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Yang H, Meijer HGE, Doll RJ, Buitenweg JR, van Gils SA. Dependence of Nociceptive Detection Thresholds on Physiological Parameters and Capsaicin-Induced Neuroplasticity: A Computational Study. Front Comput Neurosci 2016; 10:49. [PMID: 27252644 PMCID: PMC4879143 DOI: 10.3389/fncom.2016.00049] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 05/06/2016] [Indexed: 01/10/2023] Open
Abstract
Physiological properties of peripheral and central nociceptive subsystems can be altered over time due to medical interventions. The effective change for the whole nociceptive system can be reflected in changes of psychophysical characteristics, e.g., detection thresholds. However, it is challenging to separate contributions of distinct altered mechanisms with measurements of thresholds only. Here, we aim to understand how these alterations affect Aδ-fiber-mediated nociceptive detection of electrocutaneous stimuli. First, with a neurophysiology-based model, we study the effects of single-model parameters on detection thresholds. Second, we derive an expression of model parameters determining the functional relationship between detection thresholds and the interpulse interval for double-pulse stimuli. Third, in a case study with topical capsaicin treatment, we translate neuroplasticity into plausible changes of model parameters. Model simulations qualitatively agree with changes in experimental detection thresholds. The simulations with individual forms of neuroplasticity confirm that nerve degeneration is the dominant mechanism for capsaicin-induced increases in detection thresholds. In addition, our study suggests that capsaicin-induced central plasticity may last at least 1 month.
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Affiliation(s)
- Huan Yang
- Applied Analysis, MIRA Institute for Technical Medicine and Biomedical Technology, University of TwenteEnschede, Netherlands
| | - Hil G. E. Meijer
- Applied Analysis, MIRA Institute for Technical Medicine and Biomedical Technology, University of TwenteEnschede, Netherlands
| | - Robert J. Doll
- Biomedical Signals and Systems, MIRA Institute for Technical Medicine and Biomedical Technology, University of TwenteEnschede, Netherlands
| | - Jan R. Buitenweg
- Biomedical Signals and Systems, MIRA Institute for Technical Medicine and Biomedical Technology, University of TwenteEnschede, Netherlands
| | - Stephan A. van Gils
- Applied Analysis, MIRA Institute for Technical Medicine and Biomedical Technology, University of TwenteEnschede, Netherlands
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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] [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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Xia W, Mørch CD, Andersen OK. Exploration of the conditioning electrical stimulation frequencies for induction of long-term potentiation-like pain amplification in humans. Exp Brain Res 2016; 234:2479-89. [DOI: 10.1007/s00221-016-4653-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 04/13/2016] [Indexed: 01/07/2023]
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Vo L, Drummond PD. Involvement of α2-adrenoceptors in inhibitory and facilitatory pain modulation processes. Eur J Pain 2015; 20:386-98. [PMID: 26032281 DOI: 10.1002/ejp.736] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/02/2015] [Indexed: 12/19/2022]
Abstract
BACKGROUND In healthy humans, high-frequency electrical stimulation (HFS) of the forearm not only produces hyperalgesia at the site of stimulation but also reduces sensitivity to pressure-pain on the ipsilateral side of the forehead. In addition, HFS augments the ipsilateral trigeminal nociceptive blink reflex and intensifies the ipsilateral component of conditioned pain modulation. The aim of this study was to determine whether α2-adrenoceptors mediate these ipsilateral nociceptive influences. METHODS The α2-adrenoceptor antagonist yohimbine was administered to 22 participants in a double-blind, placebo-controlled crossover study. In each session, thermal and mechanical sensitivity in the forearms and forehead was assessed before and after HFS. In addition, the combined effect of HFS and yohimbine on the nociceptive blink reflex and on conditioned pain modulation was explored. In this paradigm, the conditioning stimulus was cold pain in the ipsilateral or contralateral temple, and the test stimulus was electrically evoked pain in the forearm. RESULTS Blood pressure and electrodermal activity increased for several hours after yohimbine administration, consistent with blockade of central α2-adrenoceptors. Yohimbine not only augmented the nociceptive blink reflex ipsilateral to HFS but also intensified the inhibitory influence of ipsilateral temple cooling on electrically evoked pain at the HFS-treated site in the forearm. Yohimbine had no consistent effect on primary or secondary hyperalgesia in the forearm or on pressure-pain in the ipsilateral forehead. CONCLUSIONS These findings imply involvement of α2-adrenoceptors both in ipsilateral antinociceptive and pronociceptive pain modulation processes. However, a mechanism not involving α2-adrenoceptors appears to mediate analgesia in the ipsilateral forehead after HFS.
