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Tian C, Yang Y, Li Y, Sun F, Qu J, Zha D. Expression and localization of α 2A-adrenergic receptor in the rat post-natal developing cochlea. Eur J Histochem 2023; 67:3748. [PMID: 37548252 PMCID: PMC10476538 DOI: 10.4081/ejh.2023.3748] [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: 04/11/2023] [Accepted: 07/22/2023] [Indexed: 08/08/2023] Open
Abstract
Lots of adrenergic receptors (ARs) are widely present across the auditory pathways and are positioned to affect auditory and vestibular functions. However, noradrenergic regulation in the cochlea has not been well characterized. In this study, a rat model of noise-induced hearing loss was developed to investigate the expression of α2A-adrenergic receptor (AR) after acoustic trauma, then, we investigated the expression of α2A-AR in the developing rat cochlea using immunofluorescence, qRT-PCR, and Western blotting. We found that the expression of α2A-AR significantly increased in rats exposed to noise compared with controls. Immunofluorescence analysis demonstrated that α2A-AR is localized on hair cells (HCs), spiral ganglion neurons (SGNs), and the stria vascularis (SV) in the postnatal developing cochlea from post-natal day (P) 0 to P28. Furthermore, we observed α2A-AR mRNA reached a maximum level at P14 and P28 when compared with P0, while no significant differences in α2A-AR protein levels at the various stages when compared with P0. This study provides direct evidence for the expression of α2A-AR in HCs, SGNs, and the SV of the cochlea, indicating that norepinephrine might play a vital role in hearing function within the cochlea through α2A-AR.
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Affiliation(s)
- Chaoyong Tian
- Department of Otolaryngology Head and Neck Surgery, Xijing Hospital, Air Force Medical University, Xi'an, Shannxi Province.
| | - Yang Yang
- Department of Otolaryngology Head and Neck Surgery, Xijing Hospital, Air Force Medical University, Xi'an, Shannxi Province.
| | - Yao Li
- Department of Otolaryngology Head and Neck Surgery, Xijing Hospital, Air Force Medical University, Xi'an, Shannxi Province.
| | - Fei Sun
- Department of Otolaryngology Head and Neck Surgery, Xijing Hospital, Air Force Medical University, Xi'an, Shannxi Province.
| | - Juan Qu
- Department of Otolaryngology Head and Neck Surgery, Xijing Hospital, Air Force Medical University, Xi'an, Shannxi Province.
| | - Dingjun Zha
- Department of Otolaryngology Head and Neck Surgery, Xijing Hospital, Air Force Medical University, Xi'an, Shannxi Province.
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2
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Tian C, Zha D. Sympathetic Nervous System Regulation of Auditory Function. Audiol Neurootol 2021; 27:93-103. [PMID: 34407531 DOI: 10.1159/000517452] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 05/26/2021] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The auditory system processes how we hear and understand sounds within the environment. It comprises both peripheral and central structures. Sympathetic nervous system projections are present throughout the auditory system. The function of sympathetic fibers in the cochlea has not been studied extensively due to the limited number of direct projections in the auditory system. Nevertheless, research on adrenergic and noradrenergic regulation of the cochlea and central auditory system is growing. With the rapid development of neuroscience, auditory central regulation is an extant topic of focus in research on hearing. SUMMARY As such, understanding sympathetic nervous system regulation of auditory function is a growing topic of interest. Herein, we review the distribution and putative physiological and pathological roles of sympathetic nervous system projections in hearing. Key Messages: In the peripheral auditory system, the sympathetic nervous system regulates cochlear blood flow, modulates cochlear efferent fibers, affects hair cells, and influences the habenula region. In central auditory pathways, norepinephrine is essential for plasticity in the auditory cortex and affects auditory cortex activity. In pathological states, the sympathetic nervous system is associated with many hearing disorders. The mechanisms and pathways of sympathetic nervous system modulation of auditory function is still valuable for us to research and discuss.
