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Pollard A, Wright M, West N, Newcombe R, Davies M, West NX. Mind the gap-What is the appropriate time interval between sequential dentine stimuli to elicit a dentine hypersensitivity pain response in clinical studies? J Dent 2024; 149:105305. [PMID: 39128489 DOI: 10.1016/j.jdent.2024.105305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2024] [Revised: 08/07/2024] [Accepted: 08/08/2024] [Indexed: 08/13/2024] Open
Abstract
OBJECTIVES To determine the time interval required for a tooth diagnosed with DH to recover from a stimulus (cold air-blast/tactile) and respond with a similar elicited pain response to a repeat stimulus. METHODS A single-centre, non-randomised, clinical study in healthy adult volunteers. Eligible participants with ≥1 tooth with either a qualifying Schiff score ≥2 following cold air-blast or tactile Yeaple score of ≤20 g were allocated to tactile or air-blast group. Following primary stimulation, the designated tooth was restimulated 10, 5, 2 min and immediately after initial pain cessation. Pain was recorded with participant VAS and investigator Schiff for air-blast. RESULTS 40 participants completed the study per group. There was a significant difference in VAS scores for tactile 4 delay intervals (p < 0.001) but not air-blast stimulus, and a significant difference in mean change in VAS score from immediate to two-minute delay between stimuli (8.0 tactile vs 0.8 air-blast, p = 0.011). VAS scores in response to either stimulus showed very wide variation between participants, but changes over delay intervals within participants were relatively slight. There was a significant progressive decrease in mean Schiff score with shortening delay intervals from 10 min (2.38) to stimulation immediately after pain cessation (2.15), p = 0.018. CONCLUSIONS The findings suggest healthy teeth recover after DH stimulation more quickly following an air-blast than tactile stimulus, with around 2 min allowing recovery from both. Many factors including habituation and pain measurement subjectivity need to be considered. It would be prudent for future studies to use of ≥3 min delays. CLINICAL SIGNIFICANCE No clinical study has attempted to determine the appropriate interval between successive stimuli in DH patients. The results will impact directly on the conduct of DH trials. These findings suggest the interval could be reduced to around 2-min, but the current standard of 5-min is sufficiently long to give valid results.
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Affiliation(s)
- Alexander Pollard
- Clinical Trials Group, Periodontology, Bristol Dental School, University of Bristol, Lower Maudlin Street, Bristol BS1 2LY, United Kingdom; Torbay Hospital, Torbay and South Devon NHS Foundation Trust, Newton Road, Torquay TQ2 7AA, United Kingdom.
| | - Matthew Wright
- Clinical Trials Group, Periodontology, Bristol Dental School, University of Bristol, Lower Maudlin Street, Bristol BS1 2LY, United Kingdom
| | - Natasha West
- Clinical Trials Group, Periodontology, Bristol Dental School, University of Bristol, Lower Maudlin Street, Bristol BS1 2LY, United Kingdom
| | | | - Maria Davies
- Clinical Trials Group, Periodontology, Bristol Dental School, University of Bristol, Lower Maudlin Street, Bristol BS1 2LY, United Kingdom
| | - Nicola X West
- Clinical Trials Group, Periodontology, Bristol Dental School, University of Bristol, Lower Maudlin Street, Bristol BS1 2LY, United Kingdom
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Yu CY, Abbott PV. Pulp microenvironment and mechanisms of pain arising from the dental pulp: From an endodontic perspective. AUST ENDOD J 2018. [DOI: 10.1111/aej.12257] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Christine Y. Yu
- Discipline of Endodontics; UWA Dental School; Oral Health Centre of Western Australia; The University of Western Australia (M512); Crawley Western Australia Australia
| | - Paul V. Abbott
- Discipline of Endodontics; UWA Dental School; Oral Health Centre of Western Australia; The University of Western Australia (M512); Crawley Western Australia Australia
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Abstract
The TRPV1 receptor acts as a sensor for environmental changes in pH and temperature. Since many nociceptors express TRPV1, it is possible that local tissue-cooling may inhibit nociceptor activity via reduction of TRPV1 activation. The present study used isolated superfused rat dental pulp to test the hypothesis that capsaicin receptors are activated in inflamed tissue, as measured by alterations in neuropeptide release. We tested the hypothesis that alterations in the tissue temperature and pH of isolated superfused rat dental pulp regulate capsaicin-induced release of calcitonin gene-related peptide (CGRP). Application of capsaicin with increased proton concentration ( i.e., lowered pH) produced a nearly two-fold increase in peak immunoreactive CGRP release, as compared with capsaicin applied at a pH of 7.4. Reduction in tissue temperature from 37°C to 26°C completely blocked the capsaicin effect. The study indicates that environmental stimuli regulate the activity of capsaicin-sensitive neurons innervating dental pulp, and these factors may be significant clinically in the development and amelioration of dental pain.
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Affiliation(s)
- H E Goodis
- Division of Endodontics, Department of Preventive and Restorative Sciences, UCSF, 707 Parnasssus Ave., San Francisco, CA 94143, USA.
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Nweeia MT, Eichmiller FC, Hauschka PV, Donahue GA, Orr JR, Ferguson SH, Watt CA, Mead JG, Potter CW, Dietz R, Giuseppetti AA, Black SR, Trachtenberg AJ, Kuo WP. Sensory ability in the narwhal tooth organ system. Anat Rec (Hoboken) 2014; 297:599-617. [PMID: 24639076 DOI: 10.1002/ar.22886] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Accepted: 01/15/2014] [Indexed: 01/20/2023]
Abstract
The erupted tusk of the narwhal exhibits sensory ability. The hypothesized sensory pathway begins with ocean water entering through cementum channels to a network of patent dentinal tubules extending from the dentinocementum junction to the inner pulpal wall. Circumpulpal sensory structures then signal pulpal nerves terminating near the base of the tusk. The maxillary division of the fifth cranial nerve then transmits this sensory information to the brain. This sensory pathway was first described in published results of patent dentinal tubules, and evidence from dissection of tusk nerve connection via the maxillary division of the fifth cranial nerve to the brain. New evidence presented here indicates that the patent dentinal tubules communicate with open channels through a porous cementum from the ocean environment. The ability of pulpal tissue to react to external stimuli is supported by immunohistochemical detection of neuronal markers in the pulp and gene expression of pulpal sensory nerve tissue. Final confirmation of sensory ability is demonstrated by significant changes in heart rate when alternating solutions of high-salt and fresh water are exposed to the external tusk surface. Additional supporting information for function includes new observations of dentinal tubule networks evident in unerupted tusks, female erupted tusks, and vestigial teeth. New findings of sexual foraging divergence documented by stable isotope and fatty acid results add to the discussion of the functional significance of the narwhal tusk. The combined evidence suggests multiple tusk functions may have driven the tooth organ system's evolutionary development and persistence.