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Affiliation(s)
- L Vo
- Centre for Research on Chronic Pain and Inflammatory Diseases, Murdoch University, Perth, WA, Australia
| | - P D Drummond
- Centre for Research on Chronic Pain and Inflammatory Diseases, Murdoch University, Perth, WA, Australia
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Henrich F, Magerl W, Klein T, Greffrath W, Treede RD. Capsaicin-sensitive C- and A-fibre nociceptors control long-term potentiation-like pain amplification in humans. Brain 2015; 138:2505-20. [DOI: 10.1093/brain/awv108] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 02/24/2015] [Indexed: 01/08/2023] Open
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Tada H, Torisu T, Tanaka M, Murata H, De Laat A, Svensson P. Experimental low-level jaw clenching inhibits temporal summation evoked by electrical stimulation in healthy human volunteers. Arch Oral Biol 2015; 60:681-9. [PMID: 25757146 DOI: 10.1016/j.archoralbio.2015.02.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Revised: 01/31/2015] [Accepted: 02/11/2015] [Indexed: 01/12/2023]
Abstract
OBJECTIVE To examine the effect of low-level jaw clenching on temporal summation in healthy volunteers. DESIGN In 18 healthy volunteers, the pain intensities evoked at the masseter muscle and the hand palm by the first and last stimuli in a train of repeated electrical stimuli (0.3 or 2.0 Hz) were rated using 0-100mm visual analogue scales (VAS), in order to evaluate temporal summation before and after three types of jaw-muscle tasks: low-level jaw clenching, repetitive gum chewing and mandibular rest position. A set of concentric surface electrodes with different diameters (small and large) was used for the electrical stimulation. RESULTS The temporal summation evoked by the large diameter electrode with 2.0 Hz stimulation decreased significantly both on the masseter and the hand after low-level clenching (P ≤ 0.03), but did not show any significant change after the other tasks (P > 0.23). The VAS score of the first stimulation did not show any significant changes after low-level clenching (P > 0.57). CONCLUSIONS Experimental low-level jaw clenching can inhibit pain sensitivity, especially temporal summation. Low-level jaw clenching can modify pain sensitivity, most likely through the central nervous system. The findings suggest that potential harmful low-level jaw clenching or tooth contacting could continue despite painful symptoms, e.g., temporomandibular disorders.
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Affiliation(s)
- Hiroaki Tada
- Department of Prosthetic Dentistry, Graduate School of Biomedical Sciences, Nagasaki University, Sakamoto 1-7-1, Nagasaki 852-8588, Japan.
| | - Tetsurou Torisu
- Department of Prosthetic Dentistry, Graduate School of Biomedical Sciences, Nagasaki University, Sakamoto 1-7-1, Nagasaki 852-8588, Japan.
| | - Mihoko Tanaka
- Department of Prosthetic Dentistry, Graduate School of Biomedical Sciences, Nagasaki University, Sakamoto 1-7-1, Nagasaki 852-8588, Japan.
| | - Hiroshi Murata
- Department of Prosthetic Dentistry, Graduate School of Biomedical Sciences, Nagasaki University, Sakamoto 1-7-1, Nagasaki 852-8588, Japan.
| | - Antoon De Laat
- Department of Oral Health Sciences, KU Leuven, Belgium; Dentistry, University Hospitals Leuven, Kapucijnenvoer, B-3000 Leuven, Belgium.
| | - Peter Svensson
- Section of Clinical Oral Physiology, School of Dentistry, Aarhus University, Aarhus, Denmark; Scandinavian Center for Orofacial Neurosciences (SCON), Vennelyst Boulevard 9, 8000 Aarhus C, Denmark; Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden.
