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Allmendinger F, Scheuren PS, De Schoenmacker I, Brunner F, Rosner J, Curt A, Hubli M. Contact-Heat Evoked Potentials: Insights into Pain Processing in CRPS Type I. J Pain Res 2024; 17:989-1003. [PMID: 38505501 PMCID: PMC10949273 DOI: 10.2147/jpr.s436645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Accepted: 02/23/2024] [Indexed: 03/21/2024] Open
Abstract
Purpose The pathophysiological mechanisms underlying the development of chronic pain in complex regional pain syndrome (CRPS) are diverse and involve both peripheral and central changes in pain processing, such as sensitization of the nociceptive system. The aim of this study was to objectively distinguish the specific changes occurring at both peripheral and central levels in nociceptive processing in individuals with chronic CRPS type I. Patients and Methods Nineteen individuals with chronic CRPS type I and 16 age- and sex-matched healthy controls (HC) were recruited. All individuals underwent a clinical examination and pain assessment in the most painful limb, the contralateral limb, and a pain-free control area to distinguish between peripheral and central mechanisms. Contact-heat evoked potentials (CHEPs) were recorded after heat stimulation of the three different areas and amplitudes and latencies were analyzed. Additionally, quantitative sensory testing (QST) was performed in all three areas. Results Compared to HC, CHEP amplitudes in CRPS were only increased after stimulation of the painful area (p=0.025), while no increases were observed for the pain-free control area (p=0.14). None of the CHEP latencies were different between the two cohorts (all p>0.23). Furthermore, individuals with CRPS showed higher pain ratings after stimulation of the painful limb compared to their contralateral limb (p=0.013). Lastly, compared to HC, mechanical (p=0.012) and thermal (p=0.046) sensitivity was higher in the painful area of the CRPS cohort. Conclusion This study provides neurophysiological evidence supporting an intact thermo-nociceptive pathway with signs of peripheral sensitization, such as hyperexcitable primary afferent nociceptors, in individuals with CRPS type I. This is further supported by the observation of mechanical and thermal gain of sensation only in the painful limb. Additionally, the increased CHEP amplitudes might be related to fear-induced alterations of nociceptive processing.
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Affiliation(s)
- Florin Allmendinger
- Spinal Cord Injury Center, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
| | - Paulina Simonne Scheuren
- Spinal Cord Injury Center, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
- Department of Neurology, University Hospital Bern, Inselspital, University of Bern, Bern, Switzerland
- International Collaboration on Repair Discoveries, Vancouver, BC, Canada
- Department of Anesthesiology, Pharmacology & Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Iara De Schoenmacker
- Spinal Cord Injury Center, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
| | - Florian Brunner
- Department of Physical Medicine and Rheumatology, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
| | - Jan Rosner
- Spinal Cord Injury Center, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
- Department of Neurology, University Hospital Bern, Inselspital, University of Bern, Bern, Switzerland
- Danish Pain Research Center, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Armin Curt
- Spinal Cord Injury Center, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
| | - Michèle Hubli
- Spinal Cord Injury Center, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
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Felnhofer A, Martinek D, Pazour P, Riva G. PAIN-EX: Probing Alternative Interventions for Neutralizing pain EXperiences via Embodiment in Virtual Reality. CYBERPSYCHOLOGY, BEHAVIOR AND SOCIAL NETWORKING 2023; 26:662-664. [PMID: 37335953 DOI: 10.1089/cyber.2023.29286.ceu] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/21/2023]
Affiliation(s)
- Anna Felnhofer
- Department of Pediatrics and Adolescent Medicine, Division of Pediatric Pulmonology, Allergology and Endocrinology, Medical University of Vienna, Austria
- Comprehensive Center for Pediatrics, CCP, Medical University of Vienna, Vienna, Austria
| | - Daniel Martinek
- Doctoral School Computer Science, University of Vienna, Vienna, Austria
| | - Patrick Pazour
- Doctoral School Computer Science, University of Vienna, Vienna, Austria
| | - Giuseppe Riva
- Humane Technology Laboratory, Catholic University of Milan, Milan, Italy
- Applied Technology for Neuro-Psychology Laboratory, IRCCS Istituto Auxologico Italiano, Milan, Italy
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Hijma H, Koopmans I, Klaassen E, Doll RJ, Zuiker R, Groeneveld GJ. A crossover study evaluating the sex-dependent and sensitizing effects of sleep deprivation using a nociceptive test battery in healthy subjects. Br J Clin Pharmacol 2023; 89:361-371. [PMID: 35997713 PMCID: PMC10086808 DOI: 10.1111/bcp.15505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 07/21/2022] [Accepted: 08/04/2022] [Indexed: 12/01/2022] Open
Abstract
AIM We assessed whether total sleep deprivation (TSD) in combination with pain tests yields a reliable method to assess altered pain thresholds, which subsequently may be used to investigate (novel) analgesics in healthy subjects. METHODS This was a two-part randomized crossover study in 24 healthy men and 24 women. Subjects were randomized 1:1 to first complete a day of nonsleep-deprived nociceptive threshold testing, followed directly by a TSD night and morning of sleep-deprived testing, or first complete the TSD night and morning sleep-deprived testing, returning 7 days later for a day of nonsleep-deprived testing. A validated pain test battery (heat, pressure, electrical burst and stair, cold pressor pain test and conditioned pain modulation [CPM] paradigm) and sleep questionnaires were performed. RESULTS Subjects were significantly sleepier after TSD as measured using sleepiness questionnaires. Cold pressor pain tolerance (PTT, estimate of difference [ED] -10.8%, 95% CI -17.5 to -3.6%), CPM PTT (ED -0.69 mA, 95% CI -1.36 to -0.03 mA), pressure PTT (ED -11.2%, 95% CI -17.5% to -4.3%) and heat pain detection thresholds (ED -0.74 °C, 95% CI -1.34 to -0.14 °C) were significantly decreased after TSD compared to the baseline morning assessment in the combined analysis (men + women). Heat hyperalgesia was primarily driven by an effect of TSD in men, whereas cold and pressure hyperalgesia was primarily driven by the effects of TSD observed in women. CONCLUSIONS TSD induced sex-dependent hyperalgesia on cold, heat and pressure pain, and CPM response. These results suggest that the TSD model may be suitable to evaluate (novel) analgesics in early-phase drug studies.
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Affiliation(s)
- Hemme Hijma
- Centre for Human Drug Research, CL, Leiden, The Netherlands.,Leiden University Medical Centre, ZA, Leiden, The Netherlands
| | - Ingrid Koopmans
- Centre for Human Drug Research, CL, Leiden, The Netherlands.,Leiden University Medical Centre, ZA, Leiden, The Netherlands
| | - Erica Klaassen
- Centre for Human Drug Research, CL, Leiden, The Netherlands
| | | | - Rob Zuiker
- Centre for Human Drug Research, CL, Leiden, The Netherlands
| | - Geert Jan Groeneveld
- Centre for Human Drug Research, CL, Leiden, The Netherlands.,Leiden University Medical Centre, ZA, Leiden, The Netherlands
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Tsujimura T, Nakajima Y, Chotirungsan T, Kawada S, Tsutsui Y, Yoshihara M, Suzuki T, Nagoya K, Magara J, Inoue M. Inhibition of Water-Evoked Swallowing During Noxious Mechanical Stimulation of Tongue in Anesthetized Rats. Dysphagia 2022; 38:965-972. [PMID: 36127446 DOI: 10.1007/s00455-022-10522-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 09/11/2022] [Indexed: 11/30/2022]
Abstract
Dysphagia is sometimes accompanied by pain. Because orofacial structures subserve mastication and swallowing, orofacial pain might impair both functions. Tongue biting can occur not only accidentally while eating but also in some pathological conditions. However, it remains unclear whether noxious mechanical stimulation of the tongue affects swallowing. To explore this question, we evaluated the effects of lingual pinch stimulation on the initiation of swallowing evoked by distilled water (DW) infusion with a flow rate of 5.0 µL/s for 20 s into the pharyngolaryngeal region in anesthetized rats. The swallowing reflex was identified by electromyographic (EMG) bursts in the suprahyoid muscles which include the anterior belly of the digastric muscle, mylohyoid and geniohyoid muscles, and laryngeal elevation by visual inspection. The number of DW-evoked swallows during pinch stimulation was significantly smaller than that in a control condition or during pressure stimulation. The onset latency of the first swallow during pinch stimulation was significantly longer than that in the control condition. DW-evoked swallowing was almost abolished following bilateral transection of the superior laryngeal nerve (SLN) compared with the control condition, suggesting that the SLN plays a crucial role in the initiation of DW-evoked swallowing. Finally, electrophysiological data indicated that some SLN-responsive neurons in the nucleus tractus solitarii (nTS) exhibited delayed latency from a single SLN stimulation during lingual pinch stimulation. These results suggest that noxious mechanical stimulation of the tongue inhibits the initiation of swallowing and modulates neuronal activity in the nTS.
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Affiliation(s)
- Takanori Tsujimura
- Division of Dysphagia Rehabilitation, Niigata University Graduate School of Medical and Dental Sciences, Chuo-ku, Niigata, 951-8514, Japan.
| | - Yuta Nakajima
- Division of Dysphagia Rehabilitation, Niigata University Graduate School of Medical and Dental Sciences, Chuo-ku, Niigata, 951-8514, Japan
| | - Titi Chotirungsan
- Division of Dysphagia Rehabilitation, Niigata University Graduate School of Medical and Dental Sciences, Chuo-ku, Niigata, 951-8514, Japan
| | - Satomi Kawada
- Division of Dysphagia Rehabilitation, Niigata University Graduate School of Medical and Dental Sciences, Chuo-ku, Niigata, 951-8514, Japan
| | - Yuhei Tsutsui
- Division of Dysphagia Rehabilitation, Niigata University Graduate School of Medical and Dental Sciences, Chuo-ku, Niigata, 951-8514, Japan
| | - Midori Yoshihara
- Division of Dysphagia Rehabilitation, Niigata University Graduate School of Medical and Dental Sciences, Chuo-ku, Niigata, 951-8514, Japan
| | - Taku Suzuki
- Division of Dysphagia Rehabilitation, Niigata University Graduate School of Medical and Dental Sciences, Chuo-ku, Niigata, 951-8514, Japan
| | - Kouta Nagoya
- Division of Dysphagia Rehabilitation, Niigata University Graduate School of Medical and Dental Sciences, Chuo-ku, Niigata, 951-8514, Japan
| | - Jin Magara
- Division of Dysphagia Rehabilitation, Niigata University Graduate School of Medical and Dental Sciences, Chuo-ku, Niigata, 951-8514, Japan
| | - Makoto Inoue
- Division of Dysphagia Rehabilitation, Niigata University Graduate School of Medical and Dental Sciences, Chuo-ku, Niigata, 951-8514, Japan
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Langedijk J, Araya EI, Barroso AR, Tolenaars D, Nazaré M, Belabed H, Schoene J, Chichorro JG, Oude Elferink R. An LPAR5-antagonist that reduces nociception and increases pruriception. FRONTIERS IN PAIN RESEARCH 2022; 3:963174. [PMID: 35959236 PMCID: PMC9360597 DOI: 10.3389/fpain.2022.963174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 07/01/2022] [Indexed: 11/13/2022] Open
Abstract
Introduction The G-protein coupled receptor LPAR5 plays a prominent role in LPA-mediated pain and itch signaling. In this study we focus on the LPAR5-antagonist compound 3 (cpd3) and its ability to affect pain and itch signaling, both in vitro and in vivo. Methods Nociceptive behavior in wild type mice was induced by formalin, carrageenan or prostaglandin E2 (PGE2) injection in the hind paw, and the effect of oral cpd3 administration was measured. Scratch activity was measured after oral administration of cpd3, in mice overexpressing phospholipase A2 (sPLA2tg), in wild type mice (WT) and in TRPA1-deficient mice (Trpa1 KO). In vitro effects of cpd3 were assessed by measuring intracellular calcium release in HMC-1 and HEK-TRPA1 cells. Results As expected, nociceptive behavior (induced by formalin, carrageenan or PGE2) was reduced after treatment with cpd3. Unexpectedly, cpd3 induced scratch activity in mice. In vitro addition of cpd3 to HEK-TRPA1 cells induced an intracellular calcium wave that could be inhibited by the TRPA1-antagonist A-967079. In Trpa1 KO mice, however, the increase in scratch activity after cpd3 administration was not reduced. Conclusions Cpd3 has in vivo antinociceptive effects but induces scratch activity in mice, probably by activation of multiple pruriceptors, including TRPA1. These results urge screening of antinociceptive candidate drugs for activity with pruriceptors.