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Affiliation(s)
- Martin T Nweeia
- Department of Restorative Dentistry and Biomaterial Sciences, Harvard School of Dental Medicine, 188 Longwood Ave., Boston, MA, 02115; Department of Vertebrate Zoology, Smithsonian Institution, 1000 Jefferson Drive SW, Washington, DC, 20004; Department of Organismic and Evolutionary Biology, Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138
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Facilitatory effect of AC-iontophoresis of lidocaine hydrochloride on the permeability of human enamel and dentine in extracted teeth. Arch Oral Biol 2012; 58:341-7. [PMID: 22939373 DOI: 10.1016/j.archoralbio.2012.08.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 07/30/2012] [Accepted: 08/04/2012] [Indexed: 11/22/2022]
Abstract
OBJECTIVES The objectives of the present study were to quantitatively evaluate chemical permeability through human enamel/dentine using conductometry and to clarify if alternating current (AC) iontophoresis facilitates such permeability. MATERIALS AND METHODS Electrical impedance of different concentrations of lidocaine hydrochloride was measured using a bipolar platinum impedance probe. A quadratic curve closely fitted to the response functions between conductance and lidocaine hydrochloride. For analysis of the passage of lidocaine hydrochloride through human enamel/dentine, eight premolars that were extracted for orthodontic treatment were sectioned at the cemento-enamel junction. The tooth crowns were held between two chambers with a double O-ring. The enamel-side chamber was filled with lidocaine hydrochloride, and the pulp-side chamber was filled with extrapure water. Two platinum plate electrodes were set at the end of each chamber to pass alternating current. A simulated interstitial pulp pressure was applied to the pulp-side chamber. The change in the concentration of lidocaine hydrochloride in the pulp-side chamber was measured every 2min using a platinum recording probe positioned at the centre of the pulp-side chamber. Passive entry without iontophoresis was used as a control. RESULTS The level of lidocaine hydrochloride that passed through enamel/dentine against the dentinal fluid flow increased with time. Electrical conductance (G, mho) correlated closely to the concentration (x, mmol/L) of lidocaine hydrochloride (G=2.16x(2)+0.0289x+0.000376, r(2)=0.999). CONCLUSIONS Lidocaine hydrochloride can pass through enamel/dentine. Conductometry showed that the level of lidocaine hydrochloride that passed through enamel/dentine was increased by AC iontophoresis.
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ZHU YJ, XU F, SU JH, ZHOU H, LU TJ. MATHEMATICAL MODELING FOR THE PREDICTION AND IMPROVEMENT OF TOOTH THERMAL PAIN: A REVIEW. J MECH MED BIOL 2012. [DOI: 10.1142/s0219519411004095] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Tooth pain, especially tooth thermal pain, is one of the most important symptoms and signs in dental clinic and daily life. As a special sensation, pain has been studied extensively in both clinic and experimental research aimed at reducing or eliminating the possible negative effects of pain. Unfortunately, the full underlying mechanism of pain is still unclear, because the pain could be influenced by many factors, including physiological, psychological, physical, chemical, and biological factors and so on. Besides, most studies on pain mechanisms in the literature are based on skin pain sensation and only few are based on tooth pain. In this paper, we present a comprehensive review on both neurophysiology of tooth pain mechanism, and corresponding thermal, mechanical, and thermomechanical behaviors of teeth. We also describe a multiscale modeling approach for quantifying tooth thermal pain by integrating the mathematic methods of engineering into the neuroscience. The mathematical model of tooth thermal pain will enable better understanding of thermal pain mechanism and optimization of existing diagnosis and treatment in dental clinic.
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Affiliation(s)
- Y. J. ZHU
- Stomatological Hospital, College of Medicine, Biomedical Engineering and Biomechanics Center, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - F. XU
- Biomedical Engineering and Biomechanics Center, Xi'an Jiaotong University, Xi'an 710049, P. R. China
- School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - J. H. SU
- Biomedical Engineering and Biomechanics Center, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - H. ZHOU
- Stomatological Hospital, College of Medicine, Xi'an Jiaotong University, Xi'an 710004, P. R. China
| | - T. J. LU
- Biomedical Engineering and Biomechanics Center, Xi'an Jiaotong University, Xi'an 710049, P. R. China
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Fujii K, Motohashi K, Umino M. Heterotopic ischemic pain attenuates somatosensory evoked potentials induced by electrical tooth stimulation: Diffuse noxious inhibitory controls in the trigeminal nerve territory. Eur J Pain 2012; 10:495-504. [PMID: 16188472 DOI: 10.1016/j.ejpain.2005.07.002] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2005] [Revised: 05/27/2005] [Accepted: 07/11/2005] [Indexed: 11/30/2022]
Abstract
The purpose of this study was to determine whether the late component of somatosensory evoked potentials (SEP) induced by electrical tooth stimulation and pain intensity are inhibited by heterotopic ischemic stimulation. The tourniquet pressure with 50 mmHg greater than the individual's systolic pressure was applied to the left upper arm for 10 min as ischemic conditioning stimulation. The late component of SEP and visual analogue scale (VAS) were recorded at 4 times and both were significantly decreased when ischemic conditioning stimulation was applied. The maximum reductions in SEP amplitude and the VAS value were 26.1% and 21.2%, respectively, during ischemic conditioning stimulation. After-effect was observed 5 min after removal of the conditioning stimulation. The present study revealed that heterotopic ischemic stimulation attenuated the late component of SEP induced by electrical tooth stimulation, triggering diffuse noxious inhibitory controls (DNIC) and after-effects in the trigeminal nerve territory. It was also suggested that the DNIC effect differs, depending on the intensity, kind, and quality of the test and conditioning stimuli.
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Affiliation(s)
- Keiko Fujii
- Anesthesiology and Clinical Physiology, Department of Oral Restitution, Division of Oral Health Sciences, Graduate School, Tokyo Medical and Dental University, Yushima, Bunkyo-ku, Japan.
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Gibbs JL, Melnyk JL, Basbaum AI. Differential TRPV1 and TRPV2 channel expression in dental pulp. J Dent Res 2011; 90:765-70. [PMID: 21406609 DOI: 10.1177/0022034511402206] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Hypersensitivity to thermal and mechanical stimuli can occur in painful pulpitis. To explore the neuro-anatomical basis of heat and mechanical sensitivity, we evaluated expression of TRPV1 (heat) and TRPV2 (heat/mechanical) channels in the cell bodies and terminal arborizations of neurons that innervate the dental pulp (DP) and periodontal tissues (PDL). We report that ~50% of trigeminal ganglion (TG) neurons retrogradely labeled from the DP express TRPV2, and this was significantly greater than the general expression of this channel in the TG (15%) and slightly more than what is expressed in the PDL by retrograde labeling (40%). The TRPV1 receptor, however, was less prevalent in neurons innervating the DP than their general expression in the TG (17% vs. 26%) and was more extensively expressed in neurons innervating the PDL (26%). Co-labeling studies showed that 70% of neurons that innervate the DP are myelinated. Approximately 1/3 of the retrogradely labeled neurons from the DP were calcitonin-gene-related-peptide-positive (peptide-expressing), but very few expressed the IB4 marker of non-peptidergic unmyelinated afferents. These findings suggest that the DP has a unique neurochemical innervation with regard to TRP receptor expression, which has significant implications for the mechanisms contributing to odontogenic pain and management strategies.
