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Godfrey DA, Chen K, O'Toole TR, Mustapha AI. Amino acid and acetylcholine chemistry in the central auditory system of young, middle-aged and old rats. Hear Res 2017; 350:173-188. [DOI: 10.1016/j.heares.2017.05.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 04/24/2017] [Accepted: 05/03/2017] [Indexed: 02/04/2023]
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Liu P, Gupta N, Jing Y, Collie ND, Zhang H, Smith PF. Further studies of the effects of aging on arginine metabolites in the rat vestibular nucleus and cerebellum. Neuroscience 2017; 348:273-287. [PMID: 28238850 DOI: 10.1016/j.neuroscience.2017.02.033] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 02/16/2017] [Accepted: 02/16/2017] [Indexed: 12/21/2022]
Abstract
Some studies have demonstrated that aging is associated with impaired vestibular reflexes, especially otolithic reflexes, resulting in postural instability. However, the neurochemical basis of these age-related changes is still poorly understood. The l-arginine metabolic system has been implicated in changes in the brain associated with aging. In the current study, we examined the levels of l-arginine and its metabolizing enzymes and downstream metabolites in the vestibular nucleus complex (VNC) and cerebellum (CE) of rats with and without behavioral testing which were young (4months old), middle-aged (12months old) or aged (24months old). We found that aging was associated with lower nitric oxide synthase activity in the CE of animals with testing and increased arginase in the VNC and CE of animals with testing. l-citrulline and l-ornithine were lower in the VNC of aged animals irrespective of testing, while l-arginine and l-citrulline were lower in the CE with and without testing, respectively. In the VNC and CE, aging was associated with lower levels of glutamate in the VNC, irrespective of testing. In the VNC it was associated with higher levels of agmatine and putrescine, irrespective of testing. In the CE, aging was associated with higher levels of putrescine in animals without testing and with higher levels of spermine in animals with testing, and spermidine, irrespective of testing. Multivariate analyses indicated significant predictive relationships between the different variables, and there were correlations between some of the neurochemical variables and behavioral measurements. Cluster analyses revealed that aging altered the relationships between l-arginine and its metabolites. The results of this study demonstrate that there are major changes occurring in l-arginine metabolism in the VNC and CE as a result of age, as well as behavioral activity.
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Affiliation(s)
- P Liu
- Dept. of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand; Brain Health Research Centre, University of Otago, Dunedin, New Zealand; The Brain Research New Zealand Centre of Research Excellence, New Zealand.
| | - N Gupta
- Dept. of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand; Brain Health Research Centre, University of Otago, Dunedin, New Zealand
| | - Y Jing
- Dept. of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand; Brain Health Research Centre, University of Otago, Dunedin, New Zealand
| | - N D Collie
- Dept. of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand; Brain Health Research Centre, University of Otago, Dunedin, New Zealand
| | - H Zhang
- School of Pharmacy, University of Otago, Dunedin, New Zealand; Brain Health Research Centre, University of Otago, Dunedin, New Zealand
| | - P F Smith
- Dept. of Pharmacology and Toxicology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand; Brain Health Research Centre, University of Otago, Dunedin, New Zealand; The Brain Research New Zealand Centre of Research Excellence, New Zealand; The Eisdell Moore Centre, University of Auckland, New Zealand
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Godfrey DA, Chen K, Godfrey MA, Lee AC, Crass SP, Shipp D, Simo H, Robinson KT. Cochlear ablation effects on amino acid levels in the chinchilla cochlear nucleus. Neuroscience 2015; 297:137-59. [PMID: 25839146 DOI: 10.1016/j.neuroscience.2015.03.055] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 03/06/2015] [Accepted: 03/24/2015] [Indexed: 10/23/2022]
Abstract
Inner ear damage can lead to hearing disorders, including tinnitus, hyperacusis, and hearing loss. We measured the effects of severe inner ear damage, produced by cochlear ablation, on the levels and distributions of amino acids in the first brain center of the auditory system, the cochlear nucleus. Measurements were also made for its projection pathways and the superior olivary nuclei. Cochlear ablation produces complete degeneration of the auditory nerve, which provides a baseline for interpreting the effects of partial damage to the inner ear, such as that from ototoxic drugs or intense sound. Amino acids play a critical role in neural function, including neurotransmission, neuromodulation, cellular metabolism, and protein construction. They include major neurotransmitters of the brain - glutamate, glycine, and γ-aminobutyrate (GABA) - as well as others