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Guekos A, Saxer J, Salinas Gallegos D, Schweinhardt P. Healthy women show more experimentally induced central sensitization compared with men. Pain 2024; 165:1413-1424. [PMID: 38231588 PMCID: PMC11090033 DOI: 10.1097/j.pain.0000000000003144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 09/14/2023] [Accepted: 10/13/2023] [Indexed: 01/18/2024]
Abstract
ABSTRACT Women more often experience chronic pain conditions than men. Central sensitization (CS) is one key mechanism in chronic pain that can differ between the sexes. It is unknown whether CS processes are already more pronounced in healthy women than in men. In 66 subjects (33 women), a thermal CS induction protocol was applied to the dorsum of one foot and a sham protocol to the other. Spatial extent [cm 2 ] of secondary mechanical hyperalgesia (SMH) and dynamic mechanical allodynia were assessed as subjective CS proxy measures, relying on verbal feedback. Changes in nociceptive withdrawal reflex magnitude (NWR-M) and response rate (NWR-RR) recorded through surface electromyography at the biceps and rectus femoris muscles were used as objective CS proxies. The effect of the CS induction protocol on SMH was higher in women than in men (effect size 2.11 vs 1.68). Nociceptive withdrawal reflex magnitude results were statistically meaningful for women (effect size 0.31-0.36) but not for men (effect size 0.12-0.29). Differences between men and women were not meaningful. Nociceptive withdrawal reflex response rate at the rectus femoris increased in women after CS induction and was statistically different from NWR-RR in men (median differences of 13.7 and 8.4% for 120 and 140% reflex threshold current). The objective CS proxy differences indicate that dorsal horn CS processes are more pronounced in healthy women. The even larger sex differences in subjective CS proxies potentially reflect greater supraspinal influence in women. This study shows that sex differences are present in experimentally induced CS in healthy subjects, which might contribute to women's vulnerability for chronic pain.
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Affiliation(s)
- Alexandros Guekos
- Integrative Spinal Research, Department of Chiropractic Medicine, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
- Decision Neuroscience Lab, Department of Health Sciences and Technology, Institute of Human Movement Sciences and Sport, ETH Zurich, Zurich, Switzerland
| | - Janis Saxer
- Integrative Spinal Research, Department of Chiropractic Medicine, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
- Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Diego Salinas Gallegos
- Integrative Spinal Research, Department of Chiropractic Medicine, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
- Department of Health Sciences and Technology, ETH Zurich, Zurich, Switzerland
- IQVIA AG, Rotkreuz, Switzerland
| | - Petra Schweinhardt
- Integrative Spinal Research, Department of Chiropractic Medicine, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
- Faculty of Medicine, University of Zurich, Zurich, Switzerland
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Scheuren PS, Bösch S, Rosner J, Allmendinger F, Kramer JLK, Curt A, Hubli M. Priming of the autonomic nervous system after an experimental human pain model. J Neurophysiol 2023; 130:436-446. [PMID: 37405990 PMCID: PMC10625835 DOI: 10.1152/jn.00064.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 07/02/2023] [Accepted: 07/03/2023] [Indexed: 07/07/2023] Open
Abstract
Modulated autonomic responses to noxious stimulation have been reported in experimental and clinical pain. These effects are likely mediated by nociceptive sensitization, but may also, more simply reflect increased stimulus-associated arousal. To disentangle between sensitization- and arousal-mediated effects on autonomic responses to noxious input, we recorded sympathetic skin responses (SSRs) in response to 10 pinprick and heat stimuli before (PRE) and after (POST) an experimental heat pain model to induce secondary hyperalgesia (EXP) and a control model (CTRL) in 20 healthy females. Pinprick and heat stimuli were individually adapted for pain perception (4/10) across all assessments. Heart rate, heart rate variability, and skin conductance level (SCL) were assessed before, during, and after the experimental heat pain model. Both pinprick- and heat-induced SSRs habituated from PRE to POST in CTRL, but not EXP (P = 0.033). Background SCL (during stimuli application) was heightened in EXP compared with CTRL condition during pinprick and heat stimuli (P = 0.009). Our findings indicate that enhanced SSRs after an experimental pain model are neither fully related to subjective pain, as SSRs dissociated from perceptual responses, nor to nociceptive sensitization, as SSRs were enhanced for both modalities. Our findings can, however, be explained by priming of the autonomic nervous system during the experimental pain model, which makes the autonomic nervous system more susceptible to noxious input. Taken together, autonomic readouts have the potential to objectively assess not only nociceptive sensitization but also priming of the autonomic nervous system, which may be involved in the generation of distinct clinical pain phenotypes.NEW & NOTEWORTHY The facilitation of pain-induced sympathetic skin responses observed after experimentally induced central sensitization is unspecific to the stimulation modality and thereby unlikely solely driven by nociceptive sensitization. In addition, these enhanced pain-induced autonomic responses are also not related to higher stimulus-associated arousal, but rather a general priming of the autonomic nervous system. Hence, autonomic readouts may be able to detect generalized hyperexcitability in chronic pain, beyond the nociceptive system, which may contribute to clinical pain phenotypes.
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Affiliation(s)
- 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
| | - Sofia Bösch
- Spinal Cord Injury Center, 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 Centre, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Florin Allmendinger
- Spinal Cord Injury Center, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
| | - John Lawrence Kipling Kramer
- International Collaboration on Repair Discoveries (ICORD), University of British Columbia, Vancouver, British Columbia, Canada
- Department of Anesthesiology, Pharmacology & Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - 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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Mehesz E, Karoui H, Strutton PH, Hughes SW. Exposure to an Immersive Virtual Reality Environment can Modulate Perceptual Correlates of Endogenous Analgesia and Central Sensitization in Healthy Volunteers. J Pain 2021; 22:707-714. [PMID: 33465506 DOI: 10.1016/j.jpain.2020.12.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 12/14/2020] [Accepted: 12/29/2020] [Indexed: 11/26/2022]
Abstract
Virtual reality (VR) has been shown to produce analgesic effects during different experimental and clinical pain states. Despite this, the top-down mechanisms are still poorly understood. In this study, we examined the influence of both a real and sham (ie, the same images in 2D) immersive arctic VR environment on conditioned pain modulation (CPM) and in a human surrogate model of central sensitization in 38 healthy volunteers. CPM and acute heat pain thresholds were assessed before and during VR/sham exposure in the absence of any sensitization. In a follow-on study, we used the cutaneous high frequency stimulation model of central sensitization and measured changes in mechanical pain sensitivity in an area of heterotopic sensitization before and during VR/sham exposure. There was an increase in CPM efficiency during the VR condition compared to baseline (P < .01). In the sham condition, there was a decrease in CPM efficiency compared to baseline (P < .01) and the real VR condition (P < .001). Neither real nor sham VR had any effect on pain ratings reported during the conditioning period or on heat pain threshold. There was also an attenuation of mechanical pain sensitivity during the VR condition indicating a lower sensitivity compared to sham (P < .05). We conclude that exposure to an immersive VR environment has no effect over acute pain thresholds but can modulate dynamic CPM responses and mechanical hypersensitivity in healthy volunteers. PERSPECTIVE: This study has demonstrated that exposure to an immersive virtual reality environment can modulate perceptual correlates of endogenous pain modulation and secondary hyperalgesia in a human surrogate pain model. These results suggest that virtual reality could provide a novel mechanism-driven analgesic strategy in patients with altered central pain processing.