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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: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [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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An improved model of heat-induced hyperalgesia--repetitive phasic heat pain causing primary hyperalgesia to heat and secondary hyperalgesia to pinprick and light touch. PLoS One 2014; 9:e99507. [PMID: 24911787 PMCID: PMC4050052 DOI: 10.1371/journal.pone.0099507] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Accepted: 05/02/2014] [Indexed: 01/31/2023] Open
Abstract
This study tested a modified experimental model of heat-induced hyperalgesia, which improves the efficacy to induce primary and secondary hyperalgesia and the efficacy-to-safety ratio reducing the risk of tissue damage seen in other heat pain models. Quantitative sensory testing was done in eighteen healthy volunteers before and after repetitive heat pain stimuli (60 stimuli of 48°C for 6 s) to assess the impact of repetitive heat on somatosensory function in conditioned skin (primary hyperalgesia area) and in adjacent skin (secondary hyperalgesia area) as compared to an unconditioned mirror image control site. Additionally, areas of flare and secondary hyperalgesia were mapped, and time course of hyperalgesia determined. After repetitive heat pain conditioning we found significant primary hyperalgesia to heat, and primary and secondary hyperalgesia to pinprick and to light touch (dynamic mechanical allodynia). Acetaminophen (800 mg) reduced pain to heat or pinpricks only marginally by 11% and 8%, respectively (n.s.), and had no effect on heat hyperalgesia. In contrast, the areas of flare (−31%) and in particular of secondary hyperalgesia (−59%) as well as the magnitude of hyperalgesia (−59%) were significantly reduced (all p<0.001). Thus, repetitive heat pain induces significant peripheral sensitization (primary hyperalgesia to heat) and central sensitization (punctate hyperalgesia and dynamic mechanical allodynia). These findings are relevant to further studies using this model of experimental heat pain as it combines pronounced peripheral and central sensitization, which makes a convenient model for combined pharmacological testing of analgesia and anti-hyperalgesia mechanisms related to thermal and mechanical input.
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Fischer M, Carli G, Raboisson P, Reeh P. The interphase of the formalin test. Pain 2014; 155:511-521. [DOI: 10.1016/j.pain.2013.11.015] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Revised: 11/21/2013] [Accepted: 11/21/2013] [Indexed: 10/26/2022]
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Yang G, Baad-Hansen L, Wang K, Xie QF, Svensson P. A study on variability of quantitative sensory testing in healthy participants and painful temporomandibular disorder patients. Somatosens Mot Res 2014; 31:62-71. [DOI: 10.3109/08990220.2013.869493] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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61
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Baron R, Hans G, Dickenson AH. Peripheral input and its importance for central sensitization. Ann Neurol 2013; 74:630-6. [DOI: 10.1002/ana.24017] [Citation(s) in RCA: 174] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 08/13/2013] [Accepted: 08/27/2013] [Indexed: 11/09/2022]
Affiliation(s)
- Ralf Baron
- Division of Neurological Pain Research and Therapy; Schleswig-Holstein University Hospital; Kiel Germany
| | - Guy Hans
- Multidisciplinary Pain Center; Antwerp University Hospital; Edegem Belgium
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Vo L, Drummond PD. Analgesia to pressure–pain develops in the ipsilateral forehead after high- and low-frequency electrical stimulation of the forearm. Exp Brain Res 2013; 232:685-93. [DOI: 10.1007/s00221-013-3776-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2013] [Accepted: 11/10/2013] [Indexed: 12/13/2022]
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63
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Stiasny-Kolster K, Pfau DB, Oertel WH, Treede RD, Magerl W. Hyperalgesia and functional sensory loss in restless legs syndrome. Pain 2013; 154:1457-63. [DOI: 10.1016/j.pain.2013.05.007] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Revised: 04/19/2013] [Accepted: 05/03/2013] [Indexed: 11/17/2022]
