1
|
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.
Collapse
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
| |
Collapse
|
2
|
Multisite silicon probes enable simultaneous recording of spontaneous and evoked activity in multiple isolated C-fibres in rat saphenous nerve. J Neurosci Methods 2021; 368:109419. [PMID: 34800543 DOI: 10.1016/j.jneumeth.2021.109419] [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: 06/28/2021] [Revised: 10/21/2021] [Accepted: 11/11/2021] [Indexed: 11/21/2022]
Abstract
BACKGROUND Recordings of electrical activity in nerves have provided valuable insights into normal function and pathological behaviours of the nervous system. Current high-resolution techniques (e.g. teased fibre recordings) typically utilise electrodes with a single recording site, capturing the activity of a single isolated neuron per recording. NEW METHOD We conducted proof-of-principle C-fibre recordings in the saphenous nerve of urethane-anaesthetised adult Wistar rats using 32-channel multisite silicon electrodes. Data was acquired using the OpenEphys recording system and clustered offline with Kilosort 2.5. RESULTS In single recordings in 5 rats, 32 units with conduction velocities in the C-fibre range (< 1 m/s) were identified via constant latency responses and classified using activity dependent slowing. In two animals, 6 C-fibres (5 classified as nociceptors) were well isolated after clustering. Their activity could be tracked throughout the recording - including during periods of spontaneous activity. Axonal conduction velocities were calculated from spontaneous activity and/or low frequency electrical stimulation using only the differences in action potential latency as it propagated past multiple probe sites. COMPARISON WITH EXISTING METHODS Single electrode approaches have a low data yield and generating group data for specific fibre types is challenging as it requires multiple experimental subjects and recording sessions. This is particularly true when the experimental targets are the small, unmyelinated C-fibres carrying nociceptive information. CONCLUSIONS We demonstrate that multisite recordings can greatly increase experimental yields and enhance fibre identification. The approach is of particular utility when coupled with clustering analysis. Multisite probes and analysis approaches constitute a valuable new toolbox for researchers studying the peripheral nervous system.
Collapse
|
3
|
Werland F, Hirth M, Rukwied R, Ringkamp M, Turnquist B, Jorum E, Namer B, Schmelz M, Obreja O. Maximum axonal following frequency separates classes of cutaneous unmyelinated nociceptors in the pig. J Physiol 2021; 599:1595-1610. [DOI: 10.1113/jp280269] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 12/17/2020] [Indexed: 11/08/2022] Open
Affiliation(s)
- Fiona Werland
- Department of Experimental Pain Research, MCTN Medical Faculty Mannheim Heidelberg University Mannheim Germany
| | - Michael Hirth
- Department of Experimental Pain Research, MCTN Medical Faculty Mannheim Heidelberg University Mannheim Germany
| | - Roman Rukwied
- Department of Experimental Pain Research, MCTN Medical Faculty Mannheim Heidelberg University Mannheim Germany
| | - Matthias Ringkamp
- Department of Neurosurgery Johns Hopkins University Baltimore MD USA
| | - Brian Turnquist
- Faculty of Mathematics and Computer Science Bethel University MN USA
| | - Ellen Jorum
- Section of Clinical Neurophysiology, Department of Neurology Oslo University Hospital Oslo Norway
- Institute of Clinical Medicine University of Oslo Oslo Norway
| | - Barbara Namer
- IZKF Neuroscience Research Group, University Hospital RWTH Aachen and Department of Physiology and Pathophysiology University of Erlangen‐Nuremberg Erlangen Germany
| | - Martin Schmelz
- Department of Experimental Pain Research, MCTN Medical Faculty Mannheim Heidelberg University Mannheim Germany
| | - Otilia Obreja
- Department of Experimental Pain Research, MCTN Medical Faculty Mannheim Heidelberg University Mannheim Germany
| |
Collapse
|
4
|
Pelot NA, Grill WM. In vivo quantification of excitation and kilohertz frequency block of the rat vagus nerve. J Neural Eng 2020; 17:026005. [PMID: 31945746 DOI: 10.1088/1741-2552/ab6cb6] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
OBJECTIVE There is growing interest in treating diseases by electrical stimulation and block of peripheral autonomic nerves, but a paucity of studies on the excitation and block of small-diameter autonomic axons. We conducted in vivo quantification of the strength-duration properties, activity-dependent slowing (ADS), and responses to kilohertz frequency (KHF) signals for the rat vagus nerve (VN). APPROACH We conducted acute in vivo experiments in urethane-anaesthetized rats. We placed two cuff electrodes on the left cervical VN and one cuff electrode on the anterior subdiaphragmatic VN. The rostral cervical cuff was used to deliver pulses to quantify recruitment and ADS. The caudal cervical cuff was used to deliver KHF signals. The subdiaphragmatic cuff was used to record compound action potentials (CAPs). MAIN RESULTS We quantified the input-output recruitment and strength-duration curves. Fits to the data using standard strength-duration equations were qualitatively similar, but the resulting chronaxie and rheobase estimates varied substantially. We measured larger thresholds for the slowest fibres (0.5-1 m s-1), especially at shorter pulse widths. Using a novel cross-correlation CAP-based analysis, we measured ADS of ~2.3% after 3 min of 2 Hz stimulation, which is comparable to the ADS reported for sympathetic efferents in somatic nerves, but much smaller than the ADS in cutaneous nociceptors. We found greater ADS with higher stimulation frequency and non-monotonic changes in CV in select cases. We found monotonically increasing block thresholds across frequencies from 10 to 80 kHz for both fast and slow fibres. Further, following 25 s of KHF signal, neural conduction could require tens of seconds to recover. SIGNIFICANCE The quantification of mammalian autonomic nerve responses to conventional and KHF signals provides essential information for the development of peripheral nerve stimulation therapies and for understanding their mechanisms of action.
Collapse
Affiliation(s)
- N A Pelot
- Department of Biomedical Engineering, Duke University, Room 1427, Fitzpatrick CIEMAS, 101 Science Drive, Campus Box 90281, Durham, NC 27708, United States of America
| | | |
Collapse
|
5
|
Evdokimov D, Frank J, Klitsch A, Unterecker S, Warrings B, Serra J, Papagianni A, Saffer N, Meyer zu Altenschildesche C, Kampik D, Malik RA, Sommer C, Üçeyler N. Reduction of skin innervation is associated with a severe fibromyalgia phenotype. Ann Neurol 2019; 86:504-516. [DOI: 10.1002/ana.25565] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 07/14/2019] [Accepted: 07/28/2019] [Indexed: 02/05/2023]
Affiliation(s)
| | - Johanna Frank
- Department of NeurologyUniversity of Würzburg Germany
| | | | - Stefan Unterecker
- Department of Psychiatry, Psychosomatics, and PsychotherapyUniversity of Würzburg Germany
| | - Bodo Warrings
- Department of Psychiatry, Psychosomatics, and PsychotherapyUniversity of Würzburg Germany
| | | | | | - Nadine Saffer
- Department of NeurologyUniversity of Würzburg Germany
| | | | - Daniel Kampik
- Department of OphthalmologyUniversity of Würzburg Germany
| | - Rayaz A. Malik
- Weill Cornell Medicine‐Qatar, Qatar Foundation Education City Doha Qatar
| | | | | |
Collapse
|
6
|
Ren X, Roessler AE, Lynch TL, Haar L, Mallick F, Lui Y, Tranter M, Ren MH, Xie WR, Fan GC, Zhang JM, Kranias EG, Anjak A, Koch S, Jiang M, Miao Q, Wang Y, Cohen A, Rubinstein J, Weintraub NL, Jones WK. Cardioprotection via the skin: nociceptor-induced conditioning against cardiac MI in the NIC of time. Am J Physiol Heart Circ Physiol 2018; 316:H543-H553. [PMID: 30575436 DOI: 10.1152/ajpheart.00094.2018] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Timely reperfusion is still the most effective approach to limit infarct size in humans. Yet, despite advances in care and reduction in door-to-balloon times, nearly 25% of patients develop heart failure postmyocardial infarction, with its attendant morbidity and mortality. We previously showed that cardioprotection results from a skin incision through the umbilicus in a murine model of myocardial infarction. In the present study, we show that an electrical stimulus or topical capsaicin applied to the skin in the same region induces significantly reduced infarct size in a murine model. We define this class of phenomena as nociceptor-induced conditioning (NIC) based on the peripheral nerve mechanism of initiation. We show that NIC is effective both as a preconditioning and postconditioning remote stimulus, reducing infarct size by 86% and 80%, respectively. NIC is induced via activation of skin C-fiber nerves. Interestingly, the skin region that activates NIC is limited to the anterior of the T9-T10 vertebral region of the abdomen. Cardioprotection after NIC requires the integrity of the spinal cord from the region of stimulation to the thoracic vertebral region of the origin of the cardiac nerves but does not require that the cord be intact in the cervical region. Thus, we show that NIC is a reflex and not a central nervous system-mediated effect. The mechanism involves bradykinin 2 receptor activity and activation of PKC, specifically, PKC-α. The similarity of the neuroanatomy and conservation of the effectors of cardioprotection supports that NIC may be translatable to humans as a nontraumatic and practical adjunct therapy against ischemic disease. NEW & NOTEWORTHY This study shows that an electrical stimulus to skin sensory nerves elicits a very powerful cardioprotection against myocardial infarction. This stimulus works by a neurogenic mechanism similar to that previously elucidated for remote cardioprotection of trauma. Nociceptor-induced conditioning is equally potent when applied before ischemia or at reperfusion and has great potential clinically.