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Affiliation(s)
- Chaoyong Tian
- Department of Otolaryngology Head and Neck Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Dingjun Zha
- Department of Otolaryngology Head and Neck Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, China
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3
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Wung D, Goderie T, van Wier MF, Stam M, Kramer SE. Association of beta blocker use and hearing ability in adults: a cross-sectional study. Int J Audiol 2021; 61:102-107. [PMID: 34057380 DOI: 10.1080/14992027.2021.1915508] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
OBJECTIVES To investigate the potential association between beta blocker use and hearing ability in adults and to discern whether this effect is dose-dependent. DESIGN Cross-sectional analyses. Multiple linear regression was performed with hearing ability as the dependent variable and beta blocker use as the independent variable. The independent variable was classified into three dose categories for secondary analysis. Adjustments were made for age, gender, educational level, and tobacco smoking status. STUDY SAMPLE 1636 adults, 75 of whom reported being on beta blockers, from the internet-based Netherlands Longitudinal Study on Hearing (NL-SH). RESULTS No significant association was found between beta blocker use and hearing ability in noise. In the adjusted regressions, beta blocker use changed the speech reception threshold in noise (SRT) by -0.04 dB signal-to-noise ratio (SNR) (95%CI [-0.67 to 0.58], p = 0.890). Medium dose beta blocker use changed SRT by -0.42 dB SNR (95%CI [-1.38 to 0.71], p = 0.433), while a high dose changed it by -0.26 dB SNR (95%CI [-1.74 to 1.4], p = 0.767). CONCLUSIONS No evidence was found for beta blocker-induced changes in hearing ability. Future studies on this topic should favour case-control and cohort study designs, while focussing on a hypertensive population to minimise confounding by indication.
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Affiliation(s)
- Deanna Wung
- Ecole des Hautes Etudes en Santé Publique, Rennes, France
| | - Thadé Goderie
- Department of Otolaryngology-Head and Neck Surgery, Ear and Hearing, Amsterdam Public Health Research Institute, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Marieke F van Wier
- Department of Otolaryngology-Head and Neck Surgery, Ear and Hearing, Amsterdam Public Health Research Institute, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Mariska Stam
- Department of Otolaryngology-Head and Neck Surgery, Ear and Hearing, Amsterdam Public Health Research Institute, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.,National Health Care Institute, Diemen, The Netherlands
| | - Sophia E Kramer
- Department of Otolaryngology-Head and Neck Surgery, Ear and Hearing, Amsterdam Public Health Research Institute, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
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4
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Kitcher SR, Pederson AM, Weisz CJC. Diverse identities and sites of action of cochlear neurotransmitters. Hear Res 2021; 419:108278. [PMID: 34108087 DOI: 10.1016/j.heares.2021.108278] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 04/30/2021] [Accepted: 05/18/2021] [Indexed: 11/18/2022]
Abstract
Accurate encoding of acoustic stimuli requires temporally precise responses to sound integrated with cellular mechanisms that encode the complexity of stimuli over varying timescales and orders of magnitude of intensity. Sound in mammals is initially encoded in the cochlea, the peripheral hearing organ, which contains functionally specialized cells (including hair cells, afferent and efferent neurons, and a multitude of supporting cells) to allow faithful acoustic perception. To accomplish the demanding physiological requirements of hearing, the cochlea has developed synaptic arrangements that operate over different timescales, with varied strengths, and with the ability to adjust function in dynamic hearing conditions. Multiple neurotransmitters interact to support the precision and complexity of hearing. Here, we review the location of release, action, and function of neurotransmitters in the mammalian cochlea with an emphasis on recent work describing the complexity of signaling.
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Affiliation(s)
- Siân R Kitcher
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, United States
| | - Alia M Pederson
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, United States
| | - Catherine J C Weisz
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, United States.
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5
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Wei W, Shi X, Xiong W, He L, Du ZD, Qu T, Qi Y, Gong SS, Liu K, Ma X. RNA-seq Profiling and Co-expression Network Analysis of Long Noncoding RNAs and mRNAs Reveal Novel Pathogenesis of Noise-induced Hidden Hearing Loss. Neuroscience 2020; 434:120-135. [PMID: 32201268 DOI: 10.1016/j.neuroscience.2020.03.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Revised: 02/25/2020] [Accepted: 03/15/2020] [Indexed: 12/16/2022]
Abstract
Noise-induced hidden hearing loss (NIHHL), one of the family of conditions described as noise-induced hearing loss (NIHL), is characterized by synaptopathy following moderate noise exposure that causes only temporary threshold elevation. Long noncoding RNAs (lncRNAs) mediate several essential regulatory functions in a wide range of biological processes and diseases, but their roles in NIHHL remain largely unknown. In order to determine the potential roles of these lncRNAs in the pathogenesis of NIHHL, we first evaluated their expression in NIHHL mice model and mapped possible regulatory functions and targets using RNA-sequencing (RNA-seq). In total, we identified 133 lncRNAs and 522 mRNAs that were significantly dysregulated in the NIHHL model. Gene Ontology (GO) showed that these lncRNAs were involved in multiple cell components and systems including synapses and the nervous and sensory systems. In addition, a lncRNA-mRNA network was constructed to identify core regulatory lncRNAs and transcription factors. KEGG analysis was also used to identify the potential pathways being affected in NIHHL. These analyses allowed us to identify the guanine nucleotide binding protein alpha stimulating (GNAS) gene as a key transcription factor and the adrenergic signaling pathway as a key pathway in the regulation of NIHHL pathogenesis. Our study is the first, to our knowledge, to isolate a lncRNA mediated regulatory pathway associated with NIHHL pathogenesis; these observations may provide fresh insight into the pathogenesis of NIHHL and may pave the way for therapeutic intervention in the future.