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Affiliation(s)
- J L Gibbs
- Department of Preventive and Restorative Dental Sciences, University of California San Francisco, CA 94158, USA.
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Fujii-Abe K, Oono Y, Motohashi K, Fukayama H, Umino M. Heterotopic CO2Laser Stimulation Inhibits Tooth-Related Somatosensory Evoked Potentials. PAIN MEDICINE 2010; 11:825-33. [DOI: 10.1111/j.1526-4637.2010.00855.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Aggarwal V, Singla M, Kabi D. Comparative evaluation of anesthetic efficacy of Gow-Gates mandibular conduction anesthesia, Vazirani-Akinosi technique, buccal-plus-lingual infiltrations, and conventional inferior alveolar nerve anesthesia in patients with irreversible pulpitis. ACTA ACUST UNITED AC 2010; 109:303-8. [PMID: 20123413 DOI: 10.1016/j.tripleo.2009.09.016] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2009] [Revised: 08/31/2009] [Accepted: 09/10/2009] [Indexed: 11/24/2022]
Abstract
OBJECTIVE Conventional inferior alveolar nerve block (IANB) has a poor success rate in inflamed pulps. Three alternative techniques of providing anesthesia to mandibular molars were evaluated and compared with conventional IANB. STUDY DESIGN Ninety-seven adult volunteer subjects, actively experiencing pain, participated in this prospective, randomized, double-blinded study. Twenty-five patients received Gow-Gates mandibular conduction block anesthesia, 24 patients received "high" Vazirani-Akinosi inferior alveolar nerve block, 26 received only buccal-plus-lingual infiltrations, and 22 patients (control) received conventional IANB anesthesia. Endodontic access preparation was initiated after 15 minutes of anesthesia. Pain during treatment was recorded using a Heft-Parker visual analog scale. Success was recorded for "none" or "mild" pain. RESULTS Statistical analysis using nonparametric McNemer tests showed that Gow-Gates gave a success rate of 52%, which was statistically higher than control IANB (36%) (P < .05). Vazirani-Akinosi and infiltrations gave 41% and 27% success rates, respectively, with no statistically significant differences from control IANB. CONCLUSIONS Gow-Gates mandibular conduction anesthesia may increase the success rates in patients with irreversible pulpitis compared with conventional IANB. None of the techniques provided acceptable success rates.
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Affiliation(s)
- Vivek Aggarwal
- Department of Dental Surgery, Safdarjung Hospital, New Delhi, India.
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Sensory purinergic receptor P2X3 is elevated in burning mouth syndrome. Int J Oral Maxillofac Surg 2010; 39:815-9. [PMID: 20418063 DOI: 10.1016/j.ijom.2010.03.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2009] [Revised: 12/23/2009] [Accepted: 03/16/2010] [Indexed: 10/19/2022]
Abstract
Recent studies show that P2X(3) may play a role in neuropathic pain, including orofacial pain. Burning mouth syndrome (BMS) is a chronic neuropathic pain condition affecting 0.6-12% of post-menopausal women in the Western world. This study evaluates, for the first time, P2X(3) immunoreactivity levels in lingual mucosa in BMS patients. Patients diagnosed with BMS (n=9) in accordance with International Association for the Study of Pain criteria and patients attending for wisdom tooth removal (n=10, controls), were involved in this study. A pain history and score was recorded on a visual analogue scale (VAS) prior to obtaining a lingual biopsy. Immunohistochemistry and image analysis were used to quantify submucosal nerve fibres expressing P2X(3) and the structural marker neurofilaments. P2X(3) positive fibres were significantly increased in BMS compared with controls (p=0.024). In contrast, neurofilament-staining fibres were reduced in BMS, and when expressed as a ratio of the neurofilament percentage area, there was a trend for an increase of P2X(3) positive fibres in the BMS group. Increased P2X(3) immunoreactivity in the trigeminal sensory system may play a role in the symptoms observed in BMS. P2X(3) may therefore be a therapeutic target for treating BMS and trigeminal neuropathic pain.
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Aggarwal V, Jain A, Kabi D. Anesthetic Efficacy of Supplemental Buccal and Lingual Infiltrations of Articaine and Lidocaine after an Inferior Alveolar Nerve Block in Patients with Irreversible Pulpitis. J Endod 2009; 35:925-9. [DOI: 10.1016/j.joen.2009.04.012] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2009] [Revised: 03/31/2009] [Accepted: 04/08/2009] [Indexed: 10/20/2022]
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Lam DK, Sessle BJ, Hu JW. Glutamate and capsaicin effects on trigeminal nociception I: Activation and peripheral sensitization of deep craniofacial nociceptive afferents. Brain Res 2008; 1251:130-9. [PMID: 19056361 DOI: 10.1016/j.brainres.2008.11.029] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2008] [Revised: 10/08/2008] [Accepted: 11/10/2008] [Indexed: 12/24/2022]
Abstract
We have examined the effect of the peripheral application of glutamate and capsaicin to deep craniofacial tissues in influencing the activation and peripheral sensitization of deep craniofacial nociceptive afferents. The activity of single trigeminal nociceptive afferents with receptive fields in deep craniofacial tissues were recorded extracellularly in 55 halothane-anesthetized rats. The mechanical activation threshold (MAT) of each afferent was assessed before and after injection of 0.5 M glutamate (or vehicle) and 1% capsaicin (or vehicle) into the receptive field. A total of 68 afferents that could be activated by blunt noxious mechanical stimulation of the deep craniofacial tissues (23 masseter, 5 temporalis, 40 temporomandibular joint) were studied. When injected alone, glutamate and capsaicin activated and induced peripheral sensitization reflected as MAT reduction in many afferents. Following glutamate injection, capsaicin-evoked activity was greater than that evoked by capsaicin alone, whereas following capsaicin injection, glutamate-evoked responses were similar to glutamate alone. These findings indicate that peripheral application of glutamate or capsaicin may activate or induce peripheral sensitization in a subpopulation of trigeminal nociceptive afferents innervating deep craniofacial tissues, as reflected in changes in MAT and other afferent response properties. The data further suggest that peripheral glutamate and capsaicin receptor mechanisms may interact to modulate the activation and peripheral sensitization in some deep craniofacial nociceptive afferents.