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Vo L, Drummond PD. Coexistence of ipsilateral pain-inhibitory and facilitatory processes after high-frequency electrical stimulation. Eur J Pain 2013; 18:376-85. [PMID: 23868187 DOI: 10.1002/j.1532-2149.2013.00370.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/20/2013] [Indexed: 12/19/2022]
Abstract
BACKGROUND High-frequency electrical stimulation (HFS) of the human forearm evokes analgesia to blunt pressure in the ipsilateral forehead, consistent with descending ipsilateral inhibitory pain modulation. The aim of the current study was to further delineate pain modulation processes evoked by HFS by examining sensory changes in the arm and forehead; investigating the effects of HFS on nociceptive blink reflexes elicited by supraorbital electrical stimulation; and assessing effects of counter-irritation (electrically evoked pain at the HFS-conditioned site in the forearm) on nociceptive blink reflexes before and after HFS. METHODS Before and after HFS conditioning, sensitivity to heat and to blunt and sharp stimuli was assessed at and adjacent to the conditioned site in the forearm and on each side of the forehead. Nociceptive blink reflexes were also assessed before and after HFS with and without counter-irritation of the forearm. RESULTS HFS triggered secondary hyperalgesia in the forearm (a sign of central sensitization) and analgesia to blunt pressure in the ipsilateral forehead. Under most conditions, both HFS conditioning and counter-irritation of the forearm suppressed electrically evoked pain in the forehead, and the amplitude of the blink reflex to supraorbital stimuli decreased. Importantly, however, in the absence of forearm counter-irritation, HFS conditioning facilitated ipsilateral blink reflex amplitude to supraorbital stimuli delivered ipsilateral to the HFS-conditioned site. CONCLUSIONS These findings suggest that HFS concurrently triggers hemilateral inhibitory and facilitatory influences on nociceptive processing over and above more general effects of counter-irritation. The inhibitory influence may help limit the spread of sensitization in central nociceptive pathways.
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Affiliation(s)
- L Vo
- Centre for Research on Chronic Pain and Inflammatory Diseases, School of Psychology and Exercise Science, Murdoch University, Perth, WA, Australia
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Werner MU, Petersen KL, Rowbotham MC, Dahl JB. Healthy volunteers can be phenotyped using cutaneous sensitization pain models. PLoS One 2013; 8:e62733. [PMID: 23671631 PMCID: PMC3650051 DOI: 10.1371/journal.pone.0062733] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2013] [Accepted: 03/25/2013] [Indexed: 11/24/2022] Open
Abstract
Background Human experimental pain models leading to development of secondary hyperalgesia are used to estimate efficacy of analgesics and antihyperalgesics. The ability to develop an area of secondary hyperalgesia varies substantially between subjects, but little is known about the agreement following repeated measurements. The aim of this study was to determine if the areas of secondary hyperalgesia were consistently robust to be useful for phenotyping subjects, based on their pattern of sensitization by the heat pain models. Methods We performed post-hoc analyses of 10 completed healthy volunteer studies (n = 342 [409 repeated measurements]). Three different models were used to induce secondary hyperalgesia to monofilament stimulation: the heat/capsaicin sensitization (H/C), the brief thermal sensitization (BTS), and the burn injury (BI) models. Three studies included both the H/C and BTS models. Results Within-subject compared to between-subject variability was low, and there was substantial strength of agreement between repeated induction-sessions in most studies. The intraclass correlation coefficient (ICC) improved little with repeated testing beyond two sessions. There was good agreement in categorizing subjects into ‘small area’ (1st quartile [<25%]) and ‘large area’ (4th quartile [>75%]) responders: 56–76% of subjects consistently fell into same ‘small-area’ or ‘large-area’ category on two consecutive study days. There was moderate to substantial agreement between the areas of secondary hyperalgesia induced on the same day using the H/C (forearm) and BTS (thigh) models. Conclusion Secondary hyperalgesia induced by experimental heat pain models seem a consistent measure of sensitization in pharmacodynamic and physiological research. The analysis indicates that healthy volunteers can be phenotyped based on their pattern of sensitization by the heat [and heat plus capsaicin] pain models.