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Affiliation(s)
- Wei Wei
- Department of Otology, Shengjing Hospital, China Medical University, Shenyang 110004, China
| | - Xi Shi
- Department of Otolaryngology-Head and Neck, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China; The Institute of Audiology and Speech Science of Xuzhou Medical College, Xuzhou 221004, China
| | - Wei Xiong
- Department of Otolaryngology-Head and Neck, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
| | - Lu He
- Department of Otolaryngology-Head and Neck, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
| | - Zheng-De Du
- Department of Otolaryngology-Head and Neck, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
| | - Tengfei Qu
- Department of Otolaryngology-Head and Neck, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
| | - Yue Qi
- Department of Otolaryngology-Head and Neck, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
| | - Shu-Sheng Gong
- Department of Otolaryngology-Head and Neck, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
| | - Ke Liu
- Department of Otolaryngology-Head and Neck, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China.
| | - Xiulan Ma
- Department of Otology, Shengjing Hospital, China Medical University, Shenyang 110004, China.
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6
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Al-Ghamdi BS, Rohra DK, Abuharb GAI, Alkofide HA, AlRuwaili NS, Shoukri MM, Cahusac PMB. Use of beta blockers is associated with hearing loss. Int J Audiol 2017; 57:213-220. [DOI: 10.1080/14992027.2017.1405162] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Bandar Saeed Al-Ghamdi
- Department of Cardiology, Heart Centre, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia,
- Department of Medicine, Alfaisal University, Riyadh, Saudi Arabia,
| | - Dileep Kumar Rohra
- Department of Pharmacology, College of Medicine, Alfaisal University, Riyadh, Saudi Arabia,
| | - Gheid Ali Ibrahim Abuharb
- Clinical Audiology, Department of Otolaryngology, Head & Neck Surgery and Communication Sciences, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia,
| | - Hala Abdulrahman Alkofide
- Clinical Audiology, Department of Otolaryngology, Head & Neck Surgery and Communication Sciences, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia,
| | - Nadiah Salem AlRuwaili
- Department of Cardiology, Heart Centre, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia,
| | - Mohamed M. Shoukri
- Department of Cell Biology and the National Biotechnology Centre, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia, and
| | - Peter M. B. Cahusac
- Department of Pharmacology, College of Medicine, Alfaisal University, Riyadh, Saudi Arabia,
- Department of Comparative Medicine, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
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7
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Wenner MI, Maker GL, Dawson LF, Drummond PD, Mullaney I. The potential of metabolomic analysis techniques for the characterisation of α1-adrenergic receptors in cultured N1E-115 mouse neuroblastoma cells. Cytotechnology 2015; 68:1561-75. [PMID: 26408527 DOI: 10.1007/s10616-015-9915-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 09/03/2015] [Indexed: 10/23/2022] Open
Abstract
Several studies of neuropathic pain have linked abnormal adrenergic signalling to the development and maintenance of pain, although the mechanisms underlying this are not yet fully understood. Metabolomic analysis is a technique that can be used to give a snapshot of biochemical status, and can aid in the identification of the mechanisms behind pathological changes identified in cells, tissues and biological fluids. This study aimed to use gas chromatography-mass spectrometry-based metabolomic profiling in combination with reverse transcriptase-polymerase chain reaction and immunocytochemistry to identify functional α1-adrenergic receptors on cultured N1E-115 mouse neuroblastoma cells. The study was able to confirm the presence of mRNA for the α1D subtype, as well as protein expression of the α1-adrenergic receptor. Furthermore, metabolomic data revealed changes to the metabolite profile of cells when exposed to adrenergic pharmacological intervention. Agonist treatment with phenylephrine hydrochloride (10 µM) resulted in altered levels of several metabolites including myo-inositol, glucose, fructose, alanine, leucine, phenylalanine, valine, and n-acetylglutamic acid. Many of the changes observed in N1E-115 cells by agonist treatment were modulated by additional antagonist treatment (prazosin hydrochloride, 100 µM). A number of these changes reflected what is known about the biochemistry of α1-adrenergic receptor activation. This preliminary study therefore demonstrates the potential of metabolomic profiling to confirm the presence of functional receptors on cultured cells.
