with activity mediated by transient Na+ conductances. The present study determined whether cortical SDTC is abnormal and linked to the pathogenesis of amyotrophic lateral sclerosis. METHODS Cortical SDTC and rheobase were estimated from 17 ALS patients using a controllable pulse parameter transcranial magnetic stimulation (cTMS) device. Resting motor thresholds (RMTs) were determined at pulse widths (PW) of 30, 45, 60, 90 and 120 µs and M-ratio of 0.1, using a figure-of-eight coil applied to the primary motor cortex. RESULTS SDTC was significantly reduced in ALS patients (150.58 ± 9.98 µs; controls 205.94 ± 13.7 µs, P < 0.01). The reduced SDTC correlated with a rate of disease progression (Rho = -0.440, P < 0.05), ALS functional rating score (ALSFRS-R) score (Rho = 0.446, P < 0.05), and disease duration (R = 0.428, P < 0.05). The degree of change in SDTC was greater in patients with cognitive abnormalities as manifested by an abnormal total Edinburgh Cognitive ALS Screen score (140.5 ± 28.7 µs, P < 0.001) and ALS-specific subscore (141.7 ± 33.2 µs, P = 0.003). CONCLUSIONS Cortical SDTC reduction was associated with a more aggressive ALS phenotype, or with more prominent cognitive impairment. SIGNIFICANCE An increase in transient Na+ conductances may account for the reduction in SDTC, linked to the pathogenesis of ALS.
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Affiliation(s)
- Nathan A Pavey
- Brain and Nerve Research Centre, Concord Clinical School, University of Sydney, Concord Hospital, Sydney, Australia
| | - Parvathi Menon
- Brain and Nerve Research Centre, Concord Clinical School, University of Sydney, Concord Hospital, Sydney, Australia
| | - Angel V Peterchev
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA; Department of Biomedical Engineering, Duke University, Durham, NC, USA; Department of Psychiatry and Behavioural Sciences, Duke University, Durham, NC, USA; Department of Electrical and Computer Engineering, Duke University, Durham, NC, USA; Department of Neurosurgery, Duke University, Durham, NC, USA
| | | | - Steve Vucic
- Brain and Nerve Research Centre, Concord Clinical School, University of Sydney, Concord Hospital, Sydney, Australia.
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Shin-Yi Lin C, Howells J, Rutkove S, Nandedkar S, Neuwirth C, Noto YI, Shahrizaila N, Whittaker RG, Bostock H, Burke D, Tankisi H. Neurophysiological and imaging biomarkers of lower motor neuron dysfunction in motor neuron diseases/amyotrophic lateral sclerosis: IFCN handbook chapter. Clin Neurophysiol 2024; 162:91-120. [PMID: 38603949 DOI: 10.1016/j.clinph.2024.03.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 02/07/2024] [Accepted: 03/12/2024] [Indexed: 04/13/2024]
Abstract
This chapter discusses comprehensive neurophysiological biomarkers utilised in motor neuron disease (MND) and, in particular, its commonest form, amyotrophic lateral sclerosis (ALS). These encompass the conventional techniques including nerve conduction studies (NCS), needle and high-density surface electromyography (EMG) and H-reflex studies as well as novel techniques. In the last two decades, new methods of assessing the loss of motor units in a muscle have been developed, that are more convenient than earlier methods of motor unit number estimation (MUNE),and may use either electrical stimulation (e.g. MScanFit MUNE) or voluntary activation (MUNIX). Electrical impedance myography (EIM) is another novel approach for the evaluation that relies upon the application and measurement of high-frequency, low-intensity electrical current. Nerve excitability techniques (NET) also provide insights into the function of an axon and reflect the changes in resting membrane potential, ion channel dysfunction and the structural integrity of the axon and myelin sheath. Furthermore, imaging ultrasound techniques as well as magnetic resonance imaging are capable of detecting the constituents of morphological changes in the nerve and muscle. The chapter provides a critical description of the ability of each technique to provide neurophysiological insight into the complex pathophysiology of MND/ALS. However, it is important to recognise the strengths and limitations of each approach in order to clarify utility. These neurophysiological biomarkers have demonstrated reliability, specificity and provide additional information to validate and assess lower motor neuron dysfunction. Their use has expanded the knowledge about MND/ALS and enhanced our understanding of the relationship between motor units, axons, reflexes and other neural circuits in relation to clinical features of patients with MND/ALS at different stages of the disease. Taken together, the ultimate goal is to aid early diagnosis, distinguish potential disease mimics, monitor and stage disease progression, quantify response to treatment and develop potential therapeutic interventions.
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Affiliation(s)
- Cindy Shin-Yi Lin
- Faculty of Medicine and Health, Central Clinical School, Brain and Mind Centre, University of Sydney, Sydney 2006, Australia.
| | - James Howells
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Seward Rutkove
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Sanjeev Nandedkar
- Natus Medical Inc, Middleton, Wisconsin, USA and Medical College of Wisconsin, Milwaukee, WI, USA
| | - Christoph Neuwirth
- Neuromuscular Diseases Unit/ALS Clinic, Kantonsspital, St. Gallen, Switzerland
| | - Yu-Ichi Noto
- Department of Neurology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Nortina Shahrizaila
- Division of Neurology, Department of Medicine, University of Malaya, Kuala Lumpur 50603, Malaysia
| | - Roger G Whittaker
- Newcastle University Translational and Clinical Research Institute (NUTCRI), Newcastle University., Newcastle Upon Tyne, United Kingdom
| | - Hugh Bostock
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, WC1N 3BG, London, United Kingdom
| | - David Burke
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital and Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.
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Créange A, Hutin E, Sedel F, Le Vigouroux L, Lefaucheur JP. High-dose pharmaceutical-grade biotin in patients with demyelinating neuropathies: a phase 2b open label, uncontrolled, pilot study. BMC Neurol 2023; 23:389. [PMID: 37899433 PMCID: PMC10614347 DOI: 10.1186/s12883-023-03440-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Accepted: 10/18/2023] [Indexed: 10/31/2023] Open
Abstract
BACKGROUND We proposed to investigate high-dose pharmaceutical-grade biotin in a population of demyelinating neuropathies of different aetiologies, as a proof-of-concept. METHODS Phase IIb open label, uncontrolled, single center, pilot study in 15 patients (three groups of five patients) with chronic demyelinating peripheral neuropathy, i.e. chronic inflammatory demyelinating polyradiculoneuropathy, anti-myelin-associated glycoprotein neuropathy and Charcot-Marie-Tooth 1a or 1b. The investigational product was high-dose pharmaceutical-grade biotin (100 mg taken orally three times a day over a maximum of 52 weeks. The primary endpoint was a 10% relative improvement in 2 of the following 4 electrophysiological variables: motor nerve conduction velocity, distal motor latency, F wave latency, duration of the compound muscle action potential. The secondary endpoints included Overall Neuropathy Limitations Scale (ONLS) score, Medical Research Council (MRC) sum score, Inflammatory Neuropathy Cause and Treatment (INCAT) sensory sum score, 10-m walk test, 6-min walk test, posturography parameters, and nerve excitability variables. RESULTS The primary endpoint was reached in one patient. In the full population analysis, some secondary endpoints parameters improved: MRC score, INCAT sensory sum score, 6-min walk distance, strength-duration time constant, and rheobase. There was a positive correlation between the improvement in the 6-min walk distance and the strength-duration time constant. Regarding the safety results, 42 adverse events occurred, of which three were of severe intensity but none was considered as related to the investigational product. CONCLUSIONS Even if the primary endpoint was not met, administration of high-dose pharmaceutical-grade biotin led to an improvement in various sensory and motor parameters, gait abilities, and nerve excitability parameters. The tolerance of the treatment was satisfactory. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT02967679; date 2016/12/05.
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Affiliation(s)
- Alain Créange
- AP-HP, Hôpital Henri Mondor, Service de Neurologie, 94010, Créteil, France.
- AP-HP, Hôpital Henri Mondor, CRC SEP Grand Paris Est, 94010, Créteil, France.
- Université Paris Est Créteil, EA4391, ENT, F-94010, Créteil, France.
| | - Emilie Hutin
- Laboratoire Analyse Et Restauration du Mouvement, Service de Rééducation Neurolocomotrice, AP-HP, Hôpital Henri Mondor, 94010, Créteil, France
- Université Paris Est Créteil, EA 7377, BIOTN, F-94010, Créteil, France
| | | | | | - Jean-Pascal Lefaucheur
- AP-HP, Hôpital Henri Mondor, CRC SEP Grand Paris Est, 94010, Créteil, France
- Université Paris Est Créteil, EA4391, ENT, F-94010, Créteil, France
- AP-HP, Hôpital Henri Mondor, Unité de Neurophysiologie Clinique, 94010, Créteil, France
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Chien CY, Wang JD, Lin CC. Nerve excitability test and lead toxicity: a case-control study. J Occup Med Toxicol 2023; 18:19. [PMID: 37653420 PMCID: PMC10472560 DOI: 10.1186/s12995-023-00385-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 08/11/2023] [Indexed: 09/02/2023] Open
Abstract
BACKGROUND Although conventional electrophysiological parameters have been proposed as clinical indicators for monitoring lead neuropathies, their correlations with blood lead level are weak. In this study, we investigated the applicability of nerve excitability tests (NETs) to evaluate lead intoxication. METHODS Fourteen workers who were exposed to lead with an elevated blood level ranging from 17.8 to 64.9 µg/dL and 20 healthy controls with similar ages and body heights were enrolled. Both workers and controls underwent nerve conduction studies (NCSs), motor evoked potentials (MEPs) with transcranial magnetic stimulation (TMS), and NETs. RESULTS NCSs showed prolonged distal latencies and decreased motor nerve conduction velocity of median nerves in the workers but without significant correlation to blood lead level (BLL). Significantly prolonged MEP latency was observed in the workers (+ 6 ms). NETs demonstrated hyperpolarized resting membrane potentials in stimulus-response curves and changes in the property of potassium channels under a hyperpolarized current in threshold electrotonus, implying that lead hyperpolarized nerves by interfering with potassium channels. NETs also showed a better correlation with BLL than conventional electrophysiological parameters. CONCLUSIONS Axonal hyperpolarization and central conduction delay are more apparently reflecting elevated BLL than NCS. NET may have the potential for early detection of lead neuropathy.
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Affiliation(s)
- Chung-Yao Chien
- Department of Neurology, College of Medicine, National Cheng Kung University Hospital, National Cheng Kung University, 138 Sheng Li Road, Tainan, 704, Taiwan
| | - Jung-Der Wang
- Department of Public Health, College of Medicine, National Cheng Kung University, Tainan, Taiwan
- Department of Occupational and Environmental Medicine, National Cheng Kung University Hospital, Tainan, Taiwan
| | - Chou-Ching Lin
- Department of Neurology, College of Medicine, National Cheng Kung University Hospital, National Cheng Kung University, 138 Sheng Li Road, Tainan, 704, Taiwan.
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan.
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Menon P, Pavey N, Aberra AS, van den Bos MAJ, Wang R, Kiernan MC, Peterchev AV, Vucic S. Dependence of cortical neuronal strength-duration properties on TMS pulse shape. Clin Neurophysiol 2023; 150:106-118. [PMID: 37060842 PMCID: PMC10280814 DOI: 10.1016/j.clinph.2023.03.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Revised: 02/13/2023] [Accepted: 03/08/2023] [Indexed: 04/17/2023]
Abstract
OBJECTIVE The aim of present study was to explore the effects of different combinations of transcranial magnetic stimulation (TMS) pulse width and pulse shape on cortical strength-duration time constant (SDTC) and rheobase measurements. METHODS Resting motor thresholds (RMT) at pulse widths (PW) of 30, 45, 60, 90 and 120 µs and M-ratios of 0.2, 0.1 and 0.025 were determined using figure-of-eight coil with initial posterior-to-anterior induced current. The M-ratio indicates the relative phases of the induced current with lower values signifying a more unidirectional stimulus. Strength-duration time constant (SDTC) and rheobase were estimated for each M-ratio and various PW combinations. Simulations of biophysically realistic cortical neuron models assessed underlying neuronal populations and physiological mechanisms mediating pulse shape effects on strength-duration properties. RESULTS The M-ratio exerted significant effect on SDTC (F(2,44) = 4.386, P = 0.021), which was longer for M-ratio of 0.2 (243.4 ± 61.2 µs) compared to 0.025 (186.7 ± 52.5 µs, P = 0.034). Rheobase was significantly smaller when assessed with M-ratio 0.2 compared to 0.025 (P = 0.026). SDTC and rheobase values were most consistent with pulse width sets of 30/45/60/90/120 µs, 30/60/90/120 µs, and 30/60/120 µs. Simulation studies indicated that isolated pyramidal neurons in layers 2/3, 5, and large basket-cells in layer 4 exhibited SDTCs comparable to experimental results. Further, simulation studies indicated that reducing transient Na+ channel conductance increased SDTC with larger increases for higher M-ratios. CONCLUSIONS Cortical strength-duration curve properties vary with pulse shape, and the modulating effect of the hyperpolarising pulse phase on cortical axonal transient Na+ conductances could account for these changes, although a shift in the recruited neuronal populations may contribute as well. SIGNIFICANCE The dependence of the cortical strength-duration curve properties on the TMS pulse shape and pulse width selection underscores the need for consistent measurement methods across studies and the potential to extract information about pathophysiological processes.