closely related to their metabolism and/or functions - aspartate, glutamine, and taurine. Since the effects of inner ear damage develop over time, we measured the changes in amino acid levels at various survival times after cochlear ablation. Glutamate and aspartate levels decreased by 2weeks in the ipsilateral ventral cochlear nucleus and deep layer of the dorsal cochlear nucleus, with the largest decreases in the posteroventral cochlear nucleus (PVCN): 66% for glutamate and 63% for aspartate. Aspartate levels also decreased in the lateral part of the ipsilateral trapezoid body, by as much as 50%, suggesting a transneuronal effect. GABA and glycine levels showed some bilateral decreases, especially in the PVCN. These results may represent the state of amino acid metabolism in the cochlear nucleus of humans after removal of eighth nerve tumors, which may adversely result in destruction of the auditory nerve. Measurement of chemical changes following inner ear damage may increase understanding of the pathogenesis of hearing impairments and enable improvements in their diagnosis and treatment.
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Affiliation(s)
- D A Godfrey
- Department of Neurology, University of Toledo College of Medicine, Mail Stop 1195, 3000 Arlington Avenue, Toledo, OH 43614, USA; Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, 3000 Arlington Avenue, Toledo, OH 43614, USA.
| | - K Chen
- Department of Neurology, University of Toledo College of Medicine, Mail Stop 1195, 3000 Arlington Avenue, Toledo, OH 43614, USA; Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, 3000 Arlington Avenue, Toledo, OH 43614, USA
| | - M A Godfrey
- Department of Neurology, University of Toledo College of Medicine, Mail Stop 1195, 3000 Arlington Avenue, Toledo, OH 43614, USA; Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, 3000 Arlington Avenue, Toledo, OH 43614, USA
| | - A C Lee
- Department of Neurology, University of Toledo College of Medicine, Mail Stop 1195, 3000 Arlington Avenue, Toledo, OH 43614, USA; Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, 3000 Arlington Avenue, Toledo, OH 43614, USA
| | - S P Crass
- Department of Neurology, University of Toledo College of Medicine, Mail Stop 1195, 3000 Arlington Avenue, Toledo, OH 43614, USA; Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, 3000 Arlington Avenue, Toledo, OH 43614, USA
| | - D Shipp
- Department of Neurology, University of Toledo College of Medicine, Mail Stop 1195, 3000 Arlington Avenue, Toledo, OH 43614, USA; Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, 3000 Arlington Avenue, Toledo, OH 43614, USA
| | - H Simo
- Department of Neurology, University of Toledo College of Medicine, Mail Stop 1195, 3000 Arlington Avenue, Toledo, OH 43614, USA; Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, 3000 Arlington Avenue, Toledo, OH 43614, USA
| | - K T Robinson
- Department of Neurology, University of Toledo College of Medicine, Mail Stop 1195, 3000 Arlington Avenue, Toledo, OH 43614, USA; Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, 3000 Arlington Avenue, Toledo, OH 43614, USA
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Godfrey DA, Jin YM, Liu X, Godfrey MA. Effects of cochlear ablation on amino acid levels in the rat cochlear nucleus and superior olive. Hear Res 2014; 309:44-54. [PMID: 24291808 PMCID: PMC5819880 DOI: 10.1016/j.heares.2013.11.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 11/05/2013] [Accepted: 11/19/2013] [Indexed: 11/21/2022]
Abstract
Amino acids have important roles in the chemistry of the auditory system, including communication among neurons. There is much evidence for glutamate as a neurotransmitter from auditory nerve fibers to cochlear nucleus neurons. Previous studies in rodents have examined effects of removal of auditory nerve input by cochlear ablation on levels, uptake and release of glutamate in cochlear nucleus subdivisions, as well as on glutamate receptors. Effects have also been reported on uptake and release of γ-aminobutyrate (GABA) and glycine, two other amino acids strongly implicated in cochlear nucleus synaptic transmission. We mapped the effects of cochlear ablation on the levels of amino acids, including glutamate, GABA, glycine, aspartate, glutamine, taurine, serine, threonine, and arginine, in microscopic subregions of the rat cochlear nucleus. Submicrogram-size samples microdissected from freeze-dried brainstem sections were assayed for amino acid levels by high performance liquid chromatography. After cochlear ablation, glutamate and aspartate levels decreased by 2 days in regions receiving relatively dense innervation from the auditory nerve, whereas the levels of most other amino acids increased. The results are consistent with a close association of glutamate and aspartate with auditory nerve fibers and of other amino acids with other neurons and glia in the cochlear nucleus. A consistent decrease of GABA level in the lateral superior olive could be consistent with a role in some lateral olivocochlear neurons. The results are compared with those obtained with the same methods for the rat vestibular nerve root and nuclei after vestibular ganglionectomy.
