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Cho YS, Mah W, Youn DH, Kim YS, Ko HG, Bae JY, Kim YS, Bae YC. Increase of glutamate in satellite glial cells of the trigeminal ganglion in a rat model of craniofacial neuropathic pain. Front Neuroanat 2023; 17:1302373. [PMID: 38164516 PMCID: PMC10758013 DOI: 10.3389/fnana.2023.1302373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Accepted: 11/27/2023] [Indexed: 01/03/2024] Open
Abstract
Introduction Satellite glial cells (SGCs) that envelop the cell bodies of neurons in sensory ganglia have been shown to both release glutamate, and be activated by glutamate in the context of nociceptive signaling. However, little is known about the subpopulations of SGCs that are activated following nerve injury and whether glutamate mechanisms in the SGCs are involved in the pathologic pain. Methods To address this issue, we used light and electron microscopic immunohistochemistry to examine the change in the glutamate levels in the SGCs and the structural relationship between neighboring neurons in the trigeminal ganglion (TG) in a rat model of craniofacial neuropathic pain, CCI-ION. Results Administration of ionomycin, ATP and Bz-ATP induced an increase of extracellular glutamate concentration in cultured trigeminal SGCs, indicating a release of glutamate from SGCs. The level of glutamate immunostaining in the SGCs that envelop neurons of all sizes in the TG was significantly higher in rats with CCI-ION than in control rats, suggesting that SGCs enveloping nociceptive as well as non-nociceptive mechanosensitive neurons are activated following nerve injury, and that the glutamate release from SGCs increases in pathologic pain state. Close appositions between substance-P (SP)-immunopositive (+) or calcitonin gene-related peptide (CGRP)+, likely nociceptive neurons, between Piezo1+, likely non-nociceptive, mechanosensitive neurons and SP+ or CGRP+ neurons, and between SGCs of neighboring neurons were frequently observed. Discussion These findings suggest that glutamate in the trigeminal SGCs that envelop all types of neurons may play a role in the mechanisms of neuropathic pain, possibly via paracrine signaling.
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Affiliation(s)
- Yi Sul Cho
- Department of Anatomy, Physiology and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea
| | - Won Mah
- Department of Anatomy, Physiology and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea
| | - Dong Ho Youn
- Department of Anatomy, Physiology and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea
| | - Yu Shin Kim
- Department of Oral & Maxillofacial Surgery, School of Dentistry, Programs in Integrated Biomedical Sciences, Translational Sciences, Biomedical Engineering, Radiological Sciences, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States
| | - Hyoung-Gon Ko
- Department of Anatomy, Physiology and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea
| | - Jin Young Bae
- Department of Anatomy, Physiology and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea
| | - Yun Sook Kim
- Department of Anatomy, Physiology and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea
| | - Yong Chul Bae
- Department of Anatomy, Physiology and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea
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2
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Haragopal H, Mellott JG, Dhar M, Kanel A, Mafi A, Tokar N, Winters BD. Tonotopic distribution and inferior colliculus projection pattern of inhibitory and excitatory cell types in the lateral superior olive of mice. J Comp Neurol 2023; 531:1381-1388. [PMID: 37436768 DOI: 10.1002/cne.25515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 05/26/2023] [Accepted: 06/10/2023] [Indexed: 07/13/2023]
Abstract
The principal neurons (PNs) of the lateral superior olive nucleus (LSO) are an important component of mammalian brainstem circuits that compare activity between the two ears and extract intensity and timing differences used for sound localization. There are two LSO PN transmitter types, glycinergic and glutamatergic, which also have different ascending projection patterns to the inferior colliculus (IC). Glycinergic LSO PNs project ipsilaterally while glutamatergic one's projections vary in laterality by species. In animals with good low-frequency hearing (<3 kHz) such as cats and gerbils, glutamatergic LSO PNs have both ipsilateral and contralateral projections; however, rats that lack this ability only have the contralateral pathway. Additionally, in gerbils, the glutamatergic ipsilateral projecting LSO PNs are biased to the low-frequency limb of the LSO suggesting this pathway may be an adaptation for low-frequency hearing. To further test this premise, we examined the distribution and IC projection pattern of LSO PNs in another high-frequency specialized species using mice by combining in situ hybridization and retrograde tracer injections. We observed no overlap between glycinergic and glutamatergic LSO PNs confirming they are distinct cell populations in mice as well. We found that mice also lack the ipsilateral glutamatergic projection from LSO to IC and that their LSO PN types do not exhibit pronounced tonotopic biases. These data provide insights into the cellular organization of the superior olivary complex and its output to higher processing centers that may underlie functional segregation of information.
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Affiliation(s)
- Hariprakash Haragopal
- Department of Anatomy and Neurobiology and Hearing Research Group, Northeast Ohio Medical University, Rootstown, Ohio, USA
| | - Jeffrey G Mellott
- Department of Anatomy and Neurobiology and Hearing Research Group, Northeast Ohio Medical University, Rootstown, Ohio, USA
- Brain Health Research Institute, Kent State University, Kent, Ohio, USA
| | - Matasha Dhar
- Department of Anatomy and Neurobiology and Hearing Research Group, Northeast Ohio Medical University, Rootstown, Ohio, USA
| | - Alinea Kanel
- Department of Anatomy and Neurobiology and Hearing Research Group, Northeast Ohio Medical University, Rootstown, Ohio, USA
| | - Amir Mafi
- Department of Anatomy and Neurobiology and Hearing Research Group, Northeast Ohio Medical University, Rootstown, Ohio, USA
| | - Nick Tokar
- Department of Anatomy and Neurobiology and Hearing Research Group, Northeast Ohio Medical University, Rootstown, Ohio, USA
| | - Bradley D Winters
- Department of Anatomy and Neurobiology and Hearing Research Group, Northeast Ohio Medical University, Rootstown, Ohio, USA
- Brain Health Research Institute, Kent State University, Kent, Ohio, USA
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3
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Ping Y, Ohata K, Kikushima K, Sakamoto T, Islam A, Xu L, Zhang H, Chen B, Yan J, Eto F, Nakane C, Takao K, Miyakawa T, Kabashima K, Watanabe M, Kahyo T, Yao I, Fukuda A, Ikegami K, Konishi Y, Setou M. Tubulin Polyglutamylation by TTLL1 and TTLL7 Regulate Glutamate Concentration in the Mice Brain. Biomolecules 2023; 13:biom13050784. [PMID: 37238654 DOI: 10.3390/biom13050784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 04/27/2023] [Accepted: 04/30/2023] [Indexed: 05/28/2023] Open
Abstract
As an important neurotransmitter, glutamate acts in over 90% of excitatory synapses in the human brain. Its metabolic pathway is complicated, and the glutamate pool in neurons has not been fully elucidated. Tubulin polyglutamylation in the brain is mainly mediated by two tubulin tyrosine ligase-like (TTLL) proteins, TTLL1 and TTLL7, which have been indicated to be important for neuronal polarity. In this study, we constructed pure lines of Ttll1 and Ttll7 knockout mice. Ttll knockout mice showed several abnormal behaviors. Matrix-assisted laser desorption/ionization (MALDI) Imaging mass spectrometry (IMS) analyses of these brains showed increases in glutamate, suggesting that tubulin polyglutamylation by these TTLLs acts as a pool of glutamate in neurons and modulates some other amino acids related to glutamate.
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Affiliation(s)
- Yashuang Ping
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Kenji Ohata
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
- Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Kenji Kikushima
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
- International Mass Imaging Center, Hamamatsu University School of Medicine, Hamamatsu, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Takumi Sakamoto
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Ariful Islam
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Lili Xu
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Hengsen Zhang
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Bin Chen
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Jing Yan
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Fumihiro Eto
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Chiho Nakane
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Keizo Takao
- Department of Behavioral Physiology, Faculty of Medicine, University of Toyama, 2630 Sugitani, Toyama-shi, Toyama 930-0194, Japan
- Genetic Engineering and Functional Genomics Unit, Frontier Technology Center, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
| | - Tsuyoshi Miyakawa
- Genetic Engineering and Functional Genomics Unit, Frontier Technology Center, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
- Institute for Comprehensive Medical Science Division of Systems Medicine, Fujita Health University, Aichi 470-1192, Japan
| | - Katsuya Kabashima
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Miho Watanabe
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Tomoaki Kahyo
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
- International Mass Imaging Center, Hamamatsu University School of Medicine, Hamamatsu, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Ikuko Yao
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
- International Mass Imaging Center, Hamamatsu University School of Medicine, Hamamatsu, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
- Department of Biomedical Sciences, School of Biological and Environmental Sciences, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo 669-1330, Japan
| | - Atsuo Fukuda
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Koji Ikegami
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
- Department of Anatomy and Developmental Biology, Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Hiroshima 734-8553, Japan
| | - Yoshiyuki Konishi
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
- Department of Applied Chemistry and Biotechnology, University of Fukui, 3-9-1 Bunkyo, Fukui-shi, Fukui 910-8507, Japan
| | - Mitsutoshi Setou
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
- International Mass Imaging Center, Hamamatsu University School of Medicine, Hamamatsu, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
- Department of Systems Molecular Anatomy, Institute for Medical Photonics Research, Preeminent Medical Photonics Education & Research Center, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
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4
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Mellott JG, Dhar M, Mafi A, Tokar N, Winters BD. Tonotopic distribution and inferior colliculus projection pattern of inhibitory and excitatory cell types in the lateral superior olive of Mongolian gerbils. J Comp Neurol 2022; 530:506-517. [PMID: 34338321 PMCID: PMC8716415 DOI: 10.1002/cne.25226] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Revised: 07/27/2021] [Accepted: 07/29/2021] [Indexed: 02/03/2023]
Abstract
Sound localization critically relies on brainstem neurons that compare information from the two ears. The conventional role of the lateral superior olive (LSO) is extraction of intensity differences; however, it is increasingly clear that relative timing, especially of transients, is also an important function. Cellular diversity within the LSO that is not well understood may underlie its multiple roles. There are glycinergic inhibitory and glutamatergic excitatory principal neurons in the LSO, however, there is some disagreement regarding their relative distribution and projection pattern. Here we employ in situ hybridization to definitively identify transmitter types combined with retrograde labeling of projections to the inferior colliculus (IC) to address these questions. Excitatory LSO neurons were more numerous (76%) than inhibitory ones. A smaller proportion of inhibitory neurons were IC-projecting (45% vs. 64% for excitatory) suggesting that inhibitory LSO neurons may have more projections to other regions such the lateral lemniscus or more distributed IC projections. Inhibitory LSO neurons almost exclusively projected ipsilaterally making up a sizeable proportion (41%) of the transmitter type-labeled ipsilateral IC projection from LSO and exhibited a moderate low frequency bias (10% difference H-L). Two thirds of excitatory neurons projected contralaterally and had a slight high frequency bias (4%). One third of excitatory LSO neurons projected ipsilaterally to the IC and these cells were strongly biased toward the low frequency limb of the LSO (37%). This projection appears to be species specific in animals with good low frequency hearing suggesting that it may be a specialization for such ability.
