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Cooper AH, Barry AM, Chrysostomidou P, Lolignier R, Wang J, Redondo Canales M, Titterton HF, Bennett DL, Weir GA. Peripheral nerve injury results in a biased loss of sensory neuron subpopulations. Pain 2024:00006396-990000000-00668. [PMID: 39158319 DOI: 10.1097/j.pain.0000000000003321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Accepted: 05/25/2024] [Indexed: 08/20/2024]
Abstract
ABSTRACT There is a rich literature describing the loss of dorsal root ganglion (DRG) neurons following peripheral axotomy, but the vulnerability of discrete subpopulations has not yet been characterised. Furthermore, the extent or even presence of neuron loss following injury has recently been challenged. In this study, we have used a range of transgenic recombinase driver mouse lines to genetically label molecularly defined subpopulations of DRG neurons and track their survival following traumatic nerve injury. We find that spared nerve injury leads to a marked loss of cells containing DRG volume and a concomitant loss of small-diameter DRG neurons. Neuron loss occurs unequally across subpopulations and is particularly prevalent in nonpeptidergic nociceptors, marked by expression of Mrgprd. We show that this subpopulation is almost entirely lost following spared nerve injury and severely depleted (by roughly 50%) following sciatic nerve crush. Finally, we used an in vitro model of DRG neuron survival to demonstrate that nonpeptidergic nociceptor loss is likely dependent on the absence of neurotrophic support. Together, these results profile the extent to which DRG neuron subpopulations can survive axotomy, with implications for our understanding of nerve injury-induced plasticity and pain.
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Affiliation(s)
- Andrew H Cooper
- School of Psychology and Neuroscience, University of Glasgow, Glasgow, United Kingdom
| | - Allison M Barry
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | | | - Romane Lolignier
- School of Psychology and Neuroscience, University of Glasgow, Glasgow, United Kingdom
| | - Jinyi Wang
- School of Psychology and Neuroscience, University of Glasgow, Glasgow, United Kingdom
| | | | - Heather F Titterton
- School of Psychology and Neuroscience, University of Glasgow, Glasgow, United Kingdom
| | - David L Bennett
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Greg A Weir
- School of Psychology and Neuroscience, University of Glasgow, Glasgow, United Kingdom
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2
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Mizumura K, Taguchi T. Neurochemical mechanism of muscular pain: Insight from the study on delayed onset muscle soreness. J Physiol Sci 2024; 74:4. [PMID: 38267849 PMCID: PMC10809664 DOI: 10.1186/s12576-023-00896-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2023] [Accepted: 12/22/2023] [Indexed: 01/26/2024]
Abstract
We reviewed fundamental studies on muscular pain, encompassing the characteristics of primary afferent fibers and neurons, spinal and thalamic projections, several muscular pain models, and possible neurochemical mechanisms of muscle pain. Most parts of this review were based on data obtained from animal experiments, and some researches on humans were also introduced. We focused on delayed-onset muscle soreness (DOMS) induced by lengthening contractions (LC), suitable for studying myofascial pain syndromes. The muscular mechanical withdrawal threshold (MMWT) decreased 1-3 days after LC in rats. Changing the speed and range of stretching showed that muscle injury seldom occurred, except in extreme conditions, and that DOMS occurred in parameters without muscle damage. The B2 bradykinin receptor-nerve growth factor (NGF) route and COX-2-glial cell line-derived neurotrophic factor (GDNF) route were involved in the development of DOMS. The interactions between these routes occurred at two levels. A repeated-bout effect was observed in MMWT and NGF upregulation, and this study showed that adaptation possibly occurred before B2 bradykinin receptor activation. We have also briefly discussed the prevention and treatment of DOMS.
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Affiliation(s)
- Kazue Mizumura
- Nagoya University, Nagoya, 464-8601, Japan.
- Department of Physiology, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan.
| | - Toru Taguchi
- Department of Physical Therapy, Faculty of Rehabilitation, Niigata University of Health and Welfare, Niigata, 950-3198, Japan
- Institute for Human Movement and Medical Sciences (IHMMS), Niigata University of Health and Welfare, Niigata, 950-3198, Japan
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3
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Tran H, Feng Y, Chao D, Liu QS, Hogan QH, Pan B. Descending mechanism by which medial prefrontal cortex endocannabinoid signaling controls the development of neuropathic pain and neuronal activity of dorsal root ganglion. Pain 2024; 165:102-114. [PMID: 37463226 PMCID: PMC10787817 DOI: 10.1097/j.pain.0000000000002992] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Accepted: 06/05/2023] [Indexed: 07/20/2023]
Abstract
ABSTRACT Although regulation of nociceptive processes in the dorsal horn by deep brain structures has long been established, the role of cortical networks in pain regulation is minimally explored. The medial prefrontal cortex (mPFC) is a key brain area in pain processing that receives ascending nociceptive input and exerts top-down control of pain sensation. We have shown critical changes in mPFC synaptic function during neuropathic pain, controlled by endocannabinoid (eCB) signaling. This study tests whether mPFC eCB signaling modulates neuropathic pain through descending control. Intra-mPFC injection of cannabinoid receptor type 1 (CB1R) agonist WIN-55,212-2 (WIN) in the chronic phase transiently alleviates the pain-like behaviors in spared nerve injury (SNI) rats. By contrast, intra-mPFC injection of CB1R antagonist AM4113 in the early phase of neuropathic pain reduces the development of pain-like behaviors in the chronic phase. Spared nerve injury reduced the mechanical threshold to induce action potential firing of dorsal horn wide-dynamic-range neurons, but this was reversed in rats by WIN in the chronic phase of SNI and by mPFC injection of AM4113 in the early phase of SNI. Elevated dorsal root ganglion neuronal activity after injury was also diminished in rats by mPFC injection of AM4113, potentially by reducing antidromic activity and subsequent neuronal inflammation. These findings suggest that depending on the phase of the pain condition, both blocking and activating CB1 receptors in the mPFC can regulate descending control of pain and affect both dorsal horn neurons and peripheral sensory neurons, contributing to changes in pain sensitivity.
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Affiliation(s)
- Hai Tran
- Department of Anesthesiology, Medical College of Wisconsin, 8701 W Watertown Plank Rd, Milwaukee, WI 53226
| | - Yin Feng
- Department of Anesthesiology, Medical College of Wisconsin, 8701 W Watertown Plank Rd, Milwaukee, WI 53226
| | - Dongman Chao
- Department of Anesthesiology, Medical College of Wisconsin, 8701 W Watertown Plank Rd, Milwaukee, WI 53226
| | - Qing-song Liu
- Department of Pharmacology & Toxicology, Medical College of Wisconsin, 8701 W Watertown Plank Rd, Milwaukee, WI 53226
| | - Quinn H. Hogan
- Department of Anesthesiology, Medical College of Wisconsin, 8701 W Watertown Plank Rd, Milwaukee, WI 53226
| | - Bin Pan
- Department of Anesthesiology, Medical College of Wisconsin, 8701 W Watertown Plank Rd, Milwaukee, WI 53226
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Kongsui R, Surapinit S, Promsrisuk T, Thongrong S. Pinostrobin from Boesenbergia rotunda attenuates oxidative stress and promotes functional recovery in rat model of sciatic nerve crush injury. Braz J Med Biol Res 2023; 56:e12578. [PMID: 36856256 PMCID: PMC9974073 DOI: 10.1590/1414-431x2023e12578] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 01/19/2023] [Indexed: 03/02/2023] Open
Abstract
Oxidative stress plays a role in the delay of peripheral nerve regeneration after injury. The accumulation of free radicals results in nerve tissue damage and dorsal root ganglion (DRG) neuronal death. Pinostrobin (PB) is one of the bioflavonoids from Boesenbergia rotunda and has been reported to possess antioxidant capacity and numerous pharmacological activities. Therefore, this study aimed to investigate the effects of PB on peripheral nerve regeneration after injury. Male Wistar rats were randomly divided into 5 groups including control, sham, sciatic nerve crush injury (SNC), SNC + 20 mg/kg PB, and SNC + 40 mg/kg PB. Nerve functional recovery was observed every 7 days. At the end of the study, the sciatic nerve and the DRG were collected for histological and biochemical analyses. PB treatment at doses of 20 and 40 mg/kg reduced oxidative stress by up-regulating endogenous glutathione. The reduced oxidative stress in PB-treated rats resulted in increased axon diameters, greater number of DRG neurons, and p-ERK1/2 expression in addition to faster functional recovery within 4 weeks compared to untreated SNC rats. The results indicated that PB diminished the oxidative stress-induced nerve injury. These effects should be considered in the treatment of peripheral nerve injury.
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Affiliation(s)
- R. Kongsui
- Division of Physiology, School of Medical Sciences, University of Phayao, Phayao, Thailand
- The Unit of Excellence in Translational Neurosciences Initiative, University of Phayao, Phayao, Thailand
| | - S. Surapinit
- The Unit of Excellence in Translational Neurosciences Initiative, University of Phayao, Phayao, Thailand
- Department of Medical Technology, School of Allied Health Sciences, University of Phayao, Phayao, Thailand
| | - T. Promsrisuk
- Division of Physiology, School of Medical Sciences, University of Phayao, Phayao, Thailand
| | - S. Thongrong
- The Unit of Excellence in Translational Neurosciences Initiative, University of Phayao, Phayao, Thailand
- Division of Anatomy, School of Medical Sciences, University of Phayao, Phayao, Thailand
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Arbat-Plana A, Bolívar S, Navarro X, Udina E, Alvarez FJ. Massive Loss of Proprioceptive Ia Synapses in Rat Spinal Motoneurons after Nerve Crush Injuries in the Postnatal Period. eNeuro 2023; 10:ENEURO.0436-22.2023. [PMID: 36759186 PMCID: PMC9948128 DOI: 10.1523/eneuro.0436-22.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 12/15/2022] [Accepted: 01/26/2023] [Indexed: 02/11/2023] Open
Abstract
Peripheral nerve injuries (PNIs) induce the retraction from the ventral horn of the synaptic collaterals of Ia afferents injured in the nerve, effectively removing Ia synapses from α-motoneurons. The loss of Ia input impairs functional recovery and could explain, in part, better recovery after PNIs with better Ia synaptic preservation. Synaptic losses correlate with injury severity, speed, and efficiency of muscle reinnervation and requires ventral microglia activation. It is unknown whether this plasticity is age dependent. In neonates, axotomized motoneurons and sensory neurons undergo apoptosis, but after postnatal day 10 most survive. The goal of this study was to analyze vesicular glutamate transporter 1 (VGluT1)-labeled Ia synapses (which also include II afferents) after nerve crush in 10 day old rats, a PNI causing little Ia/II synapse loss in adult rats. We confirmed fast and efficient reinnervation of leg muscles; however, a massive number of VGluT1/Ia/II synapses were permanently lost. This synapse loss was similar to that after more severe nerve injuries involving full transection in adults. In adults, disappearance of ventrally directed Ia/II collaterals targeting α-motoneurons was associated with a prolonged microglia reaction and a CCR2 mechanism that included infiltration of CCR2 blood immune cells. By contrast, microgliosis after P10 injuries was fast, resolved in about a week, and there was no evidence of peripheral immune cell infiltration. We conclude that VGluT1/Ia/II synapse loss in young animals differs in mechanism, perhaps associated with higher microglia synaptic pruning activity at this age and results in larger losses after milder nerve injuries.