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Affiliation(s)
- Jacqueline Langedijk
- Amsterdam University Medical Centers (UMC), Tytgat Institute for Liver and Intestinal Research, University of Amsterdam, Research Institute Amsterdam Gastroenterology, Endocrinology and Metabolism (AG&M), Amsterdam, Netherlands
| | - Erika Ivanna Araya
- Department of Pharmacology, Biological Sciences Sector, Federal University of Parana, Curitiba, Brazil
| | - Amanda Ribeiro Barroso
- Department of Pharmacology, Biological Sciences Sector, Federal University of Parana, Curitiba, Brazil
| | - Dagmar Tolenaars
- Amsterdam University Medical Centers (UMC), Tytgat Institute for Liver and Intestinal Research, University of Amsterdam, Research Institute Amsterdam Gastroenterology, Endocrinology and Metabolism (AG&M), Amsterdam, Netherlands
| | - Marc Nazaré
- Departments of Chemical Biology and Structural Biology, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | - Hassane Belabed
- Departments of Chemical Biology and Structural Biology, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | - Jens Schoene
- Departments of Chemical Biology and Structural Biology, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | | | - Ronald Oude Elferink
- Amsterdam University Medical Centers (UMC), Tytgat Institute for Liver and Intestinal Research, University of Amsterdam, Research Institute Amsterdam Gastroenterology, Endocrinology and Metabolism (AG&M), Amsterdam, Netherlands
- *Correspondence: Ronald Oude Elferink
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Steyaert A, Lenoir C, Lavand’homme P, van den Broeke EN, Mouraux A. Multichannel transcranial direct current stimulation over the left dorsolateral prefrontal cortex may modulate the induction of secondary hyperalgesia, a double-blinded cross-over study in healthy volunteers. PLoS One 2022; 17:e0270047. [PMID: 35709234 PMCID: PMC9202873 DOI: 10.1371/journal.pone.0270047] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Accepted: 06/02/2022] [Indexed: 11/18/2022] Open
Abstract
Background Central sensitization is thought to play a critical role in the development of chronic pain, and secondary mechanical hyperalgesia is considered one of its hall-mark features. Consequently, interventions capable of modulating its development could have important therapeutic value. Non-invasive neuromodulation of the left dorsolateral prefrontal cortex (DLPFC) has shown potential to reduce pain, both in healthy volunteers and in patients. Whether it can modulate the induction of central sensitization, however, is less well known. Objective To determine whether multifocal transcranial direct current stimulation (tDCS) targeting the left DLPFC affects the development of secondary mechanical hyperalgesia. Methods In this within-subjects, cross-over, double-blinded study, eighteen healthy volunteers participated in three experimental sessions. After 20 minutes of either anodal, cathodal, or sham multichannel tDCS over the left DLPFC, secondary mechanical hyperalgesia was induced using high-frequency electrical stimulation (HFS) of the volar forearm. We assessed intensity of perception to 128 mN mechanical pinprick stimuli at baseline and up to 240 minutes after HFS. We also mapped the area of mechanical hyperalgesia. Results HFS resulted in a robust and unilateral increase in the intensity of perception to mechanical pinprick stimuli at the HFS arm, which was not different between tDCS stimulation conditions. However, the area of hyperalgesia was reduced after anodal tDCS compared to sham. Conclusion Anodal tDCS over the left DLPFC modestly modulates the size of the HFS-induced area of secondary mechanical hyperalgesia, suggesting that non-invasive neuromodulation targeting the left DLPFC may be a potential intervention to limit the development of central sensitization.
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Affiliation(s)
- Arnaud Steyaert
- Institute of Neuroscience (IONS), Université catholique de Louvain (UCLouvain), Brussels, Belgium
- Departement of Anaesthesiology, Cliniques Universitaires Saint-Luc, Brussels, Belgium
- * E-mail:
| | - Cédric Lenoir
- Institute of Neuroscience (IONS), Université catholique de Louvain (UCLouvain), Brussels, Belgium
| | - Patricia Lavand’homme
- Institute of Neuroscience (IONS), Université catholique de Louvain (UCLouvain), Brussels, Belgium
- Departement of Anaesthesiology, Cliniques Universitaires Saint-Luc, Brussels, Belgium
| | | | - André Mouraux
- Institute of Neuroscience (IONS), Université catholique de Louvain (UCLouvain), Brussels, Belgium
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7
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Sandri A, Cecchini MP, Zanini A, Nocini R, Boschi F, Zanette G, Marcon A, Fiorio M, Tinazzi M. Unpleasant olfactory and gustatory stimuli increase pain unpleasantness in patients with chronic oral burning pain: an exploratory study. Eur J Pain 2022; 26:1094-1106. [PMID: 35279917 PMCID: PMC9313804 DOI: 10.1002/ejp.1933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Background Despite mounting evidence for the powerful influence of smell and taste substances in experimental pain, our knowledge of their effects in the clinical context is scarce, especially for patients with chronic oral burning pain. To fill this gap, we investigated the effect of olfactory and gustatory stimuli on pain perception in patients with chronic oral burning pain, a disabling condition that is difficult to manage and treat. Methods Twenty‐two patients with chronic oral burning pain underwent testing with a variety of olfactory and gustatory substances (pleasant, neutral, unpleasant) in multisensory interaction. The order of testing was randomized. Perception of pain intensity and unpleasantness was evaluated on a numerical rating scale at baseline and immediately after each test trial. Results Pain unpleasantness but not pain intensity was found to be modulated by chemosensory stimuli. Unpleasant olfactory and gustatory stimuli increased the perception of pain unpleasantness compared to pleasant and neutral stimuli. Pain unpleasantness after unpleasant olfactory and gustatory stimuli correlated with psychological questionnaire subscale scores for distress (CORE‐OM) and emotional awareness (TAS‐20). Conclusions Our findings suggest a role of unpleasant chemosensory stimuli in increasing the perception of pain unpleasantness in patients with chronic oral burning. The lack of an effect on pain intensity indicates a dissociation between sensory and affective pain components. Future research is needed to further study the association between chemosensory stimuli and emotional and subjective aspects in modulating chronic oral burning pain. Significance This exploratory work suggests that unpleasant smell and taste stimuli may have an adverse effect on the affective component of chronic oral burning pain. Future comprehensive large‐scale research, also applying brain imaging investigations as well as full psychological analysis, is required to better understand the role of smell and taste stimuli on this chronic and disabling pain condition.
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Affiliation(s)
- Angela Sandri
- Department of Neurosciences, Biomedicine and Movement Sciences Neurology Unit University of Verona Verona Italy
| | - Maria Paola Cecchini
- Department of Neurosciences, Biomedicine and Movement Sciences, Anatomy and Histology Section University of Verona Verona Italy
| | - Alice Zanini
- Department of Neurosciences, Biomedicine and Movement Sciences, Anatomy and Histology Section University of Verona Verona Italy
| | - Riccardo Nocini
- Department of Surgery Dentistry, Paediatrics and Gynaecology, Otolaryngology Section University of Verona Verona Italy
| | - Federico Boschi
- Department of Computer Science University of Verona Verona Italy
| | - Giovanni Zanette
- Italian Scientific Society of Clinical Hypnosis in Psychotherapy and Humanistic Medicine SIPMU Verona Italy
| | - Alessandro Marcon
- Department of Diagnostics and Public Health Unit of Epidemiology and Medical Statistics University of Verona Verona Italy
| | - Mirta Fiorio
- Department of Neurosciences, Biomedicine and Movement Sciences Movement Sciences Section University of Verona Verona Italy
| | - Michele Tinazzi
- Department of Neurosciences, Biomedicine and Movement Sciences Neurology Unit University of Verona Verona Italy
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Falsetta ML, Wood RW, Linder MA, Bonham AD, Honn KV, Maddipati KR, Phipps RP, Haidaris CG, Foster DC. Specialized Pro-resolving Mediators Reduce Pro-nociceptive Inflammatory Mediator Production in Models of Localized Provoked Vulvodynia. THE JOURNAL OF PAIN 2021; 22:1195-1209. [PMID: 33813057 PMCID: PMC8484336 DOI: 10.1016/j.jpain.2021.03.144] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 03/05/2021] [Accepted: 03/24/2021] [Indexed: 12/25/2022]
Abstract
Localized provoked vulvodynia (LPV) is the most common cause of chronic dyspareunia in premenopausal women, characterized by pain with light touch to the vulvar vestibule surrounding the vaginal opening. The devastating impact of LPV includes sexual dysfunction, infertility, depression, and even suicide. Yet, its etiology is unclear. No effective medical therapy exists; surgical removal of the painful vestibule is the last resort. In LPV, the vestibule expresses a unique inflammatory profile with elevated levels of pro-nociceptive proinflammatory mediators prostaglandin E2 (PGE2) and interleukin-6 (IL-6), which are linked to lower mechanical sensitivity thresholds. Specialized pro-resolving mediators (SPMs), lipids produced endogenously within the body, hold promise as an LPV treatment by resolving inflammation without impairing host defense. Ten of 13 commercially available SPMs reduced IL-6 and PGE2 production by vulvar fibroblasts, administered either before or after inflammatory stimulation. Using a murine vulvar pain model, coupling proinflammatory mediator quantification with mechanical sensitivity threshold determination, topical treatment with the SPM, maresin 1, decreased sensitivity and suppressed PGE2 levels. Docosahexaenoic acid, a precursor of maresin 1, was also effective in reducing PGE2 in vulvar fibroblasts and rapidly restored mouse sensitivity thresholds. Overall, SPMs and their precursors may be a safe and efficacious for LPV. Perspective: Vulvodynia, like many pain conditions, is difficult to treat because disease origins are incompletely understood. Here, we applied our knowledge of more recently discovered vulvodynia disease mechanisms to screen novel therapeutics. We identified several specialized pro-resolving mediators as likely potent and safe for treating LPV with potential for broader application.