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Affiliation(s)
- Jeffrey G. Mellott
- Department of Anatomy and Neurobiology, Hearing Research Group, Northeast Ohio Medical University, Hearing Research Group, Rootstown, OH, United States,Brain Health Research Institute, Kent State University, Kent, OH, United States
| | - Matasha Dhar
- Department of Anatomy and Neurobiology, Hearing Research Group, Northeast Ohio Medical University, Hearing Research Group, Rootstown, OH, United States
| | - Amir Mafi
- Department of Anatomy and Neurobiology, Hearing Research Group, Northeast Ohio Medical University, Hearing Research Group, Rootstown, OH, United States
| | - Nick Tokar
- Department of Anatomy and Neurobiology, Hearing Research Group, Northeast Ohio Medical University, Hearing Research Group, Rootstown, OH, United States
| | - Bradley D. Winters
- Department of Anatomy and Neurobiology, Hearing Research Group, Northeast Ohio Medical University, Hearing Research Group, Rootstown, OH, United States,Brain Health Research Institute, Kent State University, Kent, OH, United States
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5
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Pfeiffer RL, Anderson JR, Dahal J, Garcia JC, Yang JH, Sigulinsky CL, Rapp K, Emrich DP, Watt CB, Johnstun HA, Houser AR, Marc RE, Jones BW. A pathoconnectome of early neurodegeneration: Network changes in retinal degeneration. Exp Eye Res 2020; 199:108196. [PMID: 32810483 DOI: 10.1016/j.exer.2020.108196] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 07/27/2020] [Accepted: 08/11/2020] [Indexed: 10/23/2022]
Abstract
Connectomics has demonstrated that synaptic networks and their topologies are precise and directly correlate with physiology and behavior. The next extension of connectomics is pathoconnectomics: to map neural network synaptology and circuit topologies corrupted by neurological disease in order to identify robust targets for therapeutics. In this report, we characterize a pathoconnectome of early retinal degeneration. This pathoconnectome was generated using serial section transmission electron microscopy to achieve an ultrastructural connectome with 2.18nm/px resolution for accurate identification of all chemical and gap junctional synapses. We observe aberrant connectivity in the rod-network pathway and novel synaptic connections deriving from neurite sprouting. These observations reveal principles of neuron responses to the loss of network components and can be extended to other neurodegenerative diseases.
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Affiliation(s)
- Rebecca L Pfeiffer
- John Moran Eye Center at the University of Utah, Salt Lake City, UT, USA.
| | - James R Anderson
- John Moran Eye Center at the University of Utah, Salt Lake City, UT, USA
| | - Jeebika Dahal
- John Moran Eye Center at the University of Utah, Salt Lake City, UT, USA
| | - Jessica C Garcia
- John Moran Eye Center at the University of Utah, Salt Lake City, UT, USA
| | - Jia-Hui Yang
- John Moran Eye Center at the University of Utah, Salt Lake City, UT, USA
| | | | - Kevin Rapp
- John Moran Eye Center at the University of Utah, Salt Lake City, UT, USA
| | - Daniel P Emrich
- John Moran Eye Center at the University of Utah, Salt Lake City, UT, USA
| | - Carl B Watt
- John Moran Eye Center at the University of Utah, Salt Lake City, UT, USA
| | - Hope Ab Johnstun
- John Moran Eye Center at the University of Utah, Salt Lake City, UT, USA
| | - Alexis R Houser
- John Moran Eye Center at the University of Utah, Salt Lake City, UT, USA
| | - Robert E Marc
- John Moran Eye Center at the University of Utah, Salt Lake City, UT, USA; Signature Immunologics, Torrey, UT, USA
| | - Bryan W Jones
- John Moran Eye Center at the University of Utah, Salt Lake City, UT, USA.
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6
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Ormel L, Lauritzen KH, Schreiber R, Kunzelmann K, Gundersen V. GABA, but Not Bestrophin-1, Is Localized in Astroglial Processes in the Mouse Hippocampus and the Cerebellum. Front Mol Neurosci 2020; 13:135. [PMID: 32848599 PMCID: PMC7399226 DOI: 10.3389/fnmol.2020.00135] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Accepted: 07/07/2020] [Indexed: 11/13/2022] Open
Abstract
GABA is proposed to act as a gliotransmitter in the brain. Differences in GABA release from astroglia are thought to underlie differences in tonic inhibition between the cerebellum and the CA1 hippocampus. Here we used quantitative immunogold cytochemistry to localize and compare the levels of GABA in astroglia in these brain regions. We found that the density of GABA immunogold particles was similar in delicate processes of Bergman glia in the cerebellum and astrocytes in the CA1 hippocampus. The astrocytic GABA release is proposed to be mediated by, among others, the Ca2+ activated Cl- channel bestrophin-1. The bestrophin-1 antibodies did not show any significant bestrophin-1 signal in the brain of wt mice, nor in bestrophin-1 knockout mice. The bestrophin-1 signal was low both on Western blots and immunofluorescence laser scanning microscopic images. These results suggest that GABA is localized in astroglia, but in similar concentrations in the cerebellum and CA1 hippocampus, and thus cannot account for differences in tonic inhibition between these brain regions. Furthermore, our data seem to suggest that the GABA release from astroglia previously observed in the hippocampus and cerebellum occurs via mechanisms other than bestrophin-1.
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Affiliation(s)
- Lasse Ormel
- Section of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.,Department of Neurology, Oslo University Hospital, Ullevål, Oslo, Norway
| | - Knut H Lauritzen
- Section of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.,Research Institute of Internal Medicine, Oslo University Hospital, Rikshospitalet, Oslo, Norway
| | - Rainer Schreiber
- Department of Physiology, University of Regensburg, Regensburg, Germany
| | - Karl Kunzelmann
- Department of Physiology, University of Regensburg, Regensburg, Germany
| | - Vidar Gundersen
- Section of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.,Section for Movement Disorders, Department of Neurology, Oslo University Hospital, Rikshospitalet, Oslo, Norway
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7
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Paik SK, Yoo HI, Choi SK, Bae JY, Park SK, Bae YC. Distribution of excitatory and inhibitory axon terminals on the rat hypoglossal motoneurons. Brain Struct Funct 2019; 224:1767-1779. [PMID: 31006070 DOI: 10.1007/s00429-019-01874-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 04/11/2019] [Indexed: 12/19/2022]
Abstract
Detailed information about the excitatory and inhibitory synapses on the hypoglossal motoneurons may help understand the neural mechanism for control of the hypoglossal motoneuron excitability and hence the precise and coordinated movements of the tongue during chewing, swallowing and licking. For this, we investigated the distribution of GABA-, glycine (Gly)- and glutamate (Glut)-immunopositive (+) axon terminals on the genioglossal (GG) motoneurons by retrograde tracing, electron microscopic immunohistochemistry, and quantitative analysis. Small GG motoneurons (< 400 μm2 in cross-sectional area) had fewer primary dendrites, significantly higher nuclear/cytoplasmic ratio, and smaller membrane area covered by synaptic boutons than large GG motoneurons (> 400 μm2). The fraction of inhibitory boutons (GABA + only, Gly + only, and mixed GABA +/Gly + boutons) of all boutons was significantly higher for small GG motoneurons than for large ones, whereas the fraction of Glut + boutons was significantly higher for large GG motoneurons than for small ones. Almost all boutons (> 95%) on both small and large GG motoneurons were GABA + , Gly + or Glut + . The frequency of mixed GABA +/Gly + boutons was the highest among inhibitory boutons types for both small and large GG motoneurons. These findings may elucidate the anatomical substrate for precise regulation of the motoneuron firing required for the fine movements of the tongue, and also suggest that the excitability of small and large GG motoneurons may be regulated differently.
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Affiliation(s)
- Sang Kyoo Paik
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, 188-1, 2-Ga, Samdeok-Dong, Jung-Gu, Daegu, 700-412, South Korea
| | - Hong Il Yoo
- Department of Anatomy and Neuroscience, College of Medicine, Eulji University, 77 Gyeryong-ro 771 beon-gil, Jung-Gu, Daejeon, 34824, South Korea
| | - Seung Ki Choi
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, 188-1, 2-Ga, Samdeok-Dong, Jung-Gu, Daegu, 700-412, South Korea
| | - Jin Young Bae
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, 188-1, 2-Ga, Samdeok-Dong, Jung-Gu, Daegu, 700-412, South Korea
| | - Sook Kyung Park
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, 188-1, 2-Ga, Samdeok-Dong, Jung-Gu, Daegu, 700-412, South Korea
| | - Yong Chul Bae
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, 188-1, 2-Ga, Samdeok-Dong, Jung-Gu, Daegu, 700-412, South Korea.