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Affiliation(s)
- Ariadna Arbat-Plana
- Department of Cell Biology, Physiology and Immunology, Institute of Neurosciences, Universitat Autònoma de Barcelona, 08028 Barcelona, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), 08193 Bellaterra, Spain
- Department of Physiology, Emory University, Atlanta, Georgia 30322
| | - Sara Bolívar
- Department of Cell Biology, Physiology and Immunology, Institute of Neurosciences, Universitat Autònoma de Barcelona, 08028 Barcelona, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), 08193 Bellaterra, Spain
- Department of Physiology, Emory University, Atlanta, Georgia 30322
| | - Xavier Navarro
- Department of Cell Biology, Physiology and Immunology, Institute of Neurosciences, Universitat Autònoma de Barcelona, 08028 Barcelona, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), 08193 Bellaterra, Spain
| | - Esther Udina
- Department of Cell Biology, Physiology and Immunology, Institute of Neurosciences, Universitat Autònoma de Barcelona, 08028 Barcelona, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), 08193 Bellaterra, Spain
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Chao D, Mecca CM, Yu G, Segel I, Gold MS, Hogan QH, Pan B. Dorsal root ganglion stimulation of injured sensory neurons in rats rapidly eliminates their spontaneous activity and relieves spontaneous pain. Pain 2021; 162:2917-2932. [PMID: 33990112 PMCID: PMC8486885 DOI: 10.1097/j.pain.0000000000002284] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Accepted: 03/23/2021] [Indexed: 11/26/2022]
Abstract
ABSTRACT Dorsal root ganglion field stimulation (GFS) relieves evoked and spontaneous neuropathic pain by use-dependent blockade of impulse trains through the sensory neuron T-junction, which becomes complete within less than 1 minute for C-type units, also with partial blockade of Aδ units. We used this tool in the spinal nerve ligation (SNL) rat model to selectively block sensory neuron spontaneous activity (SA) of axotomized neurons at the fifth lumbar (L5) level vs blockade of units at the L4 level that remain uninjured but exposed to inflammation. In vivo dorsal root single-unit recordings after SNL showed increased SA in L5 units but not L4 units. Ganglion field stimulation blocked this SA. Ganglion field stimulation delivered at the L5 dorsal root ganglion blocked mechanical hyperalgesia behavior, mechanical allodynia, and ongoing spontaneous pain indicated by conditioned place preference, whereas GFS at L4 blocked evoked pain behavior but not spontaneous pain. In vivo single-unit recordings of spinal cord dorsal horn (DH) wide-dynamic-range neurons showed elevated SA after SNL, which was reduced by GFS at the L5 level but not by GFS at the L4 level. In addition, L5 GFS, but not L4 GFS, increased mechanical threshold of DH units during cutaneous mechanical stimulation, while L5 GFS exceeded L4 GFS in reducing evoked firing rates. Our results indicate that SA in injured neurons supports increased firing of DH wide-dynamic-range neurons, contributing to hyperalgesia, allodynia, and ongoing pain. Ganglion field stimulation analgesic effects after nerve injury are at least partly attributable to blocking propagation of this SA.
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Affiliation(s)
- Dongman Chao
- Department of Anesthesiology, Medical College of Wisconsin, 8701 W Watertown Plank Rd, Milwaukee, WI 53226
| | - Christina M. Mecca
- Department of Anesthesiology, Medical College of Wisconsin, 8701 W Watertown Plank Rd, Milwaukee, WI 53226
| | - Guoliang Yu
- Department of Anesthesiology, Medical College of Wisconsin, 8701 W Watertown Plank Rd, Milwaukee, WI 53226
| | - Ian Segel
- Department of Anesthesiology, Medical College of Wisconsin, 8701 W Watertown Plank Rd, Milwaukee, WI 53226
| | - Michael S. Gold
- Department of Neurobiology, University of Pittsburgh, 3500 Terrace Street Rm E1440 BST, Pittsburgh, PA 15213
| | - Quinn H. Hogan
- Department of Anesthesiology, Medical College of Wisconsin, 8701 W Watertown Plank Rd, Milwaukee, WI 53226
| | - Bin Pan
- Department of Anesthesiology, Medical College of Wisconsin, 8701 W Watertown Plank Rd, Milwaukee, WI 53226
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Szeredi ID, Jancsó G, Oszlács O, Sántha P. Prior perineural or neonatal treatment with capsaicin does not alter the development of spinal microgliosis induced by peripheral nerve injury. Cell Tissue Res 2021; 383:677-692. [PMID: 32960358 PMCID: PMC7904541 DOI: 10.1007/s00441-020-03285-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Accepted: 08/14/2020] [Indexed: 11/28/2022]
Abstract
Peripheral nerve injury is associated with spinal microgliosis which plays a pivotal role in the development of neuropathic pain behavior. Several agents of primary afferent origin causing the microglial reaction have been identified, but the type(s) of primary afferents that release these mediators are still unclear. In this study, specific labeling of C-fiber spinal afferents by lectin histochemistry and selective chemodenervation by capsaicin were applied to identify the type(s) of primary afferents involved in the microglial response. Comparative quantitative morphometric evaluation of the microglial reaction in central projection territories of intact and injured peripheral nerves in the superficial (laminae I and II) and deep (laminae III and IV) spinal dorsal horn revealed a significant, about three-fold increase in microglial density after transection of the sciatic or the saphenous nerve. Prior perineural treatment of these nerves with capsaicin, resulting in a selective defunctionalization of C-fiber afferent fibers failed to affect spinal microgliosis. Similarly, peripheral nerve injury-induced increase in microglial density was unaffected in rats treated neonatally with capsaicin known to result in a near-total loss of C-fiber dorsal root fibers. Perineural treatment with capsaicin per se did not evoke a significant increase in microglial density. These observations indicate that injury-induced spinal microgliosis may be attributed to phenotypic changes in injured myelinated primary afferent neurons, whereas the contribution of C-fiber primary sensory neurons to this neuroimmune response is negligible. Spinal myelinated primary afferents may play a hitherto unrecognized role in regulation of neuroimmune and perisynaptic microenvironments of the spinal dorsal horn.
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Affiliation(s)
- Ivett Dorina Szeredi
- Department of Physiology, University of Szeged, Dóm tér 10, Szeged, H-6720, Hungary
| | - Gábor Jancsó
- Department of Physiology, University of Szeged, Dóm tér 10, Szeged, H-6720, Hungary
| | - Orsolya Oszlács
- Department of Physiology, University of Szeged, Dóm tér 10, Szeged, H-6720, Hungary
| | - Péter Sántha
- Department of Physiology, University of Szeged, Dóm tér 10, Szeged, H-6720, Hungary.
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8
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Wang X, Ma W, Wang T, Yang J, Wu Z, Liu K, Dai Y, Zang C, Liu W, Liu J, Liang Y, Guo J, Li L. BDNF-TrkB and proBDNF-p75NTR/Sortilin Signaling Pathways are Involved in Mitochondria-Mediated Neuronal Apoptosis in Dorsal Root Ganglia after Sciatic Nerve Transection. CNS & NEUROLOGICAL DISORDERS-DRUG TARGETS 2020; 19:66-82. [PMID: 31957620 DOI: 10.2174/1871527319666200117110056] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 12/12/2019] [Accepted: 12/24/2019] [Indexed: 02/07/2023]
Abstract
Background:
Brain-Derived Neurotrophic Factor (BDNF) plays critical roles during development
of the central and peripheral nervous systems, as well as in neuronal survival after injury.
Although proBDNF induces neuronal apoptosis after injury in vivo, whether it can also act as a death
factor in vitro and in vivo under physiological conditions and after nerve injury, as well as its mechanism
of inducing apoptosis, is still unclear.
Objective:
In this study, we investigated the mechanisms by which proBDNF causes apoptosis in sensory
neurons and Satellite Glial Cells (SGCs) in Dorsal Root Ganglia (DRG) After Sciatic Nerve
Transection (SNT).
Methods:
SGCs cultures were prepared and a scratch model was established to analyze the role of
proBDNF in sensory neurons and SGCs in DRG following SNT. Following treatment with proBDNF
antiserum, TUNEL and immunohistochemistry staining were used to detect the expression of Glial
Fibrillary Acidic Protein (GFAP) and Calcitonin Gene-Related Peptide (CGRP) in DRG tissue; immunocytochemistry
and Cell Counting Kit-8 (CCK8) assay were used to detect GFAP expression and
cell viability of SGCs, respectively. RT-qPCR, western blot, and ELISA were used to measure mRNA
and protein levels, respectively, of key factors in BDNF-TrkB, proBDNF-p75NTR/sortilin, and apoptosis
signaling pathways.
Results:
proBDNF induced mitochondrial apoptosis of SGCs and neurons by modulating BDNF-TrkB
and proBDNF-p75NTR/sortilin signaling pathways. In addition, neuroprotection was achieved by inhibiting
the biological activity of endogenous proBDNF protein by injection of anti-proBDNF serum. Furthermore,
the anti-proBDNF serum inhibited the activation of SGCs and promoted their proliferation.
Conclusion:
proBDNF induced apoptosis in SGCs and sensory neurons in DRG following SNT. The
proBDNF signaling pathway is a potential novel therapeutic target for reducing sensory neuron and
SGCs loss following peripheral nerve injury.
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Affiliation(s)
- Xianbin Wang
- Institute of Neuroscience, Kunming Medical University, Kunming, Yunnan 650500, China
| | - Wei Ma
- Institute of Neuroscience, Kunming Medical University, Kunming, Yunnan 650500, China
| | - Tongtong Wang
- Institute of Neuroscience, Kunming Medical University, Kunming, Yunnan 650500, China
| | - Jinwei Yang
- Second Department of General Surgery, First People’s Hospital of Yunnan Province, Kunming, Yunnan 650032, China
| | - Zhen Wu
- Second Department of General Surgery, First People’s Hospital of Yunnan Province, Kunming, Yunnan 650032, China
| | - Kuangpin Liu
- Institute of Neuroscience, Kunming Medical University, Kunming, Yunnan 650500, China
| | - Yunfei Dai
- Institute of Neuroscience, Kunming Medical University, Kunming, Yunnan 650500, China
| | - Chenghao Zang
- Second Department of General Surgery, First People’s Hospital of Yunnan Province, Kunming, Yunnan 650032, China
| | - Wei Liu
- Institute of Neuroscience, Kunming Medical University, Kunming, Yunnan 650500, China
| | - Jie Liu
- Institute of Neuroscience, Kunming Medical University, Kunming, Yunnan 650500, China
| | - Yu Liang
- Institute of Neuroscience, Kunming Medical University, Kunming, Yunnan 650500, China
| | - Jianhui Guo
- Second Department of General Surgery, First People’s Hospital of Yunnan Province, Kunming, Yunnan 650032, China
| | - Liyan Li
- Institute of Neuroscience, Kunming Medical University, Kunming, Yunnan 650500, China
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9
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Fang Y, Zhu J, Duan W, Xie Y, Ma C. Inhibition of Muscular Nociceptive Afferents via the Activation of Cutaneous Nociceptors in a Rat Model of Inflammatory Muscle Pain. Neurosci Bull 2019; 36:1-10. [PMID: 31230211 DOI: 10.1007/s12264-019-00406-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Accepted: 01/13/2019] [Indexed: 10/26/2022] Open
Abstract
Topical irritants such as capsaicin (CAP), peppermint oil (PO), and mustard oil (MO) are effective in relieving inflammatory muscle pain. We investigated the effects of topical irritants in a rat model of inflammatory muscle pain produced by injecting complete Freund's adjuvant (CFA) into the tibialis anterior muscle. CFA-induced mechanical hypersensitivity and the spontaneous activity of muscular nociceptive afferents, and decreased weight-bearing of the hindlimb were relieved by topical application of CAP, PO, or MO on the skin overlying the inflamed muscle. The effects of topical irritants were abolished when applied to the skin on the ipsilateral plantar region or on the contralateral leg, or when the relevant cutaneous nerve or dorsal root was transected. Our results demonstrated that topical irritants may alleviate inflammatory muscle pain via activating cutaneous nociceptors and subsequently inhibiting the abnormal activity of muscular nociceptive neurons.