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Affiliation(s)
- Erzsebet Mehesz
- The Nick Davey Laboratory, Department of Surgery and Cancer, Imperial College London, London, UK
| | - Hajer Karoui
- The Nick Davey Laboratory, Department of Surgery and Cancer, Imperial College London, London, UK
| | - Paul H Strutton
- The Nick Davey Laboratory, Department of Surgery and Cancer, Imperial College London, London, UK
| | - Sam W Hughes
- The Pain Neuroplasticity and Modulation Laboratory, Brain Research and Imaging Centre (BRIC), School of Psychology, Faculty of Health, University of Plymouth, Plymouth, UK.
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Sooratgar A, Ahmadi Z, Asadi Y, Dibaji F, Shamshiri AR, Afkhami F. Evaluation of Secondary Thermal Hyperalgesia Resulting from Pulpal Inflammation in Patients with Symptomatic Irreversible Pulpitis. J Endod 2021; 47:902-905. [PMID: 33647371 DOI: 10.1016/j.joen.2021.02.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2020] [Revised: 02/11/2021] [Accepted: 02/18/2021] [Indexed: 02/05/2023]
Abstract
INTRODUCTION Inflammation can lead to hyperalgesia and allodynia by activation or sensitization of peripheral and central nervous system neurons. This study aimed to assess the occurrence of secondary thermal hyperalgesia in patients with symptomatic irreversible pulpitis (SIP). METHODS The cold sensitivity test (visual analog scale) was performed for the tooth with SIP, its adjacent sound tooth, the same sound tooth in the opposite jaw, and the contralateral sound tooth in the opposite quadrant of the same jaw. Next, the tooth with SIP underwent root canal treatment, and 3 weeks later, after complete elimination of pain, the teeth underwent cold sensitivity testing again. RESULTS A total of 64 patients, including 41 women and 23 men 18-65 years old, were evaluated in this study. The response to the cold sensitivity test significantly decreased in the tooth with SIP (P < .001), its adjacent sound tooth (P < .001), and the same sound tooth in the opposite jaw (P = .004) but not in the contralateral sound tooth in the opposite quadrant of the same jaw (P = .45) after endodontic treatment. No significant difference was noted between men and women in the groups (P > .05). CONCLUSIONS Hypersensitivity to cold test due to pulpal inflammation can also result in exaggerated response of the adjacent sound tooth and the same tooth in the opposite jaw to cold sensitivity test; these observations can be explained by the central and peripheral sensitization mechanisms.
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Affiliation(s)
- Aidin Sooratgar
- Department of Endodontics, School of Dentistry, Tehran University of Medical Sciences, International Campus, Tehran, Iran
| | | | - Yasin Asadi
- Department of Periodontics, School of Dentistry, AJA University of Medical Sciences, Tehran, Iran
| | - Fatemeh Dibaji
- Department of Endodontics, School of Dentistry, Tehran University of Medical Sciences, International Campus, Tehran, Iran
| | - Ahmad Reza Shamshiri
- Dental Research Center, Dentistry Research Institute, Department of Community Oral Health, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran
| | - Farzaneh Afkhami
- Department of Endodontics, School of Dentistry, Tehran University of Medical Sciences, International Campus, Tehran, Iran.
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van den Broeke EN, Gousset S, Bouvy J, Stouffs A, Lebrun L, van Neerven SGA, Mouraux A. Heterosynaptic facilitation of mechanical nociceptive input is dependent on the frequency of conditioning stimulation. J Neurophysiol 2019; 122:994-1001. [PMID: 31291140 PMCID: PMC6766737 DOI: 10.1152/jn.00274.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 06/10/2019] [Accepted: 07/09/2019] [Indexed: 11/22/2022] Open
Abstract
High-frequency burstlike electrical conditioning stimulation (HFS) applied to human skin induces an increase in mechanical pinprick sensitivity of the surrounding unconditioned skin (a phenomenon known as secondary hyperalgesia). The present study assessed the effect of frequency of conditioning stimulation on the development of this increased pinprick sensitivity in humans. In a first experiment, we compared the increase in pinprick sensitivity induced by HFS, using monophasic non-charge-compensated pulses and biphasic charge-compensated pulses. High-frequency stimulation, traditionally delivered with non-charge-compensated square-wave pulses, may induce a cumulative depolarization of primary afferents and/or changes in pH at the electrode-tissue interface due to the accumulation of a net residue charge after each pulse. Both could contribute to the development of the increased pinprick sensitivity in a frequency-dependent fashion. We found no significant difference in the increase in pinprick sensitivity between HFS delivered with charge-compensated and non-charge-compensated pulses, indicating that the possible contribution of charge accumulation when non-charge-compensated pulses are used is negligible. In a second experiment, we assessed the effect of different frequencies of conditioning stimulation (5, 20, 42, and 100 Hz) using charge-compensated pulses on the development of increased pinprick sensitivity. The maximal increase in pinprick sensitivity was observed at intermediate frequencies of stimulation (20 and 42 Hz). It is hypothesized that the stronger increase in pinprick sensitivity at intermediate frequencies may be related to the stronger release of substance P and/or neurokinin-1 receptor activation expressed at lamina I neurons after C-fiber stimulation.NEW & NOTEWORTHY Burstlike electrical conditioning stimulation applied to human skin induces an increase in pinprick sensitivity in the surrounding unconditioned skin (a phenomenon referred to as secondary hyperalgesia). Here we show that the development of the increase in pinprick sensitivity is dependent on the frequency of the burstlike electrical conditioning stimulation.