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Affiliation(s)
- Parvathi Menon
- Brain and Nerve Research Centre, Concord Clinical School, University of Sydney, Concord Hospital, Sydney, Australia
| | - Nathan Pavey
- Brain and Nerve Research Centre, Concord Clinical School, University of Sydney, Concord Hospital, Sydney, Australia
| | - Aman S Aberra
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA
| | - Mehdi A J van den Bos
- Brain and Nerve Research Centre, Concord Clinical School, University of Sydney, Concord Hospital, Sydney, Australia
| | - Ruochen Wang
- Department of Biomedical Engineering, Duke University, Durham, NC, USA
| | | | - Angel V Peterchev
- Department of Biomedical Engineering, Duke University, Durham, NC, USA; Department of Psychiatry and Behavioural Sciences, Duke University, Durham, NC, USA; Department of Electrical and Computer Engineering, Duke University, Durham, NC, USA; Department of Neurosurgery, Duke University, Durham, NC, USA.
| | - Steve Vucic
- Brain and Nerve Research Centre, Concord Clinical School, University of Sydney, Concord Hospital, Sydney, Australia.
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6
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Klein C, Liu H, Zhao C, Huang W. Altered flexor carpi radialis motor axon excitability properties after cerebrovascular stroke. Front Neurol 2023; 14:1172960. [PMID: 37284180 PMCID: PMC10240235 DOI: 10.3389/fneur.2023.1172960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Accepted: 04/12/2023] [Indexed: 06/08/2023] Open
Abstract
Background Spinal motoneurons may become hyperexcitable after a stroke. Knowledge about motoneuron hyperexcitability remains clinically important as it may contribute to a number of phenomena including spasticity, flexion synergies, and abnormal limb postures. Hyperexcitability seems to occur more often in muscles that flex the wrist and fingers (forearm flexors) compared to other upper limb muscles. The cause of hyperexcitability remains uncertain but may involve plastic changes in motoneurons and their axons. Aim To characterize intrinsic membrane properties of flexor carpi radialis (FCR) motor axons after stroke using nerve excitability testing. Methods Nerve excitability testing using threshold tracking techniques was applied to characterize FCR motor axon properties in persons who suffered a first-time unilateral cortical/subcortical stroke 23 to 308 days earlier. The median nerve was stimulated at the elbow bilaterally in 16 male stroke subjects (51.4 ± 2.9 y) with compound muscle action potentials recorded from the FCR. Nineteen age-matched males (52.7 ± 2.4 y) were also tested to serve as controls. Results Axon parameters after stroke were consistent with bilateral hyperpolarization of the resting potential. Nonparetic and paretic side axons were modeled by a 2.6-fold increase in pump currents (IPumpNI) together with an increase (38%-33%) in internodal leak conductance (GLkI) and a decrease (23%-29%) in internodal H conductance (Ih) relative to control axons. A decrease (14%) in Na+ channel inactivation rate (Aah) was also needed to fit the paretic axon recovery cycle. "Fanning out" of threshold electrotonus and the resting I/V slope (stroke limbs combined) correlated with blood potassium [K+] (R = -0.61 to 0.62, p< 0.01) and disability (R = -0.58 to 0.55, p < 0.05), but not with spasticity, grip strength, or maximal FCR activity. Conclusion In contrast to our expectations, FCR axons were not hyperexcitable after stroke. Rather, FCR axons were found to be hyperpolarized bilaterally post stroke, and this was associated with disability and [K+]. Reduced FCR axon excitability may represent a kind of bilateral trans-synaptic homeostatic mechanism that acts to minimize motoneuron hyperexcitability.
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Jankowska E, Kaczmarek D, Hammar I. Long-term modulation of the axonal refractory period. Eur J Neurosci 2022; 56:4983-4999. [PMID: 35999192 PMCID: PMC9826316 DOI: 10.1111/ejn.15801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 07/25/2022] [Accepted: 08/15/2022] [Indexed: 01/11/2023]
Abstract
The main question addressed in this study was whether the refractoriness of nerve fibres can be modulated by their depolarisation and, if so, whether depolarisation of nerve fibres evokes a long-term decrease in the duration of the refractory period as well as the previously demonstrated increase in their excitability. This was investigated on nerve fibres within the dorsal columns, dorsal roots and peripheral nerves in deeply anaesthetised rats in vivo. The results revealed major differences depending on the sites of fibre stimulation and polarisation. Firstly, the relative refractory period was found to be shorter in epidurally stimulated dorsal column fibres than in fibres stimulated at other sites. Secondly, the minimal effective interstimulus intervals reflecting the absolute refractory period were likewise shorter for nerve fibres within the dorsal columns even though action potentials evoked by the second of a pair of stimuli were similarly delayed with respect to the preceding action potentials at all the stimulation sites. Thirdly, the minimal interstimulus intervals were reduced by epidurally applied cathodal direct current polarisation but not at other stimulation sites. Consequently, higher proportions of dorsal column fibres could be excited at higher frequencies, especially following their depolarisation, at interstimulus intervals as short as 0.5-0.7 ms. The results demonstrate that epidural depolarisation results in long-lasting effects not only on the excitability but also on the refractoriness of dorsal column fibres. They also provide further evidence for specific features of afferent fibres traversing the dorsal columns previously linked to properties of their branching regions.
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Affiliation(s)
- Elzbieta Jankowska
- Department of Neuroscience and Physiology, Sahlgrenska AcademyUniversity of GothenburgGothenburgSweden
| | - Dominik Kaczmarek
- Department of Physiology and BiochemistryPoznan University of Physical EducationPoznanPoland
| | - Ingela Hammar
- Department of Neuroscience and Physiology, Sahlgrenska AcademyUniversity of GothenburgGothenburgSweden
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Kim T, Choi H, Choi H, Kim JS, Kim DH, Jeong U. Skin-inspired electrochemical tactility and luminescence. Electrochim Acta 2022. [DOI: 10.1016/j.electacta.2022.140259] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Jung GL, McDaniel KL, LoPachin RM, Geohagen BC, Smith A, Huffstickler M, Herr DW. IN VIVO NEUROPHYSIOLOGICAL ASSESSMENT OF IN SILICO PREDICTIONS OF NEUROTOXICITY: CITRONELLAL, 3,4-DICHLORO-1-BUTENE, AND BENZYL BROMOACETATE. Neurotoxicology 2022; 90:48-61. [PMID: 35227730 PMCID: PMC9133174 DOI: 10.1016/j.neuro.2022.02.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 02/02/2022] [Accepted: 02/21/2022] [Indexed: 11/29/2022]
Abstract
Neurotoxicants may be widespread in the environment and can produce serious health impacts in the human population. Screening programs that use in vitro methods have generated data for thousands of chemicals. However, these methods often do not evaluate repeated or prolonged exposures, which are required for many neurotoxic outcomes. Additionally, the data produced by such screening methods may not include mechanisms which play critical biological roles necessary for in vivo neurotoxicity. The Hard and Soft Acids and Bases (HSAB) in silico model focuses on chemical structure and electrophilic properties which are important to the formation of protein adducts. A group of structurally diverse chemicals have been evaluated with an in silico screening approach incorporating HSAB parameters. However, the predictions from the expanded chemical space have not been evaluated using in vivo methods. Three chemicals predicted to be cumulative toxicants were selected for in vivo neurotoxicological testing. Adult male Long-Evans rats were treated orally with citronellal (CIT), 3,4-dichloro-1-butene (DCB), or benzyl bromoacetate (BBA) for 8 weeks. Behavioral observations were recorded weekly to assess motor function. Peripheral neurophysiological measurements were derived from nerve excitability (NE) tests which involved compound muscle action potentials (CMAPs) in the tail and foot, and mixed nerve action potentials (MNAPs) in the tail. Compound nerve action potentials (CNAPs) and nerve conduction velocity (NCV) in the tail were also quantified. Peripheral inputs into the central nervous system were examined using somatosensory evoked potentials recorded from the cortex (SEPCTX) and cerebellum (SEPCEREB). CIT or BBA did not result in significant alterations to peripheral nerve or somatosensory function. DCB reduced grip-strength and altered peripheral nerve function. The MNAPs required less current to reach 50% amplitude and had a lower calculated rheobase, suggesting increased excitability. Increased CNAP amplitudes and greater NCV were also observed. Novel changes were found in the SEPCTX with an abnormal peak forming in the early portion of the waveforms of treated rats, and decreased latencies and increased amplitudes were observed in SEPCEREB recordings. These data contribute to testing an expanded chemical space from an in silico HSAB model for predicting cumulative neurotoxicity and may assist with prioritizing chemicals to protect human health.
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Affiliation(s)
- Garyn L Jung
- Center for Public Health and Environmental Assessment, US Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
| | - Katherine L McDaniel
- Center for Public Health and Environmental Assessment, US Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
| | - Richard M LoPachin
- Professor Emeritus in the Department of Anesthesiology, Albert Einstein College of Medicine, 111 E. 210th St, Bronx, NY 10467, USA.
| | - Brian C Geohagen
- Department of Anesthesiology, Montefiore Medical Center, Albert Einstein College of Medicine, 111 E. 210th St, Bronx, NY 10467, USA.
| | - Alicia Smith
- Oak Ridge Institute for Science Education, Oak Ridge, Tennessee 37830, USA.
| | | | - David W Herr
- Center for Public Health and Environmental Assessment, US Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
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Herr DW. The Future of Neurotoxicology: A Neuroelectrophysiological Viewpoint. FRONTIERS IN TOXICOLOGY 2021; 3:1. [PMID: 34966904 PMCID: PMC8711081 DOI: 10.3389/ftox.2021.729788] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 11/29/2021] [Indexed: 11/13/2022] Open
Abstract
Neuroelectrophysiology is an old science, dating to the 18th century when electrical activity in nerves was discovered. Such discoveries have led to a variety of neurophysiological techniques, ranging from basic neuroscience to clinical applications. These clinical applications allow assessment of complex neurological functions such as (but not limited to) sensory perception (vision, hearing, somatosensory function), and muscle function. The ability to use similar techniques in both humans and animal models increases the ability to perform mechanistic research to investigate neurological problems. Good animal to human homology of many neurophysiological systems facilitates interpretation of data to provide cause-effect linkages to epidemiological findings. Mechanistic cellular research to screen for toxicity often includes gaps between cellular and whole animal/person neurophysiological changes, preventing understanding of the complete function of the nervous system. Building Adverse Outcome Pathways (AOPs) will allow us to begin to identify brain regions, timelines, neurotransmitters, etc. that may be Key Events (KE) in the Adverse Outcomes (AO). This requires an integrated strategy, from in vitro to in vivo (and hypothesis generation, testing, revision). Scientists need to determine intermediate levels of nervous system organization that are related to an AO and work both upstream and downstream using mechanistic approaches. Possibly more than any other organ, the brain will require networks of pathways/AOPs to allow sufficient predictive accuracy. Advancements in neurobiological techniques should be incorporated into these AOP-base neurotoxicological assessments, including interactions between many regions of the brain simultaneously. Coupled with advancements in optogenetic manipulation, complex functions of the nervous system (such as acquisition, attention, sensory perception, etc.) can be examined in real time. The integration of neurophysiological changes with changes in gene/protein expression can begin to provide the mechanistic underpinnings for biological changes. Establishment of linkages between changes in cellular physiology and those at the level of the AO will allow construction of biological pathways (AOPs) and allow development of higher throughput assays to test for changes to critical physiological circuits. To allow mechanistic/predictive toxicology of the nervous system to be protective of human populations, neuroelectrophysiology has a critical role in our future.
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Affiliation(s)
- David W. Herr
- Neurological and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, CPHEA/ORD, U.S. Environmental Protection Agency, Washington, NC, United States
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Carroll AS, Howells J, Lin CS, Park SB, Simon N, Reilly MM, Vucic S, Kiernan MC. Differences in nerve excitability properties across upper limb sensory and motor axons. Clin Neurophysiol 2021; 136:138-149. [DOI: 10.1016/j.clinph.2021.12.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 11/16/2021] [Accepted: 12/07/2021] [Indexed: 11/24/2022]
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Kariyawasam DST, D'Silva AM, Herbert K, Howells J, Carey K, Kandula T, Farrar MA, Lin CSY. Axonal excitability changes in children with spinal muscular atrophy treated with nusinersen. J Physiol 2021; 600:95-109. [PMID: 34783018 DOI: 10.1113/jp282249] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 11/05/2021] [Indexed: 11/08/2022] Open
Abstract
Spinal muscular atrophy (SMA) is associated with developmental disruption of motor axons in ventral roots of the spinal cord alongside motor axon degeneration. The pathogenesis of peripheral axonal change during development is pertinent to understand treatment response. Nerve excitability techniques, stimulating the median motor nerve at the wrist, were utilised to investigate axonal change during neurodevelopment in 24 children with SMA, compared with 71 age-matched controls. Longitudinal axonal response to nusinersen treatment in 18 children was also investigated. Significant differences in axonal development were noted in the youngest children with SMA, signified by reduced compound muscle action potential (CMAP) (P = 0.030), higher axonal threshold (P = 0.016), rheobase (minimal current amplitude of infinite duration, required to generate an action potential) (P = 0.012) and greater changes in depolarising and hyperpolarising threshold electrotonus. Subexcitability increased in all children with SMA, compared to controls. With treatment, nerve excitability changes were observed prominently in young children, with increases in CMAP, reduction in axonal threshold, fanning-in of threshold electrotonus, increase in resting current-threshold slope and reduction in subexcitability. Whilst motor axons continue to mature in SMA, developmental delays in passive and active membrane properties occur especially in early childhood. Concurrently, motor axons actively undergo degeneration. Nusinersen restores the developmental trajectory of motor axons reducing degeneration, especially in children with early treatment initiation. Our findings move the field forward in understanding the developmental aspect of childhood-onset motor neurone diseases and changes in axonal function associated with disease modification. KEY POINTS: Pathomechanisms in spinal muscular atrophy involve concurrent neurodevelopmental and neurodegenerative processes. The greatest delays in maturation of the passive and active properties of the peripheral motor axon are seen in early childhood. Nusinersen facilitates developmental recovery of the motor axon whilst also reducing neurodegeneration. Axonal dysfunction is reversed with SMN repletion particularly when intervention occurs early in development.
