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Marshall A, Alam U, Themistocleous A, Calcutt N, Marshall A. Novel and Emerging Electrophysiological Biomarkers of Diabetic Neuropathy and Painful Diabetic Neuropathy. Clin Ther 2021; 43:1441-1456. [PMID: 33906790 DOI: 10.1016/j.clinthera.2021.03.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2020] [Revised: 03/26/2021] [Accepted: 03/27/2021] [Indexed: 12/14/2022]
Abstract
PURPOSE Diabetic peripheral neuropathy (DPN) is the most common complication of diabetes. Small and large peripheral nerve fibers can be involved in DPN. Large nerve fiber damage causes paresthesia, sensory loss, and muscle weakness, and small nerve fiber damage is associated with pain, anesthesia, foot ulcer, and autonomic symptoms. Treatments for DPN and painful DPN (pDPN) pose considerable challenges due to the lack of effective therapies. To meet these challenges, there is a major need to develop biomarkers that can reliably diagnose and monitor progression of nerve damage and, for pDPN, facilitate personalized treatment based on underlying pain mechanisms. METHODS This study involved a comprehensive literature review, incorporating article searches in electronic databases (Google Scholar, PubMed, and OVID) and reference lists of relevant articles with the authors' substantial expertise in DPN. This review considered seminal and novel research and summarizes emerging biomarkers of DPN and pDPN that are based on neurophysiological methods. FINDINGS From the evidence gathered from 145 papers, this submission describes emerging clinical neurophysiological methods with potential to act as biomarkers for the diagnosis and monitoring of DPN as well as putative future roles as predictors of response to antineuropathic pain medication in pDPN. Nerve conduction studies only detect large fiber damage and do not capture pathology or dysfunction of small fibers. Because small nerve fiber damage is prominent in DPN, additional biomarkers of small nerve fiber function are needed. Activation of peripheral nociceptor fibers using laser, heat, or targeted electrical stimuli can generate pain-related evoked potentials, which are an objective neurophysiological measure of damage along the small fiber pathways. Assessment of nerve excitability, which provides a surrogate of axonal properties, may detect alterations in function before abnormalities are detected by nerve conduction studies. Microneurography and rate-dependent depression of the Hoffmann-reflex can be used to dissect underlying pain-generating mechanisms arising from the periphery and spinal cord, respectively. Their role in informing mechanistic-based treatment of pDPN as well as facilitating clinical trials design is discussed. IMPLICATIONS The neurophysiological methods discussed, although currently not practical for use in busy outpatient settings, detect small fiber and early large fiber damage in DPN as well as disclosing dominant pain mechanisms in pDPN. They are suited as diagnostic and predictive biomarkers as well as end points in mechanistic clinical trials of DPN and pDPN.
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Affiliation(s)
- Anne Marshall
- Musculoskeletal Biology, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, United Kingdom; Division of Diabetes, Endocrinology and Gastroenterology, School of Medical Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Uazman Alam
- Division of Diabetes, Endocrinology and Gastroenterology, School of Medical Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom; Cardiovascular and Metabolic Medicine, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Andreas Themistocleous
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom; Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Nigel Calcutt
- Department of Pathology, University of California, San Diego, La Jolla, California
| | - Andrew Marshall
- Musculoskeletal Biology, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, United Kingdom; Department of Clinical Neurophysiology, The Walton Centre, Liverpool, United Kingdom; Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom.
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Jin HY, Moon SS, Calcutt NA. Lost in Translation? Measuring Diabetic Neuropathy in Humans and Animals. Diabetes Metab J 2021; 45:27-42. [PMID: 33307618 PMCID: PMC7850880 DOI: 10.4093/dmj.2020.0216] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 10/06/2020] [Indexed: 12/21/2022] Open
Abstract
The worldwide diabetes epidemic is estimated to currently afflict almost 500 million persons. Long-term diabetes damages multiple organ systems with the blood vessels, eyes, kidneys and nervous systems being particularly vulnerable. These complications of diabetes reduce lifespan, impede quality of life and impose a huge social and economic burden on both the individual and society. Peripheral neuropathy is a debilitating complication that will impact over half of all persons with diabetes. There is no treatment for diabetic neuropathy and a disturbingly long history of therapeutic approaches showing promise in preclinical studies but failing to translate to the clinic. These failures have prompted re-examination of both the animal models and clinical trial design. This review focuses on the functional and structural parameters used as indices of peripheral neuropathy in preclinical and clinical studies and the extent to which they share a common pathogenesis and presentation. Nerve conduction studies in large myelinated fibers have long been the mainstay of preclinical efficacy screening programs and clinical trials, supplemented by quantitative sensory tests. However, a more refined approach is emerging that incorporates measures of small fiber density in the skin and cornea alongside these traditional assays at both preclinical and clinical phases.
