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Wilcox M, Brown H, Johnson K, Sinisi M, Quick TJ. An assessment of co-contraction in reinnervated muscle. Regen Med 2024; 19:161-170. [PMID: 37955237 DOI: 10.2217/rme-2023-0049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2023] Open
Abstract
Aim: To investigate co-contraction in reinnervated elbow flexor muscles following a nerve transfer. Materials & methods: 12 brachial plexus injury patients who received a nerve transfer to reanimate elbow flexion were included in this study. Surface electromyography (EMG) recordings were used to quantify co-contraction during sustained and repeated isometric contractions of reinnervated and contralateral uninjured elbow flexor muscles. Reuslts: For the first time, this study reveals reinnervated muscles demonstrated a trend toward higher co-contraction ratios when compared with uninjured muscle and this is correlated with an earlier onset of muscle fatigability. Conclusion: Measurements of co-contraction should be considered within muscular function assessments to help drive improvements in motor recovery therapies.
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Affiliation(s)
- Matthew Wilcox
- Peripheral Nerve Injury Research Unit, Royal National Orthopaedic Hospital, London, HA7 4LP, UK
- University College London Centre for Nerve Engineering, London, WC1E 6BT, UK
- Department of Pharmacology, University College London, School of Pharmacy, London, WC1N 1AX, UK
| | - Hazel Brown
- Peripheral Nerve Injury Research Unit, Royal National Orthopaedic Hospital, London, HA7 4LP, UK
- University College London Centre for Nerve Engineering, London, WC1E 6BT, UK
| | - Kathryn Johnson
- Peripheral Nerve Injury Research Unit, Royal National Orthopaedic Hospital, London, HA7 4LP, UK
| | - Marco Sinisi
- Peripheral Nerve Injury Research Unit, Royal National Orthopaedic Hospital, London, HA7 4LP, UK
| | - Tom J Quick
- Peripheral Nerve Injury Research Unit, Royal National Orthopaedic Hospital, London, HA7 4LP, UK
- University College London Centre for Nerve Engineering, London, WC1E 6BT, UK
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Lulic-Kuryllo T, Leonardis JM, Momoh AO, Lipps DB. Assessing shoulder muscle stretch reflexes following breast cancer treatment and postmastectomy breast reconstruction. J Neurophysiol 2023; 129:914-926. [PMID: 36947887 PMCID: PMC10110716 DOI: 10.1152/jn.00081.2022] [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: 03/01/2022] [Revised: 03/13/2023] [Accepted: 03/16/2023] [Indexed: 03/24/2023] Open
Abstract
Muscle stiffness is altered following postmastectomy breast reconstruction and breast cancer treatment. The exact mechanisms underlying these alterations are unknown; however, muscle stretch reflexes may play a role. This work examined short- (SLR) and long-latency (LLR) shoulder muscle stretch reflexes in breast cancer survivors. Forty-nine patients who had undergone postmastectomy breast reconstruction, 17 who had undergone chemoradiation, and 18 healthy, age-matched controls were enrolled. Muscle activity was recorded from the clavicular and sternocostal regions of the pectoralis major and anterior, middle, and posterior deltoids during vertical ab/adduction or horizontal flex/extension perturbations while participants maintained minimal torques. SLR and LLR were quantified for each muscle. Our major finding was that following postmastectomy breast reconstruction, SLR and LLR are impaired in the clavicular region of the pectoralis major. Individuals who had chemoradiation had impaired stretch reflexes in the clavicular and sternocostal region of the pectoralis major, anterior, middle, and posterior deltoid. These findings indicate that breast cancer treatments alter the regulation of shoulder muscle stretch reflexes and may be associated with surgical or nonsurgical damage to the pectoral fascia, muscle spindles, and/or sensory Ia afferents.NEW & NOTEWORTHY Shoulder muscle stretch reflexes may be impacted following postmastectomy breast reconstruction and chemoradiation. Here, we examined short- and long-latency shoulder muscle stretch reflexes in two experiments following common breast reconstruction procedures and chemoradiation. We show impairments in pectoralis major stretch reflexes following postmastectomy breast reconstruction and pectoralis major and deltoid muscle stretch reflexes following chemoradiation. These findings indicate that breast cancer treatments alter the regulation of shoulder muscle stretch reflexes.