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Affiliation(s)
- Didu S T Kariyawasam
- Department of Neurology, Randwick, Sydney Children's Hospital, Sydney, New South Wales, Australia.,School of Women's and Children's Health, University of New South Wales Medicine and Health, University of New South Wales, Sydney, New South Wales, Australia
| | - Arlene M D'Silva
- School of Women's and Children's Health, University of New South Wales Medicine and Health, University of New South Wales, Sydney, New South Wales, Australia
| | - Karen Herbert
- Department of Physiotherapy, Randwick, Sydney Children's Hospital, Sydney, New South Wales, Australia
| | - James Howells
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, New South Wales, Australia
| | - Kate Carey
- School of Women's and Children's Health, University of New South Wales Medicine and Health, University of New South Wales, Sydney, New South Wales, Australia
| | - Tejaswi Kandula
- Department of Neurology, Randwick, Sydney Children's Hospital, Sydney, New South Wales, Australia
| | - Michelle A Farrar
- Department of Neurology, Randwick, Sydney Children's Hospital, Sydney, New South Wales, Australia.,School of Women's and Children's Health, University of New South Wales Medicine and Health, University of New South Wales, Sydney, New South Wales, Australia
| | - Cindy Shin-Yi Lin
- Translational Research Collective, Faculty of Medicine and Health, Brain and Mind Centre, University of Sydney, Sydney, New South Wales, Australia
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Palomés-Borrajo G, Badia J, Navarro X, Penas C. Nerve Excitability and Neuropathic Pain is Reduced by BET Protein Inhibition After Spared Nerve Injury. THE JOURNAL OF PAIN 2021; 22:1617-1630. [PMID: 34157407 DOI: 10.1016/j.jpain.2021.05.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 05/19/2021] [Accepted: 05/23/2021] [Indexed: 11/27/2022]
Abstract
Neuropathic pain is a common disability produced by enhanced neuronal excitability after nervous system injury. The pathophysiological changes that underlie the generation and maintenance of neuropathic pain require modifications of transcriptional programs. In particular, there is an induction of pro-inflammatory neuromodulators levels, and changes in the expression of ion channels and other factors intervening in the determination of the membrane potential in neuronal cells. We have previously found that inhibition of the BET proteins epigenetic readers reduced neuroinflammation after spinal cord injury. Within the present study we aimed to determine if BET protein inhibition may also affect neuroinflammation after a peripheral nerve injury, and if this would beneficially alter neuronal excitability and neuropathic pain. For this purpose, C57BL/6 female mice underwent spared nerve injury (SNI), and were treated with the BET inhibitor JQ1, or vehicle. Electrophysiological and algesimetry tests were performed on these mice. We also determined the effects of JQ1 treatment after injury on neuroinflammation, and the expression of neuronal components important for the maintenance of axon membrane potential. We found that treatment with JQ1 affected neuronal excitability and mechanical hyperalgesia after SNI in mice. BET protein inhibition regulated cytokine expression and reduced microglial reactivity after injury. In addition, JQ1 treatment altered the expression of SCN3A, SCN9A, KCNA1, KCNQ2, KCNQ3, HCN1 and HCN2 ion channels, as well as the expression of the Na+/K+ ATPase pump subunits. In conclusion, both, alteration of inflammation, and neuronal transcription, could be the responsible epigenetic mechanisms for the reduction of excitability and hyperalgesia observed after BET inhibition. Inhibition of BET proteins is a promising therapy for reducing neuropathic pain after neural injury.
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Affiliation(s)
- Georgina Palomés-Borrajo
- Institute of Neurosciences, Dept. Cell Biology, Physiology and Immunology, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Jordi Badia
- Institute of Neurosciences, Dept. Cell Biology, Physiology and Immunology, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Xavier Navarro
- Institute of Neurosciences, Dept. Cell Biology, Physiology and Immunology, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Clara Penas
- Institute of Neurosciences, Dept. Cell Biology, Physiology and Immunology, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Universitat Autònoma de Barcelona, Bellaterra, Spain.
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14
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Turan Z, Zinnuroğlu M. Peripheral axonal excitability in hemiplegia related to subacute stroke. Turk J Med Sci 2020; 50:1983-1992. [PMID: 32682362 PMCID: PMC7775702 DOI: 10.3906/sag-2004-306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Accepted: 07/18/2020] [Indexed: 11/07/2022] Open
Abstract
Background/aim This study aims to investigate peripheral nerve excitability in patients with subacute stroke. Materials and methods The study was performed in 29 stroke patients within the subacute period and 29 healthy controls using QTRAC software and TRONDNF protocol. The threshold electrotonus, recovery cycle, stimulus-response, strength-duration, and current-threshold relationships were recorded. Results The membrane was more hyperpolarized, and excitability was decreased in the hemiplegic side. The impairment of inward rectifying channel function, degree of hyperpolarization, and decrease of excitability were directly related to the Brunnstrom stages, which were more pronounced in lower stages. Conclusion The lower motor neurons were affected at the level of axonal channels as a result of upper motor neuron lesions. It can be due to dying back neuropathy, homeostasis, and neurovascular regulation changes in the axonal environment, activity-dependent plastic changes, loss of drive coming from the central nervous system, or a combination of these factors.
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Affiliation(s)
- Zeynep Turan
- Department of Physical Medicine and Rehabilitation, Koç University Hospital, İstanbul, Turkey
| | - Murat Zinnuroğlu
- Department of Physical Medicine and Rehabilitation, Faculty of Medicine, Gazi University, Ankara, Turkey
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15
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Koźmiński W, Pera J. Involvement of the Peripheral Nervous System in Episodic Ataxias. Biomedicines 2020; 8:biomedicines8110448. [PMID: 33105744 PMCID: PMC7690566 DOI: 10.3390/biomedicines8110448] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 10/20/2020] [Accepted: 10/21/2020] [Indexed: 12/04/2022] Open
Abstract
Episodic ataxias comprise a group of inherited disorders, which have a common hallmark—transient attacks of ataxia. The genetic background is heterogeneous and the causative genes are not always identified. Furthermore, the clinical presentation, including intraictal and interictal symptoms, as well as the retention and progression of neurological deficits, is heterogeneous. Spells of ataxia can be accompanied by other symptoms—mostly from the central nervous system. However, in some of episodic ataxias involvement of peripheral nervous system is a part of typical clinical picture. This review intends to provide an insight into involvement of peripheral nervous system in episodic ataxias.
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Affiliation(s)
- Wojciech Koźmiński
- Department of Neurology, University Hospital, ul. Jakubowskiego 2, 30-688 Krakow, Poland;
| | - Joanna Pera
- Department of Neurology, Jagiellonian University Medical College, ul. Botaniczna 3, 31-503 Krakow, Poland
- Correspondence:
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16
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Housley SN, Nardelli P, Powers RK, Rich MM, Cope TC. Chronic defects in intraspinal mechanisms of spike encoding by spinal motoneurons following chemotherapy. Exp Neurol 2020; 331:113354. [PMID: 32511953 PMCID: PMC7937189 DOI: 10.1016/j.expneurol.2020.113354] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 02/11/2020] [Accepted: 05/04/2020] [Indexed: 11/22/2022]
Abstract
Chemotherapy-induced sensorimotor disabilities, including gait and balance disorders, as well as physical fatigue often persist for months and sometimes years into disease free survival from cancer. While associated with impaired sensory function, chronic sensorimotor disorders might also depend on chemotherapy-induced defects in other neuron types. In this report, we extend consideration to motoneurons, which, if chronically impaired, would necessarily degrade movement behavior. The present study was undertaken to determine whether motoneurons qualify as candidate contributors to chronic sensorimotor disability independently from sensory impairment. We tested this possibility in vivo from rats 5 weeks following human-scaled treatment with one of the platinum-based compounds, oxaliplatin, widely used in chemotherapy for a variety of cancers. Action potential firing of spinal motoneurons responding to different fixed levels of electrode-current injection was measured in order to assess the neurons' intrinsic capacity for stimulus encoding. The encoding of stimulus duration and intensity corroborated in untreated control rats was severely degraded in oxaliplatin treated rats, in which motoneurons invariably exhibited erratic firing that was unsustained, unpredictable from one stimulus trial to the next, and unresponsive to changes in current strength. Direct measurements of interspike oscillations in membrane voltage combined with computer modeling pointed to aberrations in subthreshold conductances as a plausible contributor to impaired firing behavior. These findings authenticate impaired spike encoding as a candidate contributor to, in the case of motoneurons, deficits in mobility and fatigue. Aberrant firing also becomes a deficit worthy of testing in other CNS neurons as a potential contributor to perceptual and cognitive disorders induced by chemotherapy in patients.
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Affiliation(s)
- Stephen N Housley
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30318, USA
| | - Paul Nardelli
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30318, USA
| | - Randal K Powers
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA
| | - Mark M Rich
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, OH 45435, USA
| | - Timothy C Cope
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30318, USA; Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30318, USA.
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17
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Kandula T, Park SB, Carey KA, Lin CSY, Farrar MA. Peripheral nerve maturation and excitability properties from early childhood: Comparison of motor and sensory nerves. Clin Neurophysiol 2020; 131:2452-2459. [PMID: 32829292 DOI: 10.1016/j.clinph.2020.06.035] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 06/11/2020] [Accepted: 06/28/2020] [Indexed: 10/23/2022]
Abstract
OBJECTIVE Understanding of maturational properties of sensory and motor axons is of central importance for determining the impact of nerve changes in health and in disease in children and young adults. METHODS This study investigated maturation of sensory axons using axonal excitability parameters of the median nerve in 47 children, adolescents and young adults (25 males, 22 females; age range 1-25 years) and compared them to concurrent motor studies. RESULTS The overall pattern of sensory maturation was similar to motor maturation demonstrating prolongation of the strength duration time constant (P < 0.001), reduction of hyperpolarising threshold electrotonus (P = 0.002), prolongation of accommodation half-time (P = 0.005), reduction in hyperpolarising current-threshold slope (P = 0.03), and a shift to the right of the refractory cycle curve (P < 0.001), reflecting changes in passive membrane properties and fast potassium channel conductances. Sensory axons, however, had a greater increase in strength duration time constant and more attenuated changes in depolarising threshold electrotonus and current-threshold parameters, attributable to a more depolarised resting membrane potential evident from early childhood and maintained in adults. Peak amplitude was established early in sensory axons whereas motor amplitude increased with age (P < 0.001), reflecting non-axonal motor unit changes. CONCLUSIONS Maturational trajectories of sensory and motor axons were broadly parallel in children and young adults, but sensory-motor differences were initiated early in maturation. SIGNIFICANCE Identifying the evolution of biophysical changes within and between sensory and motor axons through childhood and adolescence is fundamental to understanding developmental physiology and interpreting disease-related changes in immature nerves.
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Affiliation(s)
- Tejaswi Kandula
- School of Women's and Children's Health, UNSW Medicine, UNSW Sydney, High Street, Randwick, NSW 2031, Australia; Department of Neurology, Sydney Children's Hospital, High Street, Randwick, NSW 2031, Australia
| | - Susanna B Park
- Brain and Mind Centre, Faculty of Medicine and Health, University of Sydney, 94 Mallett Street, Camperdown, NSW 2051, Australia
| | - Kate A Carey
- School of Women's and Children's Health, UNSW Medicine, UNSW Sydney, High Street, Randwick, NSW 2031, Australia
| | - Cindy S-Y Lin
- Brain and Mind Centre, Faculty of Medicine and Health, University of Sydney, 94 Mallett Street, Camperdown, NSW 2051, Australia
| | - Michelle A Farrar
- School of Women's and Children's Health, UNSW Medicine, UNSW Sydney, High Street, Randwick, NSW 2031, Australia; Department of Neurology, Sydney Children's Hospital, High Street, Randwick, NSW 2031, Australia.
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18
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Trinh T, Park SB, Murray J, Pickering H, Lin CSY, Martin A, Friedlander M, Kiernan MC, Goldstein D, Krishnan AV. Neu-horizons: neuroprotection and therapeutic use of riluzole for the prevention of oxaliplatin-induced neuropathy-a randomised controlled trial. Support Care Cancer 2020; 29:1103-1110. [PMID: 32607598 DOI: 10.1007/s00520-020-05591-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Accepted: 06/23/2020] [Indexed: 12/22/2022]
Abstract
TRIAL DESIGN Peripheral neuropathy is a commonly reported adverse effect of oxaliplatin treatment, representing a significant limitation which may require discontinuation of effective therapy. The present study investigated the neuroprotective potential of riluzole in patients undergoing oxaliplatin treatment in a randomised-controlled trial comparing riluzole and placebo-control. METHODS Fifty-two patients (17 females, 58.1 ± 12.7 years) receiving oxaliplatin treatment were randomised into either a treatment (50 mg riluzole) or lactose placebo group. The primary outcome measure was the total neuropathy score-reduced (TNSr). Secondary outcome measures include nerve excitability measures, 9-hole pegboard and FACT-GOG NTX questionnaire. Patients were assessed at baseline, pre-cycle 10 or 12, 4-week and 12-week post-treatment. RESULTS Both the treatment and placebo groups developed objective and patient reported evidence of neurotoxicity over the course of oxaliplatin treatment, although there were no significant differences across any parameters between the two groups. However, across follow-up assessments, the treatment group experienced greater neuropathy, represented by a higher TNSr score at 4-week post-chemotherapy of 8.3 ± 2.7 compared with 4.6 ± 3.6 (p = 0.032) which was sustained at 12-week post-treatment (p = 0.089). Similarly, patients in the treatment group reported worse symptoms with a FACT-GOG NTX score of 37.4 ± 10.2 compared with 43.3 ± 7.4 (p = 0.02) in the placebo group at 4-week post-treatment. CONCLUSION This study is the first to provide an objective clinical investigation of riluzole in oxaliplatin-induced peripheral neuropathy employing both functional and neurophysiological measures. Although the recruitment target was not reached, the results do not show any benefit of riluzole in minimising neuropathy and may suggest that riluzole worsens neuropathy associated with oxaliplatin treatment.
