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Byers MR, Calkins DF. Trigeminal sensory nerve patterns in dentine and their responses to attrition in rat molars. Arch Oral Biol 2021; 129:105197. [PMID: 34146928 DOI: 10.1016/j.archoralbio.2021.105197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 06/03/2021] [Accepted: 06/08/2021] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Our goal was to define trigeminal nerve ending quantities and patterns in rat molar dentine, their responses to attrition (tooth wear), and their associated odontoblasts and connections with pulpal plexuses. DESIGN Trigeminal ganglia were labeled for axonal transport of 3H-proteins to dentinal nerve endings in male rats (3-13 months old). Autoradiography detected radio-labeled dentinal tubules as indicators of nerve ending locations. Quantitative morphometry was done (ANOVA, t-tests), and littermates were compared for attrition and innervation. RESULTS There were six dentinal patterns, only two of which had an associated neural plexus of Raschkow and cell-free zone (Den-1, Den-2). Other nerves entered dentin from bush-like endings near elongated odontoblasts (Den-B), as single fibers (Den-X), as networks in predentine (PdN), or as single fibers in tertiary dentine at cusp tips (Den-S). There were at least 186,600 innervated dentinal tubules within the set of three right maxillary molars of the best-labeled rat, and similar densities were found in other rats. Attrition levels differed among cusps and in littermates (t-test p < 0.02-0.0001), but the matched right/left cusps per rat were similar. Innervations of tertiary and enamel-free dentine (Den-S, Den-X) were preserved in all rats. Den-B and Den-2 coronal patterns were unchanged unless displaced by dentinogenesis. Den-1 losses occurred in older cusps, while Den-2 patterns increased near cervical and intercuspal odontoblasts. CONCLUSIONS The extensive molar dentinal innervation had unique distributions per rat per cusp that depended on region (buccal, middle, palatal) and attrition, but only two of six patterns connected to a plexus of Raschkow.
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Affiliation(s)
- Margaret R Byers
- Department of Anesthesiology and Pain Medicine, Univ. Washington, Seattle, WA, 98195-6540, USA.
| | - Dianne F Calkins
- Department of Anesthesiology and Pain Medicine, Univ. Washington, Seattle, WA, 98195-6540, USA
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Byers MR. Chewing causes rapid changes in immunoreactive nerve patterns in rat molar teeth: Implications for dental proprioception and pain. Arch Oral Biol 2019; 107:104511. [PMID: 31445382 DOI: 10.1016/j.archoralbio.2019.104511] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 07/19/2019] [Accepted: 07/28/2019] [Indexed: 01/06/2023]
Abstract
OBJECTIVE This study tests the hypothesis that normal use of teeth (chewing) causes changes in immunoreactive-(IR) patterns for endings of large Aβ and CGRP axons in rat molar cusps. DESIGN First, a new paradigm to test chewing in adult male rats was developed. Then IR patterns for large dental axons were analysed for a calcium-binding protein, parvalbumin (PV), heavy neurofilament protein-200 (NFP), and vesicle-release molecule synaptophysin (SYN) that all typify large dental axons and proprioceptors for comparison with endings of CGRP-IR neuropeptide axons. The behavior groups were: (1) daytime sleeping/fasting (Group:SF); (2) brief feeding after 8-11 h of daytime sleeping/fasting (Group:SF-C); (3) normal nocturnal feeding (Group:N); (4) nocturnal fasting (Group:NF); (5) brief feeding/chewing after nocturnal fasting (Group:NF-C). RESULTS Nerve endings with NFP-, PV-, or SYN-IR were lost or altered in pulp and dentin in all chewing groups. Other endings with CGRP-IR were near those with PV-, NFP- and SYN-IR at the pulp-dentin border and in dentin, and they also lost immunoreactivity in all chewing groups. The special beaded regions along the crown pulp/dentin borders lost neural labeling in all chewing groups. Nerves of molar roots and periodontal ligament were not changed. CONCLUSIONS Rapid neural reactions to chewing show extensive, reversible, non-nociceptive depletions of crown innervation. Those changes were rapid enough to occur during normal feeding followed by recovery during rest. The new dental paradigm related to chewing and fasting allows dissection of intradental proprioceptive-like mechanisms during normal tooth functions for comparison with nociceptive and mechanosensitive reactions after injury or inflammation.
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Affiliation(s)
- Margaret R Byers
- Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA, 98195-6540 USA.
