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Peripheral Purinergic Modulation in Pediatric Orofacial Inflammatory Pain Affects Brainstem Nitroxidergic System: A Translational Research. BIOMED RESEARCH INTERNATIONAL 2022; 2022:1326885. [PMID: 35309172 PMCID: PMC8933089 DOI: 10.1155/2022/1326885] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 01/19/2022] [Accepted: 01/22/2022] [Indexed: 11/18/2022]
Abstract
Physiology of orofacial pain pathways embraces primary afferent neurons, pathologic changes in the trigeminal ganglion, brainstem nociceptive neurons, and higher brain function regulating orofacial nociception. The goal of this study was to investigate the nitroxidergic system alteration at brainstem level (spinal trigeminal nucleus), and the role of peripheral P2 purinergic receptors in an experimental mouse model of pediatric inflammatory orofacial pain, to increase knowledge and supply information concerning orofacial pain in children and adolescents, like pediatric dentists and pathologists, as well as oro-maxillo-facial surgeons, may be asked to participate in the treatment of these patients. The experimental animals were treated subcutaneously in the perioral region with pyridoxalphosphate-6-azophenyl-2′,4′-disulphonic acid (PPADS), a P2 receptor antagonist, 30 minutes before formalin injection. The pain-related behavior and the nitroxidergic system alterations in the spinal trigeminal nucleus using immunohistochemistry and western blotting analysis have been evaluated. The local administration of PPADS decreased the face-rubbing activity and the expression of both neuronal and inducible nitric oxide (NO) synthase isoforms in the spinal trigeminal nucleus. These results underline a relationship between orofacial inflammatory pain and nitroxidergic system in the spinal trigeminal nucleus and suggest a role of peripheral P2 receptors in trigeminal pain transmission influencing NO production at central level. In this way, orofacial pain physiology should be elucidated and applied to clinical practice in the future.
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Austah ON, Ruparel NB, Henry MA, Fajardo RJ, Schmitz JE, Diogenes A. Capsaicin-sensitive Innervation Modulates the Development of Apical Periodontitis. J Endod 2016; 42:1496-502. [PMID: 27523907 DOI: 10.1016/j.joen.2016.06.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 06/07/2016] [Accepted: 06/16/2016] [Indexed: 01/04/2023]
Abstract
INTRODUCTION Nociceptive neurons play a critical role in the detection of stimuli evoking actual or potential tissue injury. In addition, they are involved in neurogenic inflammation by the peripheral release of neuropeptides such as calcitonin gene-related peptide (CGRP). The dental pulp and periradicular tissues are innervated by capsaicin-sensitive neurons known to release CGRP. However, the role of these capsaicin-sensitive neurons in the development of apical periodontitis is largely unknown. The aim of this study was to evaluate the contribution of peptidergic neurons to the development of apical periodontitis. METHODS Neonatal Sprague-Dawley rats were injected with vehicle (control group) or a single subcutaneous capsaicin dose to cause the selective ablation of peptidergic neurons (neonatal capsaicin group). Ablation of capsaicin-sensitive neurons was verified with confocal microscopy, capsaicin-induced eye-wipe nocifensive behavior test, and by measurement of immunoreactive CGRP levels in the dental pulp. Five weeks after ablation, standardized pulp exposures were made in the mandibular left first molars. Mandibles were harvested at 7, 14, 21, and 28 days after pulp exposure and imaged with micro-computed tomography (μCT) to quantify apical lesion volume. Data were analyzed by using 2-way ANOVA analysis with Bonferroni post hoc test. RESULTS Rats in the control group displayed a robust capsaicin-induced nocifensive behavior, which was nearly abolished in the neonatal capsaicin group. In addition, the neonatal capsaicin group showed a significant depletion of susceptible neurons and CGRP in the dental pulp compared with control. Importantly, micro-computed tomography analysis showed larger periradicular lesions at 7 and 14 days after pulp exposure in the neonatal capsaicin group when compared with control. CONCLUSIONS Results identify a protective role for capsaicin-sensitive neurons in the initial phase of apical periodontitis. Thus, interventions or disorders that alter activity of capsaicin-sensitive fibers are likely to alter the development of apical periodontitis.
