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Williams IR, Filimontseva A, Connelly CJ, Ryugo DK. The lateral superior olive in the mouse: Two systems of projecting neurons. Front Neural Circuits 2022; 16:1038500. [PMID: 36338332 PMCID: PMC9630946 DOI: 10.3389/fncir.2022.1038500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Accepted: 09/29/2022] [Indexed: 01/24/2023] Open
Abstract
The lateral superior olive (LSO) is a key structure in the central auditory system of mammals that exerts efferent control on cochlear sensitivity and is involved in the processing of binaural level differences for sound localization. Understanding how the LSO contributes to these processes requires knowledge about the resident cells and their connections with other auditory structures. We used standard histological stains and retrograde tracer injections into the inferior colliculus (IC) and cochlea in order to characterize two basic groups of neurons: (1) Principal and periolivary (PO) neurons have projections to the IC as part of the ascending auditory pathway; and (2) lateral olivocochlear (LOC) intrinsic and shell efferents have descending projections to the cochlea. Principal and intrinsic neurons are intermixed within the LSO, exhibit fusiform somata, and have disk-shaped dendritic arborizations. The principal neurons have bilateral, symmetric, and tonotopic projections to the IC. The intrinsic efferents have strictly ipsilateral projections, known to be tonotopic from previous publications. PO and shell neurons represent much smaller populations (<10% of principal and intrinsic neurons, respectively), have multipolar somata, reside outside the LSO, and have non-topographic, bilateral projections. PO and shell neurons appear to have widespread projections to their targets that imply a more diffuse modulatory function. The somata and dendrites of principal and intrinsic neurons form a laminar matrix within the LSO and share quantifiably similar alignment to the tonotopic axis. Their restricted projections emphasize the importance of frequency in binaural processing and efferent control for auditory perception. This study addressed and expanded on previous findings of cell types, circuit laterality, and projection tonotopy in the LSO of the mouse.
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Affiliation(s)
- Isabella R. Williams
- Garvan Institute of Medical Research, Darlinghurst, NSW, Australia,School of Medical Sciences, University of New South Wales, Kensington, NSW, Australia,*Correspondence: Isabella R. Williams,
| | | | - Catherine J. Connelly
- Garvan Institute of Medical Research, Darlinghurst, NSW, Australia,School of Medical Sciences, University of New South Wales, Kensington, NSW, Australia
| | - David K. Ryugo
- Garvan Institute of Medical Research, Darlinghurst, NSW, Australia,School of Medical Sciences, University of New South Wales, Kensington, NSW, Australia,Department of Otolaryngology-Head, Neck and Skull Base Surgery, St. Vincent’s Hospital, Darlinghurst, NSW, Australia
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Fischer AU, Müller NIC, Deller T, Del Turco D, Fisch JO, Griesemer D, Kattler K, Maraslioglu A, Roemer V, Xu-Friedman MA, Walter J, Friauf E. GABA is a modulator, rather than a classical transmitter, in the medial nucleus of the trapezoid body-lateral superior olive sound localization circuit. J Physiol 2019; 597:2269-2295. [PMID: 30776090 DOI: 10.1113/jp277566] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 02/18/2019] [Indexed: 12/13/2022] Open
Abstract
KEY POINTS The lateral superior olive (LSO), a brainstem hub involved in sound localization, integrates excitatory and inhibitory inputs from the ipsilateral and the contralateral ear, respectively. In gerbils and rats, inhibition to the LSO reportedly shifts from GABAergic to glycinergic within the first three postnatal weeks. Surprisingly, we found no evidence for synaptic GABA signalling during this time window in mouse LSO principal neurons. However, we found that presynaptic GABAB Rs modulate Ca2+ influx into medial nucleus of the trapezoid body axon terminals, resulting in reduced synaptic strength. Moreover, GABA elicited strong responses in LSO neurons that were mediated by extrasynaptic GABAA Rs. RNA sequencing revealed highly abundant δ subunits, which are characteristic of extrasynaptic receptors. Whereas GABA increased the excitability of neonatal LSO neurons, it reduced the excitability around hearing onset. Collectively, GABA appears to control the excitability of mouse LSO neurons via extrasynaptic and presynaptic signalling. Thus, GABA acts as a modulator, rather than as a classical transmitter. ABSTRACT GABA and glycine mediate fast inhibitory neurotransmission and are coreleased at