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Affiliation(s)
- Yehong Fang
- Institute of Basic Medical Sciences, Department of Human Anatomy, Histology and Embryology, Neuroscience Center, Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing, 100005, China.,Joint Laboratory of Anesthesia and Pain, Peking Union Medical College, Beijing, 100730, China
| | - Jie Zhu
- Institute of Basic Medical Sciences, Department of Human Anatomy, Histology and Embryology, Neuroscience Center, Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing, 100005, China.,Department of Radiation Oncology, Sichuan Cancer Hospital and Institute, Sichuan Cancer Center, School of Medicine, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Wanru Duan
- Department of Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, 100053, China
| | - Yikuan Xie
- Institute of Basic Medical Sciences, Department of Human Anatomy, Histology and Embryology, Neuroscience Center, Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing, 100005, China
| | - Chao Ma
- Institute of Basic Medical Sciences, Department of Human Anatomy, Histology and Embryology, Neuroscience Center, Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing, 100005, China.
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10
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Wiberg R, Novikova LN, Kingham PJ. Evaluation of apoptotic pathways in dorsal root ganglion neurons following peripheral nerve injury. Neuroreport 2019; 29:779-785. [PMID: 29659443 DOI: 10.1097/wnr.0000000000001031] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Peripheral nerve injuries induce significant sensory neuronal cell death in the dorsal root ganglia (DRG); however, the role of specific apoptotic pathways is still unclear. In this study, we performed peripheral nerve transection on adult rats, after which the corresponding DRGs were harvested at 7, 14, and 28 days after injury for subsequent molecular analyses with quantitative reverse transcription-PCR, western blotting, and immunohistochemistry. Nerve injury led to increased levels of caspase-3 mRNA and active caspase-3 protein in the DRG. Increased expression of caspase-8, caspase-12, caspase-7, and calpain suggested that both the extrinsic and the endoplasmic reticulum (ER) stress-mediated apoptotic pathways were activated. Phosphorylation of protein kinase R-like ER kinase further implied the involvement of ER-stress in the DRG. Phosphorylated protein kinase R-like ER kinase was most commonly associated with isolectin B4 (IB4)-positive neurons in the DRG and this may provide an explanation for the increased susceptibility of these neurons to die following nerve injury, likely in part because of an activation of the ER-stress response.
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Affiliation(s)
- Rebecca Wiberg
- Department of Integrative Medical Biology, Section of Anatomy.,Department of Surgical & Perioperative Sciences, Section of Hand and Plastic Surgery, Umeå University, Umeå, Sweden
| | | | - Paul J Kingham
- Department of Integrative Medical Biology, Section of Anatomy
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11
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Devor M. Rethinking the causes of pain in herpes zoster and postherpetic neuralgia: the ectopic pacemaker hypothesis. Pain Rep 2018; 3:e702. [PMID: 30706041 PMCID: PMC6344138 DOI: 10.1097/pr9.0000000000000702] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 10/10/2018] [Indexed: 01/29/2023] Open
Abstract
INTRODUCTION Pain in herpes zoster (HZ) and postherpetic neuralgia (PHN) is traditionally explained in terms of 2 processes: irritable nociceptors in the rash-inflamed skin and, later, deafferentation due to destruction of sensory neurons in one virally infected dorsal root ganglion. OBJECTIVES AND METHODS Consideration of the evidence supporting this explanation in light of contemporary understanding of the pain system finds it wanting. An alternative hypothesis is proposed as a replacement. RESULTS This model, the ectopic pacemaker hypothesis of HZ and PHN, proposes that pain in both conditions is driven by hyperexcitable ectopic pacemaker sites at various locations in primary sensory neurons affected by the causative varicella zoster virus infection. This peripheral input is exacerbated by central sensitization induced and maintained by the ectopic activity. CONCLUSIONS The shift in perspective regarding the pain mechanism in HZ/PHN has specific implications for clinical management.
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Affiliation(s)
- Marshall Devor
- Department of Cell and Developmental Biology, Institute of Life Sciences, and Center for Research on Pain, The Hebrew University of Jerusalem, Jerusalem, Israel
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12
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Marler TL, Wright AB, Elmslie KL, Heier AK, Remily E, Kim-Han JS, Ramachandra R, Elmslie KS. Na V1.9 channels in muscle afferent neurons and axons. J Neurophysiol 2018; 120:1032-1044. [PMID: 29847236 DOI: 10.1152/jn.00573.2017] [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] [Indexed: 12/15/2022] Open
Abstract
The exercise pressor reflex (EPR) is activated by muscle contractions to increase heart rate and blood pressure during exercise. While this reflex is beneficial in healthy individuals, the reflex activity is exaggerated in patients with cardiovascular disease, which is associated with increased mortality. Group III and IV afferents mediate the EPR and have been shown to express both tetrodotoxin-sensitive (TTX-S, NaV1.6, and NaV1.7) and -resistant (TTX-R, NaV1.8, and NaV1.9) voltage-gated sodium (NaV) channels, but NaV1.9 current has not yet been demonstrated. Using a F--containing internal solution, we found a NaV current in muscle afferent neurons that activates at around -70 mV with slow activation and inactivation kinetics, as expected from NaV1.9 current. However, this current ran down with time, which resulted, at least in part, from increased steady-state inactivation since it was slowed by both holding potential hyperpolarization and a depolarized shift of the gating properties. We further show that, following NaV1.9 current rundown (internal F-), application of the NaV1.8 channel blocker A803467 inhibited significantly more TTX-R current than we had previously observed (internal Cl-), which suggests that NaV1.9 current did not rundown with that internal solution. Using immunohistochemistry, we found that the majority of group IV somata and axons were NaV1.9 positive. The majority of small diameter myelinated afferent somata (putative group III) were also NaV1.9 positive, but myelinated muscle afferent axons were rarely labeled. The presence of NaV1.9 channels in muscle afferents supports a role for these channels in activation and maintenance of the EPR. NEW & NOTEWORTHY Small diameter muscle afferents signal pain and muscle activity levels. The muscle activity signals drive the cardiovascular system to increase muscle blood flow, but these signals can become exaggerated in cardiovascular disease to exacerbate cardiac damage. The voltage-dependent sodium channel NaV1.9 plays a unique role in controlling afferent excitability. We show that NaV1.9 channels are expressed in muscle afferents, which supports these channels as a target for drug development to control hyperactivity of these neurons.
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Affiliation(s)
- Tyler L Marler
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A. T. Still University of Health Sciences, Kirksville, Missouri
| | - Andrew B Wright
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A. T. Still University of Health Sciences, Kirksville, Missouri
| | - Kristina L Elmslie
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A. T. Still University of Health Sciences, Kirksville, Missouri
| | - Ankeeta K Heier
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A. T. Still University of Health Sciences, Kirksville, Missouri
| | - Ethan Remily
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A. T. Still University of Health Sciences, Kirksville, Missouri
| | - Jeong Sook Kim-Han
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A. T. Still University of Health Sciences, Kirksville, Missouri
| | - Renuka Ramachandra
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A. T. Still University of Health Sciences, Kirksville, Missouri
| | - Keith S Elmslie
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A. T. Still University of Health Sciences, Kirksville, Missouri
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Tode J, Kirillova-Woytke I, Rausch VH, Baron R, Jänig W. Mechano- and thermosensitivity of injured muscle afferents 20 to 80 days after nerve injury. J Neurophysiol 2018; 119:1889-1901. [PMID: 29465328 DOI: 10.1152/jn.00894.2017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Chronic injury of limb nerves leading to neuropathic pain affects deep somatic nerves. Here the functional properties of injured afferent fibers in the lateral gastrocnemius-soleus nerve were investigated 20 and 80 days after suturing the central stump of this muscle nerve to the distal stump of the sural nerve in anesthetized rats. Neurophysiological recordings were made from afferent axons identified in either the sciatic nerve (87 A-, 63 C-fibers) or the dorsal root L4/L5 (52 A-, 26 C-fibers) by electrical stimulation of the injured nerve. About 70% of the functionally identified A-fibers had regenerated into skin by 80 days after nerve suture; the remaining A-fibers could be activated only from the injured nerve. In contrast, 93% of the functionally identified C-fibers could only be activated from the injured sural nerve after 80 days. Nearly half of the injured A- (45%) and C-fibers (44%) exhibited ongoing and/or mechanically or thermally evoked activity. Because ~50% of the A- and C-fibers are somatomotor or sympathetic postganglionic axons, respectively, probably all injured muscle afferent A- and C-fibers developed ectopic activity. Ongoing activity was present in 17% of the A- and 46% of the C-fibers. Mechanosensitivity was present in most injured A- (99%) and C-fibers (85%), whereas thermosensitivity was more common in C-fibers (cold 46%, heat 47%) than in A-fibers (cold 18%, heat 12%). Practically all thermosensitive A-fibers and C-fibers were also mechanosensitive. Thus, unlike cutaneous axons, almost all A- and C-fibers afferents in injured muscle nerves demonstrate ectopic activity, even chronically after nerve injury. NEW & NOTEWORTHY After chronic injury of a muscle nerve, allowing the nerve fibers to regenerate to the target tissue, 1) most afferent A-fibers are mechanosensitive and regenerate to the target tissue; 2) ectopic ongoing activity, cold sensitivity, and heat sensitivity significantly decrease with time after injury in A-afferents; 3) most afferent C-fibers do not regenerate to the target tissue; and 4) injured C-afferents maintain the patterns of ectopic discharge properties they already show soon after nerve injury.
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Affiliation(s)
- Jan Tode
- Physiologisches Institut, Christian-Albrechts-Universität zu Kiel, Kiel , Germany
| | | | - Vanessa H Rausch
- Physiologisches Institut, Christian-Albrechts-Universität zu Kiel, Kiel , Germany
| | - Ralf Baron
- Division of Neurological Pain Research and Therapy, Department of Neurology, Christian-Albrechts-Universität zu Kiel, Kiel , Germany
| | - Wilfrid Jänig
- Physiologisches Institut, Christian-Albrechts-Universität zu Kiel, Kiel , Germany
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14
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Burke D, Halmagyi GM. Normal tendon reflexes despite absent sensory nerve action potentials in CANVAS: a neurophysiological study. J Neurol Sci 2018; 387:75-79. [PMID: 29571876 DOI: 10.1016/j.jns.2018.01.023] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2017] [Revised: 01/04/2018] [Accepted: 01/20/2018] [Indexed: 01/20/2023]
Abstract
CANVAS is a recently defined progressive ataxic syndrome with impairment of vestibular, somatosensory and cerebellar function due to atrophic degeneration of dorsal root ganglia and dorsal columns, of cranial nerve somatosensory ganglia, of vestibular ganglia and vestibular nerves and of cerebellar Purkinje cells. While all patients eventually develop sensory impairment in a non-length dependent pattern and lose sensory nerve action potentials, some retain their tendon reflexes. Here we study 5 CANVAS patients with absent sensory nerve action potentials but intact, even brisk Achilles tendon reflexes and, in 4, preserved H reflexes in the upper and lower limbs. These findings imply that dorsal root ganglion neurons subserving cutaneous afferents more vulnerable than those subserving muscle afferents. Our findings have a clinical message: preservation of the Achilles tendon jerk does not exclude a large fibre peripheral neuronopathy.