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Affiliation(s)
- Obadah N Austah
- Department of Endodontics, University of Texas Health Science Center at San Antonio, San Antonio, Texas; Department of Endodontics, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Nikita B Ruparel
- Department of Endodontics, University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Michael A Henry
- Department of Endodontics, University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Roberto J Fajardo
- Department of Orthopedics, University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - James E Schmitz
- Department of Orthopedics, University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Anibal Diogenes
- Department of Endodontics, University of Texas Health Science Center at San Antonio, San Antonio, Texas.
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Kim YS, Park JH, Choi SJ, Bae JY, Ahn DK, McKemy DD, Bae YC. Central connectivity of transient receptor potential melastatin 8-expressing axons in the brain stem and spinal dorsal horn. PLoS One 2014; 9:e94080. [PMID: 24710558 PMCID: PMC3977991 DOI: 10.1371/journal.pone.0094080] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 03/11/2014] [Indexed: 12/12/2022] Open
Abstract
Transient receptor potential melastatin 8 (TRPM8) ion channels mediate the detection of noxious and innocuous cold and are expressed by primary sensory neurons, but little is known about the processing of the TRPM8-mediated cold information within the trigeminal sensory nuclei (TSN) and the spinal dorsal horn (DH). To address this issue, we characterized TRPM8-positive (+) neurons in the trigeminal ganglion and investigated the distribution of TRPM8+ axons and terminals, and their synaptic organization in the TSN and in the DH using light and electron microscopic immunohistochemistry in transgenic mice expressing a genetically encoded axonal tracer in TRPM8+ neurons. TRPM8 was expressed in a fraction of small myelinated primary afferent fibers (23.7%) and unmyelinated fibers (76.3%), suggesting that TRPM8-mediated cold is conveyed via C and Aδ afferents. TRPM8+ axons were observed in all TSN, but at different densities in the dorsal and ventral areas of the rostral TSN, which dominantly receive sensory afferents from intra- and peri-oral structures and from the face, respectively. While synaptic boutons arising from Aδ and non-peptidergic C afferents usually receive many axoaxonic contacts and form complex synaptic arrangements, TRPM8+ boutons arising from afferents of the same classes of fibers showed a unique synaptic connectivity; simple synapses with one or two dendrites and sparse axoaxonic contacts. These findings suggest that TRPM8-mediated cold is conveyed via a specific subset of C and Aδ afferent neurons and is processed in a unique manner and differently in the TSN and DH.
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Affiliation(s)
- Yun Sook Kim
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Korea
| | - Jun Hong Park
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Korea
| | - Su Jung Choi
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Korea
| | - Jin Young Bae
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Korea
| | - Dong Kuk Ahn
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Korea
| | - David D McKemy
- Neurobiology Section, Department of Biological Sciences, University of Southern California, Los Angeles, California, United States of America
| | - Yong Chul Bae
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Korea
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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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Borsani E, Albertini R, Labanca M, Lonati C, Rezzani R, Rodella LF. Peripheral purinergic receptor modulation influences the trigeminal ganglia nitroxidergic system in an experimental murine model of inflammatory orofacial pain. J Neurosci Res 2011; 88:2715-26. [PMID: 20648657 DOI: 10.1002/jnr.22420] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
ATP plays an important role as an endogenous pain mediator generating and/or modulating pain signaling from the periphery to the central nervous system. The aim of this study was to analyze the role of peripheral purinergic receptors in modulation of the nitroxidergic system at a trigeminal ganglia level by monitoring changes in nitric oxide synthase isoforms. We also evaluated Fos-positive neurons in brainstem (spinal trigeminal nucleus) and pain-related behavior. We found that local administration of the P2 purinergic receptor antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) decreased face-rubbing activity, nitric oxide synthase isoform expression in trigeminal ganglia, and Fos expression in spinal trigeminal nucleus after subcutaneous injection of formalin. These results suggest a role for peripheral P2 purinergic receptors in orofacial pain transmission through modulation of the nitroxidergic system. .