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Affiliation(s)
- E N van den Broeke
- Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
| | - S Gousset
- Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
| | - J Bouvy
- Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
| | - A Stouffs
- Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
| | - L Lebrun
- Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
| | - S G A van Neerven
- Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
| | - A Mouraux
- Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
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Wahl AM, Bidstrup D, Smidt-Nielsen IG, Werner MU, Hyldegaard O, Rotbøll-Nielsen P. A single session of hyperbaric oxygen therapy demonstrates acute and long-lasting neuroplasticity effects in humans: a replicated, randomized controlled clinical trial. J Pain Res 2019; 12:2337-2348. [PMID: 31534358 PMCID: PMC6682324 DOI: 10.2147/jpr.s198359] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Accepted: 04/24/2019] [Indexed: 12/15/2022] Open
Abstract
Purpose Animal studies have demonstrated anti-inflammatory, and anti-nociceptive properties of hyperbaric oxygen therapy (HBOT). However, physiological data are scarce in humans. In a recent experimental study, the authors used the burn injury (BI) model observing a decrease in secondary hyperalgesia areas (SHA) in the HBOT-group compared to a control-group. Surprisingly, a long-lasting neuroplasticity effect mitigating the BI-induced SHA-response was seen in the HBOT-preconditioned group. The objective of the present study, therefore, was to confirm our previous findings using an examiner-blinded, block-randomized, controlled, crossover study design. Patients and methods Nineteen healthy subjects attended two BI-sessions with an inter-session interval of ≥28 days. The BIs were induced on the lower legs by a contact thermode (12.5 cm2, 47C°, 420 s). The subjects were block-randomized to receive HBOT (2.4 ATA, 100% O2, 90 min) or ambient conditions ([AC]; 1 ATA, 21% O2), dividing cohorts equally into two sequence allocations: HBOT-AC or AC-HBOT. All sensory assessments performed during baseline, BI, and post-intervention phases were at homologous time points irrespective of sequence allocation. The primary outcome was SHA, comparing interventions and sequence allocations. Results Data are mean (95% CI). During HBOT-sessions a mitigating effect on SHA was demonstrated compared to AC-sessions, ie, 18.8 (10.5–27.0) cm2 vs 32.0 (20.1–43.9) cm2 (P=0.021), respectively. In subjects allocated to the sequence AC-HBOT a significantly larger mean difference in SHA in the AC-session vs the HBOT-session was seen 25.0 (5.4–44.7) cm2 (P=0.019). In subjects allocated to the reverse sequence, HBOT-AC, no difference in SHA between sessions was observed (P=0.55), confirming a preconditioning, long-lasting (≥28 days) effect of HBOT. Conclusion Our data demonstrate that a single HBOT-session compared to control is associated with both acute and long-lasting mitigating effects on BI-induced SHA, confirming central anti-inflammatory, neuroplasticity effects of hyperbaric oxygen therapy.
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Affiliation(s)
- Anna M Wahl
- Hyperbaric Unit, Department of Anesthesia, Head and Orthopedic Center, Rigshospitalet, Copenhagen University Hospitals, Copenhagen, Denmark
| | - Daniel Bidstrup
- Hyperbaric Unit, Department of Anesthesia, Head and Orthopedic Center, Rigshospitalet, Copenhagen University Hospitals, Copenhagen, Denmark
| | - Isabel G Smidt-Nielsen
- Hyperbaric Unit, Department of Anesthesia, Head and Orthopedic Center, Rigshospitalet, Copenhagen University Hospitals, Copenhagen, Denmark
| | - Mads U Werner
- Multidisciplinary Pain Center, Neuroscience Center, Rigshospitalet, Copenhagen University Hospitals, Copenhagen, Denmark
| | - Ole Hyldegaard
- Hyperbaric Unit, Department of Anesthesia, Head and Orthopedic Center, Rigshospitalet, Copenhagen University Hospitals, Copenhagen, Denmark.,Institute of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Per Rotbøll-Nielsen
- Multidisciplinary Pain Center, Neuroscience Center, Rigshospitalet, Copenhagen University Hospitals, Copenhagen, Denmark
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Meeker TJ, Keaser ML, Khan SA, Gullapalli RP, Seminowicz DA, Greenspan JD. Non-invasive Motor Cortex Neuromodulation Reduces Secondary Hyperalgesia and Enhances Activation of the Descending Pain Modulatory Network. Front Neurosci 2019; 13:467. [PMID: 31139047 PMCID: PMC6519323 DOI: 10.3389/fnins.2019.00467] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 04/24/2019] [Indexed: 11/29/2022] Open
Abstract
Central sensitization is a driving mechanism in many chronic pain patients, and manifests as hyperalgesia and allodynia beyond any apparent injury. Recent studies have demonstrated analgesic effects of motor cortex (M1) stimulation in several chronic pain disorders, yet its neural mechanisms remain uncertain. We evaluated whether anodal M1 transcranial direct current stimulation (tDCS) would mitigate central sensitization as measured by indices of secondary hyperalgesia. We used a capsaicin-heat pain model to elicit secondary mechanical hyperalgesia in 27 healthy subjects. In an assessor and subject-blind randomized, sham-controlled, crossover trial, anodal M1 tDCS decreased the intensity of pinprick hyperalgesia more than cathodal or sham tDCS. To elucidate the mechanism driving analgesia, subjects underwent fMRI of painful mechanical stimuli prior to and following induction of the pain model, after receiving M1 tDCS. We hypothesized that anodal M1 tDCS would enhance engagement of a descending pain modulatory (DPM) network in response to mechanical stimuli. Anodal tDCS normalized the effects of central sensitization on neurophysiological responses to mechanical pain in the medial prefrontal cortex, pregenual anterior cingulate cortex, and periaqueductal gray, important regions in the DPM network. Taken together, these results provide support for the hypothesis that anodal M1-tDCS reduces central sensitization-induced hyperalgesia through the DPM network in humans.