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Affiliation(s)
- David K Lam
- Faculty of Dentistry, University of Toronto 124 Edward Street, Toronto, Ontario, Canada M5G 1G6
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Takahama K, Shirasaki T, Zhou JR. [Lower airway nervous system as a putative target of antitussive drugs effective for treatment of chronic cough]. Nihon Yakurigaku Zasshi 2008; 131:423-8. [PMID: 18552443 DOI: 10.1254/fpj.131.423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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MARKOWITZ K, PASHLEY DH. Discovering new treatments for sensitive teeth: the long path from biology to therapy. J Oral Rehabil 2008; 35:300-15. [DOI: 10.1111/j.1365-2842.2007.01798.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Gardner N, Newton JP, Mason AG, Cadden SW. Differences between inhibitory jaw reflexes evoked by stimulation of tooth pulp and across the adjacent alveolar process in man. Arch Oral Biol 2008; 53:575-82. [PMID: 18191101 DOI: 10.1016/j.archoralbio.2007.11.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2007] [Revised: 11/28/2007] [Accepted: 11/29/2007] [Indexed: 11/16/2022]
Abstract
OBJECTIVE In humans, stimulation of nerves in or around teeth can evoke inhibitory jaw reflexes. Previous studies had suggested that there may be subtle differences in the timings of the responses. The aim of the present study was to investigate this by comparing reflexes evoked by electrical stimulation of a tooth and of the adjacent tissues in individual subjects. DESIGN Experiments were performed on 9 volunteers (3 male, 6 female). EMG recordings were made from the masseter muscle ipsilateral to the stimuli, whilst the subjects maintained a steady level of activity in the muscle. Reflexes were evoked by applying stimuli to an incisor tooth (pulpal stimuli) or across the adjacent alveolar process (transalveolar stimuli), using bipolar electrodes. RESULTS Two inhibitory responses were evoked in most (8/9) subjects. The first occurred at a shorter latency after transalveolar than after pulpal stimulation (12.3+/-0.5 ms vs 19.4+/-1.5 ms; P=0.0014, paired t-test). For technical reasons, it was not possible to make such comparisons for the second inhibitory responses in all the subjects. In 5 subjects where such a comparison was possible, the mean latency of the transalveolar-evoked response was again shorter than that of the pulpal-evoked response (56.4+/-2.8 ms and 58.8+/-5.3 ms, respectively), but this difference was not significant (P=0.5). CONCLUSIONS It appears that inhibitory jaw reflexes evoked from around the teeth are faster than those from the dental pulp. This observation could be due to differences between the peripheral afferent and/or the central pathways mediating the reflexes.
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Affiliation(s)
- Nadia Gardner
- Oral Neurophysiology Research Group, The Dental School, University of Dundee, Dundee DD1 4HN, Scotland, United Kingdom
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Guénette SA, Ross A, Marier JF, Beaudry F, Vachon P. Pharmacokinetics of eugenol and its effects on thermal hypersensitivity in rats. Eur J Pharmacol 2007; 562:60-7. [PMID: 17321520 DOI: 10.1016/j.ejphar.2007.01.044] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2006] [Revised: 01/10/2007] [Accepted: 01/11/2007] [Indexed: 12/01/2022]
Abstract
Neuropathic pain is a type of chronic pain following central or peripheral nervous system lesions that cause allodynia (pain initiated by a non-painful stimulus) and hyperalgesia (increased pain sensation following a painful stimulus). The first objective of the study was to evaluate the pharmacokinetics of eugenol, the principle chemical constituent of clove oil, following a gavage administration (40 mg/kg) in male Sprague-Dawley rats. The second objective was to evaluate the effect of repeated oral administrations of eugenol on hyperalgesia and allodynia using an experimental model of neuropathic pain in rats. Thermal and mechanical sensitivity (Hargreave's test and von Frey filaments) were determined in sciatic nerve cuff-implanted rats. Sensitivities were assessed following repeated oral administrations of 40 mg/kg of eugenol or saline for 5 days (n=6 per group). Pharmacokinetic parameters were calculated using noncompartmental methods. Serial blood samples were collected over 24 h. Concentrations of eugenol in blood and plasma peaked rapidly following oral administration. Mean T(1/2) values of eugenol in plasma and blood were long (14.0 and 18.3 h, respectively), suggesting a potential accumulation of the drug following repeated administrations. Reaction time to thermal stimuli appeared to increase constantly following repeated administrations of eugenol. On the last day of treatment, eugenol treatments resulted in a statistically significant prolongation of the reaction time to thermal stimuli in rats compared to the saline group (Mean+/-S.E.M.: 11.4+/-1.23 vs. 6.1+/-0.53 s, P<0.01). These results support the hypothesis that eugenol may alleviate neuropathic pain and that the cumulative effect of the drug may be in part responsible for this effect following repeated daily administrations.
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Affiliation(s)
- Sarah Annie Guénette
- Université de Montréal, Faculté de Médecine Vétérinaire, Département de Biomédecine Vétérinaire et de Pathologie and Microbiologie, Saint-Hyacinthe, QC, Canada
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Padilla F, Couble ML, Coste B, Maingret F, Clerc N, Crest M, Ritter AM, Magloire H, Delmas P. Expression and localization of the Nav1.9 sodium channel in enteric neurons and in trigeminal sensory endings: implication for intestinal reflex function and orofacial pain. Mol Cell Neurosci 2007; 35:138-52. [PMID: 17363266 DOI: 10.1016/j.mcn.2007.02.008] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2006] [Revised: 02/07/2007] [Accepted: 02/09/2007] [Indexed: 11/21/2022] Open
Abstract
The Nav1.9 sodium channel is expressed in nociceptive DRG neurons where it contributes to spontaneous pain behavior after peripheral inflammation. Here, we used a newly developed antibody to investigate the distribution of Nav1.9 in rat and mouse trigeminal ganglion (TG) nerve endings and in enteric nervous system (ENS). In TGs, Nav1.9 was expressed in the soma of small- and medium-sized, peripherin-positive neurons. Nav1.9 was present along trigeminal afferent fibers and at terminals in lip skin and dental pulp. In the ENS, Nav1.9 was detected within the soma and proximal axons of sensory, Dogiel type II, myenteric and submucosal neurons. Immunological data were correlated with the detection of persistent TTX-resistant Na(+) currents sharing similar properties in DRG, TG and myenteric neurons. Collectively, our data support a potential role of Nav1.9 in the transmission of trigeminal pain and the regulation of intestinal reflexes. Nav1.9 might therefore constitute a molecular target for therapeutic treatments of orofacial pain and gastrointestinal syndromes.
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Affiliation(s)
- Françoise Padilla
- Laboratoire de Neurophysiologie Cellulaire, CNRS, UMR 6150, Faculté de Médecine, IFR Jean Roche, Bd. Pierre Dramard, 13916 Marseille Cedex 20, France
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Biggs JE, Yates JM, Loescher AR, Clayton NM, Boissonade FM, Robinson PP. Vanilloid receptor 1 (TRPV1) expression in lingual nerve neuromas from patients with or without symptoms of burning pain. Brain Res 2006; 1127:59-65. [PMID: 17109831 DOI: 10.1016/j.brainres.2006.10.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2006] [Revised: 10/02/2006] [Accepted: 10/02/2006] [Indexed: 11/17/2022]
Abstract
The lingual nerve, a peripheral branch of the trigeminal nerve, can be damaged during the surgical removal of lower third molar teeth. This damage can lead to the development of dysaesthesia, with some patients complaining of burning pain. We investigated the hypothesis that vanilloid receptor 1 (TRPV1), a transducer of noxious heat stimuli, was involved in the development of this burning pain. Neuroma specimens were obtained from patients undergoing microsurgical repair of a damaged lingual nerve. Repair was undertaken where there was little evidence of spontaneous recovery, 7-41 months after the initial injury. Preoperatively the incidence of dysaesthesia was determined by reported symptoms and using visual analogue scales (VAS) for pain, tingling and discomfort. Nine neuromas were studied from patients with burning dysaesthesia and six from patients with a sensory deficit but no dysaesthesia. Indirect immunofluorescence for protein gene product (PGP) 9.5 and TRPV1 was used to quantify the percentage area of PGP 9.5 positive neuronal tissue that also expressed TRPV1. The results showed no significant difference between the mean percentage area of TRPV1 expression in neuromas from patients with or without burning dysaesthesia. Furthermore, there was no correlation between TRPV1 expression and the VAS scores for pain, tingling or discomfort. However, if data from all patients was pooled, there was a negative correlation between the level of TRPV1 expression and the time after initial injury. These data do not rule out involvement of TRPV1 in the aetiology of burning dysaesthesia following lingual nerve injury but suggest that TRPV1 at the injury site does not play a primary role.