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Affiliation(s)
- Elisa Borsani
- Division of Human Anatomy, Department of Biomedical Sciences and Biotechnologies, Brescia University, 25123 Brescia, Italy
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Park ES, Kim SY, Youn DH. NMDA receptor, PKC and ERK prevent fos expression induced by the activation of group I metabotropic glutamate receptors in the spinal trigeminal subnucleus oralis. Mol Cells 2010; 30:461-6. [PMID: 20848228 DOI: 10.1007/s10059-010-0140-x] [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: 06/08/2010] [Revised: 08/16/2010] [Accepted: 08/24/2010] [Indexed: 12/19/2022] Open
Abstract
Fos, a protein product of immediate early gene c-fos, has been used as a marker for activation of nociceptive neurons in central nervous system including spinal trigeminal nucleus (Vsp). By noxious stimulation applied to orofacial area, the expression of Fos occurred in the Vsp pars oralis (Vo), the subnucleus receiving inputs from trigeminal primary afferents that predominantly innervate intraoral receptive fields. The present study demonstrates that the in vitro activation of group I metabotropic glutamate receptors (mGluRs; mGluR1 and 5) by bath-application of their well-known agonist (S)-3,5-dihydroxyphenylglycine (DHPG) increased the number of Fos-expressing neurons in the Vo area. In addition, bath application of DHPG caused inward currents, a parameter of neuronal excitation, in the Vo neurons held at -70 mV in voltage-clamp mode of whole-cell recordings. In further experiments characterizing two phenomena, the increased Fos expression in the Vo was mediated by an additive activation of both mGluR1 and mGluR5, which required the activation of N-methyl-D-aspartate (NMDA) receptors, protein kinase C (PKC) and extracellular signal-regulated kinase (ERK). In contrast, the inward currents were mediated only by mGluR1, but not by others. The data resulting from this in vitro study indicate that the DHPG-induced membrane depolarisation or neuronal excitation may be upstream to, or skip, the NMDA receptor, PKC and ERK pathways for the DHPG-induced Fos expression.
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Affiliation(s)
- Eun-Sung Park
- Department of Oral Physiology, School of Dentistry and Brain Korea 21, Brain Science and Engineering Institute, Kyungpook National University, Daegu, 700-412, Korea
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Wu LA, Huang J, Wang W, Wang W, Li YQ, Wang XJ, Wu SX. Activation of GABAergic neurons following tooth pulp stimulation. J Dent Res 2010; 89:532-6. [PMID: 20332333 DOI: 10.1177/0022034510363231] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The functional impact of GABA (gamma-aminobutyric acid)ergic neurons in nociceptive transmission of the spinal trigeminal nucleus is not fully established. Using both the glutamic acid decarboxylase (GAD)(67)-green fluorescence protein (GFP) knock-in mouse and the tooth pulp stimulation model, we performed double-immunofluorescent histochemistry to determine the characteristics of GABAergic neuron activation in the spinal trigeminal nucleus. The number of Fos-positive GABAergic neuronal profiles was significantly increased 2 hrs after tooth pulp stimulation. The Fos/GFP double-labeled neurons were mainly present in superficial laminae of the spinal trigeminal subnucleus interpolaris-caudalis transition (Vi/Vc) and subnucleus caudalis (Vc) on the side ipsilateral to the stimulation. Subsequently, the number of double-labeled neurons decreased gradually and became comparable with that of the controls by 48 hrs. Our results provide direct morphological evidence that a subset of GABAergic neurons in the spinal trigeminal system was activated during tooth pulp stimulation.
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Affiliation(s)
- L-A Wu
- Department of Paediatric Dentistry, School of Stomatology, Fourth Military Medical University, No. 145 West Changle Road, Xi'an 710032, China
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AITA M, MAEDA T, SEO K. The effect of neonatal capsaicin treatment on the CGRP-immunoreaction in the trigeminal subnucleus caudalis of mice. Biomed Res 2008; 29:33-42. [DOI: 10.2220/biomedres.29.33] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Worsley MA, Davies SL, Clayton NM, Bountra C, Loescher AR, Robinson PP, Boissonade FM. The effect of inflammation on Fos expression in the ferret trigeminal nucleus. Eur J Oral Sci 2007; 115:40-7. [PMID: 17305715 DOI: 10.1111/j.1600-0722.2007.00411.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
We have previously carried out detailed characterization and identification of Fos expression within the trigeminal nucleus after tooth pulp stimulation in ferrets. The aim of this study was to determine the effect of pulpal inflammation on the excitability of central trigeminal neurons following tooth pulp stimulation. Adult ferrets were prepared under anesthesia to allow tooth pulp stimulation, recording from the digastric muscle, and intravenous injections at a subsequent experiment. In some animals, pulpal inflammation was induced by introducing human caries into a deep buccal cavity. After 5 d, animals were re-anaethetized, and the teeth were stimulated at 10 times the threshold of the jaw-opening reflex. Stimulation of all tooth pulps induced ipsilateral Fos in the trigeminal subnuclei caudalis and oralis. All non-stimulated animals showed negligible Fos labeling, with no differences recorded between inflamed and non-inflamed groups. Following tooth pulp stimulation, Fos expression was greater in animals with inflamed teeth than in animals with non-inflamed teeth, with the greatest effect seen in the subnucleus caudalis. These results suggest that inflammation increases the number of trigeminal brainstem neurons activated by tooth pulp stimulation; this may be mediated by peripheral or central mechanisms.