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Affiliation(s)
- David Burke
- Department of Neurology, Royal Prince Alfred Hospital and the University of Sydney, Australia
| | - G Michael Halmagyi
- Department of Neurology, Royal Prince Alfred Hospital and the University of Sydney, Australia.
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15
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N-Acetylcysteine Prevents Retrograde Motor Neuron Death after Neonatal Peripheral Nerve Injury. Plast Reconstr Surg 2017; 139:1105e-1115e. [DOI: 10.1097/prs.0000000000003257] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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16
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Hu G, Huang K, Hu Y, Du G, Xue Z, Zhu X, Fan G. Single-cell RNA-seq reveals distinct injury responses in different types of DRG sensory neurons. Sci Rep 2016; 6:31851. [PMID: 27558660 PMCID: PMC4997251 DOI: 10.1038/srep31851] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 07/28/2016] [Indexed: 01/02/2023] Open
Abstract
Peripheral nerve injury leads to various injury-induced responses in sensory neurons including physiological pain, neuronal cell death, and nerve regeneration. In this study, we performed single-cell RNA-sequencing (scRNA-seq) analysis of mouse nonpeptidergic nociceptors (NP), peptidergic nociceptors (PEP), and large myelinated sensory neurons (LM) under both control and injury conditions at 3 days after sciatic nerve transection (SNT). After performing principle component and weighted gene co-expression network analysis, we categorized dorsal root ganglion (DRG) neurons into different subtypes and discovered co-regulated injury-response genes including novel regeneration associated genes (RAGs) in association with neuronal development, protein translation and cytoplasm transportation. In addition, we found significant up-regulation of the genes associated with cell death such as Pdcd2 in a subset of NP neurons after axotomy, implicating their actions in neuronal cell death upon nerve injury. Our study revealed the distinctive and sustained heterogeneity of transcriptomic responses to injury at single neuron level, implicating the involvement of different gene regulatory networks in nerve regeneration, neuronal cell death and neuropathy in different population of DRG neurons.
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Affiliation(s)
- Ganlu Hu
- School of Life Sciences and Technology, Tongji University, Shanghai 200092, China.,Department of Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles CA 90095, USA.,Translational Center for Stem Cell Research, Tongji Hospital, Department of Regenerative Medicine, Tongji University School of Medicine, Shanghai 20065, China
| | - Kevin Huang
- Department of Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles CA 90095, USA
| | - Youjin Hu
- Department of Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles CA 90095, USA.,Translational Center for Stem Cell Research, Tongji Hospital, Department of Regenerative Medicine, Tongji University School of Medicine, Shanghai 20065, China
| | - Guizhen Du
- Department of Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles CA 90095, USA
| | - Zhigang Xue
- Translational Center for Stem Cell Research, Tongji Hospital, Department of Regenerative Medicine, Tongji University School of Medicine, Shanghai 20065, China
| | - Xianmin Zhu
- School of Life Sciences and Technology, Tongji University, Shanghai 200092, China.,Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai 200433, China
| | - Guoping Fan
- School of Life Sciences and Technology, Tongji University, Shanghai 200092, China.,Department of Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles CA 90095, USA.,Wuxi Medical School, Jiangnan University, Wuxi City, Jiangsu Province, China
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17
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He B, Fang P, Guo L, Shi M, Zhu Y, Xu B, Bo P, Zhang Z. Beneficial effects of neuropeptide galanin on reinstatement of exercise-induced somatic and psychological trauma. J Neurosci Res 2016; 95:1036-1043. [DOI: 10.1002/jnr.23869] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2016] [Revised: 07/01/2016] [Accepted: 07/13/2016] [Indexed: 12/31/2022]
Affiliation(s)
- Biao He
- Key Laboratory of Adolescent Health Assessment and Exercise Intervention Ministry of Education, School of Physical Education and Health Care, East China Normal University; Shanghai China
| | - Penghua Fang
- Key Laboratory of Gerontal Medicine, Medical College, Yangzhou University; Yangzhou Jiangsu China
| | - Lili Guo
- Key Laboratory of Gerontal Medicine, Medical College, Yangzhou University; Yangzhou Jiangsu China
| | - Mingyi Shi
- Key Laboratory of Gerontal Medicine, Medical College, Yangzhou University; Yangzhou Jiangsu China
| | - Yan Zhu
- Department of Endocrinology; Clinical Medical College, Yangzhou University; Yangzhou Jiangsu China
| | - Bo Xu
- Key Laboratory of Adolescent Health Assessment and Exercise Intervention Ministry of Education, School of Physical Education and Health Care, East China Normal University; Shanghai China
| | - Ping Bo
- Key Laboratory of Gerontal Medicine, Medical College, Yangzhou University; Yangzhou Jiangsu China
- Department of Endocrinology; Clinical Medical College, Yangzhou University; Yangzhou Jiangsu China
| | - Zhenwen Zhang
- Department of Endocrinology; Clinical Medical College, Yangzhou University; Yangzhou Jiangsu China
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18
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Medici T, Shortland PJ. Effects of peripheral nerve injury on parvalbumin expression in adult rat dorsal root ganglion neurons. BMC Neurosci 2015; 16:93. [PMID: 26674138 PMCID: PMC4681077 DOI: 10.1186/s12868-015-0232-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 12/07/2015] [Indexed: 12/24/2022] Open
Abstract
Background Parvalbumin (PV) is a calcium binding protein that identifies a subpopulation of proprioceptive dorsal root ganglion (DRG) neurons. Calcitonin gene-related peptide (CGRP) is also expressed in a high proportion of muscle afferents but its relationship to PV is unclear. Little is known of the phenotypic responses of muscle afferents to nerve injury. Sciatic nerve axotomy or L5 spinal nerve ligation and section (SNL) lesions were used to explore these issues in adult rats using immunocytochemistry. Results In naive animals, the mean PV expression was 25 % of L4 or L5 dorsal root ganglion (DRG) neurons, and this was unchanged 2 weeks after sciatic nerve axotomy. Colocalization studies with the injury marker activating transcription factor 3 (ATF3) showed that approximately 24 % of PV neurons expressed ATF3 after sciatic nerve axotomy suggesting that PV may show a phenotypic switch from injured to uninjured neurons. This possibility was further assessed using the spinal nerve ligation (SNL) injury model where injured and uninjured neurons are located in different DRGs. Two weeks after L5 SNL there was no change in total PV staining and essentially all L5 PV neurons expressed ATF3. Additionally, there was no increase in PV-ir in the adjacent uninjured L4 DRG cells. Co-labelling of DRG neurons revealed that less than 2 % of PV neurons normally expressed CGRP and no colocalization was seen after injury. Conclusion These experiments clearly show that axotomy does not produce down regulation of PV protein in the DRG. Moreover, this lack of change is not due to a phenotypic switch in PV immunoreactive (ir) neurons, or de novo expression of PV-ir in uninjured neurons after nerve injury. These results further illustrate differences that occur when muscle afferents are injured as compared to cutaneous afferents.
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Affiliation(s)
- Tom Medici
- Centre for Neuroscience and Trauma, Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, Newark Street, London, E1 2AT, UK. .,Queens Hospital, Romford, Essex, RM7 0AG, UK.
| | - Peter J Shortland
- School of Science and Health, Western Sydney University, Narellen Road, Campbelltown, NSW, 2560, Australia. .,Centre for Neuroscience and Trauma, Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, Newark Street, London, E1 2AT, UK.
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19
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Baxter JC, Ramachandra R, Mayne DR, Elmslie KS. Functional expression of α7-nicotinic acetylcholine receptors by muscle afferent neurons. J Neurophysiol 2014; 112:1549-58. [PMID: 24966300 DOI: 10.1152/jn.00035.2014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The exercise pressor reflex (EPR) is generated by group III and IV muscle afferents during exercise to increase cardiovascular function. Muscle contraction is triggered by ACh, which is metabolized into choline that could serve as a signal of exercise-induced activity. We demonstrate that ACh can induce current in muscle afferents neurons isolated from male Sprague-Dawley rats. The nicotinic ACh receptors (nAChRs) appear to be expressed by some group III-IV neurons since capsaicin (TRPV1) and/or ATP (P2X) induced current in 56% of ACh-responsive neurons. α7- And α4β2-nAChRs have been shown to be expressed in sensory neurons. An α7-nAChR antibody stained 83% of muscle afferent neurons. Functional expression was demonstrated by using the specific α7-nAChR blockers α-conotoxin ImI (IMI) and methyllycaconitine (MLA). MLA inhibited ACh responses in 100% of muscle afferent neurons, whereas IMI inhibited ACh responses in 54% of neurons. Dihydro-β-erythroidine, an α4β2-nAChR blocker, inhibited ACh responses in 50% of muscle afferent neurons, but recovery from block was not observed. Choline, an α7-nAChR agonist, elicited a response in 60% of ACh-responsive neurons. Finally, we demonstrated the expression of α7-nAChR by peripherin labeled (group IV) afferent fibers within gastrocnemius muscles. Some of these α7-nAChR-positive fibers were also positive for P2X3 receptors. Thus choline could serve as an activator of the EPR by opening α7-nAChR expressed by group IV (and possible group III) afferents. nAChRs could become pharmacological targets for suppressing the excessive EPR activation in patients with peripheral vascular disease.
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Affiliation(s)
- James C Baxter
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A.T. Still University of Health Sciences, Kirksville, Missouri
| | - Renuka Ramachandra
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A.T. Still University of Health Sciences, Kirksville, Missouri
| | - Dustin R Mayne
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A.T. Still University of Health Sciences, Kirksville, Missouri
| | - Keith S Elmslie
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A.T. Still University of Health Sciences, Kirksville, Missouri
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20
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McLachlan EM, Hu P. Inflammation in dorsal root ganglia after peripheral nerve injury: effects of the sympathetic innervation. Auton Neurosci 2013; 182:108-17. [PMID: 24418114 DOI: 10.1016/j.autneu.2013.12.009] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2013] [Accepted: 12/11/2013] [Indexed: 12/26/2022]
Abstract
Following a peripheral nerve injury, a sterile inflammation develops in sympathetic and dorsal root ganglia (DRGs) with axons that project in the damaged nerve trunk. Macrophages and T-lymphocytes invade these ganglia where they are believed to release cytokines that lead to hyperexcitability and ectopic discharge, possibly contributing to neuropathic pain. Here, we examined the role of the sympathetic innervation in the inflammation of L5 DRGs of Wistar rats following transection of the sciatic nerve, comparing the effects of specific surgical interventions 10-14 days prior to the nerve lesion with those of chronic administration of adrenoceptor antagonists. Immunohistochemistry was used to define the invading immune cell populations 7 days after sciatic transection. Removal of sympathetic activity in the hind limb by transecting the preganglionic input to the relevant lumbar sympathetic ganglia (ipsi- or bilateral decentralization) or by ipsilateral removal of these ganglia with degeneration of postganglionic axons (denervation), caused less DRG inflammation than occurred after a sham sympathectomy. By contrast, denervation of the lymph node draining the lesion site potentiated T-cell influx. Systemic treatment with antagonists of α1-adrenoceptors (prazosin) or β-adrenoceptors (propranolol) led to opposite but unexpected effects on infiltration of DRGs after sciatic transection. Prazosin potentiated the influx of macrophages and CD4(+) T-lymphocytes whereas propranolol tended to reduce immune cell invasion. These data are hard to reconcile with many in vitro studies in which catecholamines acting mainly via β2-adrenoceptors have inhibited the activation and proliferation of immune cells following an inflammatory challenge.