Collapse
Affiliation(s)
- Xiaoping Ren
- Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago, Mawood, Illinois
| | - Anne E Roessler
- Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago, Mawood, Illinois
| | - Thomas L Lynch
- Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago, Mawood, Illinois
| | - Lauren Haar
- Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago, Mawood, Illinois
| | - Faryal Mallick
- Division of Cardiology, Department of Medicine, University of Cincinnati College of Medicine , Cincinnati, Ohio
| | - Yong Lui
- Division of Cardiology, Department of Medicine, University of Cincinnati College of Medicine , Cincinnati, Ohio
| | - Michael Tranter
- Division of Cardiology, Department of Medicine, University of Cincinnati College of Medicine , Cincinnati, Ohio
| | - Michelle Huan Ren
- Division of Cardiology, Department of Medicine, University of Cincinnati College of Medicine , Cincinnati, Ohio
| | - Wen Rui Xie
- Department of Anesthesiology and Department of Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio
| | - Guo-Chang Fan
- Department of Pharmacology, University of Cincinnati , Cincinnati, Ohio
| | - Jun-Ming Zhang
- Department of Anesthesiology and Department of Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio
| | | | - Ahmad Anjak
- Division of Cardiology, Department of Medicine, University of Cincinnati College of Medicine , Cincinnati, Ohio
| | - Sheryl Koch
- Division of Cardiology, Department of Medicine, University of Cincinnati College of Medicine , Cincinnati, Ohio
| | - Min Jiang
- Division of Cardiology, Department of Medicine, University of Cincinnati College of Medicine , Cincinnati, Ohio
| | - Qing Miao
- Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago, Mawood, Illinois
| | - Yang Wang
- Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago, Mawood, Illinois
| | - Albert Cohen
- Department of Mathematics, Michigan State University , East Lansing, Michigan
| | - Jack Rubinstein
- Division of Cardiology, Department of Medicine, University of Cincinnati College of Medicine , Cincinnati, Ohio
| | - Neal L Weintraub
- Division of Cardiology, Georgia Regents University, Augusta, Geogia
| | - W Keith Jones
- Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago, Mawood, Illinois
| |
Collapse
|
7
|
Autophosphorylated CaMKII Facilitates Spike Propagation in Rat Optic Nerve. J Neurosci 2018; 38:8087-8105. [PMID: 30076212 DOI: 10.1523/jneurosci.0078-18.2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 07/14/2018] [Accepted: 08/01/2018] [Indexed: 11/21/2022] Open
Abstract
Repeated spike firing can transmit information at synapses and modulate spike timing, shape, and conduction velocity. These latter effects have been found to result from voltage-induced changes in ion currents and could alter the signals carried by axons. Here, we test whether Ca2+/calmodulin-dependent protein kinase II (CaMKII) regulates spike propagation in adult rat optic nerve. We find that small-, medium-, and large-diameter axons bind anti-Thr286-phosphorylated CaMKII (pT286) antibodies and that, in isolated optic nerves, electrical stimulation reduces pT286 levels, spike propagation is hastened by CaMKII autophosphorylation and slowed by CaMKII dephosphorylation, single and multiple spikes slow propagation of subsequently activated spikes, and more frequent stimulation produces greater slowing. Likewise, exposing freely moving animals to flickering illumination reduces pT286 levels in optic nerves and electrically eliciting spikes in vivo in either the optic nerve or optic chiasm slows subsequent spike propagation in the optic nerve. By increasing the time that elapses between successive spikes as they propagate, pT286 dephosphorylation and activity-induced spike slowing reduce the frequency of propagated spikes below the frequency at which they were elicited and would thus limit the frequency at which axons synaptically drive target neurons. Consistent with this, the ability of retinal ganglion cells to drive at least some lateral geniculate neurons has been found to increase when presented with light flashes at low and moderate temporal frequencies but less so at high frequencies. Activity-induced decreases in spike frequency may also reduce the energy required to maintain normal intracellular Na+ and Ca2+ levels.SIGNIFICANCE STATEMENT By propagating along axons at constant velocities, spikes could drive synapses as frequently as they are initiated. However, the onset of spiking has been found to alter the conduction velocity of subsequent ("follower") spikes in various preparations. Here, we find that spikes reduce spike frequency in rat optic nerve by slowing follower spike propagation and that electrically stimulated spiking ex vivo and spike-generating flickering illumination in vivo produce net decreases in axonal Ca2+/calmodulin-dependent protein kinase II (CaMKII) autophosphorylation. Consistent with these effects, propagation speed increases and decreases, respectively, with CaMKII autophosphorylation and dephosphorylation. Lowering spike frequency by CaMKII dephosphorylation is a novel consequence of axonal spiking and light adaptation that could decrease synaptic gain as stimulus frequency increases and may also reduce energy use.
Collapse
|
8
|
Djouhri L, Smith T, Ahmeda A, Alotaibi M, Weng X. Hyperpolarization-activated cyclic nucleotide-gated channels contribute to spontaneous activity in L4 C-fiber nociceptors, but not Aβ-non-nociceptors, after axotomy of L5-spinal nerve in the rat in vivo. Pain 2018; 159:1392-1402. [PMID: 29578948 DOI: 10.1097/j.pain.0000000000001224] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Peripheral neuropathic pain associated with partial nerve injury is believed to be driven partly by aberrant spontaneous activity (SA) in both injured and uninjured dorsal root ganglion (DRG) neurons. The underlying ionic mechanisms are not fully understood, but hyperpolarization-activated cyclic nucleotide-gated (HCN) channels which underlie the excitatory Ih current have been implicated in SA generation in axotomized A-fiber neurons after L5-spinal nerve ligation/axotomy (SNL/SNA). Here, using a modified model of SNA (mSNA) which involves, in addition to L5-SNA, loose ligation of the L4-spinal nerve with neuroinflammation-inducing chromic gut, we examined whether HCN channels also contribute to SA in the adjacent L4-neurons. Intracellular recordings from L4-DRG neurons in control rats, and L4-DRG neurons in mSNA rats were made using in vivo voltage- and current-clamp techniques. Compared with control, L4 C-nociceptors and Aβ-low-threshold mechanoreceptors (LTMs) exhibited SA 7 days after mSNA. This was accompanied, in C-nociceptors, by a significant increase in Ih amplitude, the percentage of Ih-expressing neurons, and Ih activation rate. Hyperpolarization-activated cyclic nucleotide-gated channel blockade with ZD7288 (10 mg/kg, intravenously) suppressed SA in C-nociceptors, but not Aβ-LTMs, and caused in C-nociceptors, membrane hyperpolarization and a decrease in Ih activation rate. Furthermore, intraplantar injection of ZD7288 (100 μM) was found to be as effective as gabapentin (positive control) in attenuating cold hypersensitivity in mSNA rats. These findings suggest that HCN channels contribute to nerve injury-induced SA in L4 C-nociceptors, but not Aβ-LTMs, and that ZD7288 exerts its analgesic effects by altering Ih activation properties and/or causing membrane hyperpolarization in L4 C-nociceptors.
