1
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Characterization of sensory neuronal subtypes innervating mouse tongue. PLoS One 2018; 13:e0207069. [PMID: 30408082 PMCID: PMC6224080 DOI: 10.1371/journal.pone.0207069] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 10/24/2018] [Indexed: 12/14/2022] Open
Abstract
The tongue is uniquely exposed to water-soluble environmental chemicals that may lead to injury or tumorigenesis. However, comparatively little research has focused on the molecular and functional organization of trigeminal ganglia (TG) afferent neurons innervating the tongue. The current study identified and characterized lingual sensory neurons based on a neuronal subtype classification previously characterized in the dorsal root ganglion (DRG) neurons. We employed immunohistochemistry on transgenic reporter mouse lines as well as single-cell PCR of known markers of neuronal subtypes to characterize neuronal subtypes innervating the tongue. Markers expressed in retrogradely labeled TG neurons were evaluated for the proportion of neurons expressing each marker, intensity of expression, and overlapping genes. We found that tongue-innervating sensory neurons primarily expressed CGRP, TRPV1, TrkC, 5HT3A and Parvalbumin. These markers correspond to peptidergic and a subgroup of non-peptidergic C-nociceptors, peptidergic A nociceptors, proprioceptors and myelinated low-threshold mechanoreceptors (LTMRs). Interestingly, as reported previously, we also found several differences between TG and DRG neurons indicating the need for single-cell sequencing of neuronal types based on tissue type within all TG as well as DRG neurons.
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2
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Somatosensory innervation of the oral mucosa of adult and aging mice. Sci Rep 2018; 8:9975. [PMID: 29967482 PMCID: PMC6028454 DOI: 10.1038/s41598-018-28195-2] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Accepted: 06/18/2018] [Indexed: 02/06/2023] Open
Abstract
Oral mechanoreception is implicated in fundamental functions including speech, food intake and swallowing; yet, the neuroanatomical substrates that encode mechanical stimuli are not well understood. Tactile perception is initiated by intricate mechanosensitive machinery involving dedicated cells and neurons. This signal transduction setup is coupled with the topology and mechanical properties of surrounding epithelium, thereby providing a sensitive and accurate system to detect stress fluctuations from the external environment. We mapped the distribution of anatomically distinct neuronal endings in mouse oral cavity using transgenic reporters, molecular markers and quantitative histomorphometry. We found that the tongue is equipped with an array of putative mechanoreceptors that express the principal mechanosensory channel Piezo2, including end bulbs of Krause innervating individual filiform papillae and a novel class of neuronal fibers innervating the epithelium surrounding taste buds. The hard palate and gums are densely populated with three classes of sensory afferents organized in discrete patterns including Merkel cell-neurite complexes, Meissner’s corpuscles and glomerular corpuscles. In aged mice, we find that palatal Merkel cells reduce in number at key time-points that correlate with impaired oral abilities, such as swallowing and mastication. Collectively, this work identifies the mechanosensory architecture of oral tissues involved in feeding.
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3
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Moayedi Y, Duenas-Bianchi LF, Lumpkin EA. Somatosensory innervation of the oral mucosa of adult and aging mice. Sci Rep 2018. [PMID: 29967482 DOI: 10.1038/s41598‐018‐28195‐2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Oral mechanoreception is implicated in fundamental functions including speech, food intake and swallowing; yet, the neuroanatomical substrates that encode mechanical stimuli are not well understood. Tactile perception is initiated by intricate mechanosensitive machinery involving dedicated cells and neurons. This signal transduction setup is coupled with the topology and mechanical properties of surrounding epithelium, thereby providing a sensitive and accurate system to detect stress fluctuations from the external environment. We mapped the distribution of anatomically distinct neuronal endings in mouse oral cavity using transgenic reporters, molecular markers and quantitative histomorphometry. We found that the tongue is equipped with an array of putative mechanoreceptors that express the principal mechanosensory channel Piezo2, including end bulbs of Krause innervating individual filiform papillae and a novel class of neuronal fibers innervating the epithelium surrounding taste buds. The hard palate and gums are densely populated with three classes of sensory afferents organized in discrete patterns including Merkel cell-neurite complexes, Meissner's corpuscles and glomerular corpuscles. In aged mice, we find that palatal Merkel cells reduce in number at key time-points that correlate with impaired oral abilities, such as swallowing and mastication. Collectively, this work identifies the mechanosensory architecture of oral tissues involved in feeding.
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Affiliation(s)
- Yalda Moayedi
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, 10032, USA
| | - Lucia F Duenas-Bianchi
- SPURS Biomedical Research Program, Department of Physiology and Cellular Biophysics, Columbia University Medical Center, New York, NY, 10032, USA
| | - Ellen A Lumpkin
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, 10032, USA. .,Department of Dermatology, Columbia University, New York, NY, 10032, USA. .,Program in Neurobiology and Behavior, Columbia University, New York, NY, 10032, USA.