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Affiliation(s)
- Elspeth M McLachlan
- Neuroscience Research Australia, Randwick, NSW 2031, and the University of New South Wales, Sydney, NSW 2052, Australia.
| | - Ping Hu
- Neuroscience Research Australia, Randwick, NSW 2031, and the University of New South Wales, Sydney, NSW 2052, Australia
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Abstract
Rodent models of nerve injury have increased our understanding of peripheral nerve regeneration, but clinical applications have been scarce, partly because such models do not adequately recapitulate the situation in humans. In human injuries, axons are often required to extend over much longer distances than in mice, and injury leaves distal nerve fibres and target tissues without axonal contact for extended amounts of time. Distal Schwann cells undergo atrophy owing to the lack of contact with proximal neurons, which results in reduced expression of neurotrophic growth factors, changes in the extracellular matrix and loss of Schwann cell basal lamina, all of which hamper axonal extension. Furthermore, atrophy and denervation-related changes in target tissues make good functional recovery difficult to achieve even when axons regenerate all the way to the target tissue. To improve functional outcomes in humans, strategies to increase the speed of axonal growth, maintain Schwann cells in a healthy, repair-capable state and keep target tissues receptive to reinnervation are needed. Use of rodent models of chronic denervation will facilitate our understanding of the molecular mechanisms of peripheral nerve regeneration and create the potential to test therapeutic advances.
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22
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Local and remote immune-mediated inflammation after mild peripheral nerve compression in rats. J Neuropathol Exp Neurol 2013; 72:662-80. [PMID: 23771220 DOI: 10.1097/nen.0b013e318298de5b] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
After experimental nerve injuries that extensively disrupt axons, such as chronic constriction injury, immune cells invade the nerve, related dorsal root ganglia (DRGs), and spinal cord, leading to hyperexcitability, raised sensitivity, and pain. Entrapment neuropathies, such as carpal tunnel syndrome, involve minimal axon damage, but patients often report widespread symptoms. To understand the underlying pathology, a tube was placed around the sciatic nerve in 8-week-old rats, leading to progressive mild compression as the animals grew. Immunofluorescence was used to examine myelin and axonal integrity, glia, macrophages, and T lymphocytes in the nerve, L5 DRGs, and spinal cord after 12 weeks. Tubes that did not constrict the nerve when applied caused extensive and ongoing loss of myelin, together with compromise of small-, but not large-, diameter axons. Macrophages and T lymphocytes infiltrated the nerve and DRGs. Activated glia proliferated in DRGs but not in spinal cord. Histologic findings were supported by clinical hyperalgesia to blunt pressure and cold allodynia. Tubes that did not compress the nerve induced only minor local inflammation. Thus, progressive mild nerve compression resulted in chronic local and remote immune-mediated inflammation depending on the degree of compression. Such neuroinflammation may explain the widespread symptoms in patients with entrapment neuropathies.
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Hart AM, Terenghi G, Wiberg M. Neuronal death after peripheral nerve injury and experimental strategies for neuroprotection. Neurol Res 2013; 30:999-1011. [DOI: 10.1179/174313208x362479] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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Ramachandra R, Hassan B, McGrew SG, Dompor J, Farrag M, Ruiz-Velasco V, Elmslie KS. Identification of CaV channel types expressed in muscle afferent neurons. J Neurophysiol 2013; 110:1535-43. [PMID: 23843437 DOI: 10.1152/jn.00069.2013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cardiovascular adjustments to exercise are partially mediated by group III/IV (small to medium) muscle afferents comprising the exercise pressor reflex (EPR). However, this reflex can be inappropriately activated in disease states (e.g., peripheral vascular disease), leading to increased risk of myocardial infarction. Here we investigate the voltage-dependent calcium (CaV) channels expressed in small to medium muscle afferent neurons as a first step toward determining their potential role in controlling the EPR. Using specific blockers and 5 mM Ba(2+) as the charge carrier, we found the major calcium channel types to be CaV2.2 (N-type) > CaV2.1 (P/Q-type) > CaV1.2 (L-type). Surprisingly, the CaV2.3 channel (R-type) blocker SNX482 was without effect. However, R-type currents are more prominent when recorded in Ca(2+) (Liang and Elmslie 2001). We reexamined the channel types using 10 mM Ca(2+) as the charge carrier, but results were similar to those in Ba(2+). SNX482 was without effect even though ∼27% of the current was blocker insensitive. Using multiple methods, we demonstrate that CaV2.3 channels are functionally expressed in muscle afferent neurons. Finally, ATP is an important modulator of the EPR, and we examined the effect on CaV currents. ATP reduced CaV current primarily via G protein βγ-mediated inhibition of CaV2.2 channels. We conclude that small to medium muscle afferent neurons primarily express CaV2.2 > CaV2.1 ≥ CaV2.3 > CaV1.2 channels. As with chronic pain, CaV2.2 channel blockers may be useful in controlling inappropriate activation of the EPR.
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Affiliation(s)
- Renuka Ramachandra
- The Baker Laboratory of Pharmacology, Department of Pharmacology, AT Still University of Health Sciences, Kirksville, Missouri
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25
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West CA, Ljungberg C, Wiberg M, Hart A. Sensory Neuron Death After Upper Limb Nerve Injury and Protective Effect of Repair. Neurosurgery 2013; 73:632-9; discussion 640. [DOI: 10.1227/neu.0000000000000066] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Abstract
BACKGROUND:
Extensive death of sensory neurons after nerve trauma depletes the number of regenerating neurons, contributing to inadequate cutaneous innervation density and poor sensory recovery. Experimentally proven neuroprotective neoadjuvant drugs require noninvasive in vivo measures of neuron death to permit clinical trials. In animal models of nerve transection, magnetic resonance imaging (MRI) proved a valid tool for quantifying sensory neuron loss within dorsal root ganglia (DRG) by measuring consequent proportional shrinkage of respective ganglia.
OBJECTIVE:
This system is investigated for clinical application after upper limb nerve injury and microsurgical nerve repair.
METHODS:
A 3-T clinical magnet was used to image and measure volume (Cavalieri principle) of C7-T1 DRG in uninjured volunteers (controls, n = 14), hand amputees (unrepaired nerve injury, n = 5), and early nerve repair patients (median and ulnar nerves transected, microsurgical nerve repair within 24 hours, n = 4).
RESULTS:
MRI was well tolerated. Volumetric analysis was feasible in 74% of patients. A mean 14% volume reduction was found in amputees' C7 and C8 DRG (P < .001 vs controls). Volume loss was lower in median and ulnar nerve repair patients (mean 3% volume loss, P < .01 vs amputees), and varied among patients. T1 DRG volume remained unaffected.
CONCLUSION:
MRI provides noninvasive in vivo assessment of DRG volume as a proxy clinical measure of sensory neuron death. The significant decrease found after unrepaired nerve injury provides indirect clinical evidence of axotomy-induced neuronal death. This loss was less after nerve repair, indicating a neuroprotective benefit of early repair. Volumetric MRI has potential diagnostic applications and is a quantitative tool for clinical trials of neuroprotective therapies.
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Affiliation(s)
- Christian Alexander West
- Department of Integrative Medical Biology, Section for Anatomy, Umea University, Umea, Sweden
- Department of Surgical and Perioperative Science, Section for Hand & Plastic Surgery, University Hospital, Umea, Sweden
| | - Christina Ljungberg
- Department of Integrative Medical Biology, Section for Anatomy, Umea University, Umea, Sweden
- Department of Surgical and Perioperative Science, Section for Hand & Plastic Surgery, University Hospital, Umea, Sweden
| | - Mikael Wiberg
- Department of Integrative Medical Biology, Section for Anatomy, Umea University, Umea, Sweden
- Department of Surgical and Perioperative Science, Section for Hand & Plastic Surgery, University Hospital, Umea, Sweden
| | - Andrew Hart
- Department of Surgical and Perioperative Science, Section for Hand & Plastic Surgery, University Hospital, Umea, Sweden
- Plastic Surgery Research, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
- Canniesburn Plastic Surgery Unit, Scottish National Brachial Plexus Service, Glasgow Royal Infirmary, Glasgow, United Kingdom
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Ramachandra R, McGrew SY, Baxter JC, Kiveric E, Elmslie KS. Tetrodotoxin-resistant voltage-dependent sodium channels in identified muscle afferent neurons. J Neurophysiol 2012; 108:2230-41. [PMID: 22855776 DOI: 10.1152/jn.00219.2012] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Muscle afferents are critical regulators of motor function (Group I and II) and cardiovascular responses to exercise (Group III and IV). However, little is known regarding the expressed voltage-dependent ion channels. We identified muscle afferent neurons in dorsal root ganglia (DRGs), using retrograde labeling to examine voltage-dependent sodium (Na(V)) channels. In patch-clamp recordings, we found that the dominant Na(V) current in the majority of identified neurons was insensitive to tetrodotoxin (TTX-R), with Na(V) current in only a few (14%) neurons showing substantial (>50%) TTX sensitivity (TTX-S). The TTX-R current was sensitive to a Na(V)1.8 channel blocker, A803467. Immunocytochemistry demonstrated labeling of muscle afferent neurons by a Na(V)1.8 antibody, which further supported expression of these channels. A portion of the TTX-R Na(V) current appeared to be noninactivating during our 25-ms voltage steps, which suggested activity of Na(V)1.9 channels. The majority of the noninactivating current was insensitive to A803467 but sensitive to extracellular sodium. Immunocytochemistry showed labeling of muscle afferent neurons by a Na(V)1.9 channel antibody, which supports expression of these channels. Further examination of the muscle afferent neurons showed that functional TTX-S channels were expressed, but were largely inactivated at physiological membrane potentials. Immunocytochemistry showed expression of the TTX-S channels Na(V)1.6 and Na(V)1.7 but not Na(V)1.1. Na(V)1.8 and Na(V)1.9 appear to be the dominant functional sodium channels in small- to medium-diameter muscle afferent neurons. The expression of these channels is consistent with the identification of these neurons as Group III and IV, which mediate the exercise pressor reflex.