several synapse types. Here we assessed the contribution of GABA and glycine in synaptic transmission between the medial nucleus of the trapezoid body (MNTB) and the lateral superior olive (LSO), two nuclei involved in sound localization. Whole-cell patch-clamp experiments in acute mouse brainstem slices at postnatal days (P) 4 and 11 during pharmacological blockade of GABAA receptors (GABAA Rs) and/or glycine receptors demonstrated no GABAergic synaptic component on LSO principal neurons. A GABAergic component was absent in evoked inhibitory postsynaptic currents and miniature events. Coimmunofluorescence experiments revealed no codistribution of the presynaptic GABAergic marker GAD65/67 with gephyrin, a postsynaptic marker for GABAA Rs, corroborating the conclusion that GABA does not act synaptically in the mouse LSO. Imaging experiments revealed reduced Ca2+ influx into MNTB axon terminals following activation of presynaptic GABAB Rs. GABAB R activation reduced the synaptic strength at P4 and P11. GABA appears to act on extrasynaptic GABAA Rs as demonstrated by application of 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol, a δ-subunit-specific GABAA R agonist. RNA sequencing showed high mRNA levels for the δ-subunit in the LSO. Moreover, GABA transporters GAT-1 and GAT-3 appear to control extracellular GABA. Finally, we show an age-dependent effect of GABA on the excitability of LSO neurons. Whereas tonic GABA increased the excitability at P4, leading to spike facilitation, it decreased the excitability at P11 via shunting inhibition through extrasynaptic GABAA Rs. Taken together, we demonstrate a modulatory role of GABA in the murine LSO, rather than a function as a classical synaptic transmitter.
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Affiliation(s)
- Alexander U Fischer
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, D-67663, Kaiserslautern, Germany
| | - Nicolas I C Müller
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, D-67663, Kaiserslautern, Germany
| | - Thomas Deller
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe-University Frankfurt, Theodor-Stern-Kai 7, D-60590, Frankfurt am Main, Germany
| | - Domenico Del Turco
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe-University Frankfurt, Theodor-Stern-Kai 7, D-60590, Frankfurt am Main, Germany
| | - Jonas O Fisch
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, D-67663, Kaiserslautern, Germany
| | - Désirée Griesemer
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, D-67663, Kaiserslautern, Germany
| | - Kathrin Kattler
- Genetics/Epigenetic Group, Department of Biological Sciences, Saarland University, D-66123, Saarbrücken
| | - Ayse Maraslioglu
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, D-67663, Kaiserslautern, Germany
| | - Vera Roemer
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, D-67663, Kaiserslautern, Germany
| | - Matthew A Xu-Friedman
- Department of Biological Sciences, University at Buffalo, State University of New York, Buffalo, NY, 14260, USA
| | - Jörn Walter
- Genetics/Epigenetic Group, Department of Biological Sciences, Saarland University, D-66123, Saarbrücken
| | - Eckhard Friauf
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, D-67663, Kaiserslautern, Germany
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Matsuura Y, Oguri M, Saito Y, Aoe Y, Ogawa A, Akiyama S, Yasuda N, Sato K, Maegaki Y, Hirooka Y. Decreased Wave V Amplitude in Auditory Brainstem Responses of Children with Cerebellar Lesions. Yonago Acta Med 2018. [DOI: 10.33160/yam.2018.12.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Yuka Matsuura
- *Department of Pathobiological Science and Technology, School of Health Science, Tottori University Faculty of Medicine, Yonago 683-8503, Japan
| | - Masayoshi Oguri
- *Department of Pathobiological Science and Technology, School of Health Science, Tottori University Faculty of Medicine, Yonago 683-8503, Japan
| | - Yoshiaki Saito
- †Division of Child Neurology, Department of Brain and Neurological Sciences, Tottori University Faculty of Medicine, Yonago 683-8504, Japan
| | - Yasutaka Aoe
- *Department of Pathobiological Science and Technology, School of Health Science, Tottori University Faculty of Medicine, Yonago 683-8503, Japan
| | - Ayame Ogawa
- *Department of Pathobiological Science and Technology, School of Health Science, Tottori University Faculty of Medicine, Yonago 683-8503, Japan
| | - Shota Akiyama
- *Department of Pathobiological Science and Technology, School of Health Science, Tottori University Faculty of Medicine, Yonago 683-8503, Japan
| | - Nanako Yasuda
- *Department of Pathobiological Science and Technology, School of Health Science, Tottori University Faculty of Medicine, Yonago 683-8503, Japan