Collapse
Affiliation(s)
- Laiche Djouhri
- Department of Physiology, College of Medicine, Alfaisal University, Riyadh, Saudi Arabia
- Department of Clinical and Molecular Pharmacology, Institute of Translational Medicine, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Trevor Smith
- Wolfson CARD, Neurorestoration Group, King's College London, London, United Kingdom
| | - Ahmad Ahmeda
- Department of Physiology, College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - Mohammad Alotaibi
- Department of Physiology, College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - Xiechuan Weng
- State Key Laboratory of Proteomics, Department of Neurobiology, Beijing Institute of Basic Medical Sciences, Beijing, China
| |
Collapse
|
9
|
Garcia-Perez E, Schönberger T, Sumalla M, Stierstorfer B, Solà R, Doods H, Serra J, Gorodetskaya N. Behavioural, morphological and electrophysiological assessment of the effects of type 2 diabetes mellitus on large and small nerve fibres in Zucker diabetic fatty, Zucker lean and Wistar rats. Eur J Pain 2018; 22:1457-1472. [DOI: 10.1002/ejp.1235] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/11/2018] [Indexed: 01/09/2023]
Affiliation(s)
| | - T. Schönberger
- Boehringer Ingelheim Pharma GmbH & Co. KG; Biberach an der Riss Germany
| | - M. Sumalla
- Neuroscience Technologies; Barcelona Spain
| | - B. Stierstorfer
- Boehringer Ingelheim Pharma GmbH & Co. KG; Biberach an der Riss Germany
| | - R. Solà
- Neuroscience Technologies; Barcelona Spain
| | - H. Doods
- Boehringer Ingelheim Pharma GmbH & Co. KG; Biberach an der Riss Germany
| | - J. Serra
- Neuroscience Technologies; Barcelona Spain
| | - N. Gorodetskaya
- Boehringer Ingelheim Pharma GmbH & Co. KG; Biberach an der Riss Germany
| |
Collapse
|
10
|
|
11
|
Watkins RH, Wessberg J, Backlund Wasling H, Dunham JP, Olausson H, Johnson RD, Ackerley R. Optimal delineation of single C-tactile and C-nociceptive afferents in humans by latency slowing. J Neurophysiol 2017; 117:1608-1614. [PMID: 28123010 PMCID: PMC5376601 DOI: 10.1152/jn.00939.2016] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 01/23/2017] [Accepted: 01/23/2017] [Indexed: 11/24/2022] Open
Abstract
Human skin encodes a plethora of touch interactions, and affective tactile information is primarily signaled by slowly conducting C-mechanoreceptive afferents. We show that electrical stimulation of low-threshold C-tactile afferents produces markedly different patterns of activity compared with high-threshold C-mechanoreceptive nociceptors, although the populations overlap in their responses to mechanical stimulation. This fundamental distinction demonstrates a divergence in affective touch signaling from the first stage of sensory processing, having implications for the processing of interpersonal touch. C-mechanoreceptors in humans comprise a population of unmyelinated afferents exhibiting a wide range of mechanical sensitivities. C-mechanoreceptors are putatively divided into those signaling gentle touch (C-tactile afferents, CTs) and nociception (C-mechanosensitive nociceptors, CMs), giving rise to positive and negative affect, respectively. We sought to distinguish, compare, and contrast the properties of a population of human C-mechanoreceptors to see how fundamental the divisions between these putative subpopulations are. We used microneurography to record from individual afferents in humans and applied electrical and mechanical stimulation to their receptive fields. We show that C-mechanoreceptors can be distinguished unequivocally into two putative populations, comprising CTs and CMs, by electrically evoked spike latency changes (slowing). After both natural mechanical stimulation and repetitive electrical stimulation there was markedly less latency slowing in CTs compared with CMs. Electrical receptive field stimulation, which bypasses the receptor end organ, was most effective in classifying C-mechanoreceptors, as responses to mechanical receptive field stimulation overlapped somewhat, which may lead to misclassification. Furthermore, we report a subclass of low-threshold CM responding to gentle mechanical stimulation and a potential subclass of CT afferent displaying burst firing. We show that substantial differences exist in the mechanisms governing axonal conduction between CTs and CMs. We provide clear electrophysiological “signatures” (extent of latency slowing) that can be used in unequivocally identifying populations of C-mechanoreceptors in single-unit and multiunit microneurography studies and in translational animal research into affective touch. Additionally, these differential mechanisms may be pharmacologically targetable for separate modulation of positive and negative affective touch information. NEW & NOTEWORTHY Human skin encodes a plethora of touch interactions, and affective tactile information is primarily signaled by slowly conducting C-mechanoreceptive afferents. We show that electrical stimulation of low-threshold C-tactile afferents produces markedly different patterns of activity compared with high-threshold C-mechanoreceptive nociceptors, although the populations overlap in their responses to mechanical stimulation. This fundamental distinction demonstrates a divergence in affective touch signaling from the first stage of sensory processing, having implications for the processing of interpersonal touch.
Collapse
Affiliation(s)
- Roger H Watkins
- Department of Physiology, University of Gothenburg, Gothenburg, Sweden; .,School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
| | - Johan Wessberg
- Department of Physiology, University of Gothenburg, Gothenburg, Sweden
| | | | - James P Dunham
- University Division of Anaesthesia, Cambridge University Hospitals, NHS Foundation Trust, Cambridge, United Kingdom
| | - Håkan Olausson
- Department of Physiology, University of Gothenburg, Gothenburg, Sweden.,Center for Social and Affective Neuroscience, Department of Clinical and Experimental Medicine, Linkoping University, Linkoping, Sweden; and
| | - Richard D Johnson
- Department of Physiology, University of Gothenburg, Gothenburg, Sweden.,Department of Physiological Sciences, University of Florida, Gainesville, Florida
| | - Rochelle Ackerley
- Department of Physiology, University of Gothenburg, Gothenburg, Sweden.,Laboratoire de Neurosciences Intégratives et Adaptatives (UMR 7260), Aix-Marseille Université-CNRS, Marseille, France
| |
Collapse
|
12
|
Reduced excitability and impaired nociception in peripheral unmyelinated fibers from Nav1.9-null mice. Pain 2016; 158:58-67. [DOI: 10.1097/j.pain.0000000000000723] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
|
13
|
Hoffmann T, Kistner K, Nassar M, Reeh PW, Weidner C. Use dependence of peripheral nociceptive conduction in the absence of tetrodotoxin-resistant sodium channel subtypes. J Physiol 2016; 594:5529-41. [PMID: 27105013 DOI: 10.1113/jp272082] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 04/11/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS This study examines conduction in peripheral nerves and its use dependence in tetrodotoxin-resistant (TTXr) sodium channel (Nav 1.8, Nav 1.9) knockout and wildtype animals. We observed use-dependent decreases of single fibre and compound action potential amplitude in peripheral mouse C-fibres (wildtype). This matches the previously published hypothesis that increased Na/K-pump activity is not the underlying mechanism for use-dependent changes of neural conduction. Knocking out TTXr sodium channels influences use-dependent changes of conductive properties (action potential amplitude, latency, conduction safety) in the order Nav 1.8 KO > Nav 1.9KO > wildtype. This is most likely explained by different subsets of presumably (relatively) Nav 1.7-rich conducting fibres in knockout animals as compared to wildtypes, in combination with reduced per-pulse sodium influx. ABSTRACT Use dependency of peripheral nerves, especially of nociceptors, correlates with receptive properties. Slow inactivation of voltage-gated sodium channels has been discussed to be the underlying mechanism - pointing to a receptive class-related difference of sodium channel equipment. Using electrophysiological recordings of single unmyelinated cutaneous fibres and their compound action potential (AP), we evaluated use-dependent changes in mouse peripheral nerves, and the contribution of the tetrodotoxin-resistant (TTXr) sodium channels Nav 1.8 and Nav 1.9 to these changes. Nerve fibres were electrically stimulated using single or double pulses at 2 Hz. Use-dependent changes of latency, AP amplitude, and duration as well as the fibres' ability to follow the stimulus were evaluated. AP amplitudes substantially diminished in used fibres from C57BL/6 but increased in Nav 1.8 knockout (KO) mice, with Nav 1.9 KO in between. Activity-induced latency slowing was in contrast the most pronounced in Nav 1.8 KOs and the least in wildtype mice. The genotype was also predictive of how long fibres could follow the double pulsed stimulus with wildtype fibres blocking first and Nav 1.8 KO fibres enduring the longest. In contrast, changes in spike duration were less pronounced and displayed no significant tendency. Thus, all major measures of peripheral nerve accommodation (amplitude, latency and durability) depended on genotype. All use-dependent changes appeared in the order NaV 1.8 KO > NaV 1.9 KO > wildtype, which is most likely explained by the relative contribution of Nav 1.7 varying in the same order and the amounts of per-pulse sodium influx expected in the opposite order.