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8
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Upregulation of the lactate transporter monocarboxylate transporter 1 at the blood-brain barrier in a rat model of attention-deficit/hyperactivity disorder suggests hyperactivity could be a form of self-treatment. Behav Brain Res 2019; 360:279-285. [DOI: 10.1016/j.bbr.2018.12.023] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 11/20/2018] [Accepted: 12/11/2018] [Indexed: 12/27/2022]
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9
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Chatard C, Meiller A, Marinesco S. Microelectrode Biosensors forin vivoAnalysis of Brain Interstitial Fluid. ELECTROANAL 2018. [DOI: 10.1002/elan.201700836] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Charles Chatard
- INSERM U1028, CNRS UMR5292; Lyon Neuroscience Research Center, Team TIGER
- Université Claude Bernard Lyon 1; Lyon France
| | - Anne Meiller
- AniRA-Neurochem Technological Platform; Lyon France
- Université Claude Bernard Lyon 1; Lyon France
| | - Stéphane Marinesco
- INSERM U1028, CNRS UMR5292; Lyon Neuroscience Research Center, Team TIGER
- AniRA-Neurochem Technological Platform; Lyon France
- Université Claude Bernard Lyon 1; Lyon France
- Lyon Neuroscience Research Center, Team TIGER; Faculty of Medicine; 8 Avenue Rockefeller 69373 Lyon Cedex 08 France
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10
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Enger R. Automated gold particle quantification of immunogold labeled micrographs. J Neurosci Methods 2017; 286:31-37. [PMID: 28527623 DOI: 10.1016/j.jneumeth.2017.05.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Revised: 05/10/2017] [Accepted: 05/13/2017] [Indexed: 11/28/2022]
Abstract
BACKGROUND Immunogold cytochemistry is the method of choice for precise localization of antigens on a subcellular scale. The process of immunogold quantification in electron micrographs is laborious, especially for proteins with a dense distribution pattern. NEW METHODS Here I present a MATLAB based toolbox that is optimized for a typical immunogold analysis workflow. It combines automatic detection of gold particles through a multi-threshold algorithm with manual segmentation of cell membranes and regions of interests. RESULTS The automated particle detection algorithm was applied to a typical immunogold dataset of neural tissue, and was able to detect particles with a high degree of precision. Without manual correction, the algorithm detected 97% of all gold particles, with merely a 0.1% false-positive rate. COMPARISONS WITH EXISTING METHOD(S) To my knowledge, this is the first free and publicly available software custom made for immunogold analyses. The proposed particle detection method compares favorably to previously published algorithms. CONCLUSIONS The software presented here will be valuable tool for researchers in neuroscience working with immunogold cytochemistry.
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Affiliation(s)
- Rune Enger
- Oslo University Hospital, Department of Neurology, N-0027 Oslo, Norway; Letten Centre and GliaLab, Division of Physiology, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, N-0317 Oslo, Norway.
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11
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Cho YS, Ryu CH, Won JH, Vang H, Oh SB, Ro JY, Bae YC. Rat odontoblasts may use glutamate to signal dentin injury. Neuroscience 2016; 335:54-63. [PMID: 27555550 DOI: 10.1016/j.neuroscience.2016.08.029] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Revised: 08/13/2016] [Accepted: 08/16/2016] [Indexed: 10/21/2022]
Abstract
Accumulating evidence indicates that odontoblasts act as sensor cells, capable of triggering action potentials in adjacent pulpal nociceptive axons, suggesting a paracrine signaling via a currently unknown mediator. Since glutamate can mediate signaling by non-neuronal cells, and peripheral axons may express glutamate receptors (GluR), we hypothesized that the expression of high levels of glutamate, and of sensory receptors in odontoblasts, combined with an expression of GluR in adjacent pulpal axons, is the morphological basis for odontoblastic sensory signaling. To test this hypothesis, we investigated the expression of glutamate, the thermo- and mechanosensitive ion channels transient receptor potential vanilloid 1 (TRPV1), transient receptor potential ankyrin 1 (TRPA1), and TWIK-1-related K+channel (TREK-1), and the glutamate receptor mGluR5, in a normal rat dental pulp, and following dentin injury. We also examined the glutamate release from odontoblast in cell culture. Odontoblasts were enriched with glutamate, at the level as high as in adjacent pulpal axons, and showed immunoreactivity for TRPV1, TRPA1, and TREK-1. Pulpal sensory axons adjacent to odontoblasts expressed mGluR5. Both the levels of glutamate in odontoblasts, and the expression of mGluR5 in nearby axons, were upregulated following dentin injury. The extracellular glutamate concentration was increased significantly after treating of odontoblast cell line with calcium permeable ionophore, suggesting glutamate release from odontoblasts. These findings lend morphological support to the hypothesis that odontoblasts contain glutamate as a potential neuroactive substance that may activate adjacent pulpal axons, and thus contribute to dental pain and hypersensitivity.
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Affiliation(s)
- Yi Sul Cho
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu 700-412, Republic of Korea
| | - Chang Hyun Ryu
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu 700-412, Republic of Korea
| | - Jong Hwa Won
- Pain Cognitive Function Research Center, Dental Research Institute of Neurobiology and Physiology, School of Dentistry, Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul, Republic of Korea
| | - Hue Vang
- Pain Cognitive Function Research Center, Dental Research Institute of Neurobiology and Physiology, School of Dentistry, Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul, Republic of Korea
| | - Seog Bae Oh
- Pain Cognitive Function Research Center, Dental Research Institute of Neurobiology and Physiology, School of Dentistry, Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul, Republic of Korea
| | - Jin Young Ro
- Department of Neural and Pain Sciences, University of Maryland School of Dentistry, Baltimore, USA
| | - Yong Chul Bae
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu 700-412, Republic of Korea.
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12
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Central connectivity of the chorda tympani afferent terminals in the rat rostral nucleus of the solitary tract. Brain Struct Funct 2014; 221:1125-37. [PMID: 25503820 DOI: 10.1007/s00429-014-0959-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Accepted: 12/06/2014] [Indexed: 10/24/2022]
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13
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Yoon BE, Woo J, Chun YE, Chun H, Jo S, Bae JY, An H, Min JO, Oh SJ, Han KS, Kim HY, Kim T, Kim YS, Bae YC, Lee CJ. Glial GABA, synthesized by monoamine oxidase B, mediates tonic inhibition. J Physiol 2014; 592:4951-68. [PMID: 25239459 DOI: 10.1113/jphysiol.2014.278754] [Citation(s) in RCA: 119] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
GABA is the major inhibitory transmitter in the brain and is released not only from a subset of neurons but also from glia. Although neuronal GABA is well known to be synthesized by glutamic acid decarboxylase (GAD), the source of glial GABA is unknown. After estimating the concentration of GABA in Bergmann glia to be around 5-10 mM by immunogold electron microscopy, we demonstrate that GABA production in glia requires MAOB, a key enzyme in the putrescine degradation pathway. In cultured cerebellar glia, both Ca(2+)-induced and tonic GABA release are significantly reduced by both gene silencing of MAOB and the MAOB inhibitor selegiline. In the cerebellum and striatum of adult mice, general gene silencing, knock out of MAOB or selegiline treatment resulted in elimination of tonic GABA currents recorded from granule neurons and medium spiny neurons. Glial-specific rescue of MAOB resulted in complete rescue of tonic GABA currents. Our results identify MAOB as a key synthesizing enzyme of glial GABA, which is released via bestrophin 1 (Best1) channel to mediate tonic inhibition in the brain.
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Affiliation(s)
- Bo-Eun Yoon
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Neuroscience Program, University of Science and Technology (UST), Daejeon, 305-350, Korea Department of Nanobiomedical Science, Dankook University, Chungnam, 330-714, Korea
| | - Junsung Woo
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Neuroscience Program, University of Science and Technology (UST), Daejeon, 305-350, Korea
| | - Ye-Eun Chun
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Neuroscience Program, University of Science and Technology (UST), Daejeon, 305-350, Korea
| | - Heejung Chun
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea
| | - Seonmi Jo
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 305-701, Korea
| | - Jin Young Bae
- Department of Oral Anatomy and Neurobiology, BK21, School of Dentistry, Kyungpook National University, Daegu, 700-412, Republic of Korea
| | - Heeyoung An
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea KU-KIST School of Converging Science and Technology, Korea University, Seoul, 136-701, Korea
| | - Joo Ok Min
- Department of Nanobiomedical Science, Dankook University, Chungnam, 330-714, Korea
| | - Soo-Jin Oh
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea
| | - Kyung-Seok Han
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Neuroscience Program, University of Science and Technology (UST), Daejeon, 305-350, Korea
| | - Hye Yun Kim
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea
| | - Taekeun Kim
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea
| | - Young Soo Kim
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea
| | - Yong Chul Bae
- Department of Oral Anatomy and Neurobiology, BK21, School of Dentistry, Kyungpook National University, Daegu, 700-412, Republic of Korea
| | - C Justin Lee
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Neuroscience Program, University of Science and Technology (UST), Daejeon, 305-350, Korea
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14
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Hudson N, Powner MB, Sarker MH, Burgoyne T, Campbell M, Ockrim ZK, Martinelli R, Futter CE, Grant MB, Fraser PA, Shima DT, Greenwood J, Turowski P. Differential apicobasal VEGF signaling at vascular blood-neural barriers. Dev Cell 2014; 30:541-52. [PMID: 25175707 PMCID: PMC4160345 DOI: 10.1016/j.devcel.2014.06.027] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 06/05/2014] [Accepted: 06/30/2014] [Indexed: 12/31/2022]
Abstract
The vascular endothelium operates in a highly polarized environment, but to date there has been little exploration of apicobasal polarization of its signaling. We show that VEGF-A, histamine, IGFBP3, and LPA trigger unequal endothelial responses when acting from the circulation or the parenchymal side at blood-neural barriers. For VEGF-A, highly polarized receptor distribution contributed to distinct signaling patterns: VEGFR2, which was found to be predominantly abluminal, mediated increased permeability via p38; in contrast, luminal VEGFR1 led to Akt activation and facilitated cytoprotection. Importantly, such differential apicobasal signaling and VEGFR distribution were found in the microvasculature of brain and retina but not lung, indicating that endothelial cells at blood-neural barriers possess specialized signaling compartments that assign different functions depending on whether an agonist is tissue or blood borne. At blood-neural barriers, only abluminal (tissue-side) VEGF-A induces permeability Most VEGFR1 is localized on the luminal face of neural microvascular endothelium Most VEGFR2 is localized on the abluminal face of neural microvascular endothelium Luminal VEGFR1 stimulates Akt; abluminal VEGFR2 induces permeability via p38
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Affiliation(s)
- Natalie Hudson
- Department of Cell Biology, UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK
| | - Michael B Powner
- Department of Cell Biology, UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK
| | - Mosharraf H Sarker
- Department of Cell Biology, UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK; Cardiovascular Division, King's College London, 150 Stamford Street, London SE1 9NH, UK
| | - Thomas Burgoyne
- Department of Cell Biology, UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK
| | - Matthew Campbell
- Neurovascular Genetics Laboratory, Smurfit Institute of Genetics, Lincoln Place Gate, Trinity College, Dublin 2, Ireland
| | - Zoe K Ockrim
- Department of Cell Biology, UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK
| | - Roberta Martinelli
- Department of Cell Biology, UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK
| | - Clare E Futter
- Department of Cell Biology, UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK
| | - Maria B Grant
- Eugene and Marilyn Glick Eye Institute, Department of Ophthalmology, Indiana University School of Medicine, 1160 West Michigan Street, Indianapolis, IN 46202, USA
| | - Paul A Fraser
- Cardiovascular Division, King's College London, 150 Stamford Street, London SE1 9NH, UK
| | - David T Shima
- Department of Ocular Biology and Therapeutics, UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK
| | - John Greenwood
- Department of Cell Biology, UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK
| | - Patric Turowski
- Department of Cell Biology, UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK.