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Affiliation(s)
- Donald A Godfrey
- Department of Neurology and Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, Toledo, OH, USA.
| | - Yong-Ming Jin
- Department of Neurology and Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, Toledo, OH, USA
| | - Xiaochen Liu
- Department of Neurology and Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, Toledo, OH, USA
| | - Matthew A Godfrey
- Department of Neurology and Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, Toledo, OH, USA
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Liu P, Zhang H, Devaraj R, Ganesalingam GS, Smith PF. A multivariate analysis of the effects of aging on glutamate, GABA and arginine metabolites in the rat vestibular nucleus. Hear Res 2010; 269:122-33. [DOI: 10.1016/j.heares.2010.06.019] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Revised: 06/21/2010] [Accepted: 06/22/2010] [Indexed: 01/21/2023]
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Neuhofer W, Pittrow D. Endothelin receptor selectivity in chronic kidney disease: rationale and review of recent evidence. Eur J Clin Invest 2009; 39 Suppl 2:50-67. [PMID: 19335747 DOI: 10.1111/j.1365-2362.2009.02121.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Endothelin (ET) is a potent vasoconstrictory peptide with proinflammatory and profibrotic properties that exerts its biological effects through two pharmacologically distinct receptor subtypes, namely ET(A) and ET(B). In addition to its substantial contribution to normal renal function, a large body of evidence suggests that derangement of the renal ET system is involved in the initiation and progression of chronic kidney disease (CKD) in diabetes, hypertension and glomerulonephritis. Thus, the use of ET receptor antagonists (ERAs) may offer potential novel treatment strategies in CKD. Recent literature on the role of the renal ET system in the healthy kidney was reviewed. In addition, an unbiased PubMed search was performed for studies published during the last 5 years that addressed the effects of ERAs in CKD. A particular objective was to extract information regarding whether selective or nonselective ERAs may have therapeutic potential in humans. ET-1 acts primarily as an autocrine or paracrine factor in the kidney. In normal physiology, ET-1 promotes diuresis and natriuresis by local production and action through ET(B) receptors in the renal medulla. In pathology, ET-1 mediates vasoconstriction, mesangial-cell proliferation, extracellular matrix production and inflammation, effects that are primarily conveyed by ET(A) receptors. Results obtained in animal models and in humans with the use of ERAs in CKD are encouraging; nevertheless, it is still under debate which receptor subtype should be targeted. According to most studies, selective inhibition of ET(A) receptors appears superior compared with nonselective ERAs because this approach does not interfere with the natriuretic, antihypertensive and ET clearance effects of ET(B) receptors. Although preliminary data in humans are promising, the potential role of ERAs in patients with CKD and the question of which receptor subtype should be targeted can only be clarified in randomized clinical trials.
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Affiliation(s)
- W Neuhofer
- Department of Internal Medicine, University of Munich, Munich, Germany.