Collapse
Affiliation(s)
- Tal Hoffmann
- Institute for Physiology and Pathophysiology, University of Erlangen-Nuremberg, Erlangen, Germany.
| | - Katrin Kistner
- Institute for Physiology and Pathophysiology, University of Erlangen-Nuremberg, Erlangen, Germany
| | | | - Peter W Reeh
- Institute for Physiology and Pathophysiology, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Christian Weidner
- Institute for Physiology and Pathophysiology, University of Erlangen-Nuremberg, Erlangen, Germany
| |
Collapse
|
14
|
Specific changes in conduction velocity recovery cycles of single nociceptors in a patient with erythromelalgia with the I848T gain-of-function mutation of Nav1.7. Pain 2016; 156:1637-1646. [PMID: 25993546 DOI: 10.1097/j.pain.0000000000000229] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Seven patients diagnosed with erythromelalgia (EM) were investigated by microneurography to record from unmyelinated nerve fibers in the peroneal nerve. Two patients had characterized variants of sodium channel Nav1.7 (I848T, I228M), whereas no mutations of coding regions of Navs were found in 5 patients with EM. Irrespective of Nav1.7 mutations, more than 50% of the silent nociceptors in the patients with EM showed spontaneous activity. In the patient with mutation I848T, all nociceptors, but not sympathetic efferents, displayed enhanced early subnormal conduction in the velocity recovery cycles and the expected late subnormality was reversed to supranormal conduction. The larger hyperpolarizing shift of activation might explain the difference to the I228M mutation. Sympathetic fibers that lack Nav1.8 did not show supranormal conduction in the patient carrying the I848T mutation, confirming in human subjects that the presence of Nav1.8 crucially modulates conduction in cells expressing EM mutant channels. The characteristic pattern of changes in conduction velocity observed in the patient with the I848T gain-of function mutation in Nav1.7 could be explained by axonal depolarization and concomitant inactivation of Nav1.7. If this were true, activity-dependent hyperpolarization would reverse inactivation of Nav1.7 and account for the supranormal CV. This mechanism might explain normal pain thresholds under resting conditions.
Collapse
|
15
|
Tigerholm J, Petersson ME, Obreja O, Eberhardt E, Namer B, Weidner C, Lampert A, Carr RW, Schmelz M, Fransén E. C-fiber recovery cycle supernormality depends on ion concentration and ion channel permeability. Biophys J 2016; 108:1057-71. [PMID: 25762318 DOI: 10.1016/j.bpj.2014.12.034] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 11/30/2014] [Accepted: 12/17/2014] [Indexed: 12/20/2022] Open
Abstract
Following each action potential, C-fiber nociceptors undergo cyclical changes in excitability, including a period of superexcitability, before recovering their basal excitability state. The increase in superexcitability during this recovery cycle depends upon their immediate firing history of the axon, but also determines the instantaneous firing frequency that encodes pain intensity. To explore the mechanistic underpinnings of the recovery cycle phenomenon a biophysical model of a C-fiber has been developed. The model represents the spatial extent of the axon including its passive properties as well as ion channels and the Na/K-ATPase ion pump. Ionic concentrations were represented inside and outside the membrane. The model was able to replicate the typical transitions in excitability from subnormal to supernormal observed empirically following a conducted action potential. In the model, supernormality depended on the degree of conduction slowing which in turn depends upon the frequency of stimulation, in accordance with experimental findings. In particular, we show that activity-dependent conduction slowing is produced by the accumulation of intraaxonal sodium. We further show that the supernormal phase results from a reduced potassium current Kdr as a result of accumulation of periaxonal potassium in concert with a reduced influx of sodium through Nav1.7 relative to Nav1.8 current. This theoretical prediction was supported by data from an in vitro preparation of small rat dorsal root ganglion somata showing a reduction in the magnitude of tetrodotoxin-sensitive relative to tetrodotoxin -resistant whole cell current. Furthermore, our studies provide support for the role of depolarization in supernormality, as previously suggested, but we suggest that the basic mechanism depends on changes in ionic concentrations inside and outside the axon. The understanding of the mechanisms underlying repetitive discharges in recovery cycles may provide insight into mechanisms of spontaneous activity, which recently has been shown to correlate to a perceived level of pain.
Collapse
Affiliation(s)
- Jenny Tigerholm
- Department of Computational Biology, School of Computer Science and Communication, KTH Royal Institute of Technology, Stockholm, Sweden; Stockholm Brain Institute, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Marcus E Petersson
- Department of Computational Biology, School of Computer Science and Communication, KTH Royal Institute of Technology, Stockholm, Sweden; Stockholm Brain Institute, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Otilia Obreja
- Anaesthesiology, Universitaetsmedizin Mannheim, University of Heidelberg, Mannheim, Germany
| | - Esther Eberhardt
- Institute of Physiology and Pathophysiology, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Barbara Namer
- Department of Anesthesiology, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Christian Weidner
- Department of Anesthesiology, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Angelika Lampert
- Institute of Physiology and Pathophysiology, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany; Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | - Richard W Carr
- Anaesthesiology, Universitaetsmedizin Mannheim, University of Heidelberg, Mannheim, Germany
| | - Martin Schmelz
- Anaesthesiology, Universitaetsmedizin Mannheim, University of Heidelberg, Mannheim, Germany
| | - Erik Fransén
- Department of Computational Biology, School of Computer Science and Communication, KTH Royal Institute of Technology, Stockholm, Sweden; Stockholm Brain Institute, KTH Royal Institute of Technology, Stockholm, Sweden.
| |
Collapse
|
16
|
Hulse RP. Identification of mechano-sensitive C fibre sensitization and contribution to nerve injury-induced mechanical hyperalgesia. Eur J Pain 2015; 20:615-25. [DOI: 10.1002/ejp.779] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/11/2015] [Indexed: 01/29/2023]
Affiliation(s)
- R. P. Hulse
- Cancer Biology; School of Medicine; University of Nottingham; Queen's Medical Centre; UK
| |
Collapse
|
17
|
Mice and rats differ with respect to activity-dependent slowing of conduction velocity in the saphenous peripheral nerve. Neurosci Lett 2015; 592:12-6. [DOI: 10.1016/j.neulet.2015.02.057] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 02/22/2015] [Accepted: 02/23/2015] [Indexed: 11/23/2022]
|
18
|
François A, Schüetter N, Laffray S, Sanguesa J, Pizzoccaro A, Dubel S, Mantilleri A, Nargeot J, Noël J, Wood JN, Moqrich A, Pongs O, Bourinet E. The Low-Threshold Calcium Channel Cav3.2 Determines Low-Threshold Mechanoreceptor Function. Cell Rep 2015; 10:370-382. [PMID: 25600872 DOI: 10.1016/j.celrep.2014.12.042] [Citation(s) in RCA: 139] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 11/14/2014] [Accepted: 12/18/2014] [Indexed: 12/12/2022] Open
Abstract
The T-type calcium channel Cav3.2 emerges as a key regulator of sensory functions, but its expression pattern within primary afferent neurons and its contribution to modality-specific signaling remain obscure. Here, we elucidate this issue using a unique knockin/flox mouse strain wherein Cav3.2 is replaced by a functional Cav3.2-surface-ecliptic GFP fusion. We demonstrate that Cav3.2 is a selective marker of two major low-threshold mechanoreceptors (LTMRs), Aδ- and C-LTMRs, innervating the most abundant skin hair follicles. The presence of Cav3.2 along LTMR-fiber trajectories is consistent with critical roles at multiple sites, setting their strong excitability. Strikingly, the C-LTMR-specific knockout uncovers that Cav3.2 regulates light-touch perception and noxious mechanical cold and chemical sensations and is essential to build up that debilitates allodynic symptoms of neuropathic pain, a mechanism thought to be entirely A-LTMR specific. Collectively, our findings support a fundamental role for Cav3.2 in touch/pain pathophysiology, validating their critic pharmacological relevance to relieve mechanical and cold allodynia.