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Affiliation(s)
- James E Biggs
- Department of Oral and Maxillofacial Surgery, School of Clinical Dentistry, University of Sheffield, Claremont Crescent, Sheffield, S10 2TA, UK.
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20
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Bombardi C, Chiocchetti R, Brunetti O, Grandis A, Lucchi ML, Bortolami R. Central distribution of nociceptive intradental afferent nerve fibers in the rat. Tissue Cell 2006; 38:251-5. [PMID: 16824568 DOI: 10.1016/j.tice.2006.05.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2005] [Revised: 05/05/2006] [Accepted: 05/09/2006] [Indexed: 12/01/2022]
Abstract
The central distribution of intradental afferent nerve fibers was investigated by combining electron microscopic observations with a selective method for inducing degeneration of the A delta- and C-type afferent fibers. Degenerating terminals were found on the proprioceptive mesencephalic trigeminal neurons and on dendrites in the neuropil of the trigeminal motor nucleus after application of capsaicin to the rat's lower incisor tooth pulp. The results give anatomical evidence of new sites of central projection of intradental A delta- and C-type fibers whereby the nociceptive information from the tooth pulp can affect jaw muscle activity.
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Affiliation(s)
- C Bombardi
- Dipartimento di Morfofisiologia Veterinaria e Produzioni Animali, Università degli Studi di Bologna, Via Tolara di Sopra 50, 40064 Ozzano dell'Emilia, Bologna, Italy
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21
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Biggs JE, Yates JM, Loescher AR, Clayton NM, Boissonade FM, Robinson PP. Changes in vanilloid receptor 1 (TRPV1) expression following lingual nerve injury. Eur J Pain 2006; 11:192-201. [PMID: 16542859 DOI: 10.1016/j.ejpain.2006.02.004] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2005] [Revised: 01/25/2006] [Accepted: 02/05/2006] [Indexed: 11/26/2022]
Abstract
We have investigated a possible role for vanilloid receptor 1 (TRPV1), a transducer of noxious stimuli, in the development of neuropathic pain following injury to a peripheral branch of the trigeminal nerve. In nine adult ferrets the left lingual nerve was sectioned and recovery permitted for 3 days, 3 weeks or 3 months (3 ferrets per group). A retrograde tracer, fluorogold, was injected into the damaged nerve to identify associated cell bodies in the trigeminal ganglion. Three further ferrets, receiving only tracer injection, served as uninjured controls. Indirect immunofluorescence for TRPV1 and image analysis was used to quantify the percentage area of staining (PAS) of TRPV1 in the left and right lingual nerves. Additionally, the proportion of fluorogold positive and fluorogold negative cells expressing TRPV1 in the ganglion was determined. TRPV1 expression increased significantly at the injury site of damaged nerves 3 days after injury and this was matched by a reduction in the proportion of fluorogold positive cells expressing TRPV1 in the ganglion. At 3 weeks TRPV1 expression at the injury site was still high, while in the ganglion was significantly greater than in the controls. In the 3-month recovery group TRPV1 expression in both nerve fibres and ganglion cells, was not significantly different from controls and there were no changes in expression in the fluorogold negative cells in the ganglion at any time point studied. These data suggest that after injury there is an increase in the axonal transport of TRPV1 from the cell bodies to the damaged axons and this is followed by an increase in synthesis in the ganglion. These changes in expression may be involved in development of sensory disturbances or dysaesthesia after injury.
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Affiliation(s)
- James E Biggs
- Department of Oral and Maxillofacial Surgery, School of Clinical Dentistry, University of Sheffield, Claremont Crescent, Sheffield, South Yorkshire S10 2TA, UK.
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Caviedes-Bucheli J, Azuero-Holguin MM, Munoz HR. The effect of capsaicin on substance P expression in pulp tissue inflammation. Int Endod J 2005; 38:30-3. [PMID: 15606820 DOI: 10.1111/j.1365-2591.2004.00893.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIM To evaluate the effect of capsaicin on substance P (SP) expression during induced inflammation in rat pulp tissue. METHODOLOGY Radioimmunoanalysis was used to measure SP levels in 36 mandibular molar pulps taken from six Wistar rats. Twelve samples were obtained from healthy pulps and used as negative control group. Another 12 samples were obtained after inducing inflammation with mechanical pulp exposure; these were used as the positive control group. Capsaicin was infiltrated into the inferior dental nerve in the experimental group and 12 samples were obtained after mechanical pulp exposure. RESULTS The lowest SP expression was found in mechanically exposed pulps where capsaicin pretreatment had been carried out (0.028 ng mL(-1)), followed by healthy pulps (0.302 ng mL(-1)). The highest SP expression was found in mechanically exposed pulps with no capsaicin pretreatment (124 ng mL(-1)). The Kruskal-Wallis test showed statistically significant differences between the groups (P < 0.001). CONCLUSION Inferior dental nerve infiltration with capsaicin reduces SP expression in dental pulp tissue in rats.
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Affiliation(s)
- J Caviedes-Bucheli
- Graduate Studies Department, School of Dentistry, Pontificia Universidad Javeriana, 26 Bogota, Colombia.
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Rifai K, Chidiac JJ, Hawwa N, Baliki M, Jabbur SJ, Saadé NE. Occlusion of dentinal tubules and selective block of pulp innervation prevent the nociceptive behaviour induced in rats by intradental application of irritants. Arch Oral Biol 2004; 49:457-68. [PMID: 15099803 DOI: 10.1016/j.archoralbio.2004.01.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/12/2004] [Indexed: 11/29/2022]
Abstract
OBJECTIVES Application of irritants on the exposed dentine of the incisors has been shown to produce aversive behaviour in awake rats. This study aims to demonstrate that the observed aversion is due to the infiltration of irritants through the dentinal tubules and the activation of capsaicin sensitive fibres in the tooth pulp. METHODS Different groups of rats were subjected, under anaesthesia, to cutting of the distal 2 mm of their lower incisors and the fixation of an artificial crown that allows the application of 10-15 microl of solution. Several procedures were followed to prevent the action of the irritants including occlusion of the dentinal tubules, local application of lidocaine, selective ablation of the capsaicin sensitive primary afferents (CSPA) or incisor pulpectomy; the reactions to intradental application of either capsaicin (1%) or formalin (2.5%) were tested using a newly designed behavioural score. RESULTS Occlusion of dentinal tubules produced significant attenuation of the nociceptive behaviour induced by dentinal application of either capsaicin or formalin. Similar results were observed following either local block with lidocaine (2%), selective ablation of capsaicin sensitive afferents or total denervation by pulpectomy. CONCLUSIONS The present results confirm the hypothesis of infiltration of irritants to the incisor pulp through the dentinal tubules and suggest that the reported inflammatory reaction and hyperalgesia are mediated, to a large extent, by capsaicin sensitive primary afferents.