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Affiliation(s)
- Megan L Falsetta
- Department of Obstetrics and Gynecology, University of Rochester, School of Medicine and Dentistry Rochester, New York; Department of Pharmacology and Physiology, University of Rochester, School of Medicine and Dentistry, Rochester, New York.
| | - Ronald W Wood
- Department of Obstetrics and Gynecology, University of Rochester, School of Medicine and Dentistry Rochester, New York
| | - Mitchell A Linder
- Department of Obstetrics and Gynecology, University of Rochester, School of Medicine and Dentistry Rochester, New York
| | - Adrienne D Bonham
- Department of Obstetrics and Gynecology, University of Rochester, School of Medicine and Dentistry Rochester, New York
| | - Kenneth V Honn
- Department of Pathology, Wayne State University, School of Medicine, Detroit, Michigan
| | - Krishna Rao Maddipati
- Department of Pathology, Wayne State University, School of Medicine, Detroit, Michigan
| | | | - Constantine G Haidaris
- Department of Microbiology and Immunology, University of Rochester, School of Medicine and Dentistry Rochester, New York
| | - David C Foster
- Department of Obstetrics and Gynecology, University of Rochester, School of Medicine and Dentistry Rochester, New York
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Springborg AD, Wessel CR, Andersen LPK, Werner MU. Methodology and applicability of the human contact burn injury model: A systematic review. PLoS One 2021; 16:e0254790. [PMID: 34329326 PMCID: PMC8323928 DOI: 10.1371/journal.pone.0254790] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 07/06/2021] [Indexed: 11/24/2022] Open
Abstract
The contact burn injury model is an experimental contact thermode-based physiological pain model primarily applied in research of drug efficacy in humans. The employment of the contact burn injury model across studies has been inconsistent regarding essential methodological variables, challenging the validity of the model. This systematic review analyzes methodologies, outcomes, and research applications of the contact burn injury model. Based on these results, we propose an improved contact burn injury testing paradigm. A literature search was conducted (15-JUL-2020) using PubMed, EMBASE, Web of Science, and Google Scholar. Sixty-four studies were included. The contact burn injury model induced consistent levels of primary and secondary hyperalgesia. However, the analyses revealed variations in the methodology of the contact burn injury heating paradigm and the post-burn application of test stimuli. The contact burn injury model had limited testing sensitivity in demonstrating analgesic efficacy. There was a weak correlation between experimental and clinical pain intensity variables. The data analysis was limited by the methodological heterogenicity of the different studies and a high risk of bias across the studies. In conclusion, although the contact burn injury model provides robust hyperalgesia, it has limited efficacy in testing analgesic drug response. Recommendations for future use of the model are being provided, but further research is needed to improve the sensitivity of the contact burn injury method. The protocol for this review has been published in PROSPERO (ID: CRD42019133734).
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Affiliation(s)
- Anders Deichmann Springborg
- Department of Anesthesia, Multidisciplinary Pain Center, Pain and Respiratory Support, Neuroscience Center, Copenhagen University Hospital, Copenhagen, Denmark
- * E-mail:
| | - Caitlin Rae Wessel
- Department of Physiology, University of Kentucky, Lexington, KY, United States of America
| | - Lars Peter Kloster Andersen
- Department of Anaesthesia and Intensive Care, Bispebjerg and Frederiksberg Hospital, University of Copenhagen, Copenhagen, Denmark
| | - Mads Utke Werner
- Department of Anesthesia, Multidisciplinary Pain Center, Pain and Respiratory Support, Neuroscience Center, Copenhagen University Hospital, Copenhagen, Denmark
- Department of Clinical Sciences, Lund University, Lund, Sweden
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10
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Hijma HJ, Groeneveld GJ. Analgesic drug development: proof-of-mechanism and proof-of-concept in early phase clinical studies. MEDICINE IN DRUG DISCOVERY 2021. [DOI: 10.1016/j.medidd.2021.100083] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
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Modality-specific facilitation of noninjurious sharp mechanical pain by topical capsaicin. Pain 2021; 162:275-286. [PMID: 32701656 DOI: 10.1097/j.pain.0000000000002020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We had previously shown that a "blunt blade" stimulator can mimic the noninjurious strain phase of incisional pain, but not its sustained duration. Here, we tested whether acute sensitization of the skin with topical capsaicin can add the sustained phase to this noninvasive surrogate model of intraoperative pain. Altogether, 110 healthy volunteers (55 male and 55 female; 26 ± 5 years) participated in several experiments using the "blunt blade" (0.25 × 4 mm) on normal skin (n = 36) and on skin pretreated by a high-concentration capsaicin patch (8%, Qutenza; n = 36). These data were compared with an experimental incision (n = 40) using quantitative and qualitative pain ratings by numerical rating scale and SES Pain Perception Scale descriptors. Capsaicin sensitization increased blade-induced pain magnitude and duration significantly (both P < 0.05), but it failed to fully match the sustained duration of incisional pain. In normal skin, the SES pattern of pain qualities elicited by the blade matched incision in pain magnitude and pattern of pain descriptors. In capsaicin-treated skin, the blade acquired a significant facilitation only of the perceived heat pain component (P < 0.001), but not of mechanical pain components. Thus, capsaicin morphed the descriptor pattern of the blade to become more capsaicin-like, which is probably explained best by peripheral sensitization of the TRPV1 receptor. Quantitative sensory testing in capsaicin-sensitized skin revealed hyperalgesia to heat and pressure stimuli, and loss of cold and cold pain sensitivity. These findings support our hypothesis that the blade models the early tissue-strain-related mechanical pain phase of surgical incisions.
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12
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Quesada C, Kostenko A, Ho I, Leone C, Nochi Z, Stouffs A, Wittayer M, Caspani O, Brix Finnerup N, Mouraux A, Pickering G, Tracey I, Truini A, Treede RD, Garcia-Larrea L. Human surrogate models of central sensitization: A critical review and practical guide. Eur J Pain 2021; 25:1389-1428. [PMID: 33759294 PMCID: PMC8360051 DOI: 10.1002/ejp.1768] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 03/17/2021] [Accepted: 03/21/2021] [Indexed: 12/11/2022]
Abstract
Background As in other fields of medicine, development of new medications for management of neuropathic pain has been difficult since preclinical rodent models do not necessarily translate to the clinics. Aside from ongoing pain with burning or shock‐like qualities, neuropathic pain is often characterized by pain hypersensitivity (hyperalgesia and allodynia), most often towards mechanical stimuli, reflecting sensitization of neural transmission. Data treatment We therefore performed a systematic literature review (PubMed‐Medline, Cochrane, WoS, ClinicalTrials) and semi‐quantitative meta‐analysis of human pain models that aim to induce central sensitization, and generate hyperalgesia surrounding a real or simulated injury. Results From an initial set of 1569 reports, we identified and analysed 269 studies using more than a dozen human models of sensitization. Five of these models (intradermal or topical capsaicin, low‐ or high‐frequency electrical stimulation, thermode‐induced heat‐injury) were found to reliably induce secondary hyperalgesia to pinprick and have been implemented in multiple laboratories. The ability of these models to induce dynamic mechanical allodynia was however substantially lower. The proportion of subjects who developed hypersensitivity was rarely provided, giving rise to significant reporting bias. In four of these models pharmacological profiles allowed to verify similarity to some clinical conditions, and therefore may inform basic research for new drug development. Conclusions While there is no single “optimal” model of central sensitization, the range of validated and easy‐to‐use procedures in humans should be able to inform preclinical researchers on helpful potential biomarkers, thereby narrowing the translation gap between basic and clinical data. Significance Being able to mimic aspects of pathological pain directly in humans has a huge potential to understand pathophysiology and provide animal research with translatable biomarkers for drug development. One group of human surrogate models has proven to have excellent predictive validity: they respond to clinically active medications and do not respond to clinically inactive medications, including some that worked in animals but failed in the clinics. They should therefore inform basic research for new drug development.
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Affiliation(s)
- Charles Quesada
- NeuroPain lab, Lyon Centre for Neuroscience Inserm U1028, Lyon, France.,Pain Center Neurological Hospital (CETD), Hospices Civils de Lyon, Lyon, France
| | - Anna Kostenko
- Department of Neurophysiology, Mannheim center for Translational Neurosciences, Heidelberg University, Heidelberg, Germany
| | - Idy Ho
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Caterina Leone
- Department of Human Neuroscience, Sapienza University, Rome, Italy
| | - Zahra Nochi
- Danish Pain Research Center, Dept of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Alexandre Stouffs
- Institute of Neuroscience (IoNS), Université Catholique de Louvain (UCLouvain), Ottignies-Louvain-la-Neuve, Belgium
| | - Matthias Wittayer
- Department of Neurophysiology, Mannheim center for Translational Neurosciences, Heidelberg University, Heidelberg, Germany
| | - Ombretta Caspani
- Department of Neurophysiology, Mannheim center for Translational Neurosciences, Heidelberg University, Heidelberg, Germany
| | - Nanna Brix Finnerup
- Danish Pain Research Center, Dept of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - André Mouraux
- Institute of Neuroscience (IoNS), Université Catholique de Louvain (UCLouvain), Ottignies-Louvain-la-Neuve, Belgium
| | | | - Irene Tracey
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Andrea Truini
- Department of Human Neuroscience, Sapienza University, Rome, Italy
| | - Rolf-Detlef Treede
- Department of Neurophysiology, Mannheim center for Translational Neurosciences, Heidelberg University, Heidelberg, Germany
| | - Luis Garcia-Larrea
- NeuroPain lab, Lyon Centre for Neuroscience Inserm U1028, Lyon, France.,Pain Center Neurological Hospital (CETD), Hospices Civils de Lyon, Lyon, France
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13
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Sandri A, Cecchini MP, Riello M, Zanini A, Nocini R, Fiorio M, Tinazzi M. Pain, Smell, and Taste in Adults: A Narrative Review of Multisensory Perception and Interaction. Pain Ther 2021; 10:245-268. [PMID: 33635507 PMCID: PMC8119564 DOI: 10.1007/s40122-021-00247-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 02/13/2021] [Indexed: 12/31/2022] Open
Abstract
Every day our sensory systems perceive and integrate a variety of stimuli containing information vital for our survival. Pain acts as a protective warning system, eliciting a response to remove harmful stimuli; it may also be a symptom of an illness or present as a disease itself. There is a growing need for additional pain-relieving therapies involving the multisensory integration of smell and taste in pain modulation, an approach that may provide new strategies for the treatment and management of pain. While pain, smell, and taste share common features and are strongly linked to emotion and cognition, their interaction has been poorly explored. In this review, we provide an overview of the literature on pain modulation by olfactory and gustatory substances. It includes adult human studies investigating measures of pain threshold, tolerance, intensity, and/or unpleasantness. Due to the limited number of studies currently available, we have structured this review as a narrative in which we comment on experimentally induced and clinical pain separately on pain–smell and pain–taste interaction. Inconsistent study findings notwithstanding, pain, smell, and taste seem to interact at both the behavioral and the neural levels. Pain intensity and unpleasantness seem to be affected more by olfactory substances, whereas pain threshold and tolerance are influenced by gustatory substances. Few pilot studies to date have investigated these effects in clinical populations. While the current results are promising for the future, more evidence is needed to elucidate the link between the chemical senses and pain. Doing so has the potential to improve and develop novel options for pain treatment.