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Affiliation(s)
- Terry Trinh
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - Susanna B Park
- Brain and Mind Centre, University of Sydney, Sydney, Australia
| | - Jenna Murray
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - Hannah Pickering
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - Cindy S-Y Lin
- Brain and Mind Centre, University of Sydney, Sydney, Australia
| | - Andrew Martin
- National Health and Medical Research Centre Clinical Trials Centre, University of Sydney, Sydney, Australia
| | - Michael Friedlander
- Department of Medical Oncology, Prince of Wales Hospital, Randwick, Sydney, Australia
| | | | - David Goldstein
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia.,Department of Medical Oncology, Prince of Wales Hospital, Randwick, Sydney, Australia
| | - Arun V Krishnan
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia. .,Department of Neurological Sciences, Prince of Wales Hospital, Level 2 High Street, Randwick, Sydney, NSW, 2031, Australia.
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19
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Casanova I, Caetano A, Díaz A, Conceição I, Brum M, de Carvalho M. Motor excitability measurements in early stage familial amyloid polyneuropathy: The influence of tafamidis treatment. Neurophysiol Clin 2020; 50:145-153. [PMID: 32507631 DOI: 10.1016/j.neucli.2020.04.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2020] [Revised: 04/20/2020] [Accepted: 04/21/2020] [Indexed: 11/17/2022] Open
Abstract
OBJECTIVE To test motor fiber excitability in early affected patients with transthyretin (TTR)-type familial amyloid polyneuropathy (TTR-FAP) before and during tafamidis treatment. METHODS We examined the left median nerve of 21 healthy-matched controls and 10 early affected TTR-FAP patients using the automated threshold-tracking program, QTRAC. TTR-FAP patients were tested one day before the initiation of tafamidis treatment, 3 and 6 months later. RESULTS The drug was well-tolerated in all patients; there was no drop-out. No statistical difference was found between healthy controls and TTR-FAP patients at study entry. On treatment, both stimulus intensity for 50% of the maximal motor response and rheobase increased significantly from entry to the last evaluation at 6 months (P<0.05). Strength duration time constant decreased significantly from the 3rd to the 6th month of evaluation (P<0.05). There was also a "fanning-out" effect on the late depolarization phase (TEd 90-100ms) as well as a shortened relative refractory period from study entry to the 6th month of evaluation. CONCLUSIONS Threshold-tracking of median nerve motor fibers is not a helpful technique for the early diagnosis of TTR-FAP patients. Tafamidis was well-tolerated. We observed possible membrane hyperpolarization during treatment. Threshold tracking can contribute to documenting the action of new drugs to treat neuropathies. Tafamidis may change nerve electrical properties by reducing the burden of amyloid fibrils.
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Affiliation(s)
- Isabel Casanova
- Instituto de Fisiologia, Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - André Caetano
- Instituto de Fisiologia, Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal; Department of Neurology, Hospital de Egas Moniz, Centro Hospitalar de Lisboa Ocidental, Lisbon, Portugal
| | - Andrés Díaz
- Instituto de Fisiologia, Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal; Hospital Universitario Fundación Santa Fe de Bogotá, Bogotá, Colombia
| | - Isabel Conceição
- Instituto de Fisiologia, Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal; Department of Neurosciences, Centro Hospitalar Universário Lisboa-Norte, Hospital de Santa Maria, Lisbon, Portugal
| | - Marisa Brum
- Instituto de Fisiologia, Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal; Department of Neurology, Centro Hospitalar de Lisboa Central, Lisbon, Portugal
| | - Mamede de Carvalho
- Instituto de Fisiologia, Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal; Department of Neurosciences, Centro Hospitalar Universário Lisboa-Norte, Hospital de Santa Maria, Lisbon, Portugal.
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20
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Lin Y, Lin CS, Chang T, Lee J, Tani J, Chen H, Sung J. Early sensory neurophysiological changes in prediabetes. J Diabetes Investig 2020; 11:458-465. [PMID: 31563156 PMCID: PMC7078118 DOI: 10.1111/jdi.13151] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 09/19/2019] [Accepted: 09/25/2019] [Indexed: 12/14/2022] Open
Abstract
AIMS/INTRODUCTION To elucidate whether axonal changes arise in the prediabetic state and to find a biomarker for early detection of neurophysiological changes. MATERIALS AND METHODS We enrolled asymptomatic diabetes patients, as well as prediabetic and normoglycemic individuals to test sensory nerve excitability, and we analyzed those findings and their correlation with clinical profiles. RESULTS In nerve excitability tests, superexcitability in the recovery cycle showed increasing changes in the normoglycemic, prediabetes and diabetes cohorts (-19.09 ± 4.56% in normoglycemia, -22.39 ± 3.16% in prediabetes and -23.71 ± 5.15% in diabetes, P = 0.002). Relatively prolonged distal sensory latency was observed in the median nerve (3.12 ± 0.29 ms in normoglycemia, 3.23 ± 0.38 ms in prediabetes and 3.45 ± 0.43 ms in diabetes, P = 0.019). Superexcitability was positively correlated with fasting plasma glucose (r = 0.291, P = 0.009) and glycated hemoglobin (r = 0.331, P = 0.003) in all participants. CONCLUSIONS Sensory superexcitability and latencies are the most sensitive parameters for detecting preclinical physiological dysfunction in prediabetes. In addition, changes in favor of superexcitability were positively correlated with glycated hemoglobin for all participants. These results suggest that early axonal changes start in the prediabetic stage, and that the monitoring strategy for polyneuropathy should start as early as prediabetes.
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Affiliation(s)
- Yi‐Chen Lin
- Department of NeurologyTaipei Municipal Wanfang HospitalTaipei Medical UniversityTaipeiTaiwan
- Neuroscience InstituteTaipei Medical UniversityTaipeiTaiwan
| | - Cindy Shin‐Yi Lin
- Neural Regenerative MedicineCollege of Medical Science and TechnologyTaipei Medical University and National Health Research InstitutesTaipeiTaiwan
- The Kam Ling Barbara Lo Chair in Neurodegenerative DisordersCentral Clinical SchoolFaculty of Medicine and Health, Brain and Mind CenterThe University of SydneySydneyAustralia
| | - Tsui‐San Chang
- Department of NeurologyTaipei Municipal Wanfang HospitalTaipei Medical UniversityTaipeiTaiwan
- Neuroscience InstituteTaipei Medical UniversityTaipeiTaiwan
- Department of NeurologySchool of Medicine, College of MedicineTaipei Medical UniversityTaipeiTaiwan
| | - Jing‐Er Lee
- Department of NeurologyTaipei Municipal Wanfang HospitalTaipei Medical UniversityTaipeiTaiwan
- Neuroscience InstituteTaipei Medical UniversityTaipeiTaiwan
| | - Jowy Tani
- Department of NeurologyTaipei Municipal Wanfang HospitalTaipei Medical UniversityTaipeiTaiwan
- Neuroscience InstituteTaipei Medical UniversityTaipeiTaiwan
- Neural Regenerative MedicineCollege of Medical Science and TechnologyTaipei Medical University and National Health Research InstitutesTaipeiTaiwan
- Ph.D. Program for Neural Regenerative MedicineCollege of Medical Science and TechnologyTaipei Medical University and National Health Research InstitutesTaipeiTaiwan
| | - Hung‐Ju Chen
- Department of NeurologyTaipei Municipal Wanfang HospitalTaipei Medical UniversityTaipeiTaiwan
- Neuroscience InstituteTaipei Medical UniversityTaipeiTaiwan
| | - Jia‐Ying Sung
- Department of NeurologyTaipei Municipal Wanfang HospitalTaipei Medical UniversityTaipeiTaiwan
- Neuroscience InstituteTaipei Medical UniversityTaipeiTaiwan
- Department of NeurologySchool of Medicine, College of MedicineTaipei Medical UniversityTaipeiTaiwan
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21
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Yan A, Issar T, Tummanapalli SS, Markoulli M, Kwai NCG, Poynten AM, Krishnan AV. Relationship between corneal confocal microscopy and markers of peripheral nerve structure and function in Type 2 diabetes. Diabet Med 2020; 37:326-334. [PMID: 30897245 DOI: 10.1111/dme.13952] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/18/2019] [Indexed: 01/03/2023]
Abstract
AIMS To investigate changes in corneal nerve morphology in Type 2 diabetes and to establish relationships between in vivo corneal confocal microscopy and markers of peripheral nerve structure and function. PARTICIPANTS AND METHODS We recruited 57 participants with Type 2 diabetes and 26 healthy controls of similar age and sex distribution. We also recruited a disease control group of 54 participants with Type 1 diabetes. All participants were assessed for distal symmetrical polyneuropathy using the Total Neuropathy Score. In vivo corneal confocal microscopy was used to assess corneal nerve fibre length, corneal nerve fibre density, corneal nerve branch density and inferior whorl length. Peripheral nerve structure was assessed using median nerve ultrasonography. Large fibre function was assessed according to median nerve axonal excitability. Small fibre function was assessed using SudoscanTM and the Survey of Autonomic Symptoms. RESULTS Corneal nerve fibre length, fibre density and branch density and inferior whorl length were significantly lower in individuals with Type 2 diabetes compared to controls (P<0.001 for all). In the Type 2 diabetes cohort, correlations were observed between neuropathy severity and corneal nerve fibre density (P=0.004), corneal nerve branch density (P=0.003), corneal nerve fibre length (P=0.002) and inferior whorl length (P=0.01). Significant correlations were observed between corneal confocal outcomes and axonal excitability measurements. No association was found between corneal confocal microscopy and median nerve cross-sectional area, Sudoscan measurements or the Survey of Autonomic Symptoms. CONCLUSIONS This study demonstrated significant changes in corneal nerves in individuals with Type 2 diabetes. Reductions in corneal nerve measures correlated with increasing neuropathy severity. Associations were found between corneal confocal microscopy and markers of voltage-gated potassium channel function.
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Affiliation(s)
- A Yan
- Prince of Wales Clinical School, University of New South Wales, Sydney, NSW, Australia
| | - T Issar
- Prince of Wales Clinical School, University of New South Wales, Sydney, NSW, Australia
| | - S S Tummanapalli
- School of Optometry and Vision Science, University of New South Wales, Sydney, NSW, Australia
| | - M Markoulli
- School of Optometry and Vision Science, University of New South Wales, Sydney, NSW, Australia
| | - N C G Kwai
- School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - A M Poynten
- Department of Endocrinology, Prince of Wales Hospital, Sydney, NSW, Australia
| | - A V Krishnan
- Prince of Wales Clinical School, University of New South Wales, Sydney, NSW, Australia
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22
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Kandula T, Farrar MA, Cohn RJ, Carey KA, Johnston K, Kiernan MC, Krishnan AV, Park SB. Changes in long term peripheral nerve biophysical properties in childhood cancer survivors following neurotoxic chemotherapy. Clin Neurophysiol 2020; 131:783-790. [PMID: 32066096 DOI: 10.1016/j.clinph.2019.12.411] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2019] [Revised: 11/14/2019] [Accepted: 12/07/2019] [Indexed: 12/28/2022]
Abstract
OBJECTIVE In the context of increasing numbers of childhood cancer survivors (CCS), this study aimed to enhance understanding of the biophysical basis for long term chemotherapy induced peripheral neuropathy from different chemotherapy agents in CCS. METHODS Detailed cross-sectional neurophysiological examination, using median nerve axonal excitability studies, alongside clinical assessments, in 103 long term CCS (10.5 ± 0.6 years post-treatment). RESULTS Cisplatin treated CCS (n = 16) demonstrated multiple sensory axonal excitability changes including increased threshold (P < 0.05), alterations in depolarising and hyperpolarising threshold electrotonus (P < 0.05) and reduction in resting and minimum IV slope (P < 0.01). Vincristine treated CCS (n = 73) were comparable to controls, except for prolonged distal motor latency (P = 0.001). No differences were seen in the non-neurotoxic chemotherapy group (n = 14). Abnormalities were more evident in the cisplatin subgroup with greater clinical neuropathy manifestations. CONCLUSION Persistent long term changes in axonal biophysical properties vary with different chemotherapy agents, most evident after cisplatin exposure. Longitudinal studies of nerve function during chemotherapy treatment are required to further evaluate these differences and their mechanistic basis. SIGNIFICANCE This study provides a unique biophysical perspective for persistent cisplatin related neurotoxicity in children, previously under recognised.
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Affiliation(s)
- T Kandula
- School of Women's and Children's Health, UNSW Medicine, UNSW Sydney, Australia; Department of Neurology, Sydney Children's Hospital, Australia
| | - M A Farrar
- School of Women's and Children's Health, UNSW Medicine, UNSW Sydney, Australia; Department of Neurology, Sydney Children's Hospital, Australia
| | - R J Cohn
- Kids Cancer Centre, Sydney Children's Hospital, Australia
| | - K A Carey
- School of Women's and Children's Health, UNSW Medicine, UNSW Sydney, Australia
| | - K Johnston
- Kids Cancer Centre, Sydney Children's Hospital, Australia
| | - M C Kiernan
- Brain & Mind Centre, University of Sydney, Australia
| | - A V Krishnan
- Prince of Wales Clinical School, UNSW Medicine, UNSW Sydney, Australia
| | - S B Park
- Brain & Mind Centre, University of Sydney, Australia; Prince of Wales Clinical School, UNSW Medicine, UNSW Sydney, Australia.