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Affiliation(s)
- Khaldoun Rifai
- Department of Prosthodontics, School of Dentistry, Lebanese University, Beirut, Lebanon
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24
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Westenbroek RE, Anderson NL, Byers MR. Altered localization of Cav1.2 (L-type) calcium channels in nerve fibers, Schwann cells, odontoblasts, and fibroblasts of tooth pulp after tooth injury. J Neurosci Res 2004; 75:371-83. [PMID: 14743450 DOI: 10.1002/jnr.10863] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We have determined the localization of Cav1.2 (L-Type) Ca2+ channels in the cells and nerve fibers in molars of normal or injured rats. We observed high levels of immunostaining of L-type Ca2+ channels in odontoblast cell bodies and their processes, in fibroblast cell bodies and in Schwann cells. Many Cav1.2-containing unmyelinated and myelinated axons were also present in root nerves and proximal branches in coronal pulp, but were usually missing from nerve fibers in dentin. Labeling in the larger fibers was present along the axonal membrane, localized in axonal vesicles, and in nodal regions. After focal tooth injury, there is a marked loss of Cav1.2 channels in injured teeth. Immunostaining of Cav1.2 channels was lost selectively in nerve fibers and local cells of the tooth pulp within 10 min of the lesion, without loss of other Cav channel or pulpal labels. By 60 min, Cav1.2 channels in odontoblasts were detected again but at levels below controls, whereas fibroblasts were labeled well above control levels, similar to upregulation of Cav1.2 channels in astrocytes after injury. By 3 days after the injury, Cav1.2 channels were again detected in nerve fibers and immunostaining of fibroblasts and odontoblasts had returned to control levels. These findings provide new insight into the localization of Cav1.2 channels in dental pulp and sensory fibers, and demonstrate unexpected plasticity of channel distribution in response to nerve injury.
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Affiliation(s)
- R E Westenbroek
- Department of Pharmacology, University of Washington, Seattle, USA.
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25
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Ikeda H, Suda H. Sensory experiences in relation to pulpal nerve activation of human teeth in different age groups. Arch Oral Biol 2003; 48:835-41. [PMID: 14596873 DOI: 10.1016/s0003-9969(03)00176-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
There are no data on the correlation of intradental nerve activity and sensation from intact human teeth. We used microneurography to examine this relation and to determine whether it changes with age. Fifteen informed and healthy male volunteers were divided into three age groups: group A (18.6+/-1.82 years, mean+/-standard deviation (S.D.)), group B (38.4+/-2.70 years) and group C (64.0+/-4.06 years). Ratings of perceived pain intensity to thermal stimulation were obtained using a visual analogue scale (VAS). In addition, each subject chose one or two words from the short-form McGill Pain Questionnaire to describe perceived pain. A total of 90 single pulpal axons were studied with microneurography at the same time as the sensory experiences were recorded. Mean conduction velocities and variance estimates correlated closely with age. With advancing age, first, the percentage of teeth from which the subjects did not perceive any sensations to thermal stimulation increased, second, units responding to heat stimulus decreased, and third, latencies of sensation induced by thermal stimulation increased. In addition, a burst of afterdischarges following thermal stimulation and neural discharges evoked by thermal stimulation produced no sensation only in some of group B and C units. In contrast, no significant difference was found among three groups in VAS scores and words to describe the perceived pain to thermal stimulation. These results suggest that pulpal afferents were activated by the same mechanism(s); the hydrodynamic mechanism works immediately after thermal stimulation and is possibly followed by direct activation of some nerves, especially slow conducting fibres. In older tooth pulps, the decrease in the number of fast conducting afferents and mineral apposition of dentinal tubules impaired the nerve activation, especially by heat, as per the hydrodynamic mechanism. Spike discharges without sensation in older individuals were suggested to be due to insufficient spatial and temporal summation and may be involved with abnormal uncomfortable sensations.
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Affiliation(s)
- Hideharu Ikeda
- Pulp Biology and Endodontics, Department of Restorative Sciences, Graduate School, Tokyo Medical and Dental University, 5-45 Yushima 1-chome, Bunkyo-ku, 113-8549, Tokyo, Japan.
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Baccei ML, Bardoni R, Fitzgerald M. Development of nociceptive synaptic inputs to the neonatal rat dorsal horn: glutamate release by capsaicin and menthol. J Physiol 2003; 549:231-42. [PMID: 12679376 PMCID: PMC2342935 DOI: 10.1113/jphysiol.2003.040451] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
To study the postnatal development of nociceptive synaptic inputs in the superficial dorsal horn of the neonatal rat spinal cord, we examined the effect of capsaicin and menthol on glutamatergic mEPSCs in postnatal day (P) 0-1, P5-6 and P9-11 slices of spinal cord. Capsaicin (100 nM to 2 microM) increased the mEPSC frequency in a concentration-dependent manner at all ages tested, with a significant enhancement of the effect between P5 and P10. This effect was sensitive to vanilloid receptor (VR) antagonists. The elevation in mEPSC frequency occurred at concentrations of capsaicin (100 nM) that did not alter the distribution of mEPSC amplitudes and was abolished by a dorsal rhizotomy, demonstrating that capsaicin acts via presynaptic VR1 receptors localized on primary afferents. Menthol significantly increased the mEPSC frequency with a similar developmental pattern to capsaicin without consistently affecting mEPSC amplitude. The increase in mEPSC frequency following capsaicin did not depend on transmembrane calcium influx since it persisted in zero [Ca2+]o. The facilitation of spontaneous glutamate release by capsaicin was sufficient to evoke action potentials in neonatal dorsal horn neurons but was accompanied by a block of EPSCs evoked by electrical stimulation of the dorsal root. These results indicate that VR1-expressing nociceptive primary afferents form functional synaptic connections in the superficial dorsal horn from birth and that activation of the VR1 receptor increases spontaneous glutamate release via an undetermined mechanism. In addition, the data suggest that immature primary afferents express functional menthol receptors that are capable of modulating transmitter release. These results have important functional implications for infant pain processing.
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Affiliation(s)
- Mark L Baccei
- Department of Anatomy and Developmental Biology, University College London, UK.