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Hossain MZ, Bakri MM, Yahya F, Ando H, Unno S, Kitagawa J. The Role of Transient Receptor Potential (TRP) Channels in the Transduction of Dental Pain. Int J Mol Sci 2019; 20:ijms20030526. [PMID: 30691193 PMCID: PMC6387147 DOI: 10.3390/ijms20030526] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Revised: 01/18/2019] [Accepted: 01/24/2019] [Indexed: 12/18/2022] Open
Abstract
Dental pain is a common health problem that negatively impacts the activities of daily living. Dentine hypersensitivity and pulpitis-associated pain are among the most common types of dental pain. Patients with these conditions feel pain upon exposure of the affected tooth to various external stimuli. However, the molecular mechanisms underlying dental pain, especially the transduction of external stimuli to electrical signals in the nerve, remain unclear. Numerous ion channels and receptors localized in the dental primary afferent neurons (DPAs) and odontoblasts have been implicated in the transduction of dental pain, and functional expression of various polymodal transient receptor potential (TRP) channels has been detected in DPAs and odontoblasts. External stimuli-induced dentinal tubular fluid movement can activate TRP channels on DPAs and odontoblasts. The odontoblasts can in turn activate the DPAs by paracrine signaling through ATP and glutamate release. In pulpitis, inflammatory mediators may sensitize the DPAs. They could also induce post-translational modifications of TRP channels, increase trafficking of these channels to nerve terminals, and increase the sensitivity of these channels to stimuli. Additionally, in caries-induced pulpitis, bacterial products can directly activate TRP channels on DPAs. In this review, we provide an overview of the TRP channels expressed in the various tooth structures, and we discuss their involvement in the development of dental pain.
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Affiliation(s)
- Mohammad Zakir Hossain
- Department of Oral Physiology, School of Dentistry, Matsumoto Dental University, 1780 Gobara Hirooka, Shiojiri, Nagano 399-0781, Japan.
| | - Marina Mohd Bakri
- Department of Oral and Craniofacial Sciences, Faculty of Dentistry, University of Malaya, Kuala Lumpur 50603, Malaysia.
| | - Farhana Yahya
- Department of Oral and Craniofacial Sciences, Faculty of Dentistry, University of Malaya, Kuala Lumpur 50603, Malaysia.
| | - Hiroshi Ando
- Department of Biology, School of Dentistry, Matsumoto Dental University, 1780 Gobara, Hirooka, Shiojiri, Nagano 399-0781, Japan.
| | - Shumpei Unno
- Department of Oral Physiology, School of Dentistry, Matsumoto Dental University, 1780 Gobara Hirooka, Shiojiri, Nagano 399-0781, Japan.
| | - Junichi Kitagawa
- Department of Oral Physiology, School of Dentistry, Matsumoto Dental University, 1780 Gobara Hirooka, Shiojiri, Nagano 399-0781, Japan.
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Michot B, Lee CS, Gibbs JL. TRPM8 and TRPA1 do not contribute to dental pulp sensitivity to cold. Sci Rep 2018; 8:13198. [PMID: 30181551 PMCID: PMC6123413 DOI: 10.1038/s41598-018-31487-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 08/15/2018] [Indexed: 01/17/2023] Open
Abstract
Sensory neurons innervating the dental pulp have unique morphological and functional characteristics compared to neurons innervating other tissues. Stimulation of dental pulp afferents whatever the modality or intensity of the stimulus, even light mechanical stimulation that would not activate nociceptors in other tissues, produces an intense pain. These specific sensory characteristics could involve receptors of the Transient Receptor Potential channels (TRP) family. In this study, we compared the expression of the cold sensitive receptors TRPM8 and TRPA1 in trigeminal ganglion neurons innervating the dental pulp, the skin of the cheek or the buccal mucosa and we evaluated the involvement of these receptors in dental pulp sensitivity to cold. We showed a similar expression of TRPM8, TRPA1 and CGRP in sensory neurons innervating the dental pulp, the skin or the mucosa. Moreover, we demonstrated that noxious cold stimulation of the tooth induced an overexpression of cFos in the trigeminal nucleus that was not prevented by the genetic deletion of TRPM8 or the administration of the TRPA1 antagonist HC030031. These data suggest that the unique sensory characteristics of the dental pulp are independent to TRPM8 and TRPA1 receptors expression and functionality.