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Affiliation(s)
- Timothy J. Meeker
- Department of Neurosurgery, Johns Hopkins Medicine, Baltimore, MD, United States
- Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, Baltimore, MD, United States
- Program in Neuroscience, University of Maryland, Baltimore, Baltimore, MD, United States
- Center to Advance Chronic Pain Research, University of Maryland, Baltimore, Baltimore, MD, United States
| | - Michael L. Keaser
- Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, Baltimore, MD, United States
| | - Shariq A. Khan
- Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, Baltimore, MD, United States
| | - Rao P. Gullapalli
- Program in Neuroscience, University of Maryland, Baltimore, Baltimore, MD, United States
- Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland, Baltimore, Baltimore, MD, United States
| | - David A. Seminowicz
- Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, Baltimore, MD, United States
- Program in Neuroscience, University of Maryland, Baltimore, Baltimore, MD, United States
- Center to Advance Chronic Pain Research, University of Maryland, Baltimore, Baltimore, MD, United States
| | - Joel D. Greenspan
- Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, Baltimore, MD, United States
- Program in Neuroscience, University of Maryland, Baltimore, Baltimore, MD, United States
- Center to Advance Chronic Pain Research, University of Maryland, Baltimore, Baltimore, MD, United States
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van den Broeke EN, Hartgerink DM, Butler J, Lambert J, Mouraux A. Central sensitization increases the pupil dilation elicited by mechanical pinprick stimulation. J Neurophysiol 2019; 121:1621-1632. [PMID: 30785805 DOI: 10.1152/jn.00816.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
High-frequency electrical stimulation (HFS) of skin nociceptors triggers central sensitization (CS), manifested as increased pinprick sensitivity of the skin surrounding the site of HFS. Our aim was to assess the effect of CS on pinprick-evoked pupil dilation responses (PDRs) and pinprick-evoked brain potentials (PEPs). We hypothesized that the increase in the positive wave of PEPs following HFS would result from an enhanced pinprick-evoked phasic response of the locus coeruleus-noradrenergic system (LC-NS), indicated by enhanced PDRs. In 14 healthy volunteers, 64- and 96-mN pinprick stimuli were delivered to the left and right forearms, before and 20 minutes after HFS was applied to one of the two forearms. Both PEPs and pinprick-evoked PDRs were recorded. After HFS, pinprick stimuli were perceived as more intense at the HFS-treated arm compared with baseline and control site, and this increase was similar for both stimulation intensities. Importantly, the pinprick-evoked PDR was also increased, and the increase was stronger for 64- compared with 96-mN stimulation. This is in line with our previous results showing a stronger increase of the PEP positivity at 64 vs. 96-mN stimulation and suggests that the increase in PEP positivity observed in previous studies could relate, at least in part, to enhanced LC-NS activity. However, there was no increase of the PEP positivity in the present study, indicating that enhanced LC-NS activity is not the only determinant of the HFS-induced enhancement of PEPs. Altogether, our results indicate that PDRs are more sensitive for detecting CS than PEPs. NEW & NOTEWORTHY We provide the first demonstration in humans that activity-dependent central sensitization increases pinprick-evoked autonomic arousal measured by enhanced pupil dilation response.
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Affiliation(s)
- E N van den Broeke
- Institute of Neuroscience, Division Cognition and Systems, Université catholique de Louvain , Brussels , Belgium
| | - D M Hartgerink
- Institute of Neuroscience, Division Cognition and Systems, Université catholique de Louvain , Brussels , Belgium.,Behavioural Science Institute, Radboud University , Nijmegen , The Netherlands
| | - J Butler
- Institute of Neuroscience, Division Cognition and Systems, Université catholique de Louvain , Brussels , Belgium
| | - J Lambert
- Institute of Neuroscience, Division Cognition and Systems, Université catholique de Louvain , Brussels , Belgium
| | - A Mouraux
- Institute of Neuroscience, Division Cognition and Systems, Université catholique de Louvain , Brussels , Belgium
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Hansen MS, Wetterslev J, Pipper CB, Asghar MS, Dahl JB. Heat pain detection threshold is associated with the area of secondary hyperalgesia following brief thermal sensitization: a study of healthy male volunteers. J Pain Res 2017; 10:265-274. [PMID: 28184167 PMCID: PMC5291329 DOI: 10.2147/jpr.s121189] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Introduction The area of secondary hyperalgesia following brief thermal sensitization (BTS) of the skin and heat pain detection thresholds (HPDT) may both have predictive abilities in regards to pain sensitivity and clinical pain states. The association between HPDT and secondary hyperalgesia, however, remains unsettled, and the dissimilarities in physiologic properties suggest that they may represent 2 distinctively different pain entities. The aim of this study was to investigate the association between HPDT and BTS-induced secondary hyperalgesia. Methods A sample of 121 healthy male participants was included and tested on 2 separate study days with BTS (45°C, 3 minutes), HPDT, and pain during thermal stimulation (45°C, 1 minute). Areas of secondary hyperalgesia were quantified after monofilament pinprick stimulation. The pain catastrophizing scale (PCS) and hospital anxiety and depression scale (HADS) were also applied. Results A significant association between HPDT and the size of the area of secondary hyperalgesia (p<0.0001) was found. The expected change in area of secondary hyperalgesia due to a 1-degree increase in HPDT was estimated to be −27.38 cm2, 95% confidence interval (CI) of −37.77 to −16.98 cm2, with an R2 of 0.19. Likewise, a significant association between HADS-depression subscore and area of secondary hyperalgesia (p=0.046) was found, with an estimated expected change in secondary hyperalgesia to a 1-point increase in HADS-depression subscore of 11 cm2, 95% CI (0.19–21.82), and with R2 of 0.03. We found no significant associations between secondary hyperalgesia area and PCS score or pain during thermal stimulation. Conclusion HPDT and the area of secondary hyperalgesia after BTS are significantly associated; however, with an R2 of only 19%, HPDT only offers a modest explanation of the inter-participant variation in the size of the secondary hyperalgesia area elicited by BTS.