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Affiliation(s)
- Angela Sandri
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy.
| | - Maria Paola Cecchini
- Anatomy and Histology Section, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Marianna Riello
- Neurology Unit, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Alice Zanini
- Anatomy and Histology Section, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Riccardo Nocini
- Otolaryngology Section, Department of Surgery, Dentistry, Paediatrics and Gynaecology , University of Verona, Verona, Italy
| | - Mirta Fiorio
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Michele Tinazzi
- Neurology Unit, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy.
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14
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Springborg AD, Jensen EK, Kreilgaard M, Petersen MA, Papathanasiou T, Lund TM, Taylor BK, Werner MU. High-dose naloxone: Effects by late administration on pain and hyperalgesia following a human heat injury model. A randomized, double-blind, placebo-controlled, crossover trial with an enriched enrollment design. PLoS One 2020; 15:e0242169. [PMID: 33180816 PMCID: PMC7660513 DOI: 10.1371/journal.pone.0242169] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 10/27/2020] [Indexed: 11/18/2022] Open
Abstract
Severe chronic postsurgical pain has a prevalence of 4–10% in the surgical population. The underlying nociceptive mechanisms have not been well characterized. Following the late resolution phase of an inflammatory injury, high-dose μ-opioid-receptor inverse agonists reinstate hypersensitivity to nociceptive stimuli. This unmasking of latent pain sensitization has been a consistent finding in rodents while only observed in a limited number of human volunteers. Latent sensitization could be a potential triggering venue in chronic postsurgical pain. The objective of the present trial was in detail to examine the association between injury-induced secondary hyperalgesia and naloxone-induced unmasking of latent sensitization. Healthy volunteers (n = 80) received a cutaneous heat injury (47°C, 420 s, 12.5 cm2). Baseline secondary hyperalgesia areas were assessed 1 h post-injury. Utilizing an enriched enrollment design, subjects with a magnitude of secondary hyperalgesia areas in the upper quartile (‘high-sensitizers’ [n = 20]) and the lower quartile (‘low-sensitizers’ [n = 20]) were selected for further study. In four consecutive experimental sessions (Sessions 1 to 4), the subjects at two sessions (Sessions 1 and 3) received a cutaneous heat injury followed 168 h later (Sessions 2 and 4) by a three-step target-controlled intravenous infusion of naloxone (3.25 mg/kg), or normal saline. Assessments of secondary hyperalgesia areas were made immediately before and stepwise during the infusions. Simple univariate statistics revealed no significant differences in secondary hyperalgesia areas between naloxone and placebo treatments (P = 0.215), or between ‘high-sensitizers’ and ‘low-sensitizers’ (P = 0.757). In a mixed-effects model, secondary hyperalgesia areas were significantly larger following naloxone as compared to placebo for ‘high-sensitizers’ (P < 0.001), but not ‘low-sensitizers’ (P = 0.651). Although we could not unequivocally demonstrate naloxone-induced reinstatement of heat injury-induced hyperalgesia, further studies in clinical postsurgical pain models are warranted.
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Affiliation(s)
| | | | - Mads Kreilgaard
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Morten Aagaard Petersen
- The Research Unit, Department of Palliative Medicine, Copenhagen University Hospitals, Copenhagen, Denmark
| | - Theodoros Papathanasiou
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Trine Meldgaard Lund
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Bradley Kenneth Taylor
- Department of Anesthesiology, Pittsburgh Center for Pain Research, and the Pittsburgh Project to End Opioid Misuse, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Mads Utke Werner
- Neuroscience Center, Copenhagen University Hospitals, Copenhagen, Denmark
- Department of Clinical Sciences, Lund University, Lund, Sweden
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15
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Cecchini MP, Riello M, Sandri A, Zanini A, Fiorio M, Tinazzi M. Smell and taste dissociations in the modulation of tonic pain perception induced by a capsaicin cream application. Eur J Pain 2020; 24:1946-1955. [PMID: 32780473 DOI: 10.1002/ejp.1644] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 08/04/2020] [Accepted: 08/05/2020] [Indexed: 12/12/2022]
Abstract
BACKGROUND Pain is a subjective experience characterized by sensory (intensity) and emotional (unpleasantness) aspects. Although literature reports behavioural effects on pain due to smell and taste influence, to our knowledge the relationship between tonic pain induced by a capsaicin cream and these chemosensory systems has never been explored before. The aim of this study was to investigate the modulation of olfactory and gustatory substances having different valence on tonic pain perception mediated by a capsaicin cream application. METHODS Sixty healthy volunteers were included in two separated experiments (N = 30 smell; N = 30 taste) and underwent different valence smell and taste stimulations, while receiving painful stimuli. Perception of pain intensity (the sensory component) and unpleasantness (the affective component) was measured with a numerical rating scale, both during the two aforementioned experiments. RESULTS Pain unpleasantness rating showed differences only in the smell experiment between the two odourous conditions. In particular, pleasant odour induced lower ratings of pain unpleasantness, while no significant results were found for intensity. Regarding taste, we could not observe significant effects nor for pain unpleasantness or intensity. CONCLUSIONS These findings highlight the potential role of pleasant odours in influencing the affective aspects of pain perception induced by this kind of tonic pain. Such evidence might provide new insight for using chemosensory substances as analgesics for modulating the cognitive aspects of neuropathic pain. SIGNIFICANCE This work shows the effect of smell on the emotional component of tonic pain, experimentally induced by capsaicin cream application. Previous literature investigated tonic pain in interaction with smell and/or taste stimuli, but mainly with physical methods such as temperature. Our findings add new information in this field, contributing to a deeper insight on the role of olfaction on this particular kind of tonic pain perception. This approach could open to new investigations aimed to consider odours for pain management.
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Affiliation(s)
- Maria Paola Cecchini
- Anatomy and Histology Section, Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Marianna Riello
- Neurology Unit, Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Angela Sandri
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Alice Zanini
- Anatomy and Histology Section, Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Mirta Fiorio
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Michele Tinazzi
- Neurology Unit, Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
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16
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Mooney ER, Davies AJ, Pickering AE. Sweet taste does not modulate pain perception in adult humans. Wellcome Open Res 2020; 5:43. [PMID: 32704547 PMCID: PMC7361508 DOI: 10.12688/wellcomeopenres.15726.2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/01/2020] [Indexed: 01/07/2023] Open
Abstract
Background: Sugar is routinely used to comfort neonates undergoing painful procedures, and animal studies have shown that sucrose increases the time to withdrawal from painful stimuli. However, there are no published studies examining the effects of sweet substances on heat pain thresholds and percept in adult humans. Methods: Healthy adult volunteers (n=27, aged 18-48 years) were recruited to a controlled, double-blind, randomised, cross-over study to characterise the effect of tasting solutions of equivalent sweetness (10% sucrose and 0.016% sucralose) on warm detection and heat pain thresholds and the percept ratings of painfully hot stimuli. The effect of anticipation of a sweet taste on heat pain threshold was also assessed. Results: Tasting either sucrose or sucralose had no significant effect on the percept of an individually titrated hot stimulus (54.5±4.2 and 54.9±3.2 vs 53.2±3.5 for water, 0-100 visual analogue scale), on the warm detection or heat pain threshold (43.3±0.8, 43.2±0.8 vs 43.0±0.8°C). Anticipation of a sweet substance similarly did not affect heat pain thresholds. Conclusions: Sucrose and sucralose solutions had no analgesic effect when assessed using heat detection thresholds and percept ratings of painfully hot stimuli despite being perceived as sweeter and more pleasant than water. These findings are in contrast to results reported from previous animal studies in which thermal analgesia from sweet solutions is robust. Given the ubiquitous availability of sugar rich drinks in the modern environment, the lack of observable effect may be due to an insufficient hedonic value of the test solutions when compared to the experience of a laboratory rodent. Alternatively, sweet tastes may have a specific effect on pain tolerance rather than the threshold and acute percept measures assayed in this study.
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Affiliation(s)
- Elizabeth R Mooney
- School of Physiology, Pharmacology & Neuroscience, Biomedical Sciences Building, University of Bristol, Bristol, BS8 1TD, UK,Anaesthesia, Pain & Critical Care Sciences, Translational Health Sciences, Bristol Medical School, University of Bristol, Level 7, Bristol Royal Infirmary, Bristol, BS2 8HW, UK
| | - Alexander J Davies
- Nuffield Department of Clinical Neuroscience, University of Oxford, Level 6 West Wing, John Radcliffe Hospital, Oxford, OX3 9DU, UK
| | - Anthony E Pickering
- School of Physiology, Pharmacology & Neuroscience, Biomedical Sciences Building, University of Bristol, Bristol, BS8 1TD, UK,Anaesthesia, Pain & Critical Care Sciences, Translational Health Sciences, Bristol Medical School, University of Bristol, Level 7, Bristol Royal Infirmary, Bristol, BS2 8HW, UK,
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17
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Mooney ER, Davies AJ, Pickering AE. Sweet taste does not modulate pain perception in adult humans. Wellcome Open Res 2020; 5:43. [PMID: 32704547 PMCID: PMC7361508 DOI: 10.12688/wellcomeopenres.15726.1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/02/2020] [Indexed: 01/07/2023] Open
Abstract
Background: It is commonly observed that humans who are in pain or discomfort seek solace in the form of sweet foods and drinks. Sugar is routinely used to comfort neonates undergoing painful procedures, and animal studies have shown that sucrose increases the time to withdrawal from painful stimuli. However, there are no published studies examining the effects of sweet substances on heat pain thresholds and percept in adult humans. Methods: Healthy adult volunteers (n=27, aged 18-48 years) were recruited to a controlled, double-blind, randomised, cross-over study to characterise the effect of tasting solutions of equivalent sweetness (10% sucrose and 0.016% sucralose) on warm detection and heat pain thresholds and the percept ratings of painfully hot stimuli. The effect of anticipation of a sweet taste on heat pain threshold was also assessed. Results: Tasting either sucrose or sucralose had no significant effect on the percept of an individually titrated hot stimulus (54.5±4.2 and 54.9±3.2 vs 53.2±3.5 for water, 0-100 visual analogue scale), on the warm detection or heat pain threshold (43.3±0.8, 43.2±0.8 vs 43.0±0.8°C). Anticipation of a sweet substance similarly did not affect heat pain thresholds. Conclusions: Sucrose and sucralose solutions had no analgesic effect when assessed using heat detection thresholds and percept ratings of painfully hot stimuli despite being perceived as sweeter and more pleasant than water. These findings are in contrast to results reported from previous animal studies in which thermal analgesia from sweet solutions is robust. Given the ubiquitous availability of sugar rich drinks in the modern environment, the lack of observable effect may be due to an insufficient hedonic value of the test solutions when compared to the experience of a laboratory rodent. Alternatively, sweet tastes may have a specific effect on pain tolerance rather than the threshold and acute percept measures assayed in this study.