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Affiliation(s)
- Heung Yong Jin
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Jeonbuk National University Medical School, Research Institute of Clinical Medicine of Jeonbuk National University-Biomedical Research Institute of Jeonbuk National University Hospital, Jeonju,
USA
| | - Seong-Su Moon
- Department of Internal Medicine, Dongguk University College of Medicine, Gyeongju,
USA
- Division of Endocrinology, Department of Internal Medicine, Nazareth General Hospital, Daegu,
Korea,
USA
| | - Nigel A. Calcutt
- Department of Pathology, University of California San Diego, La Jolla, CA,
USA
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3
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Sopacua M, Hoeijmakers JGJ, Merkies ISJ, Lauria G, Waxman SG, Faber CG. Small‐fiber neuropathy: Expanding the clinical pain universe. J Peripher Nerv Syst 2019; 24:19-33. [DOI: 10.1111/jns.12298] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 11/27/2018] [Accepted: 12/14/2018] [Indexed: 12/11/2022]
Affiliation(s)
- Maurice Sopacua
- Department of Neurology, School of Mental Health and NeuroscienceMaastricht University Medical Centre+ Maastricht The Netherlands
| | - Janneke G. J. Hoeijmakers
- Department of Neurology, School of Mental Health and NeuroscienceMaastricht University Medical Centre+ Maastricht The Netherlands
| | - Ingemar S. J. Merkies
- Department of Neurology, School of Mental Health and NeuroscienceMaastricht University Medical Centre+ Maastricht The Netherlands
- Department of NeurologySt. Elisabeth Hospital Willemstad Curaçao
| | - Giuseppe Lauria
- Neuroalgology UnitIRCCS Foundation, “Carlo Besta” Neurological Institute Milan Italy
- Department of Biomedical and Clinical Sciences “Luigi Sacco”University of Milan Milan Italy
| | - Stephen G. Waxman
- Department of NeurologyYale University School of Medicine New Haven Connecticut
- Center for Neuroscience and Regeneration ResearchVA Connecticut Healthcare System West Haven Connecticut
| | - Catharina G. Faber
- Department of Neurology, School of Mental Health and NeuroscienceMaastricht University Medical Centre+ Maastricht The Netherlands
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Hockley JRF, Smith ESJ, Bulmer DC. Human visceral nociception: findings from translational studies in human tissue. Am J Physiol Gastrointest Liver Physiol 2018; 315:G464-G472. [PMID: 29848022 DOI: 10.1152/ajpgi.00398.2017] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Peripheral sensitization of nociceptors during disease has long been recognized as a leading cause of inflammatory pain. However, a growing body of data generated over the last decade has led to the increased understanding that peripheral sensitization is also an important mechanism driving abdominal pain in highly prevalent functional bowel disorders, in particular, irritable bowel syndrome (IBS). As such, the development of drugs that target pain-sensing nerves innervating the bowel has the potential to be a successful analgesic strategy for the treatment of abdominal pain in both organic and functional gastrointestinal diseases. Despite the success of recent peripherally restricted approaches for the treatment of IBS, not all drugs that have shown efficacy in animal models of visceral pain have reduced pain end points in clinical trials of IBS patients, suggesting innate differences in the mechanisms of pain processing between rodents and humans and, in particular, how we model disease states. To address this gap in our understanding of peripheral nociception from the viscera and the body in general, several groups have developed experimental systems to study nociception in isolated human tissue and neurons, the findings of which we discuss in this review. Studies of human tissue identify a repertoire of human primary afferent subtypes comparable to rodent models including a nociceptor population, the targeting of which will shape future analgesic development efforts. Detailed mechanistic studies in human sensory neurons combined with unbiased RNA-sequencing approaches have revealed fundamental differences in not only receptor/channel expression but also peripheral pain pathways.