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Affiliation(s)
- Morten Sejer Hansen
- Department of Anesthesiology, 4231, Centre of Head and Orthopedics, Rigshospitalet
| | - Jørn Wetterslev
- Copenhagen Trial Unit, Centre for Clinical Intervention Research, Department 7812
| | | | | | - Jørgen Berg Dahl
- Department of Anesthesiology, Department Z, Bispebjerg Hospital, Copenhagen, Denmark
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Springborg AD, Jensen EK, Taylor BK, Werner MU. Effects of target-controlled infusion of high-dose naloxone on pain and hyperalgesia in a human thermal injury model: a study protocol: A randomized, double-blind, placebo-controlled, crossover trial with an enriched design. Medicine (Baltimore) 2016; 95:e5336. [PMID: 27861362 PMCID: PMC5120919 DOI: 10.1097/md.0000000000005336] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Mu-opioid-receptor antagonists have been extensively studied in experimental research as pharmacological tools uncovering mechanisms of pain modulation by the endogenous opioid system. In rodents, administration of high doses of mu-opioid-receptor antagonists after the resolution of an inflammatory injury has demonstrated reinstatement of nociceptive hypersensitivity indicating unmasking of latent sensitization. In a recent human study, pain hypersensitivity assessed as secondary hyperalgesia area (SHA), was reinstated 7 days after a mild thermal injury, in 4 out of 12 subjects after a naloxone infusion.The aims of the present study are first, to replicate our previous findings in a larger-sized study; second, to examine if high sensitizers (subjects presenting with large SHA after a thermal injury) develop a higher degree of hypersensitivity after naloxone challenge than low sensitizers (subjects presenting with restricted SHA after a thermal injury); and third to examine a dose-response relationship between 3 stable naloxone concentrations controlled by target-controlled infusion, and the unmasking of latent sensitization.Healthy participants (n = 80) underwent a screening day (day 0) with induction of a thermal skin injury (47°C, 420 seconds, 12.5 cm). Assessment of SHA was performed 1 and 2 hours after the injury. Using an enriched design, only participants belonging to the upper quartile of SHA (Q4, high sensitizers; n = 20) and the lower quartile of SHA (Q1, low sensitizers; n = 20) continued the study, comprising 4 consecutive days-days 1 to 4. Thermal skin injuries were repeated on day 1 and day 3, whereas day 2 and day 4 (7 days after day 1 and day 3, respectively) were target-controlled infusion days in which the subjects were randomly allocated to receive either naloxone (3.25 mg/kg, 4 mg/mL) or placebo (normal saline) intravenous. The primary outcome was SHA assessed by weighted-pin instrument (128 mN) 0, 1, 2, and 165 to 169 hours after the thermal injury (day 1-4). The secondary outcomes were pin-prick pain thresholds assessed by weighted-pin instrument (8-512 mN) at primary and secondary hyperalgesia areas (days 1-4).The naloxone-induced unmasking of latent sensitization is an interesting model for exploring the transition from acute to chronic pain. The results from the present study may provide valuable information regarding future research in persistent postsurgical pain states.
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Affiliation(s)
| | | | - Bradley K. Taylor
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY
| | - Mads U. Werner
- Neuroscience Center, Copenhagen University Hospitals, Copenhagen, Denmark
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11
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Drake RAR, Leith JL, Almahasneh F, Martindale J, Wilson AW, Lumb B, Donaldson LF. Periaqueductal Grey EP3 Receptors Facilitate Spinal Nociception in Arthritic Secondary Hypersensitivity. J Neurosci 2016; 36:9026-40. [PMID: 27581447 PMCID: PMC5005717 DOI: 10.1523/jneurosci.4393-15.2016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Revised: 06/17/2016] [Accepted: 06/22/2016] [Indexed: 02/06/2023] Open
Abstract
UNLABELLED Descending controls on spinal nociceptive processing play a pivotal role in shaping the pain experience after tissue injury. Secondary hypersensitivity develops within undamaged tissue adjacent and distant to damaged sites. Spinal neuronal pools innervating regions of secondary hypersensitivity are dominated by descending facilitation that amplifies spinal inputs from unsensitized peripheral nociceptors. Cyclooxygenase-prostaglandin (PG) E2 signaling within the ventrolateral periaqueductal gray (vlPAG) is pronociceptive in naive and acutely inflamed animals, but its contributions in more prolonged inflammation and, importantly, secondary hypersensitivity remain unknown. In naive rats, PG EP3 receptor (EP3R) antagonism in vlPAG modulated noxious withdrawal reflex (EMG) thresholds to preferential C-nociceptor, but not A-nociceptor, activation and raised thermal withdrawal thresholds in awake animals. In rats with inflammatory arthritis, secondary mechanical and thermal hypersensitivity of the hindpaw developed and was associated with spinal sensitization to A-nociceptor inputs alone. In arthritic rats, blockade of vlPAG EP3R raised EMG thresholds to C-nociceptor activation in the area of secondary hypersensitivity to a degree equivalent to that evoked by the same manipulation in naive rats. Importantly, vlPAG EP3R blockade also affected responses to A-nociceptor activation, but only in arthritic animals. We conclude that vlPAG EP3R activity exerts an equivalent facilitation on the spinal processing of C-nociceptor inputs in naive and arthritic animals, but gains in effects on spinal A-nociceptor processing from a region of secondary hypersensitivity. Therefore, the spinal sensitization to A-nociceptor inputs associated with secondary hypersensitivity is likely to be at least partly dependent on descending prostanergic facilitation from the vlPAG. SIGNIFICANCE STATEMENT After tissue damage, sensitivity to painful stimulation develops in undamaged areas (secondary hypersensitivity). This is found in many painful conditions, particularly arthritis. The periaqueductal gray (PAG) is an important center that controls spinal nociceptive processing, on which secondary hypersensitivity depends. Prostaglandins (PGs) are mediators of inflammation with pronociceptive actions within the PAG under normal conditions. We find that secondary hindpaw hypersensitivity in arthritic rats results from spinal sensitization to peripheral A-nociceptor inputs. In the PAG of arthritic, but not naive, rats, there is enhanced control of spinal A-nociceptor processing through PG EP3 receptors. The descending facilitatory actions of intra-PAG PGs play a direct and central role in the maintenance of inflammatory secondary hypersensitivity, particularly relating to the processing of A-fiber nociceptive information.