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Byers MR, Suzuki H, Maeda T. Dental neuroplasticity, neuro-pulpal interactions, and nerve regeneration. Microsc Res Tech 2003; 60:503-15. [PMID: 12619126 DOI: 10.1002/jemt.10291] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
This review covers current information about the ability of dental nerves to regenerate and the role of tooth pulp in recruitment of regenerating nerve fibers. In addition, the participation of dental nerves in pulpal injury responses and healing is discussed, especially concerning pulp regeneration and reinnervation after tooth replantation. The complex innervation of teeth is highly asymmetric and guided towards specific microenvironments along blood vessels or in the crown pulp and dentin. Pulpal products such as nerve growth factor are distributed in the same asymmetric gradients as the dentinal sensory innervation, suggesting regulation and recruitment of those nerve fibers by those specific factors. The nerve fibers have important effects on pulpal blood flow and inflammation, while their sprouting and cytochemical changes after tooth injury are in response to altered pulpal cytochemistry. Thus, their pattern and neuropeptide intensity are indicators of pulp status, while their local actions continually affect that status. When denervated teeth are injured, either by pulp exposure on the occlusal surface or by replantation, they have more pulpal necrosis than occurs for innervated teeth. However, small pulp exposures on the side of denervated crowns or larger lesions in germ-free animals can heal well, showing the value of postoperative protection from occlusal trauma or from infection. Current ideas about dental neuroplasticity, neuro-pulpal interactions, and nerve regeneration are related to the overall topics of tooth biomimetics and pulp/dentin regeneration.
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Affiliation(s)
- Margaret R Byers
- Department of Anesthesiology, University of Washington, Seattle 98195-6540, USA.
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Levy D, Strassman AM. Mechanical response properties of A and C primary afferent neurons innervating the rat intracranial dura. J Neurophysiol 2002; 88:3021-31. [PMID: 12466427 DOI: 10.1152/jn.00029.2002] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The intracranial dura receives a small-fiber sensory innervation from the trigeminal ganglion that is thought to be involved in some types of headaches, including migraine. Mechanical response properties of dural afferent neurons were examined to investigate variation across the population in the properties of threshold, slope, adaptation, and incidence of mechanosensitivity. Dural afferent neurons were recorded in the trigeminal ganglion of urethan-anesthetized rats and were identified by their constant-latency response to dural shock. Neurons were classified as fast A (>5 m/s), slow A (5 >or= conduction velocity (CV) >or= 1.5 m/s), or C (<1.5 m/s), based on response latency to dural shock. Mechanical receptive fields were identified by stroking or indenting the outer surface of the dura. Stimulus-response curves were obtained from responses to 2-s constant-force indenting stimuli of graded intensities delivered to the dural receptive field with a servo force-controlled mechanical stimulator. The slow A population had the highest percentage of mechanosensitive units (97%) as well as the highest slopes and the lowest thresholds. Thus by all three criteria, the slow As had the highest mechanosensitivity. Conversely, the fast A population had the lowest mechanosensitivity in that it had the lowest percentage of mechanosensitive units (66%), the lowest slopes, and the highest thresholds. The C population was intermediate with respect to all three properties but was much more similar to the slow As than to the fast As. All three fiber classes showed a negative correlation between slope and threshold. The majority of neurons showed a slowly adapting response to a maintained 2-s stimulus. Adapting neurons could be subdivided based on whether the fitted exponential curve decayed to zero or to a nonzero plateau; the latter group contained the most sensitive neurons in that they had the lowest thresholds and highest slopes. Nonadapting neurons generally had lower initial firing rates than adapting neurons. Fast A neurons exhibited greater and more rapid adaptation than slow A and C neurons. Neurons with the lowest slopes, regardless of CV, had relatively rapid adaptation. The more slowly conducting portion of the C population was distinguished from the other C neurons by a number of properties: more mechanically insensitive neurons, higher thresholds, and more nonadapting neurons. These differences in mechanical response properties may be related in part to differences in membrane currents involved in impulse generation that have been described in subpopulations of dorsal root ganglion cells.
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Affiliation(s)
- Dan Levy
- Department of Anesthesia and Critical Care, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215
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Chidiac JJ, Rifai K, Hawwa NN, Massaad CA, Jurjus AR, Jabbur SJ, Saadé NE. Nociceptive behaviour induced by dental application of irritants to rat incisors: a new model for tooth inflammatory pain. Eur J Pain 2002; 6:55-67. [PMID: 11888229 DOI: 10.1053/eujp.2001.0305] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Animal models simulating acute human pulpitis are still lacking. The rat incisors present a particular situation where most of their innervation is considered to be unmyelinated and concentrated mainly in the tooth pulp. This study reports on a new model for dental pain induced by inflammatory agents applied to the tooth pulps of incisors. In different groups of rats, artificial crowns were fixed on the lower incisors, after cutting 1-2mm of their distal extremities. A volume of 7-10 microl of solutions of saline, capsaicin (1-10mg/ml) or formalin (2.5% or 5%) was injected in the crown cavity, and the nociceptive behaviour was quantitated following a devised scoring method of four scales. Intradental application of capsaicin produced nociceptive scores in the form of one plateau for 1-2h depending on the concentration used. Similar results were obtained with intradental application of formalin 2.5%. The one plateau of nociceptive scores obtained with formalin contrasts with the biphasic aspect of nociceptive behaviour described with the intradermal formalin test. This discrepancy could be attributed to a difference in the types of afferent fibres involved in each situation. Pretreatment with morphine (2 mg/kg) attenuated, in a naloxone-reversible manner, the nociceptive behaviour observed following intradental application of capsaicin. Pretreatment with meloxicam (a cyclo-oxygenase-2 inhibitor) exerted a less pronounced attenuation of the nociceptive scores when compared with morphine. These results provide evidence for the validity of the described model for the simulation of tooth pulp inflammatory pain in awake animals.
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Affiliation(s)
- José-Johann Chidiac
- Department of Prosthodontics, School of Dentistry, Lebanese University, Beirut, Lebanon
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Pelissier T, Pajot J, Dallel R. The orofacial capsaicin test in rats: effects of different capsaicin concentrations and morphine. Pain 2002; 96:81-7. [PMID: 11932064 DOI: 10.1016/s0304-3959(01)00432-8] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The aim of this study was to develop a rat model of capsaicin-induced pain in the orofacial region. We examined the effects of subcutaneous injection of different doses of capsaicin (0.25, 0.4, 0.8, 1.5, 2.5, 25, 50, 100, 500 microg) on the face-grooming response. Injection of capsaicin into the vibrissa pad produced an immediate grooming of the injected area with ipsilateral fore- or hindpaw. A positive relationship between the amplitude of the grooming response and the capsaicin dose was observed until 1.5 microg, but with the highest concentrations (ranging from 25 to 500 microg) the amplitude of the response decreased. Morphine administered either systemically (in the neck, 0.5-4.0 mg/kg) or locally (0.25-1.0 mg/kg) reduced in a dose-dependent fashion the face grooming provoked by subcutaneous capsaicin (1.5 microg). The systemic and local morphine effects could be reversed by systemic (0.1 mg/kg) and local (0.05 mg/kg) administration of naloxone, respectively. The local administration of morphine (ED(50): 0.65 mg/kg) was more potent than systemic injection (ED50: 2.54 mg/kg) in reducing the grooming behavior. In conclusion, the orofacial capsaicin test appears to be a valid and reliable method for studying trigeminal pain mechanisms and testing analgesic drugs. The results of the present study also support the clinical use of peripheral opioid administration for the treatment of orofacial painful conditions.