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Affiliation(s)
- Benoit Michot
- Department of Endodontics, New York University College of Dentistry, New York, USA.
| | - Caroline S Lee
- Department of Endodontics, New York University College of Dentistry, New York, USA
| | - Jennifer L Gibbs
- Department of Endodontics, New York University College of Dentistry, New York, USA
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Byers MR, Cornel LM. Multiple complex somatosensory systems in mature rat molars defined by immunohistochemistry. Arch Oral Biol 2017; 85:84-97. [PMID: 29035722 DOI: 10.1016/j.archoralbio.2017.09.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 08/24/2017] [Accepted: 09/13/2017] [Indexed: 12/25/2022]
Abstract
OBJECTIVE Intradental sensory receptors trigger painful sensations and unperceived mechanosensitivity, but the receptor bases for those functions are only partly defined. We present new evidence here concerning complex endings of myelinated axons in rat molars. DESIGN We sectioned mature rat jaws in sagittal and transverse planes to analyze neural immunoreactivity (IR) for parvalbumin, peripherin, neurofilament protein, neurotrophin receptors, synaptophysin, calcitonin gene-related peptide (CGRP), or mas-related g-protein-receptor-d (Mrgprd). RESULTS We found two complex sensory systems in mature rat molar dentin that labeled with neurofilament protein-IR, plus either parvalbumin-IR or peripherin-IR. The parvalbumin-IR system made extensively branched, beaded endings focused into dentin throughout each pulp horn. The peripherin-IR system primarily made unbeaded, fork-shaped dentinal endings scattered throughout crown including cervical regions. Both of these systems differed from neuropeptide CGRP-IR. In molar pulp we found peripherin- and parvalbumin-IR layered endings, either near special horizontal plexus arrays or in small coiled endings near tangled plexus, each with specific foci for specific pulp horns. Parvalbumin-IR nerve fibers had Aβ axons (5-7μm diameter), while peripherin-IR axons were thinner Aδ size (2-5μm). Mechano-nociceptive Mrgprd-IR was only found in peripherin-IR axons. CONCLUSIONS Complex somatosensory receptors in rat molars include two types of dentinal endings that both differ from CGRP-IR endings, and at least two newly defined types of pulpal endings. The PV-IR neurons with their widely branched, synaptophysin-rich, intradentinal beaded endings are good candidates for endodontic non-nociceptive, low threshold, unperceived mechanoreceptors. The complex molar dentinal and pulpal sensory systems were not found in rat incisors.
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Affiliation(s)
- Margaret R Byers
- Department of Anesthesiology & Pain Medicine, Box 356540, University of Washington, Seattle, WA 98195-6540, USA.
| | - Leanne M Cornel
- Department of Anesthesiology & Pain Medicine, Box 356540, University of Washington, Seattle, WA 98195-6540, USA
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Kovačič U, Tesovnik B, Molnar N, Cör A, Skalerič U, Gašperšič R. Dental pulp and gingivomucosa in rats are innervated by two morphologically and neurochemically different populations of nociceptors. Arch Oral Biol 2013; 58:788-95. [PMID: 23411402 DOI: 10.1016/j.archoralbio.2013.01.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Revised: 01/14/2013] [Accepted: 01/17/2013] [Indexed: 12/25/2022]
Abstract
OBJECTIVES Difference in phenotypes of sensory neurons innervating dental pulp or gingivomucosa may be responsible for intense pain sensations in pulpitis in contrast to relatively painless chronic periodontitis. Therefore, we classified these neurons according to their size and two neurochemical characteristics of nociceptors, their TrkA expression and isolectin IB4 binding. DESIGN In rats (n=6) fluorescent tracers Fluorogold and TrueBlue were simultaneously applied into the standard-sized tooth cavity and nearby gingival sulcus, respectively. After the fluorescence on paraffin trigeminal ganglia (TG) sections was identified and photographed, immunohistochemistry for TrkA expression and IB4 binding was performed on the same sections. RESULTS The average sizes of TG neurons projecting to the gingivomucosa and dental pulp were 894±441μm(2) and 1012±381μm(2), respectively. The proportions of small-sized gingival and pulpal neurons were 14% and 5%, respectively (p<0.05). The proportions of TrkA-positive neurons among all gingival or pulpal neurons were 76% and 86%, respectively (p<0.05). Among all gingival or pulpal neurons the proportions of IB4-positive neurons were 46% and 3% (p<0.001), respectively, and the majority of them were small-medium sized. CONCLUSIONS Dental pulp and gingivomucosa are richly innervated by nociceptive TrkA-expressing neurons. However, while great majority of pulpal neurons are larger NGF-dependent A-fibre nociceptors without affinity to bind IB4, almost half of the gingival neurons are smaller IB4 binding C-fibre nociceptors. The difference in phenotype of sensory neurons might partially explain the different sensitivity of both tissues during normal and pathological conditions.