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Affiliation(s)
- Renuka Ramachandra
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, AT Still University of Health Sciences, Kirksville, MO 63501, USA
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Englezou PC, Esposti MD, Wiberg M, Reid AJ, Terenghi G. Mitochondrial involvement in sensory neuronal cell death and survival. Exp Brain Res 2012; 221:357-67. [DOI: 10.1007/s00221-012-3179-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Accepted: 06/29/2012] [Indexed: 12/19/2022]
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Sanada LS, Tavares MR, Neubern MCM, Salgado HC, Fazan VPS. Can Wistar rats be used as the normotensive controls for nerve morphometry investigations in spontaneously hypertensive rats (SHR)? Acta Cir Bras 2012; 26:514-20. [PMID: 22042117 DOI: 10.1590/s0102-86502011000600018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Accepted: 08/11/2011] [Indexed: 11/21/2022] Open
Abstract
PURPOSE We compared the sural nerve morphology among Wistar (WR), Wistar-Kyoto (WKY) and Spontaneously hypertensive (SHR) rats, including the nerve fascicles and myelinated fibers morphometry. METHODS Age matched (20 weeks) female WR (N=6), WKY (N=6) and SHR (N=7) had their right and left sural nerves removed, embedded in epoxy resin, and observed by light microscopy. Morphometric analysis was performed with the aid of computer software. RESULTS Despite presenting the same age, WR were heavier than WKY and SHR, as were SHR compared to WKY. Systolic arterial pressure was higher in SHR compared to WR, but no differences between SHR and WKY or WR and WKY were observed. The sural nerves were morphometrically symmetric between proximal and distal segments on the same side and between sides in all strains with no differences in the myelinated fiber number. Schwann cell number and density were smaller in SHR and G ratio was larger in SHR, indicating that SHR have thinner myelinated fibers. CONCLUSION Sural nerve morphology is similar between WKY and WR, allowing the use of WR as the SHR controls in morphological investigations involving peripheral neuropathies.
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Affiliation(s)
- Luciana Sayuri Sanada
- Department of Neuroscience and Behavioral Neurosciences, FMRP, USP, Ribeirao Preto, SP, Brazil
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Kalous A, Nangle MR, Anastasia A, Hempstead BL, Keast JR. Neurotrophic actions initiated by proNGF in adult sensory neurons may require peri-somatic glia to drive local cleavage to NGF. J Neurochem 2012; 122:523-36. [PMID: 22621370 DOI: 10.1111/j.1471-4159.2012.07799.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The nerve growth factor (NGF) precursor, proNGF, is implicated in various neuropathological states. ProNGF signals apoptosis by forming a complex with the receptors p75 and sortilin, however, it can also induce neurite growth, proposed to be mediated by the receptor of mature NGF, tyrosine kinase receptor A (TrkA). The way in which these dual effects occur in adult neurons is unclear. We investigated the neurotrophic effects of proNGF on peptidergic sensory neurons isolated from adult mouse dorsal root ganglia and found that proNGF stimulated neurite extension and branching, requiring p75, sortilin and TrkA. Neurite growth rarely occurred in sortilin-expressing neurons but was commonly observed in TrkA-positive, sortilin-negative neurons that associated closely with sortilin-positive glia. ProNGF was unable to induce local trophic effects at growth cones where sortilin-positive glia was absent. We propose that in adult sensory neurons the neurotrophic response to proNGF is mediated by NGF and TrkA, and that peri-somatic glia may participate in sortilin- and p-75 dependent cleavage of proNGF. The potential ability of local glial cells to provide a targeted supply of NGF may provide an important way to promote trophic (rather than apoptotic) outcomes under conditions where regeneration or sprouting is required.
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Affiliation(s)
- Adrianna Kalous
- Pain Management Research Institute and Kolling Institute, University of Sydney at Royal North Shore Hospital, St Leonards, NSW, Australia
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Holub B, Kloepper J, Tóth B, Bíro T, Kofler B, Paus R. The neuropeptide galanin is a novel inhibitor of human hair growth. Br J Dermatol 2012; 167:10-6. [DOI: 10.1111/j.1365-2133.2012.10890.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Sanada LS, da Rocha Kalil AL, Tavares MR, Neubern MCM, Salgado HC, Fazan VPS. Sural nerve involvement in experimental hypertension: morphology and morphometry in male and female normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). BMC Neurosci 2012; 13:24. [PMID: 22380617 PMCID: PMC3350456 DOI: 10.1186/1471-2202-13-24] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2011] [Accepted: 03/02/2012] [Indexed: 01/20/2023] Open
Abstract
Background The sural nerve has been widely investigated in experimental models of neuropathies but information about its involvement in hypertension was not yet explored. The aim of the present study was to compare the morphological and morphometric aspects of different segments of the sural nerve in male and female spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats. Rats aged 20 weeks (N = 6 in each group) were investigated. After arterial pressure and heart rate recordings in anesthetized animals, right and left sural nerves were removed and prepared for epoxy resin embedding and light microscopy. Morphometric analysis was performed with the aid of computer software, and took into consideration the fascicle area and diameter, as well as myelinated fiber number, density, area and diameter. Results Significant differences were observed for the myelinated fiber number and density, comparing different genders of WKY and SHR. Also, significant differences for the morphological (thickening of the endoneural blood vessel walls and lumen reduction) and morphometric (myelinated fibers diameter and G ratio) parameters of myelinated fibers were identified. Morphological exam of the myelinated fibers suggested the presence of a neuropathy due to hypertension in both SHR genders. Conclusions These results indicate that hypertension altered important morphometric parameters related to nerve conduction of sural nerve in hypertensive animals. Moreover the comparison between males and females of WKY and SHR allows the conclusion that the morphological and morphometric parameters of sural nerve are not gender related. The morphometric approach confirmed the presence of neuropathy, mainly associated to the small myelinated fibers. In conclusion, the present study collected evidences that the high blood pressure in SHR is affecting the sural nerve myelinated fibers.
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Affiliation(s)
- Luciana Sayuri Sanada
- Department of Neuroscience and Behavioral Neurosciences, University of São Paulo, Monte Alegre, Ribeirão Preto, Brazil
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Hübner S, Efthymiadis A. Recent progress in histochemistry and cell biology. Histochem Cell Biol 2012; 137:403-57. [PMID: 22366957 DOI: 10.1007/s00418-012-0933-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/06/2012] [Indexed: 01/06/2023]
Abstract
Studies published in Histochemistry and Cell Biology in the year 2011 represent once more a manifest of established and newly sophisticated techniques being exploited to put tissue- and cell type-specific molecules into a functional context. The review is therefore the Histochemistry and Cell Biology's yearly intention to provide interested readers appropriate summaries of investigations touching the areas of tissue biology, developmental biology, the biology of the immune system, stem cell research, the biology of subcellular compartments, in order to put the message of such studies into natural scientific-/human- and also pathological-relevant correlations.
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Affiliation(s)
- Stefan Hübner
- Institute of Anatomy and Cell Biology, University of Würzburg, Würzburg, Germany.
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Landerholm ÅH, Ekblom AG, Hansson PT. Somatosensory function in patients with and without pain after traumatic peripheral nerve injury. Eur J Pain 2012; 14:847-53. [DOI: 10.1016/j.ejpain.2010.01.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2009] [Revised: 12/28/2009] [Accepted: 01/30/2010] [Indexed: 10/19/2022]
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Abstract
Following distal nerve injury significant sensory neuronal cell death occurs in the dorsal root ganglia, while after a more proximal injury, such as brachial plexus injury, a sizeable proportion of spinal motoneurons also undergo cell death. This phenomenon has been undervalued for a long time, but it has a significant role in the lack of functional recuperation, as neuronal cells cannot divide and be replaced, hence the resulting nerve regeneration is usually suboptimal. It is now accepted that this cell death is due to apoptosis, as indicated by analysis of specific genes involved in the apoptotic signalling cascade. Immediate nerve repair, either by direct suturing or nerve grafting, gives a degree of neuroprotection, but this approach does not fully prevent neuronal cell death and importantly it is not always possible. Our work has shown that pharmacological intervention using either acetyl-L-carnitine (ALCAR) or N-acetyl-cysteine (NAC) give complete neuroprotection in different types of peripheral nerve injury. Both compounds are clinically safe and experimental work has defined the best dose, timing after injury and duration of administration. The efficacy of neuroprotection of ALCAR and NAC can be monitored non-invasively using MRI, as demonstrated experimentally and more recently by clinical studies of the volume of dorsal root ganglia. Translation to patients of this pharmacological intervention requires further work, but the available results indicate that this approach will help to secure a better functional outcome following peripheral nerve injury and repair.
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Affiliation(s)
- Giorgio Terenghi
- Blond McIndoe Laboratories, Biomedicine, University of Manchester, Manchester Academic Health Science Centre, UK.
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Reid AJ, Mantovani C, Shawcross SG, Terenghi G, Wiberg M. Phenotype of distinct primary sensory afferent subpopulations and caspase-3 expression following axotomy. Histochem Cell Biol 2011; 136:71-8. [PMID: 21674244 DOI: 10.1007/s00418-011-0829-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/27/2011] [Indexed: 12/20/2022]
Abstract
Specific sensory neuronal subpopulations show contrasting responses to peripheral nerve injury, as shown by the axotomy-induced death of many cutaneous sensory neurons whilst muscular sensory afferents survive an identical insult. We used a novel combination of retrograde neuronal tracing with immunohistochemistry and laser microdissection techniques, in order to describe the neurochemistry of medial gastrocnemius (muscular sensory afferents) and sural (cutaneous sensory afferents) branches of the rat sciatic nerve and relate this to the pro-apoptotic caspase-3 gene expression following nerve transection. Our results demonstrated distinctions in medial gastrocnemius and sural neuron populations with the most striking difference in the respective proportions of isolectin B4 (IB4) staining neurons (3.7 V 32.8%). The mean neuronal area of the medial gastrocnemius (MG) neurons was larger than that of the sural (SUR) neurons (1,070.8 V 646.2 μm²) and each phenotypic group was significantly smaller in sural neurons than in MG neurons. At 1 week post-axotomy, MG neurons markedly downregulated caspase-3, whilst SUR neurons upregulated caspase-3 gene expression; this may be attributable to the differing IB4-positive composition of the subpopulations. These findings provide further clarification in the understanding of two distinct neuronal populations used increasingly in nerve injury models.
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Affiliation(s)
- Adam J Reid
- Blond McIndoe Research Laboratories, Tissue Injury and Repair Group, University of Manchester, Oxford Road, Manchester, UK.
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Kirillova I, Rausch VH, Tode J, Baron R, Jänig W. Mechano- and thermosensitivity of injured muscle afferents. J Neurophysiol 2011; 105:2058-73. [PMID: 21307318 DOI: 10.1152/jn.00938.2010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Injury of limb nerves leading to neuropathic pain mostly affects deep somatic nerves including muscle nerves. Here, we investigated the functional properties of injured afferent fibers innervating the lateral gastrocnemius-soleus muscle 4-13 h [time period (TP) I] and 4-7 days (TP II) after nerve crush in anesthetized rats using neurophysiological recordings from either the sciatic nerve (165 A-, 137 C-fibers) or the dorsal root L(5) (43 A-, 28 C-fibers). Ongoing activity and responses to mechanical or thermal stimulation of the injury site of the nerve were studied quantitatively. Of the electrically identified A- and C-fibers, 5 and 38% exhibited ectopic activity, respectively, in TP I and 51 and 61%, respectively, in TP II. Thus all afferent fibers in an injured muscle nerve developed ectopic activity since ∼ 50% of the fibers in a muscle nerve are somatomotor or sympathetic postganglionic. Ongoing activity was present in 50% of the afferent A-fibers (TP II) and in 53-56% of the afferent C-fibers (TP I and II). In TP II, mechanical, cold, and heat sensitivity were present in 91, 63, and 52% of the afferent A-fibers and in 50, 40, and 66% of the afferent C-fibers. The cold and heat activation thresholds were 5-27 and 35-48°C, respectively, covering the noxious and innocuous range. Most afferent fibers showed combinations of these sensitivities. Mechano- and cold sensitivity had a significantly higher representation in A- than in C-fibers, but heat sensitivity had a significantly higher representation in C- than in A-fibers. These functional differences between A- and C-fibers applied to large- as well as small-diameter A-fibers. Comparing the functional properties of injured muscle A- and C-afferents with those of injured cutaneous A- and C-afferents shows that both populations of injured afferent neurons behave differently in several aspects.