| | - Kengo Sato
- *Department of Pathobiological Science and Technology, School of Health Science, Tottori University Faculty of Medicine, Yonago 683-8503, Japan
| | - Yoshihiro Maegaki
- †Division of Child Neurology, Department of Brain and Neurological Sciences, Tottori University Faculty of Medicine, Yonago 683-8504, Japan
| | - Yasuaki Hirooka
- *Department of Pathobiological Science and Technology, School of Health Science, Tottori University Faculty of Medicine, Yonago 683-8503, Japan
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Stephan J, Friauf E. Functional analysis of the inhibitory neurotransmitter transporters GlyT1, GAT-1, and GAT-3 in astrocytes of the lateral superior olive. Glia 2014; 62:1992-2003. [PMID: 25103283 DOI: 10.1002/glia.22720] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 06/26/2014] [Accepted: 06/27/2014] [Indexed: 01/03/2023]
Abstract
Neurotransmitter clearance from the synaptic cleft is a major function of astrocytes and requires neurotransmitter transporters. In the rodent lateral superior olive (LSO), a conspicuous auditory brainstem center, both glycine and GABA mediate synaptic inhibition. However, the main inhibitory input from the medial nucleus of the trapezoid body (MNTB) appears to be glycinergic by postnatal day (P) 14, when circuit maturation is almost accomplished. Using whole-cell patch-clamp recordings at P3-20, we analyzed glycine transporters (GlyT1) and GABA transporters (GAT-1, GAT-3) in mouse LSO astrocytes, emphasizing on their developmental regulation. Application of glycine or GABA induced a dose- and age-dependent inward current and a respective depolarization. The GlyT1-specific inhibitor sarcosine reduced the maximal glycine-induced current (IGly (max) ) by about 60%. The GAT-1 and GAT-3 antagonists NO711 and SNAP5114, respectively, reduced the maximal GABA-induced current (IGABA (max) ) by about 35%. Furthermore, [Cl(-) ]o reduction decreased IGly (max) and IGABA (max) by about 85 to 95%, showing the Cl(-) dependence of GlyT and GAT. IGABA (max) was stronger than IGly (max) , and the ratio increased developmentally from 1.6-fold to 3.7-fold. Together, our results demonstrate the functional presence of the three inhibitory neurotransmitter transporters GlyT1, GAT-1, and GAT-3 in LSO astrocytes. Furthermore, the uptake capability for GABA was higher than for glycine, pointing toward eminent GABAergic signaling in the LSO. GABA may originate from another source than the MNTB-LSO synapses, namely from another projection or from reversal of astrocytic GATs. Thus, neuronal signaling in the LSO appears to be more versatile than previously thought. GLIA 2014;62:1992-2003.
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Affiliation(s)
- Jonathan Stephan
- Department of Biology, Animal Physiology Group, University of Kaiserslautern, Kaiserslautern, Germany
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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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Kaiser A, Alexandrova O, Grothe B. Urocortin-expressing olivocochlear neurons exhibit tonotopic and developmental changes in the auditory brainstem and in the innervation of the cochlea. J Comp Neurol 2011; 519:2758-78. [DOI: 10.1002/cne.22650] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Forebrain ischemia triggers GABAergic system degeneration in substantia nigra at chronic stages in rats. Cardiovasc Psychiatry Neurol 2010; 2010:506952. [PMID: 20981346 PMCID: PMC2957857 DOI: 10.1155/2010/506952] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2010] [Revised: 06/10/2010] [Accepted: 08/11/2010] [Indexed: 11/17/2022] Open
Abstract
The long-term consequences of forebrain ischemia include delayed Parkinson's syndrome. This study revealed delayed neurodegeneration in the substantia nigra 8 weeks after 12.5 minutes of global ischemia in rat brain. Following neuronal loss of 30-40% in central and dorsolateral striatum at day 3, neuronal damage in the substantia nigra (SN) was assessed at 4-8 weeks using immunohistochemistry for glutamate decarboxylase 67 (GAD67), vesicular GABA transporter (VGAT), and calretinin (CR). At day 56, the optical density of GAD67-, but not VGAT-, immunoreactivity in substantia nigra pars reticulata (SNR)-significantly decreased. CR-neurons concentrated in substantia nigra pars compacta (SNC) were reduced by 27% from day 3 (n = 5) to day 56 (n = 7, ANOVA, p < .01). Movement coordination was impaired at day 56, as evaluated using beam-walking test (time-to-traverse 5.6 ± 1.2 sec versus 11.8 ± 5.4 sec; sham versus ischemia, p < .05, n = 5, and 7, resp.). Our results demonstrate delayed impairment of the GABAergic system components in SN and associated with movement deficits after global ischemia.