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4
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Budzik KA, Żuwała K, Buchholz DR. Taste organ growth and development in the direct developing frogEleutherodactylus coqui(Lissamphibia: Eleutherodactylidae). ACTA ZOOL-STOCKHOLM 2015. [DOI: 10.1111/azo.12137] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Karolina A. Budzik
- Department of Comparative Anatomy; Jagiellonian University; Gronostajowa 9 30-387 Kraków Poland
| | - Krystyna Żuwała
- Department of Comparative Anatomy; Jagiellonian University; Gronostajowa 9 30-387 Kraków Poland
| | - Daniel R. Buchholz
- Department of Biological Sciences; University of Cincinnati; 711A Rieveschl Hall 312 Clifton Ct. Cincinnati OH 45221 USA
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Jackson R, Braubach OR, Bilkey J, Zhang J, Akimenko M, Fine A, Croll RP, Jonz MG. Expression of
sall4
in taste buds of zebrafish. Dev Neurobiol 2013; 73:543-58. [DOI: 10.1002/dneu.22079] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 02/22/2013] [Accepted: 02/25/2013] [Indexed: 11/11/2022]
Affiliation(s)
- Robyn Jackson
- Department of BiologyUniversity of OttawaOttawa ON CanadaK1N 6N5
| | - Oliver R. Braubach
- Department of Physiology and BiophysicsDalhousie UniversityHalifax NS CanadaB3H 1X5
- Center for Functional ConnectomicsKorea Institute of Science and TechnologySeoul Korea
| | - Jessica Bilkey
- Department of BiologyUniversity of OttawaOttawa ON CanadaK1N 6N5
| | - Jing Zhang
- Department of BiologyUniversity of OttawaOttawa ON CanadaK1N 6N5
| | | | - Alan Fine
- Department of Physiology and BiophysicsDalhousie UniversityHalifax NS CanadaB3H 1X5
| | - Roger P. Croll
- Department of Physiology and BiophysicsDalhousie UniversityHalifax NS CanadaB3H 1X5
| | - Michael G. Jonz
- Department of BiologyUniversity of OttawaOttawa ON CanadaK1N 6N5
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6
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Zachar PC, Jonz MG. Confocal imaging of Merkel-like basal cells in the taste buds of zebrafish. Acta Histochem 2012; 114:101-15. [PMID: 21477848 DOI: 10.1016/j.acthis.2011.03.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Revised: 03/07/2011] [Accepted: 03/09/2011] [Indexed: 10/18/2022]
Abstract
The oropharyngeal cavity in fish supports a range of sensory modalities, including detection of chemical and mechanical stimuli. Taste buds are found throughout this tissue and may participate in both processes. We used confocal microscopy and immunohistochemistry to characterize the morphology of Merkel-like cells and their association with other cell types and nerve fibers of the taste bud in the vertebrate model, the zebrafish. In addition, we document procedures for the observation of these structures in whole-tissue preparations from larvae and adults using zebrafish-specific and monoclonal antibodies. A single microvillus Merkel-like cell was found in each taste bud regardless of age or location. Merkel-like cells were neurosecretory, as indicated by labelling with the styryl dye, FM1-43, and the synaptic vesicle marker, SV2. Merkel-like cells were associated with SV2- and calretinin-positive taste receptor cells, received innervation from discoid aggregations of nerve fibers, and retained serotonin-filled synaptic vesicles oriented within the cytoplasm toward adjacent innervation. Moreover, a ring-like formation of nerve endings was identified with the neuronal marker, zn-12 that circumscribed the taste receptor area, surrounding calretinin-immunoreactive taste cell microvilli, and appeared to associate with the nerve plexus adjacent to Merkel-like cells. We suggest that these nerve fibers are somatosensory, perhaps associated with mechanoreception or the common chemical sense.
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7
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Barreiro-Iglesias A, Villar-Cerviño V, Villar-Cheda B, Anadón R, Rodicio MC. Neurochemical characterization of sea lamprey taste buds and afferent gustatory fibers: presence of serotonin, calretinin, and CGRP immunoreactivity in taste bud bi-ciliated cells of the earliest vertebrates. J Comp Neurol 2008; 511:438-53. [PMID: 18831528 DOI: 10.1002/cne.21844] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Neuroactive substances such as serotonin and other monoamines have been suggested to be involved in the transmission of gustatory signals from taste bud cells to afferent fibers. Lampreys are the earliest vertebrates that possess taste buds, although these differ in structure from taste buds in jawed vertebrates, and their neurochemistry remains unknown. We used immunofluorescence methods with antibodies raised against serotonin, tyrosine hydroxylase (TH), gamma-aminobutyric acid (GABA), glutamate, calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY), calretinin, and acetylated alpha-tubulin to characterize the neurochemistry and innervation of taste buds in the sea lamprey, Petromyzon marinus L. For localization of proliferative cells in taste buds we used bromodeoxyuridine labeling and proliferating cell nuclear antigen immunohistochemistry. Results with both markers indicate that proliferating cells are restricted to a few basal cells and that almost all cells in taste buds are nonproliferating. A large number of serotonin-, calretinin-, and CGRP-immunoreactive bi-ciliated cells were revealed in lamprey taste buds. This suggests that serotonin participates in the transmission of gustatory signals and indicates that this substance appeared early on in vertebrate evolution. The basal surface of the bi-ciliated taste bud cells was contacted by tubulin-immunoreactive fibers. Some of the fibers surrounding the taste bud were calretinin immunoreactive. Lamprey taste bud cells or afferent fibers did not exhibit TH, GABA, glutamate, or NPY immunoreactivity, which suggests that expression of these substances evolved in taste buds of some gnathostomes lines after the separation of gnathostomes and lampreys.