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MESH Headings
- Animals
- Anti-Inflammatory Agents, Non-Steroidal/pharmacology
- Area Under Curve
- Arthritis/chemically induced
- Arthritis/complications
- Disease Models, Animal
- Freund's Adjuvant/toxicity
- Hyperalgesia/physiopathology
- Ketoprofen/pharmacology
- Male
- Nerve Fibers, Myelinated/physiology
- Nerve Fibers, Unmyelinated/physiology
- Neurons/drug effects
- Nitriles/pharmacology
- Nociception/drug effects
- Nociception/physiology
- Pain Measurement/methods
- Pain Threshold/physiology
- Periaqueductal Gray/drug effects
- Periaqueductal Gray/metabolism
- RNA, Messenger/metabolism
- Rats
- Rats, Wistar
- Receptors, Prostaglandin E, EP3 Subtype/antagonists & inhibitors
- Receptors, Prostaglandin E, EP3 Subtype/metabolism
- Spinal Cord/metabolism
- Spinal Cord/pathology
- Statistics, Nonparametric
- Sulfonamides/pharmacology
- Time Factors
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Affiliation(s)
- R A R Drake
- School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - J L Leith
- School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - F Almahasneh
- Arthritis Research UK Pain Centre and School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, United Kingdom, and
| | - J Martindale
- Neurosciences CEDD, GlaxoSmithKline, Harlow CM19 5AW, United Kingdom
| | - A W Wilson
- Neurosciences CEDD, GlaxoSmithKline, Harlow CM19 5AW, United Kingdom
| | - B Lumb
- School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - L F Donaldson
- School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom, Arthritis Research UK Pain Centre and School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, United Kingdom, and
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12
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van den Broeke EN, Lenoir C, Mouraux A. Secondary hyperalgesia is mediated by heat-insensitive A-fibre nociceptors. J Physiol 2016; 594:6767-6776. [PMID: 27377467 DOI: 10.1113/jp272599] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 07/01/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS It is believed that secondary hyperalgesia (the increased sensitivity to mechanical nociceptive stimuli that develops after cutaneous tissue injury in the surrounding uninjured skin) is mediated by a subclass of nociceptors: the slowly adapting A-fibre mechano-heat nociceptors (AMH-type I). Here we tested this hypothesis. By using intense long-lasting heat stimuli, which are known to activate these slowly adapting AMH-type I nociceptors, we show that the perceived intensity elicited by these stimuli is not increased in the area of secondary hyperalgesia. Moreover, we show that during an A-fibre nerve conduction block the perception elicited by the long-lasting heat stimuli is significantly reduced in a time window that matches the response profile of the AMH-type I nociceptors. AMH-type I nociceptors contribute to the perception of sustained heat, but they do not mediate secondary hyperalgesia. Therefore, we propose that secondary hyperalgesia is mediated by high threshold mechanoreceptors. ABSTRACT Secondary hyperalgesia refers to the increase in sensitivity to mechanical nociceptive stimuli delivered outside the area of tissue injury. Previous studies have suggested that secondary hyperalgesia is mediated by a specific class of myelinated nociceptors: slowly adapting A-fibre mechano- and heat-sensitive (AMH) type I nociceptors. Here, we tested this hypothesis by examining whether long-lasting heat stimuli, which are known to activate AMH-type I nociceptors, elicit enhanced responses when delivered to the area of secondary hyperalgesia induced by high frequency electrical stimulation of the skin (HFS). Before and 20 min after HFS, sustained 30 s radiant heat stimuli were delivered to the area of increased mechanical pinprick sensitivity while participants continuously rated intensity of perception using an online visual analog scale (0-100 mm). After HFS, no significant enhancement of heat perception was observed in the area of increased pinprick sensitivity. To establish that myelinated nociceptors actually contribute to the perception of sustained heat, we conducted a second experiment in which sustained heat stimuli were presented before and during an A-fibre nerve conduction block, achieved by applying a rubber band with weights which compresses the superficial radial nerve against the radius. During the block, heat perception was significantly reduced 17-33 s after the onset of the heat stimulus (before: mean = 53 mm, during: mean = 31 mm; P = 0.03), matching the response profile of AMH-type I nociceptors. These results support the notion that AMH-type I nociceptors contribute to the perception of sustained heat, but also show that these afferents do not mediate secondary hyperalgesia.
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Affiliation(s)
| | - Cédric Lenoir
- Institute of Neuroscience, Université catholique de Louvain, B-1200, Brussels, Belgium
| | - André Mouraux
- Institute of Neuroscience, Université catholique de Louvain, B-1200, Brussels, Belgium
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13
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Liang M, Lee MC, O'Neill J, Dickenson AH, Iannetti GD. Brain potentials evoked by intraepidermal electrical stimuli reflect the central sensitization of nociceptive pathways. J Neurophysiol 2016; 116:286-95. [PMID: 27098022 PMCID: PMC4969393 DOI: 10.1152/jn.00013.2016] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 04/14/2016] [Indexed: 01/19/2023] Open
Abstract
Secondary mechanical punctate hyperalgesia is a cardinal sign of central sensitization (CS), an important mechanism of chronic pain. Our study demonstrates that hyperalgesia from intraepidermal electrical stimulation coexists with mechanical punctate hyperalgesia and elicits electroencephalographic (EEG) potentials that predict the occurrence of punctate hyperalgesia in a human experimental model of CS. These findings inform clinical development of EEG-based biomarkers of CS. Central sensitization (CS), the increased sensitivity of the central nervous system to somatosensory inputs, accounts for secondary hyperalgesia, a typical sign of several painful clinical conditions. Brain potentials elicited by mechanical punctate stimulation using flat-tip probes can provide neural correlates of CS, but their signal-to-noise ratio is limited by poor synchronization of the afferent nociceptive input. Additionally, mechanical punctate stimulation does not activate nociceptors exclusively. In contrast, low-intensity intraepidermal electrical stimulation (IES) allows selective activation of type II Aδ-mechano-heat nociceptors (II-AMHs) and elicits reproducible brain potentials. However, it is unclear whether hyperalgesia from IES occurs and coexists with secondary mechanical punctate hyperalgesia, and whether the magnitude of the electroencephalographic (EEG) responses evoked by IES within the hyperalgesic area is increased. To address these questions, we explored the modulation of the psychophysical and EEG responses to IES by intraepidermal injection of capsaicin in healthy human subjects. We obtained three main results. First, the intensity of the sensation elicited by IES was significantly increased in participants who developed robust mechanical punctate hyperalgesia after capsaicin injection (i.e., responders), indicating that hyperalgesia from IES coexists with punctate mechanical hyperalgesia. Second, the N2 peak magnitude of the EEG responses elicited by IES was significantly increased after the intraepidermal injection of capsaicin in responders only. Third, a receiver-operator characteristics analysis showed that the N2 peak amplitude is clearly predictive of the presence of CS. These findings suggest that the EEG responses elicited by IES reflect secondary hyperalgesia and therefore represent an objective correlate of CS.