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Solbu TT, Bjørkmo M, Berghuis P, Harkany T, Chaudhry FA. SAT1, A Glutamine Transporter, is Preferentially Expressed in GABAergic Neurons. Front Neuroanat 2010; 4:1. [PMID: 20161990 PMCID: PMC2820376 DOI: 10.3389/neuro.05.001.2010] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Accepted: 12/30/2009] [Indexed: 11/13/2022] Open
Abstract
Subsets of GABAergic neurons are able to maintain high frequency discharge patterns, which requires efficient replenishment of the releasable pool of GABA. Although glutamine is considered a preferred precursor of GABA, the identity of transporters involved in glutamine uptake by GABAergic neurons remains elusive. Molecular analyses revealed that SAT1 (Slc38a1) features system A characteristics with a preferential affinity for glutamine, and that SAT1 mRNA expression is associated with GABAergic neurons. By generating specific antibodies against SAT1 we show that this glutamine carrier is particularly enriched in GABAergic neurons. Cellular SAT1 distribution resembles that of GAD67, an essential GABA synthesis enzyme, suggesting that SAT1 can be involved in translocating glutamine into GABAergic neurons to facilitate inhibitory neurotransmitter generation.
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Affiliation(s)
- Tom Tallak Solbu
- The Biotechnology Centre of Oslo, University of Oslo Oslo, Norway
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Cell Biology and Physiology of the Aging Central Auditory Pathway. THE AGING AUDITORY SYSTEM 2010. [DOI: 10.1007/978-1-4419-0993-0_3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Kumar S, Porcu P, Werner DF, Matthews DB, Diaz-Granados JL, Helfand RS, Morrow AL. The role of GABA(A) receptors in the acute and chronic effects of ethanol: a decade of progress. Psychopharmacology (Berl) 2009; 205:529-64. [PMID: 19455309 PMCID: PMC2814770 DOI: 10.1007/s00213-009-1562-z] [Citation(s) in RCA: 342] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Accepted: 04/30/2009] [Indexed: 12/12/2022]
Abstract
The past decade has brought many advances in our understanding of GABA(A) receptor-mediated ethanol action in the central nervous system. We now know that specific GABA(A) receptor subtypes are sensitive to ethanol at doses attained during social drinking while other subtypes respond to ethanol at doses attained by severe intoxication. Furthermore, ethanol increases GABAergic neurotransmission through indirect effects, including the elevation of endogenous GABAergic neuroactive steroids, presynaptic release of GABA, and dephosphorylation of GABA(A) receptors promoting increases in GABA sensitivity. Ethanol's effects on intracellular signaling also influence GABAergic transmission in multiple ways that vary across brain regions and cell types. The effects of chronic ethanol administration are influenced by adaptations in GABA(A) receptor function, expression, trafficking, and subcellular localization that contribute to ethanol tolerance, dependence, and withdrawal hyperexcitability. Adolescents exhibit altered sensitivity to ethanol actions, the tendency for higher drinking and longer lasting GABAergic adaptations to chronic ethanol administration. The elucidation of the mechanisms that underlie adaptations to ethanol exposure are leading to a better understanding of the regulation of inhibitory transmission and new targets for therapies to support recovery from ethanol withdrawal and alcoholism.