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Affiliation(s)
- Teresa Pelissier
- Programa de Farmacología Molecular y Clínica, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile
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31
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Yiangou Y, Facer P, Ford A, Brady C, Wiseman O, Fowler CJ, Anand P. Capsaicin receptor VR1 and ATP-gated ion channel P2X3 in human urinary bladder. BJU Int 2001; 87:774-9. [PMID: 11412212 DOI: 10.1046/j.1464-410x.2001.02190.x] [Citation(s) in RCA: 133] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVES To determine the presence, distribution and molecular forms of the vanilloid receptor VR1, and confirm the presence and distribution of the ATP-gated ion channel P2X3 in the human urinary bladder. Materials and methods Normal urinary bladder tissues were obtained at postmortem from four subjects. Eight urinary bladder biopsies were also taken from patients with detrusor hyper-reflexia treated with intravesical resiniferatoxin. The specimens were studied using affinity-purified specific antibodies to VR1 and P2X3 by Western blotting and immunocytochemistry, and compared with immunostaining using antibodies to the pan-neuronal marker PGP 9.5 and Schwann cell marker S-100. RESULTS VR1- and P2X3-immunoreactive fine nerve fibres were scattered throughout the suburothelium of the normal bladder and cystoscopic biopsies, and traversed the muscle layer. They had a similar distribution to PGP 9.5-immunoreactive fibres, but there were fewer, suggesting localization in subsets of axons. Western blot studies showed an expected 100-kDa VR1 protein and a P2X3-immunoreactive 66-kDa protein. Conclusion VR1 and P2X3 are present in the human urinary bladder and may contribute to distinct pathophysiological states of bladder overactivity, in accord with their differential expression in sensory neurones. Intravesical vanilloids act via VR1 and are effective in the treatment of detrusor hyper-reflexia. P2X3 may represent a selective therapeutic target for other causes of overactive bladder.
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Affiliation(s)
- Y Yiangou
- Peripheral Neuropathy Unit, Imperial College School of Medicine, Hammersmith Hospital, London
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32
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Chaudhary P, Martenson ME, Baumann TK. Vanilloid receptor expression and capsaicin excitation of rat dental primary afferent neurons. J Dent Res 2001; 80:1518-23. [PMID: 11499505 DOI: 10.1177/00220345010800060801] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Little is known about the molecular mechanisms that cause excitation of neurons which innervate the teeth. We investigated whether rat dental sensory neurons express the vanilloid (capsaicin) receptor (VR1). Dental sensory neurons were identified by retrograde transport of the fluorescent dye DiIC18 placed in maxillary molars. Patch-clamp recordings in culture showed that 65% of DiIC18-labeled rat trigeminal ganglion neurons are excited by capsaicin. Responders covered the entire range of cell sizes examined (soma diameter, 24 to 48 microm). All non-responders had a soma diameter > 33 microm. Capsazepine (1 microM) reduced the capsaicin-evoked membrane current (6/6) and depolarization (7/7 responders). RT-PCR amplified a 375-bp product from DiIC18-labeled neurons which was identical to that expected for VR1. Thus, many rat dental primary afferent neurons are excited by capsaicin, and the response appears to be mediated by VR1. These results suggest that pharmacological blockers of VR1 may provide significant relief of dental pain.
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Affiliation(s)
- P Chaudhary
- Department of Neurological Surgery, Oregon Health & Science University, Portland 97201, USA
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Alavi AM, Dubyak GR, Burnstock G. Immunohistochemical evidence for ATP receptors in human dental pulp. J Dent Res 2001; 80:476-83. [PMID: 11332536 DOI: 10.1177/00220345010800021501] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Evidence is accumulating which supports a role for ATP in the initiation of pain by acting on P2X receptors, in particular P2X3, expressed on nociceptive afferent nerve terminals. To investigate whether this receptor plays a role in dental pain, we studied the presence and distribution of P2X3 receptors in human dental pulp, and their co-localization with other neural markers. Pulps were removed from extracted third molars and immunohistochemically stained with an antibody against P2X3 receptors. P2X3 immunoreactive (-ir) nerve fibers were detected in the main body of the pulp, in the sub-odontoblastic plexus of Raschkow, and within the odontoblastic area. Co-localization of the P2X3-ir neurons with neurofilament protein (NF) showed that the majority of the fibers were positive for both NF and P2X3. Double labeling with isolectin B4 (IB4) showed that all P2X3-ir neurons also bind IB4. We conclude that P2X3 receptors are present on both myelinated and unmyelinated nerve fibers in human dental pulp and may play a role in dental pain mechanisms.
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Affiliation(s)
- A M Alavi
- Autonomic Neuroscience Institute, Royal Free Hospital School of Medicine, London, UK.
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Byers MR, Närhi MV. Dental injury models: experimental tools for understanding neuroinflammatory interactions and polymodal nociceptor functions. CRITICAL REVIEWS IN ORAL BIOLOGY AND MEDICINE : AN OFFICIAL PUBLICATION OF THE AMERICAN ASSOCIATION OF ORAL BIOLOGISTS 2000; 10:4-39. [PMID: 10759425 DOI: 10.1177/10454411990100010101] [Citation(s) in RCA: 199] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Recent research has shown that peripheral mechanisms of pain are much more complex than previously thought, and they differ for acutely injured normal tissues compared with chronic inflammation or neuropathic (nerve injury) pain. The purpose of the present review is to describe uses of dental injury models as experimental tools for understanding the normal functions of polymodal nociceptive nerves in healthy tissues, their neuroinflammatory interactions, and their roles in healing. A brief review of normal dental innervation and its interactions with healthy pulp tissue will be presented first, as a framework for understanding the changes that occur after injury. Then, the different types of dental injury that allow gradation of the extent of tissue damage will be described, along with the degree and duration of inflammation, the types of reactions in the trigeminal ganglion and brainstem, and the type of healing. The dental injury models have some unique features compared with neuroinflammation paradigms that affect other peripheral tissues such as skin, viscera, and joints. Peripheral inflammation models can all be contrasted to nerve injury studies that produce a different kind of neuroplasticity and neuropathic pain. Each of these models provides different insights about the normal and pathologic functions of peripheral nerve fibers and their effects on tissue homeostasis, inflammation, and wound healing. The physical confinement of dental pulp and its innervation within the tooth, the high incidence of polymodal A-delta and C-fibers in pulp and dentin, and the somatotopic organization of the trigeminal ganglion provide some special advantages for experimental design when dental injury models are used for the study of neuroinflammatory interactions.
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Affiliation(s)
- M R Byers
- Department of Anesthesiology, University of Washington, Seattle 98195-6540, USA
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