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Affiliation(s)
- James R F Hockley
- Department of Pharmacology, University of Cambridge , Cambridge , United Kingdom
| | - Ewan St John Smith
- Department of Pharmacology, University of Cambridge , Cambridge , United Kingdom
| | - David C Bulmer
- Department of Pharmacology, University of Cambridge , Cambridge , United Kingdom
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5
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Translational Model Systems for Complex Sodium Channel Pathophysiology in Pain. Handb Exp Pharmacol 2018; 246:355-369. [PMID: 29374838 DOI: 10.1007/164_2017_91] [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: 12/02/2022]
Abstract
Chronic pain patients are often left with insufficient treatment as the pathophysiology especially of neuropathic pain remains enigmatic. Recently, genetic variations in the genes of the voltage-gated sodium channels (Navs) were linked to inherited neuropathic pain syndromes, opening a research pathway to foster our understanding of the pathophysiology of neuropathic pain. More than 10 years ago, the rare, inherited pain syndrome erythromelalgia was linked to mutations in the subtype Nav1.7, and since then a plethora of mutations and genetic variations in this and other Nav genes were identified. Often the biophysical changes induced by the genetic alteration offer a straightforward explanation for the clinical symptoms, but mutations in some channels, especially Nav1.9, paint a more complex picture. Although efforts were undertaken to significantly advance our knowledge, translation from heterologous or animal model systems to humans remains a challenge. Here we present recent advances in translation using stem cell-derived human sensory neurons and their potential application for identification of better, effective, and more precise treatment for the individual pain patient.
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McGuire C, Boundouki G, Hockley JRF, Reed D, Cibert-Goton V, Peiris M, Kung V, Broad J, Aziz Q, Chan C, Ahmed S, Thaha MA, Sanger GJ, Blackshaw LA, Knowles CH, Bulmer DC. Ex vivo study of human visceral nociceptors. Gut 2018; 67:86-96. [PMID: 27654583 PMCID: PMC5754853 DOI: 10.1136/gutjnl-2016-311629] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Revised: 08/22/2016] [Accepted: 08/23/2016] [Indexed: 12/20/2022]
Abstract
OBJECTIVE The development of effective visceral analgesics free of deleterious gut-specific side effects is a priority. We aimed to develop a reproducible methodology to study visceral nociception in human tissue that could aid future target identification and drug evaluation. DESIGN Electrophysiological (single unit) responses of visceral afferents to mechanical (von Frey hair (VFH) and stretch) and chemical (bradykinin and ATP) stimuli were examined. Thus, serosal afferents (putative nociceptors) were used to investigate the effect of tegaserod, and transient receptor potential channel, vanilloid 4 (TRPV4) modulation on mechanical responses. RESULTS Two distinct afferent fibre populations, serosal (n=23) and muscular (n=21), were distinguished based on their differences in sensitivity to VFH probing and tissue stretch. Serosal units displayed sensitivity to key algesic mediators, bradykinin (6/14 units tested) and ATP (4/10), consistent with a role as polymodal nociceptors, while muscular afferents are largely insensitive to bradykinin (0/11) and ATP (1/10). Serosal nociceptor mechanosensitivity was attenuated by tegaserod (-20.8±6.9%, n=6, p<0.05), a treatment for IBS, or application of HC067047 (-34.9±10.0%, n=7, p<0.05), a TRPV4 antagonist, highlighting the utility of the preparation to examine the mechanistic action of existing drugs or novel analgesics. Repeated application of bradykinin or ATP produced consistent afferent responses following desensitisation to the first application, demonstrating their utility as test stimuli to evaluate analgesic activity. CONCLUSIONS Functionally distinct subpopulations of human visceral afferents can be demonstrated and could provide a platform technology to further study nociception in human tissue.
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Affiliation(s)
- Cian McGuire
- National Centre for Bowel Research and Surgical Innovation, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - George Boundouki
- Wingate Institute of Neurogastroenterology, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - James R F Hockley
- Wingate Institute of Neurogastroenterology, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - David Reed
- Wingate Institute of Neurogastroenterology, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Vincent Cibert-Goton
- National Centre for Bowel Research and Surgical Innovation, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Madusha Peiris
- Wingate Institute of Neurogastroenterology, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Victor Kung
- National Centre for Bowel Research and Surgical Innovation, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - John Broad
- National Centre for Bowel Research and Surgical Innovation, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Qasim Aziz
- Wingate Institute of Neurogastroenterology, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Christopher Chan
- National Centre for Bowel Research and Surgical Innovation, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Shafi Ahmed
- National Centre for Bowel Research and Surgical Innovation, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Mohamed A Thaha
- National Centre for Bowel Research and Surgical Innovation, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Gareth J Sanger
- National Centre for Bowel Research and Surgical Innovation, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - L Ashley Blackshaw
- Wingate Institute of Neurogastroenterology, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Charles H Knowles
- National Centre for Bowel Research and Surgical Innovation, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - David C Bulmer
- National Centre for Bowel Research and Surgical Innovation, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
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T-type calcium channels in chronic pain: mouse models and specific blockers. Pflugers Arch 2014; 466:707-17. [PMID: 24590509 DOI: 10.1007/s00424-014-1484-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Accepted: 02/13/2014] [Indexed: 02/01/2023]
Abstract
Pain is a quite frequent complaint accompanying numerous pathologies. Among these pathological cases, neuropathies are retrieved with identified etiologies (chemotherapies, diabetes, surgeries…) and also more diffuse syndromes such as fibromyalgia. More broadly, pain is one of the first consequences of the majority of inherited diseases. Despite its importance for the quality of life, current pain management is limited to drugs that are either old or with a limited efficacy or that possess a bad benefit/risk ratio. As no new pharmacological concept has led to new analgesics in the last decades, the discovery of medications is needed, and to this aim the identification of new druggable targets in pain transmission is a first step. Therefore, studies of ion channels in pain pathways are extremely active. This is particularly true with ion channels in peripheral sensory neurons in dorsal root ganglia (DRG) known now to express unique sets of these channels. Moreover, both spinal and supraspinal levels are clearly important in pain modulation. Among these ion channels, we and others revealed the important role of low voltage-gated calcium channels in cellular excitability in different steps of the pain pathways. These channels, by being activated nearby resting membrane potential have biophysical characteristics suited to facilitate action potential generation and rhythmicity. In this review, we will review the current knowledge on the role of these channels in the perception and modulation of pain.