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Affiliation(s)
- Tea Lulic-Kuryllo
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States
| | - Joshua M Leonardis
- College of Applied Health Sciences, University of Illinois, Urbana-Champaign, Illinois, United States
| | - Adeyiza O Momoh
- Section of Plastic Surgery, University of Michigan, Ann Arbor, Michigan, United States
| | - David B Lipps
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States
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3
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Sonkodi B, Pállinger É, Radovits T, Csulak E, Shenker-Horváth K, Kopper B, Buzás EI, Sydó N, Merkely B. CD3+/CD56+ NKT-like Cells Show Imbalanced Control Immediately after Exercise in Delayed-Onset Muscle Soreness. Int J Mol Sci 2022; 23:ijms231911117. [PMID: 36232420 PMCID: PMC9569472 DOI: 10.3390/ijms231911117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 09/15/2022] [Accepted: 09/19/2022] [Indexed: 11/24/2022] Open
Abstract
The purpose of the study was to carry out an immunophenotypical characterization with a special focus on natural killer cells of junior swimmers from the Hungarian National Swim Team before and after an intensive acute exercise. Nineteen swimmers, ten females and nine males, completed the exercise protocol. Sixteen swimmers experienced delayed-onset muscle soreness. Most of our findings substantiated earlier results, such as the increase in the percentage of the CD3−/CD56+ natural killer cells and the CD3−/CD56dim+ NK cells, and the decrease in the percentage of CD3+ T cells among lymphocytes after the exercise protocol. The drop of natural killer cell activity back to the pre-exercise level was in line with earlier findings. Interestingly, the percentage of CD3+/CD56+ NKT-like cells did not change significantly in those three swimmers who did not report delayed-onset muscle soreness. On the contrary, the percentage of CD3+/CD56+ NKT-like cells among lymphocytes increased in fourteen and decreased in two swimmers reporting delayed-onset muscle soreness. This study for the first time demonstrated a link between the delayed-onset muscle soreness and the imbalanced control of CD3+/CD56+ NKT-like cells among lymphocytes. However, validation of this association in a larger sample size study will be necessary.
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Affiliation(s)
- Balázs Sonkodi
- Department of Health Sciences and Sport Medicine, Hungarian University of Sports Science, 1123 Budapest, Hungary
- Correspondence:
| | - Éva Pállinger
- Department of Genetics, Cell- and Immunobiology, Semmelweis University, 1085 Budapest, Hungary
| | - Tamás Radovits
- Heart and Vascular Center, Semmelweis University, 1122 Budapest, Hungary
| | - Emese Csulak
- Heart and Vascular Center, Semmelweis University, 1122 Budapest, Hungary
| | | | - Bence Kopper
- Faculty of Kinesiology, Hungarian University of Sports Science, 1123 Budapest, Hungary
| | - Edit I. Buzás
- Department of Genetics, Cell- and Immunobiology, Semmelweis University, 1085 Budapest, Hungary
- HCEMM-SU Extracellular Vesicle Research Group, 1089 Budapest, Hungary
- ELKH-SE Translational Extracellular Vesicle Research Group, 1089 Budapest, Hungary
| | - Nóra Sydó
- Heart and Vascular Center, Semmelweis University, 1122 Budapest, Hungary
- Department of Sports Medicine, Semmelweis University, 1122 Budapest, Hungary
| | - Béla Merkely
- Heart and Vascular Center, Semmelweis University, 1122 Budapest, Hungary
- Department of Sports Medicine, Semmelweis University, 1122 Budapest, Hungary
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Delayed Onset Muscle Soreness and Critical Neural Microdamage-Derived Neuroinflammation. Biomolecules 2022; 12:biom12091207. [PMID: 36139045 PMCID: PMC9496513 DOI: 10.3390/biom12091207] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 08/26/2022] [Accepted: 08/30/2022] [Indexed: 02/06/2023] Open
Abstract