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Affiliation(s)
- Maria I Wenner
- School of Veterinary and Life Sciences, Murdoch University, Perth, WA, Australia
| | - Garth L Maker
- School of Veterinary and Life Sciences, Murdoch University, Perth, WA, Australia. .,Metabolomics Australia, Murdoch University, Perth, WA, Australia. .,Separation Science and Metabolomics Laboratory, Murdoch University, Perth, WA, Australia.
| | - Linda F Dawson
- School of Veterinary and Life Sciences, Murdoch University, Perth, WA, Australia.,School of Psychology and Exercise Science, Murdoch University, Perth, WA, Australia
| | - Peter D Drummond
- School of Psychology and Exercise Science, Murdoch University, Perth, WA, Australia
| | - Ian Mullaney
- School of Veterinary and Life Sciences, Murdoch University, Perth, WA, Australia
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8
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Masuda M, Kanzaki J. Cause of idiopathic sudden sensorineural hearing loss: The stress response theory. World J Otorhinolaryngol 2013; 3:42-57. [DOI: 10.5319/wjo.v3.i3.42] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2013] [Revised: 06/14/2013] [Accepted: 07/25/2013] [Indexed: 02/06/2023] Open
Abstract
The stress response theory is a relatively new concept about the cause of idiopathic sudden sensorineural hearing loss (ISHL). A number of possible etiologies have been proposed in the literature, as discussed in this paper, but each proposed etiology has been both supported and refuted in the literature. However, the stress response theory can integrate hypotheses that have been advocated so far. The word “stress” refers to a constellation of physical and psychological stimuli including systemic viral and bacterial illness, systemic inflammatory disorders, and physical, mental or metabolic stress. Numerous studies have demonstrated adverse effects of systemic stress on health. Stress causes changes in the immune system and cytokine network through activation of the hypothalamus-pituitary-adrenal axis and the sympathetic nervous system. Several types of catecholamine and cytokine receptors are in the cochlea cells other than capillary cells, and then they can respond to systemic stressors. However, there are few studies examining how systemic stress is associated with cochlear dysfunction. The stress response theory addresses this question. In the theory, a variety of stressors and risk factors contribute to the onset of ISHL in varying degrees. The lateral wall of the cochlea has very unique responses to systemic stressors. It plays a critical role in causing ISHL. Systemic stressors converge at the lateral wall and trigger pathological activation of nuclear factor κ-light-chain-enhancer of activated B cells, a transcriptional factor known as a stress sensor. This activation enhances local expression of genes associated with immune and inflammatory system, resulting in cochlear dysfunction. We review the original stress response theory advocated by Adams et al and the integrative stress response theory that integrates our knowledge about the etiologies of ISHL so far.
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9
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Cai J, Li J, Mao Y, Bai X, Xu L, Wang H. Immunohistochemical Localization of α2-Adrenergic Receptors in the Neonatal Rat Cochlea and the Vestibular Labyrinth. J Mol Neurosci 2013; 51:1010-20. [DOI: 10.1007/s12031-013-0089-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2013] [Accepted: 07/29/2013] [Indexed: 12/17/2022]
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10
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Degerman E, Rauch U, Lindberg S, Caye-Thomasen P, Hultgårdh A, Magnusson M. Expression of insulin signalling components in the sensory epithelium of the human saccule. Cell Tissue Res 2013; 352:469-78. [DOI: 10.1007/s00441-013-1614-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2012] [Accepted: 03/08/2013] [Indexed: 12/24/2022]
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11
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Kanzaki J, Masuda M. Correlation between stress and acute sensorineural hearing loss: stress and sudden deafness. ACTA ACUST UNITED AC 2013. [DOI: 10.4295/audiology.56.137] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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12
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Kitahara T, Horii A, Uno A, Imai T, Okazaki S, Kamakura T, Takimoto Y, Inohara H. Changes in beta-2 adrenergic receptor and AMP-activated protein kinase alpha-2 subunit in the rat vestibular nerve after labyrinthectomy. Neurosci Res 2012; 72:221-6. [DOI: 10.1016/j.neures.2011.11.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2011] [Revised: 11/18/2011] [Accepted: 11/21/2011] [Indexed: 12/17/2022]
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13