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8
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Bourinet E, Altier C, Hildebrand ME, Trang T, Salter MW, Zamponi GW. Calcium-permeable ion channels in pain signaling. Physiol Rev 2014; 94:81-140. [PMID: 24382884 DOI: 10.1152/physrev.00023.2013] [Citation(s) in RCA: 221] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The detection and processing of painful stimuli in afferent sensory neurons is critically dependent on a wide range of different types of voltage- and ligand-gated ion channels, including sodium, calcium, and TRP channels, to name a few. The functions of these channels include the detection of mechanical and chemical insults, the generation of action potentials and regulation of neuronal firing patterns, the initiation of neurotransmitter release at dorsal horn synapses, and the ensuing activation of spinal cord neurons that project to pain centers in the brain. Long-term changes in ion channel expression and function are thought to contribute to chronic pain states. Many of the channels involved in the afferent pain pathway are permeable to calcium ions, suggesting a role in cell signaling beyond the mere generation of electrical activity. In this article, we provide a broad overview of different calcium-permeable ion channels in the afferent pain pathway and their role in pain pathophysiology.
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Serra J, Collado A, Solà R, Antonelli F, Torres X, Salgueiro M, Quiles C, Bostock H. Hyperexcitable C nociceptors in fibromyalgia. Ann Neurol 2014; 75:196-208. [DOI: 10.1002/ana.24065] [Citation(s) in RCA: 179] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 11/05/2013] [Accepted: 11/08/2013] [Indexed: 12/14/2022]
Affiliation(s)
- Jordi Serra
- Department of Neurology; MC Mutual; Barcelona Spain
- Neuroscience Technologies; Barcelona Science Park; Barcelona Spain
| | | | - Romà Solà
- Department of Neurology; MC Mutual; Barcelona Spain
- Neuroscience Technologies; Barcelona Science Park; Barcelona Spain
| | - Francesca Antonelli
- Department of Neurology; MC Mutual; Barcelona Spain
- Neuroscience Technologies; Barcelona Science Park; Barcelona Spain
| | | | | | - Cristina Quiles
- Department of Neurology; MC Mutual; Barcelona Spain
- Neuroscience Technologies; Barcelona Science Park; Barcelona Spain
| | - Hugh Bostock
- Department of Neurology; MC Mutual; Barcelona Spain
- Sobell Department of Motor Neuroscience and Movement Disorders; Institute of Neurology, University College London; London United Kingdom
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Kleggetveit IP, Namer B, Schmidt R, Helås T, Rückel M, Ørstavik K, Schmelz M, Jørum E. High spontaneous activity of C-nociceptors in painful polyneuropathy. Pain 2012; 153:2040-2047. [DOI: 10.1016/j.pain.2012.05.017] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Revised: 05/07/2012] [Accepted: 05/15/2012] [Indexed: 02/07/2023]
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Serra J. Microneurography: towards a biomarker of spontaneous pain. Pain 2012; 153:1989-1990. [PMID: 22820023 DOI: 10.1016/j.pain.2012.07.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Revised: 06/26/2012] [Accepted: 07/05/2012] [Indexed: 11/28/2022]
Affiliation(s)
- Jordi Serra
- MC Mutual, Barcelona, Spain Neuroscience Technologies, Barcelona, Spain Neuroscience Technologies, London, UK
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12
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Translation of drug effects from experimental models of neuropathic pain and analgesia to humans. Drug Discov Today 2012; 17:837-49. [PMID: 22445930 DOI: 10.1016/j.drudis.2012.02.010] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Revised: 01/31/2012] [Accepted: 02/21/2012] [Indexed: 11/22/2022]
Abstract
Neuropathic pain research remains a challenging undertaking owing to: (i) the lack of understanding about the underlying disease processes; and (ii) poor predictive validity of the current models of evoked pain used for the screening of novel compounds. Common consensus is that experimental models replicate symptoms (i.e. have face validity but no construct validity). Another issue that requires attention is the sensitivity of endpoints to discriminate drug effects that are relevant to the disease in humans. In this paper we provide an overview of the pre-clinical models that can be used in conjunction with a model-based approach to facilitate the prediction of drug effects in humans. Our review strongly suggests that evidence of the concentration-effect relationship is necessary for translational purposes.