Piezo2 transmembrane excitatory mechanosensitive ion channels were identified as the principal mechanotransduction channels for proprioception. Recently, it was postulated that Piezo2 channels could be acutely microdamaged on an autologous basis at proprioceptive Type Ia terminals in a cognitive demand-induced acute stress response time window when unaccustomed or strenuous eccentric contractions are executed. One consequence of this proposed transient Piezo2 microinjury could be a VGLUT1/Ia synaptic disconnection on motoneurons, as we can learn from platinum-analogue chemotherapy. A secondary, harsher injury phase with the involvement of polymodal Aδ and nociceptive C-fibers could follow the primary impairment of proprioception of delayed onset muscle soreness. Repetitive reinjury of these channels in the form of repeated bout effects is proposed to be the tertiary injury phase. Notably, the use of proprioception is associated with motor learning and memory. The impairment of the monosynaptic static phase firing sensory encoding of the affected stretch reflex could be the immediate consequence of the proposed Piezo2 microdamage leading to impaired proprioception, exaggerated contractions and reduced range of motion. These transient Piezo2 channelopathies in the primary afferent terminals could constitute the critical gateway to the pathophysiology of delayed onset muscle soreness. Correspondingly, fatiguing eccentric contraction-based pathological hyperexcitation of the Type Ia afferents induces reactive oxygen species production-associated neuroinflammation and neuronal activation in the spinal cord of delayed onset muscle soreness.
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Sonkodi B, Hegedűs Á, Kopper B, Berkes I. Significantly Delayed Medium-Latency Response of the Stretch Reflex in Delayed-Onset Muscle Soreness of the Quadriceps Femoris Muscles Is Indicative of Sensory Neuronal Microdamage. J Funct Morphol Kinesiol 2022; 7:jfmk7020043. [PMID: 35736014 PMCID: PMC9224667 DOI: 10.3390/jfmk7020043] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 05/24/2022] [Accepted: 05/26/2022] [Indexed: 11/16/2022] Open
Abstract
Unaccustomed or strenuous eccentric exercise is known to cause delayed-onset muscle soreness. A recent hypothesis postulated that mechano-energetic microinjury of the primary afferent sensory neuron terminals in the muscle spindles, namely a transient Piezo2 channelopathy, could be the critical cause of delayed-onset muscle soreness in the form of a bi-phasic non-contact injury mechanism. This theory includes that this microlesion could delay the medium-latency response of the stretch reflex. Our aim with this study was to investigate this hypothesis. According to our knowledge, no study has examined the effect of delayed-onset muscle soreness on the medium-latency response of the stretch reflex. Our findings demonstrated that a significant delay in the medium-latency stretch reflex could be observed right after a multi-stage fitness test in the quadriceps femoris muscles of Hungarian professional handball players who consequently experienced delayed-onset muscle soreness. The long-latency stretch reflex and most likely short-latency stretch reflex were unaffected by delayed-onset muscle soreness in our study, which is in line with earlier findings. We translate these findings as indicative of proprioceptive Type Ia terminal microdamage in the muscle spindle in line with the aforementioned new acute non-contact compression axonopathy theory of delayed-onset muscles soreness.
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Affiliation(s)
- Balázs Sonkodi
- Department of Health Sciences and Sport Medicine, Hungarian University of Sport Science, 1123 Budapest, Hungary;
- Correspondence:
| | - Ádám Hegedűs
- Faculty of Kinesiology, Hungarian University of Sport Science, 1123 Budapest, Hungary; (Á.H.); (B.K.)
| | - Bence Kopper
- Faculty of Kinesiology, Hungarian University of Sport Science, 1123 Budapest, Hungary; (Á.H.); (B.K.)