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Affiliation(s)
- Elizabeth R Mooney
- School of Physiology, Pharmacology & Neuroscience, Biomedical Sciences Building, University of Bristol, Bristol, BS8 1TD, UK,Anaesthesia, Pain & Critical Care Sciences, Translational Health Sciences, Bristol Medical School, University of Bristol, Level 7, Bristol Royal Infirmary, Bristol, BS2 8HW, UK
| | - Alexander J Davies
- Nuffield Department of Clinical Neuroscience, University of Oxford, Level 6 West Wing, John Radcliffe Hospital, Oxford, OX3 9DU, UK
| | - Anthony E Pickering
- School of Physiology, Pharmacology & Neuroscience, Biomedical Sciences Building, University of Bristol, Bristol, BS8 1TD, UK,Anaesthesia, Pain & Critical Care Sciences, Translational Health Sciences, Bristol Medical School, University of Bristol, Level 7, Bristol Royal Infirmary, Bristol, BS2 8HW, UK,
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18
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Nociceptive Threshold of Calves and Goat Kids Undergoing Injection of Clove Oil or Isoeugenol for Disbudding. Animals (Basel) 2020; 10:ani10071228. [PMID: 32698304 PMCID: PMC7401653 DOI: 10.3390/ani10071228] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 07/01/2020] [Accepted: 07/06/2020] [Indexed: 12/20/2022] Open
Abstract
Simple Summary Hot-iron disbudding in calves and goat kids is a widespread husbandry procedure involving pain and, especially in goats, the risk of brain damage. The injection of clove oil under the horn bud is a potential alternative disbudding method. Clove oil, with its active substance eugenol, is cytotoxic but has anaesthetic effects, and the injection of clove oil, or the pure substance isoeugenol, under the horn bud to stop horn growth may have potential welfare benefits compared to hot-iron disbudding. We compared the injection of clove oil with the injection of isoeugenol under the horn bud with respect to pain sensitivity in this area in the first 24 h after injection. Compared to before injection, the pain sensitivity of goats kids was higher 24 h after injection of clove oil and up to at least 6 h after isoeugenol injection, while, in calves, pain sensitivity was highest after 9 h. Future studies should compare the welfare effects of isoeugenol injection with hot-iron disbudding. Abstract In this preliminary study, we compared changes in mechanical nociceptive thresholds (MNT) of calves and goat kids injected with clove oil or isoeugenol under the horn bud as a potential, more welfare-friendly alternative to hot-iron disbudding. Twenty male calves and goat kids were randomly allocated to clove oil (n = 10 per species) or isoeugenol (n = 10 per species) injection under the horn buds. MNT was measured via a pressure algometer in calves and kids at several locations around the horn buds at several time points before and up to 24 h after injection. In kids, von Frey filaments were used additionally at the same time points. In calves, linear mixed models revealed an effect on MNT of time point (p = 0.010) and side (p = 0.007), but not of injection (p = 0.298), nor of the interaction ‘injection*time point’, MNT waslowest 9 h post-injection. In goats, there was an effect of injection depending on time point (interaction injection*time point, p = 0.03) with MNT being lowest 24 h post-injection for clove oil, while MNT was similar to pre-injection in isoeugenol. In both species, variation in the individual response post-injection was very high. Our results suggest that clove oil and isoeugenol induced hypersensitivity, which was higher for clove oil, in goat kids, but they also suggest a transient anaesthetic effect in some animals and locations.
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19
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Smith MT, Remeniuk B, Finan PH, Speed TJ, Tompkins DA, Robinson M, Gonzalez K, Bjurstrom MF, Irwin MR. Sex differences in measures of central sensitization and pain sensitivity to experimental sleep disruption: implications for sex differences in chronic pain. Sleep 2020; 42:5146314. [PMID: 30371854 DOI: 10.1093/sleep/zsy209] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Indexed: 01/11/2023] Open
Abstract
Study Objectives Females demonstrate heightened central sensitization (CS), a risk factor for chronic pain characterized by enhanced responsivity of central nervous system nociceptors to normal or subthreshold input. Sleep disruption increases pain sensitivity, but sex has rarely been evaluated as a moderator and few experiments have measured CS. We evaluated whether two nights of sleep disruption alter CS measures of secondary hyperalgesia and mechanical temporal summation in a sex-dependent manner. We also evaluated differences in measures of pain sensitivity. Methods Seventy-nine healthy adults (female n = 46) participated in a randomized crossover experiment comparing two consecutive nights of eight pseudorandomly distributed forced awakenings (FA [-200 min sleep time]) against two nights of undisturbed sleep (US). We conducted sensory testing the mornings following Night 2; the heat-capsaicin pain model was used to induce secondary hyperalgesia. Results FA reduced total sleep time (REM and NREM Stage 3) more profoundly in males. We observed divergent, sex-dependent effects of FA on secondary hyperalgesia and temporal summation. FA significantly increased secondary hyperalgesia in males and significantly increased temporal summation in females. Sex differences were not attributable to differential sleep loss in males. FA also significantly reduced heat-pain threshold and cold pressor pain tolerance, independently of sex. Conclusions Sleep disruption enhances different pain facilitatory measures of CS in males and females suggesting that sleep disturbance may increase risk for chronic pain in males and females via distinct pathways. Findings have implications for understanding sex differences in chronic pain and investigating sleep in chronic pain prevention efforts.
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Affiliation(s)
- Michael T Smith
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University, School of Medicine, Baltimore, MD
| | - Bethany Remeniuk
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University, School of Medicine, Baltimore, MD
| | - Patrick H Finan
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University, School of Medicine, Baltimore, MD
| | - Traci J Speed
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University, School of Medicine, Baltimore, MD
| | - D Andrew Tompkins
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University, School of Medicine, Baltimore, MD.,Department of Psychiatry, UCSF School of Medicine, San Francisco, CA
| | - Mercedes Robinson
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University, School of Medicine, Baltimore, MD
| | - Kaylin Gonzalez
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University, School of Medicine, Baltimore, MD
| | - Martin F Bjurstrom
- Department of Psychiatry and Behavioral Sciences, Cousins Center for Psychoneuroimmunology, UCLA Semel Institute for Neuroscience and Human Behavior, Los Angeles, CA
| | - Michael R Irwin
- Department of Psychiatry and Behavioral Sciences, Cousins Center for Psychoneuroimmunology, UCLA Semel Institute for Neuroscience and Human Behavior, Los Angeles, CA
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20
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Siebenga P, van Amerongen G, Hay JL, McDonnell A, Gorman D, Butt R, Groeneveld GJ. Lack of Detection of the Analgesic Properties of PF-05089771, a Selective Na v 1.7 Inhibitor, Using a Battery of Pain Models in Healthy Subjects. Clin Transl Sci 2019; 13:318-324. [PMID: 31642607 PMCID: PMC7070789 DOI: 10.1111/cts.12712] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 09/06/2019] [Indexed: 12/12/2022] Open
Abstract
Sodium channel blockers are used for the treatment of pain, but this is limited by the lack of selectivity for different sodium channel subtypes, which can result in central nervous system and cardiovascular side effects. As such, there is special interest in the Nav 1.7 subtype, which is expressed predominantly in nociceptive and sympathetic neurons. The aim was to demonstrate analgesic properties of a potent selective Nav 1.7 sodium channel blocker, PF-05089771, alone and concomitantly with pregabalin in healthy subjects using a battery of human evoked pain models. This was a double-blind, double-dummy, randomized, placebo-controlled, five-period cross-over study with PF-05089771 alone and PF-05089771 concomitantly with pregabalin as treatment arms with pregabalin, ibuprofen, and placebo as control arms (NCT02349607). A battery of human evoked pain models was used to investigate analgesic properties of PF-05089771. Twenty-five subjects were enrolled in the study of which 23 subjects completed all five periods. PF-05089771 alone did not differ from placebo on the primary pain end points. The same holds when comparing PF-05089771 concomitantly with pregabalin and pregabalin alone. Pregabalin showed significant effects relative to placebo on thermal pain on the normal skin and UVB skin (least squares means with 90% confidence interval: 0.63 (0.32-0.93) and 0.53 (0.11-0.96)), pressure stimulation (1.10 (1.04-1.18)), and cold pressor (1.22 (1.14-1.32)). Ibuprofen demonstrated significant effects on thermal pain UVB skin (1.26 (0.82-1.70)) and pressure stimulation assessment (1.08 (1.01-1.15)), consistent with historical results. This study did not demonstrate analgesic properties of PF-05089771 alone or concomitantly with pregabalin in a battery of pain models.
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Affiliation(s)
| | | | - Justin L Hay
- Centre for Human Drug Research, Leiden, The Netherlands
| | | | - Donal Gorman
- Neuroscience and Pain Research Unit, Pfizer WRD, Cambridge, UK
| | - Richard Butt
- Neuroscience and Pain Research Unit, Pfizer WRD, Cambridge, UK
| | - Geert Jan Groeneveld
- Centre for Human Drug Research, Leiden, The Netherlands.,Leiden University Medical Centre, Leiden, The Netherlands
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21
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Martin E, Narjoz C, Decleves X, Labat L, Lambert C, Loriot MA, Ducheix G, Dualé C, Pereira B, Pickering G. Dextromethorphan Analgesia in a Human Experimental Model of Hyperalgesia. Anesthesiology 2019; 131:356-368. [DOI: 10.1097/aln.0000000000002736] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Abstract
Editor’s Perspective
What We Already Know about This Topic
What This Article Tells Us That Is New
Background
Central pain sensitization is often refractory to drug treatment. Dextromethorphan, an N-methyl-d-aspartate receptor antagonist, is antihyperalgesic in preclinical pain models. The hypothesis is that dextromethorphan is also antihyperalgesic in humans.
Methods
This randomized, double-blind, placebo-controlled, crossover study explores the antihyperalgesic effect of single and repeated 30-mg dose of oral dextromethorphan in 20 volunteers, using the freeze-injury pain model. This model leads to development of primary and secondary hyperalgesia, which develops away from the site of injury and is associated with central sensitization and activation of N-methyl-d-aspartate receptor in the spinal cord. The primary outcome was antihyperalgesia calculated with the area under the curve of the percentage change in mechanical pain threshold (electronic von Frey) on the area of secondary hyperalgesia. The secondary outcomes were mechanical pain threshold on the area of primary hyperalgesia and cognitive (reaction time) effect.