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Affiliation(s)
- Mads U Werner
- Multidisciplinary Pain Center, Neuroscience Center, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.
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Somatosensory abnormalities for painful and innocuous stimuli at the back and at a site distinct from the region of pain in chronic back pain patients. PLoS One 2013; 8:e58885. [PMID: 23554950 PMCID: PMC3598908 DOI: 10.1371/journal.pone.0058885] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 02/07/2013] [Indexed: 01/29/2023] Open
Abstract
Chronic low back pain (CLBP) was shown to be associated with pathophysiological changes at several levels of the sensorimotor system. Changes in sensory thresholds have been reported but complete profiles of Quantitative Sensory Testing (QST) were only rarely obtained in CLBP patients. The aim of the present study was to investigate comprehensive QST profiles in CLBP at the painful site (back) and at a site distinct from their painful region (hand) and to compare these data with similar data in healthy controls. We found increased detection thresholds in CLBP patients compared to healthy controls for all innocuous stimuli at the back and extraterritorial to the painful region at the hand. Additionally, CLBP patients showed decreased pain thresholds at both sites. Importantly, there was no interaction between the investigated site and group, i.e. thresholds were changed both at the affected body site and for the site distinct from the painful region (hand). Our results demonstrate severe, widespread changes in somatosensory sensitivity in CLBP patients. These widespread changes point to alterations at higher levels of the neuraxis or/and to a vulnerability to nociceptive plasticity in CLBP patients.
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Bhangoo SK, Swanson GT. Kainate receptor signaling in pain pathways. Mol Pharmacol 2012; 83:307-15. [PMID: 23095167 DOI: 10.1124/mol.112.081398] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Receptors and channels that underlie nociceptive signaling constitute potential sites of intervention for treatment of chronic pain states. The kainate receptor family of glutamate-gated ion channels represents one such candidate set of molecules. They have a prominent role in modulation of excitatory signaling between sensory and spinal cord neurons. Kainate receptors are also expressed throughout central pain neuraxis, where their functional contributions to neural integration are less clearly defined. Pharmacological inhibition or genetic ablation of kainate receptor activity reduces pain behaviors in a number of animal models of chronic pain, and small clinical trials have been conducted using several orthosteric antagonists. This review will cover kainate receptor function and participation in pain signaling as well as the pharmacological studies supporting further consideration as potential targets for therapeutic development.