| | - István Berkes
- Department of Health Sciences and Sport Medicine, Hungarian University of Sport Science, 1123 Budapest, Hungary;
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6
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Kröger S, Watkins B. Muscle spindle function in healthy and diseased muscle. Skelet Muscle 2021; 11:3. [PMID: 33407830 PMCID: PMC7788844 DOI: 10.1186/s13395-020-00258-x] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Accepted: 12/20/2020] [Indexed: 12/16/2022] Open
Abstract
Almost every muscle contains muscle spindles. These delicate sensory receptors inform the central nervous system (CNS) about changes in the length of individual muscles and the speed of stretching. With this information, the CNS computes the position and movement of our extremities in space, which is a requirement for motor control, for maintaining posture and for a stable gait. Many neuromuscular diseases affect muscle spindle function contributing, among others, to an unstable gait, frequent falls and ataxic behavior in the affected patients. Nevertheless, muscle spindles are usually ignored during examination and analysis of muscle function and when designing therapeutic strategies for neuromuscular diseases. This review summarizes the development and function of muscle spindles and the changes observed under pathological conditions, in particular in the various forms of muscular dystrophies.
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Affiliation(s)
- Stephan Kröger
- Department of Physiological Genomics, Biomedical Center, Ludwig-Maximilians-University Munich, Großhaderner Str. 9, 82152, Planegg-Martinsried, Germany.
| | - Bridgette Watkins
- Department of Physiological Genomics, Biomedical Center, Ludwig-Maximilians-University Munich, Großhaderner Str. 9, 82152, Planegg-Martinsried, Germany
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Alvarez FJ, Rotterman TM, Akhter ET, Lane AR, English AW, Cope TC. Synaptic Plasticity on Motoneurons After Axotomy: A Necessary Change in Paradigm. Front Mol Neurosci 2020; 13:68. [PMID: 32425754 PMCID: PMC7203341 DOI: 10.3389/fnmol.2020.00068] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 04/08/2020] [Indexed: 12/12/2022] Open
Abstract
Motoneurons axotomized by peripheral nerve injuries experience profound changes in their synaptic inputs that are associated with a neuroinflammatory response that includes local microglia and astrocytes. This reaction is conserved across different types of motoneurons, injuries, and species, but also displays many unique features in each particular case. These reactions have been amply studied, but there is still a lack of knowledge on their functional significance and mechanisms. In this review article, we compiled data from many different fields to generate a comprehensive conceptual framework to best interpret past data and spawn new hypotheses and research. We propose that synaptic plasticity around axotomized motoneurons should be divided into two distinct processes. First, a rapid cell-autonomous, microglia-independent shedding of synapses from motoneuron cell bodies and proximal dendrites that is reversible after muscle reinnervation. Second, a slower mechanism that is microglia-dependent and permanently alters spinal cord circuitry by fully eliminating from the ventral horn the axon collaterals of peripherally injured and regenerating sensory Ia afferent proprioceptors. This removes this input from cell bodies and throughout the dendritic tree of axotomized motoneurons as well as from many other spinal neurons, thus reconfiguring ventral horn motor circuitries to function after regeneration without direct sensory feedback from muscle. This process is modulated by injury severity, suggesting a correlation with poor regeneration specificity due to sensory and motor axons targeting errors in the periphery that likely render Ia afferent connectivity in the ventral horn nonadaptive. In contrast, reversible synaptic changes on the cell bodies occur only while motoneurons are regenerating. This cell-autonomous process displays unique features according to motoneuron type and modulation by local microglia and astrocytes and generally results in a transient reduction of fast synaptic activity that is probably replaced by embryonic-like slow GABA depolarizations, proposed to relate to regenerative mechanisms.