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15
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In vivo Proton NMR spectroscopy of genetic mouse models BALB/cJ and C57BL/6By: variation in hippocampal glutamate level and the metabotropic glutamate receptor, subtype 7 (Grm7) gene. J Mol Neurosci 2014; 53:135-41. [PMID: 24390354 DOI: 10.1007/s12031-013-0211-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Accepted: 12/12/2013] [Indexed: 12/19/2022]
Abstract
Glutamatergic neurotransmission in the brain is modulated by metabotropic glutamate receptors (mGluR). In recent studies, we identified a cis-regulated variant of a gene (Grm7) which codes for mGluR subtype 7 (mGluR7), a presynaptic inhibitory receptor. The genetic variant derived from the BALB/cJ mouse strain (Grm7 (BALB/cJ)) codes for higher abundance of mGluR7 mRNA in the hippocampus than the C57BL/6By strain-derived variant (Grm7 (C57BL/6By)). Here, we used localized in vivo (1)H NMR spectroscopy to test the hypothesis that Grm7 (BALB/cJ) is also associated with lower glutamate concentration in the same brain region. All data were obtained on a 7.0 T Agilent (Santa Clara, CA, USA) 40-cm bore system using experimentally naive adult male inbred C57BL/6By, BALB/cJ, and congenic mice (B6By.C.6.132.54) constructed in our laboratory carrying Grm7 (BALB/cJ) on C57BL/6By genetic background. The voxel of interest size was 6 μL (1 × 2 × 3 mm(3)) placed in the hippocampal CA1 region. The results showed that the hippocampal level of glutamate in the congenic mouse strain was significantly lower than that in the background C57BL/6By strain which carried the Grm7 (C57BL/6By) allele. Because the two inbred strains are genetically highly similar except at the region of the Grm7 gene, the results raise the possibility that allelic variation at the Grm7 locus contributes to the strain differences in both hippocampal mRNA abundance and glutamate level which may modulate complex behavioral traits, such as learning and memory, addiction, epilepsy, and mood disorders.
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16
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Inducible presynaptic glutamine transport supports glutamatergic transmission at the calyx of Held synapse. J Neurosci 2013; 33:17429-34. [PMID: 24174676 DOI: 10.1523/jneurosci.1466-13.2013] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The mechanisms by which the excitatory neurotransmitter glutamate is recycled at synapses are currently unknown. By examining the functional expression of plasma membrane transporters at presynaptic terminals, we aim to elucidate some of the mechanisms of glutamate recycling. Using whole-cell voltage-clamp recordings from rat calyx of Held presynaptic terminals, our data show, for the first time, that the glutamate precursor glutamine causes the direct activation of an electrogenic, sodium-dependent presynaptic transporter, which supplies glutamine for generation of presynaptic glutamate and helps sustain synaptic transmission. Interestingly, the functional expression of this transporter at the presynaptic plasma membrane is dynamically controlled by electrical activity of the terminal, indicating that uptake of neurotransmitter precursors is controlled by the demand at an individual terminal. Induction of the transporter current is calcium-dependent and inhibited by botulinum neurotoxin C, demonstrating the involvement of SNARE-dependent exocytosis in inserting transporters into the plasma membrane when the terminal is active. Conversely, inactivity of the presynaptic terminal results in removal of transporters via clathrin-mediated endocytosis. To investigate whether the presynaptic glutamine transporter supplies the precursor for generating the synaptically released glutamate, we measured miniature EPSCs to assess vesicular glutamate content. When the presynaptic glutamate pool was turned over by synaptic activity, inhibiting the presynaptic glutamine transporters with MeAIB reduced the miniature EPSC amplitude significantly. This demonstrates that presynaptic glutamine transport is centrally involved in the production of glutamate and assists in maintaining excitatory neurotransmission.
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17
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Low dopamine D5 receptor density in hippocampus in an animal model of attention-deficit/hyperactivity disorder (ADHD). Neuroscience 2013; 242:11-20. [DOI: 10.1016/j.neuroscience.2013.03.036] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2012] [Revised: 03/18/2013] [Accepted: 03/19/2013] [Indexed: 11/23/2022]
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18
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Paik SK, Kwak MK, Bae JY, Yi HW, Yoshida A, Ahn DK, Bae YC. γ-Aminobutyric acid-, glycine-, and glutamate-immunopositive boutons on mesencephalic trigeminal neurons that innervate jaw-closing muscle spindles in the rat: Ultrastructure and development. J Comp Neurol 2012; 520:3414-27. [DOI: 10.1002/cne.23110] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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19
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Zeilhofer HU, Wildner H, Yévenes GE. Fast synaptic inhibition in spinal sensory processing and pain control. Physiol Rev 2012; 92:193-235. [PMID: 22298656 DOI: 10.1152/physrev.00043.2010] [Citation(s) in RCA: 262] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The two amino acids GABA and glycine mediate fast inhibitory neurotransmission in different CNS areas and serve pivotal roles in the spinal sensory processing. Under healthy conditions, they limit the excitability of spinal terminals of primary sensory nerve fibers and of intrinsic dorsal horn neurons through pre- and postsynaptic mechanisms, and thereby facilitate the spatial and temporal discrimination of sensory stimuli. Removal of fast inhibition not only reduces the fidelity of normal sensory processing but also provokes symptoms very much reminiscent of pathological and chronic pain syndromes. This review summarizes our knowledge of the molecular bases of spinal inhibitory neurotransmission and its organization in dorsal horn sensory circuits. Particular emphasis is placed on the role and mechanisms of spinal inhibitory malfunction in inflammatory and neuropathic chronic pain syndromes.
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20
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Dopamine D5 receptors are localized at asymmetric synapses in the rat hippocampus. Neuroscience 2011; 192:164-71. [DOI: 10.1016/j.neuroscience.2011.06.056] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Revised: 05/27/2011] [Accepted: 06/18/2011] [Indexed: 01/22/2023]
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21
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Omote H, Miyaji T, Juge N, Moriyama Y. Vesicular Neurotransmitter Transporter: Bioenergetics and Regulation of Glutamate Transport. Biochemistry 2011; 50:5558-65. [DOI: 10.1021/bi200567k] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Hiroshi Omote
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan
| | - Takaaki Miyaji
- Advanced Science Research Center, Okayama University, Okayama 700-8530, Japan
| | - Narinobu Juge
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan
| | - Yoshinori Moriyama
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan
- Advanced Science Research Center, Okayama University, Okayama 700-8530, Japan
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22
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A TACC3/ch-TOG/clathrin complex stabilises kinetochore fibres by inter-microtubule bridging. EMBO J 2011; 30:906-19. [PMID: 21297582 DOI: 10.1038/emboj.2011.15] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Accepted: 01/07/2011] [Indexed: 12/24/2022] Open
Abstract
Kinetochore fibres (K-fibres) of the spindle apparatus move chromosomes during mitosis. These fibres are discrete bundles of parallel microtubules (MTs) that are crosslinked by inter-MT 'bridges' that are thought to improve fibre stability during chromosomal movement. The identity of these bridges is unknown. Clathrin is a multimeric protein that has been shown to stabilise K-fibres during early mitosis by a mechanism independent of its role in membrane trafficking. In this study, we show that clathrin at the mitotic spindle is in a transforming acidic colied-coil protein 3 (TACC3)/colonic, hepatic tumour overexpressed gene (ch-TOG)/clathrin complex. The complex is anchored to the spindle by TACC3 and ch-TOG. Ultrastructural analysis of clathrin-depleted K-fibres revealed a selective loss of a population of short inter-MT bridges and a general loss of MTs. A similar loss of short inter-MT bridges was observed in TACC3-depleted K-fibres. Finally, immunogold labelling confirmed that inter-MT bridges in K-fibres contain clathrin. Our results suggest that the TACC3/ch-TOG/clathrin complex is an inter-MT bridge that stabilises K-fibres by physical crosslinking and by reducing rates of MT catastrophe.
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23
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Obesity and type 2 diabetes in rats are associated with altered brain glycogen and amino-acid homeostasis. J Cereb Blood Flow Metab 2010; 30:1527-37. [PMID: 20424632 PMCID: PMC2949239 DOI: 10.1038/jcbfm.2010.61] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Obesity and type 2 diabetes have reached epidemic proportions; however, scarce information about how these metabolic syndromes influence brain energy and neurotransmitter homeostasis exist. The objective of this study was to elucidate how brain glycogen and neurotransmitter homeostasis are affected by these conditions. [1-(13)C]glucose was administered to Zucker obese (ZO) and Zucker diabetic fatty (ZDF) rats. Sprague-Dawley (SprD), Zucker lean (ZL), and ZDF lean rats were used as controls. Several brain regions were analyzed for glycogen levels along with (13)C-labeling and content of glutamate, glutamine, GABA, aspartate, and alanine. Blood glucose concentrations and (13)C enrichment were determined. (13)C-labeling in glutamate was lower in ZO and ZDF rats in comparison with the controls. The molecular carbon labeling (MCL) ratio between alanine and glutamate was higher in the ZDF rats. The MCL ratios of glutamine and glutamate were decreased in the cerebellum of the ZO and the ZDF rats. Glycogen levels were also lower in this region. These results suggest that the obese and type 2 diabetic models were associated with lower brain glucose metabolism. Glucose metabolism through the TCA cycle was more decreased than glycolytic activity. Furthermore, reduced glutamate-glutamine cycling was also observed in the obese and type 2 diabetic states.
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Abstract
The structure of neurons changes during development and in response to injury or alteration in sensory experience. Changes occur in the number, shape, and dimensions of dendritic spines together with their synapses. However, precise data on these changes in response to learning are sparse. Here, we show using quantitative transmission electron microscopy that a simple form of learning involving mystacial vibrissae results in approximately 70% increase in the density of inhibitory synapses on spines of neurons located in layer IV barrels that represent the stimulated vibrissae. The spines contain one asymmetrical (excitatory) and one symmetrical (inhibitory) synapse (double-synapse spines), and their density increases threefold as a result of learning with no apparent change in the density of asymmetrical synapses. This effect seems to be specific for learning because pseudoconditioning (in which the conditioned and unconditioned stimuli are delivered at random) does not lead to the enhancement of symmetrical synapses but instead results in an upregulation of asymmetrical synapses on spines. Symmetrical synapses of cells located in barrels receiving the conditioned stimulus also show a greater concentration of GABA in their presynaptic terminals. These results indicate that the immediate effect of classical conditioning in the "conditioned" barrels is rapid, pronounced, and inhibitory.