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23
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Tummanapalli SS, Issar T, Kwai N, Poynten A, Krishnan AV, Willcox M, Markoulli M. Association of corneal nerve loss with markers of axonal ion channel dysfunction in type 1 diabetes. Clin Neurophysiol 2020; 131:145-154. [DOI: 10.1016/j.clinph.2019.09.029] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 08/29/2019] [Accepted: 09/29/2019] [Indexed: 01/06/2023]
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24
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Tummanapalli SS, Issar T, Kwai N, Pisarcikova J, Poynten AM, Krishnan AV, Willcox MDP, Markoulli M. A Comparative Study on the Diagnostic Utility of Corneal Confocal Microscopy and Tear Neuromediator Levels in Diabetic Peripheral Neuropathy. Curr Eye Res 2019; 45:921-930. [DOI: 10.1080/02713683.2019.1705984] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
| | - Tushar Issar
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - Natalie Kwai
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - Jana Pisarcikova
- School of Optometry & Vision Science, University of New South Wales, Sydney, Australia
| | - Ann M. Poynten
- Department of Endocrinology, Prince of Wales Hospital, Sydney, Australia
| | - Arun V. Krishnan
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - Mark D. P. Willcox
- School of Optometry & Vision Science, University of New South Wales, Sydney, Australia
| | - Maria Markoulli
- School of Optometry & Vision Science, University of New South Wales, Sydney, Australia
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25
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Alberti P, Canta A, Chiorazzi A, Fumagalli G, Meregalli C, Monza L, Pozzi E, Ballarini E, Rodriguez-Menendez V, Oggioni N, Sancini G, Marmiroli P, Cavaletti G. Topiramate prevents oxaliplatin-related axonal hyperexcitability and oxaliplatin induced peripheral neurotoxicity. Neuropharmacology 2019; 164:107905. [PMID: 31811874 DOI: 10.1016/j.neuropharm.2019.107905] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 11/26/2019] [Accepted: 12/03/2019] [Indexed: 12/15/2022]
Abstract
Oxaliplatin (OHP) Induced Peripheral Neurotoxicity (OIPN) is one of the dose-limiting toxicities of the drug and these adverse effects limit cancer therapy with L-OHP, used for colorectal cancer treatment. Acute neurotoxicity consists of symptoms that are the hallmarks of a transient axonal hyperexcitability; chronic neurotoxicity has a clinical picture compatible with a length-dependent sensory neuropathy. Acute OIPN pathogenesis has been linked to sodium voltage-operated channels (Na + VOC) dysfunction and it has been advocated as a possible predisposing factor to chronic neurotoxicity. We tested if topiramate (TPM), a well-known Na + VOC modulator, was able to modify acute as well as chronic OIPN. The project was divided into two parts. In Experiment 1 we tested by means of Nerve Excitability Testing (NET) a cohort of female Wistar rats to assess TPM effects after a single OHP administration (5 mg/kg, iv). In Experiment 2 we assessed TPM effects after chronic OHP treatment (5 mg/kg, 2qw4ws, iv) using NET, nerve conduction studies (NCS), behavioral tests and neuropathology (caudal nerve morphometry and morphology and Intraepidermal Nerve Fiber [IENF] density). In Experiment 1 TPM was able to prevent OHP effects on Na + VOC: OHP treatment induced a highly significant reduction of the sensory nerve's threshold, during the superexcitability period (p-value = 0.008), whereas TPM co-administration prevented this effect. In Experiment 2 we verified that TPM was able to prevent not only acute phenomena, but also to completely prevent chronic OIPN. This latter observation was supported by a multimodal approach: in fact, only OHP group showed altered findings compared to CTRL group at a neurophysiological (proximal caudal nerve sensory nerve action potential [SNAP] amplitude, p-value = 0.001; distal caudal nerve SNAP amplitude, p-value<0.001, distal caudal nerve sensory conduction velocity, p-value = 0.04), behavioral (mechanical threshold, p-value 0.003) and neuropathological levels (caudal nerve fibers density, p-value 0.001; IENF density, p-value <0.001). Our data show that TPM is a promising drug to prevent both acute and chronic OIPN. These findings have a high translational potential, since they were obtained using outcome measures that match clinical practice and TPM is already approved for clinical use being free from detrimental interaction with OHP anticancer properties.
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Affiliation(s)
- Paola Alberti
- Experimental Neurology Unit, School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy; NeuroMI (Milan Center for Neuroscience), School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy.
| | - Annalisa Canta
- Experimental Neurology Unit, School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy; NeuroMI (Milan Center for Neuroscience), School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy
| | - Alessia Chiorazzi
- Experimental Neurology Unit, School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy; NeuroMI (Milan Center for Neuroscience), School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy
| | - Giulia Fumagalli
- Experimental Neurology Unit, School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy; NeuroMI (Milan Center for Neuroscience), School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy; PhD program in Neuroscience, School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy
| | - Cristina Meregalli
- Experimental Neurology Unit, School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy; NeuroMI (Milan Center for Neuroscience), School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy
| | - Laura Monza
- Experimental Neurology Unit, School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy; NeuroMI (Milan Center for Neuroscience), School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy; Human Physiology Lab., School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy
| | - Eleonora Pozzi
- Experimental Neurology Unit, School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy; NeuroMI (Milan Center for Neuroscience), School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy; PhD program in Neuroscience, School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy
| | - Elisa Ballarini
- Experimental Neurology Unit, School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy; NeuroMI (Milan Center for Neuroscience), School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy
| | - Virginia Rodriguez-Menendez
- Experimental Neurology Unit, School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy; NeuroMI (Milan Center for Neuroscience), School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy
| | - Norberto Oggioni
- Experimental Neurology Unit, School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy; NeuroMI (Milan Center for Neuroscience), School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy
| | - Giulio Sancini
- NeuroMI (Milan Center for Neuroscience), School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy; Human Physiology Lab., School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy
| | - Paola Marmiroli
- Experimental Neurology Unit, School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy; NeuroMI (Milan Center for Neuroscience), School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy
| | - Guido Cavaletti
- Experimental Neurology Unit, School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy; NeuroMI (Milan Center for Neuroscience), School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy
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26
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Daur N, Zhang Y, Nadim F, Bucher D. Mutual Suppression of Proximal and Distal Axonal Spike Initiation Determines the Output Patterns of a Motor Neuron. Front Cell Neurosci 2019; 13:477. [PMID: 31708748 PMCID: PMC6819512 DOI: 10.3389/fncel.2019.00477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 10/10/2019] [Indexed: 11/13/2022] Open
Abstract
Axonal spike initiation at sites far from somatodendritic integration occurs in a range of systems, but its contribution to neuronal output activity is not well understood. We studied the interactions of distal and proximal spike initiation in an unmyelinated motor axon of the stomatogastric nervous system in the lobster, Homarus americanus. The peripheral axons of the pyloric dilator (PD) neurons generate tonic spiking in response to dopamine application. Centrally generated bursting activity and peripheral spike initiation had mutually suppressive effects. The two PD neurons and the electrically coupled oscillatory anterior burster (AB) neuron form the pacemaker ensemble of the pyloric central pattern generator, and antidromic invasion of central compartments by peripherally generated spikes caused spikelets in AB. Antidromic spikes suppressed burst generation in an activity-dependent manner: slower rhythms were diminished or completely disrupted, while fast rhythmic activity remained robust. Suppression of bursting was based on interference with the underlying slow wave oscillations in AB and PD, rather than a direct effect on spike initiation. A simplified multi-compartment circuit model of the pacemaker ensemble replicated this behavior. Antidromic activity disrupted slow wave oscillations by resetting the inward and outward current trajectories in each spike interval. Centrally generated bursting activity in turn suppressed peripheral spike initiation in an activity-dependent manner. Fast bursting eliminated peripheral spike initiation, while slower bursting allowed peripheral spike initiation to continue during the intervals between bursts. The suppression of peripheral spike initiation was associated with a small after-hyperpolarization in the sub-millivolt range. A realistic model of the PD axon replicated this behavior and showed that a sub-millivolt cumulative after-hyperpolarization across bursts was sufficient to eliminate peripheral spike initiation. This effect was based on the dynamic interaction between slow activity-dependent hyperpolarization caused by the Na+/K+-pump and inward rectification through the hyperpolarization-activated inward current, I h . These results demonstrate that interactions between different spike initiation sites based on spike propagation can shift the relative contributions of different types of activity in an activity-dependent manner. Therefore, distal axonal spike initiation can play an important role in shaping neural output, conditional on the relative level of centrally generated activity.
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Affiliation(s)
- Nelly Daur
- Federated Department of Biological Sciences, New Jersey Institute of Technology and Rutgers University-Newark, Newark, NJ, United States
| | - Yang Zhang
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, NJ, United States
| | - Farzan Nadim
- Federated Department of Biological Sciences, New Jersey Institute of Technology and Rutgers University-Newark, Newark, NJ, United States.,Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, NJ, United States
| | - Dirk Bucher
- Federated Department of Biological Sciences, New Jersey Institute of Technology and Rutgers University-Newark, Newark, NJ, United States
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27
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Bell JM, Lorenz C, Jones KE. Nerve excitability differences in slow and fast motor axons of the rat: more than just Ih. J Neurophysiol 2019; 122:1728-1734. [PMID: 31533011 DOI: 10.1152/jn.00269.2019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The objective was to determine biophysical differences between fast and slow motor axons using threshold tracking and demonstrate confounds related to anesthetic. Nerve excitability of motor axons innervating the slow-twitch soleus (SOL) and fast-twitch tibialis anterior (TA) muscles was tested. The experiments were conducted with pentobarbital sodium (SP) anesthetic and compared with previous results that used ketamine-xylazine (KX). Nerve excitability indices measured with SP show definitive differences between TA and SOL motor axons that extend beyond previous reports. Nerve excitability indices sensitive to changes in Ih indicated an increase in SOL axons compared with TA axons [e.g., S3 t = 7.949 (df = 10), P < 0.001; hyperpolarizing threshold electrotonus (90-100 ms), t = 2.659 (df = 20); P = 0.01; hyperpolarizing I/V slope, t = 4.308 (df = 19); P < 0.001]. SOL axons also had a longer strength-duration time constant [t = 3.35 (df = 20); P = 0.003] and a longer and larger magnitude relative refractory period [RRP (ms) t = 3.53 (df = 12); P = 0.004; Refractoriness at 2 ms, t = 0.0055 (df = 9); P = 0.006]. Anesthetic choice affected many measures of peripheral nerve excitability with differences most apparent in tests of threshold electrotonus and recovery cycle. For example, recovery cycle with KX lacked a clear superexcitable and late subexcitable period. We conclude that KX had a confounding effect on nerve excitability results consistent with ischemic depolarization. Results using SP revealed the full extent of differences in nerve excitability measures between putative slow and fast motor axons of the rat. These results provide empirical evidence, beyond conduction velocity, that the biophysical properties of motor axons vary with the type of muscle fiber innervated. These differences suggest that fast axons may be predisposed to dysfunction during hyperpolarizing stresses, e.g., electrogenic sodium pumping following sustained impulse conduction.NEW & NOTEWORTHY Nerve excitability testing is a tool used to provide insight into the properties of ion channels in peripheral nerves. It is used clinically to assess pathophysiology of axons. Researchers customarily think of motor axons as homogeneous; however, we demonstrate there are clear differences between fast and slow axons in the rat. This is important for interpreting results with selective motor neuronopathy, like aging where fast axons are at high risk of degeneration.
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Affiliation(s)
- James M Bell
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada.,Department of Computing Science, University of Alberta, Edmonton, Alberta, Canada
| | - Chad Lorenz
- Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Kelvin E Jones
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada.,Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, Alberta, Canada
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28
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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: 59] [Impact Index Per Article: 11.8] [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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29
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Nielson Hoberg T, Frahm S, Hennings K, Arendt‐Nielsen L, Dahl Mørch C. Assessing the modulation of cutaneous sensory fiber excitability using a fast perception threshold tracking technique. Muscle Nerve 2019; 60:367-375. [DOI: 10.1002/mus.26520] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 05/14/2019] [Accepted: 05/14/2019] [Indexed: 12/19/2022]
Affiliation(s)
- Tatiana Nielson Hoberg
- Department of Health Science and TechnologyCenter for Sensory‐Motor Interaction (SMI), Aalborg University Fredrik Bajers Vej 7 D3, 9220 Aalborg Ø Denmark
| | - Steffen Frahm
- Center for Neuroplasticity and Pain, SMI, Department of Health Science and TechnologyAalborg University Aalborg Denmark
| | - Kristian Hennings
- Department of Health Science and TechnologyCenter for Sensory‐Motor Interaction (SMI), Aalborg University Fredrik Bajers Vej 7 D3, 9220 Aalborg Ø Denmark
| | - Lars Arendt‐Nielsen
- Department of Health Science and TechnologyCenter for Sensory‐Motor Interaction (SMI), Aalborg University Fredrik Bajers Vej 7 D3, 9220 Aalborg Ø Denmark
- Center for Neuroplasticity and Pain, SMI, Department of Health Science and TechnologyAalborg University Aalborg Denmark
| | - Carsten Dahl Mørch
- Department of Health Science and TechnologyCenter for Sensory‐Motor Interaction (SMI), Aalborg University Fredrik Bajers Vej 7 D3, 9220 Aalborg Ø Denmark
- Center for Neuroplasticity and Pain, SMI, Department of Health Science and TechnologyAalborg University Aalborg Denmark
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30
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Alberti P. Platinum-drugs induced peripheral neurotoxicity: clinical course and preclinical evidence. Expert Opin Drug Metab Toxicol 2019; 15:487-497. [DOI: 10.1080/17425255.2019.1622679] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Paola Alberti
- NeuroMI (Milan Center for Neuroscience), Milan, Italy
- School of Medicine and Surgery, University of Milano-Bicocca, Milan, Italy
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31
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Garg N, Park SB, Howells J, Vucic S, Yiannikas C, Mathey EK, Nguyen T, Noto Y, Barnett MH, Krishnan AV, Spies J, Bostock H, Pollard JD, Kiernan MC. Conduction block in immune-mediated neuropathy: paranodopathy versus axonopathy. Eur J Neurol 2019; 26:1121-1129. [PMID: 30882969 DOI: 10.1111/ene.13953] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 03/11/2019] [Indexed: 12/15/2022]
Abstract
BACKGROUND AND PURPOSE Conduction block is a pathognomonic feature of immune-mediated neuropathies. The aim of this study was to advance understanding of pathophysiology and conduction block in chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN). METHODS A multimodal approach was used, incorporating clinical phenotyping, neurophysiology, immunohistochemistry and structural assessments. RESULTS Of 49 CIDP and 14 MMN patients, 25% and 79% had median nerve forearm block, respectively. Clinical scores were similar in CIDP patients with and without block. CIDP patients with median nerve block demonstrated markedly elevated thresholds and greater threshold changes in threshold electrotonus, whilst those without did not differ from healthy controls in electrotonus parameters. In contrast, MMN patients exhibited marked increases in superexcitability. Nerve size was similar in both CIDP groups at the site of axonal excitability. However, CIDP patients with block demonstrated more frequent paranodal serum binding to teased rat nerve fibres. In keeping with these findings, mathematical modelling of nerve excitability recordings in CIDP patients with block support the role of paranodal dysfunction and enhanced leakage of current between the node and internode. In contrast, changes in MMN probably resulted from a reduction in ion channel density along axons. CONCLUSIONS The underlying pathologies in CIDP and MMN are distinct. Conduction block in CIDP is associated with paranodal dysfunction which may be antibody-mediated in a subset of patients. In contrast, MMN is characterized by channel dysfunction downstream from the site of block.