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Affiliation(s)
- Francisco J Alvarez
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, United States
| | - Travis M Rotterman
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, United States.,Department of Biomedical Engineering, School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, United States
| | - Erica T Akhter
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, United States
| | - Alicia R Lane
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, United States
| | - Arthur W English
- Department of Cellular Biology, Emory University School of Medicine, Atlanta, GA, United States
| | - Timothy C Cope
- Department of Biomedical Engineering, School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, United States
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9
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Vincent JA, Gabriel HM, Deardorff AS, Nardelli P, Fyffe REW, Burkholder T, Cope TC. Muscle proprioceptors in adult rat: mechanosensory signaling and synapse distribution in spinal cord. J Neurophysiol 2017; 118:2687-2701. [PMID: 28814636 PMCID: PMC5672542 DOI: 10.1152/jn.00497.2017] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Revised: 08/15/2017] [Accepted: 08/16/2017] [Indexed: 12/23/2022] Open
Abstract
The characteristic signaling and intraspinal projections of muscle proprioceptors best described in the cat are often generalized across mammalian species. However, species-dependent adaptations within this system seem necessary to accommodate asymmetric scaling of length, velocity, and force information required by the physics of movement. In the present study we report mechanosensory responses and intraspinal destinations of three classes of muscle proprioceptors. Proprioceptors from triceps surae muscles in adult female Wistar rats anesthetized with isoflurane were physiologically classified as muscle spindle group Ia or II or as tendon organ group Ib afferents, studied for their firing responses to passive-muscle stretch, and in some cases labeled and imaged for axon projections and varicosities in spinal segments. Afferent projections and the laminar distributions of provisional synapses in rats closely resembled those found in the cat. Afferent signaling of muscle kinematics was also similar to reports in the cat, but rat Ib afferents fired robustly during passive-muscle stretch and Ia afferents displayed an exaggerated dynamic response, even after locomotor scaling was accounted for. These differences in mechanosensory signaling by muscle proprioceptors may represent adaptations for movement control in different animal species.NEW & NOTEWORTHY Muscle sensory neurons signal information necessary for controlling limb movements. The information encoded and transmitted by muscle proprioceptors to networks in the spinal cord is known in detail only for the cat, but differences in size and behavior of other species challenge the presumed generalizability. This report presents the first findings detailing specializations in mechanosensory signaling and intraspinal targets for functionally identified subtypes of muscle proprioceptors in the rat.
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Affiliation(s)
- Jacob A Vincent
- Department of Neuroscience, Cell Biology, and Physiology, Wright State University, Dayton, Ohio
| | - Hanna M Gabriel
- Department of Neuroscience, Cell Biology, and Physiology, Wright State University, Dayton, Ohio
| | - Adam S Deardorff
- Department of Neuroscience, Cell Biology, and Physiology, Wright State University, Dayton, Ohio
| | - Paul Nardelli
- Department of Neuroscience, Cell Biology, and Physiology, Wright State University, Dayton, Ohio
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia; and
| | - Robert E W Fyffe
- Department of Neuroscience, Cell Biology, and Physiology, Wright State University, Dayton, Ohio
| | - Thomas Burkholder
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia; and
| | - Timothy C Cope
- Department of Neuroscience, Cell Biology, and Physiology, Wright State University, Dayton, Ohio;
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia; and
- School of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia
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10
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Carrasco DI, Vincent JA, Cope TC. Distribution of TTX-sensitive voltage-gated sodium channels in primary sensory endings of mammalian muscle spindles. J Neurophysiol 2017; 117:1690-1701. [PMID: 28123009 DOI: 10.1152/jn.00889.2016] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 01/24/2017] [Accepted: 01/24/2017] [Indexed: 12/19/2022] Open
Abstract
Knowledge of the molecular mechanisms underlying signaling of mechanical stimuli by muscle spindles remains incomplete. In particular, the ionic conductances that sustain tonic firing during static muscle stretch are unknown. We hypothesized that tonic firing by spindle afferents depends on sodium persistent inward current (INaP) and tested for the necessary presence of the appropriate voltage-gated sodium (NaV) channels in primary sensory endings. The NaV1.6 isoform was selected for both its capacity to produce INaP and for its presence in other mechanosensors that fire tonically. The present study shows that NaV1.6 immunoreactivity (IR) is concentrated in heminodes, presumably where tonic firing is generated, and we were surprised to find NaV1.6 IR strongly expressed also in the sensory terminals, where mechanotransduction occurs. This spatial pattern of NaV1.6 IR distribution was consistent for three mammalian species (rat, cat, and mouse), as was tonic firing by primary spindle afferents. These findings meet some of the conditions needed to establish participation of INaP in tonic firing by primary sensory endings. The study was extended to two additional NaV isoforms, selected for their sensitivity to TTX, excluding TTX-resistant NaV channels, which alone are insufficient to support firing by primary spindle endings. Positive immunoreactivity was found for NaV1.1, predominantly in sensory terminals together with NaV1.6 and for NaV1.7, mainly in preterminal axons. Differential distribution in primary sensory endings suggests specialized roles for these three NaV isoforms in the process of mechanosensory signaling by muscle spindles.NEW & NOTEWORTHY The molecular mechanisms underlying mechanosensory signaling responsible for proprioceptive functions are not completely elucidated. This study provides the first evidence that voltage-gated sodium channels (NaVs) are expressed in the spindle primary sensory ending, where NaVs are found at every site involved in transduction or encoding of muscle stretch. We propose that NaVs contribute to multiple steps in sensory signaling by muscle spindles as it does in other types of slowly adapting sensory neurons.