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25
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Featherstone DE. Intercellular glutamate signaling in the nervous system and beyond. ACS Chem Neurosci 2010; 1:4-12. [PMID: 22778802 DOI: 10.1021/cn900006n] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2009] [Revised: 09/25/2009] [Indexed: 01/22/2023] Open
Abstract
Most intercellular glutamate signaling in the nervous system occurs at synapses. Some intercellular glutamate signaling occurs outside synapses, however, and even outside the nervous system where high ambient extracellular glutamate might be expected to preclude the effectiveness of glutamate as an intercellular signal. Here, I briefly review the types of intercellular glutamate signaling in the nervous system and beyond, with emphasis on the diversity of signaling mechanisms and fundamental unanswered questions.
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Affiliation(s)
- David E. Featherstone
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois 60607
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26
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A semi-correlative technique for the subcellular localization of proteins in Drosophila synapses. J Neurosci Methods 2010; 185:273-9. [DOI: 10.1016/j.jneumeth.2009.10.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2009] [Revised: 09/29/2009] [Accepted: 10/11/2009] [Indexed: 11/21/2022]
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27
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Horn AK, Büttner-ennever JA, Büttner U. Saccadic premotor neurons in the brainstem: functional neuroanatomy and clinical implications. Neuroophthalmology 2009. [DOI: 10.3109/01658109609044631] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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28
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Ye ZC, Oberheim N, Kettenmann H, Ransom BR. Pharmacological "cross-inhibition" of connexin hemichannels and swelling activated anion channels. Glia 2009; 57:258-69. [PMID: 18837047 DOI: 10.1002/glia.20754] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The study of ion channels has relied heavily on the use of pharmacological blocking agents. However, many of these agents have multiple effects, which may compromise interpretation of results when the affected mechanisms/pathways mediate similar functions. Volume regulated anion channels (VRAC) and connexin hemichannels can both mediate the release of glutamate and taurine, although these channels have distinct activation stimuli and hemichannels, but not VRAC, are permeable to Lucifer Yellow (LY). It has been reported that some anion channel blockers may inhibit connexin hemichannels. We further examined the effects of classic gap junction/hemichannel blockers and anion channel blockers on these channels. The typical VRAC blockers, NPPB, IAA-94, and tamoxifen blocked low divalent cation-induced glutamate and taurine release and LY loading, presumed due to hemichannel opening. The blocking action of these compounds on hemichannels was concentration dependent and fell within the same range where the drugs classically block VRACs. Conversely, carbenoxolone (CBX), the most widely used gap junction/hemichannel blocker, was an effective blocker of VRAC-mediated glutamate and taurine release, and blocked these channels at similar concentrations at which it blocked hemichannels. The CBX effect on VRACs was verified using astrocytes from connexin 43 knock out (Cx43 KO) animals. In these cells, the hypotonic induced amino acid flux was retained whereas the low divalent cation solution-induced flux was lost. These results extend our knowledge about "cross-inhibition" of VRACs and gap junctions/hemichannels by certain pharmacological agents. Given the overlap in function of these two types of channels, great care must be exerted in using pharmacological blockers to identify one channel from the other.
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Affiliation(s)
- Zu-Cheng Ye
- Department of Neurology, University of Washington School of Medicine, Seattle, Washington 98104, USA.
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29
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Synaptic circuitry in the retinorecipient layers of the optic tectum of the lamprey (Lampetra fluviatilis). A combined hodological, GABA and glutamate immunocytochemical study. Brain Struct Funct 2009; 213:395-422. [PMID: 19252925 DOI: 10.1007/s00429-009-0205-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2008] [Accepted: 02/02/2009] [Indexed: 10/21/2022]
Abstract
The ultrastructure of the retinorecipient layers of the lamprey optic tectum was analysed using tract tracing techniques combined with GABA and glutamate immunocytochemistry. Two types of neurons were identified; a population of large GABA-immunonegative cells, and a population of smaller, highly GABA-immunoreactive interneurons, some of whose dendrites contain synaptic vesicles (DCSV). Five types of axon terminals were identified and divided into two major categories. The first of these are GABA-immunonegative, highly glutamate-immunoreactive, contain round synaptic vesicles, make asymmetrical synaptic contacts, and can in turn be divided into AT1 and AT2 terminals. The AT1 terminals are those of the retinotectal projection. The origin of the nonretinal AT2 terminals could not be determined. AT1 and AT2 terminals establish synaptic contacts with DCSV, with dendrites of the retinopetal neurons (DRN), and with conventional dendritic (D) profiles. The terminals of the second category are GABA-immunoreactive and can similarly be divided into AT3 and AT4 terminals. The AT3 terminals contain pleiomorphic synaptic vesicles and make symmetrical synaptic contacts for the most part with glutamate-immunoreactive D profiles. The AT4 terminals contain rounded synaptic vesicles and make asymmetrical synaptic contacts with DRN, with DCSV, and with D profiles. A fifth, rarely observed category of terminals (AT5) contain both clear synaptic vesicles and a large number of dense-core vesicles. Synaptic triads involving AT1, AT2 or AT4 terminals are rare. Our findings are compared to these of previous studies of the fine structure and immunochemical properties of the retinorecipient layers of the optic tectum or superior colliculus of Gnathostomes.
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Danilov AI, Gomes-Leal W, Ahlenius H, Kokaia Z, Carlemalm E, Lindvall O. Ultrastructural and antigenic properties of neural stem cells and their progeny in adult rat subventricular zone. Glia 2009; 57:136-52. [PMID: 18709646 DOI: 10.1002/glia.20741] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Neural stem cells (NSCs) in the subventricular zone (SVZ) continuously generate olfactory bulb interneurons in the adult rodent brain. Based on their ultrastructural and antigenic properties, NSCs, transient amplifying precursor cells, and neuroblasts (B, C, and A cells, respectively) have been distinguished in mouse SVZ. Here, we aimed to identify these cell types in rat SVZ ultrastructurally and at the light microscopy level, and to determine the antigenic properties of each cell type using gold and fluorescence immunolabeling. We found astrocytes with single cilia (NSCs, correspond to B cells) and neuroblasts (A cells). We also observed mitotic cells, ependymal cells, displaced ependymal cells, and mature astrocytes. In contrast, transient amplifying precursor cells (C cells) were not detected. The NSCs and neuroblasts had epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor alpha (PDGFRalpha) expressed on the ciliary apparatus and were the only cell types incorporating the proliferation marker BrdU. Throughout mitosis, EGFR and PDGFRalpha were associated with the microtubule of the mitotic spindle. Ependymal and displaced ependymal cells also expressed EGFR and PDGFRalpha on their cilia but did not incorporate BrdU. Our findings indicate that the NSCs in adult rat SVZ give rise directly to neuroblasts. During mitosis, the NSCs disassemble the primary cilium and symmetrically distribute EGFR and PDGFRalpha among their progeny.
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Affiliation(s)
- Alexandre I Danilov
- Laboratory of Neurogenesis and Cell Therapy, Section of Restorative Neurology, Wallenberg Neuroscience Center, Lund University Hospital, Lund, Sweden.
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31
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State of the art in antigen retrieval for immunohistochemistry. J Immunol Methods 2008; 341:1-18. [PMID: 19063895 DOI: 10.1016/j.jim.2008.11.007] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2008] [Revised: 11/19/2008] [Accepted: 11/19/2008] [Indexed: 12/14/2022]
Abstract
The masking effects of antigens by chemical fixation, processing, embedding media interactions, represent a serious problem for immunohistochemical purposes. Fortunately, different approaches in antigen retrieval exist. These techniques are relatively recent and continuously expanding. This review focuses on the present state of the art in antigen retrieval methods for immunohistochemistry in light and electron microscopy. Moreover, a brief discussion on the chemical aspects of fixation, mechanism of retrieval, as well as its efficacy, is given.
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Hammer J, Alvestad S, Osen KK, Skare Ø, Sonnewald U, Ottersen OP. Expression of glutamine synthetase and glutamate dehydrogenase in the latent phase and chronic phase in the kainate model of temporal lobe epilepsy. Glia 2008; 56:856-68. [PMID: 18381650 DOI: 10.1002/glia.20659] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
It has been suggested that astrocytic glutamate release or perturbed glutamate metabolism contributes to the proneness to epileptic seizures. Here we investigated whether astrocytic contents of the major glutamate degrading enzymes glutamine synthetase (GS) and glutamate dehydrogenase (GDH) decreases on moving from the latent phase (prior to seizures) to the chronic phase (after onset of seizures) in the kainate (KA) model of temporal lobe epilepsy. Western blotting and immunogold analysis of hippocampal formation indicated similar levels of GDH in the latent and chronic phases of KA injected rats and in corresponding controls. In contrast, the level of GS was increased in the latent phase compared with controls, as assessed by Western blots of whole hippocampal formation and subregions. The increase in GS paralleled that of glial fibrillary acidic protein (GFAP). Compared with the latent phase, the chronic phase revealed a lower level of GS (approaching control levels) but an unchanged GFAP content. The decrease in GS from latent to chronic phase was significant in whole hippocampal formation, dentate gyrus and CA3. It is concluded that kainate treated rats show an initial increase in GS, pari passu with the increase in GFAP, and a secondary decrease in GS that is not accompanied by a similar loss of GFAP. In a situation where glutamate catabolism is in high demand the secondary reduction in GS level may be sufficient to contribute to the seizure proneness that develops between the latent and chronic phases.