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Affiliation(s)
- Irina Kirillova
- Physiologisches Institut, Christian-Albrechts-Universität zu Kiel, Olshausenstrasse 40, 24098 Kiel, Germany
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Keast JR, Forrest SL, Osborne PB. Sciatic nerve injury in adult rats causes distinct changes in the central projections of sensory neurons expressing different glial cell line-derived neurotrophic factor family receptors. J Comp Neurol 2010; 518:3024-45. [PMID: 20533358 DOI: 10.1002/cne.22378] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Most small unmyelinated neurons in adult rat dorsal root ganglia (DRG) express one or more of the coreceptors targeted by glial cell line-derived neurotrophic factor (GDNF), neurturin, and artemin (GFRalpha1, GFRalpha2, and GFRalpha3, respectively). The function of these GDNF family ligands (GFLs) is not fully elucidated but recent evidence suggests GFLs could function in sensory neuron regeneration after nerve injury and peripheral nociceptor sensitization. In this study we used immunohistochemistry to determine if the DRG neurons targeted by each GFL change after sciatic nerve injury. We compared complete sciatic nerve transection and the chronic constriction model and found that the pattern of changes incurred by each injury was broadly similar. In lumbar spinal cord there was a widespread increase in neuronal GFRalpha1 immunoreactivity (IR) in the L1-6 dorsal horn. GFRalpha3-IR also increased but in a more restricted area. In contrast, GFRalpha2-IR decreased in patches of superficial dorsal horn and this loss was more extensive after transection injury. No change in calcitonin gene-related peptide-IR was detected after either injury. Analysis of double-immunolabeled L5 DRG sections suggested the main effect of injury on GFRalpha1- and GFRalpha3-IR was to increase expression in both myelinated and unmyelinated neurons. In contrast, no change in basal expression of GFRalpha2-IR was detected in DRG by analysis of fluorescence intensity and there was a small but significant reduction in GFRalpha2-IR neurons. Our results suggest that the DRG neuronal populations targeted by GDNF, neurturin, or artemin and the effect of exogenous GFLs could change significantly after a peripheral nerve injury.
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Affiliation(s)
- Janet R Keast
- Pain Management Research Institute, Kolling Institute of Medical Research, University of Sydney at Royal North Shore Hospital, St Leonards NSW 2065, Australia.
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Peirce C, Alexander LE, O'herlihy C, O'connell PR, Jones JFX. Central representation of the inferior rectal nerve of the rat. Dis Colon Rectum 2010; 53:315-20. [PMID: 20173479 DOI: 10.1007/dcr.0b013e3181c3873c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
PURPOSE Obstetric injury to the pudendal nerve contributes significantly to fecal incontinence. The inferior rectal nerve, a terminal branch of the motor division of the pudendal nerve, innervates the external anal sphincter. Animal models have been developed to establish the scientific basis of sacral neuromodulation. The aims of this study were to determine the spinal location of inferior rectal nerve motoneurons projecting to the external anal sphincter and whether the inferior rectal nerve carries sensory fibers. METHODS Ten female virgin Wistar rats were used; 7 underwent bilateral inferior rectal nerve section and application of the neuronal tracer fluorogold. Five days later dorsal root ganglia L5 to S2 and the lumbosacral spinal cord were harvested and stained for activating transcription factor 3, a molecular marker of nerve injury. Three animals were used to confirm the specificity of activating transcription factor 3 nuclear labeling as a marker of axotomy. RESULTS Fluorogold-labeled motoneurons were found exclusively at L6 in the dorsomedial sections of Onuf's nuclei (left and right), which contained 30 +/- 9 motoneurons with a median diameter of 28.3 microm (24.4-31.0) (25th-75th centiles). Double-labeled sensory neurons (fluorogold-labeled cytoplasm and activating transcription factor 3-labeled nuclei) were found in dorsal root ganglia L6 to S2 and were smaller in diameter (20.5 microm (17.8-26.7); median (25th-75th centiles)) than motoneurons (P < .0,001). CONCLUSIONS The external anal sphincter receives both motor and sensory innervation from the inferior rectal nerve. Activating transcription factor 3 nuclear staining may prove useful for quantifying the degree of nerve injury in animal models of fecal incontinence.
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Affiliation(s)
- Colin Peirce
- School of Medicine and Medical Science, University College Dublin, Belfield, Dublin, Ireland
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How do the satellite glia cells of the dorsal root ganglia respond to stressed neurons? – nitric oxide saga from embryonic development to axonal injury in adulthood. ACTA ACUST UNITED AC 2010; 6:11-7. [DOI: 10.1017/s1740925x09990494] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Dorsal root ganglia (DRG) respond to peripheral nerve injury by up-regulating nitric oxide (NO) production by neurons and glia in addition to local fibroblasts, endothelium and macrophages. We hypothesise that NO produced from these cells has specific roles. We have shown that when neuronal NO synthase (nNOS) is blocked in axotomised DRG, neurons undergo degenerative changes (Thippeswamy et al., 2001, 2007a). Further, we demonstrated that increased neuronal NO production, in response to axotomy/growth factor-deprivation in vitro, signals glial cells to produce trophic factors to support neuronal survival (Thippeswamy et al., 2005a). Recently, we found that treating satellite glia–neuron co-cultures with nNOS inhibitor, 7-nitroindazole (7NI), decreases the number of nestin+ cells that show neuron-like morphology. Cultured/axotomised DRG also upregulate inducible NOS (iNOS) in non-neuronal cells. Therefore, it is plausible that degenerative changes following nNOS inhibition are also due to iNOS-mediated excessive NO production by non-neuronal cells, which indeed is cytotoxic. NG-nitro-l-arginine methylester (L-NAME), the pan NOS inhibitor did not significantly change nNOS+ neuron number in axotomised DRG compared to 7NI suggesting that iNOS-mediated NO contributes to the degenerative process. In this paper, these findings from our and others' past work on NO-mediated neuron–glia signalling in axotomised DRG are discussed.
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Abstract
The skin, the largest organ of the body, functions as a barrier between the body proper and the external environment, as it is constantly exposed to noxious stressors. During the last few years, the concept of an interactive network involving cutaneous nerves, the neuroendocrine axis, and the immune system has emerged. The neuroendocrine system of the skin is composed of locally produced neuroendocrine mediators that interact with specific receptors. Among these mediators are neuropeptides, including members of the galanin peptide family--galanin, galanin-message associated peptide, galanin-like peptide, and alarin--which are produced in neuronal as well as nonneuronal cells in the skin. Here, we review the expression of the galanin peptides and their receptors in the skin, and the known functions of galanin peptides in different compartments of the skin. We discuss these data in light of the role of the galanin peptide family in inflammation and cell proliferation.
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Kalous A, Keast JR. Conditioning lesions enhance growth state only in sensory neurons lacking calcitonin gene-related peptide and isolectin B4-binding. Neuroscience 2009; 166:107-21. [PMID: 20006678 DOI: 10.1016/j.neuroscience.2009.12.019] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Revised: 12/01/2009] [Accepted: 12/05/2009] [Indexed: 12/31/2022]
Abstract
A conditioning lesion improves regeneration of central and peripheral axons of dorsal root ganglion (DRG) neurons after a subsequent injury by enhancing intrinsic growth capacity. This enhanced growth state is also observed in cultured DRG neurons, which support a more sparsely and rapidly elongating mode of growth after a prior conditioning lesion in vivo. Here we examined differences in the capacity or requirements of specific types of sensory neurons for regenerative growth, which has important consequences for development of strategies to improve recovery after injury. We showed that after partial or complete injury of the sciatic nerve in mice, an elongating mode of growth in vitro was activated only in DRG neurons that did not express calcitonin gene-related peptide (CGRP) or bind Bandeiraea simplicifolia I-isolectin B4 (IB4). We also directly examined the response of conditioned sensory neurons to nerve growth factor (NGF), which does not enhance growth in injured peripheral nerves in vivo. We showed that after partial injury, NGF stimulated a highly branched and linearly restricted rather than elongating mode of growth. After complete injury, the function of NGF was impaired, which immunohistochemical studies of DRG indicated was at least partly due to downregulation of the NGF receptor, tropomyosin-related kinase A (TrkA). These results suggest that, regardless of the type of conditioning lesion, each type of DRG neuron has a distinct intrinsic capacity or requirement for the activation of rapidly elongating growth, which does not appear to be influenced by NGF.
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Affiliation(s)
- A Kalous
- Pain Management Research Institute and Kolling Institute, University of Sydney at Royal North Shore Hospital, St Leonards, NSW 2065, Australia
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Duobles T, Lima TDS, Levy BDFA, Chadi G. S100beta and fibroblast growth factor-2 are present in cultured Schwann cells and may exert paracrine actions on the peripheral nerve injury. Acta Cir Bras 2009; 23:555-60. [PMID: 19030756 DOI: 10.1590/s0102-86502008000600014] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2008] [Accepted: 10/21/2008] [Indexed: 11/21/2022] Open
Abstract
PURPOSE The neurotrophic factor fibroblast growth factor-2 (FGF-2, bFGF) and Ca++ binding protein S100beta are expressed by the Schwann cells of the peripheral nerves and by the satellite cells of the dorsal root ganglia (DRG). Recent studies have pointed out the importance of the molecules in the paracrine mechanisms related to neuronal maintenance and plasticity of lesioned motor and sensory peripheral neurons. Moreover, cultured Schwann cells have been employed experimentally in the treatment of central nervous system lesions, in special the spinal cord injury, a procedure that triggers an enhanced sensorymotor function. Those cells have been proposed to repair long gap nerve injury. METHODS Here we used double labeling immunohistochemistry and Western blot to better characterize in vitro and in vivo the presence of the proteins in the Schwann cells and in the satellite cells of the DRG as well as their regulation in those cells after a crush of the rat sciatic nerve. RESULTS FGF-2 and S100beta are present in the Schwann cells of the sciatic nerve and in the satellite cells of the DRG. S100beta positive satellite cells showed increased size of the axotomized DRG and possessed elevated amount of FGF-2 immunoreactivity. Reactive satellite cells with increased FGF-2 labeling formed a ring-like structure surrounding DRG neuronal cell bodies.Reactive S100beta positive Schwann cells of proximal stump of axotomized sciatic nerve also expressed higher amounts of FGF-2. CONCLUSION Reactive peripheral glial cells synthesizing FGF-2 and S100beta may be important in wound repair and restorative events in the lesioned peripheral nerves.