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Affiliation(s)
- Antón Barreiro-Iglesias
- Department of Cell Biology and Ecology, Faculty of Biology, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain
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8
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Abstract
Merkel cells are rare epidermal cells whose function in the skin is still debated. These cells localize to highly touch-sensitive areas of vertebrate epithelia, including palatine ridges, touch domes and finger tips. In most cases, Merkel cells complex with somatosensory afferents to form slowly adapting touch receptors; it is unclear, however, whether mechanosensory transduction occurs in the Merkel cell, the somatosensory afferent or both. Classic anatomical results suggests that Merkel cells are sensory cells that transduce mechanical stimuli and then communicate with sensory afferents via neurotransmission. This model is supported by recent molecular, immunohistochemical and physiological studies of Merkel cells in vitro and in intact tissues. For example, Merkel cells express essential components of presynaptic machinery, including molecules required for release of the excitatory neurotransmitter glutamate. Moreover, Merkel cells in vitro and in vivo are activated by mechanical stimuli, including hypotonic-induced cell swelling. Although these findings support the hypothesis that Merkel cells are sensory receptor cells, a definitive demonstration that Merkel cells are necessary and sufficient to transduce touch awaits future studies.
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Affiliation(s)
- Henry Haeberle
- Neuroscience Graduate Program, UCSF, Baylor College of Medicine, Houston TX 77030
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9
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Oakley B, Witt M. Building sensory receptors on the tongue. ACTA ACUST UNITED AC 2005; 33:631-46. [PMID: 16217619 DOI: 10.1007/s11068-005-3332-0] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2005] [Accepted: 04/05/2005] [Indexed: 12/01/2022]
Abstract
Neurotrophins, neurotrophin receptors and sensory neurons are required for the development of lingual sense organs. For example, neurotrophin 3 sustains lingual somatosensory neurons. In the traditional view, sensory axons will terminate where neurotrophin expression is most pronounced. Yet, lingual somatosensory axons characteristically terminate in each filiform papilla and in each somatosensory prominence within a cluster of cells expressing the p75 neurotrophin receptor (p75NTR), rather than terminating among the adjacent cells that secrete neurotrophin 3. The p75NTR on special specialized clusters of epithelial cells may promote axonal arborization in vivo since its over-expression by fibroblasts enhances neurite outgrowth from overlying somatosensory neurons in vitro. Two classical observations have implicated gustatory neurons in the development and maintenance of mammalian taste buds--the early arrival times of embryonic innervation and the loss of taste buds after their denervation in adults. In the modern era more than a dozen experimental studies have used early denervation or neurotrophin gene mutations to evaluate mammalian gustatory organ development. Necessary for taste organ development, brain-derived neurotrophic factor sustains developing gustatory neurons. The cardinal conclusion is readily summarized: taste buds in the palate and tongue are induced by innervation. Taste buds are unstable: the death and birth of taste receptor cells relentlessly remodels synaptic connections. As receptor cells turn over, the sensory code for taste quality is probably stabilized by selective synapse formation between each type of gustatory axon and its matching taste receptor cell. We anticipate important new discoveries of molecular interactions among the epithelium, the underlying mesenchyme and gustatory innervation that build the gustatory papillae, their specialized epithelial cells, and the resulting taste buds.
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Affiliation(s)
- Bruce Oakley
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109, USA
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10
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Abstract
Taste buds are sensory end organs that detect chemical substances occurring in foodstuffs and relay the relative information to the brain. The mechanisms by which the chemical stimuli are converted into biological signals represent a central issue in taste research. Our understanding of how taste buds accomplish this operation relies on the detailed knowledge of the biological properties of taste bud cells-the taste cells-and of the functional processes occurring in these cells during chemostimulation. The amphibian Necturus maculosus (mudpuppy) has proven to be a very useful model for studying basic cellular processes of vertebrate taste reception, some of which are still awaiting to be explored in mammals. The main advantages offered by Necturus are the large size of its taste cells and the relative accessibility of its taste buds, which can therefore be handled easily for experimental manipulations. In this review, I summarize the functional properties of Necturus taste cells studied with electrophysiological techniques (intracellular recordings and patch-clamp recordings). My focus is on ion channels in taste cells and on their role in signal transduction, as well as on the functional relationships among the cells inside Necturus taste buds. This information has revealed to be well suited to outline some of the general physiological processes occurring during taste reception in vertebrates, including mammals, and may represent a useful framework for understanding how taste buds work.
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Affiliation(s)
- Albertino Bigiani
- Dipartimento di Scienze Biomediche, Sezione di Fisiologia, Università di Modena e Reggio Emilia, via Campi 287, Italy.
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