Results
Single 30-mg results are reported. Antihyperalgesia (% · min) is significantly higher on the area of secondary hyperalgesia with dextromethorphan than placebo (median [interquartile range]: 3,029 [746; 6,195] vs. 710 [–3,248; 4,439], P = 0.009, Hedge’s g = 0.8, 95% CI [0.1; 1.4]). On primary hyperalgesia area, mechanical pain threshold 2 h after drug intake is significantly higher with dextromethorphan (P = 0.011, Hedge’s g = 0.63, 95% CI [0.01; 1.25]). No difference in antinociception is observed after thermal painful stimuli on healthy skin between groups. Reaction time (ms) is shorter with placebo than with dextromethorphan (median [interquartile range]: 21.6 [–37.4; 0.1] vs. –1.2 [–24.3; 15.4], P = 0.015, Hedge’s g = 0.75, 95% CI [0.12; 1.39]). Nonserious adverse events occurrence (15%, 3 of 20 volunteers) was similar in both groups.
Conclusions
This study shows that low-dose (30-mg) dextromethorphan is antihyperalgesic in humans on the areas of primary and secondary hyperalgesia and reverses peripheral and central neuronal sensitization. Because dextromethorphan had no intrinsic antinociceptive effect in acute pain on healthy skin, N-methyl-d-aspartate receptor may need to be sensitized by pain for dextromethorphan to be effective.
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Affiliation(s)
- E. Martin
- From University Clermont Auvergne, Department of Fundamental and Clinical Pharmacology of Pain, NeuroDol, F-63000 Clermont-Ferrand, France (E.M., C.D., G.P.); Inserm UMR-S1147, Saints-Pères University Centre, Paris, France (C.N., M.-A.L.); University Paris Descartes, Sorbonne Paris Cité, Paris, France (C.N., M.-A.L.); Assistance Publique—Paris Hospital (AP-HP), Georges Pompidou European Hospital,
| | - C. Narjoz
- From University Clermont Auvergne, Department of Fundamental and Clinical Pharmacology of Pain, NeuroDol, F-63000 Clermont-Ferrand, France (E.M., C.D., G.P.); Inserm UMR-S1147, Saints-Pères University Centre, Paris, France (C.N., M.-A.L.); University Paris Descartes, Sorbonne Paris Cité, Paris, France (C.N., M.-A.L.); Assistance Publique—Paris Hospital (AP-HP), Georges Pompidou European Hospital,
| | - X. Decleves
- From University Clermont Auvergne, Department of Fundamental and Clinical Pharmacology of Pain, NeuroDol, F-63000 Clermont-Ferrand, France (E.M., C.D., G.P.); Inserm UMR-S1147, Saints-Pères University Centre, Paris, France (C.N., M.-A.L.); University Paris Descartes, Sorbonne Paris Cité, Paris, France (C.N., M.-A.L.); Assistance Publique—Paris Hospital (AP-HP), Georges Pompidou European Hospital,
| | - L. Labat
- From University Clermont Auvergne, Department of Fundamental and Clinical Pharmacology of Pain, NeuroDol, F-63000 Clermont-Ferrand, France (E.M., C.D., G.P.); Inserm UMR-S1147, Saints-Pères University Centre, Paris, France (C.N., M.-A.L.); University Paris Descartes, Sorbonne Paris Cité, Paris, France (C.N., M.-A.L.); Assistance Publique—Paris Hospital (AP-HP), Georges Pompidou European Hospital,
| | - C. Lambert
- From University Clermont Auvergne, Department of Fundamental and Clinical Pharmacology of Pain, NeuroDol, F-63000 Clermont-Ferrand, France (E.M., C.D., G.P.); Inserm UMR-S1147, Saints-Pères University Centre, Paris, France (C.N., M.-A.L.); University Paris Descartes, Sorbonne Paris Cité, Paris, France (C.N., M.-A.L.); Assistance Publique—Paris Hospital (AP-HP), Georges Pompidou European Hospital,
| | - M.-A. Loriot
- From University Clermont Auvergne, Department of Fundamental and Clinical Pharmacology of Pain, NeuroDol, F-63000 Clermont-Ferrand, France (E.M., C.D., G.P.); Inserm UMR-S1147, Saints-Pères University Centre, Paris, France (C.N., M.-A.L.); University Paris Descartes, Sorbonne Paris Cité, Paris, France (C.N., M.-A.L.); Assistance Publique—Paris Hospital (AP-HP), Georges Pompidou European Hospital,
| | - G. Ducheix
- From University Clermont Auvergne, Department of Fundamental and Clinical Pharmacology of Pain, NeuroDol, F-63000 Clermont-Ferrand, France (E.M., C.D., G.P.); Inserm UMR-S1147, Saints-Pères University Centre, Paris, France (C.N., M.-A.L.); University Paris Descartes, Sorbonne Paris Cité, Paris, France (C.N., M.-A.L.); Assistance Publique—Paris Hospital (AP-HP), Georges Pompidou European Hospital,
| | - C. Dualé
- From University Clermont Auvergne, Department of Fundamental and Clinical Pharmacology of Pain, NeuroDol, F-63000 Clermont-Ferrand, France (E.M., C.D., G.P.); Inserm UMR-S1147, Saints-Pères University Centre, Paris, France (C.N., M.-A.L.); University Paris Descartes, Sorbonne Paris Cité, Paris, France (C.N., M.-A.L.); Assistance Publique—Paris Hospital (AP-HP), Georges Pompidou European Hospital,
| | - B. Pereira
- From University Clermont Auvergne, Department of Fundamental and Clinical Pharmacology of Pain, NeuroDol, F-63000 Clermont-Ferrand, France (E.M., C.D., G.P.); Inserm UMR-S1147, Saints-Pères University Centre, Paris, France (C.N., M.-A.L.); University Paris Descartes, Sorbonne Paris Cité, Paris, France (C.N., M.-A.L.); Assistance Publique—Paris Hospital (AP-HP), Georges Pompidou European Hospital,
| | - G. Pickering
- From University Clermont Auvergne, Department of Fundamental and Clinical Pharmacology of Pain, NeuroDol, F-63000 Clermont-Ferrand, France (E.M., C.D., G.P.); Inserm UMR-S1147, Saints-Pères University Centre, Paris, France (C.N., M.-A.L.); University Paris Descartes, Sorbonne Paris Cité, Paris, France (C.N., M.-A.L.); Assistance Publique—Paris Hospital (AP-HP), Georges Pompidou European Hospital,
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Raja SN, Sivanesan E, Guan Y. Central Sensitization, N-methyl-D-aspartate Receptors, and Human Experimental Pain Models: Bridging the Gap between Target Discovery and Drug Development. Anesthesiology 2019; 131:233-235. [PMID: 31233408 PMCID: PMC6640094 DOI: 10.1097/aln.0000000000002808] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
- Srinivasa N. Raja
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205, USA
| | - Eellan Sivanesan
- Department of Neurological Surgery, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Yun Guan
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205, USA
- Department of Neurological Surgery, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
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Siebenga PS, van Amerongen G, Okkerse P, Denney WS, Dua P, Butt RP, Hay JL, Groeneveld GJ. Reproducibility of a battery of human evoked pain models to detect pharmacological effects of analgesic drugs. Eur J Pain 2019; 23:1129-1140. [PMID: 30793411 PMCID: PMC6618124 DOI: 10.1002/ejp.1379] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 02/01/2019] [Accepted: 02/17/2019] [Indexed: 12/11/2022]
Abstract
BACKGROUND Although reproducibility is considered essential for any method used in scientific research, it is investigated only rarely; thus, strikingly little has been published regarding the reproducibility of evoked pain models involving human subjects. Here, we studied the reproducibility of a battery of evoked pain models for demonstrating the analgesic effects of two analgesic compounds. METHODS A total of 81 healthy subjects participated in four studies involving a battery of evoked pain tests in which mechanical, thermal and electrical stimuli were used to measure pain detection and tolerance thresholds. Pharmacodynamic outcome variables were analysed using a mixed model analysis of variance, and a coefficient of variation was calculated by dividing the standard deviation by the least squares means. RESULTS A total of 76 subjects completed the studies. After being administered pregabalin, the subjects' pain tolerance thresholds in the cold pressor and pressure stimulation tests were significantly increased compared to the placebo group. Moreover, the heat pain detection threshold in UVB-irradiated skin was significantly increased in subjects who were administered ibuprofen compared to the placebo group. Variation among all evoked pain tests ranged from 2.2% to 30.6%. CONCLUSIONS Four studies using a similar design showed reproducibility with respect to the included evoked pain models. The relatively high consistency and reproducibility of two analgesics at doses known to be effective in treating clinically relevant pain supports the validity of using this pain test battery to investigate the analgesic activity and determine the active dosage of putative analgesic compounds in early clinical development. SIGNIFICANCE The consistency and reproducibility of measuring the profile of an analgesic at clinically relevant doses illustrates that this pain test battery is a valid tool for demonstrating the analgesic activity of a test compound and for determining the optimal active dose in early clinical drug development.
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Affiliation(s)
| | | | | | - William S. Denney
- Pfizer Inc.CambridgeMassachusetts
- Present address:
Human Predictions LLCCambridgeMassachusetts
| | | | | | | | - Geert J. Groeneveld
- Centre for Human Drug ResearchLeidenThe Netherlands
- Leiden University Medical CenterLeidenThe Netherlands
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A randomised, double-blind, placebo-controlled crossover trial of the influence of the HCN channel blocker ivabradine in a healthy volunteer pain model: an enriched population trial. Pain 2019; 160:2554-2565. [DOI: 10.1097/j.pain.0000000000001638] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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25
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Huang N, Yang C, Hua D, Li S, Zhan G, Yang N, Luo A, Xu H. Alterations in the BDNF–mTOR Signaling Pathway in the Spinal Cord Contribute to Hyperalgesia in a Rodent Model of Chronic Restraint Stress. Neuroscience 2019; 409:142-151. [DOI: 10.1016/j.neuroscience.2019.03.052] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2018] [Revised: 03/23/2019] [Accepted: 03/26/2019] [Indexed: 02/08/2023]
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26
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Quantitative sensory testing response patterns to capsaicin- and ultraviolet-B-induced local skin hypersensitization in healthy subjects: a machine-learned analysis. Pain 2019; 159:11-24. [PMID: 28700537 PMCID: PMC5737455 DOI: 10.1097/j.pain.0000000000001008] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The comprehensive assessment of pain-related human phenotypes requires combinations of nociceptive measures that produce complex high-dimensional data, posing challenges to bioinformatic analysis. In this study, we assessed established experimental models of heat hyperalgesia of the skin, consisting of local ultraviolet-B (UV-B) irradiation or capsaicin application, in 82 healthy subjects using a variety of noxious stimuli. We extended the original heat stimulation by applying cold and mechanical stimuli and assessing the hypersensitization effects with a clinically established quantitative sensory testing (QST) battery (German Research Network on Neuropathic Pain). This study provided a 246 × 10-sized data matrix (82 subjects assessed at baseline, following UV-B application, and following capsaicin application) with respect to 10 QST parameters, which we analyzed using machine-learning techniques. We observed statistically significant effects of the hypersensitization treatments in 9 different QST parameters. Supervised machine-learned analysis implemented as random forests followed by ABC analysis pointed to heat pain thresholds as the most relevantly affected QST parameter. However, decision tree analysis indicated that UV-B additionally modulated sensitivity to cold. Unsupervised machine-learning techniques, implemented as emergent self-organizing maps, hinted at subgroups responding to topical application of capsaicin. The distinction among subgroups was based on sensitivity to pressure pain, which could be attributed to sex differences, with women being more sensitive than men. Thus, while UV-B and capsaicin share a major component of heat pain sensitization, they differ in their effects on QST parameter patterns in healthy subjects, suggesting a lack of redundancy between these models.