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Affiliation(s)
- Matthew A Worsley
- Department of Oral and Maxillofacial Medicine and Surgery, School of Clinical Dentistry, University of Sheffield, UK.
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Okere CO, Waterhouse BD. Activity-dependent heterogeneous populations of nitric oxide synthase neurons in the rat dorsal raphe nucleus. Brain Res 2006; 1086:117-32. [PMID: 16616732 DOI: 10.1016/j.brainres.2006.02.107] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2006] [Revised: 02/17/2006] [Accepted: 02/20/2006] [Indexed: 11/18/2022]
Abstract
The brainstem dorsal raphe nucleus (DRN) contains an abundant distribution of nitric oxide (NO) synthase (NOS)-containing neuronal profiles in two distinct populations: faint- and intense-immunoreactive cells in midline (ventromedial and dorsomedial) and lateral wing subregions, respectively. This study tested the hypothesis that different functional dynamics underlie the topography of NOS-containing cells in the DRN rostrocaudal and mediolateral neuraxis by using a capsaicin challenge paradigm (50 mg/kg, subcutaneous). Compared with vehicle, capsaicin significantly and preferentially increased nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d, an index of constitutive NOS) reactivity in the rostral midline and caudal lateral wing subregions. Furthermore, capsaicin activated more Fos-positive cells than vehicle within all subregions of the DRN but with a caudal versus rostral predominance in activation pattern. In addition, a high proportion of capsaicin-induced Fos cells in the midline but almost none in lateral wing stained for NADPH-d. These observations suggest the existence of two functionally distinct populations of NOS neurons in the DRN. Furthermore, capsaicin increased galanin immunoreactivity with predominant staining in cell soma and fiber processes in midline and lateral wing subregions of the nucleus, respectively. The total capsaicin-induced galanin immunoreactivity was higher in rostral versus caudal DRN, and a high proportion of galanin-positive cells in the midline also contained NADPH-d and neuronal NOS, thus suggesting a potential NO-galanin interaction in these neurons. The differential pattern of Fos/NADPH-d colocalization across the nucleus suggests that midline and lateral wing NOS neurons of the DRN express their neuromodulatory actions on discrete efferent targets via different intracellular mechanisms.
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Affiliation(s)
- Chuma O Okere
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, 2900 W Queen Lane, Philadelphia, PA 19129, USA.
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Aita M, Maeda T, Takagi R, Seo K. Postnatal development of substance P-immunoreaction in the trigeminal caudalis of neonatally capsaicin-treated mice. ACTA ACUST UNITED AC 2006; 68:311-20. [PMID: 16477150 DOI: 10.1679/aohc.68.311] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The trigeminal subnucleus caudalis (Vc) is a critical relay site for processing nociceptive afferent input from the orofacial area in addition to its modulation by neuroplastic change. Although an administration of capsaicin in neonates induces a selective destruction of substance P (SP)-immunoreactive nerve fibers, little information is available regarding its detailed effects on the Vc, particularly during postnatal development. The present study examined postnatal changes in the distribution of SP in the Vc and trigeminal ganglion (TG) by immunohistochemical techniques in naïve (NV) and neonatally capsaicin-treated (CP) mice, combined with a quantitative analysis. The neonatal mice received a single subcutaneous injection of capsaicin (50 mg/kg) at 48 hours after birth. The neural density of the SP-immunoreaction decreased to approximately a quarter of that in 1-week-old NV mice but increased to three-quarters of that in the NV in the superficial area after postnatal week 2. A double staining with SP and myelin basic protein confirmed the absence of any SP-immunoreaction in the myelinated nerve fibers in both NV and CP mice. The SP-immunoreaction never overlapped with non-peptidergic IB4-labeled neurons in the Vc and TG of either group. Neither the size distribution of SP-positive neurons nor their relative ratio in the TG differed between NV and CP mice at the ages of postnatal weeks 1 and 8. These findings indicate two putative origins for the emergent SP-immunoreaction in the superficial layer of the Vc of the CP mice: the surviving trigeminal neurons with SP against capsaicin treatment and/or intrinsic neurons/interneurons in the Vc without SP under normal conditions.