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Abstract
Chronic pain is a frequent component of many neurological disorders, affecting 20-40% of patients for many primary neurological diseases. These diseases result from a wide range of pathophysiologies including traumatic injury to the central nervous system, neurodegeneration and neuroinflammation, and exploring the aetiology of pain in these disorders is an opportunity to achieve new insight into pain processing. Whether pain originates in the central or peripheral nervous system, it frequently becomes centralized through maladaptive responses within the central nervous system that can profoundly alter brain systems and thereby behaviour (e.g. depression). Chronic pain should thus be considered a brain disease in which alterations in neural networks affect multiple aspects of brain function, structure and chemistry. The study and treatment of this disease is greatly complicated by the lack of objective measures for either the symptoms or the underlying mechanisms of chronic pain. In pain associated with neurological disease, it is sometimes difficult to obtain even a subjective evaluation of pain, as is the case for patients in a vegetative state or end-stage Alzheimer's disease. It is critical that neurologists become more involved in chronic pain treatment and research (already significant in the fields of migraine and peripheral neuropathies). To achieve this goal, greater efforts are needed to enhance training for neurologists in pain treatment and promote greater interest in the field. This review describes examples of pain in different neurological diseases including primary neurological pain conditions, discusses the therapeutic potential of brain-targeted therapies and highlights the need for objective measures of pain.
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Affiliation(s)
- David Borsook
- MD Center for Pain and the Brain C/O Brain Imaging Center, McLean Hospital Belmont, MA 02478, USA.
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Microneurographic identification of spontaneous activity in C-nociceptors in neuropathic pain states in humans and rats. Pain 2011; 153:42-55. [PMID: 21993185 DOI: 10.1016/j.pain.2011.08.015] [Citation(s) in RCA: 149] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Revised: 07/11/2011] [Accepted: 08/15/2011] [Indexed: 12/21/2022]
Abstract
C-nociceptors do not normally fire action potentials unless challenged by adequate noxious stimuli. However, in pathological states nociceptors may become hyperexcitable and may generate spontaneous ectopic discharges. The aim of this study was to compare rat neuropathic pain models and to assess their suitability to model the spontaneous C-nociceptor activity found in neuropathic pain patients. Studies were performed in normal rats (n=40), healthy human subjects (n=15), peripheral neuropathic pain patients (n=20), and in five rat neuropathic pain models: nerve crush (n=24), suture (n=14), chronic constriction injury (n=12), STZ-induced diabetic neuropathy (n=56), and ddC-induced neuropathy (n=15). Microneurographic recordings were combined with electrical stimulation to monitor activity in multiple C fibers. Stimulation at 0.25 Hz allowed spontaneous impulses to be identified by fluctuations in baseline latency. Abnormal latency fluctuations could be produced by several mechanisms, and spontaneous activity was most reliably identified by the presence of unexplained latency increases corresponding to two or more additional action potentials. Spontaneous activity was present in a proportion of mechano-insensitive C-nociceptors in the patients and all rat models. The three focal traumatic nerve injury models provided the highest proportion (59.5%), whereas the two polyneuropathy models had fewer (18.6%), and the patients had an intermediate proportion (33.3%). Spontaneously active mechano-sensitive C-nociceptors were not recorded. Microneurographic recordings of spontaneous activity in diseased C-nociceptors may be useful for both short- and long-term drug studies, both in animals and in humans.
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Truini A, Leone C, Di Stefano G, Biasiotta A, La Cesa S, Teofoli P, Padua L, Cruccu G. Topographical distribution of warmth, burning and itch sensations in healthy humans. Neurosci Lett 2011; 494:165-8. [DOI: 10.1016/j.neulet.2011.03.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2010] [Revised: 02/09/2011] [Accepted: 03/02/2011] [Indexed: 11/25/2022]
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