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Affiliation(s)
- N Garg
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia.,Department of Neurology, Royal Prince Alfred Hospital, Sydney, NSW, Australia
| | - S B Park
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - J Howells
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - S Vucic
- Departments of Neurology and Neurophysiology, Westmead Hospital, University of Sydney, Sydney, NSW, Australia
| | - C Yiannikas
- Department of Neurology, Concord and Royal North Shore Hospitals, University of Sydney, Sydney, NSW, Australia
| | - E K Mathey
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - T Nguyen
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - Y Noto
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - M H Barnett
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia.,Department of Neurology, Royal Prince Alfred Hospital, Sydney, NSW, Australia
| | - A V Krishnan
- Prince of Wales Clinical School, University of New South Wales, Sydney, NSW, Australia
| | - J Spies
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia.,Department of Neurology, Royal Prince Alfred Hospital, Sydney, NSW, Australia
| | - H Bostock
- MRC Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, London, UK.,Institute of Neurology, University College London, London, UK
| | - J D Pollard
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia.,Department of Neurology, Royal Prince Alfred Hospital, Sydney, NSW, Australia
| | - M C Kiernan
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia.,Department of Neurology, Royal Prince Alfred Hospital, Sydney, NSW, Australia
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32
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Marmoy OR, Furlong PL, Moore CEG. Upper and lower limb motor axons demonstrate differential excitability and accommodation to strong hyperpolarizing currents during induced hyperthermia. J Neurophysiol 2019; 121:2061-2070. [PMID: 30917073 DOI: 10.1152/jn.00464.2018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Length-dependent peripheral neuropathy typically involves the insidious onset of sensory loss in the lower limbs before later progressing proximally. Recent evidence proposes hyperpolarization-activated cyclic nucleotide-gated (HCN) channels as dysfunctional in rodent models of peripheral neuropathy, and therefore differential expression of HCN channels in the lower limbs was hypothesized as a pathophysiological mechanism accounting for the pattern of symptomatology within this study. We studied six healthy participants, using motor axon excitability including strong and long [-70% and -100% hyperpolarizing threshold electrotonus (TEh)] hyperpolarizing currents to preferably study HCN channel function from the median and tibial nerves from high (40%) and low (20%) threshold. This was recorded at normothermia (~32°C) and then repeated during hyperthermia (~40°C) as an artificial hyperpolarizing axon stress. Significant differences between recovery cycle, superexcitability, accommodation to small depolarizing currents, and alterations in late stages of the inward-rectifying currents of strongest (-70% and -100% TEh) currents were observed in the lower limbs during hyperthermia. We demonstrate differences in late IH current flow, which implies higher expression of HCN channel isoforms. The findings also indicate their potential inference in the symptomatology of length-dependent peripheral neuropathies and may be a unique target for minimizing symptomatology and pathogenesis in acquired disease. NEW & NOTEWORTHY This study demonstrates nerve excitability differences between the upper and lower limbs during hyperthermia, an experimentally induced axonal stress. The findings indicate that there is differential expression of slow hyperpolarization-activated cyclic nucleotide-gated (HCN) channel isoforms between the upper and lower limbs, which was demonstrated through strong, long hyperpolarizing currents during hyperthermia. Such mechanisms may underlie postural control but render the lower limbs susceptible to dysfunction in disease states.
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Affiliation(s)
- Oliver R Marmoy
- Department of Clinical Neurophysiology, Portsmouth Hospitals NHS Trust, Portsmouth , United Kingdom.,Aston University , Birmingham , United Kingdom
| | | | - Christopher E G Moore
- Department of Clinical Neurophysiology, Portsmouth Hospitals NHS Trust, Portsmouth , United Kingdom
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McDermott LA, Weir GA, Themistocleous AC, Segerdahl AR, Blesneac I, Baskozos G, Clark AJ, Millar V, Peck LJ, Ebner D, Tracey I, Serra J, Bennett DL. Defining the Functional Role of Na V1.7 in Human Nociception. Neuron 2019; 101:905-919.e8. [PMID: 30795902 PMCID: PMC6424805 DOI: 10.1016/j.neuron.2019.01.047] [Citation(s) in RCA: 116] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 12/03/2018] [Accepted: 01/18/2019] [Indexed: 12/17/2022]
Abstract
Loss-of-function mutations in NaV1.7 cause congenital insensitivity to pain (CIP); this voltage-gated sodium channel is therefore a key target for analgesic drug development. Utilizing a multi-modal approach, we investigated how NaV1.7 mutations lead to human pain insensitivity. Skin biopsy and microneurography revealed an absence of C-fiber nociceptors in CIP patients, reflected in a reduced cortical response to capsaicin on fMRI. Epitope tagging of endogenous NaV1.7 revealed the channel to be localized at the soma membrane, axon, axon terminals, and the nodes of Ranvier of induced pluripotent stem cell (iPSC) nociceptors. CIP patient-derived iPSC nociceptors exhibited an inability to properly respond to depolarizing stimuli, demonstrating that NaV1.7 is a key regulator of excitability. Using this iPSC nociceptor platform, we found that some NaV1.7 blockers undergoing clinical trials lack specificity. CIP, therefore, arises due to a profound loss of functional nociceptors, which is more pronounced than that reported in rodent models, or likely achievable following acute pharmacological blockade. VIDEO ABSTRACT.
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Affiliation(s)
- Lucy A McDermott
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK
| | - Greg A Weir
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK
| | | | - Andrew R Segerdahl
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK; Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK
| | - Iulia Blesneac
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK
| | - Georgios Baskozos
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK
| | - Alex J Clark
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK
| | - Val Millar
- Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford OX3 7FZ, UK
| | - Liam J Peck
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK
| | - Daniel Ebner
- Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford OX3 7FZ, UK
| | - Irene Tracey
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK; Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK
| | - Jordi Serra
- Department of Clinical Neurophysiology, King's College Hospital, London SE5 9RS, UK
| | - David L Bennett
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK.
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Gencpinar P, Çelmeli G, Duman Ö, Haspolat Ş, Uysal H. Tibial nerve axonal excitability in type 1 diabetes mellitus. Muscle Nerve 2018; 59:76-81. [DOI: 10.1002/mus.26303] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2017] [Revised: 07/07/2018] [Accepted: 07/10/2018] [Indexed: 11/08/2022]
Affiliation(s)
- Pinar Gencpinar
- Department of Pediatric Neurology; Izmir Katip Celebi University, Tepecik Training and Research Hospital; Izmir Turkey
| | - Gamze Çelmeli
- Department of Pediatric Endocrinology; Akdeniz University Hospital; Antalya Turkey
| | - Özgür Duman
- Department of Pediatric Neurology; Akdeniz University Hospital; Antalya Turkey
| | - Şenay Haspolat
- Department of Pediatric Neurology; Akdeniz University Hospital; Antalya Turkey
| | - Hilmi Uysal
- Department of Neurology; Akdeniz University Hospital; 07070 Konyaaltı Antalya Turkey
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Howells J, Matamala JM, Park SB, Garg N, Vucic S, Bostock H, Burke D, Kiernan MC. In vivo evidence for reduced ion channel expression in motor axons of patients with amyotrophic lateral sclerosis. J Physiol 2018; 596:5379-5396. [PMID: 30175403 DOI: 10.1113/jp276624] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Accepted: 08/31/2018] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS The progressive loss of motor units in amyotrophic lateral sclerosis (ALS) is initially compensated for by the reinnervation of denervated muscle fibres by surviving motor axons. A disruption in protein homeostasis is thought to play a critical role in the pathogenesis of ALS. The changes in surviving motor neurons were studied by comparing the nerve excitability properties of moderately and severely affected single motor axons from patients with ALS with those from single motor axons in control subjects. A mathematical model indicated that approximately 99% of the differences between the ALS and control units could be explained by a non-selective reduction in the expression of all ion channels. These changes in ALS patients are best explained by a failure in the supply of ion channel and other membrane proteins from the diseased motor neuron. ABSTRACT Amyotrophic lateral sclerosis (ALS) is characterised by a progressive loss of motor units and the reinnervation of denervated muscle fibres by surviving motor axons. This reinnervation preserves muscle function until symptom onset, when some 60-80% of motor units have been lost. We have studied the changes in surviving motor neurons by comparing the nerve excitability properties of 31 single motor axons from patients with ALS with those from 21 single motor axons in control subjects. ALS motor axons were classified as coming from moderately or severely affected muscles according to the compound muscle action potential amplitude of the parent muscle. Compared with control units, thresholds were increased, and there was reduced inward and outward rectification and greater superexcitability following a conditioning impulse. These abnormalities were greater in axons from severely affected muscles, and were correlated with loss of fine motor skills. A mathematical model indicated that 99.1% of the differences between the moderately affected ALS and control units could be explained by a reduction in the expression of all ion channels. For the severely affected units, modelling required, in addition, an increase in the current leak through and under the myelin sheath. This might be expected if the anchoring proteins responsible for the paranodal seal were reduced. We conclude that changes in axonal excitability identified in ALS patients are best explained by a failure in the supply of ion channel and other membrane proteins from the diseased motor neuron, a conclusion consistent with recent animal and in vitro human data.
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Affiliation(s)
- James Howells
- Brain & Mind Centre, University of Sydney, Sydney, Australia
| | | | - Susanna B Park
- Brain & Mind Centre, University of Sydney, Sydney, Australia
| | - Nidhi Garg
- Brain & Mind Centre, University of Sydney, Sydney, Australia.,Institute of Clinical Neurosciences, Royal Prince Alfred Hospital and University of Sydney, Sydney, Australia
| | - Steve Vucic
- Departments of Neurology and Neurophysiology, Westmead Hospital and University of Sydney, Sydney, Australia
| | - Hugh Bostock
- MRC Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, Queen Square, London, UK.,Institute of Neurology, UCL, Queen Square, London, WC1N 3BG, UK
| | - David Burke
- Institute of Clinical Neurosciences, Royal Prince Alfred Hospital and University of Sydney, Sydney, Australia
| | - Matthew C Kiernan
- Brain & Mind Centre, University of Sydney, Sydney, Australia.,Institute of Clinical Neurosciences, Royal Prince Alfred Hospital and University of Sydney, Sydney, Australia
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Garg N, Park SB, Howells J, Noto YI, Vucic S, Yiannikas C, Tomlinson SE, Huynh W, Simon NG, Mathey EK, Spies J, Pollard JD, Krishnan AV, Kiernan MC. Anti-MAG neuropathy: Role of IgM antibodies, the paranodal junction and juxtaparanodal potassium channels. Clin Neurophysiol 2018; 129:2162-2169. [PMID: 30144659 DOI: 10.1016/j.clinph.2018.07.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Revised: 06/12/2018] [Accepted: 07/15/2018] [Indexed: 12/14/2022]
Abstract
OBJECTIVE To improve understanding of disease pathophysiology in anti-myelin-associated glycoprotein (anti-MAG) neuropathy to guide further treatment approaches. METHODS Anti-MAG neuropathy patients underwent clinical assessments, nerve conduction and excitability studies, and ultrasound assessment. RESULTS Patients demonstrated a distinctive axonal excitability profile characterised by a reduction in superexcitability [MAG: -14.2 ± 1.6% vs healthy controls (HC): -21.8 ± 1.2%; p < 0.01] without alterations in most other excitability parameters. Mathematical modelling of nerve excitability recordings suggested that changes in axonal function could be explained by a 72.5% increase in juxtaparanodal fast potassium channel activation and an accompanying hyperpolarization of resting membrane potential (by 0.3 mV) resulting in a 94.2% reduction in discrepancy between anti-MAG data and the healthy control model. Superexcitability changes correlated strongly with clinical and neurophysiological parameters. Furthermore, structural assessments demonstrated a proximal pattern of nerve enlargement (C6 nerve root cross-sectional area: 15.9 ± 8.1 mm2 vs HC: 9.1 ± 2.3 mm2; p < 0.05). CONCLUSIONS The imaging and neurophysiological results support the pathogenicity of anti-MAG IgM. Widening between adjacent loops of paranodal myelin due to antibodies would expand the pathway from the node to the juxtaparanode, increasing activation of juxtaparanodal fast potassium channels, thereby impairing saltatory conduction. SIGNIFICANCE Potassium channel blockers may prove beneficial in restoring conduction closer to its normal state and improving nerve function in anti-MAG neuropathy.