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Affiliation(s)
- Megumi Aita
- Division of Oral and Maxillofacial Surgery, Niigata University Graduate School of Medical and Dental Sciences, Japan
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Takemura M, Sugiyo S, Moritani M, Kobayashi M, Yonehara N. Mechanisms of orofacial pain control in the central nervous system. ACTA ACUST UNITED AC 2006; 69:79-100. [PMID: 16819148 DOI: 10.1679/aohc.69.79] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Recent advances in the study of pain have revealed somatotopic- and modality-dependent processing and the integration of nociceptive signals in the brain and spinal cord. This review summarizes the uniqueness of the trigeminal sensory nucleus (TSN) in structure and function as it relates to orofacial pain control. The oral nociceptive signal is primarily processed in the rostral TSN above the obex, the nucleus principalis (Vp), and the subnuclei oralis (SpVo) and interpolaris (SpVi), while secondarily processed in the subnucleus caudalis (SpVc). In contrast, the facial nociceptive signal is primarily processed in the SpVc. The neurons projecting to the thalamus are localized mostly in the Vp, moderately in the SpVi, and modestly in the ventrolateral SpVo and the SpVc. Orofacial sensory inputs are modulated in many different ways: by interneurons in the TSN proper, through reciprocal connection between the TSN and rostral ventromedial medulla, and by the cerebral cortex. A wide variety of neuroactive substances, including substance P, gamma-aminobutyric acid, serotonin and nitric oxide (NO) could be involved in the modulatory functions of these curcuits. The earliest expression of NO synthase (NOS) in the developing rat brain is observed in a discrete neuronal population in the SpVo at embryonic day 15. NOS expression in the SpVc is late at postnatal day 10. The neurons receiving intraoral signals are intimately related with the sensorimotor reflexive function through the SpVo. In summary, a better understanding of the trigeminal sensory system--which differs from the spinal system--will help to find potential therapeutic targets and lend to developing new analgesics for orofacial-specific pain with high efficacy and fewer side effects.
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Affiliation(s)
- Motohide Takemura
- Department of Oral Anatomy and Neurobiology, Osaka University Graduate School of Dentistry, Yamadaoka, Suita, Japan.
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Chattipakorn SC, Sigurdsson A, Light AR, Narhi M, Maixner W. Trigeminal c-Fos expression and behavioral responses to pulpal inflammation in ferrets. Pain 2002; 99:61-9. [PMID: 12237184 DOI: 10.1016/s0304-3959(02)00054-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Injury to peripheral dental tissues evokes dynamic alternations in central sensory pathways. We have previously reported that transient stimulation of the dental pulp with noxious heat evokes the induction of the immediate early gene product Fos in the transitional region between subnucleus interpolaris and caudalis (Vi/Vc) and subnucleus caudalis (Vc). A question arises as to whether similar changes occur in response to inflammation to the tooth pulp. In this study, the effects of pulpal inflammation produced by bacterial lipopolysaccharide (LPS) on face-grooming behavior and trigeminal Fos expression were examined. Face-grooming behaviors were recorded daily for 3 days pre- and 24, 48 and 72 h post- LPS or saline application. All animals were perfused 72 h post- LPS or saline application. Brainstems were processed for Fos-like immunoreactivity (Fos-LI). Teeth were processed for H&E staining. Histological examination of LPS-treated teeth revealed features of an acute pulpitis. Moreover, LPS-treated animals showed greater face-grooming activity (i.e. tongue protrusions) directed to the injured tooth than the sham-operated group. The number of Fos-positive neurons was greater in the trigeminal subnucleus caudalis (Vc) and the transitional regions (Vi/Vc) in LPS-treated animals compared with sham-operated animals, and greater in the deeper laminae than the superficial laminae of each trigeminal region. LPS treatment did not evoke Fos expression in the rostral trigeminal regions above Vi/Vc. These results demonstrate that LPS-induced pulpal inflammation results in significant alterations in the Vi/Vc and Vc, and such changes may underlie the observed nociceptive behavioral responses and may play an important role in producing a symptomatic pulpitis in humans.