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Designing and conducting proof-of-concept chronic pain analgesic clinical trials. Pain Rep 2019; 4:e697. [PMID: 31583338 PMCID: PMC6749910 DOI: 10.1097/pr9.0000000000000697] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 09/24/2018] [Accepted: 09/26/2018] [Indexed: 02/07/2023] Open
Abstract
Introduction: The evolution of pain treatment is dependent on successful development and testing of interventions. Proof-of-concept (POC) studies bridge the gap between identification of a novel target and evaluation of the candidate intervention's efficacy within a pain model or the intended clinical pain population. Methods: This narrative review describes and evaluates clinical trial phases, specific POC pain trials, and approaches to patient profiling. Results: We describe common POC trial designs and their value and challenges, a mechanism-based approach, and statistical issues for consideration. Conclusion: Proof-of-concept trials provide initial evidence for target use in a specific population, the most appropriate dosing strategy, and duration of treatment. A significant goal in designing an informative and efficient POC study is to ensure that the study is safe and sufficiently sensitive to detect a preliminary efficacy signal (ie, a potentially valuable therapy). Proof-of-concept studies help avoid resources wasted on targets/molecules that are not likely to succeed. As such, the design of a successful POC trial requires careful consideration of the research objective, patient population, the particular intervention, and outcome(s) of interest. These trials provide the basis for future, larger-scale studies confirming efficacy, tolerability, side effects, and other associated risks.
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28
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Siebenga PS, van Amerongen G, Klaassen ES, de Kam ML, Rissmann R, Groeneveld GJ. The ultraviolet B inflammation model: Postinflammatory hyperpigmentation and validation of a reduced UVB exposure paradigm for inducing hyperalgesia in healthy subjects. Eur J Pain 2019; 23:874-883. [PMID: 30597682 PMCID: PMC6590423 DOI: 10.1002/ejp.1353] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 12/17/2018] [Accepted: 12/23/2018] [Indexed: 12/18/2022]
Abstract
Background Pain models are commonly used in drug development to demonstrate analgesic activity in healthy subjects and should therefore not cause long‐term adverse effects. The ultraviolet B (UVB) model is a model for inflammatory pain in which three times the minimal erythema dose (3MED) is typically applied to induce sensitization. Based on reports of long‐lasting postinflammatory hyperpigmentation (PIH) associated with 3MED, it was decided to investigate the prevalence of PIH among subjects who were previously exposed to 3MED at our research centre. In addition, re‐evaluation of the UVB inflammation model using a reduced exposure paradigm (2MED) was performed in healthy subjects. Methods In the first study, all 142 subjects previously exposed to 3MED UVB were invited for a clinical evaluation of PIH. In the second study, 18 healthy subjects were exposed to 2MED UVB, and heat pain detection threshold (PDT) and PIH were evaluated. Results In total, 78 of the 142 subjects responded. The prevalence of PIH among responders was 53.8%. In the second study, we found a significant and stable difference in PDT between UVB‐exposed and control skin 3 hr after irradiation; 13 hr post‐irradiation, the least squares mean estimate of the difference in PDT ranged from −2.6°C to −4.5°C (p < 0.0001). Finally, the prevalence of PIH was lower in the 2MED group compared to the 3MED group. Conclusions The 3MED model is associated with a relatively high prevalence of long‐lasting PIH. In contrast, 2MED exposure produces stable hyperalgesia and has a lower risk of PIH and is therefore recommended for modelling inflammatory pain. Significance Postinflammatory hyperpigmentation is an unwanted long‐term side effect associated with the UVB inflammation model using the 3× minimal erythema dose (3MED) paradigm. In contrast, using a 2MED paradigm results in hyperalgesia that is stable for 36 hr and has a lower risk of inducing postinflammatory hyperpigmentation.
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Affiliation(s)
| | | | | | | | - Robert Rissmann
- Centre for Human Drug Research, Leiden, The Netherlands.,Leiden University Medical Centre, Leiden, The Netherlands.,Leiden Academic Centre for Drug Research, Leiden, The Netherlands
| | - Geert Jan Groeneveld
- Centre for Human Drug Research, Leiden, The Netherlands.,Leiden University Medical Centre, Leiden, The Netherlands
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29
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van Amerongen G, Siebenga PS, Gurrell R, Dua P, Whitlock M, Gorman D, Okkerse P, Hay JL, Butt RP, Groeneveld GJ. Analgesic potential of PF-06372865, an α2/α3/α5 subtype-selective GABA A partial agonist, in humans. Br J Anaesth 2019; 123:e194-e203. [PMID: 30915991 DOI: 10.1016/j.bja.2018.12.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Revised: 12/11/2018] [Accepted: 12/11/2018] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND This study investigated the analgesic effects of two doses (15 and 65 mg) of PF-06372865, a novel α2/α3/α5 gamma-aminobutyric acid A (GABAA) subunit selective partial positive allosteric modulator (PAM), compared with placebo and pregabalin (300 mg) as a positive control. METHODS We performed a randomised placebo-controlled crossover study (NCT02238717) in 20 healthy subjects, using a battery of pain tasks (electrical, pressure, heat, cold and inflammatory pain, including a paradigm of conditioned pain modulation). Pharmacodynamic measurements were performed at baseline and up to 10 h after dose. RESULTS A dose of 15 mg PF-06372865 increased pain tolerance thresholds (PTTs) for pressure pain at a ratio of 1.11 (90% confidence interval [CI]: 1.02, 1.22) compared with placebo. A dose of 65 mg PF-06372865 led to an increase in PTT for the cold pressor at a ratio of 1.17 (90% CI: 1.03, 1.32), and pressure pain task: 1.11 (90% CI: 1.01, 1.21). Pregabalin showed an increase in PTT for pressure pain at a ratio of 1.15 (95% CI: 1.06, 1.26) and cold pressor task: 1.31 (90% CI: 1.16, 1.48). CONCLUSION We conclude that PF-06372865 has analgesic potential at doses that do not induce significant sedation or other intolerable adverse events limiting its clinical use. In addition, the present study established the potential role for this battery of pain tasks as a tool in the development of analgesics with a novel mechanism of action, for the treatment of various pain states including neuropathic pain and to establish proof-of-concept. CLINICAL TRIALS REGISTRATION NCT0223871.
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Affiliation(s)
| | | | | | - Pinky Dua
- Early Clinical Development, Pfizer WRD, Cambridge, UK
| | - Mark Whitlock
- Early Clinical Development, Pfizer WRD, Cambridge, UK
| | - Donal Gorman
- Early Clinical Development, Pfizer WRD, Cambridge, UK
| | - Pieter Okkerse
- Centre for Human Drug Research (CHDR), Leiden, the Netherlands
| | - Justin L Hay
- Centre for Human Drug Research (CHDR), Leiden, the Netherlands
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30
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Li S, Zeng J, Wan X, Yao Y, Zhao N, Yu Y, Yu C, Xia Z. Enhancement of spinal dorsal horn neuron NMDA receptor phosphorylation as the mechanism of remifentanil induced hyperalgesia: Roles of PKC and CaMKII. Mol Pain 2018; 13:1744806917723789. [PMID: 28714352 PMCID: PMC5549877 DOI: 10.1177/1744806917723789] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Background Modulation of N-methyl-D-aspartate receptor subunits NR1 and NR2 through phosphorylation mediates opioid-induced hyperalgesia, and activations of protein kinase C and extracellular signal-regulated kinase 1/2 potentiate while activation of calcium/calmodulin-dependent protein kinase II inhibits opioid-induced hyperalgesia. However, the mechanism of opioid-induced hyperalgesia development and in particular the potential interplay between N-methyl-D-aspartate receptors and protein kinase C or calcium/calmodulin-dependent protein kinase II or extracellular signal-regulated kinase 1/2 in the development of remifentanil-induced hyperalgesia is unclear. Methods Remifentanil (1 µg ċ kg−1 ċ min−1) was given intravenously over 60 min in rats, followed by the infusion of either vehicle solution or the respective inhibitors of protein kinase C (chelerythrine), extracellular signal-regulated kinase II (KN93), or extracellular signal-regulated kinase 1/2 (PD98059). Thereafter, the pain behaviors were evaluated by the paw withdrawal mechanical threshold and paw withdrawal thermal latency. In in vitro studies, fetal spinal cord dorsal horn neurons were primary cultured in the presence of 4 nM remifentanil for 60 min, and then the remifentanil was washed out and replaced immediately by culturing in the absence or presence of chelerythrine, KN93 or PD98059, respectively for up to 8 h. The expressions of N-methyl-D-aspartate receptors subunits and their phosphorylation (NR1, NR2B, p-NR1, p-NR2B) were analyzed by Western blotting after the completion of treatments. Functional changes of N-methyl-D-aspartate receptors were evaluated by electrophysiologic recordings of N-methyl-D-aspartate currents. Results Remifentanil induced significant thermal and mechanical hyperalgesia, which were significantly attenuated by Chelerythrine or KN93 but not PD98059. The expressions of NR1, NR2B, p-NR1, and p-NR2B were increased significantly and progressively over time after remifentanil administration, and these increases were all significantly attenuated by either chelerythrine or KN93 but not PD98059. Intriguingly, N-methyl-D-aspartate receptor functional enhancement induced by remifentanil was attenuated by Chelerythrine, KN93, and PD98059. Conclusions It is concluded that the enhancements in function and quantity of N-methyl-D-aspartate receptor via phosphorylation of its subunits through protein kinase C and calcium/calmodulin-dependent protein kinase II activation may represent the major mechanism whereby remifentanil induced hyperalgesia.