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Affiliation(s)
- M Liang
- School of Medical Imaging, Tianjin Medical University, Tianjin, China; Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom; and
| | - M C Lee
- Division of Anaesthesia, University of Cambridge, Cambridge, United Kingdom
| | - J O'Neill
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom; and
| | - A H Dickenson
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom; and
| | - G D Iannetti
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom; and
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14
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Maracle EC, Hung LY, Fell SI, Osmond MR, Brown SHM, Srbely JZ. A Comparison of the Sensitivity of Brush Allodynia and Semmes-Weinstein Monofilament Testing in the Detection of Allodynia Within Regions of Secondary Hyperalgesia in Humans. Pain Pract 2016; 17:16-24. [PMID: 26936430 DOI: 10.1111/papr.12418] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 10/22/2015] [Indexed: 01/04/2023]
Abstract
BACKGROUND Two of the most common Quantitative Sensory Techniques (QST) employed to detect allodynia include mechanical brush allodynia and Semmes-Weinstein monofilaments. However, their relative sensitivity at detecting allodynia is poorly understood. The purpose of this study was to compare the sensitivity of brush allodynia against Semmes-Weinstein monofilament technique for detecting allodynia within regions of secondary hyperalgesia in humans. METHODS Twenty subjects (10 males, 10 females; 21.1 ± 0.9 years) were recruited and randomly allocated to allodynia or monofilament groups. Topical capsaicin (Zostrix 0.075%) was applied to a target region defined by C4-C7 dermatomes. Allodynia testing was performed at 0- (baseline) and 10 minutes postcapsaicin. The Semmes-Weinstein group assessed changes in skin sensitivity 8 cm inferior to target region and 2 cm lateral to the spinous process, while brush allodynia was employed to detect the point inferior to the target region where subjects reported changes in skin sensitivity. The distance (cm) from this point to the inferior border of the target region was termed the Allodynia Score. RESULTS Statistically significant increases in the Allodynia Score were observed at 10 minutes postcapsaicin compared to baseline (P < 0.001). No differences in monofilament scores were observed between 10 minutes postcapsaicin and baseline (P = 0.125). Brush allodynia also demonstrated superior sensitivity, detecting allodynia in 100% of cases compared to 60% in the Semmes-Weinstein group. CONCLUSION Brush allodynia is more sensitive than Semmes-Weinstein monofilaments for detecting mechanical allodynia in regions of secondary hyperalgesia. Brush allodynia may be preferred over Semmes-Weinstein monofilaments for clinical applications requiring reliable detection of allodynia.
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Affiliation(s)
- Emmalee C Maracle
- Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Laurie Y Hung
- Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Sabrina I Fell
- Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Michael R Osmond
- Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Stephen H M Brown
- Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - John Z Srbely
- Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
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15
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van den Broeke EN, Mouraux A, Groneberg AH, Pfau DB, Treede RD, Klein T. Characterizing pinprick-evoked brain potentials before and after experimentally induced secondary hyperalgesia. J Neurophysiol 2015; 114:2672-81. [PMID: 26334010 DOI: 10.1152/jn.00444.2015] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 08/31/2015] [Indexed: 11/22/2022] Open
Abstract
Secondary hyperalgesia is believed to be a key feature of "central sensitization" and is characterized by enhanced pain to mechanical nociceptive stimuli. The aim of the present study was to characterize, using EEG, the effects of pinprick stimulation intensity on the magnitude of pinprick-elicited brain potentials [event-related potentials (ERPs)] before and after secondary hyperalgesia induced by intradermal capsaicin in humans. Pinprick-elicited ERPs and pinprick-evoked pain ratings were recorded in 19 healthy volunteers, with mechanical pinprick stimuli of varying intensities (0.25-mm probe applied with a force extending between 16 and 512 mN). The recordings were performed before (T0) and 30 min after (T1) intradermal capsaicin injection. The contralateral noninjected arm served as control. ERPs elicited by stimulation of untreated skin were characterized by 1) an early-latency negative-positive complex peaking between 120 and 250 ms after stimulus onset (N120-P240) and maximal at the vertex and 2) a long-lasting positive wave peaking 400-600 ms after stimulus onset and maximal more posterior (P500), which was correlated to perceived pinprick pain. After capsaicin injection, pinprick stimuli were perceived as more intense in the area of secondary hyperalgesia and this effect was stronger for lower compared with higher stimulus intensities. In addition, there was an enhancement of the P500 elicited by stimuli of intermediate intensity, which was significant for 64 mN. The other components of the ERPs were unaffected by capsaicin. Our results suggest that the increase in P500 magnitude after capsaicin is mediated by facilitated mechanical nociceptive pathways.
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Affiliation(s)
| | - André Mouraux
- Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium; and
| | - Antonia H Groneberg
- Division of Neurophysiology, Center for Biomedicine and Medical Technology Mannheim (CBTM), Heidelberg University, Mannheim, Germany
| | - Doreen B Pfau
- Division of Neurophysiology, Center for Biomedicine and Medical Technology Mannheim (CBTM), Heidelberg University, Mannheim, Germany
| | - Rolf-Detlef Treede
- Division of Neurophysiology, Center for Biomedicine and Medical Technology Mannheim (CBTM), Heidelberg University, Mannheim, Germany
| | - Thomas Klein
- Division of Neurophysiology, Center for Biomedicine and Medical Technology Mannheim (CBTM), Heidelberg University, Mannheim, Germany
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16
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van den Broeke EN, Mouraux A. Enhanced brain responses to C-fiber input in the area of secondary hyperalgesia induced by high-frequency electrical stimulation of the skin. J Neurophysiol 2014; 112:2059-66. [PMID: 25098966 DOI: 10.1152/jn.00342.2014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
High-frequency electrical stimulation (HFS) of the human skin induces an increase in both mechanical and heat pain sensitivity in the surrounding unconditioned skin. The aim of this study was to investigate the effect of HFS on the intensity of perception and brain responses elicited by the selective activation of C fibers. HFS was applied to the ventral forearm of 15 healthy volunteers. Temperature-controlled CO2 laser stimulation was used to activate selectively low-threshold C-fiber afferents without concomitantly activating Aδ-fiber afferents. These stimuli were detected with reaction times compatible with the conduction velocity of C fibers. The intensity of perception and event-related brain potentials (ERPs) elicited by thermal stimuli delivered to the surrounding unconditioned skin were recorded before (T0) and after HFS (T1: 20 min after HFS; T2: 45 min after HFS). The contralateral forearm served as a control. Mechanical hyperalgesia following HFS was confirmed by measuring the change in the intensity of perception elicited by mechanical punctate stimuli. HFS resulted in increased intensity of perception to mechanical punctate stimulation and selective C-fiber thermal stimulation at both time points. In contrast, the N2 wave of the ERP elicited by C-fiber stimulation (679 ± 88 ms; means ± SD) was enhanced at T1 but not at T2. The P2 wave (808 ± 105 ms) was unaffected by HFS. Our results suggest that HFS enhances the sensitivity to thermal C-fiber input in the area of secondary hyperalgesia. However, there was no significant enhancement of the magnitude of the C-fiber ERPs at T2, suggesting that quickly adapting C fibers do not contribute to this enhancement.