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Affiliation(s)
- Uroš Kovačič
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 2, 1000 Ljubljana, Slovenia
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Fried K, Sessle BJ, Devor M. The paradox of pain from tooth pulp: low-threshold "algoneurons"? Pain 2011; 152:2685-2689. [PMID: 21889261 DOI: 10.1016/j.pain.2011.08.004] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Revised: 07/24/2011] [Accepted: 08/02/2011] [Indexed: 11/29/2022]
Affiliation(s)
- Kaj Fried
- Department of Dental Medicine, Karolinska Institutet, S-141 04 Huddinge, Sweden Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada M5G 1G6 Department of Cell and Developmental Biology, Institute of Life Sciences and Center for Research on Pain, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
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Tarsa L, Balkowiec A. Nerve growth factor regulates synaptophysin expression in developing trigeminal ganglion neurons in vitro. Neuropeptides 2009; 43:47-52. [PMID: 19019428 PMCID: PMC2637929 DOI: 10.1016/j.npep.2008.09.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Revised: 08/26/2008] [Accepted: 09/29/2008] [Indexed: 11/19/2022]
Abstract
The role of neuronal growth factors in synaptic maturation of sensory neurons, including trigeminal ganglion (TG) neurons, remains poorly understood. Here, we show that nerve growth factor (NGF) regulates the intracellular distribution of the synaptic vesicle protein synaptophysin (Syp) in newborn rat TG neurons in vitro. While reducing the number of Syp-positive cell bodies, NGF dramatically increases Syp immunoreactivity in both proximal and distal segments of the neurite. Intriguingly, the increase in Syp immunoreactivity occurs only in neuron-enriched cultures, in which the number of non-neuronal cells is significantly reduced. Together, our data indicate that NGF is a candidate molecule involved in early postnatal maturation of TG neurons, including control of presynaptic assembly, and thereby formation of synaptic connections.
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Affiliation(s)
- L Tarsa
- Department of Integrative Biosciences, Oregon Health and Science University, 611 SW Campus Drive, Portland, OR 97239, USA
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Pelegrini-da-Silva A, Oliveira MCG, Parada CA, Tambeli CH. Nerve growth factor acts with the beta2-adrenoceptor to induce spontaneous nociceptive behavior during temporomandibular joint inflammatory hyperalgesia. Life Sci 2008; 83:780-5. [PMID: 18930742 DOI: 10.1016/j.lfs.2008.09.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Revised: 09/13/2008] [Accepted: 09/17/2008] [Indexed: 12/21/2022]
Abstract
AIMS The aim of this study was to investigate whether the injection of nerve growth factor induces spontaneous nociceptive behavior in the intact or sensitized temporomandibular joint (TMJ) of rats. MAIN METHODS NGF was injected into the TMJ 1 h after the TMJ injection of saline or carrageenan and the spontaneous nociceptive behavior was quantified. The mechanism involved in this phenomenon was investigated by the injection of NGF into the carrageenan-sensitized TMJ in the presence of indomethacin or of beta-adrenergic antagonists. KEY FINDINGS NGF injected into the TMJ sensitized by a prior TMJ injection of carrageenan but not into the intact TMJ induced a significant nociceptive behavior. Co-injection of the non-specific Trk receptor antagonist k252A with NGF 1 h after the TMJ injection of carrageenan significantly reduced NGF-induced spontaneous nociception supporting the Trk receptor activation in this nociceptive effect. Blockade of prostaglandin synthesis by indomethacin before the TMJ injection of carrageenan did not reduce NGF-induced nociception. Co-administration of carrageenan with the beta2-adrenoceptor antagonist ICI 118.55 but not with the beta1-adrenoceptor antagonist atenolol significantly reduced NGF-induced nociception. The injection of NGF the TMJ sensitized by a previous TMJ injection of epinephrine also induced nociceptive behavior. SIGNIFICANCE Taken together, these results indicate that NGF can induce TMJ nociception during TMJ inflammation. Moreover, the expression of this nociceptive response seems to depend on the synergic activity of NGF and sympathetic amines released during TMJ inflammation acting on beta2-adrenergic receptors.
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Affiliation(s)
- Adriana Pelegrini-da-Silva
- Department of Physiological Sciences, Laboratory of Orofacial Pain, Piracicaba Dental School, University of Campinas-Piracicaba, São Paulo, Brazil.
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FRISTAD INGE, BLETSA ATHANASIA, BYERS MARGARET. Inflammatory nerve responses in the dental pulp. ACTA ACUST UNITED AC 2007. [DOI: 10.1111/j.1601-1546.2010.00247.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
In this article, we review the key basic mechanisms associated with this phenomena and more recently identified mechanisms that are current areas of interest. Although many of these pain mechanisms apply throughout the body, we attempt to describe these mechanisms in the context of trigeminal pain.
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Affiliation(s)
- Michael A Henry
- Department of Endodontics, University of Texas Health Science Center at San Antonio School of Dentistry, Mail Code 7892, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA.
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