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Affiliation(s)
- Sonia K Bhangoo
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
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68
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Vo L, Drummond PD. High frequency electrical stimulation concurrently induces central sensitization and ipsilateral inhibitory pain modulation. Eur J Pain 2012; 17:357-68. [PMID: 22893547 DOI: 10.1002/j.1532-2149.2012.00208.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/17/2012] [Indexed: 12/18/2022]
Abstract
BACKGROUND In healthy humans, analgesia to blunt pressure develops in the ipsilateral forehead during various forms of limb pain. The aim of the current study was to determine whether this analgesic response is induced by ultraviolet B radiation (UVB), which evokes signs of peripheral sensitization, or by high-frequency electrical stimulation (HFS), which triggers signs of central sensitization. METHODS Before and after HFS and UVB conditioning, sensitivity to heat and to blunt and sharp stimuli was assessed at and adjacent to the treated site in the forearm. In addition, sensitivity to blunt pressure was measured bilaterally in the forehead. The effect of ipsilateral versus contralateral temple cooling on electrically evoked pain in the forearm was then examined, to determine whether HFS or UVB conditioning altered inhibitory pain modulation. RESULTS UVB conditioning triggered signs of peripheral sensitization, whereas HFS conditioning triggered signs of central sensitization. Importantly, ipsilateral forehead analgesia developed after HFS but not UVB conditioning. In addition, decreases in electrically evoked pain at the HFS-treated site were greater during ipsilateral than contralateral temple cooling, whereas decreases at the UVB-treated site were similar during both procedures. CONCLUSIONS HFS conditioning induced signs of central sensitization in the forearm and analgesia both in the ipsilateral forehead and the HFS-treated site. This ipsilateral analgesia was not due to peripheral sensitization or other non-specific effects, as it failed to develop after UVB conditioning. Thus, the supra-spinal mechanisms that evoke central sensitization might also trigger a hemilateral inhibitory pain modulation process. This inhibitory process could sharpen the boundaries of central sensitization or limit its spread.
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Affiliation(s)
- L Vo
- School of Psychology, Murdoch University, Perth, WA, Australia
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van den Broeke EN, van Heck CH, Ceelen LAJM, van Rijn CM, van Goor H, Wilder-Smith OHG. The effect of high-frequency conditioning stimulation of human skin on reported pain intensity and event-related potentials. J Neurophysiol 2012; 108:2276-81. [PMID: 22855779 DOI: 10.1152/jn.00391.2012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
High-frequency conditioning electrical stimulation (HFS) of human skin induces an increased pain sensitivity to mechanical stimuli in the surrounding nonconditioned skin. The aim of this study was to investigate the effect of HFS on reported pain sensitivity to single electrical stimuli applied within the area of conditioning stimulation. We also investigated the central nervous system responsiveness to these electrical stimuli by measuring event-related potentials (ERPs). Single electrical test stimuli were applied in the conditioned area before and 30 min after HFS. During electrical test stimulation, the reported pain intensity (numerical rating scale) and EEG (ERPs) were measured. Thirty minutes after conditioning stimulation, we observed a decrease of reported pain intensity at both the conditioned and control (opposite arm) skin site in response to the single electrical test stimuli. In contrast, we observed enhanced ERP amplitudes after HFS at the conditioned skin site, compared with control site, in response to the single electrical test stimuli. Recently, it has been proposed that ERPs, at least partly, reflect a saliency detection system. Therefore, the enhanced ERPs might reflect enhanced saliency to potentially threatening stimuli.
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King T, Qu C, Okun A, Melemedjian OK, Mandell EK, Maskaykina IY, Navratilova E, Dussor GO, Ghosh S, Price TJ, Porreca F. Contribution of PKMζ-dependent and independent amplification to components of experimental neuropathic pain. Pain 2012; 153:1263-1273. [PMID: 22482911 DOI: 10.1016/j.pain.2012.03.006] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 02/24/2012] [Accepted: 03/06/2012] [Indexed: 12/23/2022]
Abstract
Injuries can induce adaptations in pain processing that result in amplification of signaling. One mechanism may be analogous to long-term potentiation and involve the atypical protein kinase C, PKMζ. The possible contribution of PKMζ-dependent and independent amplification mechanisms to experimental neuropathic pain was explored in rats with spinal nerve ligation (SNL) injury. SNL increased p-PKMζ in the rostral anterior cingulate cortex (rACC), a site that mediates, in part, the unpleasant aspects of pain. Inhibition of PKMζ within the rACC by a single administration of ζ-pseudosubstrate inhibitory peptide (ZIP) reversed SNL-induced aversiveness within 24 hours, whereas N-methyl-d-aspartate receptor blockade with MK-801 had no effects. The SNL-induced aversive state (reflecting "spontaneous" pain), was re-established in a time-dependent manner, with full recovery observed 7 days post-ZIP administration. Neither rACC ZIP nor MK-801 altered evoked responses. In contrast, spinal ZIP or MK-801, but not scrambled peptide, transiently reversed evoked hypersensitivity, but had no effect on nerve injury-induced spontaneous pain. PKMζ phosphorylation was not altered by SNL in the spinal dorsal horn. These data suggest that amplification mechanisms contribute to different aspects of neuropathic pain at different levels of the neuraxis. Thus, PKMζ-dependent amplification contributes to nerve injury-induced aversiveness within the rACC. Moreover, unlike mechanisms maintaining memory, the consequences of PKMζ inhibition within the rACC are not permanent in neuropathic pain, possibly reflecting the re-establishment of amplification mechanisms by ongoing activity of injured nerves. In the spinal cord, however, both PKMζ-dependent and independent mechanisms contribute to amplification of evoked responses, but apparently not spontaneous pain.