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Affiliation(s)
- Sisi Li
- Department of Anesthesiology, The Affiliated Hospital of Stomatology, Chongqing Medical University, Chongqing, China
| | - Jie Zeng
- Department of Anesthesiology, The Affiliated Hospital of Stomatology, Chongqing Medical University, Chongqing, China
| | - Xiaoxiao Wan
- Department of Anesthesiology, The Affiliated Hospital of Stomatology, Chongqing Medical University, Chongqing, China
| | - Ying Yao
- Department of Anesthesiology, The Affiliated Hospital of Stomatology, Chongqing Medical University, Chongqing, China
| | - Nan Zhao
- Department of Anesthesiology, The Affiliated Hospital of Stomatology, Chongqing Medical University, Chongqing, China
| | - Yujia Yu
- Department of Anesthesiology, The Affiliated Hospital of Stomatology, Chongqing Medical University, Chongqing, China
| | - Cong Yu
- Department of Anesthesiology, The Affiliated Hospital of Stomatology, Chongqing Medical University, Chongqing, China
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van Amerongen G, Siebenga P, de Kam ML, Hay JL, Groeneveld GJ. Effect profile of paracetamol, Δ9-THC and promethazine using an evoked pain test battery in healthy subjects. Eur J Pain 2018; 22:1331-1342. [PMID: 29635857 DOI: 10.1002/ejp.1222] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/21/2018] [Indexed: 12/12/2022]
Abstract
BACKGROUND A battery of evoked pain tasks (PainCart) was developed to investigate the pharmacodynamic properties of novel analgesics in early-phase clinical research. As part of its clinical validation, compounds with different pharmacological mechanisms of actions are investigated. The aim was to investigate the analgesic effects of classic and nonclassic analgesics compared to a sedating negative control in a randomized placebo-controlled crossover study in 24 healthy volunteers using the PainCart. METHODS The PainCart consisted of pain tasks eliciting electrical, pressure, heat, cold and inflammatory pain. Subjective scales for cognitive functioning and psychotomimetic effects were included. Subjects were administered each of the following oral treatments: paracetamol (1000 mg), Δ9-THC (10 mg), promethazine (50 mg) or matching placebo. Pharmacodynamic measurements were performed at baseline and repeated up to 10 h postdose. RESULTS Paracetamol did not show a significant reduction in pain sensation or subjective cognitive functioning compared to placebo. Promethazine induced a statistically significant reduction in PTT for cold pressor and pressure stimulation. Furthermore, reduced subjective alertness was observed. Δ9-THC showed a statistically significant decrease in PTT for electrical and pressure stimulation. Δ9-THC also demonstrated subjective effects, including changes in alertness and calmness, as well as feeling high and psychotomimetic effects. CONCLUSIONS This study found a decreased pain tolerance due to Δ9-THC and promethazine, or lack thereof, using an evoked pain task battery. Pain thresholds following paracetamol administration remained unchanged, which may be due to insufficient statistical power. We showed that pain thresholds determined using this pain test battery are not driven by sedation. SIGNIFICANCE The multimodal battery of evoked pain tasks utilized in this study may play an important role in early-phase clinical drug development. This battery of pain tasks is not sensitive to the effects of sedation alone, and thus suitable to investigate the analgesic potential of novel analgesic compounds.
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Affiliation(s)
- G van Amerongen
- Centre for Human Drug Research (CHDR), Leiden, The Netherlands
| | - P Siebenga
- Centre for Human Drug Research (CHDR), Leiden, The Netherlands
| | - M L de Kam
- Centre for Human Drug Research (CHDR), Leiden, The Netherlands
| | - J L Hay
- Centre for Human Drug Research (CHDR), Leiden, The Netherlands
| | - G J Groeneveld
- Centre for Human Drug Research (CHDR), Leiden, The Netherlands
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Knezevic NN, Yekkirala A, Yaksh TL. Basic/Translational Development of Forthcoming Opioid- and Nonopioid-Targeted Pain Therapeutics. Anesth Analg 2017; 125:1714-1732. [PMID: 29049116 PMCID: PMC5679134 DOI: 10.1213/ane.0000000000002442] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Opioids represent an efficacious therapeutic modality for some, but not all pain states. Singular reliance on opioid therapy for pain management has limitations, and abuse potential has deleterious consequences for patient and society. Our understanding of pain biology has yielded insights and opportunities for alternatives to conventional opioid agonists. The aim is to have efficacious therapies, with acceptable side effect profiles and minimal abuse potential, which is to say an absence of reinforcing activity in the absence of a pain state. The present work provides a nonexclusive overview of current drug targets and potential future directions of research and development. We discuss channel activators and blockers, including sodium channel blockers, potassium channel activators, and calcium channel blockers; glutamate receptor-targeted agents, including N-methyl-D-aspartate, α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid, and metabotropic receptors. Furthermore, we discuss therapeutics targeted at γ-aminobutyric acid, α2-adrenergic, and opioid receptors. We also considered antagonists of angiotensin 2 and Toll receptors and agonists/antagonists of adenosine, purine receptors, and cannabinoids. Novel targets considered are those focusing on lipid mediators and anti-inflammatory cytokines. Of interest is development of novel targeting strategies, which produce long-term alterations in pain signaling, including viral transfection and toxins. We consider issues in the development of druggable molecules, including preclinical screening. While there are examples of successful translation, mechanistically promising preclinical candidates may unexpectedly fail during clinical trials because the preclinical models may not recapitulate the particular human pain condition being addressed. Molecular target characterization can diminish the disconnect between preclinical and humans' targets, which should assist in developing nonaddictive analgesics.
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Affiliation(s)
- Nebojsa Nick Knezevic
- From the *Department of Anesthesiology, Advocate Illinois Masonic Medical Center Chicago, Illinois; Departments of †Anesthesiology and ‡Surgery, University of Illinois, Chicago, Illinois; §Department of Neurobiology, Harvard Medical School, and Boston Children's Hospital, Boston, Massachusetts; ‖Blue Therapeutics, Harvard Innovation Launch Lab, Allston, Massachusetts; and Departments of ¶Anesthesiology and #Pharmacology, University of California, San Diego, La Jolla, California
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Taneja A, Della Pasqua O, Danhof M. Challenges in translational drug research in neuropathic and inflammatory pain: the prerequisites for a new paradigm. Eur J Clin Pharmacol 2017; 73:1219-1236. [PMID: 28894907 PMCID: PMC5599481 DOI: 10.1007/s00228-017-2301-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 07/03/2017] [Indexed: 12/21/2022]
Abstract
AIM Despite an improved understanding of the molecular mechanisms of nociception, existing analgesic drugs remain limited in terms of efficacy in chronic conditions, such as neuropathic pain. Here, we explore the underlying pathophysiological mechanisms of neuropathic and inflammatory pain and discuss the prerequisites and opportunities to reduce attrition and high-failure rate in the development of analgesic drugs. METHODS A literature search was performed on preclinical and clinical publications aimed at the evaluation of analgesic compounds using MESH terms in PubMed. Publications were selected, which focused on (1) disease mechanisms leading to chronic/neuropathic pain and (2) druggable targets which are currently under evaluation in drug development. Attention was also given to the role of biomarkers and pharmacokinetic-pharmacodynamic modelling. RESULTS Multiple mechanisms act concurrently to produce pain, which is a non-specific manifestation of underlying nociceptive pathways. Whereas these manifestations can be divided into neuropathic and inflammatory pain, it is now clear that inflammatory mechanisms are a common trigger for both types of pain. This has implications for drug development, as the assessment of drug effects in experimental models of neuropathic and chronic pain is driven by overt behavioural measures. By contrast, the use of mechanistic biomarkers in inflammatory pain has provided the pharmacological basis for dose selection and evaluation of non-steroidal anti-inflammatory drugs (NSAIDs). CONCLUSION A different paradigm is required for the identification of relevant targets and candidate molecules whereby pain is coupled to the cause of sensorial signal processing dysfunction rather than clinical symptoms. Biomarkers which enable the characterisation of drug binding and target activity are needed for a more robust dose rationale in early clinical development. Such an approach may be facilitated by quantitative clinical pharmacology and evolving technologies in brain imaging, allowing accurate assessment of target engagement, and prediction of treatment effects before embarking on large clinical trials.
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Affiliation(s)
- A Taneja
- Division of Pharmacology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - O Della Pasqua
- Division of Pharmacology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands.,Clinical Pharmacology Modelling & Simulation, GlaxoSmithKline, Uxbridge, UK.,Clinical Pharmacology & Therapeutics Group, University College London, London, UK
| | - M Danhof
- Division of Pharmacology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands.
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Midazolam as an active placebo in 3 fentanyl-validated nociceptive pain models. Pain 2017; 158:1264-1271. [PMID: 28338566 DOI: 10.1097/j.pain.0000000000000910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The use of inactive placebos in early translational trials of potentially analgesic compounds is discouraged because of the side-effect profiles of centrally acting analgesics. Therefore, benzodiazepines are used, although their use has not been validated in this context. Whether benzodiazepines confound the results of acute pain tests is unknown. Midazolam (0.06 mg/kg) as an active placebo was investigated in 3 nociceptive models that included contact heat, electrical pain, and pressure pain thresholds in 24 healthy volunteers. Fentanyl (1 μg/kg) served as an internal validator in this randomized, placebo (saline) controlled, 3-way cross-over trial. The primary outcome parameter (contact heat pain) was analyzed using a one-way, repeated measures analysis of variance and Tukey's post test. Midazolam did not reduce pain ([numeric rating scale], 0-100) in a statistically significant manner compared with placebo for the contact heat (mean difference -1.7, 95% confidence interval -10.6 to 7.3; P = 0.89) or electrical pain (4.3, -5.1 to 13.7; P = 0.51) test, nor did it raise the pressure pain thresholds (-28 kPa, -122; 64 kPa, P = 0.73). The width of the confidence intervals suggested that there were no clinically meaningful analgesic effects compared with the placebo. In contrast, the analgesic efficacy of fentanyl was effectively demonstrated in all 3 models (P < 0.01 vs midazolam and placebo). The findings of this study show that midazolam can be used as an active placebo in analgesic drug trials. Furthermore, the proposed models were simple to implement and very effective in detecting analgesia. The test battery can be used in translational trials for new compounds and comes with an active placebo and an optional active comparator.
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van Amerongen G, de Boer MW, Groeneveld GJ, Hay JL. A literature review on the pharmacological sensitivity of human evoked hyperalgesia pain models. Br J Clin Pharmacol 2016; 82:903-22. [PMID: 27203797 DOI: 10.1111/bcp.13018] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 05/13/2016] [Accepted: 05/18/2016] [Indexed: 02/06/2023] Open
Abstract
AIMS Human evoked pain models can be used to determine the efficacy of new and existing analgesics and to aid in the identification of new targets. Aspects of neuropathic pain can be simulated by inducing hyperalgesia resulting from provoked sensitization. The present literature review aimed to provide insight into the sensitivity of different hyperalgesia and allodynia models of pharmacological treatment. METHODS A literature search was performed to identify randomized, double-blind, placebo-controlled studies that included human hyperalgesia pain models and investigated the pharmacodynamic effects of different classes of drugs. RESULTS Three hyperalgesia models [ultraviolet B (UVB) irradiation, capsaicin and thermode burn] have been used extensively. Assessment of hyperalgesia/allodynia and pharmacological effect are measured using challenge tests, which generally comprise thermal (heat/cold) or mechanical stimulation (pin-prick, stroking or impact). The UVB model was sensitive to the antihyperalgesic effects of nonsteroidal anti-inflammatory drugs (NSAIDs) and opioids. The capsaicin model was partially sensitive to opioids. The burn model did not detect any antihyperalgesic effects when NSAIDs or local anaesthetics were administered but responded to the effects of N-methyl D-aspartate (NMDA) receptor antagonists by moderately reducing mechanical hyperalgesia. CONCLUSIONS Based on pharmacological sensitivity, the UVB model adequately reflects inflammatory pain and was sensitive to NSAIDs and opioids. Findings from the capsaicin and burn models raised questions about the translatability of these models to the treatment of neuropathic pain. There is a need for a reproducible and predictive model of neuropathic pain, either in healthy subjects or in patients.
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Affiliation(s)
| | | | | | - Justin L Hay
- Centre for Human Drug Research (CHDR), Leiden, The Netherlands
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