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Affiliation(s)
- Nidhi Garg
- Brain and Mind Centre, Sydney Medical School, The University of Sydney, 94 Mallett St, Camperdown, NSW 2050, Australia.
| | - Susanna B Park
- Brain and Mind Centre, Sydney Medical School, The University of Sydney, 94 Mallett St, Camperdown, NSW 2050, Australia.
| | - James Howells
- Brain and Mind Centre, Sydney Medical School, The University of Sydney, 94 Mallett St, Camperdown, NSW 2050, Australia.
| | - Yu-Ichi Noto
- Brain and Mind Centre, Sydney Medical School, The University of Sydney, 94 Mallett St, Camperdown, NSW 2050, Australia.
| | - Steve Vucic
- Departments of Neurology and Neurophysiology, Westmead Hospital, The University of Sydney, NSW, Australia.
| | - Con Yiannikas
- Department of Neurology, Concord and Royal North Shore Hospitals, The University of Sydney, NSW, Australia.
| | - Susan E Tomlinson
- Sydney Medical School, University of Sydney, Sydney, Australia; Department of Neurology, St Vincent's Hospital, Sydney, Australia.
| | - William Huynh
- Brain and Mind Centre, Sydney Medical School, The University of Sydney, 94 Mallett St, Camperdown, NSW 2050, Australia.
| | - Neil G Simon
- St Vincent's Clinical School, University of New South Wales, NSW, Australia.
| | - Emily K Mathey
- Brain and Mind Centre, Sydney Medical School, The University of Sydney, 94 Mallett St, Camperdown, NSW 2050, Australia.
| | - Judith Spies
- Brain and Mind Centre, Sydney Medical School, The University of Sydney, 94 Mallett St, Camperdown, NSW 2050, Australia.
| | - John D Pollard
- Brain and Mind Centre, Sydney Medical School, The University of Sydney, 94 Mallett St, Camperdown, NSW 2050, Australia.
| | - Arun V Krishnan
- Prince of Wales Clinical School, University of New South Wales, NSW, Australia.
| | - Matthew C Kiernan
- Brain and Mind Centre, Sydney Medical School, The University of Sydney, 94 Mallett St, Camperdown, NSW 2050, Australia.
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Makker PGS, Matamala JM, Park SB, Lees JG, Kiernan MC, Burke D, Moalem‐Taylor G, Howells J. A unified model of the excitability of mouse sensory and motor axons. J Peripher Nerv Syst 2018; 23:159-173. [DOI: 10.1111/jns.12278] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2018] [Revised: 06/13/2018] [Accepted: 06/13/2018] [Indexed: 11/29/2022]
Affiliation(s)
- Preet G. S. Makker
- School of Medical SciencesUniversity of New South Wales Sydney Australia
| | | | - Susanna B. Park
- Brain and Mind CentreThe University of Sydney Sydney Australia
| | - Justin G. Lees
- School of Medical SciencesUniversity of New South Wales Sydney Australia
| | - Matthew C. Kiernan
- Brain and Mind CentreThe University of Sydney Sydney Australia
- Royal Prince Alfred HospitalThe University of Sydney Sydney Australia
| | - David Burke
- Royal Prince Alfred HospitalThe University of Sydney Sydney Australia
| | - Gila Moalem‐Taylor
- School of Medical SciencesUniversity of New South Wales Sydney Australia
| | - James Howells
- Brain and Mind CentreThe University of Sydney Sydney Australia
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Foadi N. Modulation of sodium channels as pharmacological tool for pain therapy-highlights and gaps. Naunyn Schmiedebergs Arch Pharmacol 2018; 391:481-488. [PMID: 29572558 DOI: 10.1007/s00210-018-1487-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 03/14/2018] [Indexed: 02/06/2023]
Abstract
Voltage-gated sodium channels are crucially involved in the transduction and transmission of nociceptive signals and pathological pain states. In the past decades, a lot of effort has been spent examining and characterizing biophysical properties of the different sodium channels and their role in signaling pathways. Several gains of function mutations of the sodium channels Nav1.7, Nav1.8, and Nav1.9 are associated with pain disorders. Due to their critical role in nociceptive pathways voltage-gated sodium channels are regarded interesting targets for pharmacological pain treatment. However we still need to fill the gap that exists in the translation of efficacy in preclinical in vitro experiments and in models of pain into the clinic. This review summarizes biological and electrophysiological properties of voltage-gated sodium channels and aims to discuss limitations and promising pharmacological strategies in sodium channel research in the context of pain therapy.
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Affiliation(s)
- Nilufar Foadi
- Clinic for Anaesthesia and Critical Care Medicine, Hannover Medical School, 30625, Hannover, Germany.
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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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Wild BM, Morris R, Moldovan M, Krarup C, Krishnan AV, Arnold R. In Vivo Electrophysiological Measurement of the Rat Ulnar Nerve with Axonal Excitability Testing. J Vis Exp 2018. [PMID: 29443059 DOI: 10.3791/56102] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Electrophysiology enables the objective assessment of peripheral nerve function in vivo. Traditional nerve conduction measures such as amplitude and latency detect chronic axon loss and demyelination, respectively. Axonal excitability techniques "by threshold tracking" expand upon these measures by providing information regarding the activity of ion channels, pumps and exchangers that relate to acute function and may precede degenerative events. As such, the use of axonal excitability in animal models of neurological disorders may provide a useful in vivo measure to assess novel therapeutic interventions. Here we describe an experimental setup for multiple measures of motor axonal excitability techniques in the rat ulnar nerve. The animals are anesthetized with isoflurane and carefully monitored to ensure constant and adequate depth of anesthesia. Body temperature, respiration rate, heart rate and saturation of oxygen in the blood are continuously monitored. Axonal excitability studies are performed using percutaneous stimulation of the ulnar nerve and recording from the hypothenar muscles of the forelimb paw. With correct electrode placement, a clear compound muscle action potential that increases in amplitude with increasing stimulus intensity is recorded. An automated program is then utilized to deliver a series of electrical pulses which generate 5 specific excitability measures in the following sequence: stimulus response behavior, strength duration time constant, threshold electrotonus, current-threshold relationship and the recovery cycle. Data presented here indicate that these measures are repeatable and show similarity between left and right ulnar nerves when assessed on the same day. A limitation of these techniques in this setting is the effect of dose and time under anesthesia. Careful monitoring and recording of these variables should be undertaken for consideration at the time of analysis.
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Affiliation(s)
- Brandon M Wild
- School of Medical Science, University of New South Wales
| | - Renée Morris
- School of Medical Science, University of New South Wales
| | - Mihai Moldovan
- Department of Clinical Neurophysiology, Rigshospitalet and the Institute of Neuroscience and Pharmacology, University of Copenhagen
| | - Christian Krarup
- Department of Clinical Neurophysiology, Rigshospitalet and the Institute of Neuroscience and Pharmacology, University of Copenhagen
| | - Arun V Krishnan
- Prince of Wales Clinical School, University of New South Wales
| | - Ria Arnold
- School of Medical Science, University of New South Wales;
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Stimulus, response and excitability – What is new? Clin Neurophysiol 2018; 129:333-334. [DOI: 10.1016/j.clinph.2017.10.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Accepted: 10/16/2017] [Indexed: 11/23/2022]
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Heide R, Bostock H, Ventzel L, Grafe P, Bergmans J, Fuglsang-Frederiksen A, Finnerup NB, Tankisi H. Axonal excitability changes and acute symptoms of oxaliplatin treatment: In vivo evidence for slowed sodium channel inactivation. Clin Neurophysiol 2017; 129:694-706. [PMID: 29233604 DOI: 10.1016/j.clinph.2017.11.015] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2016] [Revised: 10/16/2017] [Accepted: 11/05/2017] [Indexed: 01/28/2023]
Abstract
OBJECTIVE Neurotoxicity is the most frequent dose-limiting side effect of the anti-cancer agent oxaliplatin, but the mechanisms are not well understood. This study used nerve excitability testing to investigate the pathophysiology of the acute neurotoxicity. METHODS Questionnaires, quantitative sensory tests, nerve conduction studies and nerve excitability testing were undertaken in 12 patients with high-risk colorectal cancer treated with adjuvant oxaliplatin and in 16 sex- and age-matched healthy controls. Examinations were performed twice for patients: once within 3 days after oxaliplatin treatment (post-infusion examination) and once shortly before the following treatment (recovery examination). RESULTS The most frequent post-infusion symptoms were tingling paresthesias and cold allodynia. The most prominent nerve excitability change was decreased superexcitability of motor axons which correlated with the average intensity of abnormal sensations (Spearman Rho = 0.80, p < .01). The motor nerve excitability changes were well modeled by a slowing of sodium channel inactivation, and were proportional to dose/m2 with a half-life of about 10d. CONCLUSIONS Oxaliplatin induces reversible slowing of sodium channel inactivation in motor axons, and these changes are closely related to the reversible cold allodynia. However, further studies are required due to small sample size in this study. SIGNIFICANCE Nerve excitability data provide an index of sodium channel dysfunction: an objective biomarker of acute oxaliplatin neurotoxicity.
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Affiliation(s)
- Rikke Heide
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark; Danish Pain Research Center, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Hugh Bostock
- Institute of Neurology, Queen Square House, London, United Kingdom
| | - Lise Ventzel
- Department of Clinical Oncology, Aarhus University Hospital, Aarhus, Denmark
| | - Peter Grafe
- Institute of Physiology, Ludwig-Maximilians University Munich, Munich, Germany
| | - Joseph Bergmans
- Laboratory of Clinical Neurophysiology, Faculty of Medicine, University of Louvain, Brussels, Belgium
| | | | - Nanna B Finnerup
- Danish Pain Research Center, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark.
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Arnold R, Pianta TJ, Pussell BA, Kirby A, O’Brien K, Sullivan K, Holyday M, Cormack C, Kiernan MC, Krishnan AV. Randomized, Controlled Trial of the Effect of Dietary Potassium Restriction on Nerve Function in CKD. Clin J Am Soc Nephrol 2017; 12:1569-1577. [PMID: 28893921 PMCID: PMC5628705 DOI: 10.2215/cjn.00670117] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 06/26/2017] [Indexed: 11/23/2022]
Abstract
BACKGROUND AND OBJECTIVES Neuromuscular complications are almost universal in CKD by the time that a patient commences dialysis. Recent studies have indicated that chronic hyperkalemia may contribute to the development of neuropathy in CKD. This study was undertaken to determine whether dietary restriction of potassium intake may be a neuroprotective factor in CKD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS A 24-month prospective, single-blind, randomized, controlled trial was undertaken in 47 consecutively recruited patients with stages 3 and 4 CKD. The intervention arm (n=23) was prescribed a diet focusing on potassium restriction to meet a monthly serum potassium level of ≤4.5 mEq/L, with oral sodium polystyrene sulfonate provided if dietary advice failed to achieve the target. The control arm (n=24) received dietary advice regarding general nutrition. The primary outcome was the change in the total neuropathy score evaluated by a blinded observer. Secondary outcomes included electrolyte levels, gait speed, neurophysiologic parameters, and health-related quality of life scores. Five patients withdrew before initiation of treatment, and final analysis consisted of n=21 in each group. RESULTS There was a greater increase in total neuropathy score from baseline to final assessment in the control arm compared with the intervention arm (6.1±6.2-8.6±7.9 controls; 7.8±7.4-8.2±7.5 intervention; change 2.8±3.3-0.4±2.2, respectively; P<0.01). The intervention significantly reduced mean serum potassium compared with controls (4.6±0.1-4.8±0.1 mEq/L mean recorded every 6 months over the trial duration; P=0.03). There were no adverse changes in other nutritional parameters. Improved gait speed was also noted in the intervention arm compared with the control arm, with a mean increase of 0.15±0.17 m/s in the intervention group versus 0.02±0.16 m/s in the control group (P=0.01). CONCLUSIONS Our results provide important preliminary evidence that dietary potassium restriction confers neuroprotection in CKD and should be confirmed in a larger multicenter trial.