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Affiliation(s)
- Tamara King
- Department of Pharmacology, University of Arizona, Tucson, AZ 85724, USA Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85724, USA Bio5 Institute, University of Arizona, Tucson, AZ 85724, USA Department of Anesthesiology, University of Arizona, Tucson, AZ 85724, USA
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71
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von Hehn CA, Baron R, Woolf CJ. Deconstructing the neuropathic pain phenotype to reveal neural mechanisms. Neuron 2012; 73:638-52. [PMID: 22365541 PMCID: PMC3319438 DOI: 10.1016/j.neuron.2012.02.008] [Citation(s) in RCA: 585] [Impact Index Per Article: 48.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/06/2012] [Indexed: 01/01/2023]
Abstract
After nerve injury maladaptive changes can occur in injured sensory neurons and along the entire nociceptive pathway within the CNS, which may lead to spontaneous pain or pain hypersensitivity. The resulting neuropathic pain syndromes present as a complex combination of negative and positive symptoms, which vary enormously from individual to individual. This variation depends on a diversity of underlying pathophysiological changes resulting from the convergence of etiological, genotypic, and environmental factors. The pain phenotype can serve therefore, as a window on underlying pathophysiological neural mechanisms and as a guide for developing personalized pain medicine.
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Affiliation(s)
- Christian A von Hehn
- FM Kirby Neurobiology Center, Children's Hospital Boston, and Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
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Melemedjian OK, Price TJ. Dendritic spine plasticity as an underlying mechanism of neuropathic pain: commentary on Tan et al. Exp Neurol 2011; 233:740-4. [PMID: 22119623 DOI: 10.1016/j.expneurol.2011.11.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Revised: 11/07/2011] [Accepted: 11/10/2011] [Indexed: 01/01/2023]
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Sandkühler J, Gruber-Schoffnegger D. Hyperalgesia by synaptic long-term potentiation (LTP): an update. Curr Opin Pharmacol 2011; 12:18-27. [PMID: 22078436 PMCID: PMC3315008 DOI: 10.1016/j.coph.2011.10.018] [Citation(s) in RCA: 125] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Accepted: 10/17/2011] [Indexed: 11/17/2022]
Abstract
Long-term potentiation of synaptic strength (LTP) in nociceptive pathways shares principle features with hyperalgesia including induction protocols, pharmacological profile, neuronal and glial cell types involved and means for prevention. LTP at synapses of nociceptive nerve fibres constitutes a contemporary cellular model for pain amplification following trauma, inflammation, nerve injury or withdrawal from opioids. It provides a novel target for pain therapy. This review summarizes recent progress which has been made in unravelling the properties and functions of LTP in the nociceptive system and in identifying means for its prevention and reversal.
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Affiliation(s)
- Jürgen Sandkühler
- Medical University of Vienna, Center for Brain Research, Department of Neurophysiology, Spitalgasse 4, A-1090 Vienna, Austria.
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