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Affiliation(s)
- Janniche Hammer
- Centre for Molecular Biology and Neuroscience, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
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Lentz MR, Westmoreland SV, Lee V, Ratai EM, Halpern EF, González RG. Metabolic markers of neuronal injury correlate with SIV CNS disease severity and inoculum in the macaque model of neuroAIDS. Magn Reson Med 2008; 59:475-84. [PMID: 18306400 DOI: 10.1002/mrm.21556] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
In vivo MR spectroscopy (MRS) studies have shown reductions in NAA/Cr levels in patients with severe neurocognitive deficits due to AIDS dementia complex (ADC), also known as neuroAIDS. The relationship between the cellular changes within the brain during neuroAIDS and the role of NAA/Cr as a metabolic marker remains unclear. In order to clarify the relationship between NAA/Cr and disease severity we utilized the simian immunodeficiency virus (SIV)/macaque model of encephalitis. High-field proton MRS was performed on extracted metabolites from frontal cortex tissue samples of 29 rhesus macaques (6 healthy, 23 moribund with AIDS). Neuropathologic determination of encephalitis severity for each animal was completed and was found to correlate with NAA/Cr levels. Decreases in Glu/Cr and GABA/Cr may indicate that both excitatory and inhibitory neurons are affected. Highly significant correlations between NAA/Cr, Glu/Cr, and GABA/Cr were observed. These neuronal metabolites were also decreased in the absence of classical SIV encephalitis (SIVE). At any disease classification, animals inoculated with SIVmac251 were found to have lower levels of NAA/Cr than animals inoculated with SIVmac239. In considering therapy for neuroAIDS the findings here support prevention of the encephalitic process, but suggest that suppressing the formation of multinucleated giant cells alone would be insufficient to prevent neuronal injury.
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Affiliation(s)
- Margaret R Lentz
- Massachusetts General Hospital, Department of Neuroradiology, Boston, Massachusetts 02114-2696, USA
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Immunogold quantification of amino acids and proteins in complex subcellular compartments. Nat Protoc 2008; 3:144-52. [PMID: 18193031 DOI: 10.1038/nprot.2007.525] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
An increasing number of imaging techniques are in use to study the localization of molecules involved in cell-to-cell signaling. Here we describe the use of immunogold procedures to detect and quantify molecules on electron micrographs. To measure the areas of the subcellular compartments under investigation, the protocol uses an overlay screen with an array of regularly spaced points. On the basis of this, the densities of the gold-labeled molecules can be calculated. Despite the limited lateral resolution of the immunogold method as used by many investigators ( approximately 30 nm), it is possible to measure the content of molecules associated with tiny tissue compartments, e.g., synaptic vesicles and different types of membrane, such as plasma membranes and vesicle membranes. The quantification protocol can be carried out without using computer programs. The entire protocol can be completed in approximately 15 d.
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Miceli D, Repérant J, Ward R, Rio JP, Jay B, Médina M, Kenigfest NB. Fine structure of the visual dorsolateral anterior thalamic nucleus of the pigeon (Columba livia): A hodological and GABA-immunocytochemical study. J Comp Neurol 2008; 507:1351-78. [DOI: 10.1002/cne.21635] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Holten AT, Gundersen V. Glutamine as a precursor for transmitter glutamate, aspartate and GABA in the cerebellum: a role for phosphate-activated glutaminase. J Neurochem 2007; 104:1032-42. [PMID: 17986214 DOI: 10.1111/j.1471-4159.2007.05065.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Phosphate-activated glutaminase is present at high levels in the cerebellar mossy fiber terminals. The role of this enzyme for the production of glutamate from glutamine in the parallel-fiber terminals is unclear. In order to address this, we used light miroscopic immunoperoxidase and electron microscopic immunogold methods to study the localization of glutamate in rat cerbellar slices incubated with physiological K+ (3 mmol/L) and depolarizing K+ (40 mmol/L) concentrations, and during depolarizing conditions with the addition of glutamine and the glutaminase inhibitor 6-diazo-5-oxo-l-norleucine. During K+-induced depolarization glutamate labeling was redistributed from parallel-fiber terminals to glial cells. The nerve terminal content of glutamate was sustained when the slices were supplied with glutamine, which also reduced the accumulation of glutamate in glia. In spite of glutamine supplementation, the depolarized slices treated with 6-diazo-5-oxo-l-norleucine showed depletion of glutamate from parallel-fiber terminals and accumulation in glial cells. We conclude that cerebellar parallel-fiber terminals contain a glutaminase activity enabling them to synthesize glutamate from glutamine. Our results confirm that this is also true for the mossy fiber terminals. In addition, we show that, like for glutamate, the levels of aspartate in parallel-fiber terminals and GABA in Golgi fiber terminals can be maintained during depolarization if glutamine is present. This process is dependent on the activity of a glutaminase, as it can be inhibited by 6-diazo-5-oxo-l-norleucine, suggesting that the glutaminase reaction is important for glutamine to act as a precursor also for aspartate and GABA. The low levels of the kidney type of glutaminase that previously has been shown to be present in the parallel and Golgi fiber terminals could be sufficient to produce the transmitter amino acids. Alternatively, the amino acids could be produced from the liver type of glutaminase, which is not yet localized on the cellular level, or from an unknown glutminase.
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Oltedal L, Haglerød C, Furmanek T, Davanger S. Vesicular release of glutamate from hippocampal neurons in culture: an immunocytochemical assay. Exp Brain Res 2007; 184:479-92. [PMID: 17851655 DOI: 10.1007/s00221-007-1118-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2006] [Accepted: 08/20/2007] [Indexed: 12/23/2022]
Abstract
Glutamate, the main excitatory neurotransmitter in the brain, may cause excitotoxic damage through excessive release during a number of pathological conditions. We have developed an immunocytochemical assay to investigate the mechanisms and regulation of glutamate release from intact, cultured neurons. Our results indicate that cultured hippocampal neurons have a large surplus of glutamate available for release upon chemically induced depolarization. Long incubations with high K(+)-concentrations, and induction of repetitive action potentials with the K(+)-channel blocker 4-aminopyridine (4-AP), caused a significant reduction in glutamate labeling in a subset of boutons, demonstrating that transmitter release exceeded the capacity for replenishment. The number of boutons where release exceeded replenishment increased continuously with time of stimulation. This depletion was Ca(2+)-dependent and sensitive to bafilomycin A1 (baf), indicating that it was dominated by vesicular release mechanisms. The depletion of glutamate from cell bodies and dendrites was also Ca(2+)-dependent. Thus, under the present conditions, cytosolic glutamate is taken up in vesicles prior to release, and the main escape route for the amino acid is through vesicular exocytosis. Depolarization with lower concentrations of K(+) caused sustainable release of glutamate, i.e., without full depletion.
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Affiliation(s)
- Leif Oltedal
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009 Bergen, Norway.
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Grant L, Slapnick S, Kennedy H, Hackney C. Ryanodine receptor localisation in the mammalian cochlea: an ultrastructural study. Hear Res 2006; 219:101-9. [PMID: 16889917 DOI: 10.1016/j.heares.2006.06.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2005] [Revised: 06/05/2006] [Accepted: 06/12/2006] [Indexed: 10/24/2022]
Abstract
Calcium-induced calcium release (CICR) in the mammalian cochlea has been suggested to enhance neurotransmitter release from inner hair cells and facilitate the efferent response in outer hair cells. Light microscopic evidence exists for the presence of ryanodine receptors in the organ of Corti but there is so far no information about their ultrastructural localisation. We have therefore used post-embedding immunogold labeling with antibodies that predominantly recognise ryanodine receptor isoforms 1 (RyR1) and 2 (RyR2) to investigate their distribution in rat cochleae. In inner hair cells, the highest levels of labeling were observed over an area of rough endoplasmic reticulum that lies in the cytoplasmic region beneath the nucleus; in outer hair cells, the cytoplasmic region above the nucleus displayed most labeling. Labeling was also associated with the subsurface cisternae adjacent to the lateral membranes of both types of hair cell, with the efferent terminals on the outer hair cells and was observed in adjacent supporting cells. Labeling in outer hair cells was significantly higher than that in inner hair cells or in the supporting cells. Our results support the presence of RyR1 in the cochlea but do not rule out the presence of other isoforms. CICR may be involved in the control of calcium levels in the base of the inner hair cells and supporting cells, and in the cholinergic efferent response and motile behaviour of the outer hair cells.
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Affiliation(s)
- Lisa Grant
- Department of Physiology, University of Bristol, Bristol, UK.
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Holmseth S, Lehre KP, Danbolt NC. Specificity controls for immunocytochemistry. ACTA ACUST UNITED AC 2006; 211:257-66. [PMID: 16435108 DOI: 10.1007/s00429-005-0077-6] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/18/2005] [Indexed: 11/25/2022]
Abstract
Antibodies have been in widespread use for more than three decades as invaluable tools for the specific detection of proteins or other molecules in biological samples. In spite of such a long experience, the field of immunocytochemistry is still troubled by spurious results due to insufficient specificity of antibodies or procedures used. The importance of keeping a high standard is increasing because massive sequencing of entire genomes leads to the identification of numerous new proteins. All the identified proteins and their variants will have to be localized precisely and quantitatively at high resolution throughout the development of all species. Consequently, antibody generation and immunocytochemical investigations will be done on a large scale. It will be economically important to secure an optimal balance between the risk of publishing erroneous data (which are expensive to correct) and the costs of specificity testing. Because proofs of specificity are never absolute, but rather represent failures to detect crossreactivity, there is no limit to the number of control experiments that can be performed. The aims of the present paper are to increase the awareness of the difficulties in proving the specificity of immunocytochemical labeling and to initiate a discussion on optimized standards. The main points are: (1) antibodies should be described properly, (2) the labeling obtained with an antibody to a single epitope needs additional verification and (3) the investigators should be required to outline in detail how they arrive at the conclusion that the immunocytochemical labeling is specific.
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Affiliation(s)
- S Holmseth
- Centre of Molecular Biology and Neuroscience, Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, PO Box 1105, 0317, Oslo, Blindern, Norway
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Kang N, Xu J, Xu Q, Nedergaard M, Kang J. Astrocytic glutamate release-induced transient depolarization and epileptiform discharges in hippocampal CA1 pyramidal neurons. J Neurophysiol 2005; 94:4121-30. [PMID: 16162834 DOI: 10.1152/jn.00448.2005] [Citation(s) in RCA: 138] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A paroxysmal depolarization shift (PDS) has been suggested to be a hallmark for epileptic activity in partial-onset seizures. By monitoring membrane potentials and currents in pairs of pyramidal neurons and astrocytes with dual patch-clamp recording and exocytosis of vesicles from astrocytes with two-photon laser scanning microscopy in hippocampal slices, we found that infusion of inositol 1,4,5-trisphosphate (IP(3)) into astrocytes by patch pipettes induced astrocytic glutamate release that triggered a transient depolarization (TD) and epileptiform discharges in CA1 pyramidal neurons. The TD is due to a tetrodotoxin (TTX)-insensitive slowly decaying transient inward current (STC). Astrocytic glutamate release simultaneously triggers both the STC in pyramidal neurons and a transport current (TC) in astrocytes. The neuronal STC is mediated by ionotropic glutamate receptors leading to the TD and epileptiform discharges; while the astrocytic TC is a glutamate reuptake current resulting from transporting released glutamate into the patched astrocyte. Fusion of a large vesicle in astrocytes was immediately followed by an astrocytic TC, suggesting that the fused vesicle contains glutamate. Both fusion of large vesicles and astrocytic TCs were blocked by tetanus toxin (TeNT), suggesting that astrocytic glutamate release is via SNARE-dependent exocytosis of glutamate-containing vesicles. In the presence of TTX, the epileptogenic reagent, 4-AP, also induced similar neuronal STCs and astrocytic TCs, suggesting that astrocytic glutamate release may play an epileptogenic role in initiation of epileptic seizures under pathological conditions. Our study provides a novel mechanism, astrocytic release of glutamate, for seizure initiation.