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Affiliation(s)
- Sandeep Kumar
- Department of Psychiatry, Bowles Center for Alcohol Studies, University of North Carolina School of Medicine, 3027 Thurston-Bowles Building, CB #7178, Chapel Hill, NC 27599-7178, USA
| | - Patrizia Porcu
- Department of Psychiatry, Bowles Center for Alcohol Studies, University of North Carolina School of Medicine, 3027 Thurston-Bowles Building, CB #7178, Chapel Hill, NC 27599-7178, USA
| | - David F. Werner
- Department of Psychiatry, Bowles Center for Alcohol Studies, University of North Carolina School of Medicine, 3027 Thurston-Bowles Building, CB #7178, Chapel Hill, NC 27599-7178, USA
| | | | | | - Rebecca S. Helfand
- Department of Psychology and Neuroscience, Baylor University, Waco, TX, USA
| | - A. Leslie Morrow
- Department of Psychiatry, Bowles Center for Alcohol Studies, University of North Carolina School of Medicine, 3027 Thurston-Bowles Building, CB #7178, Chapel Hill, NC 27599-7178, USA, Department of Pharmacology, Bowles Center for Alcohol Studies, University of North Carolina School of Medicine, 3027 Thurston-Bowles Building, CB #7178, Chapel Hill, NC 27599-7178, USA
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Toyoshima M, Sakurai K, Shimazaki K, Takeda Y, Nakamoto M, Serizawa S, Shimoda Y, Watanabe K. Preferential localization of neural cell recognition molecule NB-2 in developing glutamatergic neurons in the rat auditory brainstem. J Comp Neurol 2009; 513:349-62. [PMID: 19177518 DOI: 10.1002/cne.21972] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
NB-2 is a neuronal cell recognition molecule that is preferentially expressed in auditory pathways. Mice deficient in the NB-2 gene exhibit aberrant responses to acoustic stimuli. Here we examined the expression and localization of NB-2 in the auditory brainstem during development in the rat. NB-2 was strongly expressed in the ventral cochlear nucleus (VCN), ventral acoustic stria, lateral and medial superior olivary complex (SOC), superior paraolivary nucleus, medial nucleus of the trapezoid body (MNTB), ventrolateral lemniscus, and central nucleus of the inferior colliculus (CIC). In the VCN and CIC, NB-2 was expressed in the regions that are known to respond to high frequencies. In situ hybridization combined with immunohistochemistry suggested that NB-2 is expressed only in neurons. NB-2 was colocalized with glutamatergic elements in the neuropil and the calyces of Held but not with glycinergic or GABAergic elements. NB-2 expression in the SOC was first detected at embryonic day (E)19, reached a maximum level at postnatal day (P)7, and declined thereafter. Immunolabeling with VGLUT1 and VGLUT2, markers for mature and premature glutamatergic synapses, respectively, in combination with NB-2 immunolabeling revealed that NB-2 is expressed at glutamatergic synapses. Collectively, our findings suggest that NB-2 plays a key role in maturation of glutamatergic synapses in the brainstem during the final stages of auditory development.
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Affiliation(s)
- Manabu Toyoshima
- Department of Bioengineering, Nagaoka University of Technology, Nagaoka, Niigata 940-2188, Japan
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Martyniuk CJ, Awad R, Hurley R, Finger TE, Trudeau VL. Glutamic acid decarboxylase 65, 67, and GABA-transaminase mRNA expression and total enzyme activity in the goldfish (Carassius auratus) brain. Brain Res 2007; 1147:154-66. [PMID: 17362888 DOI: 10.1016/j.brainres.2007.02.010] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2006] [Revised: 01/31/2007] [Accepted: 02/02/2007] [Indexed: 11/26/2022]
Abstract
GAD65 and GAD67 are the two major isoforms of the enzyme that converts glutamate into GABA in a single step reaction. Despite studies describing GAD65 and GAD67 mRNA expression in the mammalian brain, both GAD65 and GAD67 mRNA expression has not yet been fully described for a non-mammalian vertebrate model. Similarly, the expression patterns of GABA-T mRNA, the major enzyme involved in metabolizing GABA, have not been described for any vertebrate. In the present study, we utilized non-radioactive in situ hybridization to localize GAD65, GAD67, and GABA-T in the adult goldfish brain and complimented this with an in vitro assessment of total GAD and GABA-T enzyme activities. A partial fragment of goldfish GABA-T was cloned for a riboprobe that showed approximately 92% deduced amino acid identity to zebrafish GABA-T and 78% identity to human GABA-T. Transcripts for GAD65, GAD67, and GABA-T were detected throughout the brain and were detected largely in the medial and ventral regions of the telencephalon, nucleus preopticus, nucleus recessus lateralis of the hypothalamus, and Purkinje cell layer of the cerebellum. GAD65 mRNA was significantly more abundant in the nucleus recessus posterioris of the hypothalamus than GAD67 and GABA-T mRNA. Total GAD and GABA-T specific enzyme activity was highest in the hypothalamus and optic tectum and GABA-T activity was significantly higher than total GAD enzyme activity. Our results show that GAD65, GAD67, and GABA-T mRNAs are generally correlated with total GAD and GABA-T activity and all three transcripts have a largely overlapping mRNA distribution in the goldfish forebrain.
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Affiliation(s)
- Christopher J Martyniuk
- Centre for Advanced Research in Environmental Genomics, Department of Biology, University of Ottawa, 20 Marie Curie, Ottawa, Ontario, Canada K1N 6N5
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