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Affiliation(s)
- Tatiana Duobles
- Department of Neurology, School of Medicine, University of São Paulo, São Paulo, Brazil
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Gorodetskaya N, Grossmann L, Constantin C, Jänig W. Functional properties of cutaneous A- and C-fibers 1-15 months after a nerve lesion. J Neurophysiol 2009; 102:3129-41. [PMID: 19741109 DOI: 10.1152/jn.00203.2009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The functional properties of cutaneous afferent fibers were investigated 1-15 mo after nerve lesions, which allowed regeneration into denervated skin. After crushing or transection and resuturing the rat sural nerve, ongoing activity and responses to cold, heat, and mechanical stimuli presented to the denervated skin or to the nerve distal to the lesion were examined in 273 A-fibers and 211 C-fibers. Reinnervation of skin by A-fibers was largely complete by 1-4 mo after crushing but incomplete after transection and resuturing. A few A-fibers could be activated from the nerve trunk, even after 10-15 mo. Almost all regenerated A-fibers were mechanosensitive and about 6% were cold- or heat-sensitive. A few A-fibers had ongoing activity after nerve crush. Only 15-35% of C-fibers could be activated at 1-4 mo, but 60% were excited from the skin at 10-15 mo, when many also had receptive fields within the lesioned nerve. The remaining C-fibers had receptive fields only within the nerve trunk. Responses of both intraneural and intradermal endings of C-fibers could be classified into functional groups similar to those of C-fibers in control nerves to cutaneous stimuli. The frequency of afferent C-fibers with ongoing activity that were not highly cold sensitive was 45%. We conclude that the functional characteristics of afferent A- and C-fibers are expressed by regenerating nerve endings, even when they do not reinnervate their target tissue. The reinnervation of skin by afferent C-fibers is extremely slow and may never recover to normal.
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Affiliation(s)
- Natalia Gorodetskaya
- Physiologisches Institut, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
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Effects of N-acetyl-cysteine on the survival and regeneration of sural sensory neurons in adult rats. Brain Res 2009; 1287:58-66. [DOI: 10.1016/j.brainres.2009.06.038] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Revised: 06/10/2009] [Accepted: 06/12/2009] [Indexed: 11/23/2022]
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Reid AJ, Shawcross SG, Hamilton AE, Wiberg M, Terenghi G. N-acetylcysteine alters apoptotic gene expression in axotomised primary sensory afferent subpopulations. Neurosci Res 2009; 65:148-55. [PMID: 19559059 DOI: 10.1016/j.neures.2009.06.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2009] [Revised: 05/09/2009] [Accepted: 06/12/2009] [Indexed: 01/17/2023]
Abstract
Novel approaches are required in peripheral nerve injury management because current surgical techniques, which do not address axotomy-induced neuronal death, lead to deficient sensory recovery. Sensory neuronal death has functional preference with cutaneous neurons dying in great numbers whilst muscle afferents survive axotomy. This offers the potential of comparing similar cell types that suffer distinct fates upon nerve injury. Here, a novel approach, combining in vivo rat nerve injury model with laser microdissection and quantitative real-time polymerase chain reaction, identifies crucial disparities in apoptotic gene expression attributable to subpopulations of differing sensory modalities and examines the response to N-acetylcysteine (NAC) therapy. We show that axotomised muscle afferent neurons survive injury due to a neuroprotective response which markedly downregulates Bax and caspase-3 mRNA. In contrast, axotomised cutaneous sensory neurons significantly upregulate caspase-3 and alter both Bcl-2 and Bax expression such that pro-apoptotic Bax predominates. N-Acetylcysteine (NAC) intervention promotes neuroprotection of cutaneous sensory neurons through considerable upregulation of Bcl-2 and downregulation of both Bax and caspase-3 mRNA. The data presented identifies differential activation of apoptotic genes in axotomised neuronal subpopulations. Furthermore, NAC therapy instigates apoptotic gene expression changes in axotomised neurons, thereby offering pharmacotherapeutic potential in the clinical treatment of nerve injury.
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Affiliation(s)
- Adam J Reid
- Blond McIndoe Research Laboratories, Tissue Injury & Repair Group, University of Manchester, UK.
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Grossmann L, Gorodetskaya N, Baron R, Jänig W. Enhancement of Ectopic Discharge in Regenerating A- and C-Fibers by Inflammatory Mediators. J Neurophysiol 2009; 101:2762-74. [DOI: 10.1152/jn.91091.2008] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Afferent A- and C-fibers regenerating into a nerve following peripheral nerve injury are exposed to inflammatory mediators released by Schwann cells, resident and invading macrophages, and other inflammatory cells. Here we tested the hypothesis that ongoing and evoked activity in these afferent fibers are enhanced by a mixture of inflammatory mediators [inflammatory soup (IS)] applied to the injured nerve. Using in vivo electrophysiology, regenerating afferent nerve fibers were studied 7–14 days after sural nerve crush lesion. The ectopic activity was studied before and ≤1.5 h after topical application of IS to the nerve in 73 C-fibers and 22 A-fibers that were either ectopically active before application of IS (61 C-fibers, 17 A-fibers) or recruited by IS (12 C-fibers, 5 A-fibers). More than one half of the C-fibers were activated by IS for ≤90 min after its removal. The majority of mechano- (23/38) and heat-sensitive (29/35) C-fibers as well as mechano-sensitive A-fibers (12/17) decreased their activation thresholds and/or increased the response magnitude to mechanical and/or heat stimulation of the nerve. Noxious cold sensitivity, but not nonnoxious cold sensitivity, was weakly influenced by IS. Some initially nonresponsive C- and A-fibers developed new ectopic properties, i.e., were recruited, and exhibited ongoing activity and/or could be activated by physiological stimuli after application of IS. The results suggest that inflammatory mediators may be critical to enhance ectopic excitability of regenerating afferent nerve fibers. These peripheral mechanisms may be important triggering and maintaining neuropathic pain.
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Experimental models of peripheral neuropathic pain based on traumatic nerve injuries - an anatomical perspective. Ann Anat 2009; 191:248-59. [PMID: 19403284 DOI: 10.1016/j.aanat.2009.02.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Revised: 02/10/2009] [Accepted: 02/12/2009] [Indexed: 12/29/2022]
Abstract
Peripheral neuropathic pain (PNP) frequently occurs as a consequence of nerve injury and may differ depending upon the type of insult and the individual patient. Progress in our knowledge of PNP induction mechanisms depends upon the utilization of appropriate experimental models in rodents based on various types of peripheral nerve lesions. In this review, we draw attention to current knowledge on basic cellular and molecular events in various experimental models used to induce the PNP symptoms. Spontaneous ectopic activity of axotomized and non-axotomized primary sensory neurons, the bodies of which are located in the dorsal root ganglion (DRG), seems to be a key mechanism of PNP induction. The primary sensory neurons are directly affected by nerve injury or indirectly by activated satellite glial cells and adjoining immune cells that release a variety of molecules changing the microenvironment of the neurons. Recently, it has become clear that molecules produced during Wallerian degeneration play an important role not only in axon-promoting conditions distal to nerve injury but also in initiation of neuropathic pain. The molecules, transported by the blood, influence afferent neurons and their axons not only in DRG associated, but also those not directly associated with the injured nerve (i.e., in the contralateral DRG or at different spinal segments). Generally, all experimental PNP models based on a partial injury of peripheral nerve segments contain mechanisms initiated by signal molecules of Wallerian degeneration.
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Jänig W, Grossmann L, Gorodetskaya N. Mechano- and thermosensitivity of regenerating cutaneous afferent nerve fibers. Exp Brain Res 2009; 196:101-14. [PMID: 19139872 DOI: 10.1007/s00221-008-1673-5] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2008] [Accepted: 11/27/2008] [Indexed: 01/17/2023]
Abstract
Crush lesion of a skin nerve is followed by sprouting of myelinated (A) and unmyelinated (C) afferent fibers into the distal nerve stump. Here, we investigate quantitatively both ongoing activity and activity evoked by mechanical or thermal stimulation of the nerve in 43 A- and 135 C-fibers after crush lesion of the sural nerve using neurophysiological recordings in anesthetized rats. The discharge patterns in the injured afferent nerve fibers and in intact (control) afferent nerve fibers were compared. (1) Almost all (98%) A-fibers were mechanosensitive, some of them exhibited additionally weak cold/heat sensitivity; 7% had ongoing activity. (2) Three patterns of physiologically evoked activity were present in the lesioned C-fibers: (a) C-fibers with type 1 cold sensitivity (low cold threshold, inhibition on heating, high level of ongoing and cold-evoked activity; 23%): almost all of them were mechanoinsensitive and 40% of them were additionally heat-sensitive; (b) C-fibers with type 2 cold sensitivity (high cold threshold, low level of ongoing and cold-evoked activity; 23%). All of them were excited by mechanical and/or heat stimuli; (c) cold-insensitive C-fibers (54%), which were heat- and/or mechanosensitive. (3) The proportions of C-fibers exhibiting these three patterns of discharge to physiological stimuli were almost identical in the population of injured C-fibers and in a population of 91 intact cutaneous C-fibers. 4. Ongoing activity was present in 56% of the lesioned C-fibers. Incidence and rate of ongoing activity were the same in the populations of lesioned and intact type 1 cold-sensitive C-fibers. The incidence (but not rate) of ongoing activity was significantly higher in lesioned type 2 cold-sensitive and cold insensitive C-fibers than in the corresponding populations of intact C-fibers (42/93 fibers vs. 11/72 fibers).
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Affiliation(s)
- Wilfrid Jänig
- Physiologisches Institut, Christian-Albrechts-Universität zu Kiel, Olshausenstrasse 40, 24098 Kiel, Germany.
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Grossmann L, Gorodetskaya N, Teliban A, Baron R, Jänig W. Cutaneous afferent C-fibers regenerating along the distal nerve stump after crush lesion show two types of cold sensitivity. Eur J Pain 2008; 13:682-90. [PMID: 18976943 DOI: 10.1016/j.ejpain.2008.09.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2008] [Revised: 08/11/2008] [Accepted: 09/07/2008] [Indexed: 11/28/2022]
Abstract
Cutaneous C-fiber afferents show two distinct types of cold sensitivity corresponding to non-noxious and noxious cold sensations. Here, responses to cold stimulation of afferent fibers regenerating in the rat sural nerve were studied in vivo 7-14 days after nerve crush and compared with responses to mechanical and heat stimulation. The physiological stimuli were applied to the sural nerve at or distal to the lesion site. Ectopic activity was evoked in 43% of 98 A-fibers (all mechanosensitive; a few additionally weakly thermosensitive). Ectopic activity was evoked in 127 (49.2%) of 258 electrically identified C-fibers by the physiological stimuli. Eight C-fibers were spontaneously active only. Of the 127 C-fibers, 46% had one of two distinct response patterns to cooling: (1) type 1 cold-sensitive C-fibers (n=29) had a high rate of activity at 28 degrees C on the nerve surface and showed graded responses to cooling with maximal discharge rates of 11.5+/-1.1 imp/s. This activity was completely inhibited by heating, while 12/29 fibers were also excited at high threshold (median 48 degrees C) by heating. Only one type 1 cold-sensitive C-fiber was mechanosensitive. (2) Type 2 cold-sensitive C-fibers (n=29) were silent or showed a low rate of activity at 28 degrees C, had a high threshold (median 5 degrees C) and low maximal discharge rates (2.4+/-0.4 imp/s) to cooling. They were also heat-sensitive (n=25) and/or mechanosensitive (n=20). These C-fibers were, apart from their cold sensitivity, functionally indistinguishable from C-fibers with mechano- and/or heat sensitivity only. Thus regenerating cutaneous C-fibers show two types of cold sensitivity similar to those observed in intact skin: fibers of one group are predominantly sensitive to cooling, whereas the others are polymodal.
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Affiliation(s)
- Lydia Grossmann
- Physiologisches Institut, Christian-Albrechts-Universität zu Kiel, Olshausenstrasse 40, 24098 Kiel, Germany
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