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Takuma S. Effect of neonatal capsaicin treatment on neural activity in the medullary dorsal horn of neonatal rats evoked by electrical stimulation to the trigeminal afferents: an optical, electrophysiological, and quantitative study. Brain Res 2001; 906:1-12. [PMID: 11430856 DOI: 10.1016/s0006-8993(01)02448-9] [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: 11/20/2022]
Abstract
To elucidate which glutamate receptors, NMDA or non-NMDA, have the main role in synaptic transmission via unmyelinated afferents in the trigeminal subnucleus caudalis (the medullary dorsal horn), and to examine the early functional effects of neonatal capsaicin treatment to the subnucleus caudalis, optical recording, field potential recording, and quantitative study using electron micrographs were employed. A medulla oblongata isolated from a rat 5--7 days old was sectioned horizontally 400-microm thick or parasagittally and stained with a voltage-sensitive dye, RH482 or RH795. Single-pulse stimulation with high intensity to the trigeminal afferents evoked optical responses mainly in the subnucleus caudalis. The optical signals were composed of two phases, a fast component followed by a long-lasting component. The spatiotemporal properties of the optical signals were well correlated to those of the field potentials recorded simultaneously. The fast component was eliminated by 6-cyano-7-nitro-quinoxaline-2,3-dione (CNQX; 10 microM), while the long-lasting component was not. The latter increased in amplitude under a condition of low Mg(2+) but was significantly reduced by DL-2-amino-5-phosphonovaleric acid (AP5; 30 microM). Neonatal capsaicin treatment also reduced the long-lasting component markedly. In addition, the decreases in the ratio of unmyelinated axons to myelinated axons and in the ratio of unmyelinated axons to Schwann cell subunits of trigeminal nerve roots both showed significant differences (P<0.05, Student's t-test) between the control group and the neonatal capsaicin treatment group. This line of evidence indirectly suggests that synaptic transmission via unmyelinated afferents in the subnucleus caudalis is mediated substantially by NMDA glutamate receptors and documented that neonatal capsaicin treatment induced a functional alteration of the neural transmission in the subnucleus caudalis as well as a morphological alteration of primary afferents within several days after the treatment.
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MESH Headings
- 2-Amino-5-phosphonovalerate/pharmacology
- 6-Cyano-7-nitroquinoxaline-2,3-dione/pharmacology
- Action Potentials/drug effects
- Action Potentials/physiology
- Afferent Pathways/drug effects
- Afferent Pathways/growth & development
- Afferent Pathways/ultrastructure
- Animals
- Animals, Newborn/anatomy & histology
- Animals, Newborn/growth & development
- Animals, Newborn/metabolism
- Capsaicin/pharmacology
- Cell Count
- Electric Stimulation
- Electronic Data Processing
- Excitatory Amino Acid Antagonists/pharmacology
- Fluorescent Dyes/pharmacokinetics
- Magnesium Deficiency/physiopathology
- Medulla Oblongata/drug effects
- Medulla Oblongata/growth & development
- Medulla Oblongata/ultrastructure
- Microscopy, Electron
- Nerve Fibers/drug effects
- Nerve Fibers/metabolism
- Nerve Fibers/ultrastructure
- Nerve Fibers, Myelinated/ultrastructure
- Neurons, Afferent/drug effects
- Neurons, Afferent/metabolism
- Neurons, Afferent/ultrastructure
- Nociceptors/drug effects
- Nociceptors/metabolism
- Nociceptors/ultrastructure
- Rats
- Rats, Wistar
- Receptors, N-Methyl-D-Aspartate/drug effects
- Receptors, N-Methyl-D-Aspartate/metabolism
- Styrenes/pharmacokinetics
- Synaptic Transmission/drug effects
- Synaptic Transmission/physiology
- Trigeminal Caudal Nucleus/drug effects
- Trigeminal Caudal Nucleus/growth & development
- Trigeminal Caudal Nucleus/ultrastructure
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Affiliation(s)
- S Takuma
- Department of Dental Anesthesiology, Hokkaido University Graduate School of Dental Medicine, Sapporo 060-8586, Japan.
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