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Dawson LF, Phillips JK, Finch PM, Inglis JJ, Drummond PD. Expression of α1-adrenoceptors on peripheral nociceptive neurons. Neuroscience 2010; 175:300-14. [PMID: 21182905 DOI: 10.1016/j.neuroscience.2010.11.064] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 11/26/2010] [Accepted: 11/30/2010] [Indexed: 01/06/2023]
Abstract
The purpose of this study was to determine whether α(1)-adrenoceptors are expressed on primary nociceptive afferents that innervate healthy skin. Skin and dorsal root ganglia were collected from adult male Wistar rats and assessed using fluorescence immunohistochemistry with antibodies directed against α(1)-adrenoceptors alone or in combination with specific labels including myelin basic protein and neurofilament 200 (markers of myelinated nerve fibres), protein gene product 9.5 (a pan-neuronal marker), tyrosine hydroxylase (sympathetic neurons), isolectin B(4) (IB(4): non-peptidergic sensory neurons), calcitonin gene related peptide (CGRP) and transient receptor potential vanilloid receptor 1 (TRPV1) (peptidergic sensory neurons). Double labelling in dorsal root ganglia confirmed the expression of α(1)-adrenoceptors within sub-populations of CGRP, IB(4) and TRPV1 immunoreactive neurons. Myelinated and unmyelinated sensory nerve fibres in the skin expressed α(1)-adrenoceptors whereas sympathetic nerve fibres did not. The expression of α(1)-adrenoceptors on C- and A-delta nociceptive afferent fibres provides a histochemical substrate for direct excitation of these fibres by adrenergic agonists. This may help to explain the mechanism of sensory-sympathetic coupling that sometimes develops on surviving primary nociceptive afferents in neuropathic pain states.
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Affiliation(s)
- L F Dawson
- Faculty of Health Sciences, Murdoch University, Perth, Western Australia
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14
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Zhang Y, Kolli T, Hivley R, Jaber L, Zhao FI, Yan J, Herness S. Characterization of the expression pattern of adrenergic receptors in rat taste buds. Neuroscience 2010; 169:1421-37. [PMID: 20478367 DOI: 10.1016/j.neuroscience.2010.05.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Revised: 05/03/2010] [Accepted: 05/11/2010] [Indexed: 12/01/2022]
Abstract
Taste buds signal the presence of chemical stimuli in the oral cavity to the central nervous system using both early transduction mechanisms, which allow single cells to be depolarized via receptor-mediated signaling pathways, and late transduction mechanisms, which involve extensive cell-to-cell communication among the cells in the bud. The latter mechanisms, which involve a large number of neurotransmitters and neuropeptides, are less well understood. Among neurotransmitters, multiple lines of evidence suggest that norepinephrine plays a yet unknown role in the taste bud. This study investigated the expression pattern of adrenergic receptors in the rat posterior taste bud. Expression of alpha1A, alpha1B, alpha1D, alpha2A, alpha2B, alpha2C, beta1, and the beta2 adrenoceptor subtypes was observed in taste buds using RT-PCR and immunocytochemical techniques. Taste buds also expressed the biosynthetic enzyme for norepinephrine, dopamine beta-hydroxylase (DbetaH), as well as the norepinephrine transporter. Further, expression of the epinephrine synthetic enzyme, phenylethanolamine N-methyltransferase (PNMT), was observed suggesting a possible role for this transmitter in the bud. Phenotyping adrenoceptor expression patterns with double labeling experiments to gustducin, synaptosomal-associated protein 25 (SNAP-25), and neural cell adhesion molecule (NCAM) suggests they are prominently expressed in subsets of cells known to express taste receptor molecules but segregated from cells known to have synapses with the afferent nerve fiber. Alpha and beta adrenoceptors co-express with one another in unique patterns as observed with immunocytochemistry and single cell reverse transcription polymerase chain reaction (RT-PCR). These data suggest that single cells express multiple adrenergic receptors and that adrenergic signaling may be particularly important in bitter, sweet, and umami taste qualities. In summary, adrenergic signaling in the taste bud occurs through complex pathways that include presynaptic and postsynaptic receptors and likely play modulatory roles in processing of gustatory information similar to other peripheral sensory systems such as the retina, cochlea, and olfactory bulb.
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Affiliation(s)
- Y Zhang
- Department of Physiology and Pathophysiology, Key Laboratory of Environment and Genes Related to Diseases, Ministry of Education, School of Medicine, Xi'an Jiaotong University, 76# West Yanta Road, Xi'an 710061, PR China
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