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Affiliation(s)
- Dario I Carrasco
- School of Biological Science, Georgia Institute of Technology, Atlanta Georgia
| | - Jacob A Vincent
- School of Biological Science, Georgia Institute of Technology, Atlanta Georgia
| | - Timothy C Cope
- School of Biological Science, Georgia Institute of Technology, Atlanta Georgia; .,Biomedical Engineering, Georgia Institute of Technology, Atlanta Georgia; and
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11
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Affiliation(s)
- Peter J Shortland
- School of Science & Health, School of Medicine, Western Sydney University, Campbelltown, NSW, Australia
| | - David A Mahns
- School of Medicine, Western Sydney University, Campbelltown, NSW, Australia
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12
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Vincent JA, Wieczerzak KB, Gabriel HM, Nardelli P, Rich MM, Cope TC. A novel path to chronic proprioceptive disability with oxaliplatin: Distortion of sensory encoding. Neurobiol Dis 2016; 95:54-65. [PMID: 27397106 DOI: 10.1016/j.nbd.2016.07.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Revised: 06/06/2016] [Accepted: 07/03/2016] [Indexed: 02/08/2023] Open
Abstract
Persistent neurotoxic side effects of oxaliplatin (OX) chemotherapy, including sensory ataxia, limit the efficacy of treatment and significantly diminish patient quality of life. The common explanation for neurotoxicity is neuropathy, however the degree of neuropathy varies greatly among patients and appears insufficient in some cases to fully account for disability. We recently identified an additional mechanism that might contribute to sensory ataxia following OX treatment. In the present study, we tested whether that mechanism, selective modification of sensory signaling by muscle proprioceptors might result in behavioral deficits in rats. OX was administered once per week for seven weeks (cumulative dose i.p. 70mg/kg) to adult female Wistar rats. Throughout and for three weeks following treatment, behavioral analysis was performed daily on OX and sham control rats. Compared to controls, OX rats demonstrated errors in placing their hind feet securely and/or correctly during a horizontal ladder rung task. These behavioral deficits occurred together with modification of proprioceptor signaling that eliminated sensory encoding of static muscle position while having little effect on encoding of dynamic changes in muscle length. Selective inability to sustain repetitive firing in response to static muscle stretch led us to hypothesize that OX treatment impairs specific ionic currents, possibly the persistent inward Na currents (NaPIC) that are known to support repetitive firing during static stimulation in several neuron types, including the class of large diameter dorsal root ganglion cells that includes muscle proprioceptors. We tested this hypothesis by determining whether the chronic effects of OX on the firing behavior of muscle proprioceptors in vivo were mimicked by acute injection of NaPIC antagonists. Both riluzole and phenytoin, each having multiple drug actions but having only antagonist action on NaPIC in common, reproduced selective modification of proprioceptor signaling observed in OX rats. Taken together, these findings lead us to propose that OX chemotherapy contributes to movement disability by modifying sensory encoding, possibly via a chronic neurotoxic effect on NaPIC in the sensory terminals of muscle proprioceptors.
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Affiliation(s)
- Jacob A Vincent
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, OH 45435, United States
| | - Krystyna B Wieczerzak
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, OH 45435, United States
| | - Hanna M Gabriel
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, OH 45435, United States
| | - Paul Nardelli
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, OH 45435, United States; School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30318, United States
| | - Mark M Rich
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, OH 45435, United States
| | - Timothy C Cope
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, OH 45435, United States; School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30318, United States.
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