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Affiliation(s)
| | - Timothy J. Pianta
- Northern Clinical School, University of Melbourne, Melbourne, Australia
| | - Bruce A. Pussell
- Prince of Wales Clinical School, UNSW Sydney, Sydney, Australia
- Departments of Nephrology and
| | - Adrienne Kirby
- Nutrition and Dietetics, Prince of Wales Hospital, Sydney, Australia; and
| | - Kate O’Brien
- National Health and Medical Research Council Clinical Trials Centre and
| | - Karen Sullivan
- National Health and Medical Research Council Clinical Trials Centre and
| | - Margaret Holyday
- National Health and Medical Research Council Clinical Trials Centre and
| | | | | | - Arun V. Krishnan
- Nutrition and Dietetics, Prince of Wales Hospital, Sydney, Australia; and
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Weerasinghe D, Menon P, Vucic S. Hyperpolarization-activated cyclic-nucleotide-gated channels potentially modulate axonal excitability at different thresholds. J Neurophysiol 2017; 118:3044-3050. [PMID: 28904107 DOI: 10.1152/jn.00576.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 09/06/2017] [Accepted: 09/12/2017] [Indexed: 11/22/2022] Open
Abstract
Hyperpolarization-activated cyclic-nucleotide-gated (HCN) channels mediate differences in sensory and motor axonal excitability at different thresholds in animal models. Importantly, HCN channels are responsible for voltage-gated inward rectifying (Ih) currents activated during hyperpolarization. The Ih currents exert a crucial role in determining the resting membrane potential and have been implicated in a variety of neurological disorders, including neuropathic pain. In humans, differences in biophysical properties of motor and sensory axons at different thresholds remain to be elucidated and could provide crucial pathophysiological insights in peripheral neurological diseases. Consequently, the aim of this study was to characterize sensory and motor axonal function at different threshold. Median nerve motor and sensory axonal excitability studies were undertaken in 15 healthy subjects (45 studies in total). Tracking targets were set to 20, 40, and 60% of maximum for sensory and motor axons. Hyperpolarizing threshold electrotonus (TEh) at 90-100 ms was significantly increased in lower threshold sensory axons times (F = 11.195, P < 0.001). In motor axons, the hyperpolarizing current/threshold (I/V) gradient was significantly increased in lower threshold axons (F = 3.191, P < 0.05). The minimum I/V gradient was increased in lower threshold motor and sensory axons. In conclusion, variation in the kinetics of HCN isoforms could account for the findings in motor and sensory axons. Importantly, assessing the function of HCN channels in sensory and motor axons of different thresholds may provide insights into the pathophysiological processes underlying peripheral neurological diseases in humans, particularly focusing on the role of HCN channels with the potential of identifying novel treatment targets.NEW & NOTEWORTHY Hyperpolarization-activated cyclic-nucleotide-gated (HCN) channels, which underlie inward rectifying currents (Ih), appear to mediate differences in sensory and motor axonal properties. Inward rectifying currents are increased in lower threshold motor and sensory axons, although different HCN channel isoforms appear to underlie these changes. While faster activating HCN channels seem to underlie Ih changes in sensory axons, slower activating HCN isoforms appear to be mediating the differences in Ih conductances in motor axons of different thresholds. The differences in HCN gating properties could explain the predilection for dysfunction of sensory and motor axons in specific neurological diseases.
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Affiliation(s)
| | - Parvathi Menon
- Department of Neurology, Westmead Hospital, Sydney, Australia; and.,Westmead Clinical School, The University of Sydney, Sydney, Australia
| | - Steve Vucic
- Department of Neurology, Westmead Hospital, Sydney, Australia; and .,Westmead Clinical School, The University of Sydney, Sydney, Australia
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Tuncer S, Tuncer Peker T, Burat İ, Kiziltan E, İlhan B, Dalkiliç N. Axonal excitability and conduction alterations caused by levobupivacaine in rat. ACTA PHARMACEUTICA (ZAGREB, CROATIA) 2017; 67:293-307. [PMID: 28858839 DOI: 10.1515/acph-2017-0025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 05/10/2017] [Indexed: 11/15/2022]
Abstract
In this study, effects of the long-acting amide-type local anesthetic levobupivacaine on axonal conduction and excitability parameters of the rat sciatic nerve were thoroughly examined both in vitro and in vivo. In order to deduce its effects on isolated nerve conduction, compound nerve action potential (CNAP) recordings were performed using the suction method over sciatic nerves of Wistar rats before and after administration of 0.05 % (1.7 mmol L-1) levobupivacaine. Levobupivacaine caused complete CNAP area and amplitude depression by blocking conduction in a time-dependent manner. To assess the influence of levobupivacaine on in vivo excitability properties, threshold-tracking (TT) protocols were performed at sciatic nerves of rats injected with perineural 0.05 % (1.7 mmol L-1) levobupivacaine or vehicle alone. Charge-duration TT results revealed that levobupivacaine increases the rheobase and decreases the strength-duration time constant, suggesting interference of the anesthetic with the opening of Na+ channels. Twenty and 40 % threshold electrotonus curves were found for both groups to follow the same paths, suggesting no significant effect of levobupivacaine on K+ channels for either the fastest or relatively slow conducting fibers. Current-threshold relationship results revealed no significant effect on axonal rectifying channels. However, according to the results of the recovery cycle protocol yielding the pattern of excitability changes following the impulse, potential deviation was found in the recovery characteristics of Na+ channels from the absolute refractory period. Consequently, conduction blockage caused by levobupivacaine may not be due to the passive (capacitive) properties of axon or the conductance of potassium channels but to the decrease in sodium channel conductance.
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Affiliation(s)
- Seçkin Tuncer
- N.E. University , Meram Faculty of Medicine, Biophysics Department , Konya , Turkey
| | - Tülay Tuncer Peker
- Ankara University , Faculty of Medicine, Anesthesiology Department , Ankara , Turkey
| | - İlksen Burat
- N.E. University , Meram Faculty of Medicine, Biophysics Department , Konya , Turkey
| | - Erhan Kiziltan
- Başkent University , Faculty of Medicine, Physiology Department , Ankara , Turkey
| | - Barkin İlhan
- N.E. University , Meram Faculty of Medicine, Biophysics Department , Konya , Turkey
| | - Nizamettin Dalkiliç
- N.E. University , Meram Faculty of Medicine, Biophysics Department , Konya , Turkey
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Zhang Y, Bucher D, Nadim F. Ionic mechanisms underlying history-dependence of conduction delay in an unmyelinated axon. eLife 2017; 6. [PMID: 28691900 PMCID: PMC5519330 DOI: 10.7554/elife.25382] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 07/06/2017] [Indexed: 11/13/2022] Open
Abstract
Axonal conduction velocity can change substantially during ongoing activity, thus modifying spike interval structures and, potentially, temporal coding. We used a biophysical model to unmask mechanisms underlying the history-dependence of conduction. The model replicates activity in the unmyelinated axon of the crustacean stomatogastric pyloric dilator neuron. At the timescale of a single burst, conduction delay has a non-monotonic relationship with instantaneous frequency, which depends on the gating rates of the fast voltage-gated Na+ current. At the slower timescale of minutes, the mean value and variability of conduction delay increase. These effects are because of hyperpolarization of the baseline membrane potential by the Na+/K+ pump, balanced by an h-current, both of which affect the gating of the Na+ current. We explore the mechanisms of history-dependence of conduction delay in axons and develop an empirical equation that accurately predicts this history-dependence, both in the model and in experimental measurements.
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Affiliation(s)
- Yang Zhang
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, United States
| | - Dirk Bucher
- Federated Department of Biological Sciences, NJIT and Rutgers University, Newark, United States
| | - Farzan Nadim
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, United States.,Federated Department of Biological Sciences, NJIT and Rutgers University, Newark, United States
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Klein CS, Zhao CN, Liu H, Zhou P. Differences in excitability properties between medial gastrocnemius, tibialis anterior, and abductor pollicis brevis motor axons. Muscle Nerve 2017. [PMID: 28621464 DOI: 10.1002/mus.25722] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
INTRODUCTION Excitability properties of motor nerves to different muscles are different, but the explanation is uncertain. We characterized motor axon excitability properties to the medial gastrocnemius (MG) in 27 adults, and made comparisons with the peroneal nerve to the tibialis anterior (TA) and median nerve to the abductor pollicis brevis (APB) in 10 subjects. METHODS Recordings of multiple excitability properties were made using threshold tracking, stimulating the nerves at the wrist or knee. RESULTS Threshold electrotonus and superexcitability differed between nerves (APB>MG>TA axons) that may reflect differences in fast K+ conductance. APB axons had larger S2 accommodation and undershoot than TA and MG axons, indicating greater slow K+ conductance. TA axons demonstrated greater accommodation during hyperpolarizing currents than MG and APB axons, suggestive of greater inwardly rectifying current. DISCUSSION Inherent differences in several conductances underlie nerve differences in excitability, presumably related to muscle or motoneuron properties. Muscle Nerve 57: E60-E69, 2018.
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Affiliation(s)
- Cliff S Klein
- Guangdong Work Injury Rehabilitation Center, 68 Qide Road, Baiyun District, Guangzhou, China, 510440
| | - Chen Ning Zhao
- Guangdong Work Injury Rehabilitation Center, 68 Qide Road, Baiyun District, Guangzhou, China, 510440
| | - Hui Liu
- Guangdong Work Injury Rehabilitation Center, 68 Qide Road, Baiyun District, Guangzhou, China, 510440
| | - Ping Zhou
- Guangdong Work Injury Rehabilitation Center, 68 Qide Road, Baiyun District, Guangzhou, China, 510440.,Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center at Houston, Houston, Texas, USA, 77030
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Tomlinson SE, Howells J, Burke D. In vivo assessment of neurological channelopathies: Application of peripheral nerve excitability studies. Neuropharmacology 2017; 132:98-107. [PMID: 28476643 DOI: 10.1016/j.neuropharm.2017.04.045] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 04/19/2017] [Accepted: 04/29/2017] [Indexed: 12/14/2022]
Abstract
With the rapid evolution of understanding of neurological channelopathies comes a need for sensitive tools to evaluate patients in clinical practice. Neurological channelopathies with a single-gene basis can manifest as seizures, headache, ataxia, vertigo, confusion, weakness and neuropathic pain and it is likely that other genetic factors contribute to the phenotype of many of these disorders. Ion channel dysfunction can result in abnormal cell membrane excitability but utilisation of advanced neurophysiology techniques has lagged behind developments in clinical, genetic and imaging evaluation of channelopathies. However, momentum in the application of in vivo axonal excitability testing sees these tests emerging as valuable tools, with the capacity to provide sensitive and specific insights into the mechanism of disease. While single-channel function cannot be directly measured in vivo, evaluation of subjects with single-gene channelopathies has provided insights into the effects of mutation-related alterations of membrane excitability, as well as compensatory adaptive changes. By showing how ion channel dysfunction can affect axonal excitability in vivo, studies of the excitability of peripheral nerve axons complement in vitro analysis of single channel activity. The interpretation of results is enhanced by mathematical modelling of axonal function and insights provided by in vitro work. This article is part of the Special Issue entitled 'Channelopathies.'
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Affiliation(s)
- Susan E Tomlinson
- Sydney Medical School, University of Sydney, Sydney, Australia; Department of Neurology, St Vincent's Hospital, Sydney, Australia.
| | - James Howells
- Brain and Mind Centre, University of Sydney, Sydney, Australia
| | - David Burke
- Sydney Medical School, University of Sydney, Sydney, Australia; Department of Neurology, Royal Prince Alfred Hospital, Sydney, Australia
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Eviston TJ, Chong LSH, Kwai NCG, Clark JR, Krishnan AV. Altered axonal excitability properties in facial palsy. Muscle Nerve 2017; 57:268-272. [PMID: 28457007 DOI: 10.1002/mus.25677] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/24/2017] [Indexed: 11/12/2022]
Abstract
INTRODUCTION Axonal excitability measures give insight into the biophysical properties of peripheral nerve axons. In this study we applied these techniques to the study of facial palsy. METHODS Thirty patients with established facial palsy due to unresolved Bell's palsy or herpes zoster (>6 months duration), tumor invasion of the facial nerve, or traumatic facial nerve injury were assessed using facial nerve excitability techniques. RESULTS Full recordings were obtained in 23 patients (15 unrecovered Bell's palsy or herpes zoster, 5 trauma, 3 tumor-related). Compared with normal controls, the facial palsy group demonstrated changes in stimulus response properties, threshold electrotonus, refractoriness, superexcitability, and I/V slope. Depolarizing threshold electrotonus distinguished between viral and non-viral etiologies on subgroup analysis. DISCUSSION In this cross-sectional study, established facial palsy demonstrated findings similar to those seen in studies of regenerated axons. The improved understanding of underlying axonal characteristics offered by the technique may guide future treatment. Muscle Nerve 57: 268-272, 2018.
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Affiliation(s)
- Timothy J Eviston
- Prince of Wales Clinical School, University of New South Wales, Randwick, New South Wales, 2031, Australia
| | - Lauren S H Chong
- Prince of Wales Clinical School, University of New South Wales, Randwick, New South Wales, 2031, Australia
| | - Natalie C G Kwai
- Prince of Wales Clinical School, University of New South Wales, Randwick, New South Wales, 2031, Australia
| | | | - Arun V Krishnan
- Prince of Wales Clinical School, University of New South Wales, Randwick, New South Wales, 2031, Australia
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Abstract
To gain insights into erythromelalgia disease pathophysiology, this study elucidated changes in peripheral axonal excitability and influences of temperature and mexiletine on axonal function. Erythromelalgia (EM) is a rare neurovascular disorder characterized by intermittent severe burning pain, erythema, and warmth in the extremities on heat stimuli. To investigate the underlying pathophysiology, peripheral axonal excitability studies were performed and changes with heating and therapy explored. Multiple excitability indices (stimulus–response curve, strength–duration time constant (SDTC), threshold electrotonus, and recovery cycle) were investigated in 23 (9 EMSCN9A+ and 14 EMSCN9A−) genetically characterized patients with EM stimulating median motor and sensory axons at the wrist. At rest, patients with EM showed a higher threshold and rheobase (P < 0.001) compared with controls. Threshold electrotonus and current–voltage relationships demonstrated greater changes of thresholds in both depolarizing and hyperpolarizing preconditioning electrotonus in both EM cohorts compared with controls in sensory axons (P < 0.005). When average temperature was raised from 31.5°C to 36.3°C in EMSCN9A+ patients, excitability changes showed depolarization, specifically SDTC significantly increased, in contrast to the effects of temperature previously established in healthy subjects (P < 0.05). With treatment, 4 EMSCN9A+ patients (4/9) reported improvement with mexiletine, associated with reduction in SDTC in motor and sensory axons. This is the first study of primary EM using threshold tracking techniques to demonstrate alterations in peripheral axonal membrane function. Taken together, these changes may be attributed to systemic neurovascular abnormalities in EM, with chronic postischaemic resting membrane potential hyperpolarization due to Na+/K+ pump overactivity. With heating, a trigger of acute symptoms, axonal depolarization developed, corresponding to acute axonal ischaemia. This study has provided novel insights into EM pathophysiology.
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