Collapse
Affiliation(s)
- Amaury François
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France; CNRS UMR5203, 34095 Montpellier, France; INSERM, U661, 34095 Montpellier, France; Université de Montpellier, 34095 Montpellier, France
| | - Niklas Schüetter
- Department of Physiology, University of Saarland, School of Medicine, Kirrberger Straße 1, 66424 Homburg, Germany
| | - Sophie Laffray
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France; CNRS UMR5203, 34095 Montpellier, France; INSERM, U661, 34095 Montpellier, France; Université de Montpellier, 34095 Montpellier, France
| | - Juan Sanguesa
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France; CNRS UMR5203, 34095 Montpellier, France; INSERM, U661, 34095 Montpellier, France; Université de Montpellier, 34095 Montpellier, France
| | - Anne Pizzoccaro
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France; CNRS UMR5203, 34095 Montpellier, France; INSERM, U661, 34095 Montpellier, France; Université de Montpellier, 34095 Montpellier, France
| | - Stefan Dubel
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France; CNRS UMR5203, 34095 Montpellier, France; INSERM, U661, 34095 Montpellier, France; Université de Montpellier, 34095 Montpellier, France
| | - Annabelle Mantilleri
- Aix-Marseille-Université, CNRS, Institut de Biologie du Développement de Marseille, UMR 7288, 13288 Marseille, France
| | - Joel Nargeot
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France; CNRS UMR5203, 34095 Montpellier, France; INSERM, U661, 34095 Montpellier, France; Université de Montpellier, 34095 Montpellier, France
| | - Jacques Noël
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France; Université de Nice Sophia Antipolis, Institut de Pharmacologie Moléculaire et Cellulaire, UMR7275 CNRS, 660 route des lucioles, 06560 Valbonne, France
| | - John N Wood
- Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK
| | - Aziz Moqrich
- Aix-Marseille-Université, CNRS, Institut de Biologie du Développement de Marseille, UMR 7288, 13288 Marseille, France
| | - Olaf Pongs
- Department of Physiology, University of Saarland, School of Medicine, Kirrberger Straße 1, 66424 Homburg, Germany
| | - Emmanuel Bourinet
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France; CNRS UMR5203, 34095 Montpellier, France; INSERM, U661, 34095 Montpellier, France; Université de Montpellier, 34095 Montpellier, France.
| |
Collapse
|
19
|
Uebner M, Carr RW, Messlinger K, De Col R. Activity-dependent sensory signal processing in mechanically responsive slowly conducting meningeal afferents. J Neurophysiol 2014; 112:3077-85. [DOI: 10.1152/jn.00243.2014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Activity-dependent processes in slowly conducting afferents have been shown to modulate conduction and receptive properties, but it is not known how the frequency of action potential firing determines the responses of such fibers to mechanical stimulation. We examined the responses of slowly conducting meningeal afferents to mechanical stimuli and the influence of preceding action potential activity. In hemisected rat heads with adhering cranial dura mater, recordings were made from meningeal nerves. Dural receptive fields of mechanically sensitive afferent fibers were stimulated with a custom-made electromechanostimulator. Sinusoidal mechanical stimuli of different stimulus durations and amplitudes were applied to produce either high-frequency (phasic) or low-frequency (tonic) discharges. Most fibers showed slowing of their axonal conduction velocity on electrically evoked activity at ≥2 Hz. In this state, the peak firing frequency of phasic responses to a 250-ms mechanical stimulus was significantly reduced compared with control. In contrast, the frequency of tonic responses induced by mechanical stimuli of >500 ms did not change. In a rare subtype of afferents, which showed conduction velocity speeding during activity, an increase in the phasic responses to mechanical stimuli was observed. Depending on the axonal properties of the afferent fibers, encoding of phasic components of mechanical stimuli is altered according to the immediate firing history. Preceding activity in mechanoreceptors slowing their conduction velocity seems to provide a form of low-pass filtering of action potential discharges predominantly reducing the phasic component. This may improve discrimination between harmless and potentially harmful mechanical stimuli in normal tissue.
Collapse
Affiliation(s)
- Michael Uebner
- Institute of Physiology and Pathophysiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany; and
| | - Richard W. Carr
- Department of Anaesthesia and Intensive Care Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Karl Messlinger
- Institute of Physiology and Pathophysiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany; and
| | - Roberto De Col
- Department of Anaesthesia and Intensive Care Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| |
Collapse
|
20
|
Three functionally distinct classes of C-fibre nociceptors in primates. Nat Commun 2014; 5:4122. [PMID: 24947823 PMCID: PMC4072246 DOI: 10.1038/ncomms5122] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Accepted: 05/14/2014] [Indexed: 01/01/2023] Open
Abstract
In primates, C-fibre polymodal nociceptors are broadly classified into two groups based on mechanosensitivity. Here we demonstrate that mechanically sensitive polymodal nociceptors that respond either quickly (QC) or slowly (SC) to a heat stimulus differ in responses to a mild burn, heat sensitization, conductive properties and chemosensitivity. Superficially applied capsaicin and intradermal injection of β-alanine, an MrgprD agonist, excite vigorously all QCs. Only 40% of SCs respond to β-alanine, and their response is only half that of QCs. Mechanically insensitive C-fibres (C-MIAs) are β-alanine insensitive but vigorously respond to capsaicin and histamine with distinct discharge patterns. Calcium imaging reveals that β-alanine and histamine activate distinct populations of capsaicin-responsive neurons in primate dorsal root ganglion. We suggest that histamine itch and capsaicin pain are peripherally encoded in C-MIAs, and that primate polymodal nociceptive afferents form three functionally distinct subpopulations with β-alanine responsive QC fibres likely corresponding to murine MrgprD-expressing, non-peptidergic nociceptive afferents.
Collapse
|
21
|
Tigerholm J, Petersson ME, Obreja O, Lampert A, Carr R, Schmelz M, Fransén E. Modeling activity-dependent changes of axonal spike conduction in primary afferent C-nociceptors. J Neurophysiol 2013; 111:1721-35. [PMID: 24371290 DOI: 10.1152/jn.00777.2012] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Action potential initiation and conduction along peripheral axons is a dynamic process that displays pronounced activity dependence. In patients with neuropathic pain, differences in the modulation of axonal conduction velocity by activity suggest that this property may provide insight into some of the pathomechanisms. To date, direct recordings of axonal membrane potential have been hampered by the small diameter of the fibers. We have therefore adopted an alternative approach to examine the basis of activity-dependent changes in axonal conduction by constructing a comprehensive mathematical model of human cutaneous C-fibers. Our model reproduced axonal spike propagation at a velocity of 0.69 m/s commensurate with recordings from human C-nociceptors. Activity-dependent slowing (ADS) of axonal propagation velocity was adequately simulated by the model. Interestingly, the property most readily associated with ADS was an increase in the concentration of intra-axonal sodium. This affected the driving potential of sodium currents, thereby producing latency changes comparable to those observed for experimental ADS. The model also adequately reproduced post-action potential excitability changes (i.e., recovery cycles) observed in vivo. We performed a series of control experiments replicating blockade of particular ion channels as well as changing temperature and extracellular ion concentrations. In the absence of direct experimental approaches, the model allows specific hypotheses to be formulated regarding the mechanisms underlying activity-dependent changes in C-fiber conduction. Because ADS might functionally act as a negative feedback to limit trains of nociceptor activity, we envisage that identifying its mechanisms may also direct efforts aimed at alleviating neuronal hyperexcitability in pain patients.