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Affiliation(s)
- Ning Kang
- Department. of Cell Biology and Anatomy, New York Medical College, Valhalla, 10595, USA
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41
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Shigenaga Y, Moritani M, Oh SJ, Park KP, Paik SK, Bae JY, Kim HN, Ma SK, Park CW, Yoshida A, Ottersen OP, Bae YC. The distribution of inhibitory and excitatory synapses on single, reconstructed jaw-opening motoneurons in the cat. Neuroscience 2005; 133:507-18. [PMID: 15878646 DOI: 10.1016/j.neuroscience.2005.02.022] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2005] [Revised: 02/03/2005] [Accepted: 02/12/2005] [Indexed: 11/21/2022]
Abstract
In a previous study, we reported that the distribution of inhibitory input, in contrast to excitatory input, decreased somatofugally along dendrites of cat jaw-closing alpha-motoneurons [J Comp Neurol 414 (1999) 454]. The present study examined the distribution of GABA, glycine, and glutamate immunopositive boutons covering horseradish peroxidase-labeled cat jaw-opening motoneurons. The motoneurons were divided into four compartments: the soma, and primary, intermediate, and distal dendrites. Ninety-seven percent of the total number of studied boutons had immunoreactivity for at least one of the three amino acids. The proportion of boutons immunoreactive for GABA and/or glycine was lower than the proportion of boutons immunoreactive for glutamate. Boutons immunoreactive to glycine alone were more numerous than boutons double-labeled for GABA and glycine, which, in turn, occurred more frequently than boutons immunoreactive to GABA alone. The percentage synaptic covering (proportion of membrane covered by synaptic boutons) of the putatively excitatory (glutamate containing) and putatively inhibitory (GABA and/or glycine containing) boutons decreased somatofugally along the dendrites. Such systematic variations were not seen in the packing density (number of boutons per 100 microm(2)); the packing density showed a distinct drop between the soma and primary dendrites but did not differ significantly among the three dendritic compartments. Overall, the packing density was slightly higher for the putatively excitatory boutons than for the inhibitory ones. When taken together with previous analyses of jaw-closing alpha-motoneurons the present data on jaw-opening alpha-motoneurons indicate that the two types of neuron differ in regard to the nature of synaptic integration in the dendritic tree.
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Affiliation(s)
- Y Shigenaga
- Department of Oral Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Jung-Gu, Daegu 700-412, Korea.
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Larsson M, Broman J. Different basal levels of CaMKII phosphorylated at Thr286/287 at nociceptive and low-threshold primary afferent synapses. Eur J Neurosci 2005; 21:2445-58. [PMID: 15932602 DOI: 10.1111/j.1460-9568.2005.04081.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Postsynaptic autophosphorylation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) at Thr286/287 is crucial for the induction of long-term potentiation at many glutamatergic synapses, and has also been implicated in the persistence of synaptic potentiation. However, the availability of CaMKII phosphorylated at Thr286/287 at individual glutamatergic synapses in vivo is unclear. We used post-embedding immunogold labelling to quantitatively analyse the ultrastructural localization of CaMKII phosphorylated at Thr286/287 (pCaMKII) at synapses formed by presumed nociceptive and low-threshold mechanosensitive primary afferent nerve endings in laminae I-IV of rat spinal cord. Immunogold labelling was enriched in the postsynaptic densities of such synapses, consistent with observations in pre-embedding immunoperoxidase-stained dorsal horn. Presynaptic axoplasm also exhibited sparse immunogold labelling, in peptidergic terminals partly associated with dense core vesicles. Analysis of single or serial pCaMKII-immunolabelled sections indicated that the large majority of synapses formed either by presumed peptidergic or non-peptidergic nociceptive primary afferent terminals in laminae I-II of the spinal cord, or by presumed low-threshold mechanosensitive primary afferent terminals in laminae IIi-IV, contained pCaMKII in their postsynaptic density. However, the postsynaptic levels of pCaMKII immunolabelling at low-threshold primary afferent synapses were only approximately 50% of those at nociceptive synapses. These results suggest that constitutively autophosphorylated CaMKII in the postsynaptic density is a common characteristic of glutamatergic synapses, thus potentially contributing to maintenance of synaptic efficacy. Furthermore, pCaMKII appears to be differentially regulated between high- and low-threshold primary afferent synapses, possibly reflecting different susceptibility to synaptic plasticity between these afferent pathways.
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Affiliation(s)
- Max Larsson
- Department of Experimental Medical Science, Division of Neuroscience, Lund University, BMC F10, SE-221 84 Lund, Sweden.
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Halasy K, Hajszan T, Kovács EG, Lam TT, Leranth C. Distribution and origin of vesicular glutamate transporter 2-immunoreactive fibers in the rat hippocampus. Hippocampus 2005; 14:908-18. [PMID: 15382259 DOI: 10.1002/hipo.20006] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
This study examined the distribution of vesicular glutamate transporter 2 (VGLUT2)-immunoreactive neuronal structures in the ipsilateral and contralateral hippocampi of unilateral fimbria/fornix transected, unilateral entorhinal cortex ablated, and intact female and male rats. In the hippocampi of intact animals, the highest density of VGLUT2-positive boutons was observed in the supragranular layer of the dentate gyrus, followed by the CA2 pyramidal and oriens layers, and the stratum lacunosum-moleculare of the CA1 field. This staining pattern was identical both in males and in females. Electron microscopic examination revealed that the immunolabeling was confined to axon terminals forming exclusively asymmetric synaptic contacts. The quantitative analysis of the synaptic targets of VGLUT2-positive terminals showed that in the dentate gyrus, 59% of the synaptic targets were dendritic spines, followed by dendritic shafts (22%) and granule cell somata (19%). In the pyramidal layer of the CA2 field, VGLUT2-immunoreactive boutons contacted mostly dendritic shafts (85%), only some of which (15%) synapsed with spines. The synaptic targets of VGLUT2-positive varicosities were dendritic spines (71%) and shafts (29%) in the stratum lacunosum-moleculare of the CA1 field. The fimbria/fornix transection caused a significant reduction in the density of VGLUT2-positive boutons only in the CA2 field, while entorhinal cortex ablation elicited no change in fiber density in any of the areas analyzed. Furthermore, our latest experiments on colchicine-treated animals revealed a large population of VGLUT2-positive neurons in the hippocampus that may be a possible intrinsic source of hippocampal VGLUT2 boutons. Our results suggest that the most likely sources of VGLUT2-positive boutons in the dentate supragranular layer, the CA2 area, as well as in the stratum lacunosum-moleculare of the CA1 field, might be the mossy cells, the supramammillary area, and the nucleus reuniens thalami, respectively.
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Affiliation(s)
- Katalin Halasy
- Department of Obstetrics and Gynecology, Yale University School of Medicine, New Haven, Connecticut 06520-8063, USA
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Waagepetersen HS, Hansen GH, Fenger K, Lindsay JG, Gibson G, Schousboe A. Cellular mitochondrial heterogeneity in cultured astrocytes as demonstrated by immunogold labeling of α-ketoglutarate dehydrogenase. Glia 2005; 53:225-31. [PMID: 16206171 DOI: 10.1002/glia.20276] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
In brain cells, various metabolites and metabolic pathways, largely of mitochondrial origin, have been shown to be compartmentalized. Attention has therefore been focused on the possible existence of mitochondrial heterogeneity in the brain at the cellular level. To determine whether mitochondria in cultured cortical and cerebellar astrocytes are heterogeneous at the single cell level, immunogold electron microscopy and an antibody against the alpha-ketoglutarate dehydrogenase component of the alpha-ketoglutarate dehydrogenase complex, a marker enzyme for the tricarboxylic acid (TCA) cycle, were employed. The number of gold particles was counted in the mitochondria of 36 and 42 cells from cultured cerebellar and cortical astrocytes, respectively. A test for random distribution (Poisson distribution) of mitochondria according to the number of gold particles was subsequently performed for every one of the 36 and 42 cells as the ratio variance/mean (= index of dispersion). This should be approximately distributed as chi2/degrees of freedom (df) = n - 1, n = number of mitochondria), if the observations obeyed a Poisson distribution. For 26 of the 36 (cerebellar astrocytes) distributions and for 28 of the 42 (cortical astrocytes) distributions a random distribution had to be rejected. These findings therefore strongly indicate that alpha-ketoglutarate dehydrogenase is heterogeneously distributed in mitochondria within individual astrocytes originating either from cerebellum or cerebral cortex. In conclusion, this study underlines the probability that mitochondrial heterogeneity at the single cell level might be extended to involve other metabolic pathways and metabolites.
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Affiliation(s)
- Helle S Waagepetersen
- Department of Pharmacology, Danish University of Pharmaceutical Sciences, Copenhagen, Denmark
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Mahendrasingam S, Wallam CA, Polwart A, Hackney CM. An immunogold investigation of the distribution of GABA and glycine in nerve terminals on the somata of spherical bushy cells in the anteroventral cochlear nucleus of guinea pig. Eur J Neurosci 2004; 19:993-1004. [PMID: 15009147 DOI: 10.1111/j.1460-9568.2004.03193.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Spherical bushy neurons in the anteroventral cochlear nucleus receive glutamatergic primary terminals from the cochlear nerve and terminals of noncochlear (i.e. nonprimary) origin, many of which colocalize gamma-aminobutyric acid (GABA) and glycine. Here the relationship between GABA and glycine in these terminals has been investigated using postembedding immunogold labelling. A significant negative correlation was found between the density of terminal labelling for GABA and for glycine in four guinea pigs. Terminals could be divided into three categories, GABA-only, glycine-only, or colocalizing depending on whether they had a significantly higher labelling density for either amino acid than the primary terminals. The overall labelling density in all four animals was significantly greater for GABA in GABA-only terminals than colocalizing ones but similar for glycine in both. Within the terminals, the labelling density over synaptic vesicles, nonvesicular regions of cytoplasm and mitochondria was also investigated. No significant difference was detected in the labelling density of vesicles compared with nonvesicular regions for either amino acid. However, a significant difference was found between the overall labelling density over mitochondria and nonvesicular regions for both. There was also significantly more mitochondrial GABA labelling in GABA-only terminals compared to colocalizing terminals but mitochondrial glycine labelling was similar in glycine-only and colocalizing terminals. Thus the level of GABA is higher in single than in colocalizing terminals, particularly in the mitochondria, but similar for glycine in both. It is possible therefore that the presence of glycine affects the level of GABA in the nonprimary terminals but that the presence of GABA does not affect the level of glycine.