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Godfrey D, Chen K, Godfrey M, Jin YM, Robinson K, Hair C. Effects of cochlear ablation on amino acid concentrations in the chinchilla posteroventral cochlear nucleus, as compared to rat. Neuroscience 2008; 154:304-14. [DOI: 10.1016/j.neuroscience.2007.12.031] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2007] [Revised: 12/12/2007] [Accepted: 12/14/2007] [Indexed: 10/22/2022]
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Sun Y, Godfrey DA, Godfrey TG, Rubin AM. Changes of amino acid concentrations in the rat vestibular nuclei after inferior cerebellar peduncle transection. J Neurosci Res 2007; 85:558-74. [PMID: 17131392 DOI: 10.1002/jnr.21136] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Although there is a close relationship between the vestibular nuclear complex (VNC) and the cerebellum, little is known about the contribution of cerebellar inputs to amino acid neurotransmission in the VNC. Microdissection of freeze-dried brain sections and high-performance liquid chromatography (HPLC) were combined to measure changes of amino acid concentrations within the VNC of rats following transection of the cerebellovestibular connections in the inferior cerebellar peduncle. Distributions of 12 amino acids within the VNC at 2, 4, 7, and 30 days after surgery were compared with those for control and sham-lesioned rats. Concentrations of gamma-aminobutyric acid (GABA) decreased by 2 days after unilateral peduncle transection in nearly all VNC regions on the lesioned side and to lesser extents on the unlesioned side and showed partial recovery up to 30 days postsurgery. Asymmetries between the two sides of the VNC were maintained through 30 days. Glutamate concentrations were reduced bilaterally in virtually all regions of the VNC by 2 days and showed complete recovery in most VNC regions by 30 days. Glutamine concentrations increased, starting 2 days after surgery, especially on the lesioned side, so that there was asymmetry generally opposite that of glutamate. Concentrations of taurine, aspartate, and glycine also underwent partially reversible changes after peduncle transection. The results suggest that GABA and glutamate are prominent neurotransmitters in bilateral projections from the cerebellum to the VNC and that amino acid metabolism in the VNC is strongly influenced by its cerebellar connections.
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Affiliation(s)
- Yizhe Sun
- Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, Toledo, Ohio 43614, USA
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Jin YM, Godfrey DA. Effects of cochlear ablation on muscarinic acetylcholine receptor binding in the rat cochlear nucleus. J Neurosci Res 2006; 83:157-66. [PMID: 16307447 DOI: 10.1002/jnr.20706] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Cholinergic synapses in the cochlear nucleus (CN) have been reported to modulate spontaneous activity via muscarinic acetylcholine receptors. In this study, muscarinic receptor binding was measured as specific binding of 1-[N-methyl-(3)H]scopolamine in CN regions of control rats and 7 days, 1 month, and 2 months after unilateral cochlear ablation. In control rats, the strongest binding was found in granular regions, followed in order by fusiform soma, molecular, and deep layers of the dorsal cochlear nucleus (DCN), with much lower binding in the anteroventral CN (AVCN) and posteroventral CN (PVCN). After unilateral cochlear ablation, binding in the AVCN, PVCN, and their associated granular regions on the lesion side became progressively greater than on the control side through 2 months after lesion. A significant asymmetry, with binding higher on the lesion side, was also found in the DCN fusiform soma layer at 7 days, and there and in the DCN deep layer at 1 and 2 months after lesion. There was also evidence of increased binding on the control side in most CN regions. By contrast, binding in the ipsilateral facial nucleus decreased, compared with the control side, by 7 days after the lesion and showed some recovery toward symmetry by 2 months after lesion, and there was no evidence for contralateral changes. These muscarinic receptor binding changes reflect receptor plasticity after loss of auditory nerve innervation. Such plasticity may underlie some of the central auditory functional changes that occur following peripheral lesions, such as tinnitus and hyperacusis.
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Affiliation(s)
- Yong-Ming Jin
- Division of Otolaryngology, Department of Surgery, Medical University of Ohio, Toledo, 43614-5807, USA
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