Collapse
Affiliation(s)
- Jenny Tigerholm
- Department of Computational Biology, School of Computer Science and Communication, KTH Royal Institute of Technology, Stockholm, Sweden
| | | | | | | | | | | | | |
Collapse
|
22
|
Hirth M, Rukwied R, Gromann A, Turnquist B, Weinkauf B, Francke K, Albrecht P, Rice F, Hägglöf B, Ringkamp M, Engelhardt M, Schultz C, Schmelz M, Obreja O. Nerve growth factor induces sensitization of nociceptors without evidence for increased intraepidermal nerve fiber density. Pain 2013; 154:2500-2511. [DOI: 10.1016/j.pain.2013.07.036] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Revised: 07/09/2013] [Accepted: 07/19/2013] [Indexed: 01/07/2023]
|
23
|
Zotova EG, Arezzo JC. NON-INVASIVE EVALUATION OF NERVE CONDUCTION IN SMALL DIAMETER FIBERS IN THE RAT. PHYSIOLOGY JOURNAL 2013; 2013:254789. [PMID: 23580940 PMCID: PMC3620683 DOI: 10.1155/2013/254789] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A novel non-invasive technique was applied to measure velocity within slow conducting axons in the distal extreme of the sciatic nerve (i.e., digital nerve) in a rat model. The technique is based on the extraction of rectified multiple unit activity (MUA) from in vivo whole nerve compound responses. This method reliably identifies compound action potentials in thinly myelinated fibers conducting at a range of 9-18 m/s (Aδ axons), as well as in a subgroup of unmylinated C fibers conducting at approximately 1-2 m/s. The sensitivity of the method to C-fiber conduction was confirmed by the progressive decrement of the responses in the 1-2 m/s range over a 20-day period following the topical application of capsaicin (ANOVA p<0.03). Increasing the frequency of applied repetitive stimulation over a range of 0.75 Hz to 6.0 Hz produced slowing of conduction and a significant decrease in the magnitude of the compound C-fiber response (ANOVA p<0.01). This technique offers a unique opportunity for the non-invasive, repeatable, and quantitative assessment of velocity in the subsets of Aδ and C fibers in parallel with evaluation of fast nerve conduction.
Collapse
Affiliation(s)
- Elena G. Zotova
- Department of Neurology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY, 10461, USA
| | - Joseph C. Arezzo
- Department of Neurology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY, 10461, USA
- Department of Neuroscience, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY, 10461, USA
| |
Collapse
|
24
|
Double spikes to single electrical stimulation correlates to spontaneous activity of nociceptors in painful neuropathy patients. Pain 2012; 153:391-398. [DOI: 10.1016/j.pain.2011.10.041] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Revised: 09/29/2011] [Accepted: 10/28/2011] [Indexed: 11/21/2022]
|
25
|
Does spontaneous activity in C-nociceptors provide a readout to quantify neuropathic pain? Pain 2011; 153:5-6. [PMID: 22014531 DOI: 10.1016/j.pain.2011.09.027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Revised: 09/29/2011] [Accepted: 09/29/2011] [Indexed: 11/22/2022]
|
26
|
Descoeur J, Pereira V, Pizzoccaro A, Francois A, Ling B, Maffre V, Couette B, Busserolles J, Courteix C, Noel J, Lazdunski M, Eschalier A, Authier N, Bourinet E. Oxaliplatin-induced cold hypersensitivity is due to remodelling of ion channel expression in nociceptors. EMBO Mol Med 2011; 3:266-78. [PMID: 21438154 PMCID: PMC3377073 DOI: 10.1002/emmm.201100134] [Citation(s) in RCA: 271] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Revised: 02/24/2011] [Accepted: 02/28/2011] [Indexed: 11/29/2022] Open
Abstract
Cold hypersensitivity is the hallmark of oxaliplatin-induced neuropathy, which develops in nearly all patients under this chemotherapy. To date, pain management strategies have failed to alleviate these symptoms, hence development of adapted analgesics is needed. Here, we report that oxaliplatin exaggerates cold perception in mice as well as in patients. These symptoms are mediated by primary afferent sensory neurons expressing the thermoreceptor TRPM8. Mechanistically, oxaliplatin promotes over-excitability by drastically lowering the expression of distinct potassium channels (TREK1, TRAAK) and by increasing the expression of pro-excitatory channels such as the hyperpolarization-activated channels (HCNs). These findings are corroborated by the analysis of TREK1-TRAAK null mice and use of the specific HCN inhibitor ivabradine, which abolishes the oxaliplatin-induced cold hypersensibility. These results suggest that oxaliplatin exacerbates cold perception by modulating the transcription of distinct ionic conductances that together shape sensory neuron responses to cold. The translational and clinical implication of these findings would be that ivabradine may represent a tailored treatment for oxaliplatin-induced neuropathy.
Collapse
Affiliation(s)
- Juliette Descoeur
- Département de Physiologie, CNRS, UMR-5203, Institut de Génomique Fonctionnelle, Montpellier, France
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
27
|
Campero M, Bostock H, Baumann TK, Ochoa JL. Activity-dependent slowing properties of an unmyelinated low threshold mechanoreceptor in human hairy skin. Neurosci Lett 2011; 493:92-6. [PMID: 21335061 DOI: 10.1016/j.neulet.2011.02.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Revised: 02/01/2011] [Accepted: 02/05/2011] [Indexed: 02/04/2023]
Abstract
It has been previously shown that unmyelinated afferent fibres in human skin are differentiated not only by their receptor characteristics, but also by their profiles of activity-dependent slowing. One type of profile, described originally as 'type 3', is different from that of nociceptors (type 1), cold afferents (type 2) and sympathetic efferents (type 4), in that these fibres display a minimal activity-dependent slowing (∼1% at 2 Hz). However, their function remains to be determined. Here we describe one unit with a typical 'type 3' activity-dependent slowing profile recorded from an undamaged fascicle of the superficial peroneal nerve of a patient. Its conduction velocity was 1.8 m s(-1) and it slowed by 1.3% during the 2 Hz tetanus. This unit had a mechanical receptive field in the hairy skin and responded readily to weak mechanical stimuli, and not to cold. This suggests that the low threshold unmyelinated mechanoreceptors recently described in human hairy skin are probably endowed with a 'type 3' activity-dependent profile.
Collapse
Affiliation(s)
- Mario Campero
- Facultad de Medicina, Clínica Alemana-Universidad del Desarrollo, Chile.
| | | | | | | |
Collapse
|
28
|
Serra J, Solà R, Aleu J, Quiles C, Navarro X, Bostock H. Double and triple spikes in C-nociceptors in neuropathic pain states: An additional peripheral mechanism of hyperalgesia. Pain 2011; 152:343-353. [DOI: 10.1016/j.pain.2010.10.039] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2010] [Revised: 09/20/2010] [Accepted: 10/27/2010] [Indexed: 10/18/2022]
|
29
|
Feng B, Gebhart GF. Characterization of silent afferents in the pelvic and splanchnic innervations of the mouse colorectum. Am J Physiol Gastrointest Liver Physiol 2011; 300:G170-80. [PMID: 21071510 PMCID: PMC3025511 DOI: 10.1152/ajpgi.00406.2010] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Hypersensitivity in inflammatory/irritable bowel syndrome is contributed to in part by changes in the receptive properties of colorectal afferent endings, likely including mechanically insensitive afferents (MIAs; silent afferents) that have the ability to acquire mechanosensitivity. The proportion and attributes of colorectal MIAs, however, have not previously been characterized. The distal ∼3 cm of colorectum with either pelvic (PN) or lumbar splanchnic (LSN) nerve attached was removed, opened longitudinally, pinned flat in a recording chamber, and perfused with oxygenated Krebs solution. Colorectal receptive endings were located by electrical stimulation and characterized as mechanosensitive or not by blunt probing, mucosal stroking, and circumferential stretch. MIA endings were tested for response to and acquisition of mechanosensitivity by localized exposure to an inflammatory soup (IS). Colorectal afferents were also tested with twin-pulse and repetitive electrical stimulation paradigms. PN MIAs represented 23% of 211 afferents studied, 71% (30/42) of which acquired mechanosensitivity after application of IS to their receptive ending. LSN MIAs represented 33% of 156 afferents studied, only 23% (11/48) of which acquired mechanosensitivity after IS exposure. Mechanosensitive PN endings uniformly exhibited significant twin-pulse slowing whereas LSN endings showed no significant twin-pulse difference. PN MIAs displayed significantly greater activity-dependent slowing than LSN MIAs. In conclusion, significant proportions of MIAs are present in the colorectal innervation; significantly more in the PN than LSN acquire mechanosensitivity in an inflammatory environment. This knowledge contributes to our understanding of the possible roles of MIAs in colon-related disorders like inflammatory/irritable bowel syndrome.