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Affiliation(s)
- S Mahendrasingam
- MacKay Institute of Communication and Neuroscience, School of Life Sciences, Keele University, Staffordshire ST5 5BG, UK
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Kiss J, Kocsis K, Csáki A, Halász B. Evidence for vesicular glutamate transporter synapses onto gonadotropin-releasing hormone and other neurons in the rat medial preoptic area. Eur J Neurosci 2003; 18:3267-78. [PMID: 14686900 DOI: 10.1111/j.1460-9568.2003.03085.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The medial preoptic area is a key structure in the control of reproduction. Several data suggest that excitatory amino acids are involved in the regulation of this function and the major site of this action is the medial preoptic region. Data concerning the neuromorphology of the glutamatergic innervation of the medial preoptic area are fragmentary. The present investigations were focused on: (i) the morphology of the vesicular glutamate transporter 1 (VGluT1)- and vesicular glutamate transporter 2 (VGluT2)-immunoreactive nerve terminals, which are considered to be specific to presumed glutamatergic neuronal elements, in the medial preoptic area of rat; and (ii) the relationship between these glutamate transporter-positive endings and the gonadotropin-releasing hormone (GnRH) neurons in the region. Single- and double-label immunocytochemistry was used at the light and electron microscopic level. There was a weak to moderate density of VGluT1- and a moderate to intense density of VGluT2-immunoreactive elements in the medial preoptic area. Electron microscopy revealed that both VGluT1- and VGluT2-immunoreactive boutons made asymmetric type synaptic contacts with unlabelled neurons. VGluT2-labelled, but not VGluT1-labelled, axon terminals established asymmetric synaptic contacts on GnRH-immunostained neurons, mainly on their dendrites. The present findings are the first electron microscopic examinations on the glutamatergic innervation of the rat medial preoptic area. They provide direct neuromorphological evidence for the existence of direct glutamatergic innervation of GnRH and other neurons in the rat medial preoptic area.
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Affiliation(s)
- J Kiss
- Neuroendocrine Research Laboratory, Hungarian Academy of Sciences and Semmelweis University, Department of Human Morphology and Developmental Biology, Semmelweis University, H-1094 Budapest, Tüzoltó u. 58., Hungary
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Sassoé-Pognetto M, Utvik JK, Camoletto P, Watanabe M, Stephenson FA, Bredt DS, Ottersen OP. Organization of postsynaptic density proteins and glutamate receptors in axodendritic and dendrodendritic synapses of the rat olfactory bulb. J Comp Neurol 2003; 463:237-48. [PMID: 12820158 DOI: 10.1002/cne.10745] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Glutamate neurotransmission in the olfactory bulb involves both axodendritic synapses and dendrodendritic reciprocal synapses and possibly also extrasynaptic receptors. By using a sensitive immunogold procedure, we have investigated the organization of two synaptic scaffolding molecules, PSD-95 and PSD-93, as well as N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methylisoxazole-4-proprionic acid (AMPA) receptors, at these heterogeneous glutamate signaling sites. Immunolabeling for PSD-95 and PSD-93 was present in all major types of putative glutamatergic synapse, suggesting that these proteins are essential components of the synaptic signaling apparatus. The linear density and the subsynaptic distribution of PSD-95/PSD-93 gold particles did not differ significantly between axodendritic and dendrodendritic synapses. Antibodies recognizing NMDA and AMPA receptor subunits also labeled asymmetric synapses throughout the olfactory bulb. Immunolabeling for the AMPA receptor subunits GluR2/3 was similar in all types of synapse. In contrast, immunogold signals for the NR1 subunit of NMDA receptors varied significantly among different synapse populations, with olfactory nerve synapses in the glomerular layer showing the lowest labeling intensity. Although the lateral dendrites of mitral and tufted cells have been reported to respond to glutamate, they did not display significant plasma membrane labeling for the NR1 subunit or for PSD-95, suggesting that the physiological effects of glutamate at these sites are mediated by NMDA autoreceptors that are not clustered and occur only at a low density on the dendritic surface. Our quantitative analysis of olfactory bulb synapses indicates that the density of NMDA receptors is not determined by the complement of PSD-95/PSD-93. The latter molecules appear to be expressed in an all-or-none fashion and may form a standard lattice common to different types of glutamatergic synapse.
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Affiliation(s)
- Marco Sassoé-Pognetto
- Department of Anatomy, Pharmacology, and Forensic Medicine, University of Turin, I-10126 Torino, Italy.
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Bergersen L, Ruiz A, Bjaalie JG, Kullmann DM, Gundersen V. GABA and GABAA receptors at hippocampal mossy fibre synapses. Eur J Neurosci 2003; 18:931-41. [PMID: 12925019 DOI: 10.1046/j.1460-9568.2003.02828.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Anatomical and electrophysiological evidence has raised the possibility that corelease of GABA and glutamate occurs at hippocampal mossy fibre synapses which, however, lack the vesicular GABA transporter VGAT. Here, we apply immunogold cytochemistry to show that GABA, like glutamate, has a close spatial relation to synaptic vesicles in rat mossy fibre terminals, implying that a mechanism exists to package GABA in synaptic vesicles. We also show that GABAA and AMPA receptors are colocalized at mossy fibre synapses. The expression of GABA and GABAA receptors is, however, weaker than in inhibitory synapses. Electrical stimuli that recruit mossy fibres evoke monosynaptic GABAA receptor-mediated signals in post-synaptic targets that show marked frequency-dependent facilitation and sensitivity to group II metabotropic receptors, two features that are characteristic of mossy fibre transmission. These results provide further evidence for GABA and glutamate cotransmission at mossy fibre synapses, although paired pre- and post-synaptic recordings will be required to determine the role of GABA at this unusual synapse.
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Affiliation(s)
- Linda Bergersen
- Anatomical Institute and the Centre for Molecular Biology and Neuroscience, University of Oslo, Blindern, Oslo, Norway
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Abstract
Little is known about the expression and possible functions of unopposed gap junction hemichannels in the brain. Emerging evidence suggests that gap junction hemichannels can act as stand-alone functional channels in astrocytes. With immunocytochemistry, dye uptake, and HPLC measurements, we show that astrocytes in vitro express functional hemichannels that can mediate robust efflux of glutamate and aspartate. Functional hemichannels were confirmed by passage of extracellular lucifer yellow (LY) into astrocytes in nominal divalent cation-free solution (DCFS) and the ability to block this passage with gap junction blocking agents. Glutamate/aspartate release (or LY loading) in DCFS was blocked by multivalent cations (Ca2+, Ba2+, Sr2+, Mg2+, and La3+) and by gap junction blocking agents (carbenoxolone, octanol, heptanol, flufenamic acid, and 18alpha-glycyrrhetinic acid) with affinities close to those reported for blockade of gap junction intercellular communication. Glutamate efflux via hemichannels was also accompanied by greatly reduced glutamate uptake. Glutamate release in DCFS, however, was not significantly mediated by reversal of the glutamate transporter: release did not saturate and was not blocked by glutamate transporter blockers. Control experiments in DCFS precluded glutamate release by volume-sensitive anion channels, P2X7 purinergic receptor pores, or general purinergic receptor activation. Blocking intracellular Ca2+ mobilization by BAPTA-AM or thapsigargin did not inhibit glutamate release in DCFS. Divalent cation removal also induced glutamate release from intact CNS white matter (acutely isolated optic nerve) that was blocked by carbenoxolone, suggesting the existence of functional hemichannels in situ. Our results indicated that astrocyte hemichannels could influence CNS levels of extracellular glutamate with implications for normal and pathological brain function.
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Mahendrasingam S, Wallam CA, Hackney CM. Two approaches to double post-embedding immunogold labeling of freeze-substituted tissue embedded in low temperature Lowicryl HM20 resin. BRAIN RESEARCH. BRAIN RESEARCH PROTOCOLS 2003; 11:134-41. [PMID: 12738009 DOI: 10.1016/s1385-299x(03)00040-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Double labeling is used for localizing two antigens simultaneously in the same tissue. We have used two approaches to post-embedding immunogold labeling to investigate whether nerve terminals in the guinea-pig anteroventral cochlear nucleus (AVCN) that contain gamma-aminobutyric acid (GABA) or glycine are capable of retrieving the other amino acid as part of an investigation of colocalization of these putative neurotransmitters. For this, vibroslices of perfusion-fixed brain stem were freeze-substituted and embedded in the low temperature resin, Lowicryl HM20. Simultaneous labeling of ultrathin sections was then performed with a mixture of a rabbit primary antibody to GABA and a guinea-pig primary antibody to the glycine transporter, GLYT2, followed by labeling with a mixture of secondary antibodies (goat anti-rabbit IgG-30 nm gold, goat anti-guinea pig IgG-15 nm gold). This approach indicated that GLYT2 occurs in the plasma membrane of some terminals that contain GABA. The other approach involved sequential labeling of ultrathin sections with a rabbit primary antibody to the GABA transporter, GAT1, followed by an anti-rabbit secondary antibody conjugated to 15-nm gold particles. Sections were then treated with paraformaldehyde vapor to denature any free anti-IgG binding sites on the first antibody, and labeled with a primary antibody to glycine also raised in rabbit followed by an anti-rabbit secondary antibody conjugated to 30-nm gold particles. This approach indicated that GAT1 occurs in the plasma membrane of some terminals that contain glycine. Thus, these techniques can be used to localize heat-labile multiple antigens in the same tissue.
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Affiliation(s)
- S Mahendrasingam
- MacKay Institute of Communication and Neuroscience, School of Life Sciences, Keele University, Keele, Staffordshire ST5 5BG, UK
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