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Affiliation(s)
- Emanuel N van den Broeke
- Institute of Neuroscience, Faculty of Medicine, Université Catholique de Louvain, Brussels, Belgium
| | - André Mouraux
- Institute of Neuroscience, Faculty of Medicine, Université Catholique de Louvain, Brussels, Belgium
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17
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van den Broeke EN, Mouraux A. High-frequency electrical stimulation of the human skin induces heterotopical mechanical hyperalgesia, heat hyperalgesia, and enhanced responses to nonnociceptive vibrotactile input. J Neurophysiol 2014; 111:1564-73. [PMID: 24453277 DOI: 10.1152/jn.00651.2013] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
High-frequency electrical stimulation (HFS) of the human skin induces increased pain sensitivity in the surrounding unconditioned skin. The aim of the present study was to characterize the relative contribution of the different types of nociceptive and nonnociceptive afferents to the heterotopical hyperalgesia induced by HFS. In 17 healthy volunteers (9 men and 8 women), we applied HFS to the ventral forearm. The intensity of perception and event-related brain potentials (ERPs) elicited by vibrotactile stimuli exclusively activating nonnociceptive low-threshold mechanoreceptors and thermonociceptive stimuli exclusively activating heat-sensitive nociceptive afferents were recorded before and after HFS. The previously described mechanical hyperalgesia following HFS was confirmed by measuring the changes in the intensity of perception elicited by mechanical punctate stimuli. HFS increased the perceived intensity of both mechanical punctate and thermonociceptive stimuli applied to the surrounding unconditioned skin. The time course of the effect of HFS on the perception of mechanical and thermal nociceptive stimuli was similar. This indicates that HFS does not only induce mechanical hyperalgesia, but also induces heat hyperalgesia in the heterotopical area. Vibrotactile ERPs were also enhanced after HFS, indicating that nonnociceptive somatosensory input could contribute to the enhanced responses to mechanical pinprick stimuli. Finally, the magnitude of thermonociceptive ERPs was unaffected by HFS, indicating that type II A-fiber mechano-heat nociceptors, thought to be the primary contributor to these brain responses, do not significantly contribute to the observed heat hyperalgesia.
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Affiliation(s)
- Emanuel N van den Broeke
- Institute of Neuroscience, Faculty of Medicine, Université Catholique de Louvain, Brussels, Belgium
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18
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Mørch CD, Gazerani P, Nielsen TA, Arendt-Nielsen L. The UVB cutaneous inflammatory pain model: a reproducibility study in healthy volunteers. Int J Physiol Pathophysiol Pharmacol 2013; 5:203-215. [PMID: 24379905 PMCID: PMC3867698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Accepted: 11/12/2013] [Indexed: 06/03/2023]
Abstract
BACKGROUND The human ultraviolet-B (UVB) experimental pain model induces cutaneous neurogenic inflammation, involves hyperalgesia, and is widely used as a pharmacological screening pain model. AIM To estimate the test-retest reliability of the UVB pain model by application of a comprehensive set of vasomotor and quantitative sensory assessment methods and to estimate sample sizes required for parallel or crossover pharmacological screening studies when this model is considered to be applied. METHODS The upper arms of 15 healthy male volunteers were UVB irradiated with three times the minimal erythema dose. Neurogenic inflammation was assessed by measuring erythema index, superficial blood flow and skin temperature at baseline, 1 day, 2 days and 3 days post irradiation. Sensory changes were assessed by brush stroke, von Frey hairs, pressure algometry, heat-evoked pain, stimulus response function to weight calibrated pin-prick stimulation, and the area of secondary hyperalgesia. The experiment was repeated with a two-week interval. Systematic bias, Coefficient of variation (CV), and intra-class correlation (ICC) were calculated within and between UVB irradiations. The sample sizes for parallel and crossover studies were calculated. RESULTS Neurogenic inflammation (erythema index) and primary hyperalgesia (pin-prick stimulation) remained significant for 3 days, and were highly reproducible within and between the UVB irradiations resulting of low sample sizes (4-26) in both parallel and crossover studies. CONCLUSION Based on sample size calculations, it is recommended to use the erythema index to assess neurogenic inflammation, and pin-prick stimulation for primary hyperalgesia for both parallel and crossover pharmacological screening studies.
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Affiliation(s)
- Carsten Dahl Mørch
- Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Faculty of Medicine, Aalborg University Denmark
| | - Parisa Gazerani
- Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Faculty of Medicine, Aalborg University Denmark
| | - Thomas A Nielsen
- Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Faculty of Medicine, Aalborg University Denmark
| | - Lars Arendt-Nielsen
- Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Faculty of Medicine, Aalborg University Denmark
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Abstract
The concepts of visceral hyperalgesia and visceral hypersensitivity have been examined in a variety of functional gastrointestinal disorders (FGIDs). Although the pathophysiological mechanisms of pain and hypersensitivity in these disorders are still not well understood, exciting new developments in research have been made in the study of the brain-gut interactions involved in the FGIDs.
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Affiliation(s)
- B Moshiree
- Department of Medicine, University of Florida College of Medicine, Division of Gastroenterology, Hepatology, and Nutrition, 1600 SW Archer Rd, HD 602, PO Box 100214, Gainesville, FL 32610-0214, USA
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