Collapse
Affiliation(s)
- Bin Feng
- Center for Pain Research, Univ. of Pittsburgh, W1402 BST, 200 Lothrop St., Pittsburgh, PA 15213, USA.
| | | |
Collapse
|
30
|
Ringkamp M, Johanek LM, Borzan J, Hartke TV, Wu G, Pogatzki-Zahn EM, Campbell JN, Shim B, Schepers RJ, Meyer RA. Conduction properties distinguish unmyelinated sympathetic efferent fibers and unmyelinated primary afferent fibers in the monkey. PLoS One 2010; 5:e9076. [PMID: 20140089 PMCID: PMC2816714 DOI: 10.1371/journal.pone.0009076] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Accepted: 01/11/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Different classes of unmyelinated nerve fibers appear to exhibit distinct conductive properties. We sought a criterion based on conduction properties for distinguishing sympathetic efferents and unmyelinated, primary afferents in peripheral nerves. METHODOLOGY/PRINCIPAL FINDINGS In anesthetized monkey, centrifugal or centripetal recordings were made from single unmyelinated nerve fibers in the peroneal or sural nerve, and electrical stimuli were applied to either the sciatic nerve or the cutaneous nerve endings, respectively. In centrifugal recordings, electrical stimulation at the sympathetic chain and dorsal root was used to determine the fiber's origin. In centrifugal recordings, sympathetic fibers exhibited absolute speeding of conduction to a single pair of electrical stimuli separated by 50 ms; the second action potential was conducted faster (0.61 0.16%) than the first unconditioned action potential. This was never observed in primary afferents. Following 2 Hz stimulation (3 min), activity-dependent slowing of conduction in the sympathetics (8.6 0.5%) was greater than in one afferent group (6.7 0.5%) but substantially less than in a second afferent group (29.4 1.9%). In centripetal recordings, most mechanically-insensitive fibers also exhibited absolute speeding to twin pulse stimulation. The subset that did not show this absolute speeding was responsive to chemical stimuli (histamine, capsaicin) and likely consists of mechanically-insensitive afferents. During repetitive twin pulse stimulation, mechanosensitive afferents developed speeding, and speeding in sympathetic fibers increased. CONCLUSIONS/SIGNIFICANCE The presence of absolute speeding provides a criterion by which sympathetic efferents can be differentiated from primary afferents. The differences in conduction properties between sympathetics and afferents likely reflect differential expression of voltage-sensitive ion channels.
Collapse
Affiliation(s)
- Matthias Ringkamp
- Department of Neurosurgery, School of Medicine, Johns Hopkins University, Baltimore, Maryland, United States of America.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
31
|
Handwerker HO. Classification of nociceptors--to what purpose? Pain 2010; 148:355-356. [PMID: 20097476 DOI: 10.1016/j.pain.2009.12.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2009] [Accepted: 12/18/2009] [Indexed: 10/19/2022]
Affiliation(s)
- Hermann O Handwerker
- Department of Physiology and Pathophysiology, University of Erlangen/Nuremberg, Universitaetsstr. 17, 91054 Erlangen, Germany
| |
Collapse
|
32
|
Obreja O, Ringkamp M, Namer B, Forsch E, Klusch A, Rukwied R, Petersen M, Schmelz M. Patterns of activity-dependent conduction velocity changes differentiate classes of unmyelinated mechano-insensitive afferents including cold nociceptors, in pig and in human. Pain 2010; 148:59-69. [DOI: 10.1016/j.pain.2009.10.006] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Revised: 09/08/2009] [Accepted: 10/06/2009] [Indexed: 11/30/2022]
|
33
|
Campero M, Baumann TK, Bostock H, Ochoa JL. Human cutaneous C fibres activated by cooling, heating and menthol. J Physiol 2009; 587:5633-52. [PMID: 19822550 DOI: 10.1113/jphysiol.2009.176040] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Differential A-fibre block of human peripheral nerves changes the sensation evoked by innocuous cooling (approximately 24 degrees C) of the skin from 'cold' to 'hot' or 'burning', and this has been attributed to activity in unidentified unmyelinated fibres that is normally masked or inhibited by activity in Adelta cold fibres. Application of the TRPM8 agonist menthol to the skin evokes 'burning/stinging' as well as 'cold', and the unpleasant sensations are also enhanced by A-fibre block. In this study we used microneurography to search for C fibres in human skin activated by cooling and menthol, which could be responsible for these phenomena. Afferent C fibres were classified by activity-dependent slowing as Type 1A (polymodal nociceptor), Type 1B (mechanically insensitive nociceptor) or Type 2 (cold sensitive), and their responses to heating and cooling ramps were measured before and after topical application of menthol preparations (2-50%). The only C fibres activated by menthol were the Type 2 fibres, which discharged vigorously with innocuous cooling and were strongly activated and sensitized to cooling by menthol. Unlike an Adelta cold fibre, they continued to discharge at skin temperatures down to 0 degrees C, and most (13/15) were also activated by heating. We propose that the Type 2 C fibres, although resembling Adelta cold fibres in their responses to innocuous cooling and menthol, have a more complex sensory function, colouring with a 'hot-burning' quality the perceptions of low and high temperatures. Their bimodal thermoreceptive properties may help account for several puzzling psychophysical phenomena, such as 'innocuous cold nociception', 'paradoxical heat' and the thermal grill illusion, and also for some neuropathic pains.
Collapse
Affiliation(s)
- M Campero
- Facultad de Medicina, Clinica Alemana-Universidad del Desarrollo, Santiago, Chile.
| | | | | | | |
Collapse
|
34
|
Microneurography in rats: a minimally invasive method to record single C-fiber action potentials from peripheral nerves in vivo. Neurosci Lett 2009; 470:168-74. [PMID: 19800936 DOI: 10.1016/j.neulet.2009.09.061] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2009] [Revised: 09/27/2009] [Accepted: 09/28/2009] [Indexed: 10/20/2022]
Abstract
Microneurography is a method suitable for recording intraneural single or multiunit action potentials in conscious subjects. Microneurography has rarely been applied to animal experiments, where more invasive methods, like the teased fiber recording technique, are widely used. We have tested the feasibility of microneurographic recordings from the peripheral nerves of rats. Tungsten microelectrodes were inserted into the sciatic nerve at mid-thigh level. Single or multiunit action potentials evoked by regular electrical stimulation were recorded, digitized and displayed as a raster plot of latencies. The method allows unambiguous recording and recognition of single C-fiber action potentials from an in vivo preparation, with minimal disruption of the nerve being recorded. Multiple C-fibers can be recorded simultaneously for several hours, and if the animal is allowed to recover, repeated recording sessions can be obtained from the same nerve at the same level over a period of weeks or months. Also, single C units can be functionally identified by their changes in latency to natural stimuli, and insensitive units can be recognized as 'silent' nociceptors or sympathetic efferents by their distinctive profiles of activity-dependent slowing during repetitive electrical stimulation, or by the effect on spontaneous efferent activity of a proximal anesthetic block. Moreover, information about the biophysical properties of C axons can be obtained from their latency recovery cycles. Finally, we show that this preparation is potentially suitable for the study of C-fiber behavior in models of neuropathies and nerve lesions, both under resting conditions and in response to drug administration.
Collapse
|
35
|
Goldfinger MD. Probability distributions of Markovian sodium channel states during propagating axonal impulses with or without recovery supernormality. J Integr Neurosci 2009; 8:203-21. [PMID: 19618487 DOI: 10.1142/s0219635209002125] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Accepted: 05/06/2009] [Indexed: 12/19/2022] Open
Abstract
This study addressed a macroscopic neurophysiological phenomenon - supernormality during the recovery phase of propagating axonal impulses - in explicit chemical terms. Excitation was reconstructed numerically using the kinetic scheme of multiple-state probabilistic transitions within a population of voltage-dependent sodium channels (NaCh) derived by Vandenberg and Bezanilla ("PC" scheme). Each NaCh transition was characterized as a reversible Markov process with voltage-dependent rate constants associated with each respective directional transition. While recovery reconstructed with the Hodgkin-Huxley formalism included a supernormal period, the PC scheme did not. The present analysis showed that the occurrence and degree of supernormality with the PC scheme was determined by the relative speed of the transitions within the closed loop of the kinetic scheme; supernormality was promoted by speeding these kinetics. The analysis also showed that concurrent with supernormality, the faster loop kinetics caused (1) an elevation in the C(1) --> C(2) transitions, and (2) a reduction in the I(4) --> I(5) transitions. Thus, macroscopic functionality in information processing could be expressed in terms of probabilistic interstate transitions among a population of NaCh molecules.
Collapse
Affiliation(s)
- M D Goldfinger
- Department of Neuroscience, Cell Biology, & Physiology, Wright State University, Dayton, Ohio 45435, USA.
| |
Collapse
|
36
|
Microneurographic single-unit recordings to assess receptive properties of afferent human C-fibers. Neurosci Lett 2009; 470:158-61. [PMID: 19481585 DOI: 10.1016/j.neulet.2009.05.064] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Revised: 04/24/2009] [Accepted: 05/20/2009] [Indexed: 11/16/2022]
Abstract
Action potentials in unmyelinated peripheral axons can be recorded in awake humans by microneurography with small electrodes placed in a peripheral nerve. This technique provides extracellular recordings of single C-fibers and thus enables characterization of their sensory and axonal properties. By using microneurographical basic properties of afferent C-fibers such as conduction velocities, innervation territories, sensory thresholds and chemical responsiveness were measured. Moreover, axonal excitability changes induced by repetitive activation were assessed. Sensory and axonal properties of the different fiber classes cluster. Based on those specific properties, unitary functional classes of nociceptors (such as polymodal nociceptors and mechano-insensitive nociceptors) and non-nociceptors (such as tactile afferents and warm fibers) were classified. With normal data available, sensitization and desensitization of afferent fibers have been found in pathophysiologic states as detected in chronic pain patients. As subjects and patients are awake during the recording, microneurography provides a unique tool to correlate the discharge behaviour of afferent nerve fibers with the sensation evoked by certain stimuli.
Collapse
|
37
|
Z'Graggen WJ, Bostock H. Velocity recovery cycles of human muscle action potentials and their sensitivity to ischemia. Muscle Nerve 2009; 39:616-26. [DOI: 10.1002/mus.21192] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
38
|
Namer B, Handwerker HO. Translational nociceptor research as guide to human pain perceptions and pathophysiology. Exp Brain Res 2009; 196:163-72. [PMID: 19350229 DOI: 10.1007/s00221-009-1777-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Accepted: 03/17/2009] [Indexed: 01/12/2023]
Abstract
Microneurography is a method for recording single unit action potentials with microelectrodes from the nerves of awake cooperating humans. Although this method is now in use since almost 40 years, its potency has been strengthened by the recent technical developments. A great progress was the discovery that different functional groups of nociceptors are characterized by a distinctly different post-excitatory slowing of their conduction velocities. Microneurography is now powerful enough to analyze the nerve activity pattern of enigmatic sensations such as pruritus. Furthermore, it is the only method providing direct insight in the changes which human nerves undergo with aging. Recently, reliable recordings from patients suffering from painful neuropathies came into reach. It has been shown that different types of neuropathies are characterized by different patterns of abnormal nociceptor functions. Although some of them are characterized by abnormal spontaneous activity in C-nociceptors, others show mainly signs of denervation. Microneurography is, therefore, a tool for translational studies on human nociceptor functions by linking direct animal studies on experimental neuropathies with human diseases.
Collapse
Affiliation(s)
- Barbara Namer
- Department of Physiology and Pathophysiology, Institut für Physiologie und Pathophysiologie, University of Erlangen/Nuernberg, Universitätsstr. 17, 91054 Erlangen, Germany
| | | |
Collapse
|
39
|
Kuwabara S. Ionic mechanisms for paresthesias arising from human sensory axons. Clin Neurophysiol 2008; 119:1945-6. [PMID: 18571980 DOI: 10.1016/j.clinph.2008.04.296] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2008] [Revised: 04/26/2008] [Accepted: 04/29/2008] [Indexed: 11/29/2022]
|
40
|
De Col R, Messlinger K, Carr RW. Conduction velocity is regulated by sodium channel inactivation in unmyelinated axons innervating the rat cranial meninges. J Physiol 2007; 586:1089-103. [PMID: 18096592 DOI: 10.1113/jphysiol.2007.145383] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Axonal conduction velocity varies according to the level of preceding impulse activity. In unmyelinated axons this typically results in a slowing of conduction velocity and a parallel increase in threshold. It is currently held that Na(+)-K(+)-ATPase-dependent axonal hyperpolarization is responsible for this slowing but this has long been equivocal. We therefore examined conduction velocity changes during repetitive activation of single unmyelinated axons innervating the rat cranial meninges. In direct contradiction to the currently accepted postulate, Na(+)-K(+)-ATPase blockade actually enhanced activity-induced conduction velocity slowing, while the degree of velocity slowing was curtailed in the presence of lidocaine (10-300 microm) and carbamazepine (30-500 microm) but not tetrodotoxin (TTX, 10-80 nm). This suggests that a change in the number of available sodium channels is the most prominent factor responsible for activity-induced changes in conduction velocity in unmyelinated axons. At moderate stimulus frequencies, axonal conduction velocity is determined by an interaction between residual sodium channel inactivation following each impulse and the retrieval of channels from inactivation by a concomitant Na(+)-K(+)-ATPase-mediated hyperpolarization. Since the process is primarily dependent upon sodium channel availability, tracking conduction velocity provides a means of accessing relative changes in the excitability of nociceptive neurons.
Collapse
Affiliation(s)
- Roberto De Col
- Institute for Physiology and Pathophysiology, University of Erlangen-Nuremberg, Erlangen, Germany
| | | | | |
Collapse
|
41
|
Moalem-Taylor G, Lang PM, Tracey DJ, Grafe P. Post-spike excitability indicates changes in membrane potential of isolated C-fibers. Muscle Nerve 2007; 36:172-82. [PMID: 17487863 DOI: 10.1002/mus.20793] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Recording of action potentials from single unmyelinated nerve fibers by microneurography is an important tool to investigate peripheral neural functions in human neuropathies. However, the interpretation of microneurography recordings can be difficult because axonal membrane potential is not revealed by this method. We tested the hypothesis that the recovery cycle of excitability after a single action potential is correlated with changes in the axonal membrane potential. To this end, we used the threshold tracking technique to study how different chemical mediators, with known effects on the membrane potential, influence the post-spike superexcitability of C-fiber compound action potentials in isolated rat sural and vagus nerves. We found that: (1) some chemical mediators (e.g., adenosine 5'-triphosphate) produce a reduction or loss of superexcitability together with increased axonal excitability, indicating membrane depolarization; (2) blockade of axonal hyperpolarization-activated (Ih) currents produces an enhancement of superexcitability together with a decreased excitability, indicating membrane hyperpolarization; and (3) application of calcium produces an increase in membrane threshold without an alteration in superexcitability, indicating a non-specific increase in surface charge and a change in the voltage-dependent activation of sodium channels. In addition, we demonstrated that membrane depolarization and hyperpolarization induce opposite post-spike latency shifts (changes in supernormality) in rat and human nerve segments. Thus, recordings of post-spike excitability and shifts in latency are sensitive techniques for detection of various types of neuromodulation, which are correlated with changes in membrane potential of unmyelinated peripheral axons and may help to understand observations obtained by microneurography in peripheral human neuropathies.
Collapse
Affiliation(s)
- Gila Moalem-Taylor
- School of Medical Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
| | | | | | | |
Collapse
|
42
|
Affiliation(s)
- David Burke
- Institute of Clinical Neurosciences, University of Sydney and Royal Prince Alfred Hospital, Sydney, New South Wales 2006, Australia.
| |
Collapse
|